Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Wakefield Virginia
205 am EDT Wednesday Jul 23 2014
high pressure will slide south along the middle Atlantic coast
through tonight...as a frontal boundary remains nearly stationary
from the deep south to the coastal Carolinas. A cold front will
approach from the northwest on Wednesday...then push across the
region Thursday into Thursday night. High pressure will build over
the area on Friday.
Near term /until 6 am this morning/...
a more typical warm humid evening is occurring across the area
this evening as high pressure has now settled off the southeast
coast...with only a weak trough lingering in vicinity of the
Florida/GA/SC coast. Temperatures as of 9pm generally range from the
middle 70s to low 80s...with dewpoints ranging from the upper 60s to
low 70s. Afternoon/early evening showers/thunderstorms over southern portions
have dissipated. No additional showers are expected over the next
few hours. However...a weak impulse tracks NE in vicinity of Cape
Hatteras late tonight...so a 20-30% pop will be maintained for far
southeast portions after midnight. Otherwise...expect a warm humid night
with lows from the upper 60s far NE...to low/middle 70s elsewhere.
Patchy fog is also possible overnight to around sunrise.
Short term /6 am this morning through Friday/...
west/ surface hi pressure settling off the southeast Continental U.S. CST on Wednesday...incrsg/dp
layered south-southwesterly flow will push hotter air into the region. Hanging onto
20-30% probability of precipitation...primarily for the afternoon/evening hours...otherwise avgg psny. Low
level mixing (w/ south-southwesterly wnds) should lower dewpoints in the afternoon
hours...preventing heat indices from rising to/above 100f. Next trough
tracks through the Great Lakes and gradually amplifies into the
NE/middle Atlantic regions Wednesday into Wednesday night...pushing the next surface cold
front toward the forecast area. Hi temperatures will be mainly 90 to 95f inland...85 to
90f near the CST.
Timing of next cold front into/across the forecast area will be primary forecast
concern Thursday into Friday. 12z/22 NAM/GFS are a tad slower than their
00z runs west/ pushing the cold front southeast through the forecast area. Have nudged probability of precipitation
a little higher across the forecast area on Thursday due to slower timing (still 50%
far north...60% cntrl/s)...though that timing may be problematic
anyway for portions of the forecast area (esp central va) where precipitation deficits
past month or so average a couple/few inches. The cold front settles S into
northern NC Thursday night/early Friday...then is very slo to push S of there
(typical of this time of year) during rest of the day Friday. For
bulk of forecast area...expecting drying from the north and west as surface hi pressure
(1016-1020mb) builds into region from the Ohio Valley. Will hang onto 20-30%
probability of precipitation across portions of NE NC on Friday...otherwise p/msny west/ dewpoints
Low temperatures Wednesday night mainly in the l70s. Hi temperatures Thursday in the M/u80s
north...u80s to l90s S. Hi temperatures Friday in the M/u80s inland...l/m80s at
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 /06z 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.
a stationary front off the NC coast will dissipate heading into this
evening and overnight. Meanwhile...more typical Bermuda high
pressure takes control by Wednesday morning...and lasts until the
next cold front passes over the waters on Thursday. East-southeast winds at or below
10 knots currently will gradually veer to the SW tonight....then remain
SW 10 to 15 knots into Thursday morning. Once the cold front passes on
Thursday...winds will veer to the north-NE at or below 15 knots through Friday
morning. Winds become S-SW again at or below 15 knots by this weekend. Small Craft Advisory
conditions are not expected the next few days...and probably not
through the weekend either. Stayed close to nwps depiction for
significant wave heights through the weekend with seas 2-3 feet
building to ~4 feet Wednesday night/early Thursday before subsiding as winds
become north-NE Friday. Waves will remain 1 to 2 feet.