Area Forecast Discussion
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FXUS61 KAKQ 191747
Area Forecast Discussion
National Weather Service Wakefield VA
147 PM EDT TUE JUL 19 2016
A cold front moves slowly south across the Mid Atlantic States
through Wednesday and then dissipates over the Carolinas later in
the week. High pressure builds south into the area tonight and
Wednesday. High pressure over the Southeast states becomes the
dominant weather feature late in the week.
.NEAR TERM /THROUGH TONIGHT/...
The weather map this morning had an east to west cold front
oriented across Maryland to the Ohio Valley. High pressure was
over the Great Lakes. In the upper levels...a weak zonal flow and
some capping was holding off convection across the area. The cold
front will be rather diffuse today and become better defined while
moving south into North Carolina tonight and Wednesday morning as
high pressure builds to the north of the region.
An instability axis with mixed layer CAPEs over 2k develops over
northeast North Carolina this afternoon. Dry air and weakening
inversion should inhibit significant convection at that time. A
short wave moving south from the Great Lakes will steepen lapse
rates from north to south late this afternoon and this evening.
Have highest POPs over the Piedmont by mid afternoon with likely
POPs appearing across the Interstate 95 Corridor and in the 5 PM
to 8 PM time frame and moving into southeast Virginia and
northeast North Carolina after sunset.
The Storm prediction Center has most of the area away from the
coast in a slight risk for severe thunderstorms with the main
threat being damaging winds. Strengthening lapse rates will be the
primary contributor to expected instability.
Abundant sunshine during the first half of the day will bring high
temperatures to around 90 degrees inland and a few degrees cooler
near the coast. Dew points have lowered a few degrees from
yesterday`s values eliminating the potential for heat index
Convection shifts to the southeast and moving out of the area by
shortly after Midnight. NAM12 suggests some upper level impulses
and left over instability warranting low chance POPs through the
pre-dawn hours. Low temperatures are expected to be around 70
degrees Wednesday morning.
.SHORT TERM /WEDNESDAY THROUGH THURSDAY/...
Trough axis pushes offshore Wednesday as the upper level ridge
amplifies over the nation`s mid section. Surface high pressure
builds into New England as the cold front washes out over the
region. Expect enough forcing and moisture for a mention of slight
chance to low end chance POP`s across the far southeast forecast
area for diurnally driven showers and thunderstorms Wednesday. Weak
flow may also result in seabreeze convection over the Eastern Shore
to southeast Virginia. Otherwise, cooler, with highs in the mid 80`s
under a mostly sunny to partly cloudy sky. High pressure settles over
the Mid Atlantic region Wednesday night with dry conditions and a
clear sky expected. Lows in the mid to upper 60`s inland to low 70`s
near the coast. Surface high pressure slides offshore Thursday as
the upper level ridge builds eastward. Dry conditions continue with
highs in the upper 80`s.
.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
Long term period will feature mainly dry conditions and above
normal temps. For Thursday night/Friday, dry wx expected as
surface high pressure slides just offshore and a broad upper-
level ridge slides east into the eastern Conus. Temps max out in
the lo-mid 90s.
For the weekend, a thermal trough will hold in place over the Mid
Atlc with weak w/nw flow aloft. Expect hi temps in the mid/upr 90s
both days, and with dewpoints in the lo/mid 70s, afternoon heat
indices will be near 105f (heat advsry criteria). 10-20% chances
for rain Sat increase to 20-30% Sun. Continued hot into Mon (highs
up to the mid 90s) with a 30% chance for rain as stronger mid-
level energy approaches the region.
.AVIATION /18Z TUESDAY THROUGH SUNDAY/...
Mainly VFR conditions thus far this afternoon with sct-bkn
ceilings developing between 4-5 kft. Convection was developing on
the east side of the mountains and across the western piedmont
moving southeast. Forcing from an upper level wave will support
the development of more storms as the system progresses east.
This would place showers and storms into RIC around 22z-01z. Have
placed a tempo group in the RIC TAF. Storms will result in brief
periods of IFR visbilities and gusty winds of 25-35 kt. For now it
appears the best chances for showers and storms remains south of
SBY, so have left mention out of the SBY TAF for now.
The forcing pushes southeast to PHF and ORF from 23z-02z with
showers and storms possible at both location along with brief
periods of IFR visibilities and gusts winds similar to RIC. ECG
will experience the storms a little later...mainly after 00z. Due
to the upper level support the storms should be able to sustain
themselves into northeast NC and may not weaken much with sunset.
some lingering showers/tstms are possible over northeast NC after
06Z. In the wake of the showers there is the the potential for
patchy fog and/or low clouds through 12Z/Wed with some IFR
possible at all TAF sites. Confidence is low and have held off on
putting IFR conditions in the TAFS, but IFR conditions are
possible during the early morning hours Wednesday.
OUTLOOK...Southern areas may see widely scattered to isolated
afternoon tstms again Wednesday. Otherwise, mainly dry conditions
are expected for the latter half of the week.
Current conditions now have winds that average around
5-10 Kt across the waters with the stronger winds now well off the
coast as tstms have pushed farther offshore. Later today, a cold
front weakens as it approaches from the nw, allowing NW winds to
shift to the E/NE at only 5-10 Kt by this afternoon/evening. Lack
of cold air advection and weak gradient winds will keep winds sub-
SCA (to avg 10-15 KT) in the wake of the front on Wed. For Wed
aftn/Thu...winds avg aob 10 kt with weak sfc hi pressure in the
vicinity. Waves remain 1-2 ft with seas 2-3 ft. Winds increase to
10-20 Kt from the SSW Fri aftn/Fri night ahead of next frontal