Area forecast discussion
National Weather Service Wakefield Virginia
212 PM EDT Tuesday may 21 2013
Synopsis...
the combination of high pressure over the Atlantic and southwest
surface winds will continue to pull a warm and humid airmass into
the region through Thursday. A cold front will pass through the
Middle Atlantic States Thursday night. Surface high pressure returns
to the area Friday into the weekend with drier conditions and
cooler temperatures expected.
&&
Near term /until 6 PM this evening/...
there is plenty of low level moisture(pwats ~1.5 in) and moderate
cape values(~1100 j/kg)...so generally have 30 to 40 percent probability of precipitation
on today during the afternoon and early evening hours...decreasing
for the late night and morning hours.
Temperature will maximum out near 80 along the coast to the middle 80s
inland. High temperatures may end up being a few degrees cooler if cloud
and precipitation regions are more expansive than anticipated.
&&
Short term /6 PM this evening through Thursday night/...
on Wednesday...there will be less coverage of precipitation as
upper level support weakens. Guidance on Wednesday is still
unclear as to where to focus precipitation and kept 30 percent
probability of precipitation area wide that afternoon and early evening.
On Thursday...upper level dynamics increase as the cold front over
the plains states approaches the area. Have 40-50 percent probability of precipitation for
showers and thunderstorms except 30 percent in the far southeast.
NAM has lowered maximum temperatures significantly during this period
and is close to Euro. Lowered readings a few degrees from the
previous forecast with highs low to middle 80s Tuesday...middle to upper 80s
Wednesday and around 80 on Thursday. Readings will be a bit cooler
near the coast. Lows will be generally in the middle to upper 60s.
&&
Long term /Friday through Monday/...
long range models continue to push cold front across the region Thursday
night and offshore Friday am. Will keep the chance probability of precipitation with this
feature. Lingering moisture now prognosticated to shift offshore with the
boundary Friday so will only carry chance probability of precipitation along the coast Friday morning.
Lows Thursday night in the 60s.
Canadian high pressure builds into the area from the northwest Friday afternoon through
the rest of the Holiday weekend. Upshot will be a dry prd with
temperatures a few degrees below normal.
Still warm Friday with highs in the u70s-l80s. Cold air advection kicks in Friday night.
Lows through weekend in the 50s. Highs each day l-m70s...warming into the
M-u70s Monday.
&&
Aviation /18z Tuesday through Sunday/...
SW winds will prevail during the taf period. Widely scattered convection
will be possible over southeast portions through early evening. Included tempo
group for thunderstorms at ecg through 20z. All of the sites were varying
between VFR and MVFR and this will be the trend for at least the
first few hours of the taf period and likely again late Wednesday
morning. IFR stratus is indicated by MOS and NAM bufr soundings at
most of the taf sites for Wednesday morning roughly from 08 to 14z.
Conditions will slowly improve Wednesday morning.
Outlook: isolated to widely scattered convection will be possible late
Wednesday afternoon and evening. IFR stratus will be possible again Thursday
morning. More widespread convection is expected Thursday afternoon and
evening as a cold front approaches. The weather improves Friday and
beyond following the cold frontal passage.
&&
Marine...
no flags expected today through Wednesday...as south-southwest flow (aob 15-20 kts with
seas 2-4 ft) continues around hi pressure off the CST. Pressure gradient
will increase a bit late Wednesday through Thursday ahead of approaching cold front
prognosticated to cross the area Thursday night through Friday morng. Any Small Craft Advisory conditions
that develop will be marginal ahead of the front. Wna continues to
forecast seas around 5 feet out near 20 nm starting late Wednesday...but will
hold off on any headline for now. Winds will shift to the northwest or north Friday
afternoon behind the front.
&&
Akq watches/warnings/advisories...
Maryland...none.
NC...none.
Virginia...none.
Marine...none.
&&
$$
Synopsis...bmd
near term...bmd/mas/dap
short term...lsa
long term...mpr
aviation...lsa
marine...tmg
