Office: LWX
FXUS61 KLWX 061419
AFDLWX
Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
1019 AM EDT Mon May 6 2024
.SYNOPSIS...
An active weather pattern will continue throughout this week with
daily chances for showers and thunderstorms. Storms may contain
heavy rainfall, gusty winds, and small hail. A strong cold front
looks to cross the region Thursday into Friday bringing an increased
threat for flooding and severe weather. Decreasing rain chances and
cooler conditions are expected as high pressure returns this
weekend.
&&
.NEAR TERM /THROUGH TONIGHT/...
Dense Fog Advisories have been allowed to expire as of 10am this
morning. Pockets of one to four mile visibility values will
remain in and along the I-95 corridor and down into the central
VA Piedmont through noon today. Fog and stratus have been slow
to lift given the abundant moisture in the low levels. PWATS are
running 1.3 inches on the 12z KIAD sounding and 1.1" on the
KRNK sounding signifying the very moist airmass overhead.
Fog and stratus should continue mix out through midday as light
south to southwesterly flow takes over. This will allow for an
uptick in temperatures with afternoon highs pushing back into the
mid to upper 70s and low 80s. Cloud bases will lift, but the overall
sky coverage will remain mostly cloudy to overcast given the
approaching shortwave trough from the Ohio and Tennessee River
Valley.
This disturbance will slowly drift east across the mountains this
afternoon before pushing toward the coast this evening and into
the first half of the overnight period. 12z hi-res CAM guidance
continues to highlight the 19-00z/3pm-8pm window for the best
convective development. The HRRR/NAM seem to be the most
aggressive with convective development especially in areas
along and south of I-66/US-50 as the vort axis and max PVA cross
during the peak heating period. The 12z ARW/NSSL are slightly
less, but show a similar theme of numerous showers and
thunderstorms starting west of the Blue Ridge this afternoon and
drifting east into the metros this evening.
The severe weather threat today appears to be low given the
poor low level lapse rates, deep saturation, and low shear
(0-6km shear less than 20 kts). MLCAPE values will range
between 500-1000 j/kg north of I-66 with 1000-1500 j/kg further
south where a few breaks in the clouds may occur. This is the
area where one or two strong pulse type thunderstorms look to
occur with a brief gusts of wind, small hail, and heavy rain as
the primary concerns.
The bigger concern this evening will be heavy rainfall with a weak
surface trough extending west to east across the area. This
trough combined with slow moving thunderstorms this afternoon
and evening could lead to one or two instances of localized flash
flooding. One thing working into our favor is the recent week
of dry weather and the limited amount of rainfall over the
weekend. Even with that said, PWATS of 1.25-1.7 inches this
afternoon and evening will yield efficient rain producers out of
any loosely organized convection especially where the weak
surface trough sets up.
Shower and thunderstorm activity should keep going through the first
half of the night as the shortwave trough drifts eastward across the
area. Patchy fog may again be possible during the second half of the
night. Lows overnight tonight should generally be in the low-mid
60s, with upper 50s in the mountains. Dewpoint values will remain in
the 60s leading to a muggy feel.
&&
.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
Conditions will remain unsettled heading into Tuesday and
Wednesday, with additional chances for showers and thunderstorms
each afternoon. Decaying convection from the Ohio Valley may
also potentially impact the area during the overnight hours
Tuesday night. Temperatures will reach into the upper 70s and
lower 80s on Tuesday. Even warmer temperatures are expected on
Wednesday, with highs reaching into the mid-upper 80s.
&&
.LONG TERM /THURSDAY THROUGH SUNDAY/...
A cold front will approach the region by Thursday, ushering in
an abundance of moisture to the Mid-Atlantic. Instability ahead
of the frontal passage continues to be elevated, this may lead
to some isolated instances of strong to severe thunderstorms
Thursday afternoon and evening. Along with the limited severe
threat is the isolated threat for flooding in areas that receive
higher rainfall totals Thursday coupled with previously
received rainfall over the last few days before. Uncertainty is
still present with this system, especially with respect to
timing and potential impacts. Highs on Thursday will be in the
upper 70s to low 80s for most lower elevations with upper 60s
for the mountains.
Soon after the frontal passage on Friday, lingering low-level
moisture will probably stick around. Will keep elevated PoPs Friday
before lessening for the weekend with just normal springtime
precipitation and thunderstorm chances for the afternoon hours. High
temperatures will slowly increase behind the front and into early
next week, with 60s by Saturday eventually rising to the low to mid
70s by Monday.
&&
.AVIATION /14Z MONDAY THROUGH FRIDAY/...
IFR ceilings are expected to persist through much of the morning,
with improvement back to VFR conditions during the afternoon. Fog
will also be possible at the terminals through mid-morning. Showers
and thunderstorms will overspread the area from SW to NE during the
late afternoon and evening hours. VCTS has been introduced at all
TAF sites this evening. IFR ceilings and fog both appear possible
again tonight after the thunderstorms move out. Gradual improvement
back to VFR conditions is expected again on Tuesday, but afternoon
showers and thunderstorms will be possible once again. The threat
for afternoon showers and thunderstorms is lower on Wednesday,
but still non-zero.
Light and somewhat variable winds are expected for both today and
Tuesday. Winds will turn out of the west on Wednesday, and may
gust to around 15-20 knots at times.
Sub-VFR ceilings will likely persist through much of Thursday with
increasing rain chances along with thunderstorms for the terminals.
A few storm, especially along and east of the I-95 corridor may
become strong to severe. Westerly winds on Thursday will soon be met
with northwesterly gusts Friday as a frontal passage occurs.
&&
.MARINE...
Light winds are expected over the waters both today and on
Tuesday. However, SMWs may be needed as thunderstorms approach
the waters. The most likely time for thunderstorms to impact the
waters today looks to be during the evening and overnight hours.
Winds will turn westerly on Wednesday, and may potentially near
SCA levels across northern portions of the Bay.
SCA conditions are becoming increasingly likely Thursday, with an
isolated threat for a few SMWs to be issued due to an strong
thunderstorms that cross the waters. Improvements return Friday
behind the cold front with elevated northwesterly winds in
place.
&&
.TIDES/COASTAL FLOODING...
Sensitive tidal sites like Annapolis and DC SW Waterfront will
continue to experience minor tidal flooding for the morning high
tide cycle before dissipating. Further minor flooding will be
possible for the next high tide cycle before improvements are felt
in the tidal anamolies through midweek. Additional periods of
coastal flooding are possible in Wednesday.
&&
.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...None.
VA...None.
WV...None.
MARINE...None.
&&
$$
SYNOPSIS...EST
NEAR TERM...KJP/EST
SHORT TERM...KJP
LONG TERM...ADM
AVIATION...KJP/ADM
MARINE...KJP/ADM
TIDES/COASTAL FLOODING...KJP
