Rockville, Maryland 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

319
FXUS61 KLWX 230842
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
342 AM EST Sat Nov 23 2024

.SYNOPSIS...
Upslope mountain snow showers slowly decrease this morning while
breezy conditions continue as upper level low pressure kicks toward
the Canadian Maritimes this afternoon. High pressure briefly returns
Sunday before another front pushes through Monday into Tuesday. A
more potent front and low pressure system look to arrive for the
Thanksgiving holiday period.

&&

.NEAR TERM /THROUGH TONIGHT/...
A Blizzard Warning remains in effect until 7am this morning for
western Grant and western Pendleton Counties due to persistent
visibility at or below 1/4 mile, frequent wind gusts of 35+
mph, and heavy falling and blowing snow. Webcams in this area
continue to show blowing and drifting snow as well as poor
visibilities (below 1/4 mile).

In addition to the Blizzard Warning, Winter Storm Warnings
remain in place for Garrett Co. MD and western Highland Co. VA
until 7am. Webcams in these areas reflect a continuation of
light to moderate snow despite air temperatures at or above
freezing 32 to 35 degrees as of 3am this morning).Travel remains
difficult along the higher ridges of the I-68, US-48, and
US-219 corridors where patchy snow coverage is still evident.
Conditions look to improve beyond sunset as temperatures
continue to slowly rise. Additional snow accumulations of a
dusting to 2 inches are possible with localized amounts up to 3
inches (at elevations above 3500 feet) in both warning zones
(Blizzard and Winter Storm Warnings).

Mountain upslope shower activity will begin to decrease this morning
into mid-afternoon as the shortwave trough kicks east and the upper
level low exits off the northern New England coast. A brief period
of freezing rain or drizzle is possible early to mid Saturday
morning along the higher elevations/high valleys of the Allegheny
Front as deeper moisture vacates halting any additional ice crystal
formation. A few one hundredths of ice accumulation are expected
with up to a tenth of an inch toward Backbone Mountain and Spruce
Knob.

Conditions will continue to improve this afternoon as the low
pressure pushes toward the Canadian Maritimes. Breezy conditions
will remain with height rises in the wake of the departing shortwave
trough and incoming high pressure system from the Tennessee River
Valley. The tightened gradient between the two systems will keep
sustained northwesterly winds around 20 to 30 mph with gusts up to
40 mph (mainly on the ridges).

Temperatures warm back above into the mid to upper 30s over the
mountains today with upper 40s and low to mid 50s further east
toward the metro areas. Lows tonight will fall back into the mid to
upper 30s outside the mountains.

&&

.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
High pressure briefly returns to the area Sunday before pushing
off the southeast U.S coast Monday. Dry conditions are expected
as a result along with moderating temperatures. Highs Sunday
will push into the low to mid 50s with 40s over the mountains.
Lows Sunday night will fall into 30s.

Dry conditions are expected for the first half of Monday ahead of
the next approaching low pressure system. The low and it`s
associated cold front are expected to cross the region late Monday
into early Tuesday morning. 00z/06z guidance continues to show good
agreement with increasing precipitation chances along and west of
the Alleghenies as early as Monday afternoon before spreading east
toward the metros Monday evening into Monday night as low pressure
tracks from the mid-Mississippi River Valley into the northern Great
Lakes region. A few light to moderate showers will accompany this
front bringing more beneficial rain to the region. Rainfall amounts
of a tenth to a quarter of an inch are expected areawide. Highest
totals will be along and west of Allegheny Front.

High temperatures will be well above average, reaching the low to
mid 60s (50s in the mountains). Mostly sunny skies to start will
give way to mostly cloudy skies by the late afternoon/evening ahead
of the approaching low.

&&

.LONG TERM /TUESDAY THROUGH FRIDAY/...
A low pressure system will be passing to our north on Tuesday, and
rain associated with it will be moving out of our area Tuesday
morning. Subsidence behind the upper trough and surface high
pressure will likely yield dry conditions the remainder of Tuesday
and into Wednesday.

