Area Forecast Discussion
Issued by NWS Sterling, VA

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FXUS61 KLWX 190758

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
358 AM EDT Wed Oct 19 2016

A weak cold front will stall out over the area late today into
tonight before retreating to the north on Thursday. Another,
stronger cold front will cross the area Friday. An upper-level
trough will pass through the area Saturday and high pressure will
build into the region for Sunday. A reinforcing cold front will
pass through the area Sunday night into Monday.


Surface analysis depicts high pressure centered over the SE
CONUS...leading to light S/SW flow across much of the area. Cold
front currently approaching the Mid-Atlantic from the N/NW, with
light showers along/ahead of it. Aloft...nose of mid-/upper-level
ridge extends into southern/central VA.

While the showery activity across PA is expected to weaken and
dissipate as it slowly works cover near front
will gradually work into the area through the day today. This
will lead to a tricky temperature cloud cover could
temper warming across parts of the area this afternoon. General
consensus is for E/W oriented front to be bisecting the northern
part of the CWA by afternoon. Thus, while M/U80s are forecast
across central VA...locations near the Mason-Dixon line and across
northern/central Maryland line could remain in the 70s.

There could also be a few showers that develop this afternoon
across the Highlands in an area of enhanced convergence near
frontal boundary. This scenario is supported by most convective
allowing models including many members of NSSL-/NCAR-WRF ensembles
as well as the HRRR. While non-zero...thunder chances are low, as
elevated warm layer is present near 12 kft which would likely
prevent strong updrafts from penetrating into favorable
temperature regions for lightning.


Cold front that was draped over the area Wednesday will lift back
north as a warm front Thursday...leaving our area in the warm
sector. Lack of forcing will leave most areas dry through much of
Thursday. Cloud cover across northern portions of the area could
again temper warming in these areas. Additionally...H5 heights
will be falling during the day as riding breaks down in response
to potent vorticity maxima approaching from the west. This should
also help to keep most places a few degrees cooler than previous

Coverage of showers will increase from west to east Thursday night
into Friday as a strong cold front approaches. Anafrontal nature of
precipitation will likely keep rainfall amounts on the low-
end...with most places receiving less than a half an inch during
the entire event (greatest totals likely across the higher
terrain in the west).


Low pressure will track up toward Nova Scotia Saturday while high
pressure builds over Ohio Valley. An upper-level trough will pass
through the area during this time. A tight gradient between the
departing low and the high to the west will cause windy conditions
and the northwest flow will cause much cooler conditions compared
to recent days. A bkn stratocu deck is possible Saturday as the
trough swings through. A couple showers cannot be ruled out...but
much of the day should be blustery and dry.

High pressure will Saturday night into Sunday. Dry and chilly
conditions are expected Saturday night. Frost in the valleys and a
freeze on the ridge tops are possible. Confidence in the frost is
low since the gradient wind may be strong enough to prevent
radiational cooling. Sunday will remain dry and cool.

A reinforcing cold front will pass through Sunday night into
Monday and high pressure will build overhead later Monday and
Tuesday...bringing more dry and chilly conditions.


Fog potential this morning appears much lower than previous light southerly flow remains at the terminals and
dewpoint depressions through the boundary layer are larger than
previous nights. Thus, expect VFR conditions to remain at all
terminals. VFR will continue through the day today. A stalled
frontal boundary will be across the region Wednesday night into
Thursday...leading to the possibility of lower ceilings, however
flight restrictions are currently not anticipated. Showers
increase in coverage Thursday night and sub-VFR conditions are
possible into Friday. Gusty NW winds are also possible behind the
front through Friday night.

Gusty northwest winds are expected Saturday. VFR conditions will
persist for Saturday and Sunday.


Southerly winds continue on the waters this morning. A few gusts
AOA SCA were noted early this morning as stronger winds aloft
were able to mix down due to warmer waters. Thus, issued an SCA to
account for this. Winds should diminish near sunrise. Winds then
remain below SCA through Thursday afternoon. Winds increase a bit
out of the south Thursday night ahead of an approaching frontal
system and winds may approach SCA conditions.

Cold front moving through the region Friday will very likely bring
SCA conditions with gales possible later Friday into early

Gusty northwest winds are expected behind a cold front for
Saturday through Saturday night. A Small Craft Advisory will be
needed and a Gale warning may be needed for portions of the

Winds may shift to the west and southwest for Sunday. A small
craft advisory will likely be needed for portions of the waters
during this time. A reinforcing cold front will pass through
Sunday night into Monday. More SCA conditions are possible during
this time.


South to southwest flow will continue over the waters through
tonight...with southerly winds Thursday into Friday ahead of a
cold front. Elevated water levels are expected at the sensitive
sites during this time.

DC/Alexandria appears the most vulnerable for minor coastal flooding
through tomorrow nights high tide cycle...with the current forecast
near minor stage tomorrow night. Otherwise...minor tidal flooding
concerns return Thursday night at other sensitive sites (e.g.,

A potent offshore flow will develop behind a cold front later
Friday through the weekend. Blowout tides are possible during this


A record daily high temperature of 84 degrees was set at
Baltimore-Washington International Thurgood Marshall Airport (BWI)
near Baltimore MD Tuesday. This breaks the old record of 82 set
in 1945...1928 and 1908.

Climate records have been kept at BWI since 1950. Additional
temperature records for the Baltimore MD area extend back to
July of 1872.

Two record daily high temperatures were set at Washington Dulles
International Airport (IAD) so far this week. A high temperature of
84 degrees Monday broke the old record of 83 set in 1963. A high of
85 degrees on Tuesday broke the old record of 82 set in 2007 and

Climate records have been kept at IAD since November of 1962.

Below is a list of record daily warm temperatures for October
19th and 20th.

Record daily high temperatures
Site    10/19       10/20
DCA    88 (1938)   86 (1969)
BWI    82 (1947)*  87 (1969)
IAD    83 (1991)*  83 (1969)
*also occurred in previous years

Record daily warm low temperatures
Site   10/19       10/20
DCA   65 (1905)   64 (1885)*
BWI   67 (1905)   65 (1910)
IAD   60 (2011)   59 (1993)
*also occurred in previous years


MARINE...Small Craft Advisory until 7 AM EDT this morning for ANZ533-


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