Weather

509 
fxus61 kphi 071055 
afdphi 


Area forecast discussion 
National Weather Service Mount Holly New Jersey 
655 am EDT sun Sep 7 2008 


Synopsis... 
weak high pressure will build over the region today and tonight 
and off the coast Monday. A cold front will drop down from the 
northwest and cross the region Tuesday afternoon and evening. 
Cool, dry high pressure will then build in from the Great Lakes 
region Wednesday and Thursday before moving off the coast Friday. 
Another cold front will approach from the northwest Saturday. 


&& 


Near term /through tonight/... 
skies were mostly clear except to the north and west of phl where 
some leftover low level moisture has allowed stratocu to linger. 
Skies will be mostly sunny today from phl S/east with a west to 
northwest flow and dry air continuing. To the north/west mixing will 
dissipate the clouds later this morning and this afternoon. 
Following the model 1000-850 thicknesses, the airmass has cooled a 
bit and guidance temperatures reflect this with highs a few degrees lower 
than the previous runs. These lower numbers look reasonable, but 
with lots of sunshine, I think the met numbers look too low. 


&& 


Short term /Monday through Monday night/... 
high pressure remains over the area tonight with mostly clear 
skies and light winds. With even drier air arriving from the 
northwest, temperatures should be several degrees cooler than this 
morning with expected lows mostly in the 50s. 


Monday will still be influenced by weak high pressure, which 
will keep skies mostly sunny. High temperatures should be normal or 
slightly above normal considering the thicknesses and 800 mb temperatures. 


Monday night will see a light return flow on the backside of the 
high. This will allow dew points to increase a bit. Also, some high 
clouds associated with an approaching frontal system should move 
over the area. The combination will mean lows should be a few 
degrees higher than tonight and mav looks reasonable. 


A cold front moves through Tuesday afternoon and evening. 
Scattered showers and thunderstorms should accompany the front with partly 
to mostly cloudy skies. Dry cooler air arrives behind the front 
late Tuesday night. Mex temperatures look good for Tuesday/Tuesday night. 
Although Storm Prediction Center has indicated a slight risk of severe Tue, I did not 
mention it in the severe weather potential statement since organized dynamics don't look like they 
will line up with the front and I dint see any jet streaks aloft 
putting US in a favorable quadrant. 


&& 


Long term /Tuesday through Saturday/... 
cool dry high pressure dominates Wednesday and Thursday and then 
moves offshore Friday. The new GFS is similar to the HPC forecasts 
from yesterday, but show the airmass to be cooler with much lower 
dew points. Grids have been updated to reflect this. 


For Friday and Saturday, previous grids and forecast from HPC were 
generally unchanged as moisture increases and this could allow for 
some showers or even thunderstorms. 


&& 


Aviation /12z Sunday through Thursday/... 
skies cleared over eastern area in the wake of Tropical Storm Hanna 
overnight, but stratocumulus has persisted over northwestern 
areas, affecting kabe and just flirting with kttn. These clouds 
should tend to dissipate now that sunrise was occurring, and 
downsloping effects gather strength and drier air works into the 
area. Otherwise, most of the day should feature fine VFR 
conditions, with a light westerly flow and almost full sunshine. 
Visibilities may tend to lower overnight in fog at the more rural 
taf locations, possibly as low as IFR at krdg by Monday morning. 


Otherwise, high pressure behind Hanna will provide fair weather and 
VFR conditions Monday into Tuesday, when a frontal system will move 
in with another possibility of showers and thunderstorms. VFR 
weather is expected Wednesday and Thursday. 


&& 


Marine... 
winds and waves were decreasing in the wake of departing Tropical 
Storm Hanna early this morning. There were still gusts at or just 
above 25 knots on the ocean waters, but gusts had decreased over 
Delaware Bay early this morning so the Small Craft Advisory there 
has been discontinued. Also, seas were still 7 or 8 feet on the 
ocean, especially over eastern reaches. 


Conditions should improve rapidly with the light offshore flow 
that was taking hold, so the Small Craft Advisory will persist 
only until 15z for the ocean waters. Buoy 44009 had subsided to 6 
feet regarding wave heights. The day shift can extend the advisory 
if necessary, as wavewatch was showing seas remaining at 5 feet 
into early afternoon. 


Otherwise, weak high pressure is expected to build over the region 
in the wake of the storm today and continue Monday. Wind speeds and 
seas will continue to remain below Small Craft Advisory levels. A 
cold front from the northwest is slated to arrive Tuesday afternoon 
and evening, with at least scattered additional precipitation, and 
possibly some convection. Conditions may approach Small Craft 
Advisory criteria in the frontal zone. 


&& 


Rip currents... 
the rip current risk will continue in the moderate range for today, 
but it was felt that adding "approaching high" was warranted due to 
the residual long period associated with the swells from departing 
Tropical Storm Hanna, or her extratropical remnants. A coastal flood 
statement was issued, along with the usual surf forecast. 


However, swells from major Hurricane Ike may begin to arrive by 
Monday. Even if that does not occur, the expected northeast fetch 
might increase rip currents again by Wednesday. 


&& 


Phi watches/warnings/advisories... 
PA...none. 
New Jersey...none. 
Delaware...none. 
Maryland...none. 
Marine...Small Craft Advisory until 11 am EDT this morning for 
anz450>455. 


&& 


$$ 


Synopsis...stauber 
near term...stauber 
short term...stauber 
long term...stauber 
aviation... 
marine... 
rip currents...