Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Wakefield Virginia
126 PM EDT Tuesday Oct 13 2015
a cold front crosses the area today and exits the coast by late
this evening. An upper trough swings across the Middle Atlantic
States on Wednesday...followed by high pressure building back
over the area Thursday. Another cold front tracks through the
region on Friday.
Near term /until 6 PM this evening/...
the current upper air analysis indicates a deep upper trough
tracking across the Ohio/Tennessee valleys. A middle-level front
precedes the trough and extends south-southwest from upstate New York through the
middle-Atlantic and southeast. Moisture is limited with this
b0undary...and the strongest forcing is well north of the local
area...hence radar returns have diminished quickly over the past
several hours. A surface cold front lags back to the west and will
arrive later this afternoon. The passing cold front this afternoon may
provide just enough instability/lift to rejuvenate shower
activity...especially across NE NC and far southeast Virginia. Will need to see
if downsloping can overwhelm any chance of shower development this
afternoon. A 20% pop will be maintained at this time.
Variably cloudy today with a breezy SW wind. Expect gusts of
15-20 miles per hour inland and 25-30 miles per hour closer to the coast. Temperatures
will warm nicely today in the well-mixed environment with highs of
Short term /6 PM this evening through Thursday night/...
a cooler airmass moves into the region from the northwest behind the
frontal passage tonight. Gradual clearing overnight with winds
becoming light late will allow temperatures to fall to
50-55 degrees northwest (upper 40s possible far northwest counties) to
55-60 degrees southeast by morning.
A broad upper level trough swings through the middle Atlantic region
Wednesday/Wednesday night. West-northwest winds around 10-15 miles per hour...dry air aloft...and
falling heights will result in a sunny but cool day. Temperatures will be
slow to warm into the lower 70s for afternoon highs. The more
noticeable cool down will occur Wednesday night as high pressure builds
into the region from the west. Continued northwest winds will stream
additional cooler air into the region and clearing skies will
promote excellent radiational cooling conditions. Expect lows in the
middle-upper 40s west and in the upper 40s to lower 50s east (low-middle
50s at the beaches). High pressure slides over the area on Thursday and
shifts southward Thursday night. Additional effects from subsidence aloft will
support even cooler high temperatures in the middle-upper 60s on Thursday. An
approaching cold front Thursday night will cause winds to become more southerly
and prevent overnight lows from reaching their fullest potential
(despite mostly clear skies). Expect slightly warmer lows in the
upper 40s inland to low-middle 50s closer to the coast.
Long term /Friday through Monday/...
long term period will feature dry conds and decreasing temperatures through
the period. For Thursday night...surface hi pressure centers over the southeast states
as an upper-level trough and associated surface cold front approach from the
Ohio Valley. The front crosses the area late Friday/Friday night...with a dry
frontal passage expected as the best shortwave energy stays north of the forecast area per
the 12z GFS and European model (ecmwf). Hi temperatures Friday average in the lower 70s across the
forecast area...with lows Friday night ranging from the middle 40s over the Piedmont to
the middle 50s near the CST. Weekend through Monday then looks dry with
strong surface hi pressure building into the area and hi temperatures only in the
low/middle 60s each day...with overnight lows dropping into the middle/upper
30s over coldest areas (piedmont) both Sat night and Sun night. Lows
average near 40 along the I-95 corridor.
Aviation /17z Tuesday through Saturday/...
as of 17z...a cold front was pushing into western Virginia. In advance of
the front...SW winds were gusting to around 20 knots. Just scattered to broken
SC and ac clouds ahead of the front...and mainly just scattered SC
behind the front. The cold front will exit the CST late tonight/early
Wednesday morng...with winds turning to the W/NW.
Outlook...high pressure returns to the region through Thursday. High
pressure slides offshore Thursday night...as the next cold front
approaches the area. The front passes through dry late Friday into Sat
with high pressure building in from the northwest Sat into sun.
sub-Small Craft Advisory conditions prevail early this morning...as winds have
shifted to the south-southwest and generally average 10 to 15 knots. As the pressure
gradient continues to increase later this morning expect wind
speeds to ramp up...and have hoisted a marginal Small Craft Advisory later this
morning for the Bay/lower James/Currituck Sound (added to the Small Craft Advisory
already going into effect across the northern coastal waters). Seas will
also build through the morning hours...to 4-5 feet over northern waters by
late morning...while averaging 2-3 feet in the Bay. Still expecting
these to be minimal Small Craft Advisory events generally lasting only ~ 6 hours.
Due to a lack of cold air advection behind the front expect conds to stay sub-Small Craft Advisory
tonight into Wednesday. Ramp winds up a bit Wednesday night to minimal Small Craft Advisory
thresholds in the Bay as wind directions turn more northerly and
colder air does surge briefly down over the waters. Winds then
return back to the west/SW Thursday night and increase again Friday ahead of
the next cold front. A more significant surge of wind is likely
either Sat or Sat night/sun as strong high pressure builds into
the area and reinforces a much colder airmass over the waters.
Marine...Small Craft Advisory until 7 PM EDT this evening for anz650-
Small Craft Advisory until 4 PM EDT this afternoon for anz633.