Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Wakefield Virginia
724 am EST Monday Jan 26 2015
low pressure over southwest Virginia early this morning will
weaken this morning...while a new low pressure system will
develop off the North Carolina coast by early this afternoon.
This low will then rapidly intensify as it tracks north northeast
off the middle Atlantic and New England coasts this afternoon through
Tuesday. The low will move away to the northeast Tuesday night and
Wednesday...as high pressure builds in from the northwest.
Near term /until 6 PM this evening/...
early this morng...area of rain was moving into western and northern
counties in advance of surface low over SW Virginia and upper trough pushing across
the mountains the low will weaken this morng...while a new low pressure
system will develop off the NC CST by early this afternoon. That low
will then rapidly intensify off the middle Atlantic CST into this eveng.
Combination of the surface low re-development and upper trough swinging
across the region will result in chances for rain today into this
eveng. Highest probability of precipitation (60-80%) will be over the northern half of the area
where best lift will be...with 30-40% probability of precipitation over the southern half. Temperatures
will warm a bit into early afternoon despite cloud cover...possible
precipitation as winds will be generally from the east. Hi temperatures will range from
the lower 40s northwest to the middle 50s over NE NC.
Short term /6 PM this evening through Wednesday/...
will favor a blend of the 12z NAM/European model (ecmwf) for this period. The main
event for our area begins tonight into Tuesday morng...as colder air
plunges S in response to rapid intensification of the surface low off
the middle Atlantic and southern New England CST. Still mainly rain across the
southern 2/3 of the County Warning Area in the evening...then transitioning to all snow
between 00z-09z from northwest to southeast. During this time...best lift/frontogenesis
will reside off the CST or NE of our County Warning Area. However...will be
relying on deformation zone and possible banding development from
the Delaware-Maryland-Virginia to Long Island to "wrap around" and drop S over the
lower Maryland eastern shr...and portions of central and eastern Virginia from this eveng
through Tuesday morng. Thus...based on the above reasoning and wpc
forecasts...have issued winter weather advisories for most of the County Warning Area with
the exception of SW counties of scntrl Virginia and all of NE NC
counties. Generally...advsys will run from 8pm-1am this eveng/tonight
to 8am-noon Tuesday. Any change in the position of the banding can have
drastic effects on snow amounts...so uncertainty still remains
rather high. For now...have forecast 2-4" of snow on the lower Maryland
eastern shr...with 1-3" across Northern Neck/Virginia eastern shr...1-2" across the eastern
Virginia Piedmont/central Virginia including ric metropolitan and Tri-Cities...then
tapered to 1" or less over scntrl Virginia and southeast Virginia including Hampton
rds and the Tidewater area.
Snow is expected to taper off and end late Tuesday morng/aftn...but
if 00z European model (ecmwf) is correct...this would be slower and additional
snow amounts may need to be added...esply over the lower Maryland eastern shr.
Lows tonight in the upper 20s to middle 30s...highs on Tuesday ranging from the
middle 30s to lower 40s. Clearing/cold Tuesday night/Wednesday with lows in the
20s and highs on Wednesday ranging from the Lower/Middle 40s SW to the Lower/Middle
Long term /Wednesday night through Sunday/...
long term period will feature below normal temperatures with dry weather most
days. For Wednesday night...surface hi pressure builds over the middle Atlantic and southeast
states as the next low pressure systm approaches from the west. With a mostly
clear sky and light winds...temperatures will fall into the middle 20s in most
spots. Low pressure and an associated middle-level vorticity maximum will bring
precipitation (plain rain) into the area starting late Thursday. Favored the
slightly slower European model (ecmwf) solution...with a 30% chance of precipitation (ra/snow
north and rain south) Thursday night...with low temperatures in the low to middle 30s.
Conds then dry out into Friday and Sat as surface hi pressure builds in from the west.
Expect a prtly cloudy sky both days with northwest winds and hi temperatures
falling from the 40s on Friday to the middle 30s to lower 40s on Sat.
