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Area forecast discussion 
National Weather Service Baltimore Maryland/Washington District of Columbia
926 PM EDT sun Jul 24 2016

Synopsis...
a warm front will lift north of the area tonight. A cold front
will approach from the northwest late Monday. This front may
stall across the region during the middle of next week.

&&

Near term /until 6 am Monday morning/...
showers/thunderstorms have developed this evening ahead of an
approaching remnant mesoscale convective system/shortwave from earlier today. The bulk of
the activity so far has been west of the District of Columbia Metro back into
western Maryland/Virginia and eastern WV. Much of the current activity at 9pm,
some strong to locally severe, is across northern VA, along the
unstable side of a tight cape gradient. Across northern Virginia there
exists between 1000-3000 j/kg of MLCAPE, while only 500-1000 j/kg
is analyzed closer to the Chesapeake Bay. Bulk shear values are
low, about 25 knots or less, but given the high amount of
instability in WV/VA, some pulse severe storms remain possible.
Showers/thunderstorms will push eastward into District of Columbia/Maryland over the
next several hours, however given much less instability, severe
threat will diminish. Coverage will wane overnight, but until
shortwave clears the region, 06-09z, chances remain for
showers/storms.

Otherwise warm and muggy conditions are expected as dew points
rise on return flow. Lows generally in the 70s. Some patchy fog
also possible, especially in areas that see rain.

&&

Short term /6 am Monday morning through Tuesday night/...
the primary issue for Monday will be the heat, and have issued a
heat advisory for areas east of the Blue Ridge in addition to the
Winchester-Hagerstown corridor. West-southwest flow will advect warm and
moist air into the area, and any lingering mid clouds should clear
by midday. Widespread mid to upper 90s are expected with possibly
a few 100s. Model consensus for dew points is the low 70s, but
there is some spread. If everything came together just right, heat
indices could near 110 east of I-95, but it's likely the
temperatures and dew points will balance themselves via mixing to
fall short of that mark.

Thunderstorms will provide little relief for most of the day east
of the mountains, as any forcing remains well to the NW, so most
of the storms will be terrain-based. Some of these may gradually
propagate to the southeast by evening as a cold front approaches from
the northwest. The better shear will be north of the region, but with
moderately high cape expected, there could be some stronger
storms, especially to the northwest. Still have pops in the chance range
as the front gets strung out parallel to the upper flow. However,
have lingered storm chances well into the night as the boundary
sinks southward.

The front will remain stalled across the area on Tuesday. The
highest chances of storms will be south of the front, which at
this time looks to be south of I-66. Due to weak flow, the storms
could be heavy rain producers. Temperatures will back off
slightly, but the heat index will still approach 100 across much
of the area. Perturbations interacting with the front will keep a
threat of storms across southern areas into Tuesday night.

&&

Long term /Wednesday through Sunday/...
quasi-stationary front remains near the area Wednesday into next
weekend, with temperatures remaining above normal, and at least
isolated shower/storm chances possible nearly each day.

Some guidance is hinting that ridging will retreat to the south just
enough Wednesday and Thursday for 850 mb temps (and thus sfc temps) to
fall a few degrees from the early week highs in the M/u90s.
Though...temps in l/m90s are still above normal. The gradual
"cooling" trend continues Friday into next weekend, with afternoon
highs generally in the u80s/l90s as broad troughing develops and
heights lower further. Shortwave moving through the flow could
concentrate thunderstorm coverage late in the week...though
spatiotemporal placement is uncertain at this forecast range.

&&

Aviation /01z Monday through Friday/...
primarily VFR conditions should prevail through the night.
However, scattered showers and thunderstorms have developed and
will push eastward across the region. Have introduced mention of
thunderstorms in the vicinity at all taf sites except cho which should remain south of the
convective activity. May also see some brief reductions in
visibility with any heavier showers/storms.

Some patchy fog also possible, especially if rain occurs.

VFR through most of Monday with storm chances increasing (but
still scattered) during the late afternoon through evening. Some
storms may persist into the night as the front drifts south. This
front will stall on Tuesday, with the highest chance of storms
near cho.

Frontal boundary remains near the area through the end of the week,
with at least afternoon thunderstorms possible.

&&

Marine...
southerly winds up to about 15 knots this evening will turn
southwest on Monday. At this time, winds expected to remain less
than 15 kt, although flow may increase some Monday evening. A
bigger hazard will be thunderstorms, although the best chance may
await until Monday evening, and renew on Tuesday, especially for
southern waters.

A frontal boundary remains near the waters through the end of the
week, with gusty winds possible in any thunderstorms.

&&

Climate...
here are the record highs and warm lows for the next three days.
Monday's numbers appear to be the most vulnerable.

Sunday...
dca...101 in 2010...84 in 2011
BWI...101 in 2010...82 in 2010
iad... 99 in 2010...78 in 2010

Monday...
dca...100 in 1930...79 in 1965
BWI...100 in 2010...77 in 1887
iad... 98 in 2010...76 in 1965

Tuesday...
dca...103 in 1930...79 in 1987
BWI...101 in 1940...80 in 1940
iad....98 in 2012...76 in 2005

&&

Lwx watches/warnings/advisories...
District of Columbia...heat advisory from noon to 8 PM EDT Monday for dcz001.
Maryland...heat advisory from noon to 8 PM EDT Monday for mdz003>006-011-
013-014-016>018-503>508.
Virginia...heat advisory from noon to 8 PM EDT Monday for vaz028-030-031-
036>040-050>057-501-502-505-506.
WV...heat advisory from noon to 8 PM EDT Monday for wvz052-053.
Marine...none.

&&

$$
Synopsis...ads
near term...ads/mm
short term...ads
long term...mse
aviation...ads/mm/mse
marine...ads/mm/mse
climate...weather forecast office lwx

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