West Coast Multi-Day heavy Precipitation Event 28 November-2 December 2012-Draft

Transcription

1 West Coast Multi-Day heavy Precipitation Event 28 November-2 December 2012-Draft By Richard H. Grumm and Charles Ross National Weather Service State College, PA Contributions by the Albany MAP and Craig Evanego Abstract A deep and persistent mid-tropospheric trough over the northeastern Pacific brought surges of high precipitable air into the West Coast of the United States. The surges of moisture over a 4- day period brought heavy rainfall to the mountains of northern and central California. Rainfall amounts in several orographically favored locations exceeded 500 mm (20 inches). The pattern was relatively well predicted by the NCEP global model and global ensemble forecast system. The relatively well predicted pattern and the strong terrain forcing produced relatively accurate quantitative precipitation forecasts. The global ensemble forecast system produced 48 hour rainfall amounts in excess of 150 mm and 72 hour forecasts produced some areas with in excess of 200 mm of precipitation. Shorter range forecasts from the NCEP short range ensemble forecast system produced comparable rainfall amounts. At 16km resolution, the short range ensemble forecasts showed the more terrain features which were vulnerable to heavy precipitation. Standardized anomalies were used to define the pattern and compare this event to previous events. The documented events 31 December 1996 into early January 1997 and an event in December 2010 were used to compare to this event. Each of these extreme rainfall events had significant precipitable water and moisture flux anomalies and each event had ensemble forecasts showing a high probability of 150 to 200 mm of QPF. The forecasts from the historic cases were retrieved from the global forecast system retroforecast project. These retro-forecasts provide an opportunity to evaluate ensemble prediction systems performance during previous high impact rainfall events and could be used to develop internal climatologies.

2 1. Overview An amplified ridge over the Aleutians and Bering Sea was part of a blocking pattern over the north Pacific. Short-waves from Asia cut under this high latitude blocking ridge resulting in a quasi-stationary 500 hpa trough over the northeastern Pacific and Gulf of Alaska. The resulting deep trough over the northeastern Pacific (Fig. 1a-f) pushed a series of waves, with surges of high precipitable water (PW) air (Fig. 2) into the West Coast of the United States resulting in a multi-day heavy rainfall event. The trough ridge-pattern and associated standardized anomalies over western North America and the eastern pacific was similar to the pattern for heavy rainfall found by Junker et al. (2008:Fig 4 &5). Negative height anomalies around -3s below normal are typically observed in the deep troughs off the West Coast with weaker positive height anomalies over western North America. The plume of deep moisture in the PW field (Fig. 2) or atmospheric river (AR:Neiman et al. 2008) and the anomaly field was similar to Junker et al. (2008: Figs 11&12). Clearly, this event had a well-known pattern often associated with extreme precipitation along the West Coast of North America. This event occurred in the climatological peak time for heavy precipitation events along the West Coast which peak during the cold season from November and March. The moisture flux along the West Coast peaks during this time (Junker et al. 2008) as does the occurrence of extremes in the moisture flux along the West Coast. The intrusions of deep moisture plumes or AR also peak during the cold season. Ralph and Dettinger (2012) examined heavy rainfall events along the West Coast during December The categorized rainfall events based on 3-day precipitation thresholds at National Weather Service COOP sites (see their Table 1). With several reports of in excess of 20 inches during the event of 28 November through 2 December 2012 this event may qualify as category 4 event with at least 2 stations reports in excess of 500 mm of rainfall. For reference, a category I event produces 200 to 300 mm of rainfall at approximately 173 stations. Their data results showed that California (See their Fig. 3) has the most high end rainfall events, likely due to the terrain and surges of high PW air in AR which impinge upon these terrain features. The value of patterns and anomalies in predicting heavy rainfall events has been demonstrated by Junker et. al (2009a;2009b;2008). The values of the model and ensemble data provide confidence in a pattern conducive in producing heavy rainfall. The model QPF and ensemble QPF probabilities aid in understanding the potential for heavy rainfall. The high probability of an extreme event combined with a pattern with the known to produce extreme rainfall events provides confidence in predicting these events. The concept of patterns and probabilities or Synoptic-Probabilistic forecasting requires knowledge of critical high impact weather patterns and probabilistic data from ensembles to anticipate extreme events. This paper will document the multi-day extreme rainfall event of 28 November through 2 December The pattern and critical anomalies are presented along with probabilistic QPFs standardized anomaly forecasts from the NCEP GEFS and SREF. These data demonstrate how predictable the event was. This event is then compared to the heavy rainfall events of December 2010 ( Ralph and Dettinger) and the event of December 1996-January 1997 (Junker et al. 2008).

