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Area forecast discussion 
National Weather Service Wakefield Virginia 
709 PM EDT Sat Jul 5 2008 


Synopsis... 
a frontal boundary will remain nearly stationary across the middle 
Atlantic region...keeping unsettled weather across the area 
through Monday. The front finally pushes off the coast Monday 
night...as weak high pressure builds in for Tuesday and Wednesday. 


&& 


Near term /until 6 am Sunday morning/... 
unstable airmass firmly entrenched across the middle Atlantic and Carolinas 
early this evening...with distinct surface trough/conv boundary from 
Georgia/SC northward into the Virginia Piedmont....and along this boundary is 
where greatest coverage of storms has been thus far. Have issued 
some severe but overall storms appear to be weakening over past 
hour...transitioning to primarily heavy rainers. Have updated forecast 
to go Cat probability of precipitation for portions of interior southeast/cnrl Virginia for rest of 
eveng. 


For later tonight...still good consensus among NAM/GFS that the 
upper low will amplify a bit...bringing strong upper diffluent 
zone into the middle Atlantic after midnight. Low level instability will be 
weaker at that time...but with dew points around 70...expect there will 
still be sufficient lift for at least scattered thunderstorm activity even 
after midngt...with potential for heavy downpours/localized 
flooding continuing. Have likely probability of precipitation all zones overnight (except 
in NC dropped probability of precipitation to 50% after midngt). Severe threat certainly 
possible with strong lift...but overall should be isolated as freeze 
levels are rather high and bulk 0-6 km shear is about 20 kts or 
less. 


&& 


Short term /6 am Sunday morning through Tuesday/... 
unsettled pattern will continue Sunday...with more clouds than sun 
expected and continued with high chance (40-50%) probability of precipitation in 
morning...and likely (60%) during afternoon. High temperatures again held in 
check (mainly in middle 80s) due to the clouds and moisture. Upper trough 
slowly tracks farther east by Monday...and have focused highest 
precipitation chances Monday across NE NC/far southeast Virginia...with somewhat lower 
chances elsewhere (but still above climatology at aroound 40%) 


By Monday ngt/Tuesday...should see a return to a more typical Summer 
diurnal pattern with partly cloudy skies and only 20-30% chances for 
precipitation primarily during afternoon/eveng hours. Temperatures also rise back into 
the 90s with more sun expected. 


&& 


Long term /Tuesday night through Saturday/... 
Bermuda high pressure builds in by Tuesday night. Kept 20% chance of 
rain showers/thunderstorms through then with the highest chance over southeast Virginia/NE NC where 
lingering moisture and forcing mechanisms from the frontal remnants 
will still be in place. Lows will be in the upper 60s in western sections 
to lower 70s in the east/coastal locations. 


Wednesday am starts out dry. An upper level trough and associated surface 
front located near the Great Lakes begins to move closer during the 
day...while the S/SW flow around the high offshore increases. 
Abundant moisture will get pumped up around the high and ahead of 
the front...so have 20% chance of rain showers/thunderstorms during peak heating 
hours. The front then sags to the south Wednesday night through Thursday night. 
Chance of rain showers/thunderstorms continues through this period as the boundary 
slowly attempts to move farther through our area. High temperatures will be in 
the upper 80s/lower 90s Wednesday and Thursday...and low temperatures will range from the 
upper 60s/lower 70s. 


The front will stall and eventually wash out across our southern counties 
on Friday. Will still have a chance of precipitation on Friday through Friday night in 
the south closest to what will be left of the boundary...with a 
slight chance farther north and west. High temperatures will be cooler on 
Friday with 850 temperatures falling to 13 to 15c and with additional cloud 
cover. Min temperatures will also drop slightly on Friday night/Sat 
am...generally 65 to 70 except lower 70s right at the southern beaches. 


&& 


Aviation /23z Saturday through Thursday/... 
isolated-scattered convection still on tap for today as same humid airmass in 
place. Front will continue to lie mostly to the north of our region. 
Mostly VFR for the terminals except in shower/thunderstorm activity which 
might last into late evening. Areas of fog will affect terminals 
overnight into the morning with MVFR/IFR conds...along with smoke in 
the southeast. 


Longated warm conveyor belt with a subtropical connection from the 
western Gulf will maintain a fairly moist column over the region today and 
through Monday. By early next week...a middle level shortwave and 
subsequent westerly flow finally pushes the surface front off shore. 


&& 


Marine... 
main concern this evening will be thunderstorms that will continue to affect 
mainly the southern waters. Could have wind gusts up to 33 knots with 
lightning strikes and small hail possible in the heaviest storms. 
Meanwhile...smoke from the wildfire near Suffolk Virginia will continue to 
affect the waters around the Tidewater region (srn ches Bay and the 
southern Atlantic waters)...with smoke from the fire in Hyde County NC 
moving across Currituck sand. Visibilities may be reduced locally down to 1 
to 3 miles where smoke is the thickest so use caution if boating. 


Wind pattern remains diurnally driven with onshore winds through this 
evening due to seabreeze development. Winds will eventually diminish 
and become S after midnight tonight. The pressure gradient tightens by 
Sun afternoon as a front moves closer to the waters from the northwest. May have 
a few gusts to Small Craft Advisory (20 kt) across the ches Bay and a few gusts to 25 
knots across the Atlantic waters late on sun...but do not think that the 
coverage and duration of such winds would be great enough to raise Small Craft Advisory 
flags at this time. Will continue to monitor for any changes. 


The front will stall and wash out over the southern waters during the 
early part of the week...while Bermuda high pressure builds back in. 
Another front approaches from the northwest and then stalls out across southern 
zones late Wednesday through Thursday. 


&& 


Fire weather... 
light southerly flow to continue tonight and Sunday so smoke will 
continue to affect much of metropolitan Norfolk/Portsmouth and outlying 
areas. High relative humidity overngt/Erly Sunday morning will have 
potential for smoke/superfog scenario. Winds should allow for some 
improvemnt again by midday Sunday. 


&& 


Akq watches/warnings/advisories... 
Maryland...none. 
NC...none. 
Virginia...none. 
Marine...none. 


&& 


$$ 
Synopsis...lkb 
near term...lkb 
short term...lkb 
long term...jrl 
aviation...jef 
marine...jrl 
fire weather...lkb 

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