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152
FXUS61 KLWX 141404
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
1004 AM EDT Tue May 14 2024

.SYNOPSIS...
Slow moving low pressure will gradually push across the Mid-Atlantic
region today through Wednesday bringing increased chances for
showers and thunderstorms as well as below normal temperatures.
Drier conditions return briefly Thursday before another storm system
brings the threat for showers and storms Friday into the weekend.
Weak high pressure tries to build back over the area Monday with
additional shower and thunderstorm chances heading into the middle
of next week.

&&

.NEAR TERM /THROUGH TONIGHT/...
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10 AM Update: Showers have continued to move through the area
this morning. A lull in coverage and intensity will progress
through the remainder of the morning and early afternoon.
Additional moderate to heavy precipitation is expected later
today with the heavier bands moving north from the Carolinas.
Cannot rule out an isolated rumble of thunder for the afternoon
hours.

Previous Discussion Follows:
Low pressure is swirling over Missouri this morning while a
lead shortwave and isentropic ascent are bringing thickening
cloud cover along with some light showers moving into central
Virginia and the central Shenandoah Valley. While these showers
will continue to advance northward through the morning, they may
tend to fall apart, or at least produce little measurable rain,
as the airmass to the north will still need to saturate. The
Baltimore metro area may stay dry until this afternoon. Overall,
the showers will be off and on for most of the day. Rain may
tend to fill in late this afternoon into tonight as secondary
low pressure develops along the Carolina coast and moisture is
advected northward toward the area. Instability through tonight
will be very weak, with an isolated thunderstorm threat mainly
limited to the mountains and our southern tier from central
Virginia to southern Maryland. Forecast rain totals have trended
down a bit. The greater chance for higher totals remains across
Central Virginia and perhaps to southern Maryland, due to a
combination of upslope flow into the Blue Ridge and closer
proximity to forcing from the coastal low. The flood threat in
this area remains marginal/isolated at best.

The highest temperatures today (mid 70s) may be across the
Baltimore area where clouds will stay thinner longer. The areas
already seeing showers will likely stay in the 60s. Lows tonight
drop into the upper 50s and lower 60s. Saturated low levels may
allow some patchy fog to develop, especially where there are
breaks in the rain.
-- End Changed Discussion --

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
The coastal low will be moving northeast Wednesday while the
upper level low slowly approaches from the west. The forecast
has trended cooler and more stable thanks to the onshore flow.
This means rain may take the form of occasional light showers
interspersed with drizzle, which has lowered rain amounts a bit.
Two day totals are now in the 0.25-0.75 inch range for much of
the area, with 0.75-1.5 inches across the south. A chance of
thunderstorms remains in the forecast for now, but it`s quite
possible any instability remains south and west of the area.
Temperatures likely remain in the 60s for most of the area. Rain
should gradually wind down Wednesday night as the upper level
trough axis passes, although low clouds likely stick around.

Thursday and Thursday night should feature a relative break in
the action as a narrow upper ridge moves overhead and surface
high pressure wedges in from the north. However, the now-stacked
low off the coast won`t be too far away, and it`s possible
clouds and a few showers continue to rotate westward into the
area. A few showers could also form along the Alleghenies due to
upslope flow. High temperatures will likely rebound into the
70s, but this will be contingent on cloud cover.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
Weak high pressure Thursday gives way to another shortwave trough of
low pressure Friday into the weekend. The overall weather patterns
remains about the same with one day of dry conditions (i.e Monday
and potentially Thursday this week) followed by 2 to 3 days of
unsettled weather conditions.

Mid level ridging will slide east while the next upper level trough
and low pressure system set to approach from the Ohio River
Valley/Great Lakes region Friday into Saturday. With that said,
model guidance continues to show subtle discrepancies in regards to
to the timing of this system and placement of it`s associated
surface fronts across the region. Most of the recent 00z guidance
suggests an uptick in shower and thunderstorm activity Friday
afternoon and night as a warm front lifts through the area. A slow
moving cold front and it`s associated surface low will immediately
follow Saturday into Saturday night bringing with it additional
showers and thunderstorms. Severe weather does not appear to be a
concern at this point although one or two strong thunderstorms
cannot be ruled out if CAPE/shear can be maximized within the peak
heating period. Localized flooding could be the bigger concern given
repetitive rounds of rain throughout the week and rich moisture
flooding in along the slow moving warm front Friday into Friday
night. PWATs are forecast to remain high the next 5-7 days,
exceeding the 90th percentile, so rain efficiency will be high
wherever/whenever it rains. No washouts are expected Friday or
Saturday although rain gear will come in handy especially during the
afternoon and evening hours.