Aviation /12z Monday through Friday/...
as of 724 am EST...VFR conditions across area terminals
deteriorate through the taf period. Cloud bases will lower to MVFR
first over ric/sby through 15z...then by late morning/afternoon over
phf/orf/ecg. Light rain is forecast to develop mainly at ric this
morning...with vcsh wording at sby by late morning. Went ahead and
lowered sby to IFR after 18z through the rest of the taf period. Blended
current probability of precipitation with some of the guidance for starting times of precipitation.
Ceilings and visibilities lower to MVFR and in some cases IFR during the afternoon
except at ecg. The lowest conditions for this taf period and
beyond appear to be lining up for sby where NE winds will also
Outlook...rain changes to snow during the late evening hours
Monday into early morning hours of Tuesday (02-06z/tuesday) and
continues trough midday Tuesday. Snow may be heavy at times at
sby through Tuesday morning where accumulating snowfallis
currently forecast. Elsewhere, a light accumulation of snowfall is
expected at ric/phf/orf with only a trace amts of snow expected at
ecg. IFR conditions are expected by late afternoon and through the
evening at sby and will continue overnight Monday especially during
periods of accumulating snow. IFR conds will be possible Monday
night at phf/orf/ecg, mainly towards the end of the taf period and
into Tuesday morning.
Dry and mainly VFR conds are expected during the rest of the week.
There will be a chance for precipitation late in the week mainly on Thursday
gale watch headline has been converted to small carft advisory through
Wed, with Gale Warning remaining in effect for northern coastal
waters. East-southeast flow over the waters will back to the east-NE early this
morning and evenuallt to the northwest later today. Surface low will
redevelop off the Carolina CST late today, and will intensify as
it slowly lifts NE into tonight. High confidence for gales
continues over northern zones on the back side of the rapidly
deepening surface low. Sca's over remaindr of the waters as flow
becomes northwest and increases to 20-25kt. Rapid ramp up of winds will
quickly build seas to 6-9 feet south and 8-10 feet north, west/ at least
12 feet out 20nm over northern coastal waters. Waves in the ches Bay up to
5-6 feet late tonight/Tuesday morning. Northwest flow and low end Small Craft Advisory conds
look to continue into Wednesday morning as surface hi pressure slowly builds in
from the west. Sub-Small Craft Advisory conds then for Wednesday night/Thu.
low pressure intensifies rapidly off the middle-Atlantic coast
tonight night/Tuesday. The result will be a period of strong northerly
winds over the waters. Tidal anomalies are expected to reach 1 to
1.5 feet...possibly higher...during Monday night and Tuesday
mornings high tide cycles. Sites in the Lower Bay will reach
highest astro tide with water levels approaching minor flooding
thresholds at Sewells Point tonight. For Ocean City...minor
flooding is expected with new guidance indicating an increased
chance for moderate. Have gone ahead with coastal Flood Watch for
Worcester County in vicinity of Ocean City for tonight. This will give the day
crew one more opportunity to peruse latest guidance and either go
with advisory or upgrade to warning later today. Another period of
high anomalies are expected again Tuesday...before anomalies drop
off Tuesday night/Wednesday as the low lifts away from the region.
Maryland...Winter Weather Advisory from 10 PM this evening to noon EST
Tuesday for mdz021>025.
Coastal Flood Watch from this evening through late tonight for
Virginia...Winter Weather Advisory from 11 PM this evening to noon EST
Tuesday for vaz080-081-087>090-092-093.
Winter Weather Advisory from 8 PM this evening to 8 am EST
Tuesday for vaz048-049-061-062-068-069.
Winter Weather Advisory from 1 am to noon EST Tuesday for
Winter Weather Advisory from 10 PM this evening to noon EST
Tuesday for vaz073>078-084>086-099-100.
Winter Weather Advisory from 8 PM this evening to noon EST
Tuesday for vaz063-064-070>072-082-083.
Marine...Small Craft Advisory from 4 PM this afternoon to 6 PM EST
Wednesday for anz630>634-654-656-658.
Gale Warning from 4 PM this afternoon to 10 PM EST Tuesday for
Small Craft Advisory from 4 PM this afternoon to noon EST
Wednesday for anz635>638.