Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service Baltimore Maryland/Washington District of Columbia
230 PM EST Wednesday Jan 28 2015

Synopsis...
dry and cold high pressure will linger into early Thursday. A cold
front will swing through the region late in the day on Thursday. A
windy and dry Friday behind the cold front with high pressure
building in for Saturday. Low pressure approaches the region
Sunday and will impact the region Sunday afternoon and overnight
into Monday. The low will move away from the region on
Monday...followed by high pressure building into the region
Tuesday and Wednesday.

&&

Near term /through tonight/...
although the day started off west/ a quick increase of temperatures...it
leveled-off late morning west/ only a slow climb to our maximum which is
likely occurring here in the middle afternoon. Dewpoints across the
area are still in the single digits...not ideal for anything other
than a biting cold feel to the air. Gusty winds in the 20-25mph
range are adding to the discomfort...though they are expected to
gradually subside from the late afternoon hours through the evening. Past
sunset...winds should be only a light northwest breeze. By then...the
very low dewpoints will aide in another sharp temperature drop late
tonight back into the teens and 20s across the area. Low level
decoupling of winds and clear skies will make certain that this
occurs.

&&

Short term /Thursday through Friday night/...
dense high cirrus will start the day on Thursday...W/ a continued
increase in cloud cover from the west over the course of the day.
Temperatures will again gradually climb back into the 20s and l30s through
the morning. A cold front tailing down from a clipper system well to
our north will quickly trudge across the upper Midwest overnight
and into early Thursday. By midday...this feature will be on the
doorstep of the central Appalachians - sliding over the higher terrain
through the early afternoon hours.

A strengthening southerly surface wind will help bump temperatures back up into
the M-u30s for the southern half of the County Warning Area ahead of the frontal passage. Northern Maryland
and just into northern Virginia will still be hanging onto the near or sub-
freezing surface temperatures as precipitation approaches from the west. Plenty of
dry air will greet the incoming precipitation...likely preventing much of
it from reaching the surface until frontal passage toward the late afternoon period.
The lower atmos over the northern half of the County Warning Area will allow for a mix
of rain/snow - possibly sleet - as the initial wave of precipitation
arrives. The northern tier of the County Warning Area /nrn Maryland/ will likely be cold
enough for mainly snow west/ some liquid mixed-in and this is also
where the best potential for snow accumulation will be...albeit
very light. A rain snow mix possible across the tier of counties
on either side of the I-66 corridor and much of the Potomac
Highlands/Blue Ridge.

The front looks to be progressive...so precipitation chances may be
limited to this band and conditions will likely dry out behind the
boundary - minus the Appalachians. The higher terrain will then become
the focus of multi-period upslope snow showers west/ potential
advisory snows for these higher elevation areas along The Spine of
the central Appalachians.

An amplified trough will be across the middle-Atlantic Friday while the
cold front will be well off the East Coast. Positive vorticity advection and a cold pool
aloft may lead to light snow showers and flurries across the
northern middle-Atlantic through Friday afternoon. Northwest winds will be
blustery with gusts up to 40 miles per hour Friday. Higher wind gusts will be
possible across higher elevations along and west of the Blue Ridge
and across northern Maryland. A Wind Advisory may be warranted for
these areas during this time. Cold conditions are expected Friday
with maximum temperatures reaching the low 20s across higher elevations to the
low 30s along I-95. Due to gusty winds...wind chill values will be
in the teens to 20s. Gusty northwest winds will continue Friday night but
subside some with gusts around 30mph into Saturday morning. Forecast min
temperatures Saturday morning will be in the single digits west of the Blue
Ridge to the teens elsewhere. Wind chill values will drop Friday
night and into Saturday morning. Wc advisories may be warranted
north and west of the balt/District of Columbia metros including west of the Blue
Ridge mountains

&&

Long term /Saturday through Wednesday/...
Sat...cold high pressure will be over the middle Atlantic region to
start the day on Saturday. Temperatures will be slowly rebound from reading
in the teens east of the Blue Ridge...while west of the Blue Ridge
temperatures will range from lower teens and even single digits west of
I-81. Fair skies on Saturday ahead of the next storm system.

