Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Baltimore Maryland/Washington District of Columbia
956 am EDT Mon Jul 25 2016
a cold front will approach from the northwest late tonight. This
front may stall across the region during the middle of the week.
Another cold front is expected at the end of the week.
Near term /through tonight/...
a cold front is located across the Great Lakes region this
morning, and a Lee trough can be discerned east of the
Appalachians. A warm and humid airmass is in place with 9 am obs
already rising quickly into the mid and upper 80s. Subsidence
behind a departing shortwave should keep the area dry for the next
Two hazards are expected today...heat and scattered strong
thunderstorms. Warm air advection in the mid-levels will allow
surface temperatures to climb into the mid-upper 90s with a few
spots around the I-95 corridor potentially hitting 100. High
moisture content will lead to heat indices solidly between
105-109 across much of the mid-Atlantic with the exception of
higher elevations and the Shenandoah Valley. A heat advisory is in
effect from noon to 8pm today. It's not out of the question a spot
could briefly hit warning criteria of 110, but the 12z sounding
supports afternoon dew points in the lower 70s.
The second hazard is for severe thunderstorms mainly along and north
of U.S. Highway 50. Midday-early afternoon storm initialization
should largely occur along the terrain and be isolated-scattered.
Some of these storms may push east by mid-late afternoon, but
coverage is uncertain. More organized storms may approach northern
areas by early evening as outflow from activity currently near
Lake Ontario initiates new storms across central PA. While any
storm has the potential to be strong due to SBCAPE >2500 j/kg, the
greatest severe threat may come with the organized storms from PA
early this evening due to antecedent poor mid-level lapse rates.
Shear will also be increasing during this time due to a shortwave
trough. The main threats will be damaging winds from pulse
downbursts or multicell clusters. Localized flooding can not be
ruled out through tonight with precipitable water near 2 inches and storm
motions around 20 kt.
Activity will likely sag southward across the southern outlook
area late this evening and overnight. It should diminish some but
thunderstorms are still likely overnight.
Short term /Tuesday through Wednesday night/...
the cold front will be near the mid-Atlantic Tuesday morning.
Light northerly winds will give some relief to the heat and
humidity however temps will still reach the low to mid 90s and
indices into the upper 90s to near 100 Tuesday afternoon. Showers
and thunderstorms are likely mainly across the southern half of the
outlook area Tuesday afternoon and evening. Coverage seems to be
isolated however confidence is low at this time due to the
stalled frontal boundary.
The front will be near the mid-Atlantic through Wednesday night.
Showers and thunderstorms can not be ruled out through this period.
Light W-NW flow aloft will keep heat and humidity down however
still be above normal for late July.
Uncertainty exists for coverage and threat level of thunderstorms
Long term /Thursday through Sunday/...
a front will meander across the area through the end of the work
week keeping the risk of T-storms Thu and Fri. With front stalled
out across the area, we could see multiple rounds of convection
with heavy rain becoming a bigger threat. It will still be hot and
humid with temperatures in the mid 90s and heat indices at or
above 100f. By the weekend, guidance shows a low pressure center
developing off of the Delaware coast and moving northeast away
from the coast with front clearing the fcst area and weak high
pressure building in bringing lower humidities but with temps
still around 90f.
Aviation /14z Monday through Friday/...
VFR conditions expected this morning. More thunderstorms are
expected this afternoon and evening and may impact the terminals.
Activity may be rather isolated until mid-late afternoon. The most
organized storms may impact the Baltimore area this evening. Some
storms may be strong with gusty winds and heavy rain. Sub- VFR
conditions expected in activity. The chance for thunderstorms
persists through Wednesday as a frontal boundary stalls across the
overall winds expected to be 10-15kts from the west or SW today and
tonight. A brief surge of SW winds ahead of a cold front is
possible across the southern Chesapeake Bay late tonight and will
need to be monitored. Showers and thunderstorms are possible this
morning as well as today and tonight as a hot and humid airmass
stays in places. Coverage will increase this evening and overnight
as thunderstorms track eastward. Some storms may be strong to
severe resulting in gusty winds. Smws will be likely through
Tuesday morning. A cold front will move through the waters Tuesday
morning and winds will become nrly behind it. Showers and
thunderstorms are possible Tuesday afternoon mainly across the
southern waters and again on Wednesday.
new record highs are possible today at dca and iad. Here are the
record highs today:
Dca...100 in 1930...79 in 1965
BWI...100 in 2010...77 in 1887
iad... 98 in 2010...76 in 1965
Here are the last dates 100 degrees was reached:
dca...July 26, 2012
BWI...July 18, 2012
iad...July 18, 2012
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-
Virginia...heat advisory until 8 PM EDT this evening for vaz028-030-031-
WV...heat advisory until 8 PM EDT this evening for wvz052-053.