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fxus61 kakq 211511 
afdakq 


Area forecast discussion 
National Weather Service Wakefield Virginia 
1111 am EDT sun Mar 21 2010 


Synopsis... 
high pressure remains centered off the middle Atlantic coast today. 
Low pressure tracks across the Ohio Valley tonight and Monday. The 
trailing cold front crosses the Middle Atlantic States late Monday 
afternoon. Another front moves through late Tuesday...with high 
pressure building back in on Wednesday. 


&& 


Near term /until 6 PM this evening/... 
latest surface analysis showing pressure rises just off the southern Virginia coast...with 
strong low pressure centered across the lower MS valley. Cirrus shield 
slowly advecting northeastward...but thicker middle level clouds are currently 
confined to southern NC. For the afternoon...expect increasing clouds mainly 
over far SW sections of the County Warning Area...where this may cause temperatures to 
become steady around 70/in the lower 70s after about 2 PM. 
Elsewhere...think the incrsg clouds will be too late to have much 
affect on high temperatures...gnly into the middle 70s over much of central 
and eastern Virginia. With a moderate south-southwest flow this afternoon across the akq County Warning Area...have 
raised high temperatures into the lower 70s even at Norfolk/Virginia Beach...although 
may see some turning of the winds to south-southeast later in the afternoon..which 
would drop temperatures a few degrees along the immediate coast. 


&& 


Short term /6 PM this evening through Tuesday/... 
skies quickly become cloudy this evening ahead of apprchg systm from the 
SW. 00z data continues to sprt precipitation holding off until aftr midnite over 
western counties. Showers ovrsprd forecast area from SW-NE aftr 06z due to combo of 
increasing moisture & southeasterly wind flow. Offshore ridge may keep most of lower 
Delaware-Maryland-Virginia dry through sunrise Monday. Lows 50-55. 


Low prs moves across Kentucky and into West Virginia Monday morning then continues into western 
PA by evening. Southeasterly ll jet combines with decent lift to produce a 6-8 
hour prd of steady precipitation Monday am along and ahead of occulded frontal boundary. 
Models continue to forecast some weak instability aloft with the frontal zone... 
so thunder is psble with the primary rain band. Based on latest data 
not looking for any severe threat given time of day...but some gusty 
winds are possible given the prognosticated instability and shear. 


Best lift & instability (along with the frontal bndry) lifts NE into Northern 
Neck & Eastern Shore areas drng Monday afternoon. Data suggests dry punch of 
air from the SW dmnshs precipitation chances aftr 20z or so across southwestern counties. 
Will keep skies M cloudy for now...but would not be surprised to see 
some prtl sunshine mainly S of i64 late Monday afternoon. Highs in the 
M-u60s...near 70 southwestern counties given any sun. Quantitative precipitation forecast bwtn 1/2 to 3/4 in. 


Upper low drifts across the region Monday night b4 liftg off the New Jersey 
coast Tuesday. Precipitation chances quickly dmnsh across Eastern Shore areas drng the 
evening as systm continues to move NE. Otw...kept low chance probability of precipitation drng this 
time frame given the cold pool aloft. Lows Monday night 40-45. Highs 
Tuesday tricky depending on amount of cloud cover. U50s along the coast 
to l60s west of ches Bay. 


&& 


Long term /Tuesday night through Saturday/... 
vertically-stacked low pressure moving off the Atlantic coast Tuesday night 
will give way dry and seasonably mild conditions on Wednesday as flat upper 
ridging builds into the middle Atlantic region. The GFS is a little faster 
with the northwest-southeast progression of the northern stream jet axis/shortwave 
trough well north of the forecast area. It is this feature aloft which will 
eventually drop a surface backdoor front southward through the region 
(wed night per both the ECMWF/gfs)...before that happens expect 
temperatures to rebound well into the 60s (some lower 70s) over interior 
portions of the region on Wednesday...with cooler temperatures near the coast. A 
little cooler on Tuesday behind initial (weak) backdoor front...albeit 
mainly eastern portions toward the coasts as the temperatures aloft remain very 
similar. 


Conditioned with the mention of rain beginning on Friday...as both the 
GFS/European model (ecmwf) show another backdoor front pushing into the region...with 
this feature serving as an anafront late Friday/early Sat as a southern 
stream wave moves across the Lower Middle Atlantic region. Cooler temperatures 
Friday/Sat as a result of the likelihood of increased clouds/rain chances. 


&& 


Aviation /15z Sunday through Thursday/... 
VFR conditions will persist for anthr taf cycle before restrictions 
develop twrds daybreak Monday. 


A large band of rain showers/thunderstorms and rain showers will works its way SW/NE through the 
region Monday morning into early afternoon. Dry slot at middle levels will shut 
chances of precipitation off over SW County Warning Area...with lingering chances of rain showers over 
the Northern Neck into the Eastern Shore late day. However...MVFR/IFR ceilings 
look to remain low along the coastal third...but could see enough 
dry air to allow for VFR conditions over central VA/NC. 


Another issue Monday am will be wind direction and potential for maximum 
Crosswinds over southeast Virginia/NE NC Monday am. Guidance showing winds at the 
surface to be out of the southeast (140-160 degrees) 10-20z Monday and 
eventually out of the south late afternoon/early evening. Low level jet moves 
over the region at that time with winds of 35-45 kts at 1-2k feet. 


Upper level low moves over the region Tuesday with MVFR ceilings developing...with 
chances for late am/PM rain showers activity (esp north central Virginia/Maryland eastern 
shore). Winds shift to the northwest Tuesday night into Wednesday which could make 
for crosswind issues once again for phf/orf. 


&& 


Marine... 
look for a S/southeast flow today over the waters...winds gnrly at or below 15 kts. 


Raised flags for Monday over the Bay/coastal waters as S/southeast flow 
increases ahead of an approaching low pressure system. Look for 
building seas over the coastal waters before seas relax over the southern 
waters Tuesday am and hold near 5 feet outer fringes far north till Tuesday 
evening. This low will eventually push offshore Tuesday night and into Wednesday. 
Could see a brief period of low-end gales Tuesday night (nw flow) and 
early Wednesday (mainly northern half of Bay/coastal waters). High pressure builds 
into the region through Thursday before next frontal system pushes into the 
region from the northwest on Friday. 


&& 


Akq watches/warnings/advisories... 
Maryland...none. 
NC...none. 
Virginia...none. 
Marine...Small Craft Advisory from 7 am Monday to 1 am EDT Tuesday for 
anz630>632-656-658. 
Small Craft Advisory from 7 am Monday to 7 PM EDT Tuesday for 
anz650-652-654. 


&& 


$$ 
Synopsis...lkb 
near term...lkb 
short term...mpr 
long term...bkh 
aviation...ccw 
marine...ccw 

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