388 
fxus61 kakq 181954 
afdakq 


Area forecast discussion 
National Weather Service Wakefield Virginia 
354 PM EDT Thursday Mar 18 2010 


Synopsis... 
high pressure will prevail over the middle Atlantic through Sunday 
bringing mild and dry conditions. Low pressure will arrive from the 
southwest Sunday night and Monday. 


&& 


Near term /until 6 am Friday morning/... 
an upper low off the southeast coast this afternoon will slowly 
drift east tonight is response to falling heights over the upper 
Midwest. High clouds will steadily dissipate from northwest to 
southeast overnight as an upper ridge builds in from the west. 
Morning low temperatures will be seasonally cool with readings 
ranging from the middle 30s to low 40s. 


&& 


Short term /6 am Friday morning through Sunday/... 
upper ridging will continue to prevail over the middle Atlantic region 
through Saturday night. Temperatures will range from near 70 along 
the coast to the low and middle 70s inland under full sun Friday...and 
then warm a few more degrees Saturday. The biggest challenge of 
Friday and Saturday will continue to be minimum dewpoints during the 
afternoon. Values at present...Thursday afternoon are ranging from 
the upper teens and low 20s in the western zones to the low 30s 
along the coast. It is likely that similar dewpoint depressions will 
continue the next two days. This will keep minimum relative humidity 
values rather low...but minimal wind should preclude any fire 
weather concerns. 


An upper low will drop over the lower Mississippi Valley Saturday 
night and Sunday. The upper flow shifts to southwest...which will 
allow moisture to increase. Mild temperatures will continue Sunday 
as the upper ridge axis will linger over the middle Atlantic region. 
Any rain showers will arrive at earliest late Sunday afternoon...but 
most likely not until Sunday night. 


&& 


Long term /Sunday night through Thursday/... 
the extended forecast period will begin unsettled Sun night through at 
least Monday morning...as we see our best chances for a period of rain 
asscd with the northwest-southeast oriented warm/occluded front. Have boosted probability of precipitation 
above 50% during this period...earlier (late sun night) across western 
portions and later (after daybreak mon) over the east. By afternoon...GFS and 
European model (ecmwf) are similar with the depiction of deep...broad dry slotting 
spreading through the forecast region from the SW...as the surface low 
tracks across northern Virginia. Thus have lowered probability of precipitation from SW-NE for Monday 
afternoon...as despite the dry slotting (which in the lower layers would be 
aided by a developing SW or downslope flow)...cannot rule out the 
possibility of convectively-induced showers and/or thunderstorms with the 
daytime heating. As for temperatures...leaned toward an HPC-mex guidance 
blend...I.E. 65-70 for most...which would be predicated on at least 
partial sunshine within the narrow (and departing) warm sector. Even 
with the ensuing cold air advection aloft Monday afternoon...developing SW (donwsloping) 
low level flow will offset and allow for the mild conditions. 




Tuesday...included minimal chances for showers over the northern portions of the 
forecast area asscd with the passage of the middle level low...I.E. Where 
DPVA is most favorable for at least isolated development despite the deep 
SW-west low level flow. Temperatures a bit cooler than Monday...yet still quite mild/ 
seasonable (60-65 for most...cooler along the coasts). 


Wednesday-Thursday relatively uneventful in comparison...at least in terms of 
probability of precipitation. Have maintained dry weather during this time as deep layer ridging 
holds serve across the region (ahead of the next front which would 
most likely not affect the forecast area until Friday at the earliest). 
Temperatures again seasonably mild...60s to lower 70s across the region 
(coolest along the lower eastern shore). 


&& 


Aviation /20z Thursday through Tuesday/... 
VFR conditions should persist through the upcoming taf 
cycle...with mainly middle/high clouds at or above 12kft. Have allowed for 
some scattered middle clouds at kphf-korf-kecg through the evening in 
association with low pressure off the southeast coast. 


Next chance of flight restrictions/precipitation comes early Monday morning with 
a very quick moving cold front. Some scattered precipitation/short lived MVFR 
conds possible. A more extended period of MVFR/IFR possible on 
Monday night/Tuesday morning as next upper low pressure system 
crosses the region. 


&& 


Marine... 
low prs moving NE along the Carolina coast will maintain the stronger 
NE flow and higher NE swells across the southern waters tonight through Friday. 
Seas across northern coastal waters prognosticated to slowly fall below 5 feet by late 
this evening or around midnight. Seas stay at or above 5 feet across southern waters through 
Friday due to lingering NE swells at or above 5 feet. 


Conditions through the weekend be marked by sub-Small Craft Advisory conditions 
across all waters as high pressure dominates...with winds generally 
10-15 kts or less and wave heights < 4ft. 


&& 


Akq watches/warnings/advisories... 
Maryland...none. 
NC...none. 
Virginia...none. 
Marine...Small Craft Advisory until 2 am EDT Friday for anz650-652-654. 
Small Craft Advisory until 6 PM EDT Friday for anz656-658. 


&& 


$$ 
Synopsis...ajz 
near term...ajz 
short term...ajz 
long term...bkh 
aviation...mam 
marine...bkh