842
FXUS61 KLWX 060754
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
354 AM EDT Sat Jul 6 2024

.SYNOPSIS...
A cold front moves through the area through tonight. The front
brings shower and thunderstorm chances east of the Blue Ridge today.
Humidity decreases Sunday in the wake of the front with high
pressure briefly building overhead. Heat, humidity, and daily
thunderstorm chances return early next week.

&&

.NEAR TERM /THROUGH TONIGHT/...
Oppressive warmth this morning continues in the DC and Baltimore
metros where temperatures reside in the mid 80s and heat indices
are around 90-95. It is very rare to see these kind of temperatures
persist so late into the night, even for mid July. Elsewhere,
temperatures have fallen to the mid to upper 70s. By sunrise, expect
most areas to be in the 70s, except for the immediate DC and
Baltimore City areas that will be around 80F. A shower or two could
develop this morning in the very moist airmass east of the Blue
Ridge, though most areas are likely to remain dry.

A weak front to our north this morning will slowly slide south
across the area today into tonight. The latest guidance and CAM
output indicate conditions are going to remain mostly dry west of
the Blue Ridge. In these areas, temperatures this afternoon reach
the low 90s, but deeper mixing drops dew points to the 60s and
eliminates any heat advisory concerns there.

The same cannot be said for those east of the Blue Ridge where hot
and very humid conditions persist. Particularly, those along and
east of I-95 will see temperatures hit the upper 90s this afternoon
and heat indices of 105-108. A Heat Advisory is in effect today for
these areas. The development of the bay breeze in the mid to late
afternoon will bring in mid to upper 70s dew points along the
Western Shore during peak heating. The result in heat indices between
110-113 for several hours through early evening from Baltimore to
St. Mary`s County. As a result, an Excessive Heat Warning has been
issued for these areas of the Western Shore.

Between I-95 and the Blue Ridge there is uncertainty regarding how
much/where deep mixing occurs, and how low dew points drop this
afternoon. Given that yesterday dew points dropped to around 70F
along US-15, and better mixing is expected today, opted to not issue
a Heat Advisory in the western Piedmont/foothills where heat indices
max out between 100-102. The Heat Advisory was expanded to cover
Orange, Culpeper, southern Fauquier, eastern Loudoun, the rest of
Montgomery/Howard, and all of northeast MD.

As the front reaches I-95, isolated to scattered thunderstorms are
likely to develop ahead of it, but most of the convection pushes
east of I-95 quickly. The highest storm coverage is expected over
Southern MD and the Eastern Shore. A strong storm or two is
possible, with damaging winds as the main threat. However, the
overall severe threat is very low. Locally heavy rainfall could lead
to an instance or two of flooding, though chances for this too are
low. Lingering convection dissipates by late evening.

As the front passes through Southern MD it begins to slow down,
which could keep some shower/storm activity over the lower
Chesapeake Bay through the night. Overnight lows drop to the 70s
east of the Blue Ridge, and 60s to the west.

&&

.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
The frontal boundary stalls just south of our area, over SE/south-
central VAl Sunday. This brings dry conditions to most of the area,
though cannot rule out a brief storm or two in Central VA or far
southern MD. While still hot, highs in the low to mid 90s, the
humidity levels are going to be noticeably lower Sunday. Mild
conditions Sunday night as lows only drop to the low to mid 70s.

A warm front lifts north through the area early Monday. Southerly
flow returns and advects deep moisture over the area once again.
Scattered afternoon to evening showers and thunderstorms return to
the forecast Monday. High heat and humidity return as highs reach
the low to mid 90s, and peak heat indices soar upwards of 100.

&&

.LONG TERM /TUESDAY THROUGH FRIDAY/...
A Bermuda high will remain in place offshore through next week,
maintaining prevailing southerly flow locally. At mid-upper levels,
broad troughing will reside across the center of the country, with
southwesterly flow aloft locally. Multiple disturbances will pass
off to our northwest over the course of the week, helping to
increase chances for afternoon and evening showers and
thunderstorms. The best chances for showers and thunderstorms may
come Tuesday into Wednesday as a cold front drops southward toward
the area. All in all, the pattern looks like a pretty typical mid-
summer pattern through much of the week, with hot and humid
conditions and daily chances for afternoon/evening thunderstorms.

Each day looks to be humid, with dewpoints in the lower to middle
70s. Tuesday should be the hottest day of the long term period, with
highs generally in the lower to middle 90s. Temperatures should cool
slightly heading toward the end of the week as a weak cold front
moves through (highs in the mid to upper 80s). Overnight
temperatures will remain very warm, with lows generally in the lower
to middle 70s for most.

&&

.AVIATION /08Z SATURDAY THROUGH WEDNESDAY/...
General VFR conditions are expected this weekend. A weak front
slowly crosses the area today, then moves south on Sunday. Most
terminals remain dry as afternoon showers/storms today focus east of
DCA/BWI/MTN. Cannot rule out some VCTS for an hour or two this
afternoon, but confidence and probabilities are too low to include
in the TAFs at this time.

Southwest to west winds today become north tonight, then light and
variable Sunday as high pressure quickly passes over the area. A
warm front lifts north of the area Monday, bringing southerly winds
and a return of afternoon showers and thunderstorms.

Prevailing VFR conditions are expected on both Tuesday and
Wednesday, but temporary drops to sub-VFR may be possible either
afternoon or evening. Winds will be out of the south on both Tuesday
and Wednesday.

&&

.MARINE...
South winds early this morning gusting around 20 knots in the open
waters of the Chesapeake Bay south of Drum Point will abate by mid
morning. Winds turn southwest, then west through the day as a weak
front slowly moves south across the local waters. Scattered showers
and thunderstorms are possible this afternoon, mostly south of North
Beach and over the Lower Tidal Potomac. Any strong storm could
produce wind gusts in excess of 35 knots, in addition to lightning
strikes.

The front slowly pushes south of Southern MD late tonight, though it
is forecast to stall just south of the area Sunday. While a
thunderstorm or two is possible Sunday in the lower Chesapeake
waters, mostly dry conditions are forecast. Winds turn north
tonight, then are variable Sunday.

A warm front lifts north across the waters early Monday, bringing
the return of south winds at 10-15 knots. Scattered afternoon
showers and thunderstorms return to the forecast Monday.

Persistent southerly flow is expected over the waters on Tuesday and
Wednesday. Winds may near SCA levels in channeled southerly flow
Tuesday afternoon into Tuesday evening.


&&

.TIDES/COASTAL FLOODING...
Generally light southerly to southwesterly flow will result in
elevated tide levels through the weekend. Vulnerable shoreline may
come close to minor flooding during the early morning high tides.

&&

.CLIMATE...


&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...Heat Advisory from 11 AM this morning to 8 PM EDT this evening
     for DCZ001.
MD...Heat Advisory from 11 AM this morning to 8 PM EDT this evening
     for MDZ005-006-008-013-016-503>508.
     Excessive Heat Warning from 11 AM this morning to 8 PM EDT
     this evening for MDZ011-014-017-018.
VA...Heat Advisory from 11 AM this morning to 8 PM EDT this evening
     for VAZ050-051-053>057-502-506-526-527.
WV...None.
MARINE...Heat Advisory from 11 AM this morning to 8 PM EDT this evening
     for ANZ530.
     Small Craft Advisory until 6 AM EDT early this morning for
     ANZ534-543.

&&

$$

SYNOPSIS...KRR
NEAR TERM...KRR
SHORT TERM...KRR
LONG TERM...KJP
AVIATION...KRR/KJP
MARINE...KRR/KJP
TIDES/COASTAL FLOODING...LWX