Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Baltimore Maryland/Washington District of Columbia
248 PM EDT Sat Aug 29 2015
High pressure remains over the region through Sunday and then slides
offshore for the week ahead.
Near term /tonight/...
High pressure remains over the area. Prnstly cumulus forming over the mountains...low
chances that any of these will form into a shwr/tstm. Overnight not quite
as cool as the prvs few ngts west/ lows in the 60s xcpt l70s in the
cities and along the Bay. Light fog may form in the central shen
vlly aftr mdngt.
Short term /Sunday/...
Tmrw same story different day - high pressure remains over the area. Highs
85-90. A little better chance of rain shower/thunderstorm tmrw...especially over the
mountains...but at this time of yr upper level wind field is gnrly pretty
light...as is the case Sunday. Hence severe threat is none.
Long term /Sunday night through Saturday/...
By Sunday night...trough in the northern stream in vicinity of the eastern
Great Lakes will provide the weakness for the closed low which has
been residing on the central Gulf Coast to lift NE. While diurnal
convection over the high terrain will begin to weaken during the
evening...had to continue low end probability of precipitation through the night as the
trough approaches from the southwest. Lows will be in the 60s with
lower 70s east of I-95.
There are some slight timing differences...but the trough should
lift across the area during the morning to midday hours...shearing
out as it interacts with the northern stream. At the
minimum...Monday will be a mostly cloudy interruption to our high
pressure-dominated weather pattern. Low level moisture and forcing
will be poor...but elected to leave at least slight chance probability of precipitation
across the entire area. Thunder chances will be minimal with this
feature. Also shaded high temperatures a little lower due to the
clouds...mainly in the middle 80s.
Late Summer pattern resumes Monday night into Tuesday...and if
anything...mid/upper ridging will build further over the eastern
Continental U.S.. this will mean rising temperatures...with many areas near or
above 90 for highs. Without a prominent trigger present and poor middle-
level lapse rates...any diurnal convection will be confined to the
Tuesday night-Sat: high pressure will mostly dominate conditions during
this period...with some upper level shortwaves that will move
through or near our area. 00z European model (ecmwf) keeps our County Warning Area drier than the
12z GFS...with both models bringing precipitation over or near our County Warning Area
next Sat. Kept a chance of showers and thunderstorms during the late
afternoon/Erly evening each day but majority of time will be dry. Temperatures will
be five to ten degrees above normal for Erly sept.
Aviation /18z Saturday through Thursday/...
VFR conds expeceted tonight and sun. Light fog is possible at cho/mrb.
Upper disturbance passes over Sunday night-Monday...but VFR
conditions should prevail and any isolated shower should be light.
Tuesday morning will probably represent the better opportunity for
morning br at mrb/cho as skies clear. Any diurnal storms Tuesday
afternoon likely stay west of terminals.
Winds are expeceted to remain below Small Craft Advisory values majority of next 24 hours.
There may be a period this evening when srly channeling will push winds into
the upper teens. If so a 3 hour mws or Small Craft Advisory may need to be issued for
portions of the Bay.
Trough of low pressure to the north will tighten the pressure
gradient Sunday evening...and when combined with southerly
channeling there could be a brief window for Small Craft Advisory conditions. However
have limited forecast to 15 knots for now due to low confidence.
Westerly flow 5-10 knots Monday will become lighter and more variable
Monday night and Tuesday as high pressure is reestablished.
District of Columbia...none.