936
FXUS61 KLWX 151840
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
240 PM EDT Mon Jul 15 2024

.SYNOPSIS...
Hot and humid conditions will persist through midweek as a
surface trough lingers east of I-95 with high pressure remains
offshore. The surface trough will be overtaken by a cold front
late Wednesday into Thursday. This front will then stall to the
south through the end of the week and into the weekend.

&&

.NEAR TERM /THROUGH TONIGHT/...
Another oppressively hot afternoon. Heat headlines remain in
effect through the evening. Stay hydrated and well-rested.

In terms of convection this afternoon, model guidance continues
to show an axis of showers and thunderstorms across the CWA
from approximately the Shenandoah Valley towards the northern DC
metro and points northwest later this afternoon into this
evening. There is a remnant MCV well north of the area near Lake
Erie, but there is an area of forcing attached south of the MCV
from a line along I-79 in western PA down to Morgantown, WV.
This is visible on satellite imagery as of 18Z. As this moves
east and interacts with a lee sfc trough and potential bay
breeze, the potential for convection increases. Now there is a
subtle inversion present on ACARS data as of 18Z around 500 mb
with weak westerly flow that is inhibiting a lot of the cu for
the time being. Some of these storms may become strong to
severe given the available convective parameters. Most likely
hazards will be damaging winds. Most convection should depart to
the east a little after sunset, with some residual showers
sticking around into the overnight hours. Overnight lows will
drop down into the upper 60s to low 70s for most with mid to
upper 70s closer to the waters.

&&

.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
Have upgraded the Excessive Heat Watch for Tuesday into an
Excessive Heat Warning for the DC and Baltimore metros along
with the northern portions of the Shenandoah Valley into the
eastern panhandle of West Virginia. Elsewhere, heat advisories
are in effect for tomorrow afternoon and evening. Most models
have Tds a degree or two higher tomorrow, so heat indices right
around local criteria are expected. This coupled with another
day of heat and oppressive humidity will likely result in
continued heat related illnesses.

Additionally, showers and thunderstorms return thanks in part to
remnant MCS activity and a local surface trough. Still more
uncertainty as to where coverage may be greatest but have tried to
highlight the northern two-thirds of the CWA as the best chance for
convective initiation. Better forcing exists further north of the
area but should this change, strong to severe thunderstorms may
become more common across our northern half of the forecast
area. This is where SPC has upgraded the northern third of the
area to a Level 2 out of 5 (Slight Risk). Precipitation wanes
by the mid to late evening hours with lows dropping down into
the 70s for most areas aside from upper 60s in the mountains.

Another hot day is expected on Wednesday, although heat index values
may be a few degrees cooler compared to previous days. Heat
Advisories are still possible, especially east of the Blue Ridge
Mountains and the climo areas along the waterways. A cold front
will approach the area from the Ohio Valley, leading to an
increase in shower and thunderstorm potential across the area.
There are some timing discrepancies with the front that may
inhibit strong to severe storms with post-peak heating
initiation. The front is expected to slowly move south where it
will eventually stall past Wednesday night. Lows are expected to
be in the 60s to low 70s for most areas with increasing
northwest flow.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
The primary features of interest will be a pair of stagnant upper
ridges across the Intermountain West and western Atlantic, as well
as a prominent trough over eastern Canada down into much of the
eastern third of the country. With the area of lower heights
anchoring a good chunk of the northeastern U.S., there will finally
be a period of near to even below average temperatures.

Looking down to the surface, a cold front responsible for the
pattern shift will drop south and east of the local area on Thursday
before settling into the Carolinas by Friday. Some increase in
heights are expected by the weekend as the Atlantic ridge shifts
westward. This leads to a weakening of the southern extension of
troughing across the northeastern U.S. Overall, this front will
provide a focus for additional showers and thunderstorms as it
pushes southward on Thursday. This would particularly focus over
areas south of I-66/U.S. 50 before a mainly dry sets up on Friday.
Forecast highs each will top out in the mid/upper 80s, locally in
the 70s across mountain locales. More sunshine can be had with the
frontal zone well off to the south.

Over the weekend, the period of north to northeasterly winds ends
with the stalled front returning northward a warm front. Conditions
turn warmer along with an uptick in humidity levels. Based on
multiple ensemble systems, such temperatures should stay fairly
close to average for mid/late July standards. This places highs
squarely in the upper 80s to low 90s. Shower and thunderstorm
chances return with the return of the front. This pattern is
expected to hold on into early next week as well.

&&

.AVIATION /18Z MONDAY THROUGH SATURDAY/...
Have added VCTS and VCSH to all TAFs aside from CHO this
afternoon and evening. CU field is starting to grow and model
guidance continues to have various showers/thunderstorms across
the area. Main concern form an aviation standpoint would be
microbursts. Otherwise, VFR conditions are expected to persist
through much of the period. Another period of VCTS is possible
Tuesday afternoon. Some guidance has a more organized complex
along/north of the Potomac river. Low confidence, but something
to monitor.

