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Area forecast discussion 
National Weather Service Wakefield Virginia 
1041 PM EDT Wednesday Mar 17 2010 


Synopsis... 
high pressure will settle over the area tonight through 
Thursday...as a weak low pressure system develops off the 
southeast coast. High pressure then becomes centered over the 
Carolinas Friday and Saturday...bringing dry and warm weather to 
the middle Atlantic. A cold front will push through the region late 
Sunday into Monday. 


&& 


Near term /until 8 am Thursday morning/... 
upper low over the southeastern US with surface low developing off the coast 
will throw middle to high level moisture northward across NC and Virginia. 
This upper low will be slow to move over the next 24 to 36 hours 
before exiting to the east on Friday. As a result...have increased 
the sky cover for tonight. But the low levels remain dry so any 
rain should remain to the south. Also...as a result of the 
increased clouds...temperatures should be a couple of degrees 
warmer than last night which had much better radiational cooling conditions. 


&& 


Short term /8 am Thursday morning through Saturday/... 
low pressure tracks slowly NE in vicinity of Gulf Stream Thursday into Thursday night...b4 moving 
out to sea on Friday. Otherwise...surface hi pressure to remain near the forecast area. Still 
xpctg broken cloudiness as far north as southern Virginia/NE NC through Thursday night (ra to remain 
south-southeast of fa)....b4 clearing trend takes over early Friday. Friday/Sat will be warm 
(for middle/lt Mar...and especially inland) - normal hi temperatures u50s/around 60u 
degrees f - as surface hi pressure slides from over the forecast area...to offshr...which 
(eventually) results in a return flow from the south-southwest. Hi temperatures Thursday/Friday 
from around 60 near the CST...to u60s/l-m70s farther inland. Wdsrpd hi 
temperatures into the 70s xcptd on Sat (though 60s at the cst). Ngttm 
rdgs falling into the u30s/l40s both Thursday night/Friday night. 


&& 


Long term /Saturday night through Wednesday/... 
medium range period characterized by quick moving cold front Sunday 
night...with high pressure quickly building back and allowing for 
near/just above climatology temperatures through the period. 


Long term forecast period begins with upper ridging in place over the 
mid-Atlantic. To the west...strong short wave trough will be diving across 
the central/Southern Plains Saturday night/early Sunday...taking on a 
slightly negative tilt as it pushes a surface cold front across the Tennessee 
Valley/Gulf Coast region on Sunday. Have trended towards the European model (ecmwf) 
solution...which is a bit farther south and slower than the GFS 
(which makes sense considering the more amplified setup). 


Accordingly...have lowered cloud cover a bit early Sunday and 
continued to shunt chances on precipitation back Sunday aftn/evening. Have kept 
probability of precipitation at slight or less before middle afternoon...which better chances coming 
late afternoon or during the evening west/ the front. Given slower frontal 
passage timing...not expecting convective chances to be too high so have 
pulled thunder wording for now. Otw...bkn-sct line of rain showers comes 
through Sunday night...with lingering slight rain chances continuing 
into Monday morning over the eastern County Warning Area. More sun should allow for 
another mainly dry and pleasant day on Sunday...with highs again in 
the 70s. 


Extended period of high pressure/upper ridging then quickly build in 
behind the front for early next week...with downslope (w) flow aloft 
allowing for mainly dry weather through the period and temperatures 
recovering to near/just above normal by midweek. Look for highs 
generally in the 50s and 60s Monday and Tuesday...recovering into 
the M/u60s to near 70 (and potentially higher) by Wednesday. Seasonable 
early morning lows generally in the 30s to near 40. 


&& 


Aviation /03z Thursday through Monday/... 
VFR ufn as high prs builds into the region. High level cloudiness from southern 
systm starting to move into southern forecast area at this time...but all 
sites remain VFR into Thursday. 


The next weather system may bring precipitation and MVFR/IFR conds late sun. 


&& 


Marine... 
generally benign conds weather wise over the waters as high pressure in 
place dominates weather across the region. Light flow continues tonight... 
becoming north-northeast tomorrow and tomorrow night before veering to the S by 
later Friday/Sat as the high pressure moves offshore. Low pressure drifting away 
from region prognosticated by both the Swan & wavewatch to keep long period 
easterly swell up through the next 24 hours or so. Small Craft Advisory for hazard seas will 
remain in place through Thursday afternoon...and may need to extend out a bit 
farther for southern coastal zones. 


Otherwise...a cold front will approach from the west later 
sun/Monday...with prefrontal S flow turning west-northwest behind the front for 
Monday/Tuesday. 


&& 


Tides/coastal flooding... 
positive anomalies now down to about 0.5 feet or less above 
normal...with the highest of these very minor departures in northern 
central Bay zones. This shouldn't result in any flooding 
issues...but will note these minor anomalies in updated coastal waters forecast this 
afternoon over Bay zones. 


&& 


Akq watches/warnings/advisories... 
Maryland...none. 
NC...none. 
Virginia...none. 
Marine...Small Craft Advisory for hazardous seas until 4 PM EDT 
Thursday for anz650-652-654-656-658. 


&& 


$$ 
Synopsis...alb/lkb 
near term...ess 
short term...alb 
long term...mam 
aviation...als 
marine...mam 
tides/coastal flooding...