000 
fxus61 kphi 200920 
afdphi 


Area forecast discussion 
National Weather Service Mount Holly New Jersey 
420 am EST Tue Feb 20 2018 


Synopsis... 
high pressure off the East Coast will provide southwesterly 
winds and unseasonably mild weather today and Wednesday. A cold 
front is forecast to cross the area Wednesday night. This 
frontal system is expected to remain across the mid- Atlantic 
region through the latter part of this week and into the 
weekend, with a chance for rain each day. Temperatures should 
remain near or somewhat above normal through this period. 






&& 


Near term /until 6 PM this evening/... 
a stationary/warm front extended from central New Jersey, 
southward across the Delmarva, and southward across the East 
Coast, before looping back across the western Appalachians and 
northward across western Pennsylvania. Areas south and east of 
the front remain mostly fog free, while the areas north and west 
of the front are socked in with low clouds and dense fog. This 
front may push back eastward through daybreak, allowing for the 
fog to spread toward the coast. So we will keep the dense fog 
advisory in place. We expect the front to lift north of the area 
as a warm front during the daytime today. Once the front lifts 
north of the area, we expect some clearing, and the fog and low 
clouds to dissipate. However, this will likely be a slow trend 
for many areas. This will make the forecast for the day tricky. 
If the low clouds and fog do not burn off quick enough, daytime 
temperatures will not have enough time to warm up. The current 
expectation is that the clouds and fog will begin to dissipate 
and lift by late morning or early afternoon, which will allow 
for some warming. So we leaned closer to the warmer guidance 
since we expect some clearing. Outside of some drizzle this 
morning, we expect the area to remain preciptation free for 
today as there are not any short waves/vorticity impulses 
expected. 


&& 


Short term /6 PM this evening through 6 am Wednesday/... 
any clearing this afternoon is expected to be short lived as 
clouds and fog/drizzle are expected to develop again tonight. 
While the warm front is expected to have lifted north of the 
area during the day today, our area will remain withing a 
warm/moist southwest flow as high pressure remains off the East 
Coast. This warm/moist air will allow the low levels to saturate 
again, and in turn allowing for the low clouds and fog/drizzle 
to form. It is very possible that another night of dense fog is 
in store for the area, and another dense fog advisory may be 
possible tonight. Outside of any drizzle overnight, we expect 
the area to remain precipitaiton free overnight. 


&& 


Long term /Wednesday through Monday/... 
the long-term period begins with a continuation of unseasonably 
mild weather, aided by southwesterly flow around and unusually 
strong mid-/upper-level ridge along the East Coast. At least 
some partial sunshine is expected to help temperatures reach the 
low to mid 70s in most areas. A number of Max temperature 
records are likely to be broken; see the climate secction below. 


Later on Wednesday the upper ridge begins to be suppressed and a 
cold front is forecast to push south across the forecast area 
Wednesday night. There does not seem to be much forcing for upward vertical velocity 
with the front so we have included only a slight chance of 
showers for most areas with the frontal passage. The front will 
result in a return to more normal temps for late February. 


This front is expected to stall somewhat south of Delaware. 
However the cool air looks rather shallow and low level warm 
advection develops above it by Thursday and and continues into 
Friday/Saturday. This warm air advection plus some apparent weak impluses in 
the continuing SW flow aloft should result in periods of rain 
for the latter part of the week and into the weekend. Confidence 
in the timing however is below average. Daytime highs should 
gradually increased above normal. 


By Sunday a stronger shortwave trof is forecast to approach from 
the west, with the associated surface frontal system to cross 
the mid-Atlantic region late in the day. More widespread rain is 
expect ahead of the is system on Saturday night and Sunday, 
followed by clearing on Monday. 


&& 


Aviation /08z Tuesday through Saturday/... 
the following discussion is for kphl, kpne, kttn, kabe, krdg, 
kilg, kmiv, kacy and surrounding areas. 


Today-tonight...low clouds and fog/drizzle will persist across the 
taf sites through at least the mid-late morning hours as our area 
remain no the northern side of a frontal boundary to our south. 
While Acy and miv do not have the LIFR conditions the rest of the 
taf sites do, we expect them to lower through daybreak. As the 
frontal boundary to our south lifts north of the area today, we 
expect an improvement to the conditions for a period this afternoon. 
However, this improvement is expected to be temporary as low clouds 
and fog/drizzle are once again expected to develop after sunset and 
likely persist through the night. IFR conditions are expected again 
tonight through Wednesday morning. 


