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068
FXUS61 KLWX 240117 AAA
AFDLWX

Area Forecast Discussion...UPDATED
National Weather Service Baltimore MD/Washington DC
917 PM EDT Sun Jun 23 2024

.SYNOPSIS...
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A cold front will pass east of the area Monday leading to drier
weather and lowering humidity. High pressure briefly returns
Tuesday before another surge of excessive heat and humidity
Wednesday as high pressure pushes offshore. Another cold front
will approach the area late Wednesday into Thursday bringing
additional chances for showers and thunderstorms.
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&&

.NEAR TERM /THROUGH MONDAY/...

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Not sure how much convection will occur tonight ahead of the
frontal passage especially given lack of showers on radar this
evening and steady downward trend in lightning across the
Appalachians. Have kept isold/low end sct PoPs for the overnight
period, but it appears most places will stay dry overnight
except in the mountains where chances look a little higher.
Frontal passage is expected around 12Z with sharp drying
expected through the day Monday. Temperatures will still be
around 90, but with lowering humidity through the day.
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&&

.SHORT TERM /MONDAY NIGHT THROUGH TUESDAY NIGHT/...
By Monday morning, the surface cold front will be nearly
through the area, with any lingering showers and storms quickly
exiting southern Maryland. While temperatures will still be a
little above normal in the mid 80s to near 90, dew points
falling into the 50s and a gusty northwest wind will likely feel
refreshing compared to the weekend. A few showers may linger
through midday along the Allegheny Front as the primary upper
trough axis passes. As the wind abates Monday night, lows will
range from the mid 50s in the mountains to 60s in most other
places.

The surface high will translate through on Tuesday and move to
the southeast Tuesday night. Comfortable dew points in the mid
to upper 50s remain through the day, although temperatures will
rebound a little to the upper 80s and lower 90s. A light
southerly flow and potential clouds will result in a slightly
warmer night. There is a slight chance weakened convection from
the Ohio Valley makes a run at the Appalachians toward
Wednesday morning.

&&

.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
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Excessive heat and humidity briefly return Wednesday ahead of a cold
front that will bring more widespread chances for showers and
thunderstorms across the region.

Overall the synoptic pattern becomes a bit more amplified as high
pressure shifts offshore and the next piece of upper level shortwave
energy moves south from the Great Lakes into the Mid-Atlantic
region. With high pressure pushing offshore south/southwesterly flow
will increase which means a return of the excessive heat and
humidity. Temperatures will surge back into the mid to upper 90s
with heat index values around or over the 100 degree mark east of
the Blue Ridge Wednesday afternoon. Some uncertainty remains in
regards to the temperatures due to the progression of the next
shortwave trough and incumbent cold front from the Ohio River
Valley.

12z synoptic/ensemble guidance suggests the development of
convection Wednesday afternoon across the western half of the
forecast area before advancing east Wednesday evening into Wednesday
night as the cold front sweeps in. Added heat and humidity will
allow for increased instability across the region lending a limited
potential for severe weather. Current CSU learning machine
probabilities and the SPC discussion in the Day 4 timeframe also
back up this notion although confidence is medium at this time.
Additional shower and thunderstorm chances are possible especially
east of the Blue Ridge Thursday as the front and upper level trough
slowly push through the remainder 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 dry conditions, seasonable temperatures, lower
humidity, and light onshore flow. The high slides off the New
England coast late Friday into Saturday allowing south to
southwesterly flow to return along with a warm front from the
south. Some uncertainty remains in the placement of this
boundary in relation to an area of low pressure tracking across
the northern Great Lakes region. For now, opted to hold low end
precipitation chances Saturday afternoon and evening especially
in areas west of the Blue Ridge. Additional showers and
thunderstorms are likely Sunday as the next cold front
approaches the region.
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&&

.AVIATION /01Z MONDAY THROUGH FRIDAY/...

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The wind shift to the W/NW with the cold front will occur toward
sunrise Monday morning. Gusts up to 25 kt will be possible
through the day with a developing cu field. High pressure will
result in lighter winds Monday night into Tuesday.

Prevailing VFR conditions are expected Wednesday through Friday.
Showers and thunderstorms may lead to brief restrictions on both
Wednesday and Thursday afternoons as a cold front slowly moves
through the area. The highest coverage of storms looks to be on
Wednesday with activity mainly along and east of the corridor
Thursday. Winds will be out of the southwest Wednesday with gusts up
to 20 knots. West to northwest winds return in the wake of the front
THursday into Friday.
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&&

.MARINE...

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The cold front will pass through Monday morning with a wind
shift to the northwest. The wind forecast has trended upward for
Monday, with advisories added for all waters. Gusts of 20-25 kt
are likely, with a few gusts to 30 kt not out of the question.
Winds gradually subside Monday night, but advisories will likely
continue.

High pressure builds across the area Tuesday, with light west
winds becoming southerly by Tuesday night. An SCA may be needed
for the bay Tuesday night due to southerly channeling.

Some southerly channeling could occur over the middle and 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 afternoon into early Thursday as a cold front
passes through. Winds will diminish throughout the day Thursday in
northwest flow as high pressure builds back into the region. Sub SC-
level winds are expected with high pressure Friday.
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&&

.CLIMATE...
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Very hot temperatures are expected on Wednesday. Several
records could be in jeopardy, as seen below. Below is a list of
record high temperatures for Jun 26th, the year the record was
set, and the current forecast high temperatures for that day. 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.

                                    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+)         98F
Martinsburg (MRB)            102F (1943)          92F
Charlottesville (CHO)         99F (1998)          98F
Annapolis (NAK)               98F (1952)          94F
Hagerstown (HGR)          98F (1954+)         95F
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&&

.LWX WATCHES/WARNINGS/ADVISORIES...
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DC...None.
MD...None.
VA...None.
WV...None.
MARINE...Small Craft Advisory until 6 PM EDT Monday for ANZ530>534-
     537>543.
     Small Craft Advisory until midnight EDT tonight for ANZ535-536.
     Small Craft Advisory from 6 AM to 6 PM EDT Monday for ANZ535-
     536.
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&&

$$

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