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Next 12 Hours

Forecast data from the National Digital Forecast Database.

5 Day Forecast

• Sunday
• 
• High: 86 °
• Low: 68 °
• T-Storms

• Monday
• 
• High: 84 °
• Low: 72 °
• Chance of T-Storms

• Tuesday
• 
• High: 91 °
• Low: 70 °
• Chance of T-Storms

• Wednesday
• 
• High: 93 °
• Low: 70 °
• Partly Cloudy

• Thursday
• 
• High: 91 °
• Low: 73 °
• Chance of T-Storms

Area forecast discussion 
National Weather Service Wakefield Virginia 
424 am EDT sun may 19 2013 


Synopsis... 
a weak front remains nearly stationary over North Carolina this 
morning. This front is expected to lift to the north today...and 
move north of the region by Monday afternoon. A ridge of high 
pressure off the southeast coast will prevail into the middle of 
the week. 


&& 


Near term /until 6 PM this evening/... 
latest water vapor imagery continues to show stubborn upper low 
over western Kentucky with a rather broad middle/upper level trough situated 
from Kentucky down into the Carolinas. At the surface...stationary 
front/boundary still located over northern NC. Area of showers and 
embedded thunderstorms developed along the boundary in north central NC 
earlier this morning...but have since weakened as they moved north 
into the region. Cloud tops have warmed...but a few shallow 
showers ongoing over the Eastern Shore...aided by middle level 
energy/shortwave. RUC 700 mb Omega handles this area of showers 
well...with the showers pushing offshore in the next few hours. In 
addition...very moist boundary layer...warm air advection and calm winds have 
resulted in areas of fog this morning...with some visibilities as 
low as half a mile in the Richmond area. 


Additional weak impulses will eject eastward from the dying upper low 
into a warm/moist airmass...with the first arriving later this 
morning. Cooling cloud tops already observed this morning over western 
NC. Precipitation waters still around 1.5 inches (+1 Standard dev). Expect 
showers to increase in coverage across the eastern Virginia Piedmont by middle 
morning. For this afternoon...weakening upper low will remain in 
the vicinity of western Kentucky as the boundary begins to lift northward as a 
warm front. Shortwave will lift through Virginia...combining with weak 
divergence aloft to provide forcing for ascent...albeit weak. 
However...with abundant moisture in place...it will be enough to 
trigger additional showers this afternoon...mainly across the 
Piedmont into central Virginia. Instability will be limited...but good low 
level lapse rates and Theta-E advection will be enough for 
scattered afternoon thunderstorms....mainly across southern Virginia. S/southeast 
flow will limit the amount of instability along the coast and over 
the Eastern Shore. Middle level wind fields are rather weak...so the 
main threat from thunderstorms will be heavy rain. 


Another cloudy/wet day will prevent temperatures from reaching their full 
potential...with highs generally in the middle/upper 70s. Colder 
along the immediate coast and over the Eastern Shore. 


&& 


Short term /6 PM this evening through Tuesday/... 
remnants of the upper low will eject over the Appalachians Sunday 
night into Monday as a potent upper trough reaches the Midwest. At 
the surface...warm front will locate north of the forecast area Monday afternoon 
as high pressure located over the western Atlantic extends westward into 
the Lower Middle Atlantic and southeast states. Warm/moist airmass will 
build in as S/SW flow advects deep moist from the Atlantic...with 
precipitation water values approaching +1.5 Standard dev. Weak shortwave and 
divergence aloft will provide subtle forcing for ascent...but 
expect most forcing and resultant convection to be diurnally 
driven. While Theta-E advection and warm temperatures will provide 
marginal instability (500-1000 j/kg cape)...a weakening middle level 
wind field will provide limited shear. The result will be 
scattered thunderstorms with very little organization. The 
shortwave axis prognosticated to be around the eastern Virginia Piedmont...with the 
best chances for showers/thunderstorms being to the east of the 
axis over central and eastern Virginia. 


Trough axis will locate along the coast Tuesday as the central Continental U.S. 
Trough amplifies the upper ridge over the east. Residual moisture 
and subtle uvm will be sufficient for showers along the coast 
Tuesday afternoon. Dewpoints in the middle 60s and afternoon temperatures in 
the low/middle 80s will result in greater instability (~1500 j/kg 
cape and ~-6 lifted index) for convection/thunderstorms. Forcing 
will be mostly diurnally driven. However...shear remains weak so 
expect no organized thunderstorms. 


