Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Wakefield Virginia
432 PM EDT Wednesday Mar 12 2014
a strong cold front will push across the area and off the coast
this evening into tonight. High pressure will build into the
region during Thursday...then slides out to sea during Friday.
A weak cold front will drop through the area Saturday night into
Sunday morning. Low pressure will track from the Gulf Coast states
northeast and off the North Carolina coast Sunday through Monday.
Near term /until 6 am Thursday morning/...
late this afternoon...latest akq radar and surrounding radars indicated
an area of showers moving through portions of eastern Virginia and the lower Maryland
eastern shr. While...the leading edge of a line of showers and isolated
thunderstorms in advance of the cold front was extending from scntrl PA south-southwest
through extreme western Virginia...and into western NC. The RUC/GFS/hrrr have this
line of showers/isolated storms pushing across our County Warning Area from around 5 PM to
around 10 PM. Thus...will have likely probability of precipitation (60) through this time
period...with rainfall amts of around .10 inch or less expected. Any
heavier showers could produce a bit more rainfall and contain
gusty winds. The entire forecast area is in a slight risk for severe weather through this
eveng...with isolated damaging winds the main threat. But...limiting
factors will be the lack of instability and lack of convergence
ahead of/along the cold front (with deep layered low level winds - to
about 5kft - from the SW parallel to the cold front crossing the fa).
Cold front moves off the CST around or shortly aftr midngt...with
intensifying low pressure moving NE toward the Canadian Maritimes by Thursday
morng. This will result in very strong northwest winds ushering a much
drier and colder airmass into the region. Gusts to 45 to 50 miles per hour
will be possible...esply over eastern/NE portions of the area. Have
thus issued a Wind Advisory for those locations from later this
eveng into Thursday morng. Under a clearing sky...lows tonight will range
from the middle 20s to middle 30s.
Short term /6 am Thursday morning through Saturday/...
hi pressure will build toward the region during Thursday...then slides out to
sea during Friday. Sunny/mostly sunny and very chilly on Thursday with hi
temperatures only ranging from the upper 30s to lower 40s. Clear/mostly clear
and cold Thursday night with min temperatures ranging from the upper teens to middle 20s.
Mostly sunny on Friday...with south-southwest winds 10 to 15 miles per hour helping temperatures
to rebound into the upper 40s to upper 50s.
Maintaining dry weather Friday night and Sat. A weak cold front will
approach from the northwest late Sat. Mostly clear to partly cloudy with
lows Friday night in the middle 30s to near 40...and highs on Sat in the
lower to middle 60s.
Long term /Saturday night through Wednesday/...
a cold front sags through the middle Atlantic region Saturday night.
Low pressure develops in vicinity of the NC coast Sunday and pulls
offshore Sunday night. Secondary low pressure forms along the
southeast coast Sunday night and pulls offshore Monday/Monday night.
Spatial timing differences exist between GFS/ECMWF...but overall
agree on this general pattern. The best precipitation potential at
this time is from Sunday through Monday evening. In general...rain
is expected. However...there is a potential of a mix of rain/snow across
the far northern counties Sunday night...and again Monday evening
across the northwest half of the area as precipitation ends. High
temperatures should generally be below normal...with
clouds/precipitation and cool high pressure to the north. Weak high
pressure briefly builds over the region late Monday
night/Tuesday...before moving offshore midweek. This should bring a
moderating trend along with dry conditions as SW flow prevails.
Aviation /20z Wednesday through Monday/...
area of light showers currently affecting kric/sby with will pull
off to the NE through 21z...while a line of heavier showers with
embedded thunderstorms over eastern WV will push through the local area
between about 21/22z and 01/02z this evening. Did not include
thunderstorms with the taf issuance...but did have a tempo group for
low MVFR to IFR visibilities with heavier showers possible. Gusty SW
winds will average 15-25 knots this evening (brief higher gusts possible
in any convection).
Winds abruptly shift to the northwest between 01-04z...and will be quite
strong (especially at ksby) where tafs have g40 knots. Elsewhere have
gusts to 30-35kt. Skies clear out and VFR conditions prevail Thursday
with winds still remaining gusty to 25-35kt through the day. Dry/VFR
weather prevails Thursday through Sunday...with a chance of rain by Monday.
low pressure tracks from the northern middle Atlantic late this
afternoon to Cape Cod early Thursday morning...dragging a strong
cold front across the middle Atlantic coast this evening. Strong cold air advection
and vigorous pressure rises of ~7-10mb/3hr overspread the region in
the wake of the cold front. Given the strength of the cold air advection/pressure
rises gale warnings are in effect for the entire marine area. The
wind will be strongest over the Ocean/Bay (30-35kt gusts up to
45kt)...with 25-30kt gusts up to 40kt over the sound/rivers. Seas
are expected to reach 7-9ft out near 20nm...with 4-5ft
nearshore...and 4-5ft waves. Cold air advection continues through the day Thursday.
Ocean Bay/gale warnings remain through Thursday evening...while the
sound/rivers run through Thursday morning. All gale flags will
likely need to be replaced with scas. High pressure settles over the
southeast coast by Thursday night and shifts offshore Friday. A
modest pressure gradient develops over the region Friday
afternoon/evening...so a period of marginal Small Craft Advisory conditions are
possible over the Bay/northern ocean zones. The gradient relaxes later
Friday night into Saturday as a cold front slowly approaches from
the north. This front sags through the region north-S Saturday night into
Sunday. Low pressure develops along the boundary Sunday night into
Monday. This has the potential to produce a strong north-northeast wind and
a strong cold front will move through the area this evening. In
the wake of this front...very dry air is expected to infiltrate
the region on Thursday. The combination of gusty northwest winds and
relative humidity values dipping as low as 10%-15% will greatly
enhance the threat for wildfires spreading out of control. Despite
recent rainfall...the finer fuels have dried out sufficiently to
support rapid fire growth potential. One limiting factor will be
the unseasonably cold temperatures forecast on Thursday (highs
only in the upper 30s across the lower Maryland Eastern Shore to the
middle 40s in NE nc). After coordination with state forestry
officials...have gone ahead and issued a Fire Weather Watch for all of
our Virginia and NE NC counties for Thursday. Due to colder temperatures over
Maryland...will not go with a watch at this time in favor of eventually putting
out an enhanced Fire Danger Statement (sps) early Thursday
morning. Depending on how much rain falls with the frontal passage
this evening (or lack thereof)...will likely upgrade to a red flag
warning for Virginia and NC this evening.
Maryland...Wind Advisory until 11 am EDT Thursday for mdz021>025.
NC...Wind Advisory until 11 am EDT Thursday for ncz102.
Fire Weather Watch from Thursday morning through Thursday
afternoon for ncz012>017-030>032-102.
Virginia...Fire Weather Watch from Thursday morning through Thursday
afternoon for vaz048-049-060>100.
Wind Advisory until 11 am EDT Thursday for vaz075>078-085-086-
Marine...Gale Warning until 8 PM EDT Thursday for anz630>632-634-650-
Gale Warning until 7 am EDT Thursday for anz633-635>638.