077
FXUS61 KLWX 230132 AAA
AFDLWX

Area Forecast Discussion...UPDATED
National Weather Service Baltimore MD/Washington DC
932 PM EDT Sat Jun 22 2024

.SYNOPSIS...
Broad high pressure offshore will continue to drive excessive heat
and humidity into the region through Sunday. A stationary front over
the Great Lakes and Upper Midwest will drop south into the area late
Sunday and Monday bringing increased chances for thunderstorms. High
pressure briefly returns Tuesday before another cold front crosses
the area Wednesday and Thursday next week.

&&

.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...

Very warm and muggy tonight with lows struggling to drop below
80 along and east of I-95 due to increasing high clouds and
scattered mid clouds. Some record warm minimums are expected,
particularly at IAD and DCA. Some scattered convection has
developed in the vicinity of Winchester, but hopefully, these
storms will wane by midnight with increasing convective
inhibition. Adjusted minimums upward tonight by several degs and
tomorrows`s highs just a touch, keeping them just shy of the
century mark. Also, increased PoPs for Sunday-Sunday evening
given better signal for convection in model guidance, although
the best chance may not be until evening, but multiple rounds
are not out of the question.

&&

.SHORT TERM /6 AM SUNDAY MORNING THROUGH MONDAY NIGHT/...
One last hot day is on top for the Mid-Atlantic region on
Sunday. Despite a gradual lowering of heights as the ridge
buckles, net warming in the lower troposphere will make for
another toasty one. Forecast highs rise into the mid/upper 90s
again, accompanied by dew points which will hold steady in the
upper 60s to low 70s. Profiles appear moister on Sunday which
suggests it may be more difficult to scour out the moisture by
convective mixing processes. Consequently, Heat Advisories will
again go into effect, but this time for the Blue Ridge eastward
from 11 AM until 7 PM. Heat indices start pushing into the 104
to 107 degree range. The biggest question mark will be whether
any sizable increase in mid/high clouds can offset surface
heating effects. Additionally, the guidance does show some light
shower activity firing up near the lee trough. This could
further hinder temperatures from hitting the century mark.

Unlike today/Saturday, lift in the column should be more robust
as the area is grazed by a shortwave trough over New England.
The glancing blow of height falls combined with better moisture
transport should allow for greater shower and thunderstorm
coverage on Sunday afternoon through portions of the overnight
hours. Multiple rounds of such convection is possible, some of
which could become strong to severe in nature. The Storm
Prediction Center has upgraded areas north of U.S. 50 into a
Slight risk for severe weather on Sunday. Elsewhere, a Marginal
risk persists. There is also a non-zero risk for flash flooding
for locations that see multiple rounds of activity. The flash
drought which has ensued from the lengthy heat wave will help
mitigate some of the flood risk though.

A cold front sweeps through the area late Sunday night into
Monday morning. This slowly brings an end to the shower and
thunderstorm activity. The new work week will yield slightly
cooler temperatures and less humidity. Mid 80s to low 90s are
expected during the afternoon, while 70s are more commonplace
over mountain locales. Any shower activity largely ends up
farther south to around the I-64 corridor. Northwesterly winds
persist through the day with afternoon gusts up to 20 mph at
times. Dry weather continues into the night with forecast lows
falling back into the 60s, locally in the mid/upper 50s over the
higher terrain.

&&

.LONG TERM /TUESDAY THROUGH SATURDAY/...
A one day reprieve in the humidity before the heat surges again
midweek. More widespread thunderstorm chances and much needed rain
expected across the area Wednesday into Thursday.

Surface high pressure briefly builds back over the area Tuesday
giving us a brief reprieve in humidity as drier air settles in.
Dewpoints will fall back into the mid to upper 50s and low 60s with
light west to northwest breezes. The drier air combined with a
downslope component to the wind will allow high temperatures to
surge back into the low to mid 90s especially east of the Allegheny
Front. Overnight lows Tuesday night will fall back into the upper
60s and low 70s.

Unfortunately, high pressure quickly pushes offshore Wednesday
allowing for increased southwesterly return flow and our next
shortwave trough/front to move in. This will allow temperatures to
surge back into the mid to upper 90s with heat index values up and
over the 100 degree mark east of the Blue Ridge Wednesday afternoon.
Some uncertainty remains in regards to temperatures due to the
progression of the next shortwave trough and incumbent cold front
from the Ohio River Valley set to approach the region. 12z
synoptic/ensemble guidance suggest fairly spotty convection
Wednesday afternoon and evening with more widespread thunderstorm
activity developing across the Ohio River Valley and advancing east
toward the region Wednesday night. This is partially due in part to
the modeling trying to resolve what looks to be a complex of
thunderstorms diving south and east from the Ohio River Valley ahead
of the cold front late Tuesday night into Wednesday morning. In the
event this occurs the atmosphere may be turned over reducing the
potential threat of widespread severe weather or pushing it later
into Wednesday and perhaps Thursday. Current CSU learning machine
probabilities and the SPC discussion in the Day 5 timeframe also
illustrate this potential threat/uncertainty for severe weather
during the midweek timeframe.

