Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Baltimore Maryland/Washington District of Columbia
issued by National Weather Service Mount Holly New Jersey
949 am EDT Tuesday Oct 13 2015
a cold front will pass through the region today. High pressure
will build overhead tonight through Thursday. Another cold front
will pass through the area Friday and Canadian high pressure will
build overhead during the weekend.
Near term /through tonight/...
a trough of low pressure is moving through the region this
morning with a narrow band of showers along it. The showers have
been weakening as they move east toward the region. This is due
to most of the middle and upper- level support with the trough
remaining off to our north... any additional precipitation amounts
will be light. The best chances of a light shower or two will be
from Baltimore north with very light quantitative precipitation forecast. Near term temperatures
and probability of precipitation will be adjusted slightly for the 10:30 am update based
on ongoing trends.
A cold front will pass through the region from west to east this
afternoon...but most areas will remain dry during this time due to
subsidence behind departing shortwave energy. Also...with some
sunshine expected and a downsloping westerly flow behind the cold
front it will turn out to be another warm afternoon. Maximum temperatures are
forecast to range from the 50s along the Allegheny Front to the
middle and upper 70s near Washington and Baltimore. The forecast
leans toward the warmer side of guidance due to the downsloping
flow and sunshine expected this afternoon.
The cold front will move off to the east tonight while high
pressure builds into the Midwest. A west to northwest flow will
usher in cooler conditions during this time. Min temperatures will range
from the upper 30s along the ridge tops of the Allegheny Highlands
to the middle 50s in Washington and Baltimore.
Short term /Wednesday through Thursday night/...
high pressure will build into the Ohio Valley Wednesday before
settling overhead Thursday into Thursday night. Dry and cool
conditions are expected during this time along with sunshine. It
will be breezy Wednesday with winds gusting around 20 to 25 miles per hour
and there may be scattered/broken cumulus deck as a weak upper-level trough
Long term /Friday through Monday/...
00z model showing slightly quicker progression of the cold front
Friday...with it now offshore by 00z Sat. Continues to be mainly a
dry passage for most of the County Warning Area. Have slight chance probability of precipitation for
northwestern areas and along the Mason- Dixon...closer to the
upper level support as well as possible terrain influences. Any precipitation
that does form will quickly end by Friday night...with broad high
pressure building in for the weekend.
Dry weather for the weekend...with well below normal temperatures...and
frost/freeze potential becoming the big story. Strong surge of cold air advection over
the area as the high builds in...with the northern stream trough
dipping well south of the area. While there still remains some
differences in the temperatures...with the GFS on the cooler side than the
European model (ecmwf)...the agreement is there of seeing 850mb temperatures dropping below
0 degrees celsius. Lows Friday night still predominately in the
40s...with spots out west hitting the middle 30s. With light winds and
clear skies...strong radiational cooling should lead to most of the
area seeing sub-40 Sat and sun nights...with a good portion of the
Potomac Highlands dipping to near or below freezing. Will have to
continue to monitor with the potential for frost/freeze products.
Highs Sat and sun will hover in the 50s.
Ridging building in from the west late in the weekend will nudge the
trough on east...allowing for a warm up to start the week. High
pressure dominating the region keeps things dry and quiet.
Aviation /14z Tuesday through Saturday/...
VFR conditions are expected most of the time through Thursday
night. Any shower should be brief and confined to the BWI area
late this morning. West to southwest winds will gust around 20
knots this afternoon.
West to northwest winds are expected behind a cold front tonight
through Thursday night. Gusts up to 20 knots are possible
Wednesday afternoon and again Thursday afternoon.
VFR conditions for the end of the week through the weekend.
a southwest flow has increased ahead of an approaching cold front
this morning with current gusts already around 15 knots. A Small
Craft Advisory is in effect for the Maryland Chesapeake Bay south
of Pooles Island and lower tidal Potomac River this morning. The
Small Craft Advisory is in effect for all of the waters this
afternoon and evening as the mixing layer increases. A cold front
will pass through the waters later this afternoon into this
evening. West to northwest winds are expected behind the boundary
tonight through Thursday. A Small Craft Advisory is in effect for
portions of the waters tonight and Wednesday. A Small Craft
Advisory may be also be needed for Wednesday night and Thursday.
Small Craft Advisory gusts becoming more likely for Friday with incrsg southerly flow
ahead of the cold front. A brief lull is expected as the front
passes Friday evening. Strong cold air advection will keep gusty northwest winds over the
water...with Small Craft Advisory conditions lasting through the weekend for portions of
a southerly flow has increased a bit over the waters. Anomalies
are around one half to three quarters of a foot above normal early
this morning. The anomalies may increase a bit today due to the
southerly flow...but water levels are expected to remain below
minor flooding thresholds. Since the flow will be slightly west of
south...this should prevent anomalies from increasing too much.
Latest guidance along with the forecasted levels remain below
minor flooding thresholds...but it will be close for sensitive
areas such as Annapolis and Washington District of Columbia this afternoon/evening.
An offshore flow will develop behind a cold front tonight and
anomalies will quickly drop.
District of Columbia...none.
tides/coastal flooding... bjl/Sears