901
FXUS61 KLWX 181415
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
1015 AM EDT Sun Aug 18 2024

.SYNOPSIS...
A slow moving cold front will bring showers and thunderstorms to the
forecast area today. Precipitation chances peak this afternoon
and into the evening as the frontal boundary moves over the
region. In the wake of the cold front, dry conditions and cooler
temperatures return next week as Canadian high pressure builds
in from the northwest.

&&

.NEAR TERM /THROUGH TONIGHT/...
1015 AM Update: Early morning low clouds and fog are beginning
to burn off for areas along and east of I-81. Think the clearing
will be soon enough to keep severe/flood threat elevated further
east. Still looks to be a multi-threat hazard day with an
approaching cold front and already warm sector across our
eastern areas allowing for amplified instability parameters.
Most likely threat will be damaging winds and isolated instances
of flooding but cannot rule out large hail or an isolated
tornado given the increasing helicity at the lower levels for a
brief period later today. Remain weather aware today,
especially along and east of the Blue Ridge Mountains.

Previous Discussion Follows:
A slow moving cold front passing over the forecast area will
bring scattered to numerous rain showers and thunderstorms to
the forecast area today. Precipitation chances peak this
afternoon and will persist into the evening as the cold front
moves through. Atmospheric conditions will be similar to
yesterday, with CAPE values of 1000-2000 J/kg, bulk shear values
20-30 knots, and lapse rates nearing 6 C/km. The area with more
favorable conditions will be similar to yesterday with those
east of the Blue Ridge in a slight risk for severe weather.

Primary hazards for today will be damaging wind gusts and
locally heavy rainfall. A Flood Watch is in effect from 2PM this
afternoon through this evening for portions of NE Maryland and
portions of the area surrounding DC. Multiple rounds of showers
and thunderstorms are possible with some storms capable of
producing rainfall rates of an inch or two per hour. Isolated
instances of urban flooding could occur along with vulnerable
positions being sensitive to flooding given recent rainfall.
Precipitation chances decrease overnight as the frontal boundary
departs the area.

Temperatures will be in the 70s to 80s for most with overnight
low temperatures in the 60s to low 70s.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
Precipitation chances linger on Monday as a surface trough lies to
our west and a surface cold front departs offshore. By Monday
morning, the aforementioned cold front will be draped over the coast
of the Carolinas while a surface trough remains west of the
Alleghenies. Precipitation chances peak Monday afternoon,
though coverage will generally decrease as the frontal boundary
moves farther away. With any convection, there is a marginal
risk of severe weather for those south of DC and east of the
Blue Ridge.

Conditions dry out areawide Monday into Tuesday as surface high
pressure builds in from the northwest. Temperatures on Monday
will be in the upper 70s to low 80s areawide with higher
elevations staying in the mid to upper 60s. Overnight lows will
dip into the 50s and 60s areawide. Temperatures will be
noticeably cooler on Tuesday with high temperatures in the 70s
for most. Overnight lows on Tuesday will dip into the 50s for
most with higher elevations dipping into the 40s.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
Canadian high pressure will gradually build into the region through
the end of the work week settling overhead by Friday morning. As a
result, dry weather and cooler than normal temperatures are
expected. Temperatures will feel more like late September than late
August, some 10 degs below normal.

&&

.AVIATION /14Z SUNDAY THROUGH THURSDAY/...
Ceilings and visiblities will continue to improve late this
morning as low clouds and fog burn off heading into the early
afternoon. This afternoon, showers and thunderstorms will lead
to sub-VFR conditions as heavy rainfall and gusty winds bring
reduced ceilings and visibilities. Highest confidence for TSRA
is at KIAD, KDCA, KBWI, and KMTN where there is a slight risk
for severe weather. Outside of convection, expected southerly
winds blowing 5-10 knots becoming light and variable overnight.

Prevailing VFR conditions are expected on Monday, though
afternoon showers and thunderstorms could lead to sub-VFR
conditions. Winds will be out of the northwest, gusting up to 15
knots. Prevailing VFR conditions continue on Tuesday.

No sig wx is expected Wed through Thu.

&&

.MARINE...
SCA conditions are likely this afternoon, particularly in the
southern portions of the waters. SMWs are possible as strong to
severe thunderstorms impact the waters. Primary hazards will be
gusty winds,heavy rainfall, and frequent lightning strikes. SCA
criteria winds return Monday night into Tuesday.

SCA conditions are expected Wed with winds diminishing below SCA Wed
evening as high pressure settles in.

&&

.TIDES/COASTAL FLOODING...
Minor coastal flooding will continue at all tidal locations through
this afternoon`s high tide cycle with water levels receding
tonight.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...Flood Watch from 2 PM this afternoon to 8 PM EDT this evening
     for DCZ001.
MD...Small Craft Advisory until 8 PM EDT this evening for MDZ008.
     Flood Watch from 2 PM this afternoon to 8 PM EDT this evening
     for MDZ005-006-008-011-013-014-503>508.
     Coastal Flood Advisory until noon EDT today for MDZ508.
VA...Flood Watch from 2 PM this afternoon to 8 PM EDT this evening
     for VAZ053-054-506.
WV...None.
MARINE...Small Craft Advisory until 8 PM EDT this evening for
     ANZ530>534-537>543.
     Flood Watch from 2 PM this afternoon to 8 PM EDT this evening
     for ANZ530.

&&

$$

SYNOPSIS...AVS/ADM
NEAR TERM...AVS/ADM
SHORT TERM...AVS
LONG TERM...LFR
AVIATION...AVS/LFR/ADM
MARINE...AVS/LFR
TIDES/COASTAL FLOODING...LFR