Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

fxus61 kakq 232007 
afdakq

Area forecast discussion
National Weather Service Wakefield Virginia
407 PM EDT Thu Mar 23 2017

Synopsis...
Canadian high pressure overhead will slowly slide offshore
tonight and shift farther eastward on Friday. A gradual warming
trend then begins Friday through the upcoming weekend. A more
active weather pattern is anticipated Sunday night into the
first half of next week.

&&

Near term /until 6 am Friday morning/...
Canadian sfc high pressure sits overhead late this aftn and is
expected to slowly drift offshore tonight. Continued clear skies
overnight with light onshore winds. Lows below freezing inland
areas/Maryland lower Eastern Shore (28-31f) and in the mid 30s far
southeast Virginia/NE NC coastal areas.

&&

Short term /6 am Friday morning through Sunday/...
dry with a gradual warming trend Fri through Sat as Canadian
high pressure continues to push ewd/offshore. A warm front lifts
northwest of the area overnight...allowing warm air advection to
commence on Fri with winds becoming more S-SW. Temperatures are
expected to rebound to readings at to slightly above normal due
to breezy SW winds gusting to around 20-25 mph inland Virginia/NE NC
and up to 25-30 mph Maryland/Virginia Eastern Shore. Expect highs in the
mid 60s most inland areas (mid 50s to lower 60s beaches and
Maryland/Virginia eastern shore). Overall conditions will be dry as
mid-upper level ridging and decent subsidence aloft dominates
(i.E. Best shower chances are along/north of the Mason-Dixon
line invof the warm front). Otherwise, mid-high clouds should
stream across the region (especially north) within relatively
flat, upper level flow through Fri night. Lows around 50f.

Meanwhile, low pressure exits the intermountain west Fri and
tracks into the wrn Midwest Fri night. As the low struggles to
cross the mid-Mississippi Valley Sat/Sat night, a secondary warm
front extending from the low is expected to lift north through
the area Sat aftn. This will allow for additional warming in
continued SW sfc winds and a noticeable influx of moisture as
dewpoints increase to around 50f. Although clouds should clear
out briefly across the southeast half of the area during the day (as is
typical with a warm frontal passage), aftn cumulus development
and increasing cirrus from the west will keep partly sunny
wording in the forecast...mostly cloudy far nrn counties invof
the warm front. Maintained highs for Sat in the in the mid 70s
inland (upper 60s to lower 70s beaches). Continued warm Sat
night with lows running about 10-15 degrees above normal. Lows
in the lower 50s most areas (upper 40s possible Atlantic beaches
of Maryland/Virginia eastern shore).

Weakening sfc low in the Great Lakes finally gets kicked east-northeast by
another low pressure system exiting the intermountain west on
sun. Negative tilting of the mid-upper lows will slow the
advancing (and weakening) sfc cold front associated with the
Great Lakes low. This will also slow the arrival of incoming
precip into the eastern Piedmont until late sun aftn (or even
possibly not arriving until early evening). High temps expected
to reach the lower 70s most inland areas (60s beaches). A
combination of instability parameters are not lining up for
favorable/widespread thunderstorm development sun aftn/early
evening. Best factors to overcome the meager instability will be
the presence of weak seabreeze boundaries with southeast-S sfc winds,
and a veering wind profile with height (albeit weak 0-6km shear
of roughly 30kt). Taking this into consideration and knowing
that the region will be well within a warm sector, cannot
completely rule out diurnally-driven thunderstorms in the aftn.
Have therefore added a slight chance for thunder into the
forecast.