The latter half of the week then demands attention, as guidance
consistently suggests a low developing over the central Plains and
tracking east to the Mid-Atlantic. Models diverge at this
point, with some intensifying a trough to the north and pulling
the low along the coast as a Nor`easter, while others present a
less intense trough and allow the low to continue east offshore.
In addition to track, the timing and strength of this low are
still highly uncertain this far out. These factors will be
important to monitor for the potential of mountain snow and snow
further east for Thursday into Friday.


&&

.AVIATION /09Z SATURDAY THROUGH WEDNESDAY/...
VFR conditions are expected at most terminals through Monday. Brief
periods of MVFR cigs are possible through this evening as the upper
level low slowly exits the region. Highest confidence for this will
be at terminals along and west of the Blue Ridge. Any residual light
shower or drizzle activity over the corridor will wrap up prior to
12z/7am with residual upslope rain/snow shower activity remaining
west of KCBE and KW99 through midday 17z/12pm.

Wind will remain the main impact to aviation today due to the
tight gradient overhead. Expect sustained west to northwest winds
at 10 to 20 kts with gusts of 20 to 30 kts during the late morning
and afternoon hours. LLWS will remain possible through early this
morning at KCHO/KSHD given lighter boundary layer winds. West to
northwest winds will decrease tonight into SUnday with gusts between
15 to 20 kts.

Next chance of sub-VFR conditions arrive Monday night into Tuesday
as another low pressure system crosses the region. A few showers
will accompany the low and it`s associated front leading to to some
cig/vsby restrictions at times. Winds will turn to the south Monday
at 5 to 15 kts. Winds increase late Monday night into Tuesday as the
front passes.

VFR conditions are expected Tuesday and Wednesday. Winds gradually
increase and turn WNW behind a frontal passage on Tuesday. Gusty
winds 20-30 knots are possible Tuesday afternoon. Winds diminish
somewhat Tuesday night into Wednesday, but gusts to around 20 knots
remain possible Wednesday afternoon.

&&

.MARINE...

Gale Warnings continue for the middle and open waters of the
bay/lower tidal Potomac through sunrise this morning. This is due
largely in part to the last big surge of wind behind the departing
upper level low and shortwave trough. High end SCA conditions with
gusts between 25 to 30 kts out of the west/northwest are expected
over all waters through early Sunday morning. Winds are slow to
taper Sunday with SCAs likely continue across most of the waters
with gusts up to 20 kts through the early afternoon period. Sub-SCA
level winds are expected late Sunday afternoon through Monday as
high pressure builds nearby.

Winds turn to the south on Monday as high pressure pushes offshore.
SOme southerly channeling may be noted of the middle and open waters
of the Chesapeake Bay resulting in SCAs. A cold front may bring a
line of gusty showers across the waters late Monday night into
Tuesday morning. SCAs are likely, but could see a few gusts near
gale force. We`ll continue to monitor this threat to see how it
materializes.

Winds increase out of the WNW Tuesday behind a front. SCA conditions
are likely with gusts upwards of 20 knots in the afternoon, and
could approach 30 knots over the wider waters. SCAs could continue
into Wednesday morning before gradually diminishing through the day.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...Small Craft Advisory until 7 PM EST this evening for MDZ008.
     Winter Storm Warning until 7 AM EST this morning for MDZ001.
VA...Winter Storm Warning until 7 AM EST this morning for VAZ503.
     Wind Advisory until 7 AM EST this morning for VAZ503-504-507-
     508.
WV...Wind Advisory until 7 AM EST this morning for WVZ506.
     Blizzard Warning until 7 AM EST this morning for WVZ501-505.
MARINE...Small Craft Advisory until 7 PM EST this evening for ANZ530-
     535-536-538.
     Gale Warning until 7 AM EST this morning for ANZ531>534-537-
     539>543.
     Small Craft Advisory from 7 AM this morning to 7 PM EST this
     evening for ANZ531>534-537-539>543.

&&

$$

SYNOPSIS...EST
NEAR TERM...EST
SHORT TERM...EST
LONG TERM...CAS
AVIATION...CAS/EST
MARINE...CJL/CAS/EST