3 2. Data and Methods The Climate Forecast System (CFS:Saha et al. 2010) version 2 data were used to reconstruct the pattern over this and historic events. The standardized anomalies were computed using the 21- day centered means and standard deviations computed from the CFSV1 (Saha 2010) data on a 1x1 degree grid. The method employed was similar to the method outlined by Hart and Grumm (2001). For the reconstruction of the conditions during the 21 July and 3-4 November 2012 events the SA were computed as: SA = (OBS MEAN)/STD (1) Where SA is the standardized anomaly in the observed fields, OBS is the parameter, for example PW, MEAN and STD are the 21-day centered mean and standard deviations from the CFSRV1 data. The NCEP Global Forecast system (GFS:) and Global ensemble forecast system (GEFS) and short-range ensemble forecast system where used to show forecasts the November-December 2012 event. For all forecast systems the SA were computed as in equation 1 except the observations (OBS) were replaced by the forecast value (FCST) when using the GFS or the ensemble mean when using the GEFS resulting in the following equation: SA = (FCST MEAN)/STD (2) All CFSR and forecast data were displayed using GrADS (Doty and Kinter 1995). The SA were displayed using shading and typically are displayed in 1σ ranges from -6 to +6σ. The observed, forecast, and ensemble mean fields are displayed as contours using standard meteorological contour intervals and units. Ensemble quantitative precipitation forecasts (QPF) were displayed in a two panels format. The upper panels show the probability of exceeding a specified threshold such as 50 mm and the ensemble mean 50mm QPF contour is plotted over the shaded probabilities. The lower panels show the ensemble mean QPF and individual members forecast of the specified contour used in the upper probability panels. The forecasts from the historic events were obtained from the reforecast data (Hamill et al 2012). The 11 member GEFS ensemble was used to produce probability forecasts of the QPF fields and reconstruct forecast of the standardized anomalies. The gridded Stage-IV precipitation data was used to show the spatial extent of the event. Data for point values were obtained from the National Weather Service River Forecast Center. These data aid in showing the local maximum not likely covered in gridded data. No attempted to categorize the event using COOP data was attempted. All gridded precipitation data were displayed using GrADS (Doty and Kinter 1995).

4 3. Regional Pattern and estimated precipitation The 24 hour gridded rainfall (Fig. 3) suggest that the heaviest rainfall was on the 30 th of November and 2 nd of December An examination of radar and 6-hourly estimated rainfall verified several impulse moving into the mountains producing the heavy rainfall (not shown). The hourly radar data showed some interesting mesoscale banded features between UTC 2 December which likely contributed to the heavy rainfall on 2 December. The unique bands on 2 December and the impulses produced in excess of 384mm of precipitation in the 4- day total QPE field (Fig. 4). The surges of high PW air impinged on California on the 29 th, 30 th (Fig. 5) of November and on the 1 st and 2 nd of November (not shown). These surges of high PW were accompanied by strong winds at 850 and 700 hpa resulting in several surges of high moisture flux values into the region (Figs. 6 &7). The 850 hpa moisture flux anomalies peaked over 5σ above normal at 30/0000, 30/0600, 30/1200 and 30/1800, 02/0600, 02/1200 UTC. The moisture flux was relatively low during 1 December peaking at near 3σ above normal at 01/1200 UTC with a weaker impulse which came ashore on 1 December. The pattern (Figs. 1 & 2) and the regional PW and moisture flux anomalies implied conditions typically associated with heavy and extreme rainfall events along the West Coast of the United States. The moisture flux anomalies were similar to the range of extreme rainfall events described by Junker et al. (2009).- 4. Forecasts The GEFS QPFs are shown using the GEFS probability of 125 mm for 125 mm or more QPF in 72 hours (Fig. 8) and the ensemble mean with spaghetti plots of the 125 mm contour in 72 hours (Fig 9) from the 1200 UTC GEFS. Values of 100 mm, 125, 150 and 200 mm were examined. The 200 mm contour (~8 inches) were observed in several GEFS forecast cycles (Fig. 10). The optimum time windows to display contours at and above 150mm varied implying issues with both temporal and spatial QPF forecasts. For brevity the focus is on the 125 mm forecasts which showed more consistent data at all forecast initial times. These high QPFs were only possible due to the relatively well predicted pattern which is not shown here+.

