Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

fxus61 klwx 171400 

Area forecast discussion
National Weather Service Baltimore Maryland/Washington District of Columbia
1000 am EDT Thu Oct 17 2019

low pressure departing to our northeast will rapidly intensify
today before high pressure returns for Friday and into
Saturday. Low pressure may impact the area Saturday night into Sunday
before a cold front approaches early next week.


Near term /through tonight/...
a Wind Advisory continues for the higher elevations through 6
PM this evening. Strong westerly winds will lead to continued
upslope shower activity today, with some snow expected above
3000 feet. When all is said and done, could see an inch or two
on the highest peaks out west. Additionally, a deepening surface
low, located near Long Island, will continue to strengthen
today and move off to the northeast. Gradient winds across
northern and central Virginia and all of Maryland are expected to gust
around 40 knots as a result, a Wind Advisory is in effect for
those areas through early this evening. A chilly day today,
with highs only in the upper 50s to near 60, paired with the
strong winds.

As the aforementioned low moves away from the area to the
northeast, winds will gradually diminish across the region
tonight into Friday. Slightly cooler tonight as well, with lows
in the low 40s east of the Blue Ridge, and mid 30s to low 40s
west of the Blue Ridge. Higher ridge tops will see lows in the
upper 20s to low 30s. Upslope activity continues tonight as
well, but should begin to die down.


Short term /Friday through Saturday/...
by Friday, all shower activity should be finished out west, and
winds will be substantially less. Winds will still be gusting in
the 20-25 mph range on Friday across northern areas, but this
will quickly diminish into the evening as high pressure builds
directly overhead. Highs on Friday will be slightly cooler than
average, with temps in the low to mid 60s.

Friday night will likely be the coldest night of the forecast
period across the entire area. Frost/freeze headlines will be
needed Friday night west of the Blue Ridge, with widespread lows
in the low to mid 30s. Warmer temps along/east of I-95, with
lows closer to the low 40s. Between I-95 and the Blue Ridge,
things are a bit less certain, as temperatures will be close to
frost advisory criteria, but will wait on issuing that for now.

High pressure will shift offshore Saturday, leading to warmer
temperatures into the mid 60s. No rain is expected throughout
the day on Saturday.


Long term /Saturday night through Wednesday/...
low pressure in the southern stream of the jet will track through
the southeastern Continental U.S. Saturday night and then most likely off the
mid-Atlantic coast Sunday. There may be enough warm and moist air
that overruns cooler air over our area, bringing the chance for
rain. Confidence is still low given that there is still some
divergence among guidance as to the timing and how far north the
moisture will make it, but as of now it appears that the best chance
for rain will be later Saturday night through midday Sunday.

A storm system will track east of The Rockies Sunday night into
Monday and it will intensify as it does so. This will cause a
longwave upper-level trough over the central Continental U.S. With upper-level
ridging over our area. Surface high pressure may wedge into the mid-
Atlantic briefly which can bring dry conditions for Sunday night and

However, as the trough shifts east, so to will a stronger cold
front. Ahead of the cold front, a southerly flow will allow for
warmer conditions along with deep moisture advection.
Unseasonably warm conditions are likely Tuesday along with
increasing chances for rain. High pressure will return for the
middle portion of next week with drier and more seasonable


Aviation /14z Thursday through Monday/...
VFR conditions will prevail over the next several days, as high
pressure builds into the region Friday into Saturday. However,
gusty west-northwest winds will be the main threat today, especially at the
northern terminals, where gusts of 35-40 knots are expected.
Winds at cho will be slightly lighter, as the deepening surface
low will be farther away than at the other terminals, but could
still see gusts up to 30 knots. Winds will decrease Thursday
night and Friday, but still gust in the 15-20 knot range
throughout the day on Friday.

As high pressure settles overhead Friday night into Saturday,
winds will be light across the entire area, with no clouds or
precipitation to speak of.

Low pressure may bring some rain and subvfr conditions
Saturday night into Sunday. High pressure may briefly return
for Sunday night and Monday, but low clouds and or fog may be stuck
underneath the subsidence inversion.


Gale Warning will continue through early this evening, as a
strong low pressure system intensifies to the northeast.
Northern portions of the Bay will see stronger gusts (near 40
knots), as the low will be closer to that region, with a tighter
pressure gradient. Winds will relax somewhat later in the
evening, but there is still the chance that the Northern Bay
could see gale conditions later into the evening, but confidence
is not high enough at this time, so going with a Small Craft
Advisory for all waters. Winds will continue to be gusty through
Friday, remaining above Small Craft Advisory criteria through Friday evening.

High pressure builds overhead later Friday evening, quickly
bringing winds below Small Craft Advisory criteria finally. High pressure will keep
winds light on Saturday as well.

Low pressure will likely pass by to the south and east later
Saturday night into Sunday. An Small Craft Advisory may be needed for portions of
the waters during this time. High pressure may briefly return for
Monday before a cold front impacts the waters Tuesday.


Tides/coastal flooding...
a strong offshore flow will cause anomalies to continue to fall
sharply today. Tidal blowout conditions are possible later today
into Friday near times of low tide. The offshore flow will weaken
Friday night and turn onshore for the weekend. Anomalies will likely
increase sharply during this time, and tidal flooding is possible
this weekend.


Lwx watches/warnings/advisories...
District of Columbia...Wind Advisory until 6 PM EDT this evening for dcz001.
Maryland...Wind Advisory until 6 PM EDT this evening for mdz003>006-011-
Virginia...Wind Advisory until 6 PM EDT this evening for vaz028-031-
WV...Wind Advisory until 6 PM EDT this evening for wvz050>053-501-
Marine...Small Craft Advisory from 6 PM this evening to 6 PM EDT Friday
for anz530>543.
Gale Warning until 6 PM EDT this evening for anz530>543.


near term...cjl/jmg

National Weather Service Glossary of Abbreviations