Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Baltimore Maryland/Washington District of Columbia
635 am EST Monday Feb 8 2016
low pressure will pass well to our south and east this morning.
Another low pressure system will dive south into the Ohio Valley
today before passing through our area tonight into Tuesday. High
pressure will slowly build toward our area during the middle
portion of the week.
Near term /until 6 PM this evening/...
region remains sandwiched with deepening low pressure offshore
and a second low over the Great Lakes...dipping into the Ohio River
valley by this afternoon. Any precipitation with the low offshore is remaining
well east...and as such expecting generally dry weather through the first
half of today.
A Winter Weather Advisory remains in effect for the western tier of
counties for today. The advisory has the potential to be
extended...or may need to be upgraded to a warning...but will let
day crew determine where the snow totals fall. Concerning the
precipitation...surface low to the west begins to track closer to the middle-
Atlantic...while upper level trough deepens across the eastern US.
This placement of the trough is going to serve as the Avenue for
multiple impulses to move through the region in the coming
days...resulting in increasing precipitation chances. The first of these reaches the
western areas by midday...pushing east through the afternoon. As
such...expecting the precipitation to move in midday out west...briefly
rain/snow or even all rain. As the intensity increases...expecting a
complete changeover to snow corresponding where the advisory is. As
the precipitation pushes east...generally expecting all rain or maybe a
rain/snow mix with highs in the 40s...and lack of any heavier precipitation
holding off till tonight.
Short term /6 PM this evening through Wednesday night/...
tricky forecast still in place for the precipitation tonight through Tuesday
night with many factors still in place. One thing that seems to
have been consistent for many model runs now is the hint of the
heaviest band of precipitation aligning over NE Maryland/southeast PA/north Delaware. As such...am
issuing a Winter Storm Watch beginning tonight and lasting through
Tuesday night with the potential of 7 inches or more of snow in a 24
hour time period for Frederick County east and south to account
for Baltimore metropolitan.
In addition to the previously mentioned surface low to the
northwest...secondary low forms over Virginia tonight...deepening as it
pushes offshore during the day Tuesday. 00z GFS deepens the low more
than the other model solutions...and as such...seeing the highest
quantitative precipitation forecast amts in this latest run. While the placement of the heaviest
band is coming into better agreement...the exact amount of quantitative precipitation forecast and
the resulting snow is still uncertain...though with incrsg
confidence now of seeing at least 7 inches. Timing looks to have
the heavier snow move in second half of tonight...lasting into the
morning...with lighter snow for a period or even a break in the
precipitation...then another burst possible Tuesday afternoon. The other issue at hand
is the thermal profiles and the resulting p-type. Initial
agreement with most areas east of the Blue Ridge seeing a
rain/snow mix first part of tonight. As the precipitation increases in
intensity...generally aftr 03/04z...should see a changeover to
snow for areas mainly north and west of a District of Columbia to Charlottesville
line. Portions of southern Maryland will stay all rain...at least for
tonight. 00z model suite showing cooler wet bulb temperatures...with
northern half of the County Warning Area fully below freezing...and District of Columbia metropolitan with
periods of at or just below freezing. Another thing working
against snow totals is that at first no snow might accumulate with
the warmer temperatures. So a delay in snow accumulation is possible...which
may affect totals.
Precipitation begins to taper off across central Virginia tomorrow night...lingering
along the I-95 corridor and the upslope regions potentially all
the way through Wednesday with the region remaining on the western side of
the low and continuously being impacted by shortwaves progressing
across the mid-Atlantic. While criteria level snow wont be possible over
the eastern areas...advisory level snow might be possible on the
Not to be forgotten...the potential for cold temperatures continues for Wednesday
night...with wind chills below zero becoming more likely for the western
portions of the County Warning Area. Will continue to highlight in the severe weather potential statement with the
potential need of a Wind Chill Advisory.
Long term /Thursday through Sunday/...
the 500 mb trough axis will remain through the weekend...meaning the cold pttn will
remain in place. If anything...we/ll be getting incrsgly colder.
Init round of cold air advection ends Thursday. Gusty northwest winds will relax at that point.
Then another northern stream shortwave and surface reflection tracks S of area lt
Friday...which drags down even colder air for Sat-sun. For the most
part...temperatures will remain subfreezing through the extended. Min-T will be in
the teens...or lower. Sat night would be the coldest night...with possible
subzero readings in the mountains wind chills will be a concern.
The low itself could provide scattered shsn just about anywhere Friday/Friday night.
In addition there will be continued upslope potl Thursday before flow becomes
disrupted. The pttn would support addtl upslope in the wake of the
Aviation /12z Monday through Friday/...
VFR conditions initially today. MVFR ceilings at all terminals by
this afternoon. As the precipitation moves in late today/this evening...
expecting conditions to drop quickly to IFR or lower...especially tonight
with the heavier precipitation. Other than kcho...sites should start as
light rain...transitioning to rain/snow mix...eventually becoming all
snow by Tuesday morning. Kcho looks to remain all rain...though
cannot rule out a brief rain/snow mix tonight. Winds generally
less than 12 kts through the taf period.
Sub-VFR conditions will continue Tuesday with the precipitation...eventually
improving to VFR by Wednesday morning.
Gusty northwest winds will be the primary AVN concern Thursday...W/ some g25kt
likely. Another disturbance may bring more shsn Friday. Way too soon to
tell if this will materialize...but it could bring MVFR/IFR restrictions
if it did.
expecting generally sub-Small Craft Advisory conditions today through a good portion
of Tuesday. Occasional gusts to 20 kts possible this evening...but not
widespread enough at this time to issue a Small Craft Advisory. As the low pushes offshore
and deepens by Tuesday night...expect Small Craft Advisory conditions on at least the
Chesapeake Bay... spreading to all waters on Wednesday.
Small Craft Advisory conds continue into Thursday...then relax as brief hipres crests over the
region ahead of another disturbance Friday.
water levels are actually fairly close to normal across the northern chesepeake
Bay...but departures are starting to be realized across the Middle Bay.
Plus...were still carrying close to a foot above astro normas across
the upper tidal Potomac.
As several rounds of low pressure pass over/east of the mouth of the
Bay...additional water will be drawn in to the estuary. That may
lead to complications as early as the PM tide cycle today...carrying
through Tuesday. Minor inundation would be more likely for both
cycles on Tuesday.
District of Columbia...none.
Maryland...Winter Weather Advisory from noon today to 1 am EST Tuesday
Winter Storm Watch from late tonight through late Tuesday
night for mdz004>006-011-014-503-505>508.
Virginia...Winter Weather Advisory from noon today to 1 am EST Tuesday
WV...Winter Weather Advisory from noon today to 1 am EST Tuesday