Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Wakefield Virginia
840 PM EST Sat Dec 27 2014
high pressure will drift farther eastward off the Carolina coast
tonight as a cold front over the Ohio Valley slowly moves towards
the middle Atlantic region tonight and Sunday. Weak low pressure will
develop along the front and enhance the chance for rain Sunday
into Monday. The front will move offshore on Monday but low
pressure to the south will keep clouds and a chance of rain over
the area into early Tuesday.
Near term /until 6 am Sunday morning/...
dry conditions continue through this evening. High pressure slowly
drifting off the Carolina coast remains in control and looks to
hold precipitation off until after daybreak Sunday. There remains
a lot of middle to high level cloud cover west of the mountains and
this will start to make its way east overnight...thickening as it
does. Expect partly cloudy skies this evening...becoming cloudy by
early Sunday morning. With the increasing clouds and light south
winds around 5-10 miles per hour...expect milder overnight temperatures in the
low to middle 40s.
Short term /6 am Sunday morning through Tuesday/...
while models agree on the overall pattern and timing of the
perturbations in the SW flow...handling of the best upper level
divergence differs just enough to make exact timing of
precipitation tricky from Sunday through early Monday. A cold
front drops into the area Sunday as a weak wave of low pressure
lifts NE along the front and over the region late Sunday morning
through the afternoon. With increasing deep moisture in the southwesterly
flow and plenty of isentropic lift present...the result will be
widespread precipitation with periods of moderate rainfall spreading SW
to NE across the region through the day Sunday. Best chances appear
to be across the western and northern portions of the forecast area and
perhaps as far south as central Virginia. Have kept likely probability of precipitation in the
forecast, but probability of precipitation may eventually be raised to categorical once
the exact track of the best precipitation is known. Highs sun in the middle
to upper 50s inland to low 60s southeast where rain begins later in the
day. This initial wave of precipitation lifts through the area Sun
afternoon allowing for a break in the widespread rainfall Sunday
The front stalls just off the middle-Atlantic coast and extends southeast
into the Carolinas as southwesterly flow and deep moisture continues. The
lull in precipitation sun evening will be short-lived as the next
shortwave deamplifies and lifts into the region late Sun night
into Monday morning. A stronger surface low develops along the
front...lifting into NC early Monday morning. Another round of
widespread precipitation is expected late Sun night into Monday. This round
of precipitation should be more focused over the southern half of the area
across south central and southeast Virginia as well as NE NC. Models are
in slightly better agreement...now lingering moisture over the
area into Monday evening. Maintained chance probability of precipitation through Monday afternoon
and evening. Highs Monday range from the middle 40s in the north to near 50
in the S.
Upper jet and additional shortwave energy lifts into the region
Monday night into Tuesday...providing additional uvm. Remnant low level
moisture will result in additional light precipitation Monday night into Tuesday
morning. Temperature profiles expected to remain above freezing through Tuesday
morning...as the best cold air advection arrives as precipitation pushes offshore late
Monday night. Have maintained slight chance probability of precipitation through Tuesday morning to
account for potential wraparound moisture. Lows Monday night in the
middle to upper 30s with highs Tuesday only in the low to middle 40s.
Long term /Tuesday night through Saturday/...
GFS/European model (ecmwf) remain in good agreement Tuesday night through the
daytime hours on Friday with regard to overall pattern. A cold
zonal flow will prevail aloft across the region
Wednesday/Thursday...with high pressure building into and across
the area. Weather is expected to be dry with temperatures at or
slightly below normal for late December. Low temperatures Tuesday night
and Wednesday night around 25-30 degrees...a bit warmer near the
coast. Lows Thursday night in the upper 20s northwest to the low-middle
30s southeast...with min temperatures expected to occur before 06z...as clouds
increase overnight. High temperatures Tuesday through Thursday in the
40s...and in the 40s all areas Friday (except southeast Virginia/NE NC where
50s look likely).
GFS/European model (ecmwf) continue to diverge from next Friday night through
Saturday night with regard to timing of low pressure and associated
complex frontal system. GFS remains 12-18 hours faster than
European model (ecmwf) which develops a wave along the front Saturday
night...delaying the frontal passage until Sunday. Regardless...
Friday night into Saturday night next week looks to be unsettled
with clouds and showers. However...temperatures will warm to
above normal on Saturday with many areas potentially in the 60s.
Aviation /02z Sunday through Thursday/...
VFR conds occurring across the region with mostly high clouds
beginning to overspread the area from the s=sw. Winds are
generally light from the south less than 5 knots. A cold front will
approach the middle Atlantic region during the overnight. Clouds will
increase and thicken tonight and rain is expected to occur across
the County Warning Area before noon on Sunday. At this time...expect VFR conds to
persist into the afternoon/evening with ceilings lowering to 035-060 kft
across the region and visibility 3-5 Michigan in rain and fog.
Outlook...steady rain moves into the region during the evening
Sunday with periods of MVFR and tempo IFR conds Sunday night and
Monday morning. A lull in the precipitation is expected Monday
aftn/evening. Low pressure moving along the front to the south
will bring another round of rain and possible IFR conds Monday night
into Tuesday. VFR and dry weather are expected Wednesday and
fairly tranquil conditions expected on the marine area through
Sunday...as high pressure prevails along/just off the Virginia/NC coast.
Some increase in winds likely tonight/early sun...with speeds in the
10-15 knots range. Next frontal system approaches the area late
Sunday...and crosses the area Sunday night/Monday morning. Winds
gradually drop off ahead of the front on Sunday...but are expected
to increase out of the north/NE on Monday. Models have come into line
with earlier forecast reasoning...and are now indicating a stronger
surge...with wind speeds near Small Craft Advisory criteria possible Monday/Monday
night. Also expect that seas will eventually build to 5 feet over at
least the southern coastal waters late Monday-Tuesday in north/NE flow of
15-20 knots. May need some Small Craft Advisory headlines during that timeframe. Surface
high pressure slowly builds into the area by midweek...with
kdox 88d radar is expected to be out of service through at least
Wednesday 12/31. See ftmdox (free text message) for details.