&&

Long term /Sunday night through Thursday/...
medium range period features a mild period, courtesy of surface
high pressure oriented just off the mid-Atlantic/southeast
coast. Main weather features of note a couple of mid/upper level
lows, which will bring scattered light precipitation late in the
weekend and again by Tuesday. The first of these disturbances
traverses across the central/Southern Plains on Saturday,
dampening as it crosses east- NE into the Ohio Valley and eastern
Great Lakes on Sunday and into the northeast on Monday. This
feature will allow for some isolated to scattered showers Sunday
night into early on Monday. Quantitative precipitation forecast will be limited with this
feature. Despite increasing precipitable water values, minimal instability and
steadily weakening dynamics/forcing remain maximized well off
to our N-NW. Therefore, high end chc to likely pop is in place
for Sunday night over our western/northwest tier of the area for
sct/numerous showers. Region remains mild in the warm sector
with southerly flow bringing highs in the upper 50s to 60s
Northern Neck and Maryland lower Eastern Shore...with upper 60s to
low 70s inland for early next week.

For the middle of next week...attention turns to a second
southern stream disturbance, which is expected to track
east/northeastward from the California coast...across the plains and
mid-south late Sat-early Monday. There remains some significant
disagreement with the GFS/ECMWF, with the European model (ecmwf) and its member
ensembles remaining more progressive and flatter. Will lean in
the European model (ecmwf) direction with the GFS parallel and gefs seemingly
trending in this quicker direction as well. Still, this system
will be a bit stronger than the weekend system but it too will
weaken as it pushes across the eastern third of the conus Monday
through early Tuesday. So while would translate to another
period of showers late Monday night into Tuesday afternoon,
system will again be progressive. Given the timing, will mention
slight chance of thunder Tuesday afternoon west of the Bay.
Remaining mild, with highs in the 60s to near 70 Eastern
Shore...mid 70s to near 80 south central Virginia/interior NE NC.

Shortwave ridging rebuilds behind this system for Wednesday.
Highs remain mild through the period, with 50s and 60s over the
Northern Neck of Virginia into MD, with highs well into the 60s to mid
70s inland. Early morning lows mainly in the 40s to low 50s
southern sections.

&&

Aviation /19z Thursday through Tuesday/...
Canadian high pressure overhead will slowly slide offshore
tonight and shift farther eastward on Friday. Clear skies and
light, variable winds will be common areawide through tonight.
South to southwest winds on Friday become breezy with afternoon
gusts around 20-25 mph across inland Virginia/NE NC and 25-30 mph
across the Maryland/Virginia Eastern Shore. Winds are expected to diminish
around sunset Friday evening. Breezy again on Saturday, however
afternoon gusts should only average around 20 mph. A warm front
lifts northwest of the mountains late tonight and another one
lifts through the region Saturday afternoon. Although weather
conditions will be dry, mid to high level clouds may stream
across the area (especially north of kric in vicinity of the
warm fronts).

A weakening low pressure system in the Great Lakes is expected
to bring a weakening surface cold front and associated showers
to the region late Sunday afternoon into Sunday night. Isolated,
diurnally-driven thunderstorms may be possible in this
timeframe. A more active weather pattern is anticipated during
the first half of next week.

&&

Marine...
latest obs reflect northerly flow across the waters this
afternoon, with surface high pressure in place over the region.
Small Craft Advisory headlines have been dropped for all waters except for anz658
south of the Virginia/NC border to Currituck Beach Light through
23z/7pm EDT. Seas have fallen off to 2-3 ft north, 3-4 ft
central waters, and 4-5 ft across the far southern coastal
waters.



Sfc high pres slides off the coast tonight through Friday...
with winds becoming SW Fri and lingering through Sat. Pressure
gradient tightens tomorrow afternoon, with developing low
pressure over the plains. Southerly flow increasing to ~15 knots
by Friday afternoon. While nearshore winds will be elevated and
gusty tomorrow and Sat afternoons, given still cool water
temps...will undercut guidance slightly and keep waters below
any Small Craft Advisory thresholds for now. The next front crosses the waters
early next week...W/ relatively benign marine conditions
expected over the weekend in south-southwest winds mainly aob 15 kt. Seas
averaging 2-3 ft...waves 1-2 ft.

&&

Akq watches/warnings/advisories...
Maryland...none.
NC...none.
Virginia...none.
Marine...Small Craft Advisory until 4 PM EDT this afternoon for anz656-
658.

&&

$$
Synopsis...bmd
near term...bmd

National Weather Service Glossary of Abbreviations