Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Baltimore Maryland/Washington District of Columbia
300 PM EDT Friday Jul 11 2014
high pressure centered over New York state will shift offshore
tonight and set up a return flow into next week. A cold front will
cross the area early next week. An upper level low will then persist
over the eastern states into late next week.
Near term /through Saturday/...
as of 18z...1025 mb surface high centered over Ithaca New York with light northerly
or Ely flow over the area. More stable marine area as well as an
earlier layer of low over the Shenandoah Valley has limited
temperatures and instability today. That said...a robust cumulus field
has broken out...though no organized development is apparent in
visible satellite imagery. With 1000 j/kg estimated from a modified
12z kiad radiosonde observation and very low shear...any thunderstorm activity looks
to be isolated late this afternoon with anything that develops
persisting into the evening.
Tonight...return flow as high pressure moves offshore. The
increasing moisture will counter the clear skies a little...but
still allow min temperatures in the middle 60s inland...low 70s urban/near
shore. Any ongoing thunderstorms should end around midnight with no
real low level jet to provide moisture and energy. Fog likely develops again
late tonight in prone valleys and plains.
Short term /Saturday night through Sunday night/...
this weekend...warming trend with chances for afternoon convection
(mainly Blue Ridge and west). Otherwise...typical summertime weather
with maximum temperatures in the upper 80s Saturday...low 90s Sunday. Min temperatures
increase a few degrees each night.
Long term /Monday through Friday/...
Monday afternoon and Tuesday look to be quite unsettled. An
anomalously strong upper level trough...for this time of
year...will work its way across the Great Lakes region through the
beginning of next workweek. Currently looking like we will have
all of the ingredients in place for severe weather Tuesday. The
middle-Atlantic will be located under the right entrance region of an
upper level jet maximum Monday night and Tuesday...which will lead to
enhanced destabilization. A cold front will be approaching from
the west...which will serve as a strong forcing mechanism for
organized convection...though convective initiation via other
means...such as terrain circulations...remnant outflow
boundaries...and sea breezes...is possible as well. 0-6 km shear
values near 50 kts should ensure convection remains organized as
well. The combination of these ingredients has led Storm Prediction Center has put
much of our area in the day 4 severe weather outlook.
Probability of precipitation will be confined to the eastern portion of the area Wednesday
as high pressure will begin ridging into the area. This high will
remain centered over the Great Lakes through the middle of the
workweek. This will bring a seasonably cool Continental air mass
over the area Wednesday and Thursday...with highs near 80 and dry
conditions across the area.
Bermuda high pressure will regain control as the high over the Great
Lakes weakens toward the end of the workweek. This will begin to
usher slightly warmer and more humid air into the region...and
return the chance of thunderstorms Friday afternoon.
Aviation /19z Friday through Wednesday/...
VFR conds through this evening aside from isolated thunderstorms and rain. Fog likely
develops again tonight in prone areas...IFR possible at kmrb and
kcho (probably just ground fog at kiad).
VFR prevails this weekend with chances for afternoon thunderstorms
west of the Blue Ridge.
variable 5-10kt flow with a Bay breeze into this evening. 10 knots
return flow begins tonight as high pressure over the Upper
Middle-Atlantic shifts offshore tonight. Southerly flow channels late
Saturday afternoon/through Saturday night with gusts in the 20 knots
range. Small Craft Advisory up from 4pm Saturday to 6am Sunday...and may need to be
extended into Sunday.
District of Columbia...none.
Marine...Small Craft Advisory from 6 PM Saturday to 6 am EDT Sunday for
Small Craft Advisory from 4 PM Saturday to 6 am EDT Sunday for