Area Forecast Discussion Issued by NWS Sterling, VA
000
FXUS61 KLWX 150122
AFDLWX
Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
922 PM EDT Thu Mar 14 2024
.SYNOPSIS...
Increasing clouds and dry conditions continue through tonight as
high pressure pushes further off the southeast U.S coast. A cold
front will cross the area Friday into Friday night bringing showers
and thunderstorms. Cool high pressure briefly returns to the area
Saturday before a secondary cold front crosses Sunday into early
next week.
&&
.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
Warm conditions continue this evening with temperatures in the mid
to upper 60s and low 70s as of 8:30pm. Downsloping continues along
and east of the Alleghenies with the bulk of any shower and
thunderstorm activity hanging to the west across the Ohio River
Valley where better low level moisture resides.
High clouds will continue to increase overnight and gradually
thicken into Friday morning as the cold front approaches. Any shower
chances overnight will be limited to areas along and west of the
Allegheny Front as the complex of showers/storms over
western/central Ohio shifts north and east toward western MD, north-
central WV, and southwest PA. Lows tonight will fall into the mid to
upper 50s.
Shower chances will continue to increase from the north and west mid
to late Friday morning with thunderstorms heading into Friday
afternoon. Latest 18z guidance from both the HRRR/NAM3KM suggest
CAPE values on the order of 300-600 j/kg across the entirety of the
forecast area late Friday morning through Friday evening. 0-6km
shear values will 30-40 kts nearly orthogonal to the associated cold
frontal boundary. With all that said, the severe weather threat is
very low, but not zero. This is especially true for areas such as
southern MD, and the northern neck of VA where an isolated strong
storm cannot be ruled out. Cloud cover combined with limited
moisture due in part to the antecedent dry airmass will help inhibit
severe weather development.
Shower and thunderstorm activity will enter western MD and eastern
WV around or slightly after daybreak Friday morning. This activity
will advance toward I-81 and the Blue Ridge/Catoctin Mountains at or
before midday. Baltimore/Washington DC metro areas and southern MD
will see showers and thunderstorms through the afternoon with
all precipitation wrapping up from west to east between 7-9pm
Friday evening. Rainfall amounts will range between 0.10 to 0.25
inch with locally heavier amounts where thunderstorms form.
Temperatures will continue to be milder than average, but
slightly cooler than today in the west thanks to better coverage
of cloud cover and precipitation for this region. Highs Friday
will push into the low to mid 70s with 60s over the mountains.
&&
.SHORT TERM /6 AM FRIDAY MORNING THROUGH SATURDAY NIGHT/...
Shower chances will continue to increase from the north and west mid
to late Friday morning with thunderstorms heading into Friday
afternoon. Latest 18z guidance from both the HRRR/NAM3KM suggest
CAPE values on the order of 300-600 j/kg across the entirety of the
forecast area late Friday morning through Friday evening. 0-6km
shear values will 30-40 kts nearly orthogonal to the associated cold
frontal boundary. With all that said, the severe weather threat is
very low, but not zero. This is especially true for areas such as
southern MD, and the northern neck of VA where an isolated strong
storm cannot be ruled out. Cloud cover combined with limited
moisture due in part to the antecedent dry airmass will help inhibit
severe weather development.
Shower and thunderstorm activity will enter western MD and eastern
WV around or slightly after daybreak Friday morning. This activity
will advance toward I-81 and the Blue Ridge/Catoctin Mountains at or
before midday. Baltimore/Washington DC metro areas and southern MD
will see showers and thunderstorms through the afternoon with
all precipitation wrapping up from west to east between 7-9pm
Friday evening. Rainfall amounts will range between 0.10 to 0.25
inch with locally heavier amounts where thunderstorms form.
Temperatures will continue to be milder than average, but
slightly cooler than today in the west thanks to better coverage
of cloud cover and precipitation for this region. Highs Friday
will push into the low to mid 70s with 60s over the mountains.
Clearing is expected late Fri night with still a
pleasant day Sat, but cooler, with highs in the mid 60s. Tranquil
conditions Sat-Sat night under sfc ridging before secondary
front crosses the mountains Sunday morning.
&&
.LONG TERM /SUNDAY THROUGH THURSDAY/...