Additional shower and thunderstorm chances are possible especially
east of the Blue Ridge Thursday as the front and upper level trough
slowly push south and east of the area. With that said, extra cloud
cover and a front overhead will lead to cooler temperatures in the
mid to upper 80s. Broad high high pressure will return from the
north Friday delivering mostly sunny skies, seasonable temperatures,
lower humidity, and light onshore flow. The high slides off the New
England coast Saturday allowing south to southwesterly flow to
return along with the terrain based showers and thunderstorms.
Temperatures on both days will sit in the mid to upper 80s and low
90s with upper 70s to low 80s expected in the mountains.

&&

.AVIATION /02Z SUNDAY THROUGH THURSDAY/...
VFR conditions can be expected through Sunday morning with
mainly southerly winds.

By Sunday afternoon into the evening, there is an increasing
threat for showers and thunderstorms as a cold front approaches
from the Ohio Valley. Winds shift to southwesterly on Sunday
with gusts up to 20 knots from the late morning until around
dark. The threat for storms will also lead to some restrictions
at times. Showers remain in the picture through Sunday night as
winds gradually shift to westerly.

Prevailing VFR conditions are expected Monday outside of a few
thunderstorms along and east of the corridor terminals Monday
morning into early Monday afternoon. Convection will mainly be tied
to the cold frontal boundary as it sweeps through. Any convection
that we do see will cause brief MVFR or lower restrictions. Outside
of thunderstorm chances some morning river/valley fog and ground fog
could create restrictions especially west of corridor Monday
morning in the wake of the departing frontal boundary.

High pressure returns to the area Monday evening into Tuesday
bringing continued VFR conditions. Additional showers and
thunderstorms are likely Wednesday into Thursday as another cold
front passes through the area.

&&

.MARINE...
Southerly channeling effects persist through tonight and into
Sunday morning. Expect a gradual shift to southwesterly flow
during the day on Sunday. Winds stay up through the day which
warranted additional Small Craft Advisories through early Sunday
evening. There is also an increased risk for showers and
thunderstorms, particularly from the late afternoon through the
early overnight hours. Special Marine Warnings may be required
for some of Sunday`s convective activity. The cold front
responsible for all of this action pushes across the waters
Monday morning.

Small Craft Advisories may be needed for portions of the waters
Monday into Monday night as a cold front passes through. A few
thunderstorms may develop along the front Monday morning into Monday
afternoon mainly over the middle and lower waters. Winds will switch
to the west and northwest with gusts up to 20 kts. The primary
threat with thunderstorms will be strong winds. Sub-SCA level west
to northwest winds return Tuesday as high pressure builds back over
the area. Winds turn back to the south to southwest Wednesday as
high pressure pushes offshore. Some southerly channeling could occur
over the lower waters Wednesday ahead of an approaching cold front
from the Ohio River Valley. SCA level winds look to return to
portions of the waters Wednesday night into Thursday as a cold front
passes through.

&&

.CLIMATE...
Very hot temperatures are expected through Sunday, and again on
Wednesday next week. Several records could be in jeopardy, as
seen below. Below is a list of record high temperatures for Jun
23rd, and 26th, the year the record was set, and the current
forecast high temperatures for those days. A plus sign after the
date signifies the record was set multiple times, with the most
recent year indicated below. RERs are only issued for DCA, IAD,
BWI, and MRB, but other sites are shown for reference.


                                    Sunday Jun 23nd
Climate Site                  Record High     Forecast High
Washington-National (DCA)     98F (1988)          98F
Washington-Dulles (IAD)       96F (1988)          98F
Baltimore (BWI)               97F (2010)          99F
Martinsburg (MRB)            100F (1934)          95F
Charlottesville (CHO)        100F (1894)          96F
Annapolis (NAK)               98F (1988)          96F
Hagerstown (HGR)              98F (1988)          95F

                                    Wednesday Jun 26th
Climate Site                  Record High     Forecast High
Washington-National (DCA)    101F (1952)          98F
Washington-Dulles (IAD)       95F (1998)          98F
Baltimore (BWI)               99F (1954+)         97F
Martinsburg (MRB)            102F (1943)          94F
Charlottesville (CHO)         99F (1998)          98F
Annapolis (NAK)               98F (1952)          93F
Hagerstown (HGR)          98F (1954+)         96F

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...Heat Advisory from 11 AM to 7 PM EDT Sunday for DCZ001.
MD...Heat Advisory from 11 AM to 7 PM EDT Sunday for MDZ003>006-008-
     011-013-014-016>018-503>508.
VA...Heat Advisory from 11 AM to 7 PM EDT Sunday for VAZ037>040-050-
     051-053>057-501-502-505-506-526-527.
WV...None.
MARINE...Small Craft Advisory from 6 AM to 6 PM EDT Sunday for ANZ530.
     Small Craft Advisory until 6 PM EDT Sunday for ANZ531>534-
     537>543.
     Small Craft Advisory from 11 AM to 6 PM EDT Sunday for ANZ535-
     536.

&&

$$

SYNOPSIS...EST
NEAR TERM...LFR
SHORT TERM...BRO
LONG TERM...EST
AVIATION...LFR/EST
MARINE...LFR/EST
CLIMATE...LFR