Scientific Forecaster Discussion
fxus61 klwx 230734
Area forecast discussion
National Weather Service Baltimore Maryland/Washington District of Columbia
334 am EDT Mon Sep 23 2019
a cold front will pass through the area late today into tonight
and high pressure will build overhead for Tuesday and Wednesday.
A weak cold front will pass through the area Thursday and high
pressure will briefly return for Friday before moving off the
coast during the weekend.
Near term /through today/...
southerly flow is in place this morning with a surface ridge
across the Carolinas and offshore of the Atlantic coastline. A
cold front is tracking eastward from the Midwest and will move
into the area and cross the region this evening. Mostly sunny
skies, dry conditions, and southwesterly flow through a good
portion of the day will lead to another hot day, with highs from
the upper 80s to low 90s. The afternoon hours will see a
general increase in cloud cover from west to east as the frontal
zone approaches. Additionally, chances will increase for some
showers this afternoon near and west of the Blue Ridge, and east
of the Blue Ridge this evening. Instability will be quite
limited, generally less than 500 j/kg, so while a few
thunderstorms are possible, a severe threat is not anticipated.
Precipitation amounts will be quite light and scattered.
Short term /tonight through Wednesday night/...
once the frontal passage moves eastward this evening, the
chances for showers will diminish overnight as drier
northwesterly flow works into the region. Lows will fall back
into the 50s/60s.
High pressure will then build over the area on Tuesday and
Tuesday night with sunny/clear skies. Highs Tuesday will range
through the upper 70s to low 80s, with lows Tuesday night from
the upper 40s to mid 50s in most locations, except low 60s in
the urban centers and along the larger bodies of water. The high
will shift offshore by late Wednesday, allowing for a southerly
flow to develop. Mostly sunny and dry conditions will continue
with highs in the low 80s. Lows Wednesday night in the 50s/60s.
Long term /Thursday through Sunday/...
a weak cold front will pass through the area Thursday.
Unseasonably hot conditions are likely ahead of the frontal
passage, and there may be an isolated shower or thunderstorm.
Highs well into the 80s/lower 90s are most likely. However,
with plenty of westerly flow at the low- levels any convection
will be isolated.
High pressure will briefly build overhead for Thursday night and
Friday, allowing for relatively cooler conditions. However,
Friday afternoon will still likely be warmer than climo with Max
temps in the 80s for many locations.
The high will move offshore during the weekend while a
subtropical ridge builds overhead. The anomalously potent ridge
combined with surface high pressure offshore will most likely
result in unusually hot and humid conditions. A cold front may
make its way toward the area Sunday, but confidence for this to
occur is low since it will be running into the anomalously
potent upper-level high. Will have the forecast lean toward the
warmer guidance during this time.
Aviation /07z Monday through Friday/...
predominantly VFR is expected through Wednesday. A cold front
will cross the area this evening, and a period of scattered
showers and isolated thunderstorms is possible across the taf
sites in the afternoon/evening hours. However, any reductions
will be brief and isolated in nature. Only other aviation
weather related concern will be the potential for fog
development Tuesday night in the favored locations, possibly
VFR conditions are expected most of the time for Thursday and
Small Craft Advisory is in effect this morning for portions of the lower tidal
Potomac and central Chesapeake Bay with gusts near 20 knots. For
a period this afternoon and into this evening, gusts to near
20 knots may become more widespread, and a Small Craft Advisory is in effect for
all waters. A relative lull is then expected for the first half
of tonight as a cold front crosses the waters. Behind this
frontal passage, winds will increase out of the northwest and a
Small Craft Advisory returns to all waters late tonight into Tuesday. Sub-Small Craft Advisory
conditions are then likely Tuesday night and Wednesday as high
pressure moves overhead.
A weak cold front will pass through the waters Thursday and high
pressure will return for Thursday night into Friday. Winds may
reach Small Craft Advisory criteria for portions of the waters Thursday into
a southerly flow will cause elevated water levels today into
tonight, but the flow will be west of south so water levels are
most likely to remain below minor flooding thresholds.
District of Columbia...coastal flood advisory until 5 am EDT early this morning for
Marine...Small Craft Advisory from 1 PM this afternoon to 6 PM EDT this
evening for anz530-531-535-536-538>542.
Small Craft Advisory from 4 am to 11 am EDT Tuesday for anz530-
Small Craft Advisory until 2 PM EDT Tuesday for anz534-543.
Small Craft Advisory from 2 am to 2 PM EDT Tuesday for anz532-
Small Craft Advisory until 6 PM EDT this evening for anz532-
Small Craft Advisory until 8 am EDT this morning for anz537.
Small Craft Advisory from 1 PM this afternoon to 2 PM EDT
Tuesday for anz537.