Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Wakefield Virginia
835 PM EDT Thursday Jul 24 2014
a frontal boundary slowly dissipates across North Carolina
tonight through Friday. High pressure builds north of the area
Friday and Saturday. A cold front approaches from the northwest
Monday then crosses the area Tuesday.
Near term /until 6 am Friday morning/...
Northampton County storm survey results can be found by
referencing the latest public information statement (pnsakq)...
Dropped northern most counties of watch box as the severe threat has
shifted to the line of storms now apprchg the Virginia/NC border. Even
these storms beginning to weaken a bit.
quick update to account for severe tstrm watch until 03z. Mesoscale low
along slow moving front continues to be fueled by merging inflow
boundaries and untapped instability. This expected to continue to
drift southeast next few hours before weakening after 00z. Bumped up probability of precipitation
where convection is headed.
current msas showing frontal boundary draped across southern Virginia
with weak impulse moving NE along it. First impulse (which
produced this mornings convection) now offshore with secondary
impulse to be the trigger for the next round of convection late
this afternoon and evening as boundary stalls ivof Virginia/NC border. Short
range models move this convection southeast across the region through the
evening hours then takes most precipitation south into NC after midnight.
Given the development over the past hour and addntl convection
dvlpng along outflow boundaries... went with likely probability of precipitation through 00z for
areas west of the Chesapeake Bay...chance probability of precipitation elsewhere. Kept chance
probability of precipitation going across southeastern Virginia/NE NC after midnight as boundary will be
slow to drift south through 12z Friday. Weak flow will allow for
slightly cooler and dryer air to filter into the northern half of
forecast area after midnight. Lows in the 60s except near 70 southeastern beach areas.
Short term /6 am Friday morning through Sunday/...
models wash out boundary across the Carolinas Friday as upper trough axis
pushes east. Tsctns show just enough moisture/instability for slght chance
probability of precipitation across NE NC counties Friday afternoon. Otw...dry with below normal
temperatures. Highs l-m80s.
High pressure builds into the area from the north Friday night and
early Saturday with relatively weak cold air advection. Models differ a bit with respect to
moisture returning across the Piedmont Sat. Given the midlevel
cap seen in soundings...kept forecast dry but kept probability of precipitation below 15% Sat. Heat
and humidity begin to return as 850 mb temperatures rise. Highs Sat u80s-l90s.
Lows Sat night 70-75.
Next front apprchs from the northwest late Sunday. Dry through 18z with chance
probability of precipitation drng the afternoon/evening hours (20% southeastern areas to 40% northwestern cntys).
Long term /Sunday night through Thursday/...
medium range models are in decent agreement about pushing a cold
front through the local area on Monday as a rather anomalous upper
low digs into southeastern Canada and the eastern U.S. The front will be
driven as far south as the Gulf Coast by early Wednesday as a broad
area of high pressure expands from the High Plains to the eastern
Seaboard. The good news is some much needed rain is expected
along/ahead of the cold front Sunday night into Monday. The even
better news is a comfortable airmass will follow the front into the
local area from Tuesday into at least next Thursday. After a rather
warm day on Monday (highs in the upper 80s to low 90s)...cooler and
less humid conditions arrive Tuesday-Thursday with highs in the
low/middle 80s. Low Sunday night in the upper 60s to middle 70s...cooling
into the upper 50s to middle 60s Tuesday night.
Aviation /01z Friday through Tuesday/...
as of 00z...line of thunderstorms moving across southeast portions of the area with
IFR conds in heavier rain. Will likely need to update ecg. With
rain extending across the taf sites. While drier air moves in and
clears off some of the layered cloudiness...IFR fog is possible due to
wet ground... included at some of the sites. VFR conds expected by
middle morning as high pressure builds in.
Outlook...mainly VFR through Saturday. Complex low pressure and
frontal system affects the area bringing a chance for mainly afternoon thunderstorms
Sunday and Monday. Dry weather returns for Tuesday.
Note: observations from ksby are not readily available due to a
communications problem. Return to service is unknown at this time.
However...current information may be obtained by calling into the
ASOS site directly. Amend not schedule will be appended to the ksby taf
until further notice.
a cold front will continue to push south of the waters through this
evening. Behind the front...high pressure starts to nose into the
area overnight. North-NE winds will average 10-15 knots. Waves 1-2
feet...with seas 1-3 feet.
An upper level trough pushes across the waters on Friday as surface high
pressure builds back into the middle Atlantic region. Winds north-NE at or below
10 knots Friday/Friday night. The surface high then slides off the middle Atlantic
coast by Sat morning with southeast winds at or below 15 knots...becoming SW by Sat
night into Sunday. SW winds continue Sunday into Monday before the
next cold front moves through Monday night and turns the winds to
the northwest at or below 15 knots into Tuesday.
Waves will remain 1-2 feet through Tuesday. An increase in seas to
around 4 feet is expected across the northern waters Sat night into
Monday due to increased S-SW flow.
kdox radar is down for part replacement. Radar expected to returned
to servive once work is completed.