Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Wakefield Virginia
1015 am EST Sat Nov 28 2015
high pressure shifts southward today as it slowly weakens. 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 PM this evening/...
for the rest of today...high pressure from the middle Atlantic to
southeast states will shift southward and weaken today. Meanwhile...a
cold front that stretches from northern New England to Texas will push
east and sag southward into the area later tonight. Some high clouds
continue to push in from the west resulting in periods of thickening
clouds as the day progresses. Conditions will be dry and
unseasonably warm ahead of the incoming cold front as winds shift
around to the southwest but remain light. Highs areawide will be
in the lower 70s (upper 60s immediate coast). This is about 10-15
degrees above normal for late November (or roughly 1.5 Standard dev
above normal...close to 2.0 Standard dev for Salisbury md). Record
highs are not anticipated but should come close at kric and ksby.
See climate section below for additional information.
Short term /6 PM this evening through Monday night/...
fog becomes less of an issue overnight tonight as winds remain southerly
and thickening clouds inhibit radiational cooling conditions.
Model soundings hint at the possibility of patchy fog development
across far southeast areas late tonight but confidence is not high
based on the aforementioned conditions expected. The combination
of clouds and southerly flow will result in warm overnight lows in the
lower 50s... which is roughly 15-20 degrees above normal. Record
high minimum temperatures are not anticipated.
The cold front sags southward into the region late tonight and continues
to track southward through sun...stalling over the Carolinas Sun night
into early next week. Rain is not expected to begin across
far northwest-north counties until the early morning hours on sun. As the
front drops through the area...rainfall will slowly spread southward and
become more widespread Sun night into Monday as better dynamics aloft
enhance precipitation generation. Meanwhile...high pressure slides
across southeast Canada into northern New England during this timeframe and
gradually extends down into the Middle Atlantic States. This will
create a cold air wedge down the leeside of the Appalachians and
result in additional rainfall Monday/Monday night due to warm moist air
overrunning the cooler wedge in place. Overall quantitative precipitation forecast amounts remain
fairly light (0.10 inches or less in any given 6 hour period) with
storm total rainfall averaging 0.30-0.40 inches. 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. 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
as rainfall becomes re-enhanced by overrunning/better dynamics.
Lows in the 40s inland/lower 50s along the coast.
Long term /Tuesday through Friday/...
going with a blend of the 12z GFS/European model (ecmwf) for the extended period.
There is uncertainty with the timing/passage of the cold front on
Wednesday...and how close low pressure tracks toward the southeast and middle Atlantic CST Friday
into Sat. So...cool hi pressure wedge and overrunning will result in
40%-60% probability of precipitation for rain Monday night into Tuesday night...then 30%-50% probability of precipitation for
rain or rain showers with cold front during Wednesday. Dry weather Wednesday night
and Thursday...as hi pressure builds in from the west. At this time...going in
between the GFS and European model (ecmwf) for Friday with regard to low pressure moving off
the southeast CST. So...have 30%-40% probability of precipitation mainly over southeast Virginia and NE NC.
Lows in the 40s to lower 50s Tuesday morng...in the middle 40s to lower 50s
Wednesday morng...in the upper 30s to middle 40s Thursday morng...and in the middle
30s to middle 40s Friday morng. Highs in the middle 50s to middle 60s Tuesday and
Wednesday...and in the lower to middle 50s Thursday and Friday.
Aviation /15z Saturday through Wednesday/...
early morning shallow ground fog has become very unstable in the
last couple of hours with lots of bouncing visibilities. With the
sun coming up now...should see visibilities improving over the
next hour or two with VFR conditions returning. High pressure
remains in place to begin the day....but the high should weaken
today as the cold front to the northwest...stretching from central
PA southwestward along the Ohio River into southeastern MO at 12z...slowly moves
southeastward. The front will reach sby first between 3z and 9z and
continue to move southeastward on Sunday. Ahead of the front today...expect
to see some high level clouds with light SW flow. For
tonight...should have enough mixing and clouds to keep any fog
Outlook...a cold front slides into the region Sunday before
dissipating over the Carolinas Sunday night and Monday. With cool
high pressure building into the region...a cold air damming
situation is expected to develop Monday into Tuesday. Expect
periods of rain and MVFR/IFR conditions at times Sunday night
through at least Tuesday.
the period begins with high pressure over the waters this morning.
The persistent northeast flow that has been in place most of the
week has produced a consistent swell that has had wave heights
between 4 - 6 in the coastal zones and 2 to 3 in the mouth of the
Bay. However...with the surface high reforming over the Carolinas
on Friday...the surface flow has turned more to the SW over all
the waters except for near Duck NC. As a result...the seas have
diminished some over the northern waters as buoy 9 is down to 4 to 5 feet.
As the surface high weakens today and the front to the northwest
approaches will see the winds turn more SW...but not expecting
them to increase above 10 knots. For now have kept seas around 5 feet
in the outer most portion of the coastal zones...but allowed the
nrshore waves to drop to 3 to 4 feet. So will keep the Small Craft
Advisory in place for now...but will need to monitor whether it
can be dropped early...especially for the northern coastal zones.
The cold front...which has been slowing in each model run over the
last few days should finally push across the waters late Sat night
or Sunday. Initially...not seeing much push as the surface high is
way up in eastern Canada. But by Monday...that high drops southeast into New
England and noses down the coast. This should allow the winds to
increase especially in the coastal zones to around 20 knots on Monday
and Monday night with seas getting back to around 5 - 6 feet. This
could lead to another small craft period. On the Bay and Currituck
Sound however...not anticipating Small Craft Advisory conditions...but will need to
watch the mouth of the Bay for a slight increase in seas .
The wedging high retreats on Tuesday as the strong surface low lifts
into the Great Lakes and the flow in advance of the storm becomes
SW again. The SW flow should again allow the seas to relax some as
the winds also weaken. The cold front crosses the region on
Wednesday and the winds could increase as much colder air moves
into the area.
forecast highs versus record highs for November 28:
location high high year
-------- -------- ------ ----
Richmond 72 76 1990
Salisbury 71 76 1990
Marine...Small Craft Advisory until 7 am EST Sunday for anz650-652-654-