Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

fxus61 kakq 231359 
afdakq

Area forecast discussion
National Weather Service Wakefield Virginia
959 am EDT Fri Aug 23 2019

Synopsis...
a cold front will slowly cross the mid-Atlantic region today
into tonight. The front is expected to stall along the Carolina
coast Saturday and Sunday as high pressure builds north of the
area. Low pressure is expected to develop along the boundary
Sunday night into Monday.

&&

Near term /through tonight/...
as of 1000 am EDT Friday...

Storm Prediction Center has our entire region in a slight risk for severe wx today.
Showers and thunderstorms will develop ahead of the front this
afternoon and evening. Hrrr wants to hold off on convection
until 20z but feel that much like yesterday convection will
likely be a couple hours ahead of that over the Piedmont, so
pops start increasing significantly from west to east beginning
at 18z. Damaging winds is the primary threat. Southeast Virginia and NE NC
is also in a slight risk for excessive rain today. At this
point there is no Flash Flood Watch but we will evaluate that this
afternoon when the latest model guidance comes out.

Previous discussion...

As of 400 am EDT Friday...

Current WV imagery places a trough from the Great Lakes to ern
Canada, with a broad ridge from the southeast conus into the
sub-tropical wrn Atlantic. At the surface, a cold front is
located in vicinity of the Ohio Valley, with high pressure
located well off the southeast coast. Partly to mostly cloudy,
warm, and humid early this morning with temperatures of 70-75f
and dewpoints in the upper 60s to low 70s.

The trough over the Great Lakes will continue to dig swd today
pushing the cold front into the mid-Atlantic by this aftn. On
average, numerical models forecast 1000-1500 j/kg of MLCAPE
across central portions of the area, with 1500-2500 j/kg across
srn/southeast portions. This combined with 25-35kt of 0-6km bulk shear
should allow tstms to organize into some discrete cells and line
segments, with the primary threat being damaging wind gusts
this aftn. After this initial severe threat, the main hazard
will be heavy rainfall. Precipitable water values are expected to reach
2.0-2.25", with a slow moving front and a deep warm cloud layer.
23/00z href has a rather strong signal for some excessive
rainfall across central/srn Virginia and NE NC late this aftn into
this evening. The threat is not widespread enough to warrant a
Flash Flood Watch, plus much of this area is ~10-25% or 25- 50%
of normal for rainfall the past 14 days.

Not as hot but still humid today with high temperatures ranging
from the upper 70s to ~80f N, to the mid/upper 80s S and se,
with dewpoints still in the 70s. The cold front gradually drops
through the area later tonight with pops diminishing from northwest to
southeast. Low temperatures range from the low/mid 60s N, to the low
70s southeast.

&&

Short term /Saturday through Sunday/...
as of 400 am EDT Friday...

The front is expected to settle near the Carolina coast by
Saturday as high pressure builds north of the region. Low-level
moisture will be slow to clear over NE NC where pops remain
40-60%. Additionally clouds will likely be slow to clear across
the north with NE flow off a relatively warm ocean. Highs Saturday
will generally be in the upper 70s to around 80f and could be a
few degrees cooler if rain lingers longer.

By Saturday night and Sunday the high will continue to build to
the north. However, models suggest an inverted through could
sharpen along the frontal boundary (nam is most aggressive). If
this were to occur there is the potential for anomalous easterly
flow with the high to the north and this could spread some bands of
heavier rain into ern NC, some of which could inch north of the
Albemarle Sound. Lows Saturday night range from the upper 50s to
low 60s N, to the low 70s southeast. Highs Sunday are forecast to be
in the upper 70s to around 80f.

&&

Long term /Sunday night through Thursday/...
as of 4 PM EDT Wednesday...

The extended period (monday) will start with below normal temps as
high pressure remains centered over the Canadian Maritimes with low
pressure off the NC Outer Banks. There is a chc of a few
showers/tstms (mainly across southern/eastern portions of the cwa)
on Mon. Highs mainly in the low 80s on Mon. Expect slowly warming
temperatures throughout next week as the aforementioned area of high
pressure retreats offshore and the low off the Outer Banks moves to
our northeast. Mainly dry on Tue (although an isolated aftn-evening
tstm cannot be ruled out over the area...mainly south/west). There
is a better chc for aftn-evening showers/tstms on Wed as strong low
pressure (sfc-aloft) tracks over Ontario and the trailing cold front
slowly approaches the region from the northwest. Have pops of 30-35% west/20%
east Wed aftn-Wed evening. The frontal boundary potentially lingers
over the area on Thu, so kept slight chc/low-end chc pops in the
grids (highest during the aftn-evening).

Highs in the mid 80s on Tue warming into the upper 80s by Wed-Thu.
Low Mon night mainly in the 60s. Slightly warmer Tue night-Thu night
with lows in the upper 60s northwest/low 70s southeast.

&&

Aviation /14z Friday through Tuesday/...
as of 200 am EDT Friday...

A cold front is pushing into the mountains as of 11z, with high
pressure centered well off the southeast coast. VFR conditions
prevail under scattered high clouds, with a 5-10kt SW wind. The cold
front will advance to the southeast today, with the leading edge
reaching ric and sby by 16-19z, phf/orf 21-00z, and ecg 00-03z.
Low pressure will track along the boundary and showers/tstms
are expected to become widespread, primarily after 19z.
MVFR/IFR vsby is expected in heavy rain, with MVFR and
potentially IFR cigs developing by this evening in NE flow
behind the front. A few strong wind gusts are also possible with
the initial tstms this aftn. Degraded flight conditions are
expected to continue later tonight with a 20-30% chc of showers
from ric-sby, and 30-60% over southeast Virginia/NE NC with some embedded
tstms over NE NC.

The cold front settles along the Carolina coast Saturday into
Sunday. Low pressure is expected to develop along the front by
Sunday night, before lifting to the NE Monday into Tuesday. A
chc of showers will continue, with the highest probability over
southeast Virginia/NE NC.

&&

Marine...
as of 330 am EDT Friday...

A cold front located just north of the local waters will slowly
drop south through today before slowing down further/nearly
stalling near the Virginia/NC this evening. The front finally settles
south of the region by Saturday. Ahead of the front, SW will
range around 10 to 15 knots. Behind the front, winds shift to
the north and eventually NE at around 10 to 15 knots. Seas today and
tonight will generally range from 2 to 3 feet, and waves in the
Bay around 1 to 2 feet.

As surface high pressure builds in from the north and low
pressure develops along the southeast coast on Saturday, NE
winds will likely increase to 15 to 20 knots with gusts to 25
knots. Small craft advisories will likely be needed late
Saturday through Tuesday as onshore flow persists. NE flow will
allow for seas to build to 5 to 6 feet (potentially 7 feet out
20 nm) and waves at the mouth of the Bay to build to as high as
4 to 5 feet. Winds and seas look to diminish by mid-week.

&&

Akq watches/warnings/advisories...
Maryland...none.
NC...none.
Virginia...none.
Marine...none.

&&

$$
Synopsis...ajz/cmf

National Weather Service Glossary of Abbreviations