Area Forecast Discussion
Issued by NWS Sterling, VA

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FXUS61 KLWX 240859
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
359 AM EST Fri Nov 24 2017

.SYNOPSIS...
High pressure will remain over the mid-Atlantic through
tonight. A cold front will cross the region Saturday and move
east of the Chesapeake Bay Saturday night. High pressure moves
back into the area Sunday and remains through the middle part
of the upcoming work week.

&&

.NEAR TERM /THROUGH TONIGHT/...
At 08Z, GOES-16 showing mainly clear skies across much of the
eastern U.S. Temperatures have dropped to the lower-to-mid 20s
outside of the metropolitan centers and western shore of the
Chesapeake Bay.

Skies will be sunny/clear through tonight, with light and
variable winds becoming more southerly this afternoon but still
remaining light. Max and min temps today and tonight,
respectively, will return to normal ranges with the southerly
flow.

&&

.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
On Saturday, a cold front will cross the CWA and exit east of
the Chesapeake late Saturday evening. With deep westerlies,
expecting the shower activity to be limited, as both the GFS and
ECMWF shows decaying rainfall as the front moves east. So am
forecasting scattered showers primarily west of the Blue Ridge,
with sprinkles along and east of Interstate 95. The impact from
this front will be felt in the form of a gust wind, which will
start early Saturday evening, giving wind gusts over the land
20-30 mph Saturday night through mid-day on Sunday.

In favored upslope regions, rain showers will turn to snow
showers early Saturday evening, with a 6-9 hour period of
snowfall producing around an inch of accumulation before
tapering to flurries after midnight Saturday night.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
Long term is a period of transition from the trough-dominated
weather over the weekend as a transient ridge move in from the
western US. For Monday, the northeastern trough will be pulling
east into the Canadian maritimes, with the ridge axis over the
central US and a deep trough over California. At the surface,
this will translate into weakening northwesterly flow as a
sprawling area of surface high pressure moves over the eastern
US. Skies will have few clouds and temperatures will start to
rebound. By Tuesday, the eastern trough will be out of the
picture, with the ridge in the central US having flattened out,
but with an axis which will be over our area. The surface high
will settle just to our southeast and allow a broad
southwesterly flow to bring warmer air northward, with surface
temps rising a bit above normal. By this time, the northern and
southern stream portions of the system out west will be
separating, with the much faster northern stream system moving
into the Great Lakes.

By Wednesday, the northern stream portion rapidly pushes east
into the Canadian maritimes, while the much slower moving
southern stream portion will still be crossing the central US.
For us, this means that the high pressure off to our southeast
will likely remain in control with continued southwesterly flow,
resulting in a yet still milder day - temps likely reaching the
60s. Finally, by Thursday, the southern stream system pushes
east towards us from the central plains, bringing a drop in
temps, greater cloud cover and an increased risk of showers.
This is contingent however on a predictable speed to this
system`s movement, and as it will likely spend some time as a
cut-off upper low over the southwest before making its way
towards our region, the timing and track is more uncertain than
normal.

Either way, bottom line is that temps will be moderating
through the week, with an uncertain chance of rain towards the
end.

&&

.AVIATION /09Z FRIDAY THROUGH TUESDAY/...
VFR all terminals next 24 hours. Light and variable winds become
southerly this afternoon.

Generally VFR Saturday and Sunday, with somewhat stronger and
more gusty south-southwest winds Saturday shifting to northwest
behind a cold front by Sunday. Chance of showers is minimal and
any showers should result in only brief and limited reductions
in cigs and vsby.

VFR overall Monday and Tuesday under high pressure.

&&

.MARINE...
Light winds for another day before another solid Small Craft
Advisory event beginning Saturday evening and continuing through
Sunday. There is even the potential for Gales north of North
Beach including Annapolis and Baltimore with the initial
pressure surge and 35kts as low as 925 mb and strong cold air
advection over the warmer waters of the Chesapeake.

Most likely sub SCA winds for the bulk of waters on Monday as
high pressure pushes east across the area. By Tuesday, southerly
channeling on the back side of the high may result in small
craft advisory conditions.

&&

.TIDES/COASTAL FLOODING...
Anomalies have crept back up over much of our waters, but
appear to have leveled off somewhat. With light winds expected
again today, do not expect major fluctuations, so kept BTA
steady and used a blend of Estofs and ETSS. Do not expect any
coastal flooding, but sensitive sites may touch action stage.
Will need to monitor the anomalies in case they do start rising
again. With a southwest wind expected on Saturday, will also
need to watch potential for an additional increase in anomalies
as water starts piling up in the northern bay. By Sunday,
northwest flow should help lower anomalies again.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...None.
VA...None.
WV...None.
MARINE...None.

&&

$$
SYNOPSIS...Lee
NEAR TERM...Lee
SHORT TERM...Lee
LONG TERM...RCM
AVIATION...Lee/RCM
MARINE...Lee/RCM
TIDES/COASTAL FLOODING...



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