Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

fxus61 kakq 150254 

Area forecast discussion
National Weather Service Wakefield Virginia
954 PM EST Thu Nov 14 2019

low pressure develops off the southeast coast Friday and tracks
off the Carolina coast Saturday into Sunday. Meanwhile, strong
high pressure builds north of the region from the Great Lakes to
New England this weekend.


Near term /until 6 am Friday morning/...
as of 950 PM EST Thursday...

Late this evening, a coastal boundary was along the southeast coast
with the latest radar showing showers moving up into ern NC and
scntrl Virginia. Rain showers will spread north-northeast along and inland of this
boundary into east-southeast portions of the area overnight into Fri
morning. Lows will range from the lower 30s extrm NW, to the mid
to upper 40s southeast Virginia and NE NC.


Short term /6 am Friday morning through Sunday night/...
as of 330 PM EST Thursday...

On Friday, a mid level trough begins to dig across the southern
US, meanwhile low pressure will cross northern Florida and become
better organized off the southeast coast. Precip well ahead of the
system may start to affect southern portions of the forecast
area early on Friday. Based on current forecast low temps, there
shouldn't be any p-type issues. Concern would be if any precip
makes it further north and west where colder air will still be
in place. Forecast soundings over the Piedmont and Southside for
early Friday morning show a warm nose from 700mb down, with
surface temps in the mid 30s. Any precip that tries to get into
this area will be battling dry air in the low levels, however
forecast soundings likely aren't accounting for any
evaporational cooling that could potentially take place if you
get enough rain moving into the dry layer. Quantitative precipitation forecast amounts will
likely be on the light side (a few hundredths), so rapid cooling
shouldn't be a concern, however it's close enough to at least
mention the slight possibility of some patchy freezing
rain/drizzle early Friday morning. Scattered showers will impact
the southeast portions of the forecast area throughout the day, with
moderate to heavy rain possible at times across far southeast Virginia and NE
NC. Precip will likely have a somewhat sharp cut off Friday
afternoon and evening as the low off the coast gets better
developed and the precip will be battling dry air from a strong
high pressure over the Great Lakes region. High temps will
remain cool on Friday with high temps in the upper 40s to lower

Low pressure strengthens Saturday into Sunday off the coast.
Meanwhile, the strong high pressure will move from the Great Lakes
region to over northern New England. Scattered showers will continue
mainly over the southeastern portions of the forecast area. Drier
air filtering in from the north should prevent the precip from
getting into the colder air across the western portions of the
forecast area. A tightening pressure gradient will create gusty
winds along the coast. North/northwest winds will gust 35-50 mph near the
coast. Wind advisories or warnings likely needed this weekend
along the coast. Rain should begin to wind down by late Sunday
as the low continues to move NE and pulls well away from the
coast, however some lingering scattered showers may still be
around along the coast into Sunday night. High temps Saturday
and Sunday will be in the 40s for most to low 50s across the far
se, with low temps ranging from the 30s northwest to mid 40s southeast.
Rainfall totals through Sunday night will likely be 1-2 inches
across far southeast Virginia and NE NC with lesser amounts as you move northwest.
The far northwest of the forecast area likely won't see any rain during
this event.


Long term /Monday through Thursday/...
as of 300 PM EST Thursday...

By Monday, the coastal low will be moving north-northeast offshore, up the mid-
Atlantic waters to the northeast and eventually the Canadian
Maritimes by Tuesday. Will keep a slight chance of showers in the
forecast across mainly the NE Monday with the potential for a few
residual showers around the backside of the low. After Monday, lower
confidence in the forecast as the models have an upper trough
dipping into the region Tuesday. This will bring the possibility for
the development of another coastal low off the Carolina coast late
Tuesday into Wednesday, but both the latest GFS and European model (ecmwf) runs keep
this feature well offshore. Regardless, the region (eastern portions
in particular) may feel some impacts in the form of rain showers and
wind from this system, especially if this system develops further to
the west than currently modeled. For now, have no more than chance
pops in the forecast Tuesday and Wednesday to highlight the
uncertainty. High pressure builds back across the region for the end
of next week. Below normal temperatures to start the forecast
period, but moderating temperatures closer to normal by Tuesday and


Aviation /03z Friday through Tuesday/...
as of 715 PM EST Thursday...

VFR or MVFR conditions will prevail at the taf sites this evening
into early Fri morning, with MVFR cigs and -ra expected to
affect orf/phf/ecg after midnight into early Fri morning, as
pcpn associated with coastal trough lifts NE into the southeast Virginia and
NE NC. Pcpn chances will remain highest over southeast Virginia and NE NC
during Fri, as sfc low pressure lifts NE off the southeast coast.
MVFR and possibly IFR cigs will occur at phf/orf/ecg into Fri
evening, with -ra expected. VFR or MVFR cigs will be likely at
ric/sby. Light north or NE winds early Fri morning will increase
during the day, esply at orf/ecg.

