000 
fxus61 kphi 160042 
afdphi 


Area forecast discussion 
National Weather Service Mount Holly New Jersey 
742 PM EST Fri Dec 15 2017 


Synopsis... 
surface low pressure, well off the Delmarva, will track 
northeast into the open Atlantic this evening. High pressure, 
centered over the southeastern United States, will nose into the 
region early on Saturday. This will be short-lived as a cold 
front, coming in from the north, will move into or through the 
area on Saturday night and Sunday. This front will then stall 
before lifting northward as a warm front Sunday night and 
Monday. A cold front will progress through the region around the 
middle of next week. Another system may affect the area near 
the close of next week. 


&& 


Near term /until 6 am Saturday morning/... 
the Winter Weather Advisory has been cancelled for all but our 
coastal counties and central New Jersey. 


Our upper level jet enhanced light snow event was coming to an 
end this evening. The back edge of the accumulating snow was in 
our coastal counties. It should be off the coast shortly. 


Snowfall accumulations in the 1 to 3 inch range were common, 
except in the Poconos and far northern New Jersey and in parts 
of northeastern Maryland and central and southern Delaware where 
totals were less than an inch. 


Gradual clearing is anticipated for tonight as the system moves 
farther off the coast. 


A west wind should increase to 5 to 10 miles per hour. Minimum 
temperatures are forecast to favor the teens in much of eastern 
Pennsylvania and northern New Jersey, and the lower and middle 
20s in southern New Jersey and on the upper Delmarva. 


&& 


Short term /6 am Saturday morning through 6 PM Saturday/... 
shortwave energy rotating around the based of the large scale 
trough is forecast to move across the Great Lakes and northeast 
states on Saturday. At the surface, a weak area of low pressure 
will pass to our north but a northwest flow behind this 
disturbance will help steer a cold front southward into the I-80 
corridor by the late afternoon. 


Even with the deepest, more organized synoptic lift staying to 
our north, models show a ribbon of low-level 
convergence/frontogenetical lift near the front that could 
support some snow shower activity across the I-80 and I-78 
corridor during the mid to late afternoon. We are currently only 
expecting minor accumulations. Elsewhere, expect clouds to 
increase as the day progresses. 


Forecast high temperatures range from the lower 30s across the 
I-80 corridor to the lower 40s in Delmarva and coastal New Jersey. 


&& 


Long term /Saturday night through Friday/... 
overview...the period starts with a deepening surface low off 
Delmarva. This low will track to the northeast overnight into 
the open Atlantic. Surface high pressure, centered across the 
deep south, will push up into the mid-Atlantic by daybreak 
Saturday. This high won't hang around long. A cold front, coming 
in from the north, will move into or through the forecast area 
Saturday night into Sunday. This front will back up as a warm 
front Sunday night into Monday. Another cold front will push 
through the region in the Tuesday/Wednesday timeframe. Surface 
high pressure is expected on Thursday. This will elide to a warm 
front later on Thursday into Friday and a cold front very late 
in the period. Both of these fronts are associated with low 
pressure moving across the eastern Great Lakes. 


Temperatures...for reference, normals for kphl are around 30 
and in the middle 40s. Sunday will be slightly below normal. 
Monday and Tuesday will be above normal with some mid-50s 
possible across portions of the coastal plain. Wednesday looks 
to be about normal with Thursday slightly below. Friday will 
rebound once again with above normal temperatures. Once again, 
portions of the coastal plain could see temperatures top out in 
the middle 50s. 


Precipitation...small pops have been inserted late Sunday and 
maintained into Sunday night. This associated with the warm 
front in the vicinity. Small pops will continue into Monday and 
through Tuesday night. Wednesday and Thursday will be pop free 
behind the mid-week cold front. Some chance pops will be 
inserted into the grids on Friday. 


Winds...fairly benign through the period. Moist noticeable 
winds will be right ahead and behind the cold front Tuesday and 
Wednesday. 


Impacts...while the forecast will see a roller coaster week 
with temperatures and multiple chances of precipitation, none 
are expected to create widespread hazardous weather at this 
time. 


&& 


Aviation /01z Saturday through Wednesday/... 
the following discussion is for kphl, kpne, kttn, kabe, krdg, 
kilg, kmiv, kacy and surrounding areas. 


This evening...improving to VFR. Light and variable wind. 


Overnight...VFR. Clearing. West wind 4 to 8 knots. 


Saturday...VFR. Mostly clear in the morning, then increasing 
clouds. West to southwest wind 5 to 10 knots. 


Outlook... 
Saturday night...generally VFR with light and variable winds. 
Medium confidence. 


Sunday...generally VFR. Light northeast winds to start the day 
and southeast to finish. Increasing clouds and a small chance of 
precipitation later in the day. Medium confidence. 


Sunday night and Monday...generally VFR, though brief sub-VFR 
conditions are possible with light rain or snow, especially 
north of phl. Light winds generally transitioning from southeast 
to southwest during the period. Low confidence. 


Monday night and tuesday: sub-VFR conditions possible, with 
scattered showers during the period, especially on Tuesday. 
Winds primarily southwest at 5 to 15 kts. Medium confidence. 


Tuesday night and Wednesday...generally VFR. Decreasing clouds 
and showers on Tuesday night. No precipitation expected on 
Wednesday. Winds west or northwest 10 to 20 mph. Medium 
confidence. 


&& 


Marine... 
northwest winds expected increase this evening as low pressure 
intensifies while tracking to our east. Opted for a Small Craft Advisory instead 
of a glw for tonight and Saturday with winds generally in the 
25-30 kt range. However, a brief ramp up in winds are expected 
late tonight when pressure rises behind the offshore low are 
greatest. An isolated gust to near gale force at our offshore 
buoys is certainly a possibility. 


Outlook... 
Saturday night: residual advisory-level northwest winds in the 
evening will diminish overnight. Gale force gusts during the 
evening can't be ruled out. Seas below criteria. 


Sunday and Sunday night: sub Small Craft Advisory conditions. 
No headlines anticipated. There may be some light rain in the 
afternoon and overnight with potential for some visibility 
restrictions. 


Monday and Monday night: sub Small Craft Advisory conditions. 
No headlines anticipated. Scattered showers, at times, could 
create visibility restrictions. 


Tuesday: southwest winds increasing to near advisory levels by 
afternoon with seas also building. A chance of showers and 
visibility restrictions. 


Tuesday night and Wednesday...Small Craft Advisory conditions 
expected due to northwest winds behind the front and building 
seas. 


&& 


Phi watches/warnings/advisories... 
PA...none. 
New Jersey...Winter Weather Advisory until 9 PM EST this evening for 
njz012>015-019>027. 
Delaware...Winter Weather Advisory until 9 PM EST this evening for dez003. 
Maryland...none. 
Marine...Small Craft Advisory until 1 am EST Sunday for anz452>455. 
Small Craft Advisory from 11 PM this evening to 1 am EST 
Sunday for anz450-451. 
Small Craft Advisory from 1 am to 6 PM EST Saturday for anz430- 
431. 


&& 


$$ 


Synopsis...kruzdlo 



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