Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service Baltimore Maryland/Washington District of Columbia
942 am EDT Sat Jul 26 2014

Synopsis...
high pressure is moving offshore. Low pressure is expected to
track across Pennsylvania Sunday night with an associated cold
front moving into the middle Atlantic. A reinforcing front will cross the
region Monday. High pressure will build in behind the front bringing
cooler and drier conditions during midweek.

&&

Near term /through tonight/...
a shortwave trough will continue to move across the middle Atlantic
this morning. Scattered showers will exit the Chesapeake Bay region this
morning while a scattered sprinkles diminish across Nova.

Return flow will continue across the region and temperatures will reach
the middle to upper 80s by this afternoon. As westerly flow increases
aloft...a surface trough will form across the region which will cause
an area of weak convergence near the I-95 corridor by this
afternoon. Instability will increase behind the exiting shortwave
trough today and isolated-scattered showers and thunderstorms will be possible
across The Wash/balt region...northern Piedmont and southern Maryland. Activity
is expected to be non- severe as forcing...shear and instability will be
weak.

Note...Sunday is a critical weather day with severe weather expected for
the mid-Atlantic.



&&

Short term / Sunday through 6 am Sunday/...
a potent shortwave in the westerly flow aloft will approach the area
tonight. Most of the forcing should remain to the west...but the
surface trough will strengthen overhead and even retrograde
westward. Therefore...a few showers and thunderstorms are possible
tonight...but coverage across most areas should be isolated or
widely scattered since most of the forcing will remain to our west
over the Ohio Valley. Min temperatures will range from the 60s in the
mountains to the middle 70s in downtown Washington and Baltimore...
and it will feel noticeably more humid.

&&

Long term /Sunday through Friday/...
the primary action during the extend period looks to be coming at the
beginning. Synoptically this Summer certainly has been out of the
norm (ie..an absence of the sub tropopause high) and it looks lake this will
hold true for the end of Jul as well.

It appears that an unusually strong area of low pressure will be
tracking across PA sun evening. This will place the middle Atlantic sun in an
unstable air mass west/ convective available potential energy over 1000. Storm Prediction Center has entire County Warning Area in a slt
risk. One thing that would make this threat stronger is if area gets
breaks in clouds during midday to allow for htg/instability. Highs seasonable...
gnrly in u80s...possibly 90 in the ciites.

Chance for rain/thunderstorms expeceted to continue Sun night ahead of a cold fnt. How much
instability will remain Post-sunset will help to determine if there will be
a continue severe threat. Lows ranging from the m60s to l70s.

Currently if looks lake the actual cold fnt won't push east of the region
until late Monday...hence more probability of precipitation/chances for cnvctn. Highs in lm80s.

Aftr that the next several days - the last part of Jul...the
Continental U.S. Should be under a western ridge/eastern trough. This will keep
temperatures in the middle Atlantic below normal. As i've written in several dscns
recently we are at the climatologically warmest time of the yr -
highs should gnrly be in the u80s/lows in the mu60s. As of now it
looks lake highs Tuesday-Friday should be in the l80s. Low temperatures outside of
warmer cities will be a60...possibly even into the u50s. It looks lake it
should be dry Tue-Fri.

&&

Aviation /13z Saturday through Wednesday/...
patchy br is possible early this morning across the western
terminals. VFR conditions will persist for the rest of today. A few
showers and thunderstorms are possible across the eastern
terminals...especially this afternoon. However...coverage will be
isolated to widely scattered.

A few more showers and thunderstorms are possible across the
terminals tonight...but again coverage will be isolated to widely
scattered since most of the forcing will be to our west over the
Ohio Valley. Patchy br may reduce visibilities late tonight.

In the extend...thunderstorms are possible sun..Sun night...and Monday. It is likely
that l.T. VFR conds will occur if storms develop over an Airport along
west/ the possiblity of strong winds.

Conds expeceted to be VFR Tuesday and Wednesday.

&&

Marine...
a southerly flow has developed around departing high pressure and
the southerly flow will continue through tonight. The pressure
gradient will strengthen a bit this afternoon and tonight...causing
southerly winds to channel up the Maryland Chesapeake Bay and lower
tidal Potomac River. A Small Craft Advisory is in effect for the
Maryland Chesapeake Bay from south of Pooles Island to Smith
Point...and the lower tidal Potomac River from Cobb Island to Smith
Point. Wind gusts may be marginal this afternoon due to the
relatively cooler waters...but will continue with the headline for
now due to the strengthening gradient. Higher confidence with Small Craft Advisory
wind gusts is for tonight.

Thunderstorms expeceted on the waters...especially sun aftn/eve. These may
generate strong gusty winds. An Small Craft Advisory is expeceted Monday as a cold fnt moves
through the waters. This may continue into Monday night. Tuesday-Thursday look more
tranquil.

&&

Tides/coastal flooding...
a light southerly flow has caused tidal anomalies to increase to
around one-half foot above normal. This will cause water levels to
approach minor flooding for sensitive areas near high tide this
morning for locations along the western shore of the Maryland
Chesapeake Bay and the shore of the upper tidal Potomac River.
However...water levels should remain just below these thresholds
since the flow will be light. The high tide cycle this afternoon and
evening will be the lower of the two...so minor flooding is not
expected.

However...the southerly flow may strengthen a bit tonight and the
high tide cycle late tonight into Sunday morning will be the higher
of the two. Minor tidal flooding is possible for sensitive areas
near high tide late tonight into Sunday morning.

&&

Lwx watches/warnings/advisories...
District of Columbia...none.
Maryland...none.
Virginia...none.
WV...none.
Marine...Small Craft Advisory from 1 PM this afternoon to 6 am EDT
Sunday for anz531>534-537-539>543.

&&

$$
Update...has
previous...bjl/Woody!

National Weather Service Glossary of Abbreviations