Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Wakefield Virginia
842 PM EDT Wednesday Jul 23 2014
a cold front pushes across the region late tonight and Thursday...
then dissipates across the Carolinas Friday through Saturday as
high pressure moves north of the area.
Near term /until 6 am Thursday morning/...
scattered convection across the mts prognosticated to slowly move southeast ivof thermal
trough late this afternoon. Kept slght chance probability of precipitation through the evening. Models
show a lull in precipitation coverage later this evening before picking up again
after midnight ahead of apprchg cold front. Best support for precipitation
will be across northern half of forecast area towards sunrise with highest probability of precipitation
(40%) across northern most areas. Otw..pt to mostly cloudy & muggy.
Short term /6 am Thursday morning through Saturday/...
cold front prognosticated to drop southeast across the forecast area Thursday morning before
slowing as it apprchs the NC/NC border drng the afternoon. Meanwhile...
models depict weak short wave moving NE along the boundary drng the afternoon and
evening. Best forcing coupled with a 60-70kt rrq of upper jet appears
to enhance precipitation chance across southern half of forecast area. Appears that portions of
the forecast area that need rain the most (ivof ric metropolitan area) may Luck out
with the higher qpf's once again. Severe threat appears minimal due to
the extensive cloud coverage and timing of the frontal passage. Given precipitable waters at or above
1.5 inches...some heavy downpours and gusty winds possible in any tstrm
across the south. Kept likely probability of precipitation for now across southern half of
forecast area...chance probability of precipitation across the north. Temperatures tricky. Highs 80-85 north...
Boundary prognosticated to stall/wash out across southeastern Virginia/northern NC Thursday night
into Friday morning with lingering trough across the Carolinas Friday afternoon.
Likely probability of precipitation across the south during the evening...with chance probability of precipitation after
midnite. Drying from the north ends precipitation there. Still muggy Thursday
night with lows in the 60s. Dry Friday except kept a slight chance pop
in across NC counties drng the afternoon. Highs in the l-m80s.
High pressure builds into the area from the north Friday night and
Saturday. Models differ with respect to returning moisture Sat afternoon. GFS wetter
farther north. Kept slght chance probability of precipitation across the south for now given
the uncertainity. Lows Friday night 65-70. Highs Sat 85-90.
Long term /Saturday night through Wednesday/...
long term period starts off Sat night into sun with an upper-level trough
digging over the eastern Continental U.S. And surface hi pressure pushing offshore. A
complex area of surface low pressure will develop across the Great Lakes
region...with a prefrntal Lee trough leading to a chance of rain showers/thunderstorms
over the local area. With deep S/SW flow...temperatures will be about five
degrees above normal...highs in the low to middle 90s. The
aforementioned surface low will push east and drag a cold front into the middle
Atlantic region Monday/Monday night. Included a 40% chance of rain showers/thunderstorms
during this time period. Highs Monday in the upper 80s to lower 90s. Aside
from a low chance of rain near the CST...conditions will dry out for
Tuesday and Wednesday...with highs only in the middle 80s.
Aviation /01z Thursday through Monday/...
as of 23z...a broken line of thunderstorms extended from northern New
Jersey to west central Virginia. Have tempo showers at sby from
04-06z. Otherwise...activity should stay north of the taf sites.
Cold front found across central Pennsylvania and northern West
Virginia. This will press southward overnight and move through
ric/sby in the morning and reach southeast portions late in the day. Precipitation
breaks out on both sides of the front on Thursday with the best
chance for significant thunderstorm activity over far southern Virginia and NE North
Carolina. Indicated showers for ric/orf and phf in the afternoon. Thunderstorms
will be possible during these times. Precipitation should be mainly to the south
of sby and through 00z...north of ecg.
Kept IFR out of the forecast. Expect enough mixing to prevent fog but
some stratus will be possible. Have scattered stratus southeast portions but it is
possible that MVFR stratus may develop at some of the sites near
Surface high pressure builds back into the region from the west-northwest on Friday
and then slides off the middle Atlantic coast by Saturday. A complex
low pressure system may affect Sunday and Monday with a chance for
showers and thunderstorms.
Note: observations from ksby are not readily available due to a
communications problem. Technicians are aware of the issue.
Current information may be obtained by calling into the ASOS site
directly. In the meantime...amend not schedule will be appended to the
ksby taf until further notice.
sub-Small Craft Advisory conditions expected through the next few days with surface hi
pressure located well offshore and a fairly weak pressure gradient over the
middle Atlantic. Ahead of a prefrntal trough over the Piedmont this
aftn/eveng...southerly winds over the Bay will rise to 10-15 knots...just below
Small Craft Advisory thresholds. Seas will build to 3-4 feet for northern coastal waters. A cold
front crosses the waters on Thursday...with winds shifting from SW to northwest...and
staying sub-Small Craft Advisory behind the front due to very weak cold air advection. Benign marine
conditions continue into Friday and Sat as surface hi pressure builds into the
region. Winds will stay at or below 10 knots with 1-2 feet waves over the Bay and
2-3 feet over coastal waters. Next cold front crosses the waters late Monday/Monday
kdox radar has returned to service but remains unstable.