5 The six successive 0000 UTC GEFS runs beginning at 0000 UTC 25 November 2012 showing the probability of 125 mm of QPF valid from 1200 UTC 30 November through 1200 UTC 2 December 2012 are shown in Figure 8. These data show that all of the runs had the probability of 125mm or more QPF at the 40% level or greater. Due to timing and spatial issues the probabilities varied considerably from run-to-run and several runs failed to produce a mean 125 mm contour (Thick black contour). The 3 runs from 27,28, and 29 November had the highest probability of over 125 mm or more QPF and each produced a 125 mm contour (Fig. 8c-e). The mean QPF and each members 125mm contour from the successive 1200 UTC cycles (Fig. 9) beginning at 1200 UTC 24 November show that each run had several members producing at least 125mm or more of QPF. The runs initialized at 26,27,28, and 29 November each had a mean 125 mm contour. Several of these runs produced in excess of 150 mm (~6 inches) of QPF. The GEFS cycles which produced over 200 mm of QPF are shown in Figure 10. The time ranges was altered to capture more cycles. Several shorter range GEFS forecasts showed lower QPF amounts indicating a potential QPF spin-up issue. These data show that no single cycle produced a mean 200 mm contour and the probability of 200 mm or more QPF never exceeded 40%. It is unknown as to whether this is a limit of the system as the GEFS internal system QPF climatology is unknown. The potential exists that QPF amounts above 125 mm in 72 hour periods are extremely rare in the GEFS. The NCEP SREF forecasts from 30 November 2012 initialized at 0300, 0900 and 1500 UTC (Fig. 11) showed a similar pattern in the 150 mm and greater QPF. Due to the finer 16km resolution, the forecasts showed some of the potential terrain features not evident in the 55km GEFS. The forecasts for 125mm or more QPF during the forecast period (Fig. 12) clearly showed the impact of higher resolution and terrain on the forecast. 5. Historic and comparative events Junker et al. (2009) showed the rainfall and the pattern associated with the December January 1997 northern California heavy rainfall event. The reforecasts form the GEFS for this event were retrieved and analyzed. These data showed that the 11 member ensemble predicted both the pattern with surge of high PW air into California (Fig, 13) and the potential for heavy rainfall (Fig. 14&15). The ensemble mean PW and standardized anomalies for 6 forecast periods are shown. These data show the well predicted atmospheric river into the region with forecasts of PW anomalies in the +4 to +5σ range and a few isolated grid points in the +5 to +6σ range.

6 The reforecast GEFS at 75km resolution predicted over 150 mm of QPF (6 inches) of rainfall in 48 hours and had 72 hour forecasts in which over 200 mm (8 inches) of QPF was predicted (not shown). 6. Precipitation The total event precipitation estimated from the Stage-IV data was shown in Figure 4. The 4 key days during event were shown in Figure 3. Appendix 1-7 show daily precipitation maps produced by the California-Nevada River Forecast Center. These data indicated that the heaviest precipitation fell on the 30 th of November and the 2 nd of December. Gridded rainfall amounts in excess of 450 mm were difficult to find despite observations (Tables 1) of event total rainfall in excess of 20 inches. It was difficult to find good matching observations for the time periods in the gridded forecasts. Table 2 shows that 3 days totals over 16 inches was limited to 5 stations and only one station received over 20 inches of precipitation. Due to the relatively warm temperatures snowfall was limited to elevations in excess of 7000 and in some cases 7500 feet. At Leavett Lake (9600 feet) snow depth went from 43 to 80 inches and Squaw Valley (8200 feet) snow depth went from 28 to 74 inches Summary A high latitude blocking pattern over the Bering Sea allowed short-wave energy to cut beneath the block resulting in a deep cut-off 500 hpa cyclone over the eastern Pacific. These waves brought several surges of high PW air into California resulting in a multi-day heavy precipitation event. Rainfall totals in orographically favored regions received in excess of 500 mm (20 inches) of rainfall. Much of the heavy rainfall fell in managed water shed which store water for the larger metropolitan areas of California. Initial reports (AP 2012) suggest that the rainfall increased water storage by over 10%. Thus, the heavy rainfall produced limited flood damage and the heavy snows likely made a positive contribution to water storage potential. The surges of high PW air, referred to as Atmospheric Rivers (Ralph 2012), often characterized by above normal PW as identified in PW anomaly fields and high values on integrated water vapor transport (IVT: Wick 2012) were generally well predicted by NCEP models and ensemble prediction systems. The relatively well known and well predicted pattern and the resulting provided confidence in the pattern which alerted forecasters to the potential for an extreme rainfall event. This combined with high values of QPF in the models and ensemble prediction systems produced high confidence in forecasts of extreme rainfall. This multi-day event was characterized by several surges of an AR into the region. Similar to Warner et al (2012) and Junker et al (2009), the AR was relatively narrow and produced locally 1 Alex Tardy NWS provide rainfall, snowfall and snow elevation totals along with flows in major basins.

