Area Forecast Discussion
Issued by NWS Sterling, VA

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FXUS61 KLWX 250843
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
343 AM EST Sun Feb 25 2018

.SYNOPSIS...
A stationary boundary draped across southern Virginia will lift
northward today as a warm front. A cold front will approach from the
west and cross the area by this evening. High pressure will then
build in over the region, migrating off the Mid Atlantic coast by
midweek. A broad area of low pressure will approach the Great Lakes
region on Thursday, bringing unsettled weather to our region through
weeks end.

&&

.NEAR TERM /THROUGH TONIGHT/...
The wave of moderate to heavy rain that traversed the area earlier
this morning is clearing northeast MD, with additional light to
moderate shower activity moving into western MD and the eastern WV
Panhandle. High res model guidance brings this area of rain eastward
through daybreak, nearing the metro areas, but keeping the bulk of
rain along and north of the District. Visibilities have dropped this
morning in the wake of the earlier rainfall, ranging 1 to 3 miles in
the most restricted areas, but it`s not the widespread dense fog we
experienced 18-24 hours ago. Temperatures are holding generally in
the middle to upper 40s area wide, and they could fall a few more
degrees before bottoming out for the night.

A west to east oriented station boundary across southern Virginia
this morning will lift northward as a warm front today, and how far
northward it progresses will have implications on how warm
temperatures reach across the area. Some model guidance wants to
bring 70s as far north as D.C., but think that may be a bit over
done. Do think the 70s are obtainable along the southern tier of our
CWA where the warm front will be to the north, while the lower 60s
are more likely across the northern tier, and middle to upper 60s in
between.

After somewhat of a lull in rain coverage early this morning, expect
showers to fill in from mid morning onward as a cold front moves
across our area. Not seeing a lot of QPF from model consensus, on
average of a quarter to half inch possible through this afternoon,
with highest amounts found over our northern and western zones. Have
removed the chance of thunder from the forecast with temperatures
and moisture are not as high as previously forecast, and a lack of
strong forcing as the front crosses our area by this evening.
Southerly winds will uptick ahead of the front later this morning,
gusting upwards of 20-25 mph. The front will clear our area by early
this evening, turning winds light out of the northwest as drier air
moves in with high pressure building in from the west. Clouds will
stick around tonight with shortwave energy and an upper level jet
residing overhead. Meager cold air advection tonight in the wake of
the front, with temperatures remaining mild for late February,
settling in to the middle 40s surrounding the metro areas and
southward, with upper 30s and lower 40s to the north and west.
&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
High pressure continues to move eastward over the Mid Atlantic on
Monday, with a shortwave trough crossing overhead and pressing off
to our east by Monday evening. This will help skies to finally start
to clear by Monday afternoon, bringing a welcome return of some
sunshine. Did keep slight chance POPs in the gridded forecast for
the first half of Monday for our extreme southern zones as some
guidance wants to keep the frontal boundary just close enough to
have the possibility of light shower activity for these areas.
Temperatures remain above normal on Monday, with highs in the middle
to upper 50s. High pressure will settle overhead Monday night,
coupled with light winds, this allow temperatures a good chance to
radiate under mostly clear skies. Middle to upper 30s will be
prevalent in the metro areas, with lows at or slightly below
freezing along and west of the Blue Ridge. Clear and dry conditions
continue Tuesday and Tuesday night as high pressure dominates the
region, migrating off the Mid Atlantic coast by Tuesday night. Highs
on Tuesday will be in the upper 50s to near 60 degrees, with lows
Tuesday night in the upper 30s to near 40 degrees.
&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
The extended portion of the forecast will start out with high
pressure moving offshore. Warm advection in the return flow will
provide enough lift for scattered showers to arrive during the day
Wednesday. The warm front will approach the forecast area Wednesday
night, and arrive on Thursday as mid level energy runs through
rather fast flow. Therefore, PoPs will spread from central
Virginia across the entire area by Thursday. Temperatures will
be mild for the period.

A deep cyclone will be developing in the Great Lakes/Midwest
Thursday, which will be sending a moisture-rich cold front across
the area Thursday night, with some precip likely lingering into
Friday. Believe that rain will be the dominant type with this
system; cold air will be rushing in Friday PM on gusty northwest
winds after the precip departs. This could provide some upslope snow
showers to the Appalachians Friday night.

High pressure will be building across the area Saturday as the
deepening cyclone continues northeast.

&&

.AVIATION /09Z SUNDAY THROUGH THURSDAY/...
IFR conditions have returned to the terminals early this morning,
owing mostly to low CIGs. IFR VIS is also a possible occurrence this
morning in the wake of earlier rainfall, and shower activity
approaching from the west. A cold front will approach the terminals
after 25/15z, moving east of the area by around 26/00z. As a result,
winds will veer from the south this morning, to the west southwest
this afternoon, and out of the northwest by this evening. Ahead and
along of the front, winds will gust to around 20 knots during the
day, along with MVFR/IFR conditions as -SHRA moves over the
terminals. VFR conditions return in the wake of the front this
evening, continuing through the first half of the work week as high
pressure builds over the region, promoting light winds and only mid
to high level clouds.

Scattered showers will be near the terminals Wednesday, mainly
to the west. While flight restrictions will be possible,
confidence is low. The chances increase sharply Thursday as a
warm front heads north toward the terminals.

&&

.MARINE...
Patchy dense fog is possible early this morning across portions of
our waters, with SCA conditions expected today as a warm front lifts
northward in to the area and a cold front approaches from the west.
Have left the upper portion of the Bay out of the SCA at this time
as not expecting the warm front to travel this far north, thus
keeping wind gusts down in these areas. The cold front will sweep
through the waters this afternoon, potentially accompanied by some
gusty showers. High pressure builds over the waters through the
first half of the work week, resulting in light winds over the
waters with no headlines anticipated.

Small Craft Advisories not anticipated Wed or Thu either, due
mainly to poor mixing in vicinity of a warm front and complex
storm system.
&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...None.
VA...None.
WV...None.
MARINE...Small Craft Advisory until 6 PM EST this evening for
     ANZ532>534-536-537-540>543.

&&

$$
SYNOPSIS...BKF
NEAR TERM...BKF
SHORT TERM...BKF
LONG TERM...HTS
AVIATION...BKF/HTS
MARINE...BKF/HTS


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