Low pressure will intensify off the southeast and mid Atlc coast Fri
evening into Sun night. Potential for rain and degraded flight
conditions expected through sun, especially at taf locations
close to the coast.


as of 420 PM EST Thursday...

Surface high pressure continues to push offshore this afternoon with
generally light (5-10 kt) onshore flow across the south
transitioning to south and southwesterly 5-10 kts across the
north. Waves in the Bay are running 1-2 ft with 2-4 ft seas
offshore (highest south). Generally quiet marine conditions are
expected to continue through the overnight hours tonight.
Northeasterly winds increase across the southern coastal waters
after daybreak as low pressure develops off the Georgia/SC coast in
response to a digging upper trough in the subtropical jet
stream. A 1035+mb surface high will quickly dive southeastward
from south central Canada on Friday into early Saturday and over
the northeast states by Saturday afternoon, setting up an
impressive and prolonged pressure gradient across the mid-
Atlantic as a series of low pressure areas deepen and
consolidate off the Carolina coast.

Marine conditions will begin to deteriorate by early Friday
afternoon as the first area of low pressure lifts slowly
northeastward. Winds will increase to 15-20 kts across the
southern coastal waters and the Currituck Sound. Conditions will
spread northward into Friday late afternoon/early evening as
low pressure consolidates off the Carolinas. An extended period
of unsettled to dangerous marine conditions appears certain from
Fri night-Sunday night with a very high likelihood of
widespread gale conditions and increasing potential for storm
conditions for areas near and south of Cape Charles including
the Currituck Sound. Even the lower James River could experience
a period of frequent gale force gusts. The most likely onset of
storm/gale conditions looks to be late Friday evening-early
Saturday morning (local wind probabilities show probs of gale
force gusts ramping up to nearly 100% during this timeframe over
the ocean/lower ches Bay with storm force wind gust probs from
Cape Charles southward climbing above 50%). Models have come
into better agreement with respect to the evolution of low
pressure and confidence continues to increase regarding the
placement and timing of gale and storm conditions. After
coordination with surrounding offices, have issued a storm watch
for ocean zones south of Cape Charles and the Currituck Sound
starting at 03z Sat. Gale watches remain in effect for the
southern ches Bay and the offshore zones north of Cape Charles
beginning at 03z Saturday as well. The gale watch for the lower
James River begins at 09z. In addition, a high wind watch has
been issued for land areas of coastal southeast Virginia (norfolk and Virginia
beach) and for inland and coastal Currituck counties through
Sunday morning.

Seas are forecast to build to 12-16 ft offshore with waves in the
ches Bay up to 4-7 ft (perhaps up to 8-9 ft at the mouth). A high
surf advisory will eventually be needed. Winds are expected to
diminish to below gale criteria late Sun night-early Mon am, before
falling below Small Craft Advisory criteria during the late Mon-Mon night timeframe.
However, seas likely remain elevated through early next week. Will
end the gale/storm watches at 12z Sunday for now but extensions
will be required in subsequent forecasts.


Tides/coastal flooding...
as of 300 PM EST Thursday...

A prolonged coastal flood event is becoming more likely this
weekend, with the worst conditions expected to occur Sunday. Strong
low pressure will develop off the southeast coast this weekend
leading to a prolonged period of strong onshore north-NE flow Saturday
through Sunday. This will allow tide departures to rise through the
weekend, leading to many areas along the Atlantic coast along/south
of Chincoteague, and lower Chesapeake Bay to see moderate coastal
flooding (with departures of 2-3 ft above normal tide) by the Sunday
morning high tide cycle. In fact, some spots (such as Jamestown and
areas along the NE NC coast) could reach major coastal flooding
Sunday. In addition, many spots may even see some minor-moderate
coastal flooding with the Saturday afternoon/evening high tide cycle
given that we will already have widespread gale force winds over the
waters by that point. With the potential for a long duration coastal
flood event, combined with the potential for significant
beach/dune erosion from the breaking waves, have opted to issue
a coastal Flood Watch for the Atlantic coast south of
Chincoteague, as well as the lower Chesapeake Bay and up the
James/York rivers. Am currently expecting inundation of 2 feet
or greater in places normally susceptible to coastal flooding,
especially on Sunday due to the higher astronomical tide.


Akq watches/warnings/advisories...
NC...coastal Flood Watch from Saturday morning through late Sunday
night for ncz102.
High wind watch from Friday evening through Sunday morning for
Virginia...coastal Flood Watch from Saturday morning through late Sunday
night for vaz084-086-089-090-093-095>100-523>525.
High wind watch from Friday evening through Sunday morning for
Marine...gale watch from Friday evening through Sunday morning for
Storm watch from Friday evening through Sunday morning for
Small Craft Advisory from 7 PM Friday to 7 am EST Sunday for
Gale watch from late Friday night through Sunday morning for


near term...cmf

National Weather Service Glossary of Abbreviations