7 heavy precipitation for several relatively short periods of time (see Fig. 6 Warner et al. 2012), generally less than hours in duration over about 72 days. The pattern of anomalies, with a deep trough and negative height and temperature anomalies over the eastern Pacific and positive height and temperature anomalies over the Great Basin were identified by both Warner et al (2012) and Junker et al (2009). Both studies also showed the surges of high PW air with above normal PW surges into the affected regions. This case fit this idealized model well and the idealized model was well predicted by the NCEP forecasts systems. It is interesting to note that similar to this event that Warner et al (2012) found a positive height anomaly over the Bering Sea (see their Fig. 11& 15a) suggesting blocking over the northern Pacific played a role in the heavy precipitation events. The GEFS reforecasts (Hamill 2012) were used to compare two events from the published literature. The results shown here suggest that the GEFS can predict the pattern associated with heavy rainfall along the West Coast and that this relatively coarse global forecast system and produced heavy rainfall in the correct geographic domain. The total QPF in these re-forecasts suggests that the system can produce 150 and 250 mm of QPF in 48 to 72 hour time periods. Knowing the upper limit of the systems PDF could be of value to forecasters. It is likely that when a system is predicting a record or near record event in its phase space that a record event is a potential outcome in the phase space of the atmosphere. Future and planned work to exploit model internal climatology (M-Climate) needs to be further explored and exploited. As good as the operational GEFS QPFs were for this event and the re-forecasts were for the two historic events, forecasting QPF is still a mesoscale issue requiring high resolution models and ensembles to better define the regions and potential basins which may be affected by extreme precipitation. In this event, most of the heavy precipitation fell in well managed watersheds limiting the impact of the rainfall. Not all basins are well managed and many extreme rainfall events, such as this one, are often high impact weather events. 8. Acknowledgements Links to data and aspects of this event were provided by members of the Albany MAP. Lance Bosart described the pattern associated with this event in the MAP. Forecast issues were discussed and reviewed in real-time as this well anticipated event unfolded. Links to the GEFS reforecasts were provided by Ryan Maue of the MAP. 9. References

8 Hamill, T. M., G. T. Bates, J. S. Whitaker, D. R. Murray, M. Fiorino, T. J. Galarneau, Jr., Y. Zhu, and W. Lapenta, 2012: NOAA's second-generation global medium-range ensemble reforecast data set. Bull Amer. Meteor. Soc., submitted. Junker, N.W, M.J.Brennan, F. Pereira,M.J.Bodner,and R.H. Grumm, 2009a:Assessing the Potential for Rare Precipitation Events with Standardized Anomalies and Ensemble Guidance at the Hydrometeorological Prediction Center. Bulletin of the American Meteorological Society,4 Article: pp Junker, N.W, M.J.Brennan, F. Pereira,M.J.Bodner,and R.H. Grumm, 2009b:Assessing the Potential for Rare Precipitation Events with Standardized Anomalies and Ensemble Guidance at thehydrometeorological Prediction Center. Bulletin of the American Meteorological Society,4 Article: pp Junker, N. W., R. H. Grumm, R. Hart, L. F. Bosart, K. M. Bell, and F. J. Pereira, 2008: Use of standardized anomaly fields to anticipate extreme rainfall in the mountains of northern California. Wea. Forecasting,23, Moore, B.J, PJ. Neiman, F. M Ralph and FE. Barthold 2012: Physical Processes Associated with Heavy Flooding Rainfall in Nashville, Tennessee, and Vicinity during 1-2 May 2010: The Role of an Atmospheric River and Mesoscale Convective Systems,MWR, Ralph, F. M., M. D. Dettinger, 2012: Historical and National Perspectives on Extreme West Coast Precipitation Associated with Atmospheric Rivers during December Bull. Amer. Meteor. Soc., 93, Warner, Michael D., Clifford F. Mass, Eric P. Salathé, 2012: Wintertime Extreme Precipitation Events along the Pacific Northwest Coast: Climatology and Synoptic Evolution. Mon. Wea. Rev., 140, Wick, G. A., P.J. Neiman, and F.M. Ralph, 2012: Description and validation of an automated objective technique for identification and characterization of the integrated water vapor signature of atmospheric rivers. IEEE Trans. Geosci. Remote Sensing, (in press).need to get copy of this.

