Weather

314 
fxus61 kphi 060810 
afdphi 


Area forecast discussion 
National Weather Service Mount Holly New Jersey 
410 am EDT Monday Oct 6 2008 


Synopsis... 
nice Fall weather for a good part of the week as high pressure 
covers the region into Thursday. Temperatures at night may get down 
to freezing across the southern Poconos, Lehigh Valley and northern 
New Jersey with some frosty conditions. 


&& 


Near term /through tonight/... 
overall pattern is unchanged since first midnight shift. What has 
changed is the amount of precipitation that once looked liked a 
soaking rain for parts of the region but now looks like little if 
any will fall. Clouds overspreading the cfa this morning but not 
much in the way of showers. There is a west to East Line of light 
precipitation across Pennsylvania and will accordingly move it 
with the upper flow until it clears our cfa this afternoon. 
Also... we'll continue to see the the clouds move southeast on the 
fast flow from the northwest. The upper level boundary will pass 
north to south through US today and clearing will settle in by the 
late morning and afternoon. There may still be a brief shower or 
sprinkles passing through today so will keep mention in forecast. 
Before that however, there will be some patchy dense fog across 
part of the region. At this hour...3 am...there is enough of a 
temperature/deep spread but that will close in by daybreak. Winds are 
practically calm everywhere. Once the front pass through the high 
pressure builds south from James Bay toward evening with clearing 
skies cold air advection filtering down the coast. 


Highs today will be in the middle 50s to lower 70s well south. Under 
clear skies tonight and light winds temperatures will reach near 
freezing northern areas and low to middle 40s south. Will be issuing 
a freeze warning for Carbon/Monroe and Sussex New Jersey for a more 
widespread freeze and a frost advisory for parts of Berks...Lehigh 
Northampton in PA...and Warren and northern Morris in New Jersey. 


&& 


Short term /Tuesday through Wednesday/... 
this part of the forecast will be the best with clear skies and 
crisp air but some overnight lows will bring freezing temperatures 
and perhaps widespread frost tonight and Tuesday night. High 
pressure will be firmly in place over the region with sunshine and 
highs Tuesday in the upper 50s to the upper 60s. Overnight lows 
will range from the lower 30s(freezing mark)north to the low and 
middle 40s south. Will more than likely need frost or freezing 
bulletins again for Tuesday night into Wednesday. 


&& 


Long term /Wednesday night through Sunday/... 
the weather changes during this period with the high pressure 
moving offshore and the combination of the low moving out of the 
Mississippi Valley being caught up in the fast Pacific zonal flow 
by Wednesday night. The miss low will deepen down to 568dm with a 
mini 50 knots jet of 50-55kt east of the center bringing in warm 80h 
temperatures and plenty of moisture from the Gulf. It will be a 
race to see if the fast flow north of the low drops far enough 
south to just bring US some light showers or will the backing 
winds aloft arrive in time to bring the low with attendant 
precipitation into our cfa. The GFS is starting to show this 
happening with an almost negative with diffluence aloft moving 
north with a healthy band of heavy showers across our Delaware-Maryland-Virginia 
zones by Friday morning. This is slightly different from last night 
when a low developed and move slowly north. This morning, the 
gradient from the weak surface feature is interacting with the 
western edge of the Atlantic ridge and brings a bullseye of 2-3 
inch quantitative precipitation forecast skirting by the del/New Jersey coasts by Friday evening then 
continuing parallel to the coast toward Long Island. Ahead of the 
low will some some gusty onshore winds of 30 to 35 kts at 80h but 
strong warm air advection that will keep strongest winds aloft. 


The upper low continues north into New York state while weakening, 
and the surface feature is absorbed in the overall environment of 
the west Atlantic high Saturday afternoon. Precipitation should be 
tapering off across southern zones Saturday morning and Saturday 
afternoon remainder of zones. Our weather dries into Sunday but 
there is a lot happening in the plains down to the Gulf... 


A northern branch and southern branch set up develops from the 
Great Lakes to the Texas Gulf Coast. The atmosphere is getting set 
for its fall transition. 


After the chill on Wednesday temperatures rise well above normal 
during the day and nighttime hours. While the Poconos reach the 
middle 60s(normal 59) the Delaware-Maryland-Virginia zones reach near 80(normal 69) by 
the weekend. 


&& 


Aviation /08z Monday through Friday/... 
for the most part, conditions are VFR early this morning and will 
remain that way today. However, there are a few notable exceptions. 
A band of low clouds and fog has moved across kacy and kmiv. It 
appears to be advecting out of those locations at this time. Ceilings dropped 
to 100 feet and visibilities were locally less than a mile when the clouds 
and fog were over these sites. A few more periods of LIFR/IFR can 
not be ruled out through daybreak. 


Otherwise, satellite shows an area of middle-level clouds working 
across PA and into New Jersey. These clouds are in advance of a strong 
upper level disturbance which will cross the region today into this 
evening. The models have all trended drier with this system, and 
little in the way of sensible weather is expected with this system. 


Once this vorticity moves by, a very strong area of high pressure will 
move into the region later tonight through midweek. This will bring 
excellent flying weather through Wednesday. 


Outlook... 
the high will move to the east Wednesday into Thursday allowing for 
a return flow. A storm system may approach the region for the second 
half of Thursday into Friday. However, there is considerable 
uncertainty with this next system. The European model (ecmwf) is much drier and has 
a more optimistic forecast overall than the GFS. 


&& 


Marine... 
a vigorous upper level disturbance will move across the area today 
into this evening, but have little effect on sensible weather. A 
very strong 1030+ mb high will then build in later tonight into 
midweek. The pressure gradient between the departing vorticity and the 
building high will strengthen during the day today and peak tonight. 
All of the available model data indicates that while winds and seas 
will increase, they will remain below Small Craft Advisory criteria. This is the 
third straight night that the wavewatch data has decreased seas from 
5 feet to 3 feet. While a brief spike to 5 feet can not be ruled out, it 
is not expected to be widespread. Also, winds may briefly gust to 25 
kts, but again they are not expected to last. Due to the fact that 
things continue to look marginal, will hold off on issuing any 
marine flags at this time. 


As the high build into the region Tuesday into Wednesday, the winds 
will diminish. This high will then slide to the east on Wednesday 
with a return flow becoming established. A storm system then affect 
the area Thursday into Friday. However, there is substantial model 
uncertainty with respect to this system. The European model (ecmwf) is much weaker and more 
suppressed than the GFS. If the GFS were correct, additional marine 
flags may be needed by the end of the week. 


&& 




Phi watches/warnings/advisories... 
PA...frost advisory from 2 am to 8 am EDT Tuesday for paz060>062. 
Freeze warning from 2 am to 8 am EDT Tuesday for paz054-055. 
New Jersey...frost advisory from 2 am to 8 am EDT Tuesday for njz007-008. 
Freeze warning from 2 am to 8 am EDT Tuesday for njz001. 
Delaware...none. 
Maryland...none. 
Marine...none. 


&& 


$$ 
Synopsis...eberwine 
near term...eberwine 
short term...eberwine 
long term...eberwine 
aviation...nierenberg 
marine...nierenberg 

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