Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Wakefield Virginia
1008 am EDT Friday Oct 31 2014
weak high pressure builds across the area today. A strong low
pressure system will develop off the middle Atlantic coast Saturday
and Saturday night before exiting the area on Sunday. High
pressure returns for the beginning of next week.
Near term /until 6 PM this evening/...
quick update to forecast to increases cloudiness this morning across central/eastern
portions of forecast area.
middle-morning surface analysis shows very weak hi pressure in vicinity of central mountains...W/
a lingering frontal boundary off the CST...and a progressive baroclinic
wave tracking along the boundary. Also...one short wave aloft moving
through the lower Ohio Valley...and a 2nd (stronger) one diving southeast
through the western lakes states.
Today begins cool and mcldy (w/ exception of the far SW
piedmont)...with a clearing line tracking from south-southwest-north-northeast as the low
pulls farther NE. Initial short wave carves out trough into interior southeast
Continental U.S. States and awaits arrival of the 2nd short wave from the north-northwest. Very weak
surface hi pressure remains in place long enough for a mainly dry day across the
forecast area. Combo of system east and west of the forecast area will result in vrb clouds to
pcldy conds most places this afternoon. Will have slight chance to low end
chance probability of precipitation right along the immediate CST in southeast Virginia/NE NC this afternoon as
the surface low tracks off the CST. Hi temperatures from the u50s north-northwest to 60 to
Short term /6 PM this evening through Sunday/...
strong short wave will continue to dig south from the Tennessee Valley across
the deep south tonight...then through the Carolinas on Sat. Continued
good model agreement depicting upper low closing off over the
Carolinas midday Sat. Models continue to spin-up secondary
cyclogenesis offshore of the NC coast Sat aftn/eve...before
quickly ejecting northeast away from the area late Sat night into
Sunday morning. Cool 1030+mb high pressure will settle east from
the Mississippi Valley late Saturday through Monday.
00z/31 suite of models remain in good agreement that rain will
increase in coverage late tonight through Saturday. Breezy overall
on Saturday...with best surge of cold air advection likely holding off until Sat
night. Given forecast of how far S upper level system tracks...most significant
impacts (both wind and ra) Apr to be over for eastern/southeastern coastal
locations (primarily) from midday Sat into early Sat evening.
Additionally, a period of strong north-northeast winds (35-45 mph) expected
along coastal zones west/areas of minor tidal flooding along the Atlantic
beaches and lower ches Bay (see coastal flooding section blo). Will
continue to highlight potential impacts in severe weather potential statement. A Wind Advisory may be
needed over at least some of our coastal zones Sat night for a 6-10
hour period if current forecast rationale pans out.
Precipitation will taper off Sat night west/ subsidence in the wake of the
departing wave...and sky clears out quickly into Sunday morning as
surface high of Canadian origin sinks from the Ohio Valley into
the southeast beginning Sunday. This will usher in the coolest air
of the season to date.
With respect to quantitative precipitation forecast...most inland places may have average amounts less than 0.25
in...W/ higher amounts (to 0.50 to possibly 0.75 in) mainly confined to
close to the CST.
For temperatures...widespread clouds and increasing rain chances
will keep highs in the 50s for most on Saturday...though temperatures may
not make it out of the 40s well inland. Well mixed atmos/breezy-
windy conds will keep temperatures from bottoming out Saturday
night...but still chilly with low temperatures in the middle 30s inland to
low 40s along the coast. Despite a mostly sunny sky...ongoing low
level cold air advection will keep highs Sunday in the 50s...or roughly -1 to -1.5
Standard dev from climatology.
Long term /Sunday night through Thursday/...
strong high pressure settles over the middle Atlantic Sunday night. By
Monday morning lows should fall to around 30-32 for much of the
area (upper 20s possible in favored cold spots)...with slightly
higher values (35-40) for far southeast portions. This has the potential to
produce the first widespread freezing temperatures this fall across
the local area. A slow moderating trend is expected Monday through
Wednesday as the high gradually moves offshore. Highs Monday should
range from 55-60...with middle/upper 60s possible by Tuesday and
Wednesday. Overnight lows should remain rather cool Tuesday morning
ranging from the low/middle 30s interior to low 40s for southeast coastal
locations. Lows should moderate into the middle 40s/low 50s Wednesday
morning with the high well offshore and the resumption of south-southwest flow.
The next cold front approaches from the northwest Wednesday/Wednesday
night...and tracks through the middle Atlantic Wednesday
night/Thursday. At this time moisture appears rather limited with
this front...so only slight chance probability of precipitation are included at the end of the
Aviation /14z Friday through Tuesday/...
mainly VFR conditions will prevail today as a weak area of high
pressure persists over the area. The high dissipates over the
region this afternoon while setting up a weak wedge that...due to the
resulting NE flow...may cause some MVFR ceilings to occur at
korf/kphf/kecg this afternoon and evening. Also today...a weak
area of low pressure will develop along a stalled frontal boundary
off the Carolina coast. Increasing moisture along with a few
showers may impact the NE NC/southeast Virginia coast...but rain chances are
too low at this time to include mention in the tafs.
Strong upper level system will move across the Ohio and then Tennessee
River valleys into Sat. This system will help form a strong
coastal system off the Outer Banks late Sat into sun. As this
system deepens and moves off the coast...20-30 knots north winds with
higher gusts will be possible from Sat night through Sun afternoon.
gale watches Sat night have been upgraded to warnings following
increased confidence and coordination with neighboring offices. For
today...NE winds up to ~15 knots expected as low pressure develops off the southeast
CST. Though not likely...will have to monitor for the potential of
Small Craft Advisory conditions over the Bay. Winds become northerly tonight with similar speeds
as the low passes offshore and another low pressure center develops near
the NC/SC CST. On Sat...winds/waves/seas increase as that second
area of low pressure strengthens off the NC CST in response to a very
potent middle-level shortwave trough. Maintained the Small Craft Advisory over northern coastal
waters before the gale as a period of 5 feet seas is expected
there...while conditions elsewhere will ramp up fast enough to just
warrant a gale headline. Conditions over the rivers other than the
lower James are expected to stay sub-gale so a Small Craft Advisory has been issued
there. Brief winds close to storm force are possible over southern coastal
waters...but with the speed and track of the surface low...expect winds to
stay mainly in the gale range. Strongest winds over the
Bay/sound/cstl waters (30-40 knots sustained with gusts to 40-45 kt) will
occur Sat night...and slowly diminish on sun as the low pulls well NE
of the area. Expect 4-6 feet waves over the Bay and seas over coastal waters
up to 10-12 feet. Hi pressure builds over the area Sun night and Monday and then
slowly moves offshore Erly to middle next week...with sub-Small Craft Advisory
low pressure is expected to rapidly strengthen off the coast late
Saturday afternoon and Saturday night. Tidal departures of 1-1.5 feet
above normal are possible Saturday night along the Atlantic coast
and Lower Bay. Minor tidal flooding is expected for these locations
if the surge coincides with the high tide cycle Saturday night.
Marine...Small Craft Advisory from 1 PM EDT Saturday to 4 PM EST Sunday
Gale Warning from 4 PM EDT Saturday to 7 am EST Sunday for
Gale Warning from 4 PM EDT Saturday to 10 am EST Sunday for
Small Craft Advisory from 7 am to 4 PM EDT Saturday for anz650-