9 Figure 1. GFS 00-hour forecasts of 500 hpa heights (contours) and 500 hpa standardized anomalies (shaded) in 24 hour increments 1200 UTC a-f) 28 November through 03 December Contours every 60m and anomalies as in the color bar. Return to text.

10 Figure 2. As in Figure 2 except for precipitable water (mm). Contours every 10 mm. Return to text.

11 Figure 3. Stage-IV precipitation (mm) data over California showing 24-hour precipitation for the four periods ending at a) 0000 UTC 30 November, b) 0000 UTC 1 December, c) 0000 UTC 2 December and d) 0000 UTC 3 December Shading as in color key to the right of each image. Return to text.

12 Figure 4. As in Figure 3 except for total accumulated precipitation (mm) from 0000 UTC 29 November 2012 through 1200 UTC 3 December County boundaries are in light gray. Return to text.

13 Figure 5. As in Figure 2 except for precipitable water in 6-hour increments from a-f) 1200 UTC 29 November 2012 through 1800 UTC 30 November Return to text.

14 Figure 6, As in Figure 5 except for 850 hpa moisture flux (kgms-1) and moisture flux anomalies. Return to text.

15 Figure 7. As in Figure 6 except for 850 hpa moisture flux from a) 1200 UTC 1 December through f) 1800 UTC 2 December Return to text.

16 Figure 8. NCEP GEFS forecasts of ensemble mean QPF (mm: shaded and dashed black contours) and each ensemble members 125 mm contour (colored lines) and the ensemble mean 125 mm contour (Thick black). Forecasts valid for the period of 1200 UTC 30 November trhough 1200 UTC 2 December 2012 from forecasts initialized at a) 1200 UTC 24 November, b) 1200 UTC 25 November, c) 1200 UTC 26 November, d) 1200 UTC 27 November, e) 1200 UTC 28 November, and f) 1200 UTC 29 November Return to text.

17 Figure 9. As in Figure 8 except the probability of 125 mm or more precipitation (shaded) and the ensemble mean 125mm contour. Return to text.

18 Figure 10. As in Figure 9 except for forecasts of 175 mm of precipitation for GEFS initialized at a) 0000 UTC 27 November, b) 0000 UTC 28 November, c) 1200 UTC 28 November, d) 0000 UTC 29 November, e) 1200 UTC 29 November and f) 0000 UTC 30 November The time window and ensemble cycles were picked based on those that had 1 or more members with 175 mm or more precipitation. Return to text.

19 Figure 11. NCEP 16km SREF precipitation forecasts from NCEP SREF initialized at a-d) 0300 UTC 30 November, b-e) 0900 UTC 30 November, and c-f) 1500 UTC 30 November Upper panels show each member probability of 150 mm or more precipitation and the ensemble mean 150 mm contour if present. Lower panels show the ensemble mean QPF (shaded) and each member s 150 mm contour. Return to text.

20 Figure 12. As in Figure 11 except for 125 m of QPF.. Return to text. NWS State College Case Examples

21 Figure 13. GEFS reforecasts of precipitable water (mm) and precipitable water anomalies valid at 1200 UTC 01 January 1997 from GEFS forecasts initialized at 0000 UTC a) 25 December 1996, b) 26 December, c) 27 December 1996, d) 28 December 1996, e) 29 December 1996, and f) 30 December This cases is referred to as the December 1996-January 1997 event or January 1997 event.. Return to text.

22 Figure 14. As in Figure 8 except for GEFS reforecasts for the January 1997 event for 200 mm of precipitation from GEFS initialized at 0000 UTC a) 26 December b) 27 December, c) 28 December, d) 29 December, e) 30 December, and f) 31 December Return to text.

23 Figure 15. As in Figure 14 except for the probability of 200 mm or more precipitation for the period of 1200 UTC 31 December 1996 through 0000 UTC 3 January 1997Return to text.

