812
FXUS61 KAKQ 080746
AFDAKQ

AREA FORECAST DISCUSSION
National Weather Service Wakefield VA
346 AM EDT Wed May 8 2024

.SYNOPSIS...
Summer-like conditions with daily showers and storms are
expected through Thursday, with a cold front expected to push
through the region late Thursday through Friday. An upper level
trough will keep a chance for showers late Saturday into Sunday,
with dry conditions expected Monday.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 330 AM EDT Wednesday...

Key Messages:

-Marginal SVR risk today for most of the region (slight risk SW
 zones)

- Hot today with highs in the upper 80s/lower 90s

The latest WX analysis indicates sfc low pressure over the upper
peninsula of Michigan, with high pressure well off the SE coast,
and a lee trough over the local area. Aloft, there are two
separate areas of low pressure: one across the Dakotas/nrn
rockies, and another near the sfc low over northern Michigan.
There is a weak ridge aloft locally, but that will be
flattening out later today as the upper trough over Michigan
translates E to upstate NY and New England by this evening.

It remains mild and dry early this morning with temperatures
mostly in the 60s. Partly cloudy, except for the MD eastern
shore where some low clouds and fog remain in place through the
next few hrs. There is a large scale area of showers/tstms over
thr OH Valley that m,may spread a shower to the far twds
sunrise but for the most part this will only lead to some
additional high clouds. SPC has a Marginal risk for severe for
most of the CWA today, with a Slight across the SW zones (from
about Farmville to Bertie Co. NC). Shear will be increasing
today as the H5 gradient tightens in response to the trough
moving from MI to New England. The 0-6km shear this aftn/evening
will increase to ~40 kt, and ML CAPE will be 1000-2000 J/Kg
(highest over the south). As such, any storms that do develop
will have the potential to become severe w/ wind as the primary
threat (though mid level lapse rates are modestly steeper than
yesterday so some large hail will also be possible). Probably
the main reason that most of the CWA is only in a Marginal is
due to the lack of a trigger for convection other than a weak
lee trough. PoPs this aftn will mostly hold off until late
aftn/early evening and will be highest across the south
(30-40%), and lowest over the NE (~20%). It will be hot with
highs into the upper 80s to lower 90s. The bulk of guidance
suggests that the best chc for storms will actually be this
evening as a band of slightly steeper mid level lapse rates are
progged to push through. PoPs diminish for awhile late in the
evening/early thu morning, but then most of the CAMs depict an
MCS potentially moving in from the W between 06-12Z Thu
morning. Will show PoPs ramping up to 40-50% late. Warm with
lows in the mid to upper 60s.


 &&

.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
As of 300 PM EDT Tuesday...

While the ridge flattens some into Wednesday, low-level thicknesses
will be at their greatest, favoring the hottest temps of the week.
Most guidance agrees on nearly everywhere flirting w/ 90 degrees
with some output even suggesting a few sites reaching 92-93F. Even
those on the eastern shore should reach the upper 80s. Given dew
points in the 60s (low 60s NW/mid-upper 60s SE), aftn heat indices
approach the mid and potentially upper 90s. The other story will be
continued chances for afternoon/evening thunderstorms. With a strong
upper low shifting E towards the Great Lakes and an approaching (but
flattening) mid/upper trough, stronger flow aloft is forecast to
overspread the FA. Area-averaged soundings show more than adequate
bulk shear to support svr wx (~40 kt). Additionally, the
aforementioned heat/humidity will favor moderate-strong instability
with MLCAPE 2000+ J/kg in the aftn, highest across the S/SE. The one
caveat is we again are lacking a prominent trigger for storms w/ the
WSW sfc flow and ridge aloft, so may have to again rely on residual
boundaries or upstream perturbations to spark convection. SPC has
upgraded the SW half of the area to a slight risk, which is where
the highest confidence resides regarding convective coverage and
strong instability. Would not be surprised to see this expanded to
the rest of the FA in future updates. Steep low and relatively steep
mid-level lapse rates argue for both large hail and damaging winds
as the primary threats from any storm that can develop. Convection
may linger into the evening and overnight as instability will be
slow to wane. Also, there is a better signal in the guidance that a
mesoscale convective system (or its remnants) will move through at
some point Wed night, which explains the elevated overnight and
early morning PoPs. Overnight lows will be in the mid-upper 60s.

The highest coverage of severe wx is expected Thursday as even
stronger flow aloft overspreads the region and a sfc cold front
approaches from the W. Aloft, the approaching upper trough will
induce height falls and provide more widespread forcing for ascent.
SPC has a slight risk for the entire area. Some of the CAMs continue
to suggest prior-day shower/storm activity may linger into the
morning hrs Thursday, which could mess with the aftn instability to
some extent. However, it is notoriously difficult to time these
features (even in the <24 hr timeframe) and the models tend to
perform poorly in their development and evolution. Damaging winds
and large hail continue to look like the most likely threats from
any storm. Given the frontal forcing, it seems probable that storms
would eventually grow upscale in a linear-type feature, with
widespread damaging winds becoming increasingly favored. Low-level
hodograph curvature is also somewhat enhanced near the front, though
high LCLs would argue against a robust tornado threat. With more
clouds around, high temps will be cooler and generally in the 80s
(warmest S/SE, coolest N). Also cooler Thu night with lows in the
upper 50s-low 60s.

