Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service Baltimore Maryland/Washington District of Columbia
1033 am EDT Thursday Jul 24 2014

a cold front will slowly pass through central and southern Virginia
today. High pressure will build overhead tonight through Friday
before moving off the coast during the weekend. A cold front will
pass through the area early next week.


Near term /through tonight/...
an upper level trough axis will continue to approach the middle
Atlantic this morning. A surface cold front has moved into southern Virginia
where heavy showers and strong convection are taking place. Light
nearly winds behind the front have led to a slow drying process at the
surface. Dewpoints range from the low 60s near the Mason Dixon line to the
70s near cho.

Ahead of the trough axis and in the west-SW flow aloft...a
disturbance will move off the East Coast this morning and
subsidence behind this feature has led to clouds breaking across
WV/SW Virginia. This will increase instability in this area since dewpoints
are still high. Per the 12z iad radiosonde observation and rnk radiosonde observation...instability is
present and increases to the south with higher dewpoints. A few
showers west isolated thunderstorms are expected in the central
foothills and Shenandoah Valley through the afternoon. Further north...nearly
winds will slowly advect dry cooler air into the region and rain
chances will taper from north to south today ahead of the trough

Previous discussion...
temperatures will still make it into the l-m80s across the area for daytime
highs...but dewpoints will hover in the m50s or lower this afternoon
which is a noticeably less humid feel to the air than the past
couple of days. The near-10 degree drop in dewpoints will reflect in
the overnight lows as well on Thursday night/Friday morning. Temperatures across the
northern half will drop to the l60s and some u50s...while the I-95
corridor and areas south/east will see lows in the l-m60s.


Short term /Friday through Friday night/...
a weak upper-level trough will remain overhead Friday.
However...surface high pressure will also be overhead so dry
conditions are expected along with sunshine. A scattered/broken cumulus deck
will develop during the afternoon. Maximum temperatures will range from the
upper 60s and lower 70s in the mountains to the lower and middle
80s across most other locations. Dewpoints in the 50s and 60s will
also make it feel noticeably less humid compared to recent days.

High pressure will remain overhead Friday night...bringing dry and
comfortable conditions.


Long term /Saturday through Wednesday/...
high pressure will move off the coast Saturday and a return
southerly flow will usher in warmer and a bit more humid
conditions. The increased heat and humidity may lead to a couple
showers and thunderstorms...but coverage should remain isolated to
widely scattered due to the lack of a strong lifting mechanism.

A potent cold front will move through the Great Lakes Sunday and
this will carve out a trough of low pressure both at the upper-
levels and lower-levels of the atmosphere across our area. A
southerly flow around high pressure off the Atlantic will continue
to usher in warm and humid conditions. The increased forcing along
with the heat and humidity will lead to a better chance for
showers and thunderstorms.

The cold front will pass through the area Monday...bringing the
chance for more showers and thunderstorms. Noticeably cooler and
drier conditions are expected behind the front for the middle
portion of next week.


Aviation /15z Thursday through Monday/...
a cold front sagging south across the area will slowly usher-in a
stiff northwest-northerly breeze later this morning. MVFR/VFR conditions expected
this morning as ceilings continue to lift. This will affect areas
along the I-95 corridor and east west/ a general north wind near 10kt.
Precipitation will decrease throughout the day and into tonight west/
clearing skies and light winds toward Friday morning.

High pressure will bring VFR conditions for Friday through Friday
evening. Patchy fog is expected late Friday night into Saturday
morning. A southerly flow will develop for Saturday and Sunday as
high pressure moves off the coast. The increased moisture from
the southerly flow will bring the chance for showers and
thunderstorms. Thunderstorms will be more widespread in coverage
Sunday. A cold front front will pass through the terminals
Monday...bringing the chance for more showers and thunderstorms.


showers are expected from Annapolis and District of Columbia south this morning and
early afternoon as a cold front south of the waters moves further
south. Nearly winds will increase to 10-15kt by this afternoon as
wind channels down the Bay. A brief respite and then some more
northerly channeling overnight...but expected to be near but below Small Craft Advisory
range. A Small Craft Advisory advisory is in effect for the Maryland Chesapeake Bay south
of Pooles Island and lower tidal Potomac late tonight through
Friday morning.

High pressure will build over the waters Friday into Friday night.
The high will move off the coast Saturday and Sunday...allowing
for a southerly flow to develop. Southerly winds may gust past
Small Craft Advisory criteria for portions of the waters Saturday afternoon through
Sunday morning. A potent cold front will pass through the waters
early next week.

Showers and thunderstorms are possible Saturday through Monday. As
of now it appears that the most widespread coverage in
thunderstorms will be Sunday into Sunday night...but certainty
remains low this far out.


Lwx watches/warnings/advisories...
District of Columbia...none.
Marine...Small Craft Advisory from 2 am to 8 am EDT Friday for


near term...has/gms
short term...bjl
long term...bjl

National Weather Service Glossary of Abbreviations