402 
fxus61 kphi 080930 
afdphi 


Area forecast discussion 
National Weather Service Mount Holly New Jersey 
430 am EST Thursday Jan 8 2009 


Synopsis... 
the large low pressure system that affected our area Wednesday will 
continue moving to our northeast today. High pressure will build 
briefly to our south tonight and Friday, but another low pressure 
center will move through our area from the west-southwest Saturday. 
A brisk northwest flow Sunday is expected to be followed by high 
pressure Sunday night, but another front could affect our area later 
Monday into Tuesday. Much colder air will follow for the middle of 
next week. 


&& 


Near term /until 6 PM this evening/... 
cold air advection and gusty winds prevailed in the wake of the 
front that moved east of the area Wednesday night. Clouds had 
broken up over a good portion of the region, but some residual 
stratocumulus was floating though and providing scattered to broken 
conditions early this morning. The chance of snow was continued for 
the northern zones today, but instead of snow showers, it was 
referenced as light snow or flurries...not much difference for 
public consumption in any case. 00z models continued on a 
converged solution for today, as wednesday's storm moves further 
away to the northeast and high pressure builds to our south. The 
broad upper trough will pass through today, adding to diurnally- 
enhanced stratocumulus, and mainly for the terrain-influenced 
northern zones. Gusty winds this morning will abate somewhat this 
afternoon, according to model soundings. Due to the gusts up 
around 30 knots this morning, a mention was inserted into the 
hazardous weather outlook about gusty winds possibly causing tree 
limbs to fall where ice accrued Wednesday, leading to scattered 
additional power outages. A Special Weather Statement issued 
Wednesday night will be reissued, and be in effect through 17z. 


With potent cold air advection today, it was decided to hedge a 
degree or two lower toward the NAM MOS for highs today. 


The Rancocas Creek and Millstone River in New Jersey will crest 
near bankfull. River statements have been issued for these 
events. 


&& 


Short term /6 PM this evening through Friday night/... 
the upper trough will move off to the east tonight as surface 
high pressure builds to our south. Winds will veer a bit to the 
northwest, and any leftover clouds will diminish, with the 
exception of the far northern zones. The northwest flow will 
contribute to at least some cloudiness, and even the possibility 
of a few flurries continuing in the Northern Hills. Continuing 
cold air advection will cause temperatures to fall into the teens 
and 20s. High pressure will be just south of our area Friday, 
giving US a sunny to partly sunny day, with seasonably cold 
temperatures. With the approaching weather system Friday night, 
small snow chances were kept for now for later Friday night. 
However, this may need to be increased as the event nears. 


&& 


Long term /Saturday through Wednesday/... 
another active period lies ahead for the middle-Atlantic region, as 
yet another middle-west low pressure system approaches and looks to 
drive right through our area Saturday. The models have converged a 
bit on the 00z suite, but there are still low level temperature 
differences which will lead to large-ish precipitation type 
uncertainties. For this forecast, the GFS was seen to lie between 
the anomalously cold NAM, and the (eventually, by 00z sunday) 
overly warm European model (ecmwf). So, using a compromise solution, the GFS was 
accepted for now. This means that all areas, even far south, 
should start out as snow late Friday night or Saturday morning. 
Then, with an easterly flow bringing in warmer ocean air, southern 
and eastern areas were allowed to mix with, and even change to 
rain south. This is expected for Saturday afternoon, before the 
process reverses with cold air advection Saturday night, which 
will change the precipitation back to all snow, or mostly all 
snow, before ending Saturday night. For now, a coupe or few inches 
of snow was inserted into the snow amount grids as a first guess, 
which delivered wording of "moderate snow accumulation" north, and 
"light" central. With the somewhat colder solutions on the 00z run 
as compared with the 12z run, more emphasis was placed on snow, at 
least north and central. Probabilities were raised into the likely 
category for Saturday. 


High pressure is seen to nudge into the region Sunday and into 
Monday, but is once again moved offshore later Monday and Monday 
night by a Great Lakes low pressure system. Again, this system 
will provide what will for now be characterized as a very broad- 
brushed amount of precipitation to the region in the form of snow 
and rain. 


