083
FXUS61 KLWX 131850
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
250 PM EDT Sat Jul 13 2024

.SYNOPSIS...
A slow moving boundary will weaken and move further east later
today. High pressure builds over the SE CONUS Sunday though
Wednesday of next week, bringing a return of hot and humid
conditions locally. A cold front approaches Wednesday before passing
through Wednesday night into Thursday. High pressure approaches the
area late next week.

&&

.NEAR TERM /THROUGH TONIGHT/...
Today starts a warming trend. Highs today are expected to rise
into the upper 80s to low 90s for most areas east of the
Alleghenies where upper 70s to low 80s will be more common. By
tonight, lows will drop down into the 60s west of the Blue Ridge
Mountains, with 70s further east with mostly dry conditions
expected.

In terms of rain chances this afternoon, coverage looks to be isolated
to widely scattered at best. Overall consensus from CAMs is the
best shot of convection is generally along/west of the Blue
Ridge, with some guidance bringing showers towards US-15 by
sunset or so. The showers or storms do not appear to be
hazardous, but rather beneficial rain.

&&

.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
Upper ridge will settle near the region by Sunday, allowing hot
and humid conditions to build back into the area. Highs are
expected to soar into the mid to even upper 90s during the day.
With the Bermuda high in place, dewpoints will be limited into
the mid to upper 60s, allowing heat indices to only get to the
upper 90s to low 100s during the afternoon and early evening
hours. Cannot completely rule out heat advisories for some of
our eastern areas but confidence is low at this time in this
coming to fruition. Additionally with the heat and humidity
return allows for some isolated showers and thunderstorms Sunday
afternoon and evening. Lows Sunday night will fall back into
the upper 60s out west to mid to upper 70s closer to the waters
with decreasing precipitation chances.

By Monday, the Bermuda high starts to break down more, allowing for
increasing moisture and dewpoints rising into the low 70s for some
areas east of the Blue Ridge mainly. High temperatures may be a few
degrees warmer than Sunday, with some areas reaching triple
digits. Have issued an Excessive Heat Watch for all areas east
of the Blue Ridge and in the northern Shenandoah Valley into
central Maryland. Heat indices up to 105-110F are likely in the
watch area. Showers and thunderstorms will again be possible
for the afternoon and evening hours. There will be some
uncertainty leading up to these showers and storm chances with
remnant convection coming down from mainly the Ohio Valley. Will
be worth monitoring if any days at the beginning of next week
necessitate closer eyes for strong to severe storms possible.

&&

.LONG TERM /TUESDAY THROUGH SATURDAY/...
A hot and humid air mass persists over the area with the potential for
another triple digit degree day on Tuesday. Forecast 850-mb
temperatures rise into the 22-24C range which dry adiabatically
mixed to the surface carry highs to around 100 to 102 degrees.
With dew points rising into the upper 60s to low 70s, heat
indices would more than qualify for additional heat products.
Little to no relief can be had at night either with forecast low
temperatures well into the 70s, locally near 80 degrees inside
D.C. and Baltimore. Given the degree of heating and moisture in
the atmosphere, there will be an inherent risk for showers and
thunderstorms. However, the better chance for a more
concentrated risk of severe thunderstorms would come on
Wednesday with the cold front.

Ahead of this front, additional cloud cover likely overspreads the
area. This should help lower temperatures a tad, but with elevated
humidity levels as dew points are forecast to be in the low to perhaps
mid 70s. Will continue to monitor the situation for any additional heat
products that may eventually be necessary. Given the approach of a
seasonably strong cold front, expect an increasing risk for strong to
severe thunderstorms. With a slower trend in the guidance, a threat for
organized convection may loom into Wednesday night as well. As usual,
there is a lot of uncertainty in how the convective threat evolves.

This frontal system settles south and east of the region on Thursday
into Friday. Its close proximity to the local area will maintain some
threat of overrunning showers and thunderstorms. The post-frontal air
mass should certainly be cooler owing to a mainly north to
northeasterly winds. Daily highs through Friday should be in the 80s,
possibly nearing 90 degrees by next Saturday.

&&

.AVIATION /18Z SATURDAY THROUGH THURSDAY/...
Cannot rule out an isolated afternoon shower in the
vicinity of IAD or MRB later this afternoon/evening.

VFR conditions are likely Sunday into Monday with some chances for a
few showers and thunderstorms during the afternoon and evening
hours. Winds will be fairly light out of the south to southwest most
of the period.

A risk of strong to severe thunderstorms looms at all terminals through
Wednesday. This is in response to a multi-day period of excessive heat
and humidity. Restrictions are possible, especially on Wednesday as a
strong cold front tracks closer to the area. Wind fields largely remain
out of the southwest through Wednesday, accompanied by some brief
subtle wind shifts through the afternoon hours. By Thursday, a cold
front tracks through leading to a north to northwesterly wind.
Lingering shower chances loom which could lead to periods of sub-VFR
conditions.

&&

.MARINE...
Expect winds to dissipate further as the frontal boundary
continues to move further offshore through the early afternoon
hours.

Sunday, winds will turn more southwesterly earlier in the day and
the southerly by the evening hours. Shower and thunderstorm chances
increase slightly by Monday, with SCAs possible over portion of the
waters.

Southerly channeling effects may lead to some Small Craft Advisories
Tuesday evening through much of Wednesday. Additionally, the hot and
humid air mass will promote increasing chances for showers and
thunderstorms. Wednesday appears to provide the best opportunity for
severe caliber thunderstorms. This could make for some hazardous
conditions across the waterways. Special Marine Warnings may be
required for some of these storms.

&&

.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)          101F
Washington-Dulles (IAD)           98F (1995)          100F
Baltimore (BWI)                  102F (1995)          101F
Martinsburg (MRB)                107F (1936)           98F
Charlottesville (CHO)            102F (1954)           99F
Annapolis (NAK)                  101F (1995)           98F
Hagerstown (HGR)                 102F (1954)           98F

                  ***TUESDAY, JULY 16TH, 2024***
LOCATION                       RECORD (YEAR)        FORECAST
Washington-National (DCA)        104F (1988)          101F
Washington-Dulles (IAD)          104F (1988)          101F
Baltimore (BWI)                  104F (1988)          101F
Martinsburg (MRB)                107F (1988)          100F
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)+          97F
Baltimore (BWI)                  101F (1988)           97F
Martinsburg (MRB)                102F (1988)+          94F
Charlottesville (CHO)            100F (1988)+          97F
Annapolis (NAK)                  100F (1900)           94F
Hagerstown (HGR)                 100F (1953)+          95F

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...Excessive Heat Watch from Monday morning through Monday
     evening for DCZ001.
MD...Excessive Heat Watch from Monday morning through Monday
     evening for MDZ003>006-008-011-013-014-016>018-503>508.
VA...Excessive Heat Watch from Monday morning through Monday
     evening for VAZ027>031-037>040-050-051-053>057-501-502-
     505-506-526-527.
WV...Excessive Heat Watch from Monday morning through Monday
 evening for WVZ051>053.

&&

$$

SYNOPSIS...CPB
NEAR TERM...CPB
SHORT TERM...CPB
LONG TERM...BRO
AVIATION...CPB/BRO
MARINE...CPB/BRO
CLIMATE...BRO