Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Wakefield Virginia
348 am EDT Thursday Jul 31 2014
high pressure over the middle Atlantic region this morning will slide
offshore through the day as low pressure stays well north of the
area. A frontal boundary will develop along the coast Friday...then
move inland through the weekend.
Near term /through tonight/...
latest surface analysis reveals broad ~1019 mb hi pressure over the middle
Atlantic region with low pressure well north of the area. Aloft...a hi-
amplitude upper-level trough remains in place across the eastern Continental U.S..
the surface hi slides offshore today...with southerly flow continuing. Model
thicknesses and MOS guidance support temperatures rising into the middle
80s...upper 80s possible in some areas. Otws...expect a mostly/prtly
sunny sky with continued dry weather. For tonight...an approaching middle-
level shortwave trough may lead to some isolated/scattered rain showers...especially
over the Piedmont. Another comfortable night with overnight low temperatures
ranging from the middle 60s to lower 70s.
Short term /Friday through Saturday/...
trough aloft will weaken/shift westward into the Ohio/TN/MS valleys
into Friday. Bermuda hi pressure rebounds across the western Atlantic...with deep
layered southwesterly flow aloft (ovr the eastern seaboard) and a surface frontal
boundary developing along the southeast Virginia/NE NC CST. In addition...an
easterly surface flow from the Atlantic will provide increasing low level
moist. The combination of these features will result in increased
shower/thunderstorm chances...esply Friday aftn/eveng...and thus will carry
40-60% probability of precipitation. With plenty of clouds around and precipitation possible...hi
temperatures on Friday will likely be a touch cooler than Thursday...in the lower
to middle 80s.
Friday night and Sat...the frontal boundary will nudge inland a bit
more...at least into eastern portions of the area. With a continued
moist surface-aloft flow over the region...and weak low pressure areas moving
north-northeast along the boundary...have gone with likely probability of precipitation (60%)
everywhere during this time. Expecting plenty of clouds...so highs
on Sat will only be in the lower 80s. Lows Friday night ranging from the
middle 60s to lower 70s.
Long term /Saturday night through Wednesday/...
a stalled frontal boundary and associated plume of Atlantic moisture
will linger over the middle Atlantic Saturday night through Monday
between a strong ridge over the western Atlantic...and a trough over
the Midwest. Generally expecting mainly diurnal afternoon/evening
showers/thunderstorms Sunday and Monday...with lingering overnight/early
morning showers. A cold front drops through the Great Lakes Monday
night and Tuesday...and then into the Ohio Valley by midweek. This
will shove the plume of moisture offshore...with probability of precipitation gradually
diminishing to slight chance northwest-southeast by midweek. Highs should average in
the low/middle 80s Sunday/Monday...and trend upward to the middle/upper
80s Tuesday...and upper 80s to around 90 Wednesday. Low temperatures
should generally be in the upper 60s to low 70s.
Aviation /07z Thursday through Monday/...
high prssure moving off the middle Atlantic coast will continue the
VFR conditions through the forecast period. Expect only cirrus along
with scattered cumulus today. S-southeast winds at or below 10 kts.
Outlook...threat for showers/tstrms increase Friday & continue into
the weekend as moisture increases along a stalled coastal front.
no headlines expected in short term as high pressure moves off the
middle Atlantic coast. A trough develops along the southeast and middle
Atlantic coasts Friday and Saturday. Expect an east-southeast wind through the
period at speeds at or below 15 kts. Seas averaging 2 to 3 feet with latest
wwa indicating seas building to near 4 feet by Friday night & Saturday
out near 20 nm. Winds become S-SW by Sunday remaining at or below 15 kts.