307 
fxus61 kakq 040819 
afdakq 


Area forecast discussion 
National Weather Service Wakefield Virginia 
319 am EST Thursday Dec 4 2008 


Synopsis... 
high pressure remains centered off the middle Atlantic coast this 
morning. A cold front will cross the area Thursday afternoon and 
evening...with high pressure building back over the middle Atlantic 
region Friday into the weekend. 


&& 


Near term /through today/... 
hi level cloudiness will continue to spread across forecast area this mrng/midday...b4 middle level 
cloudiness arrives by this evening as a cold front enters from the northwest. Low level flow 
from the SW...resulting in moderate blyr warming. 850 mb temperatures rise above +6 degrees 
c by this afternoon. Xpctg hi temperatures from the m50s across the far northern sections 
of forecast area...to the l60s southeast. Will continue west/ only slight chance probability of precipitation across far northwest 
areas of forecast area this afternoon as middle level forcing/fgen weaken. 


&& 


Short term /tonight through Saturday/... 
frontal boundary settles S to near the southeast Continental U.S. CST overnight. GFS pushes axis 
of moisture southeast through the forecast area...lingering in vicinity of extreme southeast Virginia and NE NC 
through Friday morning. Tsxns showing moisture generally at or below 700 mb mb and uvm weak. Will 
keep mention of slight chance probability of precipitation. Limited clearing west/ cold air advection on Friday...as flow below 
900mb largely northerly. Sharping of trough aloft through the Midwest Friday 
night/Sat morning...then to the east CST lt Sat...resulting in p/mcldy 
conds. 


Low temperatures tonight mainly in the 30s...hi temperatures on Friday in the 40s. Remaining 
seasonably cold Friday night (lows in the 20s to m30s)...and Sat (hi 
temperatures again in the 40s). 


&& 


Long term /Saturday night through Wednesday/... 
clipper type systm prognosticated to eject quickly southeast in eastern trough Sat night. 
The projected track of systm (n of Mason-Dixon line) would not nrmlly 
produce much in the way of sgnfcnt precipitation across forecast area. However...latest 
GFS/European model (ecmwf) both indct enough moisture along trailing trough to produce a several 
hour prd of precipitation across region. Thus...have incrsd probability of precipitation Sat night into chance 
Cat with the highest probability of precipitation across the north and lowest across the S. Next 
concern is p-type as ll thnckns sprt a snow or rain to snow scenario 
across the northern 2/3rds of the forecast area. Lows in the u20s north to m30s southeastern CST. 


Lingering snow showers across lower Maryland Eastern Shore sun am b4 anthr cold 
prd expeceted Sun afternoon through Tuesday as anthr in a series of Canadian high 
prs builds into region. Below normal temperatures continue with highs sun and Monday in 
the 40s and lows 20-30 (upr teens in nrmly cold spots). 


Return flow returns Tuesday as 500 mb ridge moves offshore. 850 mb temperatures rise to 
sprt readings to between 50-55. Next systm ejects NE from Gulf states 
late Tuesday then moves NE along applach mts. Moisture with this systm 
prognosticated to quickly move north and ovrsprd region by middle week. Appears that 
enough warm air is drawn north to keep this event all liquid at this time. Lows Tuesday 
night 40-45 and highs Wednesday u40s-l50s. Trailing cdfrnt moves offshore 
by Thursday night allowing anthr cold airmass to build in by next Friday. 


&& 


Aviation /08z Thursday through Monday/... 
VFR conditions to continue today as high pressure moves offshore of 
the mid-Atlantic. SW winds will increase ahead of an approaching 
cold front with gusts to 20 knots possible this afternoon. The front 
will move across the region this evening into early Friday. Moisture 
ahead of the front remains limited and only expect very light 
rain/sprinkles with frontal passage. Model soundings continue to show an 
increase in low level moisture and a period of MVFR ceilings tonight into 
Friday as the front stalls out over southeast Virginia/NE NC. 


High pressure and VFR conditions return late Friday through early Sat. The 
next frontal system moves across the region late Sat through early sun 
bringing increasing cloud cover and a chance of precipitation. High 
pressure then builds back in late sun through Monday. 


&& 


Marine... 
the pressure gradient between high pressure east of the waters and low pressure 
over the lower Great Lakes has tightened...with a resultant increase 
in surface winds. Latest observations report gusts to around 20 knots 
across the ches Bay where a Small Craft Advisory remains in effect through this afternoon. 
Meanwhile ndbc buoy 44009 is already reporting seas around 6 feet and have 
accordingly commenced the Small Craft Advisory from Fenwick Island Delaware S to Parramore 
Island Virginia with the early am forecast issuance. Winds and seas will also 
increase farther to the S over the next several hours...and will 
begin a Small Craft Advisory from Parramore Island Virginia S to the Virginia/NC border later 
this am. 


Winds will briefly ease this evening as the gradient weakens. A surface 
cold front will cross the waters tonight and models continue to show 
increasing northwest winds with cold air advection behind the front. Small Craft Advisory 
flags will likely need to be issued for this next wind event late 
tonight into early Friday. High pressure then builds in across the waters 
from the SW during the day Friday into Sat. An area of low pressure will 
then move across the region from the northwest late Sat into sun with a 
round of high end Small Craft Advisory conditions expected sun into Monday. 


&& 


Akq watches/warnings/advisories... 
Maryland...none. 
NC...none. 
Virginia...none. 
Marine...Small Craft Advisory until 6 PM EST this afternoon for 
anz630>632-650-652. 
Small Craft Advisory from 10 am this morning to 6 PM EST this 
afternoon for anz633. 
Small Craft Advisory from 7 am this morning to 6 PM EST this 
afternoon for anz654-656. 


&& 


$$ 
Synopsis...alb 
near term...alb 
short term...alb 
long term...mpr 
aviation...jrl 
marine...jrl 

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