Area Forecast Discussion
Issued by NWS Sterling, VA

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FXUS61 KLWX 160228

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
928 PM EST Thu Feb 15 2018

A cold front will cross the area Friday morning. High pressure
will build north of the area Friday night. Low pressure will
then pass to the southeast Saturday night. A second area of high
pressure will return early next week before the next cold front
affects the area during the middle of next week.


Radar imagery as of 9 pm Thursday shows a band of light to
moderate rain showers moving east across southern Pennsylvania.
Some of these rain showers have reached into northern Maryland
and the eastern West Virginia Panhandle. Rain amounts across
southern Pennsylvania appear to be averaging one half to one
inch in the moderate rain, but lesser amounts in the light rain.
Surface observations out of Cumberland, Thurmont, and
Westminster in western and central Maryland indicate a northerly
wind around 10 knots with gusts between 20 to 25 knots as these
rain showers sagged across these areas during the last hour or
two. Rain amounts have been averaging a couple of hundredths of
an inch to up to one quarter of an inch. Temperatures have also
dropped between 3 and 7 degrees in the past hour or two due to
the cooling of the rain falling in these areas. Just to the
south of these pressing rain showers, temperatures remain in the
upper 60s to near 70 with a persistent southwest wind.

As these showers move south and east during the next couple of
hours, so will the sharp cold front that is currently across
northern Ohio and central Indiana. Through the remainder of the
night, additional rain showers will develop along and ahead of
the cold front and move east into our region. Rain amounts will
average between one quarter of an inch in southeastern zones to
as much as an inch in the northwestern zones. No flooding is
anticipated as the southwest winds at the surface, westerly
winds aloft, and a cold frontal passage timing should offset
this factor. The cold front should cross our area around 09z and
move to our south by 15z Friday morning.

As for the remainder of the day Friday, cold high pressure will
build in from the west. Temperatures, dewpoint temperatures, and
available moisture will be on the decrease as a breezy northwest
wind ushers in drier air throughout the day. Friday`s high
temperatures may actually occur around midnight tonight or
shortly thereafter as we look at the cold front to pass through
the area in the middle of the night Thursday night/early Friday


Friday night into Saturday morning will be influenced by cold
high pressure. Clearing skies Friday night and dry air in place
will transition to mostly sunny skies Saturday morning.
Temperatures Friday night will fall from near 50 around sunset
to the upper 20s by sunrise Saturday morning. Also, expect a 10
to 15 degree drop in our dewpoint temperatures.

We should encounter increasing clouds late Saturday morning
through Saturday night as high pressure moves to the northeast
and brings the wind direction out of the northeast then the
southeast rather quickly. At the same time, an area of low
pressure is expected to form along the mid-Atlantic Coast before
pushing out to sea.

The coastal low is expected to spread snow and sleet from
southwest to northeast Saturday through Saturday evening. The
low will be moving rather quickly, despite it being a coastal
low. Therefore, wintry precipitation may only persist for a
couple of hours. Snow to liquid ratios will be generally around
5 to 1, or less where sleet mixes and between 7 to 10 along the
Mason Dixon line where precip remains as snow through the
event. Snow amounts of an inch or less are expected south of
I-66 with 1-3 inches north of there. Precip ends by midnight
Sat night.


High pressure builds overhead on Sunday bringing dry conditions
over our region into Sunday night as southerly flow settles in.
A low pressure system moving towards the Great Lakes will push
a warm front over or nearby on Monday that could bring unsettled
weather over our area. A cold front will then stall to our
northwest Tuesday into Wednesday and keeping southerly flow over
us. Depending on how close it stalls, we could experience some
precipitation. The front will then slowly move across on
Thursday keeping the chance of precip over our CWA.

A warming trend will be in place in the long term period as high
temperatures will be gradually increasing from the 40s and 50s on
Sunday into near the 70s Tuesday and Wednesday. High temperatures
will drop around 10 degrees on Thursday due to the front.


Rain showers expected overnight as a cold front crosses the
area with brief cigs restrictions into MVFR category. Despite
some of these rain showers briefly shifting winds to the north
and gusting to around 25 knots this evening near MRB and MTN,
the primary wind shift is expected around 09Z with gusts around
20 to 25 kts expected.

Snow expected late Sat at onset with a quick transition to
snow/sleet mix Sat evening with precip ending by midnight Sat
night. Flight restrictions are likely late Sat and Sat evening.

VFR conditions are expected during on Sunday as high pressure
builds overhead. Periods of sub-VFR conditions possible Monday
into Tuesday as frontal boundaries affect our area, but it will
depend on how close they move.


A cold front will approach the waters overnight before passing
through Friday morning. Instability is limited...but strong
winds remain aloft. A line of showers will be capable of mixing
some of those winds down early Friday morning. Special Marine
Warnings may be needed...but confidence is low at this time due
to the limited instability.

Southerly winds tonight into Friday morning will turn to the
northwest behind the front later Friday. A Small Craft Advisory
remains in effect for the waters during this time. Winds may
continue to gust past SCA criteria Friday night...but winds
should diminish Saturday and remain below SCA criteria through
early next week.

Winds are expected to remain below SCA criteria from Sunday
into Monday night, therefore no small craft advisory expected
these days. Winds will increase later on Tuesday, which will be
monitored in case a SCA is required.


MARINE...Small Craft Advisory until 7 PM EST Friday for ANZ530>543.


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