For the end of the weekend and start of the work week, the synoptic
pattern amplifies over the east central CONUS as an upper trough
digs into the Ohio Valley and Mid-Atlantic Sunday/Monday. A pair of
reinforcing cold fronts is progged to move through our area in this
time frame, but is expected to be a dry frontal passage for most of
our area. Some upslope precipitation is possible along the
Alleghenies early Sunday morning, with the temperatures just behind
the cold front still too warm for snow. However, by Sunday night
temperatures drop below freezing in the mountains. A series of minor
disturbances will bring a few bursts of possible snow to the
Alleghenies Monday morning and Tuesday night.
Gusty winds are expected with this system, hanging around the area
through midweek, though the strongest winds are expected Sunday with
the strongest gradient, gusting 25-35 mph and up to around 40-45 mph
in the higher elevations along the Allegheny Front. After Sunday,
winds gusting around 25-30 mph are possible each afternoon through
Wednesday, diminishing overnight each night.
Temperatures drop hard by Monday, with highs 10-15 degrees lower
than Sunday and near or below normal. By midweek temperatures begin
to moderate as high pressure builds in from the southwest.
&&
.AVIATION /01Z FRIDAY THROUGH TUESDAY/...
High clouds will continue to increase this evening in association
with an approaching cold front and complex of showers/thunderstorms
over the Ohio River Valley. VFR conditions are expected to prevail
through the overnight period into early Friday morning. Any
precipitation should hold off until or beyond 12z for TAF terminals
along and east of a line from KMRB to KSHD. Showers and
thunderstorms should work into terminals west of KMRB between 10-
15z/6-11am before advancing east toward KMRB between 13-17z/9am-1pm
and the corridor terminals between 16-21z/12-5pm. With limited CAPE
went with VCTS at all terminals instead of -TSRA. The coverage of
storms will be isolated to scattered along the progression of the
front mainly within the 16-21z/12-5pm window. Rain will be light to
moderate in nature as the front passes through. All precipitation
should come to an end from west to east across the terminals by
00z/8pm. Cigs and vsbys will range between MVFR to low end VFR with
shower/thunderstorm activity late Friday morning into Friday
afternoon.
Winds will remain light out of the south at 5-10 kts tonight into
Friday. Did add a mention of LLWS given the fact that an increasing
low level jet on the order of 30-40 kts will surge ahead of the
front early Friday morning between 6-10z/2-6am. Confidence has
increased amongst hi-res guidance and current observations to the
west for the inclusion of LLWS in the current TAF package. Winds
will remain out of the south/southwest ahead of the front Friday
afternoon with gusts up to 20 kts along the immediate edge of the
boundary. North/northwest winds will take over Friday evening into
Friday night in the wake of the frontal boundary. Sustained speeds
will remain between 5 to 10 kts.
Brief high pressure settles back over the region Saturday with VFR
condition prevailing. Winds will remain out of the west switching to
the southwest at 5 to 10 kts. FR conditions are expected Sunday
through midweek with any possible precipitation limited to the
Alleghenies and as such not expected to impact the terminals. The
main concern will be gusty W/NW winds 25 to 30 kts on Sunday and 20
to 25 kts on Monday.
&&
.MARINE...
Southerly channeling will pick up late tonight with SCA
conditions likely across the southern waters of the Chesapeake
Bay and lower tidal Potomac late tonight into Friday morning. A
few thunderstorms across the southern waters 18-22z/2-6pm
Friday afternoon/early evening may produce strong gusty winds
and require SMWs.
Southwesterly winds over the waters become gusty and northwesterly
by Sunday morning as a frontal system moves through the area. Winds
may reach SCA criteria over the northern waters during the day on
Sunday. By late Sunday night/Monday morning, SCA conditions become
more likely over the southern waters before quickly encompassing all
waters. Afterwards hazardous conditions for small crafts likely
continues into Tuesday.
&&
.TIDES/COASTAL FLOODING...
Anomalies will continue to increase through the end of the week as
winds begin to increase out of the south. Some tidal sites may reach
minor flood stage Friday ahead of the next low pressure system
expected to impact the area. The wind shift behind the cold
front Friday evening will alleviate temporary tidal flooding
concerns.
&&
.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...None.
VA...None.
WV...None.
MARINE...Small Craft Advisory until 2 PM EDT Friday for ANZ533-534-537-
543.
&&
$$
SYNOPSIS...EST
NEAR TERM...EST
SHORT TERM...LFR/EST
LONG TERM...CAS
AVIATION...LFR/CAS/EST
MARINE...LFR/CAS/EST
TIDES/COASTAL FLOODING...LFR/ADM