Winds this morning will be light and varialbe for many locations, 
although some areas will continue with southwest winds around 5-10 
knots. All areas are expected to have their winds increase to 5-10 
knots out of the southwest today. Some areas will even see some 
gusts around 15-20 knots, especially where the clouds break up and 
dissipate. The southwest winds will continue into tonight, with some 
areas becoming light and variable. 


Outlook... 


Wednesday...fog and stratus dissipate in the morning, giving way 
to VFR conditions. SW winds 10-15 kt with gusts to 20 kt. 
Confidence: above average. 


Wednesday night...scattered showers and patchy fog possible with 
sub-VFR conditions. Winds shift from SW to north in the evening. 
Confidence: average. 


Thursday...sub-VFR conditions possible in scattered showers. NE 
winds 10-15 kt. Confidence: average. 


Thursday night...sub-VFR conditions possible in scattered 
showers. Confidence: below average. 


Friday through Saturday...sub-VFR conditions in periods of rain. 
Confidence: below average. 


&& 


Marine... 
the dense fog advisory remains across the waters through this 
morning. It is possible that the fog may continue through the 
day, and into tonight. Even if there is some clearing during the 
day today, the fog will likely redevelop this evening and 
overnight. So the dense fog advisory may need to be extended 
later this morning, or another may need to be reissued for later 
tonight. 


Winds and seas are expected to remain below advisory levels for 
today and tonight. However, winds may gust around 20 knots at times 
and seas will be around 3-4 feet. 


Outlook... 


Wednesday...Small Craft Advisory conditions possible on the ocean with gusty SW 
winds. 


Wednesday night...sub-sca conditions expected.SW winds turning 
northwest overnight. 


Thursday...Small Craft Advisory conditions possible on the ocean waters. 


Friday through Saturday...sub-sca conditions anticipated. 




&& 


Climate... 
record high temperatures are possible today and Wednesday. 


Tuesday, February 20: 


Atlantic City...70 in 1930 
Philadelphia....70 in 1939 
Wilmington......71 in 1930 
Allentown.......68 in 1930 
Trenton.........70 in 1930 
Georgetown......68 in 2002 
Mount Pocono....59 in 1930 
reading.........72 in 1930 


Wednesday, February 21: 


Atlantic City...74 in 1930 
Philadelphia....72 in 1930 
Wilmington......70 in 1953 
Allentown.......67 in 1953 
Trenton.........70 in 1930 
Georgetown......71 in 2014 
Mount Pocono....60 in 1930 
reading.........71 in 1930 


A record warm minimum temperature may be set for Atlantic City 
on Tuesday. The current record is 44 in 1949. 


The following are the record warm minimum temperatures for 
Wednesday, all which should be exceeded. 


Abe 46-1981 
Acy 49-1954 
phl 49-2002 
ilg 47-2002 
ridge 48-1930 
ttn 48-2002 


The all time February Max temps may be approached on Wednesday 
at ilg, ttn, Ged ridge mpo. All the all time monthly Max's are 
listed below: 


Acy 77 2/25/30 
phl 79 2/25/30 
ilg 78 2/24/85 
Abe 77 2/24/17 
ttn 76 2/25/30 
Ged 77 2/25/17 
ridge 77 2/24/17 
mpo 70 2/25/30 


Our expectation is that Acy will exceed the previous all time 
record rainfall for February, by the end of the weekend. The 
record is 6.50 inches in 2010. #2 is 1958 with 5.98 inches. 


And...adding only half an inch to phl and ilg will put both 
locations in the top 9 ranking for Feb rainfall. 


Have rechecked the monthly projection at phl and the avg temp 
continues at 41.0 or 5.3f above avg which is 8th warmest on 
record, if it holds. Add or subtract a degree to the 
average/departure and the ranking changes from 3rd to 11th. The 
forecast 5.3f departure is ~2f warmer than the current 
departure. I'd expect similar for the rest of our area...a bit 
less in the north which will have better chances for colder air, 
and a bit more warming in the south where the positive 
departure as of yesterday was already 5f above normal, heading 
for 7+. So all in all it appears we're heading for a top 10 
warmest February. Last year was the warmest on record, a 
whopping 3+f degrees warmer than our current projection. 


&& 


Phi watches/warnings/advisories... 
PA...dense fog advisory until 10 am EST this morning for paz054-055- 
060>062-070-071-101>106. 
New Jersey...dense fog advisory until 10 am EST this morning for njz001- 
007>010-012>027. 
Delaware...dense fog advisory until 10 am EST this morning for dez001>004. 
Maryland...dense fog advisory until 10 am EST this morning for mdz008-012- 
015-019-020. 
Marine...dense fog advisory until 10 am EST this morning for anz430-431- 
450>455. 


&& 


$$ 
Synopsis... 
near term...Robertson 
short term...Robertson 



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