Winter Storm Tomorrow-Tomorrow Night · higher in an extended period of poor travel conditions during most of the daytime hours tomorrow, with particular concern for the afternoon

Philadelphia/Mount Holly

Weather Forecast Office Presentation Created 2/19/2019

4:12 PM@NWS_MountHolly NWSMountHolly

Winter Storm Tomorrow-Tomorrow Night

What Has Changed?

Initial Briefing

Decision Support Briefing #1

As of 4:30 PM

Tuesday, February 19, 2019

https://www.facebook.com/NWSMountHolly/

https://twitter.com/NWS_MountHolly




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.






Wintry Mix: E PA, N and W NJ, N DE, NE MD

Snow: NJ, E PA, DE, NE MD

None Limited Elevated Significant Extreme

Summary of Greatest Impacts

None Limited Elevated Significant Extreme






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.






Probabilistic Snowfall Forecast

Low End Potential9 in 10 (90%) Chance of Higher Snowfall

Than Depicted Below

High End Potential1 in 10 (10%) Chance of Higher Snowfall Than

Depicted Below






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.






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.






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.

Event Summary






Web:

www.weather.gov/phi

Phone (public):

(609) 261-6600

Facebook:

NWSMountHolly

Twitter:

@NWS_MountHolly

Contact and Next Briefing Information

Briefing Webpage:

www.weather.gov/media/phi/current_briefing.pdf

Next Briefing By 6:00 AM Wednesday,

February 20, 2019

Disclaimer: The information contained in this briefing is time-

sensitive; do not use after the next briefing package is issued.



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Winter Storm Tomorrow-Tomorrow Night · higher in an extended period of poor travel conditions during most of the daytime hours tomorrow, with particular concern for the afternoon