Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Wakefield Virginia
1023 PM EST Friday Dec 26 2014
high pressure will slowly drift offshore tonight into Saturday.
Low pressure tracks northeast through the Tennessee Valley
Saturday night and across the middle Atlantic Sunday as a cold front
approaches from the northwest. This cold front drops through the
region Sunday night. Another area of low pressure tracks along the
front and crosses the region Sunday night...before moving off the
Near term /until 6 am Saturday morning/...
scattered-broken cirrus flowing around the periphery of an upper level high
pressure centered over the Caribbean will stream across the middle
Atlantic region from west to east tonight. As the upper level high
shifts eastward overnight...the cirrus will shift more to the east and
south from its most current position generally along and south of
Interstate 64. Made additional adjustments to sky cover with only
partly cloudy wording in forecast per this expected trend.
Overall...the cirrus should have minimal impact on falling temperatures
tonight. Still expecting lows around 30 inland and in the
middle-upper 30s for southeast Virginia/NE NC coastal locations.
Short term /6 am Saturday morning through Monday/...
high pressure slowly drifts offshore Saturday. Limited mixing and
a light SW wind is expected once again Saturday, though will be
partially offset by warming aloft. This should yield maxima about
a category warmer than those of today, or upper 50s to low 60s
inland, middle to upper 50s coastal zones and the lower Eastern Shore.
Grids will average out sunny to mostly sunny, though we'll begin
to see some lowering middle to high clouds late in the day and Sat
night as low pressure tracks through the Tennessee Valley and a
cold front approaches from the northwest. Lows Sat night mainly in the 40s
under a mostly cloudy to overcast sky.
Model guidance continues to be a bit slower with the frontal
boundary, which approaches the region from the Tennessee Valley late Sat
through Sunday, dropping south across the region later Sunday
through Monday. Have increased pop into chance range late Sat
night/Sunday morning with initial batch of overrunning moisture
lifting north across the area, with rain remaining likely for
much of the region, especially north/central sections of the area
Sunday afternoon. For that reason, have bumped pop into 50-60%
range across the north, tapering back to 30-40% south. Highs
Sunday in the middle 50s to low 60s.
Probability of precipitation increase to likely range for most of our area Sunday night.
Main shortwave ejecting east across the middle-south will interact
with the cold front as it slowly drops south across the region and
into the Carolinas early Monday. Deterministic models all handle
shortwave energy a little bit differently. CMC is a bit more
amplified than either the 12z/26 European model (ecmwf) or GFS. However, all models
are close in depicting best forcing/upper support sliding across
the local area Sunday night. Quantitative precipitation forecast on the order of between a half
and three-quarters of an inch Sunday night and early Monday. Kept
lows on the mild side with ongoing clouds/pcpn...in the low 40s
northwest to lower 50s southeast coastal plain. Surface low slips offshore Monday
afternoon and evening, with surface front dropping south of the area
late in the day. Probability of precipitation ramp downward through the day, with
lingering showers over the east diminishing by sunset. Clearing
will likely be delayed with onshore flow persisting at low levels
Monday aftn/eve. However, temperatures will get off to a mild start
across the south. This combined with shallow mixing will result in
a rather shallow diurnal curve, west/highs only in the middle 40s north
to middle 50s south, under a mostly cloudy to overcast sky.
Long term /Monday night through Friday/...
GFS/European model (ecmwf) in good agreement through day 6 /next Thursday/ with
regard to overall pattern. A cold zonal flow will prevail aloft
across the region...with high pressure building into and across the
area from Monday night through Thursday of next week. Weather is
expected to be dry with temperatures at or a bit below normal for
late December. Low temperatures Monday night in the 30s...then in the 25 to
30 degree range /a bit warmer near the coast/ Tuesday night
through Thursday night. High temperatures Tuesday through Thursday in the
GFS/European model (ecmwf) diverge a bit going into next Friday...with GFS faster and
further south with low pressure and associated frontal system moving
east-northeast/northeastward out of the plains/MS valley. Regardless...Friday into
Saturday next week look to be unsettled...with temperatures warming
to near normal for high temperatures on Friday.
Aviation /03z Saturday through Wednesday/...
high pressure centered over the region is providing VFR conditions
area wide and it is expected to remain in control of the regions
weather through the day on Saturday as is slowly slides off the
Carolina coast. Some high level moisture is stream northeast from
the lower MS valley into southern New England and could produce some
broken cirrus for ric/phf/sby...but otherwise little more than
scattered cirrus is expected. The only potential restriction could
be some ground fog at phf as temperature/dew point depressions are
already at 6 degrees and the sensor did report a short period of
IFR fog last night. Mostly like this would be a short temporary
condition so will not include in this taf issuance...but could
need to add it for the next forecast cycle.
Outlook...a cold front approaches from the northwest Saturday
night and Sunday. This along with associated low pressure system
moving through the Carolinas will bring widespread rain and
periods of IFR Sunday through Monday. The weather improves for
Tuesday and Wednesday as high pressure builds back into the Middle
fairly tranquil conditions expected on the marine area through
Sunday...as high pressure prevails over or just east of the area.
Winds over the weekend expected to generally be 10 kts or less...
with seas 2 feet or less and waves 1 to 2 feet on the Bay. Next
frontal system approaches the area late Sunday...and crosses the
area on Monday. This front will bring a wind shift to the
north...although all models suggest the surge will remain below
Small Craft Advisory criteria. However...wind speeds in the 10 to 15 knots range will
make for choppy conditions on both the Bay and ocean from later
Sunday night through Tuesday.
kdox 88d radar is expected to be out of service through at least
Wednesday 12/31. See ftmdox (free text message) for details.