Friday starts off mainly dry, but scattered showers are expected to
redevelop as the upper trough swings through and the associated
shortwave moves across either VA or the Carolinas. There will be
limited sfc-based instability but the cold pool aloft could set off
some tstms, mainly across the southern 1/2 of the CWA. At this time,
severe wx is not expected. Highs on Fri will be cooler, mainly in
the lower to mid 70s (upper 70s possible far S).

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
As of 300 PM EDT Tuesday...

There remains some uncertainty for both Friday night and
through the weekend. The 12z deterministic GFS continues to
phase the upper trough with srn stream energy Fri night (this is
because it is slower and more amplified with the trough). This
leads to sfc low pressure formation along the baroclinic zone
just offshore of the Carolinas. Such a scenario would push
widespread stratiform rainfall N towards the FA Fri evening and
overnight. The 12z ECMWF suppresses this feature further S as it
is depicts a more neutral trough tilt. At this time, will keep
the highest PoPs across the SE assuming the sfc low passes well
to our S. Beyond this, the weekend weather pattern will feature
yet another upper trough diving SE from the Great Lakes and
passing off the mid-Atlantic coast Sat night through Sunday. The
airmass will be cooler and fairly dry but will continue w/
20-30% PoPs (highest N) for Sat night through early Sun aftn. It
looks mainly dry from late Sunday through Tuesday with
seasonable temperatures (highs in the 70s with lows in the upper
40s to mid 50s), potentially warming further into the middle of
next week.

&&

.AVIATION /07Z WEDNESDAY THROUGH SUNDAY/...
As of 200 AM EDT Wednesday...

IFR/LIFR on the eastern shore as an area of marine fog and low
stratus has spread inland, with VFR conditions elsewhere under
BKN mid/high clouds. Winds are mostly light/variable. Flight
restrictions across the eastern shore should improve through 12Z
(lingering the longest at the Atlantic coast), otherwise partly
sunny and mainly dry with WSW winds through the rest of the
morning into the mid/late aftn period. Widely scattered mainly
late afternoon and evening showers and thunderstorms develop,
with enough of a chc between ~21Z today and 03Z/Thu to include
VCTS(lower chance at SBY so did not include it there). IFR VSBYs
will be possible in any tstms, along with strong gusty winds.

Outlook...Active pattern on Thu with at least a chc for
showers/storm all day (even in the morning). Some strong storms
will be possible. Drying out from W to E Thu evening, then VFR
Fri, but there will be a chc for showers/isolated tstms
redeveloping Fri aftn into Fri evening. Mainly dry Sat, but
another chc for showers Sat night into Sunday.

&&

.MARINE...
As of 330 AM EDT Wednesday...

Surface high pressure remains off the Southeast coast with multiple
areas of low pressure over the Plains and another low centered near
Michigan. Flow aloft is largely from the SW between a closed low
over the northern Plains and ridging over the Gulf of Mexico. Winds
are S at 5-10 kt early this morning with waves around 1 foot and
seas 2-3 ft.

Satellite and surface/buoy observations continue to show areas of
fog over the northern coastal waters where a Marine Dense Fog
Advisory continues until 7am. SW winds will generally stay in the 5-
10 kt range today ahead of weak lee troughing over inland areas.
Guidance is mixed with respect to the potential and coverage of
showers and thunderstorms across the waters this afternoon/evening.
However, the environment will support strong storms if they are able
to form and locally enhanced winds/waves/seas are likely in and near
any convection that is able to materialize. Sub-SCA flow continues
Thursday and with somewhat greater potential for strong storms
(highly dependent on how convection evolves upstream). Flow becomes
westerly on Friday as the surface front crosses the region. 00z
guidance has come into better agreement showing a period of cold
advection/stronger NW winds Friday night into early Saturday. This
period may require SCA headlines in subsequent forecasts. The NNW
surge looks to be short-lived with SE flow reestablishing for the
second half of Saturday. Another front potentially moves through the
region on Sunday with winds becoming NW behind the boundary, though
currently forecast to stay below SCA thresholds. Waves will
generally maintain 1-2 ft through the period but could increase to 2-
3 ft Friday night/early Saturday. Near-shore seas will average 2-3
ft with 3-4 ft more prevalent out near 20 NM.

&&

.TIDES/COASTAL FLOODING...
As of 250 PM EDT Tuesday...

The upcoming new moon cycle and the Perigee from this past weekend
will lead to continued positive tidal anomalies over the next few
days. Given the ongoing light southerly flow, some nuisance to low-
end minor coastal flood impacts are possible for coastal communities
along the upper portions of the Chesapeake Bay and tidal Potomac
River during the upcoming astronomically higher high tide cycle late
this evening into Wednesday morning. Added some Coastal Flood
Advisories for Lancaster and Northumberland Counties (Lewisetta) and
from Accomack VA north to Somerset, Dorchester, and Wicomico (MD)
counties on the bay side of the eastern shore. Potential for some
additional nuisance to near minor water levels over the next
couple of days before tidal anomalies ease later this week.

&&

.AKQ WATCHES/WARNINGS/ADVISORIES...
MD...Coastal Flood Advisory until 6 AM EDT early this morning for
     MDZ021>023.
NC...None.
VA...Coastal Flood Advisory until 6 AM EDT early this morning for
     VAZ077-078-099.
MARINE...Dense Fog Advisory until 7 AM EDT this morning for ANZ650-652.

&&

$$

SYNOPSIS...LKB
NEAR TERM...LKB
SHORT TERM...LKB/SW
LONG TERM...LKB/SW
AVIATION...AJB/LKB
MARINE...RHR
TIDES/COASTAL FLOODING...