Sun...high pressure will slide off the coast early in the day.
Meanwhile low pressure over the Missouri Valley will head east.
Moisture will overspread the region and precipitation chances
increase from west to east. The models show SW winds aloft
increasing throughout the day. However temperatures at the
surface will be tougher to erode under cloudy skies. Expecting a
wintry mix on Sunday. Current timing of precipitation suggests the late
morning to early afternoon west of the Blue Ridge...and early to
middle afternoon east of the Blue Ridge. Of course confidence of
timing precipitation this far out is problematic...and model change of
only 6 hours will have big implications on just what type of precipitation
will fall. However am concerned about coming out of a 36 hour of
subfreezing temperatures and models trying to scour out the cold air too
fast. Thus added a chance of freezing rain for about the northern
third of the County Warning Area. Precipitation will continue into the overnight
hours...although the 12z GFS is aggressive moving the precipitation out
quickly Sun night.

Monday...low pressure will moving across the Mason-Dixon line early in
the day bringing end to precipitation. Daytime highs will be below normal by
4-8 degrees-f. There could be a slight chance of lingering snow
shower activity across the region.

Tue-Wed...high pressure builds across the region Tuesday and continues
through Wednesday. Tuesday will be cold...about 10-14 degf below normal. Temperatures
on Wednesday moderate some. Some guidance suggests another low pressure
system moving off the southeast coast. But low confidence on this feature.

&&

Aviation /18z Wednesday through Monday/...
gusty winds and cold temperatures the main weather concern for area airports
into early Thursday. Clear skies but gusty winds mark this aftn's
period...though gusts will drop off toward sunset. Southerly winds will
pick up middle-morning Thursday as a cold front approaches from the west. The
front will carry a mix of rain/snow for a relatively brief window
of the late afternoon/evening as the boundary crosses the region. Timing
and precipitation- types may become more clear closer to the
passage...which is toward later part of the current taf cycle.

VFR conditions expected Friday into Saturday. Gusty northwest winds
20-25kts g 35 kts are expected Friday. Northwest winds will subside some
Friday night but continue out of the northwest 10-15kts g20kts. Northwest winds
around 5-10kts expected Saturday.

Low pressure crosses the region Sunday and sub-VFR conditions are
possible Sunday into Monday as a wintry mix is expected at the
terminals.

&&

Marine...
widespread low-end Small Craft Advisory conds this afternoon will gradually subside from
north to south into the late night hours. A brief lull overnight but
then southerly channeling will begin late the afternoon Thursday ahead of a cold
front. This boundary will swing through the area late Thursday
aftn/eve...switching winds back to northwesterly where they still stay through
the end of the week.

Post-frontal conditions will lead to northwest winds 20-25kts with gusts
around 40 kts Friday afternoon. Gale warnings are likely during this
time. Northwest winds will subside some Friday night but winds should stay
gusty and gales or Small Craft Advisory conditions are likely. Northwest winds will subside
by Saturday.

&&

Lwx watches/warnings/advisories...
District of Columbia...none.
Maryland...none.
Virginia...none.
WV...none.
Marine...Small Craft Advisory until midnight EST tonight for anz530>534-
537>543.
Small Craft Advisory from 1 PM Thursday to 6 am EST Friday for
anz530>534-537>543.
Small Craft Advisory until 6 PM EST this evening for anz535-
536.
Small Craft Advisory from 1 PM to 6 PM EST Thursday for anz535-
536.

&&

$$
Synopsis...gms/smz
near term...gms
short term...gms
long term...has/smz
aviation...gms/has/smz
marine...gms/has/smz

National Weather Service Glossary of Abbreviations