The main story in the extended period regarding winter weather is 
going to be the Arctic airmass which descends on the region by 
mid-week. The European model (ecmwf) is showing 1000-850mb thicknesses plummeting 
as the Arctic air continues to filter into the region. With a 
cold frontal passage on Tuesday, 850 hpa temperatures drop from -2c 
on Tuesday morning to around -20c on Wednesday morning. Daytime 
highs on Wednesday may get to near freezing for the far southern 
portion of our area, but elsewhere highs are forecast to be in the 
20s central and only teens in the higher elevations north. 


&& 


Aviation /09z Thursday through Monday/... 
the following discussion is for kphl, kpne, kttn, kabe, krdg, kilg, 
kmiv, kacy and surrounding areas. 


A far cry from Wednesday morning. Conditions are VFR across our taf 
sites with good visibilities and ceilings anywhere from 3,500 to 6,500 
bases. Skies have even cleared over parts of New Jersey and Delaware. Cold 
air advection is developing the usual instability showers and some 
light snow over to our west but not looking for much in the way of 
snow showers except for an area near krdg northeast to kabe until 
around 11z this morning. 


The storm exiting to the northeast doesn't have the blast of cold 
air with it but rather a gradual turning over to chilly conditions. 
Winds will be picking up this morning and may gusts to 30 or 35 
knots briefly this morning. The next chance of precipitation will 
arrive Friday evening in the form of snow. Deteriorating flight 
conditions as the night wears on with an introduction to some 
freezing rain and sleet around. 


Outlook... 
pure Arctic air in the outlook period...................... 
the fast flow aloft continues to be the main story and it's that jet 
that will bring quick moving storms across the terminal control 
area. The one departing to the northwest today...the next arriving 
on Saturday into Sunday with reinforced cold air behind it, and 
another around the 13th followed by a blast of cold air right from 
the Arctic Circle. It will really be cold next Wednesday/Thursday. 


The high next Wednesday at phl (coldest so far this season) will 
be 19 and the low Thursday morning 11 also coldest this season. On 
the other hand, Mount Pocono will have a high on Wednesday of 7 
and a low of -1 on Thursday. 


&& 


Marine... 
seas are up to 8 feet at 44009 and should be around that for a 
couple more hours then start to diminish. There have been gale 
forces winds along the northern and central New Jersey coast. Winds have 
diminished at this time the moment but will gust again to gale force 
especially after sunup as the atmosphere begins to mix. Gales will 
remain up into the the afternoon hours. This is not a full blow gale 
but enough cold air will sweep across the waters to cause the gusty 
winds. Waves in the lower Delaware Bay are 2 feet. High pressure will 
build in the from west today and be offshore Friday afternoon. 


Fast upper flow is bringing several storms our way between Friday 
and next week with each one colder behind it. A real blast of Arctic 
air is on tap for Wednesday. I can remember speaking with several 
fishing grounds last season and they remarked how windy last fall 
and winter had been. Well, this is another windy fall and winter 
with a parade of storms. 


Pure Arctic air on the way next week.............. 


Here is a list storms producing gale force winds since Oct 1... 


The gale force storms since Oct 1st... 
Oct 18...Oct 21...Oct 27...Nov 05...Nov 15...Nov 17...Dec 01... 
Dec 06...Dec 20...Dec 29...Dec 30...Jan 02...Jan 07 


It is tough to find a stretch of nice weather to go fishing and 
more fast moving storms are on the way this weekend into next week. 
Gales are also up for the entire stretch of the canyon areas today 
into Friday and again late Saturday in Sunday. 


&& 


Tides/coastal... 
the winds today are very favorable for causing low water levels. The 
latest AVN surge is showing 2 feet below MLLW which is threshold for 
advertising in the coastal waters forecast. However...NGM is not that extreme and the 
snap shot from the current levels is above the prediction. With 
that will hold off on issuing a low water advisory but keep in mind 
the water levels could fall to around a foot below. 


&& 


Phi watches/warnings/advisories... 
PA...none. 
New Jersey...none. 
Delaware...none. 
Maryland...none. 
Marine...Gale Warning until 4 PM EST this afternoon for anz430-431- 
450>455. 


&& 


$$ 


Synopsis.../ 
near term.../ rpw 
short term.../ rpw 
long term.../ Heavener 
aviation...eberwine 
marine...eberwine 
tides/coastal...eberwine 

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