Upper level ridging tries to build back into the area Sunday into
Monday bringing slightly drier conditions. Another front will follow
with renewed chances for showers and thunderstorms Tuesday and
Wednesday next week. Temperatures will continue to warm back above
average during this time leading to the potential for greater
instability for thunderstorm activity to feed off of. With a fairly
active northern stream will continue to monitor for any severe
weather or hydro threats within the extended period. Right now,
there is no mention in the Day 4-8 outlook from the Storm Prediction
Center.

&&

.AVIATION /14Z TUESDAY THROUGH SATURDAY/...
The first showers associated with the next low pressure system
are advancing northward early this morning. These will likely be
light in nature and may tend to dissipate as they approach the
metro areas. A greater chance of showers will come this
afternoon. Timing may need to be adjusted a bit. Also slowed
down the progression of low ceilings, with MVFR conditions
currently confined to western North Carolina. The light and
occasional nature of the showers this morning likely won`t
contribute to a rapid decline in ceilings. However, MVFR is
possible by this afternoon, with IFR becoming more likely
tonight (timing faster for CHO). LIFR is also possible, with
the greatest chance at CHO. A more widespread wave of rain may
arrive during the late afternoon into tonight, having a better
chance to reduce visibility. An isolated thunderstorm is
possible at CHO and MRB this afternoon into tonight, but not a
high enough chance to include in the TAF. South to southeast
winds 5-10 kt expected through tonight.

Winds become east to north Wednesday and Wednesday night, which
will likely lock in low ceilings. IFR may lift to MVFR during
the day, only to lower again Wednesday night. Occasional showers
and drizzle will continue before tapering off Wednesday night. A
few thunderstorms are possible, but this chance seems to be
decreasing.

There may be a break in activity on Thursday, but a few showers
and low clouds may stick around with low pressure remaining
stationary off the coast.

Sub-VFR conditions return Friday into Saturday as another upper
level trough and series of fronts traverse the region. Shower and
thunderstorm activity will increase across the terminals especially
Friday and Saturday afternoons. Slightly drier conditions and VFR
return Sunday into Monday with weak mid level ridging overhead.
Additional sub-VFR conditions are possible Tuesday into Wednesday
next week as another front and shortwave low pressure system cross
the region.

&&

.MARINE...
-- Changed Discussion --
An occasional 20 knot gust could occur today, but overall winds
should be sub-advisory. South-southeast winds increase once
again late this afternoon and evening, with another SCA being
issued for the Chesapeake and lower Potomac. Winds could gust
slightly higher to around 24-28 knots in the open waters of the
bay during this time. Isolated thunderstorms are possible later
this afternoon into tonight.

SCA conditions likely continue Wednesday through Thursday, at
least along the bay, as low pressure becomes nearly stationary
off the coast. Showers and an isolated thunderstorm will
continue Wednesday before decreasing Wednesday night.

Marginal SCA conditions remain possible especially over the open
waters of the bay and lower tidal Potomac Friday and Saturday. This
is due largely in part to an area of low pressure and series of
fronts crossing the region. Shower and thunderstorm will increase
especially during the afternoon and evening hours. Special Marine
Warnings may be needed for portions of the waters if any strong
storm capable of producing wind gusts of 35 knots develops

SCA conditions continue for portions of the waters Sunday and Monday
due in part to the tightened gradient across the region. These
conditions may expand into Tuesday and Wednesday as another
shortwave low pressure system crosses the region.
-- End Changed Discussion --

&&

.TIDES/COASTAL FLOODING...
South to southeast winds through tonight will keep water levels
elevated in the Chesapeake Bay and Tidal Potomac. Expect additional
minor coastal flooding at high tide over the next 24-36 hours,
especially at sensitive locations in Annapolis, Otter Point, DC
Waterfront, and Straits Point.

As an area of low pressure moves east of the area Wednesday, winds
become northeast, then north. This should result in quickly
decreasing water levels and reduced coastal flood threat.

Beyond Wednesday, the next threat for coastal flooding appears to be
Thursday and Friday as snap back occurs.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
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DC...None.
MD...Coastal Flood Advisory until 2 PM EDT this afternoon for
     MDZ014.
VA...None.
WV...None.
MARINE...Small Craft Advisory from 4 PM this afternoon to 2 AM EDT
     Wednesday for ANZ530>532-539-540.
     Small Craft Advisory from 4 PM this afternoon to 6 AM EDT
     Wednesday for ANZ533-534-537-541-543.
-- End Changed Discussion --

&&

$$

SYNOPSIS...EST
NEAR TERM...ADS/ADM
SHORT TERM...ADS/ADM
LONG TERM...EST
AVIATION...ADS/ADM/EST
MARINE...ADS/EST
TIDES/COASTAL FLOODING...LWX