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Area forecast discussion...updated
National Weather Service Baltimore Maryland/Washington District of Columbia
1028 am EST Tue Jan 17 2017

Synopsis...
a stationary front over the Carolinas will move north as a warm
front today. A weak cold front will push through the area early
Wednesday. High pressure returns Thursday followed by an
approaching warm front Friday. High pressure returns again for
Saturday. Low pressure will affect the area to start the new week.

&&

Near term /until 6 PM this evening/...
main batch of steady light warm air advection showers continues
to progress quickly eastward across the area...with radar imagery
showing the back edge nearly east of our office (sterling, va) as
of 1020 am. Generally a tenth of an inch or less...though perhaps
up to a quarter of an inch along the Allegheny Front. Some locally
dense fog developed across portions of North Maryland and eastern WV this
morning...though, most places have risen above a quarter mile as
rain has moved through. Expect that trend to continue in areas
that remain at or below a quarter mile (mainly kfdk). Visible satellite
imagery also showing an area of clearing across the Shenandoah
Valley...any clearing should be short-lived as clouds fill back in
across these areas. Another area of rainfall across eastern WV
will cross the area through early afternoon. By mid-afternoon,
forcing will weaken, although areas of showers will still be
around. Temperatures likely to be stuck in the 40s for a good
chunk of the day with low clouds and scattered rain showers, but
likely to make a run into the 50s late in the day for most with
some drying.

&&

Short term /6 PM this evening through Thursday night/...
we'll be briefly warm sectored this evening and into tonight out
ahead of an approaching cold front that will be crossing the region
during the overnight/early morning hours. With increased low level
wind field, not expecting widespread fog coverage, but some areas of
patchy fog are possible given moist low level conditions. Some
scattered showers also possible until frontal passage. Lows will be
generally in the 40s.

Upper level trough will move across Wednesday morning, keeping
slight to low chances for a few showers across the northern half of
the area, as well as chances for rain and possibly a few snow
showers along the Allegheny Front in upslope flow. Otherwise, will
see developing northwest flow with drying by the afternoon. Highs
Wednesday from 50-60f, except 40s along the Allegheny Front.

High pressure and calm weather then takes hold Wednesday night
through much of Thursday night. Lows in the 30s, highs in the
low/mid 50s. Chances for rain showers then increase late Thursday
night in southwestern areas ahead of the next approaching system.

&&

Long term /Friday through Monday/...
confidence is increasing regarding the possibility of rain Friday.
Both GFS and Euro show an open short wave moving into the forecast
area around 18z. This will probably be pushing north of the region
by Friday evening but the afternoon hours are looking wet. But it
is mid January...and temperatures could be far colder than the
mid to upper 40s expected.

A ridge of high pressure will move over the East Coast Saturday.
Highs should be in the low to mid 50s. Lows Saturday night 35-40.

The ridge will be short lived as the upper atmosphere remains in
fast flow over the Continental U.S.. long range models are showing deepening
low pressure over Texas Sunday...tracking NE and centered over Kentucky
Monday night. This means on southerly flow the mid Atlantic will
be fairly mild - this in contrast to one year ago when the
blizzard of 2016 wracked the region Jan 22-24. Instead of
blizzard conditions this year there'll be a chance of rain on the
22nd...rain likely the 23rd.

&&

Aviation /15z Tuesday through Saturday/...
widespread reductions expected today with low clouds and rain
showers. A mix of LIFR/IFR/MVFR is expected as low stratus and
patchy fog and rain showers move across the taf sites. Highest risk
of LIFR at mrb this morning and BWI later this afternoon. Lowest
risk of IFR at dca. Most widespread rain will occur this morning
into the early afternoon hours. Later tonight, rain showers will
taper off, but additional low ceilings and patchy fog possible,
along with another round of IFR.

VFR will return on Wednesday and persist through Thursday night.

Winds light and variable this morning will become southerly this
afternoon up to about 10 knots, before turning southwest this
evening. A cold front will then cross the region late tonight/early
Wednesday with a turn to northwest winds. Winds will gust up to
around 20 knots Wednesday afternoon.

For Friday an approaching warm front will likely bring rain to
the airports. Ceilings could drop into MVFR range...improving
late in the day. Saturday's weather is expected to be VFR.

&&

Marine...
primarily southerly sub-Small Craft Advisory winds expected through today and
tonight. That being said, with strong low level wind field, may see
some gusts approach Small Craft Advisory-criteria late this afternoon and tonight.
However confidence is too low for issuance at this time.

Winds will then turn to the northwest on Wednesday following cold
frontal passage. Gusts up to about 20 knots expected, and a Small Craft Advisory has
been issued.

Winds will then subside for Wednesday night through Thursday night.

No problems expected on the waters Friday or Saturday.

&&

Lwx watches/warnings/advisories...
District of Columbia...none.
Maryland...none.
Virginia...none.
WV...none.
Marine...Small Craft Advisory from 7 am to 6 PM EST Wednesday for
anz530>543.

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