24 Figure 16. GEFS reforecasts valid at 1200 UTC 18 December 2010 showing the mean precipitable water (mm) and precipitable water anomalies (upper panels) and the spaghetti plots of 25 and 50mm precipitable water contours and the variance about the ensemble mean. Data for GEFS initialized at a-d) 0000 UTC 14 December 2010, b-e) 0000 UTC 15 December 2010, and c-f) 0000 UTC 16 December Return to text.

25 Figure 17. As in Figure 14 except for GEFS valid 1200 UTC 17 December through 1200 UTC 18 December 2010 from GEFS initialized at a) 0000 UTC 14 December, b) 0000 UTC 15 December, c) 0000 UTC 16 December, and d) 0000 UTC 17 December Return to text.

26 Figure 18. As in Figure 16 except for the probability of 200 mm or more precipitation and the ensemble mean 200 mm contour. Return to text.

27 Location Region 7-day rainfall total Brandy Creek Shasta Lakeshore Shasta Stouts Meadow Shasta Girard Shasta Stirling City Feather Bucks Lake Feather La Porte Feather Four Trees Feather Huysink Folsum Deer Creek Folsum Sierra City Folsum Blue Canyon Folsum Table 1. 7-day rainfall totals for the full event at select sites and the region. Data show 7- day rainfall totals in inches.

28 State County Location Rainfall CA HUMBOLDT COUNTY HONEYDEW 1 SE CA HUMBOLDT COUNTY PETROLIA 7.4 SE CA DEL NORTE COUNTY CAMP SIX CA HUMBOLDT COUNTY COOSKIE MTN CA HUMBOLDT COUNTY BRIDGEVILLE 5.2 ENE CA HUMBOLDT COUNTY MIRANDA 4.1 SW CA HUMBOLDT COUNTY SHELTER COVE 1.2 ENE CA TRINITY COUNTY COFFEE CREEK CA TRINITY COUNTY MAD RIVER 12 SE CA HUMBOLDT COUNTY REDWAY 1.8 WSW CA DEL NORTE COUNTY GASQUET CA MENDOCINO COUNTY YORKVILLE CA HUMBOLDT COUNTY GARBERVILLE 2.9 SW CA TRINITY COUNTY MAD RIVER 7.4 SE CA TRINITY COUNTY RUTH CA TRINITY COUNTY TRINITY CENTER CA MENDOCINO COUNTY LAYTONVILLE CA TRINITY COUNTY TAYLOR RIDGE CA MENDOCINO COUNTY WILLITS HOWARD CA DEL NORTE COUNTY CRAZY PEAK CA DEL NORTE COUNTY CRESCENT CITY 4.2 NE CA DEL NORTE COUNTY ELK VALLEY CA HUMBOLDT COUNTY BRIDGEVILLE CA TRINITY COUNTY ZENIA 2 ENE CA MENDOCINO COUNTY HOPLAND 2.4 WNW CA DEL NORTE COUNTY CRESCENT CITY 5.5 NNE CA TRINITY COUNTY SCORPION CA TRINITY COUNTY MAD RIVER CA MENDOCINO COUNTY LEGGETT CA HUMBOLDT COUNTY WESTSIDE CA HUMBOLDT COUNTY KNEELAND CA HUMBOLDT COUNTY EEL RIVER CAMP Table 2. Rainfall amounts 30 November to 4 December where rainfall was in excess of 10 inches or 250 mm.

29 Appendix 1 24 Hour Synoptic Precipitation (Inches) Ending 1200 UTC Thu Nov Courtesy NOAA/NWS/California Nevada River Forecast Center

30 Appendix 2 24 Hour Synoptic Precipitation (Inches) Ending 1200 UTC Fri Nov Courtesy NOAA/NWS/California Nevada River Forecast Center

31 Appendix 3 24 Hour Synoptic Precipitation (Inches) Ending 1200 UTC Sat Dec Courtesy NOAA/NWS/California Nevada River Forecast Center

32 Appendix 4 24 Hour Synoptic Precipitation (Inches) Ending 1200 UTC Sun Dec Courtesy NOAA/NWS/California Nevada River Forecast Center

33 Appendix 5 24 Hour Synoptic Precipitation (Inches) Ending 1200 UTC Mon Dec Courtesy NOAA/NWS/California Nevada River Forecast Center

34 Appendix 6 24 Hour Synoptic Precipitation (Inches) Ending 1200 UTC Tue Dec Courtesy NOAA/NWS/California Nevada River Forecast Center

35 Appendix 7 24 Hour Synoptic Precipitation (Inches) Ending 1200 UTC Wed Dec Courtesy NOAA/NWS/California Nevada River Forecast Center