A few westerly or southwesterly wind gusts to 15 kts are
possible this afternoon Otherwise, winds will continue to be
fairly light out of the south to southwest leading into Tuesday
before becoming more westerly to northwesterly on Wednesday as a
cold front approaches the area sometime later in the day on
Wednesday.

A shift to north to northwesterly winds will take place Thursday
morning with the threat for showers and thunderstorms tracking
southward with the front. Some restrictions are possible,
particularly across the more southern terminals. Improvements can be
expected once this system exits toward the Virginia/North Carolina
border. A mainly dry day is likely for Friday with VFR conditions.
Winds eventually shift to northeast to easterly on Friday with the
frontal zone returning as a warm front by Saturday. This introduces
additional shower and thunderstorm chances on Saturday which could
bring periods of sub-VFR conditions.

&&

.MARINE...
SMWs are possible today and Tuesday with any strong
thunderstorms that cross the waters. SCAs will be possible
Wednesday after a cold front crosses the waters later in the day
and into the overnight hours.

A cold front will track across the waters Thursday morning which
brings a shift to northerly winds. These persist through much of the
day before turning more northeast to easterly on Friday. At this
point, background winds stay below Small Craft Advisory levels.
However, there could be some showers and thunderstorms across the
southern waters for the first half of Thursday. These could pose a
hazard to mariners in the waterways.

&&

.TIDES/COASTAL FLOODING...
Anomalies will be slightly elevated over the next several days
with some more sensitive tidal locations reaching action stage.
No minor flooding is expected over the next several tide cycles
locally.

&&

.CLIMATE...
Here are some daily high temperature records during the July 15-17
timeframe next week.

Records (RERs) are only issued for DCA, IAD, BWI, and MRB, but
other sites are shown for reference. A `+` sign indicates multiple years
currently hold that record.


                ***MONDAY, JULY 15TH, 2024***
LOCATION                       RECORD (YEAR)        FORECAST
Washington-National (DCA)        100F (1988)          100F
Washington-Dulles (IAD)           98F (1995)          101F
Baltimore (BWI)                  102F (1995)          101F
Martinsburg (MRB)                107F (1936)           99F
Charlottesville (CHO)            102F (1954)          100F
Annapolis (NAK)                  101F (1995)           99F
Hagerstown (HGR)                 102F (1954)           98F

                  ***TUESDAY, JULY 16TH, 2024***
LOCATION                       RECORD (YEAR)        FORECAST
Washington-National (DCA)        104F (1988)          102F
Washington-Dulles (IAD)          104F (1988)          102F
Baltimore (BWI)                  104F (1988)          102F
Martinsburg (MRB)                107F (1988)           99F
Charlottesville (CHO)            102F (1988)          100F
Annapolis (NAK)                   98F (1997)+          98F
Hagerstown (HGR)                 104F (1988)          100F

                 ***WEDNESDAY, JULY 17TH, 2024***
LOCATION                       RECORD (YEAR)        FORECAST
Washington-National (DCA)        102F (1980)           97F
Washington-Dulles (IAD)          100F (1997)+          96F
Baltimore (BWI)                  101F (1988)           97F
Martinsburg (MRB)                102F (1988)+          93F
Charlottesville (CHO)            100F (1988)+          96F
Annapolis (NAK)                  100F (1900)           94F
Hagerstown (HGR)                 100F (1953)+          93F

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...Excessive Heat Warning until 8 PM EDT this evening for DCZ001.
     Excessive Heat Warning from 11 AM to 8 PM EDT Tuesday for
     DCZ001.
MD...Excessive Heat Warning until 8 PM EDT this evening for MDZ003-
     006-008-011-013-014-016>018-504-506>508.
     Excessive Heat Warning from 11 AM to 8 PM EDT Tuesday for
     MDZ003-006-008-011-013-014-016>018-504-506>508.
     Heat Advisory until 8 PM EDT this evening for MDZ004-005-502-
     503-505.
     Heat Advisory from 11 AM to 8 PM EDT Tuesday for MDZ004-005-
     502-503-505.
VA...Excessive Heat Warning until 8 PM EDT this evening for
     VAZ027>031-053>055-057-527.
     Excessive Heat Warning from 11 AM to 8 PM EDT Tuesday for
     VAZ027>031-053>055-057-527.
     Heat Advisory until 8 PM EDT this evening for VAZ025-026-
     036>040-050-051-056-501-502-504>506-526.
     Heat Advisory from 11 AM to 8 PM EDT Tuesday for VAZ025-026-
     036>040-050-051-056-501-502-504>506-526.
WV...Excessive Heat Warning until 8 PM EDT this evening for
     WVZ051>053.
     Excessive Heat Warning from 11 AM to 8 PM EDT Tuesday for
     WVZ051>053.
     Heat Advisory until 8 PM EDT this evening for WVZ050-055-502-
     504-506.
     Heat Advisory from 11 AM to 8 PM EDT Tuesday for WVZ050-055-
     502-504-506.

&&

$$

SYNOPSIS...CPB
NEAR TERM...CPB
SHORT TERM...CPB
LONG TERM...BRO
AVIATION...BRO/CPB
MARINE...BRO/CPB
TIDES/COASTAL FLOODING...LWX
CLIMATE...LWX