Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Wakefield Virginia
101 am EST sun Nov 29 2015
a cold front sags south through the middle Atlantic region late
tonight through Sunday...stalling across the Carolinas Sunday
night into early next week. The next cold front is expected to
cross the region on Wednesday.
Near term /until 6 am this morning/...
another mild/quiet evening across forecast area. Cold front has drawn closer to the forecast area
past 24 hours...now found from near the PA-Maryland border to the central Ohio Valley
to the western Gulf of mex. Scattered -r has been trying to inch closer over
the mountains this evening and will slowly push into far northwest-north counties the
rest of tonight. Otherwise...mostly cloudy cntrl/N...partly S. Low temperatures
mainly from 50-55f.
Short term /6 am this morning through Tuesday/...
the cold front sags southward into lower Maryland by Sunday morning...then
into central Virginia by early afternoon and NC middle afternoon. The front
will stall over the Carolinas Sun night into early next week as
the parent high remains well to north over eastern Canada. Rain is
not expected to begin across far northwest-north counties and lower Maryland
until the early morning hours on sun. As the front drops through
the area...rainfall (light and scattered in nature in the morning)
will slowly spread southward and become a little more widespread Sun
afternoon. Scattered light rain may not push into southeast Virginia
until late Sunday afternoon into Sunday evening.
A better chance for more widespread rain in expected late Sunday
night into Monday as better dynamics aloft enhance precipitation
generation. Meanwhile...high pressure slides across southeast Canada into
northern New England during this timeframe extending down into the Middle
Atlantic States. This will create a cold air wedge on the leeside
of the Appalachians into central Virginia reinforcing the seasonably cool
air. Rain chances will continue into Monday/Monday night...but models
have backed off on the amount of overrunning with the cooler wedge
in place. Best probability of precipitation remain over the southern half of the forecast
area where isentropic lift is expected. Pop forecasts for this
period will likely chance as the models have been somewhat
inconsistent handling moisture Monday afternoon into Tuesday.
Overall quantitative precipitation forecast amounts remain fairly light (0.10 inches or less in
any given 6 hour period) with forecast total rainfall averaging
0.30-0.40 inches mainly across the south. Temperatures will be
highly variable on sun as the front drops through the area.
Currently anticipating highs in the middle- upper 50s north to middle-
upper 60s south through temperatures will fall in the late afternoon
across portions of the area. Lows Sun night in the 40s
inland/lower 50s far southeast Virginia and NE NC. Effects of the cad
wedge will be felt on Monday with highs in the middle-upper 40s
along/west of Interstate 95 and in the 50s eastward. Temperatures likely to
hold nearly steady Monday night. Lows in the 40s inland/lower 50s
along the coast.
Rain chances increased again on Tuesday as the shallow cad
remains in place and low pressure develops along the stalled
front just off the coast. The cad does look to slowly erode
Tuesday allowing high inland to get into the lower to middle 50s with
lower 60s closer to the coast and Bay.
Long term /Tuesday night through Saturday/...
going with a blend of the 12z GFS/European model (ecmwf) for the extended period.
Cold front will approach from the west Tuesday night...then cross the region
and move off the CST Wednesday into Wednesday night. Will have hi chance to likely
probability of precipitation for rain Tuesday night into early Wednesday afternoon...then decreasing probability of precipitation
from west to east later Wednesday afternoon into Wednesday eveng. Both the latest GFS and
European model (ecmwf) now indicate dry weather for later Wednesday night through Sat...as a large
area of hi pressure builds eastward and eventually over the area from the
plains and Midwest. Lows in the upper 40s to middle 50s Wednesday morng...in
the middle 30s to middle 40s Thursday morng...and in the lower 30s to lower 40s
Friday and Sat morngs. Highs in the upper 50s to middle 60s Wednesday...and
mainly in the lower to middle 50s Thursday...Friday and Sat.
Aviation /06z Sunday through Thursday/...
03z update...phf has fog with variable visibility values. The taf
has tempo group for 2 miles until 07z. It is believed that this fog
is very shallow and concentrating in the lowest spots of the
01z update...removed tempo IFR at ecg due to current trends. MVFR
fog remains in the forecast from 04-08z.
calm to light southwest winds off of a retreating high pressure
system prevailed over the area early Saturday evening.
Broken to overcast middle and high level clouds are expected to prevent the
redevelopment of ground fog that took place the last three nights.
Included visibility restriction at ecg where less wind and clouds may
allow some fog...especially early in the evening. Included MVFR 02-
08z with a couple of hours of tempo IFR. NAM MOS has IFR for most of
the overnight hours but this appears overdone.
A cold front extends from central New Jersey across northern
Maryland to southern Ohio. This front will drift to the south
through Sunday. Rain is developing along and to the north of the
front and has developed over northeast Kentucky...northern West
Virginia and southern Pennsylvania. Confidence for the start time
of rain is low but followed close to our pop forecast and is
earlier than the lav MOS and later than the NAM. Rain begins in
the tafs at 10z for sby...14z for ric and 21z for phf. Ceilings
lower through the taf period and especially as precipitation develops.
There is some indication that rain may taper off before 00z at ric
and sby which may result in fine tuning later.
Outlook...periods of rain and IFR conditions can be expected through
Wednesday with onshore NE winds at the surface and a moist west to
southwest flow aloft. As high pressure builds south into the Middle
Atlantic States...a cold air wedge will develop along the east side
of the Appalachians...promoting deterioration of aviation
conditions...especially at ric.
A cold front sweeps off the coast Wednesday bringing in drier air
and VFR conditions to the area beginning Wednesday night and
10 PM update...removed the Small Craft Advisory for the Virginia coastal waters S of Cape
Charles as seas have subsided to 4 feet or less. The Small Craft Advisory for the NC
waters north of Currituck Beach Light remains in effect until 7 am
hi pressure will weaken and slide to the south-southeast of the area tonight...as a
cold front sags into extreme northern areas by sun morng. The front will
sink down through the region during sun...with winds becoming north-northeast 5
to 15 knots all areas. By Monday morng...hi pressure will build from southeast Canada
into New England...then slides off the CST by Monday eveng. This will
result in stronger north-northeast winds of 10 to 20 knots...and seas bldng back
to 5-6 feet. Sca's will be likely again starting late Sun night or
early Monday morng at least for the mouth of the ches Bay and the
coastal waters. The wedging hi retreats on Tuesday...as strong low pressure
lifts into Wisconsin and pushes a cold front eastward into the mountains
that front will then approach Tuesday night...then move across the area
and off the CST Wednesday into Wednesday night. Strong northwest or north winds then
expected Wednesday night through Thursday...as cool hi pressure builds in behind the
Marine...Small Craft Advisory until 7 am EST this morning for anz658.