Weather

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afdakq 


Area forecast discussion 
National Weather Service Wakefield Virginia 
738 PM EDT Thursday Aug 21 2008 


Synopsis... 
high pressure centered to our north will move offshore of New 
England tonight...and will then hold in place through the weekend. 
A cold front will attempt to move through the region early next week. 


&& 


Near term /until 2 am Friday morning/... 
high pressure remains centered to our north over upstate 
New York...while ts Fay is well to our south centered near Flagler 
Beach Florida. Meanwhile the middle Atlantic is sandwiched in between 
these two areas...with moderate onshore flow continuing. The 
majority of the cloud cover today has been confined to the Virginia 
Piedmont and southern Appalachians where upslope flow has enhanced 
cumulus development. Overall...our airmass is even more stable today 
compared to this time yesterday...with drier air in place over southeast 
Virginia/NE NC where dew points have dropped into the upper 50s at orf and 
other nearby locations. Thus do not expect any precipitation tonight. Low 
temperatures will range from the upper 50s over northwest portions...to near 70 
over southeast Virginia/NE NC (except lower 50s in vicinity of sby). 


&& 


Short term /2 am Friday morning through Sunday/... 
the high will slide offshore of New England by early Friday 
morning...and will then remain centered just south of Nova 
Scotia through the first half of the weekend. Onshore flow will 
persist through early Sunday...and high temperatures will remain quite 
comfortable...lower to middle 80s on both Friday and Saturday. Low 
temperatures will range from 60 in the west to 70 in the east. 


The high begins to lift off to the NE and away from the coast of 
New England as an upper level trough and associated surface front 
approach the region from the northwest. The onshore flow will 
weaken...and winds will start to become southeast/S by late Sunday. As 
a result high temperatures will be warmer on Sunday (85 to 90)...with 
low temperatures in the lower 60s in the Piedmont up to lower 70s at the beaches. 


Low level moisture will begin to increase on Sunday...although with no 
prominent forcing mechanisms in place will keep the forecast dry through 
Sunday for now. 


&& 


Long term /Sunday night through Thursday/... 
GFS/European model (ecmwf) have slowed down with progression of the next cold 
front...therefore have removed precipitation mention Sun night and only have 
a slight chance (20%) coming into the region by Monday afternoon. With the 
slower timing...light southerly flow looks to keep temperatures very warm on 
Monday...with highs into lower 90s interior and upper 80s along the coast 
and in northern zones. 


For Tuesday into Thursday...eventual track of moisture associated with Fay (or 
remnants) will be the main feature affecting our weather. 12z runs 
of European model (ecmwf) and GFS are similar but with the GFS farther east (and 
therefore more optimistic for precipitation). If the European model (ecmwf) verifies 
would expect to see bulk of moisture remaining to our west across the 
Appalachians or perhaps even west of the mountains have gnly split the 
difference for now...with best chances for precipitation west of I-95 in 
the Piedmont (30-40%)...and lowest chances over the Eastern Shore 
(20%). Easterly flow and partly to mcdy skies will keep high temperatures in 
the 80s. 


For the latest information regarding the tropics...please refer to 
the forecasts and discussions issued by the Tropical Prediction 
Center. 


&& 


Aviation /00z Friday through Tuesday/... 
mostly clear skies cover the taf sites at 23z. Easterly winds will 
continue through Friday and beyond but dry conditions aloft and some 
subsidence should keep low clouds from becoming more than scattered. Fog 
is expected at sby but duration should be shorter than this morning 
when dew points dropped to 10 degrees below the previous evening 
readings. That number should be about 5 degrees Friday morning. The 
current taf has them down to 2 miles by 07z but it may go briefly 
LIFR and that will be considered with the next issuance. Mainly 
VFR conditions are expected for the next few days. Morning fog and 
haze and widely scattered precipitation is expected by early next week. 


&& 


Marine... 
with strong surface high anchored from New England southward to off the 
middle Atlantic coast...and Fay still over Florida...marine area will 
continue to see easterly flow regime tonight through Saturday. Winds 
have gnly been 10 to 15 kts with an occasional gust just under 20 
kts. Expect little change in these conditions over the next 24 
hours...winds on Sat look to be a bit lighter as the gradient weakens 
slightly. However...as swell becomes more dominant by Sat waves 
should increase some...near 5 feet for southern coastal waters. 


Flow gradually veers to more of a southeast to south direction later Sunday 
into Monday ahead of an approaching cold front....but wind speeds 
remain under Small Craft Advisory thresholds. Lots of uncertainty into next week as 
front stalls somewhere in southern Virginia or Carolinas west/ remnants of Fay 
tracking to our west. 


At this point...sensors and forecasts do not depict any significant 
tidal departures but will continue to monitor closely. Expect at 
least a moderate risk for rip currents Friday and Sat as onshore flow 
persists. 


&& 


Akq watches/warnings/advisories... 
Maryland...none. 
NC...none. 
Virginia...none. 
Marine...none. 


&& 


$$ 
Synopsis...jrl 
near term...jrl 
short term...jrl 
long term...lkb 
aviation...lsa 
marine...lkb