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Area forecast discussion 
National Weather Service Baltimore Maryland/Washington District of Columbia
432 PM EDT Mon Jul 25 2016

Synopsis...
a cold front will drift into the region from the north tonight.
This front will stall across the region during the middle of the
week. Another cold front is expected at the end of the week.

&&

Near term /until 6 am Tuesday morning/...
a Severe Thunderstorm Watch has been issued for the northern 3/4
of the area through 10 PM.

A cold front extends from western New York to the Ohio Valley this
afternoon. Another confluence zone extends into the Appalachians.
The hot and humid airmass across the mid-Atlantic is supporting
MLCAPE in excess of 2000 j/kg. Isolated storms are developing over
the mountains, but more organized convection is developing in the
better lift to the north. Hi-res guidance indicates the northern
part of the area has the highest risk to see some of these
organized storms during the early evening hours, particularly the
Baltimore area. It's possible the activity could be weakening
though as it travels parallel to the low level shear vector. Locally
damaging wind gusts will be the biggest threat. However,
relatively slow storm motion and precipitable water near 2 inches will support
locally heavy rain. Flash flood guidance is over 2 inches/hour in
much of the area though.

Most of the evening storms should either dissipate or exit the are
by midnight. However, as the boundary sinks southward, can't rule
out some rogue showers/storms lingering. Low temperatures will be
in the 70s for most locations.

&&

Short term /6 am Tuesday morning through Wednesday night/...
the front will become stalled across Virginia, likely toward the
southern half of the area, for Tuesday and Wednesday as it becomes
parallel to the upper level flow. Thunderstorm chances will
largely be diurnally based each day, but with the front in the
area and potential for subtle shortwave troughs to be moving
across the area, it will be tough to pinpoint any dry periods. For
Tuesday afternoon, bulk shear will again be in the 25-30 kt range
in the midst of strong destabilization over the southern portions
of the forecast area, so a marginal risk of severe weather has
been introduced. Wednesday afternoon and evening will need to be
monitored as well as the pattern changes very little. High precipitable water
will mean heavy rain is also a threat.

Temperatures will lower a little for the next two days, generally
in the low to mid 90s. However, heat indices will approach 100 yet
again, especially Tuesday, with the highest values over the far
southern areas. Due to values near 105...have issued a heat
advisory again for Tuesday for Nelson, Albemarle, Orange, and
Spotsylvania counties. Overnights will remain in the 70s.

&&

Long term /Thursday through Monday/...
main story Thursday through the weekend will be persistent above
normal temperatures (though not too extreme) and the potential for
showers and thunderstorms (some of which could be heavy at times).

Front will linger near the area Thursday, which will keep chances
for at least isolated afternoon thunderstorms in the forecast. Mid
90s temperatures coupled with upper 60s dewpoints yields heat index
values in the upper 90s Thursday.

Heights begin to fall late Thursday as shortwave approaches. While
timing differences exist among long term guidance, the best chance
for precipitation will occur as this feature crosses the area late
Thursday into Friday. Depending on the track, there could be some
heavy rain across parts of the area.

While uncertainty exists with next weekends forecast, general
consensus is for above normal temperatures to continue, with at
least isolated afternoon thunderstorm chances.

&&

Aviation /21z Monday through Saturday/...
thunderstorms will be the main concern through the evening,
particularly the 4-9 PM time frame. Heavy rain and strong wind
gusts will be possible. With somewhat scattered coverage, have
left as thunderstorms in the vicinity for now. Baltimore area may have a slightly better
chance at seeing some organized storms. In the humid airmass,
can't rule out some fog, particularly where storms cross.

Nearby frontal boundary will allow for isolated afternoon
thunderstorms Thursday. Better chance for scattered
showers/thunderstorms arrives late Thursday into Friday as upper
level energy approaches.

&&

Marine...
update to issue Small Craft Advisory for portions of the central Chesapeake
and lower tidal Potomac. Expecting to winds to gust to near 20
knots this evening and into the overnight hours. Elsewhere, overall
winds expected to be 10-15kts from the west or SW today and tonight.
Showers and thunderstorms will become increasingly possible by
late afternoon/ early evening. Some storms may be strong to severe
resulting in gusty winds. Smws will be likely. A cold front will
move through the waters Tuesday morning and winds will become west to
northwest behind it. Showers and thunderstorms are possible Tuesday
afternoon mainly across the southern waters and again on Wednesday
as the front stalls out.

While gradient winds remain below Small Craft Advisory criteria through the end of
the week, thunderstorms will be possible Thursday and Friday. The
best chance for showers/storms is late Thursday into Friday as upper
level energy approaches.

&&

Climate...
the last time we hit 100 degrees:
dca: July 26th 2012 (100)
bwi: July 18th 2012 (104)
dmh: July 19th 2013 (100)
iad: July 18th 2012 (101)
cho: July 8th 2012 (106)
hgr: July 7th 2012 (101)
mrb: July 7th 2012 (100)

Record maximum temperatures for July 25th:
dca (dc area): 100 (1930)
dca only: 99 (2010, 1987)
BWI (baltimore area): 100 (2010)
BWI only: 100 (2010)
dmh: 100 (2010)
iad (dulles area): 98 (2010)
iad only: 98 (2010)
cho: 101 (2010)
hgr: 98 (2010)
mrb: 101 (1933)

Dca (dc area): 79 (1965)
dca only: 79 (1965)
BWI (baltimore area): 77 (1887, 1885)
BWI only: 76 (2001, 1965)
dmh: 78 (2011)
iad (dulles area): 76 (1965)
iad only: 76 (1965)
cho: 74 (2010)
hgr: 75 (2001)
mrb: 73 (2010, 2001, 1989, 1979, 1965)

"area" denotes threadex sites which are the numbers used for rers.

&&

Lwx watches/warnings/advisories...
District of Columbia...heat advisory until 8 PM EDT this evening for dcz001.
Maryland...heat advisory until 8 PM EDT this evening for mdz003>006-011-
013-014-016>018-503>508.
Virginia...heat advisory until 8 PM EDT this evening for vaz028-030-031-
036>040-050>057-501-502-505-506.
Heat advisory from noon to 8 PM EDT Tuesday for vaz036-037-050-
056.
WV...heat advisory until 8 PM EDT this evening for wvz052-053.
Marine...Small Craft Advisory until 4 am EDT Tuesday for anz534-537-543.

&&

$$
Synopsis...ads
near term...ads
short term...ads
long term...mse
aviation...ads/mse
marine...ads/mse/mjm
climate...dfh

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