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Area forecast discussion 
National Weather Service Baltimore Maryland/Washington District of Columbia
359 am EDT sun Jul 31 2016

Synopsis...
an area of weak low pressure will track eastward across the area
today. A cold front will move southward on Monday as the low moves
offshore. High pressure will build in from the north during the
middle of the week.

&&

Near term /through tonight/...
please see the latest flood statements for the latest information on
floodwaters working downstream due to the very heavy rain last
evening between District of Columbia and Baltimore.

The other concern first thing this morning is fog in a humid and
stagnant airmass. The County Warning Area is divided, with more fog to the SW and
more low clouds to the NE. Several sporadic obs have hit 1/4sm, so
will need to continue to monitor for a short fuse dense fog advisory.

The pressure pattern is weak across the area, with lower pressure
extending from the mid-Atlantic to the Ohio Valley. Broad upper
troughing is located over the Ohio Valley. Both of these features
will push eastward today. Other than an isolated shower, most of the
morning hours should be dry. Convection should initially fire along
the terrain and then push east during the mid to late afternoon.
There seems to be consensus that the best coverage of storms will be
to the south of the track of the weak low, and with a ridge of
higher Theta-E air. This is generally SW of the District of Columbia Metro, although
storms could push northward toward the Chesapeake Bay during the
evening as the Theta-E ridge expands slightly.

In terms of parameters, today appears to have less potential to be
hazardous. Deep layer shear and precipitable water are both lower than Saturday.
Ncar ensemble Max quantitative precipitation forecast is also lower than yesterday and focused in
the above-mentioned area across the southern County Warning Area.

With potential for sun for part of the day, highs will again push
toward 90. Even though there should be a diurnal downturn to precip,
with the baggy low near the area, some showers may linger into the
night, especially to the east. Lows generally in the mid 60s to
lower 70s.

&&

Short term /Monday through Tuesday night/...
the broad, weak surface low doesn't make a whole lot of progress
eastward on Monday, although northwest flow on the back side will begin to
advect some slightly drier air into the area. However, the mid-level
trough axis will be approaching with an embedded vort Max.
Therefore, some scattered showers and storms could develop during
the afternoon and evening. Shear and instability should be low
enough that severe weather isn't a concern. This activity will
diminish during Monday evening.

On Tuesday, the drying trend should be more pronounced as the low
moves farther offshore and northwest flow becomes established. However, mid-
level trough will be sharpening over New England, and this could
provide enough energy for a shower or storm near the Chesapeake Bay.
Cooler air will continue to move into the area Tuesday night.

&&

Long term /Wednesday through Saturday/...
troughing departs on Wednesday and heights begin to rise. Some
guidance is continuing to hint at the potential for some
energy/convection to move into the area on northwest flow around the
periphery of another building central US ridge. However will
continue to downplay for now given difficulty of pinpointing these
convective systems days in advance, and tendency of them to curl
southward into greater instability. Will run with a mainly dry
forecast, however an isolated shower/storm possible in the higher
terrain as high pressure begins to move offshore and light return
flow develops. Highs in the 80s and dew points in the 60s.

Ridging continues to build in from the southwest Thursday and
Friday, and with that will come warmer temperatures and a return in
moisture. Could be some isolated to scattered convection on either
day, especially higher terrain. Highs nudge back up towards or above
90f.

The next cold front will approach and cross the area next weekend.
Thus Saturday looking warm/humid with increased chances for
showers/thunderstorms.

&&

Aviation /08z Sunday through Thursday/...
IFR or lower conditions will remain possible through sunrise -- in
low clouds around District of Columbia/Baltimore, and in fog at mrb/cho.

Much of today should feature VFR conditions with light SW winds.
Scattered showers and storms will be possible again today, but less
widespread and less intense than Saturday. Cho will have the highest
chance. Best time frame will be mid afternoon to evening. Low
confidence in any fog tonight, so will not include a mention for now.

A few storms will be possible again on Monday as a trough axis
swings through, but coverage even less than Sunday. Light west flow
on Monday will become northerly on Tuesday as low pressure moves
offshore. Tuesday should be dry.

Predominantly VFR expected Wednesday and Thursday. Only restrictions
would come in some patchy fog at night/early morning and any
isolated-scattered showers/thunderstorms Thursday.

&&

Marine...
variable flow will become S/SW today. Generally expecting winds 10
kt or less, but could increase to 15 kt this evening. Scattered
storms will be possible from mid afternoon to the evening, so
locally higher gusts will be a concern. Flow becomes west on Monday,
then north on Tuesday. Will continue to mention potential for Small Craft Advisory
conditions during this period, although current guidance suggests it
will be very borderline. Storm threat even lower for Monday and
lower still on Tuesday.

Sub-Small Craft Advisory winds expected Wednesday. Winds may increase out of the
south Thursday and approach Small Craft Advisory criteria. A few
showers/thunderstorms possible Thursday as well.

&&

Tides/coastal flooding...
tidal anomalies have risen back to around a foot above normal, and
this is causing some minor flooding early this morning, most notably
at Annapolis. Once this morning's high tide cycle is complete, no
additional flooding is anticipated today, however tonight's/early
Monday morning's high tide cycle may produce additional minor
flooding, mainly at Annapolis.

&&

Lwx watches/warnings/advisories...
District of Columbia...none.
Maryland...coastal Flood Advisory until 8 am EDT this morning for mdz014.
Virginia...none.
WV...none.
Marine...none.

&&

$$
Synopsis...ads
near term...ads
short term...ads
long term...mm
aviation...ads/mm
marine...ads/mm
tides/coastal flooding...mm

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