416 
fxus61 kakq 210512 
afdakq 


Area forecast discussion 
National Weather Service Wakefield Virginia 
1212 am EST Sat Nov 21 2009 


Synopsis... 
high pressure settles over the area tonight and lingers through 
Saturday night. The an area of low pressure moves through the Gulf 
Coast and up the eastern Seaboard from late Sunday through Monday 
night. High pressure builds down the eastern Seaboard on Tuesday 
into Wednesday. 


&& 


Near term /through today/... 
latest weather analysis depicts surface high pressure over the Midwest 
this evening. To the south...developing low pressure noted over 
the western/central Gulf coasts this evening in assn with 
middle/upper level low over west central Texas. Some cirrus associated 
with this feature getting shoved downstream...riding SW flow aloft 
already pushing across the middle-south and Carolina Piedmont...as 
noted on early evening infrared/ramsdis WV imagery. Will likely see these 
high clouds continue to make inroads across the western half of 
the area into the overnight hours. 


Otherwise...surface high pressure settles over the region overnight 
and begins to slide off to the NE on Saturday. Should see mainly 
clear conditions over the eastern County Warning Area. However...with the aforementioned 
SW flow aloft ahead of the next system...should begin to see 
cirrus across the western...and eventually the central County Warning Area 
overnight. Stayed close to inherited temperatures...and still should see 
good radiative conditions. Early morning lows in the middle 30s to the 
near 40...with the potential for some l30s well north/northwest of ric. 


Saturday... 
should see decent warming for Saturday. Have gone with the warmer 
mav guidance...although the thicken clouds could hold temperatures down a 
degree or two mainly in west/SW parts of the County Warning Area. Seasonable highs in 
the l60s for most zones...upper 50s over the eastern shr. 


&& 


Short term /tonight through Monday/... 
active period begins on Sunday into Monday...but the models are 
not in very good agreement. The GFS seems to be too strong and too 
fast with the system and is generally the only model showing this 
strong of a system. The NAM/Canadian seem to be the middle of the 
Road with the clouds increasing on Sunday with the bulk of the 
overrunning precipitation on Sunday night through Monday. The 12z European model (ecmwf) is 
even slower...and has trended slower from the 00z run. For now 
have gone toward the middle of the guidance...increasing clouds 
and bringing some low probability of precipitation in late Sunday but focusing probability of precipitation and 
quantitative precipitation forecast on Sunday night into Monday. Hesitant to be too slow as 
overrunning is often faster than what the models indicate. 


For temperatures...have gone closer to the met on Sunday for 
highs...but not as warm given the increasing clouds. For Sunday 
night did lean a little milder given the expected increase in 
moisture. Have lowered highs on Monday given the expected clouds 
and lingering rain. The mex numbers look too warm on Monday...but 
given the speed of the GFS solution...it is understandable they 
would be warmer. 


&& 


Long term /Monday night through Friday/... 
low confidence forecast for this period as GFS/NAM/ECMWF showing 
rather large differences even in the short term...so evolution of 
next system later in the week very uncertain. Will keep chance probability of precipitation 
in the forecast Monday night as NE flow continues with surface high off the 
New England coast...and at least a wave of low pressure off the 
middle Atlantic/southeast coast (outlier GFS solution gnly disregarded). For 
Tue/Wed...ridging develops either along the East Coast (ecmwf) or 
well off the coast (gfs). Gnly keeping skies partly cloudy for this 
period with near to slightly above average temperatures...highs into lower 60s 
and lows mainly in the 40s. As the ridge breaks down on 
Thanksgiving day...GFS/ECMWF bring next system into the area from 
the south (although again west/ major differences in track). Bring 
increasing clouds into the forecast...along with at least a slight chance 
for showers. Front looks to push through by Friday...drier and cooler 
weather for Friday. 


&& 


Aviation /06z Saturday through Wednesday/... 
VFR cndtns expeceted through forecast prd xcpt for some MVFR cndtns through 12z 
in patchy fog. Went ahead with a bkn250 forecast vice sky clear as Sat loop 
alrdy indctg plnty of cirrus apprchg from SW. 


Low apprchs from S by late sun with next chance for lower ceilings and chance 
for rain into Monday. The weather improves again by Tuesday. 


&& 


Marine... 
continue Small Craft Advisory for NC coastal waters from Virginia/NC border to curr beach light until 6 
am Sat as NE winds keeps seas around 5 feet. 


Surface high moves off to the NE...and a wave of low prs apprchs from 
the S on sun. GFS solution looks too fast and have disregarded the 
southerly flow regime it depicts on Monday (keeping winds NE on 
Monday/Monday night per NAM/UKMET/ECMWF consensus). This consensus solution 
places the surface high in a favorable position for Small Craft Advisory conditions 
later Sunday through Monday (over new england) and have gone close 
to previous forecast (higher than the models for wind speeds). For 
seas...gnly went 5-6 feet for now on the coast (gfs solution yields a 
wavewatch forecast for only 4-5 feet south and 6-7 feet north). 


&& 


Akq watches/warnings/advisories... 
Maryland...none. 
NC...none. 
Virginia...none. 
Marine...Small Craft Advisory until 6 am EST early this morning for 
anz658. 


&& 


$$ 
Synopsis...ess/mam 
near term...ess/mam 
short term...ess 
long term...lkb 
aviation...mpr 
marine...lkb/mpr