Near seasonable normal temperatures Monday (upper 70s/low 80s) before a 
warming trend Tuesday. Increasing heights/thicknesses...as well as 
850 temperatures approaching +1 Standard dev...will result in temperatures generally 
in the middle 80s. 




&& 


Long term /Tuesday night through Saturday/... 
models similar over this time period with the timing of another trough 
deeping at 500 mb toward Friday and Saturday. This will usher a 
stronger cold front through the region Friday into Saturday. The 
front will have some showers and thunderstorms with it as it moves 
through. Before that a frontal boundary remains nearly stationary 
across the Great Lakes and New England. South of this area will have 
general south to southwest flow across the area. Could see an 
isolated afternoon thunderstorm. Any thunderstorms that form north 
along the boundary could push into the northern part of the area 
during the evenings. Temperatures will be at or above normal until 
the front passes. Then temperatures will drop back on Saturday to at 
or below normal. 


&& 


Aviation /08z Sunday through Thursday/... 
aviation conditions next 12 hours or so appear to be split between 
MVFR/VFR at kphf/kecg/korf and mainly IFR at kric/ksby. Looks like 
kric will remain IFR/LIFR through at least 12z in pre-warm frontal 
airmass with scattered shwrs/fog/dz. Ksby...based upon observations 
last 1-2 hours...will likely oscillate between IFR and 
MVFR...although IFR will dominate in the 09z-14z time frame. The 
other 3 tafs should be mainly VFR/MVFR...although a heavier 
shower/thunderstorm could briefly bring conditions down to IFR. With 
little forcing through 20z...do not expect a lot of shower/thunderstorm 
activity at korf/kphf/kecg. 


Latest NAM suggests that precipitation focus will shift to the north and 
west as warm front lifts northward ahead of weakening upper trough from 
the Tennessee Valley. This should limit precipitation coverage at terminals in the 
12z-00z time frame...although scattered showers/isolated thunderstorm possible at ksby 
through 18z...and at kric after 21z. 


Region in warm sector Monday through Wednesday with scattered...more 
diurnal...shwr/tstm activity...but mainly VFR/MVFR conditions. 


&& 


Marine... 
east/southeast winds prevail across the marins area this morning...with speeds 
below Small Craft Advisory criteria everywhere. Wind expected to gradually turn to 
the south all areas as the day progresses...and warm front lifts northward 
through region. Winds generally 10-15kt on the 
Bay/rivers/sound...and 10-20 knots on the ocean /highest north of Cape 
Charles Light/. These conditions expected to persist next 2-3 
days...before winds become south-southwesterly/southwesterly in the Tuesday time frame. 


Biggest forecast concern this morning is seas on the coastal waters. 
Winds forecast do not appear to be sufficient to cause seas to 
increase to 5+ feet. However...wavewatch guidance persists in 
placing most of the coastal waters in 5-6 foot seas today/tonight. 
At this time...will have Small Craft Advisory for the northern 2 coastal zones for seas through 00z 
Monday. Seas have increased to around 5 feet at 44009 and 44014...with 
greatest risk for 5 foot seas in coastal waters area being in the 
northern coastal zones. Seas expected to subside below 5 feet after 00z 
Monday. 


&& 


Hydrology... 
rainfall over the Piedmont and ridges to the west are forecast to 
bring significant rises to area rivers by Monday and Tuesday. Some 
locations will likely experience action stage and may possibly 
have minor flooding. This will depend on which basins locally 
heavy rainfall sets up which is too early to determine. 


&& 


Equipment... 
akq 88d radar is back in service. 


&& 


Akq watches/warnings/advisories... 
Maryland...none. 
NC...none. 
Virginia...none. 
Marine...Small Craft Advisory until 11 PM EDT this evening for anz650. 
Small Craft Advisory until 8 PM EDT this evening for anz652. 


&& 


$$ 
Synopsis...lkb 
near term...Sam 
short term...Sam 
long term...jab 
aviation...worse 
marine...worse 
hydrology... 
equipment...