Scientific Forecaster Discussion
fxus61 klwx 161904
Area forecast discussion
National Weather Service Baltimore Maryland/Washington District of Columbia
304 PM EDT Wed Oct 16 2019
low pressure will intensify today as it moves off the mid-
Atlantic coast. A strong cold front will pass through late this
afternoon into this evening while the rapidly intensifies off to
our northeast. The low will move toward New England later
tonight and Thursday before high pressure returns for Friday and
into Saturday. Low pressure may impact the area Sunday before a
cold front approaches next week.
Near term /until 6 am Thursday morning/...
cold/occluded front crossing the area at this time. Southern stream
low pressure across southeast virginia; this will be the feature
that will eject into the Atlantic and deepen rapidly. The back edge
of the rain also crossing the area. While its possible for a few
additional showers in the dry slot, the bulk of the rain has
fallen. Due to shear, some interesting structures present, but
air mass is stable. Will be adjusting late afternoon precip
Wind forecasts aloft increasing mostly as projected, but the 12z
cycle suggesting the core of winds closer to 40-50 kt. The concern
remains how much will mix, as momentum Transfer typically less than
ideal coincident with a nocturnal inversion. Keeping a forecast
near mean layer mixed, which is still 25-30 kt almost areawide
and up to 40kt across the ridge tops. No changes to wind
advisories, but admittedly it will be close in spots.
Temperatures will drop behind the front tonight as cold advection
increases. However, am skeptical as to how quickly the boundary
layer cools; NAM may be too cold. Ingredients for upslope
precipitation still in place, and it will be cold enough for some
wet snow to mix, especially after midnight. However, have scaled
back how much accumulating snow this might be...especially since
the ground should remain warm.
Short term /6 am Thursday morning through Friday night/...
deep cyclogenesis will be the primary weather factor Thursday. The
pressure gradient will be favorable for rather deep mixing. How
deep, and how strong the winds will be, depends upon the computer
model. Have increased wind forecasts for Thursday, producing gusts
barely below advisory threshold for Metro Baltimore (and for that
matter, most of maryland). The gradient will have less of an
influence south and west...but still a windy day. Upslope
precipitation will continue, but temperatures will be too warm for
anything other than light rain.
High pressure will build for Friday. Both Thursday night-Friday
morning and Friday night will be chilly, especially Friday
night when winds will be light and radiational cooling will be
Long term /Saturday through Wednesday/...
high pressure sitting over our region Saturday will start to shift
northeastward out of our region. Winds will slowly become southerly
to southeasterly ahead of an approaching coastal system.
Temperatures during the day will be near normal in the mid to upper
60s with overnight temps in the 40s to low 50s.
The Sunday to Monday period remains very uncertain at this time. The
models have a tropical low forming over the Gulf of Mexico and
moving northward through the southeastern US and up along the
eastern Seaboard. There remains quite a bit of uncertainty on how
far this coastal system reaches into our region. At this time there
remains a threat for another system late Sunday into Monday. This
system has the potential to bring significant rain to our area.
Models indicate the potential for pw's as high as 1.5 to 1.7 which
in October is pretty high. We will need to continue to monitor the
model trends to determine the exact track of this system. At this
time the main threat area for the coastal storm will be central
Virginia and southern Maryland.
A strong cold front is forecast to move through our region Tuesday
into Wednesday. Depending on the timing and track of the coastal low
the day before, these two systems could merge to bring significant
amount of precipitation to our region again on Wednesday. This
system looks to move fully through our area by Wednesday morning.
Behind the frontal passage temperatures are expected to be near or
slightly below normal on Wednesday.
Aviation /19z Wednesday through Monday/...
flight conditions fluctuating at this time, but ample IFR abounds.
Conditions will be improving for the rest of the afternoon into
tonight. VFR should prevail for the remainder of the week.
Northwest winds will increase before dark, with widespread 25-30 kt
gusts expected through Thursday afternoon. Some gusts of 35 kt (or
perhaps a pinch more) possible. Winds will crease Thursday night and
The majority of our region should experience mainly VFR conditions
Saturday and Sunday. The main threat for restrictions will be in
central Virginia and the cho terminal. VFR conditions expected at
a cold front crossing the waters at this time, with sporadic gusty
winds. Have a Small Craft Advisory in place. Any higher gusts (or
waterspouts) will trigger special marine warnings. This threat
should be ending by dark.
Synoptic winds will increase this evening, and be strong/gusty
through Thursday. Already had a Gale Warning for the waters
tonight. Have expanded it to all waters for Thursday...40 kt
Northern Bay, 35 kt Drum Point-Smith Point/Tangier Sound/Potomac
River (further away from rapidly strengthening nor'easter).
Small craft conditions likely will linger into Thursday night
and perhaps Friday.
Winds will remain light on Saturday. Winds above the 18 knot
threshold will be possible on Sunday. Small craft advisories may be
needed on Sunday.
water levels have increased substantially today. Have expanded
coastal flood advisory for most areas Baltimore south as well as
Dahlgren gauge and SW District of Columbia on the Potomac for the PM tide cycle.
Strong northwest winds tonight will then lead to blow-out
conditions; threat should last for only one cycle.
District of Columbia...coastal flood advisory from 8 PM this evening to 1 am EDT
Thursday for dcz001.
Maryland...Wind Advisory from 6 PM this evening to 2 PM EDT Thursday for
Coastal flood advisory until 10 PM EDT this evening for mdz014.
Coastal flood advisory until 9 PM EDT this evening for mdz016.
Coastal flood advisory until 7 PM EDT this evening for mdz017-
Coastal flood advisory until 11 PM EDT this evening for mdz011.
Virginia...Wind Advisory from 6 PM this evening to 2 PM EDT Thursday for
Coastal flood advisory until 9 PM EDT this evening for vaz057.
WV...Wind Advisory from 6 PM this evening to 2 PM EDT Thursday for
Marine...Small Craft Advisory until 6 PM EDT this evening for
Gale Warning from 6 PM this evening to 6 PM EDT Thursday for