Winter Storm Tomorrow-Tomorrow Night

Transcription

1 Winter Storm Tomorrow-Tomorrow Night Decision Support Briefing #1 As of 4:30 PM Tuesday, February 19, 2019 What Has Changed? Initial Briefing

2 Main Points Hazard Impacts Location Timing Snow Snow will create hazardous travel conditions. Roadways will be snow covered. Travel conditions for most of the day Wednesday will be impacted, and there is particular concern regarding the evening commute. NJ, east-central and southeast PA, DE, northeast MD. Snow will gradually overspread these areas from southwest to northeast tomorrow morning, from around 6AM to 12PM, with the most intense snow in the late morning and early afternoon. Sleet and Freezing Rain A period of sleet and freezing rain following the initial period of snow will exacerbate already hazardous travel conditions, with up to a tenth of an inch of ice accumulation. Eastern and southeastern PA, northern and western NJ, far northeast MD, far northern DE. Snow will transition to an extended period of sleet and freezing rain from mid-afternoon through the evening. Elsewhere, snow should transition to rain with only a brief mix expected.

3 Summary of Greatest Impacts Snow: NJ, E PA, DE, NE MD None Limited Elevated Significant Extreme Wintry Mix: E PA, N and W NJ, N DE, NE MD None Limited Elevated Significant Extreme

4 Expected Snowfall Accumulations Uncertainty in Snowfall Forecast: As with other storms this season, considerable uncertainty exists in the snowfall forecast owing to critical timings of transitions between snow, ice, and rain. While confidence in exact snowfall totals is medium at best, confidence is higher on a period of significant and widespread travel impacts, especially from mid-morning through the evening.

5 Probabilistic Snowfall Forecast Low End Potential 9 in 10 (90%) Chance of Higher Snowfall Than Depicted Below High End Potential 1 in 10 (10%) Chance of Higher Snowfall Than Depicted Below

6 Expected Ice Accumulations Ice accumulation notes: Icing of a few hundredths to a tenth of an inch is generally insufficient to produce tree damage or power outages, but any amount of ice is capable of creating very hazardous road conditions.

7 Precipitation Onset Time Onset Time Notes: This map represents our best estimate for when snow will begin tomorrow. Owing to cold temperatures tonight, snow should begin accumulating on all untreated surfaces soon after it begins falling.

8 Event Summary A winter storm will impact the area from early tomorrow morning through tomorrow night. A variety of precipitation types are expected. Travel impacts are likely for most of the day Wednesday, except in central and northern NJ and east-central PA where most of the morning should remain dry before snow begins. For all areas, the evening commute is the period of greatest concern, but morning commute impacts are possible in northeast MD, DE, southern NJ, and far southeast PA All areas will likely see precipitation begin as snow. A gradual transition from snow to a mix of sleet and freezing rain, then rain, will occur tomorrow afternoon and evening. Rain will continue for most of the night, potentially ending near daybreak Thursday. Over far northern NJ and the Poconos, precipitation may never transition to plain rain, instead staying as a mix of sleet and freezing rain after the initial period of snow. Considerable uncertainty exists in how much snow will fall. However, confidence is higher in an extended period of poor travel conditions during most of the daytime hours tomorrow, with particular concern for the afternoon and evening. Up to a tenth of an inch of ice is expected in eastern PA and northern NJ, which will lead to hazardous travel conditions into Wednesday night. Over southern NJ and Delmarva, only a brief period of icing is expected before a transition to rain. Localized minor coastal flooding is possible during the Wednesday morning high tide cycle, but this is not expected to be a widespread or significant concern. Strong winds are also not expected to be a concern.

9 Contact and Next Briefing Information Next Briefing By 6:00 AM Wednesday, February 20, 2019 Briefing Webpage: Web: Facebook: Phone (public): (609) Twitter: Disclaimer: The information contained in this briefing is timesensitive; do not use after the next briefing package is issued.