420 
fxus61 kphi 220133 
afdphi 


Area forecast discussion 
National Weather Service Mount Holly New Jersey 
833 PM EST Friday Nov 21 2008 


Synopsis... 
deep low pressure moving well off the coast will continue to pull 
away from our region overnight. A cold northwest wind will follow 
the storm as high pressure builds in from the west on Saturday. 
Low pressure will move into the northeast and remain stationary 
into a good part of next week. 


&& 


Near term /until 6 am Saturday morning/... 
the timing for the expiration of the Winter Weather Advisory 
worked out well with the last significant echos shown on kdox radar 
clearing the coast around 800 PM. The snow showers caused reduced 
visibilities as they moved by, but no significant accumulations 
were reported. Clear skies and cold dry air has moved in across 
the area this evening and should stay put in most areas overnight. 
Wind chill values are in the teens or low 20s in most areas with 
single digits up on Mount Pocono. These cold readings will continue 
overnight. 


Lake effect is developing well to the north and west across northwest PA 
and upstate New York. Its possible, that some cloudiness and perhaps a few 
snow showers could make it into the northern counties late tonight, so 
chance probability of precipitation were introduced there with the update. The scarcity of 
moisture precludes the mention of anything more significant. 


&& 


Short term /6 am Saturday morning through Sunday night/... 
I decided to keep this period free from precipitation, although 
I suppose a flurry or two could occur across the far northwest 
zones. Any flurries should be so far and few between, even more so 
on Sunday. 


So as the above mentioned low pressure becomes just a memory, 
surface high pressure will expand into the region by Sunday. This 
will help the winds to relax. But before this happens we could see 
gusts approach 35 miles per hour along the coast and 25 miles per hour inland tomorrow. 
Because of this, wind chills will once be similar to tonight, single 
digits and teens. With less wind on Sunday, it won't feel as cold 
although we'll continue in the below normal range. 


&& 


Long term /Monday through Friday/... 
the models are in good agreement through this forecast period in 
terms of the overall pattern, that is a West Coast trof, a ridge in 
the middle, and a somewhat anomalous deep trough over the northeast. 
This will keep the both coasts somewhat unsettled. 


As for the finer model points across the forecast area, both the 
European model (ecmwf) and the GFS are in transition. In fact they've flip-flopped 
later next week. The European model (ecmwf) and it's ensemble mean are now more 
north/northeast with the low when compared to the GFS and it's 
ensemble mean. With nothing to really specifically hang our hat on, 
the HPC compromise appears to be the best course of action. 


Surface high pressure off the Carolinas early on Monday morning will 
drift further off the coast during the day. This will allow a cold 
front to track through the region on Monday night. After the frontal 
passage, the forecast area will be under a broad cyclonic flow as 
low pressure intensifies and meanders over the northeast. 


The best chance of seeing precipitation will be early in the period 
with the cold front. Then exactly where the surface low and it's 
parent trough set's up will dictate what type of shower activity we 
see in the cyclonic flow. For now, we'll favor (with low pops) the 
climatologically favored areas in this pattern, that is north and 
west of of the I-95 corridor. 


Tough to see seasonal levels with the expected pattern. With that 
said, temperatures are forecast to remain below normal right through 
the end of next week. 


&& 


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


At 0100z, the sky over our region was clearing as a disturbance in 
the upper atmosphere continued to push to our south. The visibility 
was unrestricted and there was a northwest wind around 8 to 12 knots 
at most locations. Little change is expected overnight. 


On Saturday, a west northwest wind is expected to increase into the 
10 to 16 knot range with gusts up into the 20s. Some stratocumulus 
will move overhead, mainly for the afternoon hours, with bases in 
the 4500 to 5000 foot range. 


After dark on Saturday, wind speeds are forecast to diminish a bit 
and we should lose the gusts. The cloud cover will also decrease 
for the evening hours. 


Outlook... 
high pressure is forecast to build in from the west for Sunday and 
Sunday night. A cold front is expected to approach from the 
northwest on Monday and it should reach our region on Monday night. 
There is the possibility of rain showers from Monday afternoon into 
Monday night, and perhaps some snow showers late on Monday 
night. 


&& 


Marine... 
the combination of the low pressure system developing well off the 
coast, the high building in from the west, and the cold air 
advection occurring is expected to generate near gale-force winds 
over the waters, especially our Atlantic waters. The gale remains a 
close call, but our thinking based on our guidance is that we will 
not get frequent gale-force gusts over a sustained period of time. 
The worst conditions look to be tonight into tomorrow morning, and 
we are carrying a strong Small Craft Advisory in response. Winds 
look to diminish from west to east through Saturday evening, and the 
timing of the advisory from the previous forecaster is maintained. 


As the storm moves off to the northeast and high pressure pushes in 
from the west, winds and seas will subside. The high pressure system 
will provide tranquil marine weather Sunday into Monday. Complex low 
pressure dropping down from the Great Lakes will bring the next 
threat for inclement weather along with advisory/warning conditions 
late Monday into Tuesday. 


&& 


Phi watches/warnings/advisories... 
PA...none. 
New Jersey...none. 
Delaware...none. 
Maryland...none. 
Marine...Small Craft Advisory until midnight EST Saturday night for 
anz450>455. 
Small Craft Advisory until 6 PM EST Saturday for anz430-431. 


&& 


$$ 
Synopsis...kruzdlo 
near term...O'Hara 
short term...kruzdlo 
long term...kruzdlo 
aviation...iovino 
marine...delisi