Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Wakefield Virginia
401 PM EDT Tuesday Jul 7 2015
a frontal boundary will approach from the north and west...stalling
just north of the area Wednesday night through Thursday afternoon.
This will result in a chance for showers and thunderstorms late
Wednesday afternoon into Wednesday night. Hot and mainly dry weather
will prevail Thursday...with slightly cooler temperatures on
Friday as the front sinks south and dissipates across the area.
Near term /until 6 am Wednesday morning/...
latest analysis indicating an strong upper level trough over
central Canada and the western Great Lakes with upper level ridging off
the middle/Atlantic and southeast coast. Surface low pressure is centered east of
Hudson Bay...with a strong cold front extending SW all the way
into the middle MS valley. Typical summertime conditions over the
local area with temperatures mainly in the upper 80s to around 90
f. All of the recent rain likely enhancing low level moisture...with
afternoon dew points failing to drop much...ranging from 70-75 f across most
locations. Not excessive...but heat indices are running in the
middle to upper 90s for the most part.
Finally having a mainly dry day across the region...though will
continue to keep 20% chance for thunderstorms over south central/southeast Virginia and NE
NC through 01z where ml convective available potential energy average ~2000 j/kg per latest Storm Prediction Center
mesoanalysis. West/ loss of heating by sunset...expect skies to
become mainly clear all zones west/ no additional chances for rain.
Warm/humid overnight with lows in the lower to middle 70s.
Short term /6 am Wednesday morning through Friday/...
models in reasonably good agreement Wednesday/Thursday with upper level ridge
expanding west to become centered across the Gulf Coast states to
the southeast Atlantic coast. Fast moving west-southwest flow aloft Wednesday into Thursday will
gradually shift to the west-northwest by Friday. Surface low pressure is prognosticated to
track from the upper Ohio Valley to the New Jersey coast Wednesday...bringing more
significant forcing to the local area Wednesday afternoon. 12z NAM appears
too wet across NC...given the pattern but will have at least 30%
probability of precipitation for all zones by late afternoon/after 20z (highest probability of precipitation across the
north). Still looks like shear is too weak for much severe threat but
gusty winds and locally heavy rain once again will be possible.
Highs into the Lower-Middle 90s S to the upper 80s north (where clouds/precipitation
arrive earlier). Models show some continued shortwave energy overnight
Wednesday night across the NE zones...and will maintain chance probability of precipitation (30%) there
into the early morng hours of Thursday. Lows 70-75 f. Probaly a little
hotter on Thursday with highs in the middle 90s most areas as deeper west-southwest
flow devlops. Slight chance of late afternoon/eveng thunderstorms across the
region...but models are suggesting that the deep west flow may dry
conds out/limit probability of precipitation. Slightly cooler Friday as front dissipates over
the area...highs middle 80s north to lower 90s SW.
Long term /Friday night through Tuesday/...
southeastern U.S. Ridge will continue to retrograde west next
weekend...ending up over West Texas/Southern Plains by Sunday before
expanding/building north over the Rocky Mountains early next week. This
will set the stage for northwest flow to develop over the middle-Atlantic
region this weekend...then more pronounced troughing over the East
Coast next week. A series of disturbances originating in the
Midwest/Ohio Valley will make a run at the local area this
weekend...but timing these features will be difficult. Went with
generally climatology probability of precipitation Sat/sun (20-30%)...then increased them a little
bit next Monday/Tuesday with the strengthening upper trough overhead.
Seasonable temperatures are expected through the period with lows in the
upper 60s to middle 70s...and highs in the middle/upper 80s to low 90s.
Aviation /20z Tuesday through Sunday/...
weak high pressure over the region this afternoon and limited
moisture leading to VFR conditions across the region. Some
afternoon cumulus has popped in the heating of the day across southeast Virginia/NE
NC. Expect little convection due to the dry air aloft. As the surface
high weakens late this afternoon and tonight...will see the SW
flow continue at around 5 - 10 kts this evening and tonight.
The next front will approach from the northwest on Wednesday...keeping the SW
flow in place. Through 18z...expect just some cumulus to develop. So
VFR conditions will prevail through the forecast.
Outlook 18z Wednesday - sun...the front approaches Wednesday afternoon so
expect some convection with restrictions of visible and ceilings with
the thunderstorms. The front lifts back north on Thursday before
another front slides across early Friday morning with chances for
more convection. Drier conditions are expected Friday and Saturday
as high pressure build through the middle Atlantic.
typical summertime pattern setting up for the middle to late week
period. Surface high pressure will linger over the western Atlantic
while a weak surface trough sharpens inland. SW flow will persist
through Thursday with speeds generally at or below 15 knots. Winds turn northwest at
similar speeds Friday...then light and variable winds are expected
this weekend. Seas will remain 2-4 feet/ches Bay 1-3 feet.