Area Forecast Discussion
Issued by NWS Sterling, VA

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FXUS61 KLWX 162030
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
330 PM EST Fri Feb 16 2018

.SYNOPSIS...Cold front will push south of the area this evening.
High pressure will briefly build north of the region tonight,
then a wave of low pressure will pass to the south Saturday.
High pressure will return briefly again on Sunday before another
storm system approaches from the west early next week.

&&

.NEAR TERM /THROUGH TONIGHT/...

Cdfnt has cleared much of the area except across southern MD
with any showers expected to move out of the area by 6PM.
Clearing and turning colder tonight as high pressure builds to
the north over PA with lows dropping into the 20s and 30s.

&&

.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...

High clouds associated with next wx system will be on the
increase around daybreak Sat with a high dense overcast
developing by midday. Model trends have remained fairly
consistent with low pres developing along the NC coast Sat
evening and moving quickly out to sea late Sat night. Precip
onset looks to be late morning across the southwest with precip
spreading quickly northeast during the afternoon. Precip totals
are expected to be generally around half inch for a 6-hr
duration precip event. P-type fcst continues to remain
challenging due to mixed precip potential with models showing
temps at the warm nose of +1C or +2C south of the I-70 corridor
in central MD and south of I-66 and U.S.50 in western VA. Snow
at onset will likely change to sleet south of those locations
with all snow across north central MD and rain across southern
MD. Given warm nose of only +1C or +2C, strong omega and wet-
bulb cooling could overcome that shallow warm layer and make
the layer isothermal potentially resulting in more snow than
what is currently forecast. So, if the fcst were to go wrong it
would probably be for more snow than what is fcst, but latest
thinking is that warm sfc temperatures and high likelihood of
sleet mixing in will cut down on snow totals significantly. The
chance of freezing rain has decreased significantly due to warm
antecedent conditions and shallow warm layer aloft. So, fzra was
removed from the fcst. Precip will end around 10PM as a brief
period of light rain south of I-70 and remaining all snow north
of there. Please see snow maps in our website for specific
snow/sleet amounts.

High pressure builds for Sun with any snow melting rather
quickly as temps rise into the upper 40s and low 50s.

&&

.LONG TERM /MONDAY THROUGH FRIDAY/...

High pressure will be moving away from the coast as return flow
settles in. Isentropic lift will allow showers over our area
through the day and possibly into the night. Temperatures will
remain well above freezing, with highs reaching the 50s.

A cold front will stall to our west Tuesday into Wednesday. We will
remain in the warm sector and high temperatures both days will reach
the 70s. Showers associated to this front are more likely towards
the western counties of our CWA Tuesday and part of the day
Wednesday. The front will then moves across slowly Wednesday night
or Thursday. The front will then stall to our south as waves of low
pressure tracks along it and maintain the unsettled weather over our
area Thursday and into Friday. Temperatures will decrease behind the
front, but not enough to bring p-type concerns. High temperatures
will be in the 50s.

&&

.AVIATION /20Z FRIDAY THROUGH WEDNESDAY/...

Gusty winds ending late this evening. Wintry precip expected
Sat afternoon with IFR conditions likely in the evening. Precip
ends by midnight Sat night but low cigs will likely persist
until daybreak Sun.

Periods of sub-VFR conditions possible Monday into Monday night
as a front moves through our area. VFR conditions expected
Tuesday and Wednesday. Some sub-VFR periods possible late on
Wednesday as showers move through.

&&

.MARINE...

SCA conditions expected through tonight. Winds 10kt or less Sat
through Mon.

Winds are expected to remain below SCA criteria on Monday, then
they will increase on Tuesday but are not expected to reach SCA
criteria. Similar conditions expected on Wednesday, therefore
no small craft advisory expected these days.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...None.
VA...None.
WV...None.
MARINE...Small Craft Advisory until 10 PM EST this evening for ANZ530-
     531-535-536-538>540.
     Small Craft Advisory until 3 AM EST Saturday for ANZ532-533-
     537-541-542.
     Small Craft Advisory until 6 AM EST Saturday for ANZ534-543.

&&

$$
SYNOPSIS...LFR
NEAR TERM...LFR
SHORT TERM...LFR
LONG TERM...IMR
AVIATION...IMR
MARINE...IMR/LFR



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