Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Wakefield Virginia
1018 am EDT Wednesday Jul 23 2014
surface high pressure will remain in place over the western
Atlantic today. A cold front will approach from the northwest
through tonight...then push across the region Thursday and
Thursday night. High pressure will build over the area on Friday.
Near term /through tonight/...
fog has quickly burned off with low clouds dsptg as well.
Weah high prs over the region to provide a return to above normal temperatures
today due to plnty of sunshine and a west-SW wind. Latest short range
models hold off most convective activity until aftr 21z...so
backed off probability of precipitation a bit Erly this aftr xcpt across southeastern Virginia/NE NC
where lingering trough may result in scattered convection by or shortly
aftr 18z. Highs l-m90s...a bit cooler at the beaches. Dew points
should mix out a bit resulting in heat index values at or below 100.
dampening upper trough and its associated surface cold front will
drop from the upper Midwest (this morning) towards the region late
tonight into early Thursday. Expect clouds to increase as the trough
approaches, becoming overcast late across the north/northwest (partly cloudy
se). As front sinks slowly south towards thea area late tonight,
will probably see some spotty rain showers/isolated T develop to our
northwest...potentially reaching northern County Warning Area by day break.
Therefore went with a 30-40% pop across the north...20% farther
south. Partly to mostly cloudy and muggy with early morning lows
in the low to middle 70s.
Short term /Thursday through Friday/...
surface cold front will be dropping southeast ac receiver station the County Warning Area Thursday
morning...reaching the coastal plain by afternoon. Unfortunately for
portions of the forecast area (namely central Virginia/Richmond metro) where precipitation
deficits past month or so average a couple/few inches, model guidance
continues to depict best forcing coincident with 60-70kt rrq of
upper jet arriving by Thursday afternoon and oriented from upstate SC/central
NC towards the Tidewater area. Therefore, have kept best
pop/higher quantitative precipitation forecast across the southern half of County Warning Area Thursday afternoon/evening,
gradually spreading southeast as the cold front settles farther south
into NE NC Thursday night/early Friday. As is typical for this time of year,
front will then likely get hung up across far southeast County Warning Area lt Thursday and
much of Friday. Otherwise, for bulk of forecast area...gradual drying from the northwest
to southeast is indicated as surface hi pressure builds in from the Ohio Valley.
Drop probability of precipitation off for most areas Thursday ngt, but did maintain 20-30% probability of precipitation
along the stalled boundary across coastal NE NC through Friday afternoon.
Otherwise clearing and becoming a bit drier late Thursday through
For temps, look for highs in the M/u80s north...u80s to l90s S Thursday.
Highs Friday in the M/u80s inland...l/m80s at the CST.
Long term /Friday night through Tuesday/...
stationary front remains over NC Friday night with high pressure
over the local area. This will result in dry conditions. Front
remains stationary over NC on Saturday before slowing lifting back
north through Virginia Saturday night into Sunday morning. Will carry
slight chance probability of precipitation across the far south Saturday for possibility of
afternoon convection near the front. By Sunday...the front will align
itself across northern Virginia and will be the focus for thunderstorm activity
across the entire area due to increased moisture/instability. Will
carry chance probability of precipitation into Monday as well as the front dissipates nearby.
The models are in good agreement about bringing a cold front through
the local area Monday night with dry/cooler air arriving next
Tuesday/Wednesday. Highs Saturday in the 80s. Warmest Sunday/Monday
with highs in the upper 80s to low 90s. Cooler again next Tuesday with
highs in the 80s. Lows mainly in the 60s to low 70s.
Aviation /14z Wednesday through Sunday/...
a warm front near the coastal Virginia/NC border will keep lingering
shower activity in the Albemarle Sound vicinity through at least
23/0800z. Thereafter...an approaching cold front will cause the warm
front to shift southeast and away from the area after daybreak. Fog
may be problematic across southern Virginia/NE NC...in the vicinity of the warm
front. Observations have shown variable visibilities of 1-5sm and
ceilings fluctuating between 100-1000 feet above ground level. At this time...kecg and ksby
should be most adversely impacted by fog with visibilities as low as
1sm possible and ceilings below 500 feet above ground level. Any fog that develops should
lift/dissipate by 23/1400z.
Otherwise...early morning sunshine in a moist and warm environment
will allow scattered-broken cumulus to develop by late morning/early afternoon.
Pre-frontal thunderstorms are expected to form by middle to late afternoon
today and all taf sites are anticipated to be impacted. The
previously mentioned cold front moves into the region from the
west by late this evening...bringing a more focused line of
showers and thunderstorms to the region overnight tonight into
Thursday. The front stalls along the NC coast by Friday morning.
This will shunt precipitation chances over far southeast Virginia and NE NC through
Friday...possibly into Saturday. Surface high pressure builds back
into the region from the west-northwest on Friday and then slides off the middle
Atlantic coast by Saturday...bringing a return to rain-free
conditions during the weekend.
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.
light and variable winds switching anywhere from east-southeast to S today with
speeds around 5-10 knots this morning...becoming 10-15 knots by this afternoon
as a cold front approaches the region from the west-northwest. A pre-frontal
thermal trough develops ahead of it and scattered thunderstorms will
be possible by middle-late afternoon through this evening. As the pressure
gradient tightens ahead of the front...wind speeds are expected to
increase this afternoon through tonight (aob 15 knots all waters...gusts to
around 20 knots possible over ocean). The cold front crosses the waters
late tonight into Thursday with showers/storms becoming more widespread.
Winds turn to a more S-SW direction tonight...W-NW on Thursday...then north
Thursday night. Waves generally 1 foot this morning...building to 1-2 feet
by middle-late afternoon through tonight. Seas 2-3 feet this morning...
building to 3-4 feet early this evening and overnight. Waves/seas
start to subside Thursday afternoon as the front begins to stall along the NC
coast...which will also cause precipitation to become shunted over far southeast
Virginia/NE NC by Thursday night into Friday.
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...bringing a return to onshore east-southeast winds at or below
15 knots through the rest of the weekend. The next cold front to impact
the region will approach the waters Sun night.
kdox radar offline at this time due to a transmitter failure on-site.
Technicans will be dispatched later this morning. Updates will be
passed along as they become available.