Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Baltimore Maryland/Washington District of Columbia
604 PM EST Monday Dec 9 2013
an upper-level disturbance will pass through the region late tonight
through Tuesday morning. High pressure will build overhead Tuesday
night through the end of the week.
Near term /through Tuesday/...
dense fog advisory issued for this and overnight that includes
the north-central Maryland...the northern Shenandoah Valley and Nova. The area
has been socked in stratus/fog all day as dewpoints are near or
just above freezing over a ground fresh snow/ice pack. May
eventually need to expand the dense fog advisory eastward toward the
cities and southern Maryland...but confidence in dense fog is still too low
to issue right now.
weak high pressure will build overhead late this afternoon and
evening. Moisture underneath the subsidence inversion will result in
low clouds during this time...mainly near and east of the Blue Ridge
mountains. A light northwest flow may dry things out later this
evening...causing low clouds to possibly dissipate.
A potent shortwave and jetmax located over the central Continental U.S. Late
this afternoon will pass through our area late tonight through
Tuesday morning. The forcing from this system will be strong...and
this will cause a band of moderate to locally heavy precipitation to
quickly overspread our area. Cold advection and evaporative cooling
should be enough for precipitation to fall in the form of snow for
most locations. However...there will be a warm layer aloft that will
cause sleet and freezing rain across portions of central Virginia
and southern Maryland. Precipitation across these areas should
change to snow Tuesday morning before ending. Any ice from freezing
rain should be under one tenth of an inch.
Latest guidance shows the potential for mesoscale banding...which
will cause high precipitation rates. However...certainty in exactly
where that band sets up is still high. A Winter Weather Advisory
is in effect for the entire area late tonight into early Tuesday
afternoon. The morning rush hour will be impacted and snowfall
rates around one to two inches per hour will cause dangerous
travel conditions. The advisory may need to be upgraded to a
warning for portions of the area...depending on exactly where the
heavier bands set up and how strong they are. Will continue to
monitor during evening and overnight shifts.
Precipitation will quickly during the early and middle afternoon
Short term /Tuesday night through 6 PM Tuesday/...
high pressure will build east into the middle Atlantic region Tuesday
night through Wednesday night. Aside from some upslope cloud cover
and a slight chance of higher elevation snow in the Potomac
Highlands...dry and cold conditions expected across the region. Low
temperatures will drop into the low to middle 20s near the Chesapeake
Bay...the middle to upper teens from the Shenandoah Valley to
southern Maryland...and the single digits in portions of the Potomac
Highlands. Winds will gust 20 to 25 miles per hour Tuesday night before
diminishing Wednesday and Wednesday night.
Long term /Tuesday night through Monday/...
high pressure across the area for Thursday and Friday. Thursday should see quite a
bit of sunshine but it will be on the cool side west/ high temperatures only in
the u20/l30s. Thursday night should be cold west/ lows from the teens to the
High pressure remains over the middle Atlantic Fri: continued M sun skies west/ temperatures
in the 35-40 range. The high will move offshore Sat which will put the
area in a warmer return flow. Highs in the u30s to m40s. The next weather
maker looks to move into the area Sat or Sat night as a short WV
tracks east out of the southern stream across the Tennessee vlly. Models are forecasting
highs near 50 Sat...but model performance long range on temperatures has not
been great lately - for the weekend past models were nearly 10 degrees too
warm at 5-6 days out. For now will keep forecast highs in the l40s Sat.
Wintry mix possible Sat...but confidence in specifics is low.
The short WV is expeceted to move offshore Sat night. Brzy conds possible
Sunday...then high pressure returns to start the next weak.
Aviation /00z Tuesday through Saturday/...
IFR/subifr conditions are expected late this afternoon and evening
across most of the terminals. Ceilings/visibilities may improve later this
evening into the overnight hours before a band of snow/sleet
overspread the terminals early Tuesday. Ceilings/visibilities will quickly drop
to IFR/subifr levels during this time. Conditions will improve
Tuesday afternoon and Tuesday night as drier air moves in.
Skies will clear Tuesday night with partial sunshine Wednesday then
a few clouds Wednesday night. VFR conditions Tuesday night through
Northwest to west northwest winds will gust over 20 knots Tuesday
night before diminishing Wednesday and Wednesday night when high
pressure builds overhead.
High pressure over the region Thu/Fri. Diminished ceilings/visibilities possible late Sat
ahead of the next system to impact the region.
surface high pressure will build toward the waters through Tuesday.
Northwest winds are expected during this time. Wind gusts may
approach Small Craft Advisory criteria Tuesday afternoon. Have capped gusts around 15
knots for now. A period of snow/sleet is expected Tuesday morning
and this will reduce visibilities to less than one mile.
A Small Craft Advisory is in effect for all waters Tuesday
High pressure over the waters Thursday and Friday. A disturbance move into over
the waters Sat. Small Craft Advisory level winds expeceted Sunday.
District of Columbia...Winter Weather Advisory from 3 am to 2 PM EST Tuesday for
Maryland...Winter Weather Advisory from 3 am to 2 PM EST Tuesday for
Dense fog advisory until 2 am EST Tuesday for mdz003>007-009-
Virginia...Winter Weather Advisory from 1 am to 2 PM EST Tuesday for
Winter Weather Advisory from 3 am to 2 PM EST Tuesday for
Dense fog advisory until 2 am EST Tuesday for vaz028-030-031-
WV...Winter Weather Advisory from 1 am to 2 PM EST Tuesday for
Winter Weather Advisory from 3 am to 2 PM EST Tuesday for
Dense fog advisory until 2 am EST Tuesday for wvz052-053.
Marine...Small Craft Advisory from 6 PM Tuesday to 6 am EST Wednesday