Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Baltimore Maryland/Washington District of Columbia
306 PM EDT sun Oct 4 2015
Synopsis...low pressure will drift east from the southeast coast
tonight then move out to sea through middle week. High pressure will
build into the region middle week. A cold front will cross the area
Near term /through Monday night/... patchy dz being noted as of
18z with observation and the latest reflectivity. Area remains sandwiched
between the high pressure to the north...and low pressure resting
off the Carolina coast. This low will slowly be pushing away from
the region by tonight...with the high pivoting to the south. This
will lead to diminishing winds during the overnight hours...though
not completely diminished with a tightened pressure gradient.
Concerning precipitation...low levels remaining saturated per 12z kiad sounding
and ceiling reports of around 1kft across the County Warning Area. Weak subsidence
around 500mb should keep the drier air aloft for most of the
day...with the next shortwave not moving into the middle Atlantic till
tonight. So while probability of precipitation will exist through the remainder of the
afternoon...not expecting much in terms of accumulate with the precipitation being even
more dz than rain most likely. Any precipitation will be mostly suppressed to
the south overnight...and as winds shift to the north...any upsloping
precipitation development will be minimal as well. Overnight lows will however
right near normal...per sref/adjmetbc blend.
12z Monday morning will see a synoptic setup with the low off the
Carolina coast and the surface high pressure slowly sinking south.
Aloft...the closed low still lingers to the south with multiple
weak impulses rounding the low into the mid-Atlantic. While the
moist levels will be dropping off and as such no precipitation is expected...can
still expect mostly cloudy conditions for the first half of the
day. Westerly winds look to take over aloft late in the day Monday...or
possibly even not till Monday night...which will finally work to
scatter the skies out.
High temperatures will reach the 60s...while lows tomorrow night could drop
into the 40s for most of the area as winds become light and skies
scatter. Depending on the cloud coverage though...could see temperatures a
few degrees warmer...but still around normal.
Short term /Tuesday through Wednesday/...fair weather conditions will
dominate the region during this period with high pressure building Tuesday
night through Wednesday night. Scattered-broken stratocu expected Tuesday with
clearing expected Tuesday night. A few clouds will begin reaching the
northwest part of the forecast area late Wednesday. Temperatures back to seasonal norms in
the middle 70s and lows around 50.
Long term /Wednesday night through Sunday/... high press continues to
dominate conditions Wednesday night through Thursday. A cold front will move
across our region Friday into Sat bringing a chance of showers for
our County Warning Area. High press build behind the front. Temperatures will be near
Aviation /18z Sunday through Friday/... generally MVFR ceilings through tonight
with only kcho holding onto the IFR ceilings. Expecting the lower
ceilings at kcho through the night. The other sites could see a brief
period of VFR ceilings overnight...but returning to MVFR near
daybreak. Guidance suggesting even IFR ceilings but confidence is too
low at this time to include in taf. Visible could also drop at
kmrb/kiad/kcho...but need to see the trend this evening before
dropping visible at kiad/kmrb.
Winds northerly 10-15kts with occasional gusts 20-25 kts this afternoon...dropping
blw 10 kts tonight and becoming more northerly. VFR conditions return on
Monday...between 14-19z. VFR conditions then lasting through Monday
VFR conditions Tuesday and Wednesday with no sig weather.
VFR conditions expected during this period with high press
dominating the weather conditions.
Marine...mainly Small Craft Advisory conditions on all the waters this afternoon with
occasional gales on the middle Chesapeake Bay and lower tidal Potomac. Will
go ahead and drop the gales everywhere but where occasional gales are
begin noted...and issue a Small Craft Advisory. The Gale Warning remains in place
through tonight...but will most likely be dropped by 03z this
evening. A Small Craft Advisory will then be needed the remainder of the night and
lasting into Monday night.
Small craft conditions could still linger through Tuesday but should
subside quickly Tuesday evening.
Sub-Small Craft Advisory conditions expected during this period with high press
dominating the weather conditions.
Tides/coastal flooding... coastal flood warnings in effect District of Columbia and St
Marys County to account for moderate flood levels forecasted to be
reached through the high tide cycles this tonight. District of Columbia may fall just
short with the better chance coming again during the cycle Monday.
Coastal flood advisories for Baltimore/Anne Arundel/Calvert/Arlington
for minor flood levels being reach through Monday.
Tidal anomalies currently between 1.5 and 2.5 feet across the waters.
With the winds decreasing tonight...anomalies taper off
slightly...though still remaining between 1.0-2.0 feet. Used a the
etss guidance as it has been capturing The Levels better today than
District of Columbia...coastal Flood Warning until 5 am EDT Monday for dcz001.
Maryland...coastal Flood Advisory until 2 am EDT Monday for mdz014.
Coastal Flood Advisory until 3 PM EDT this afternoon for
Coastal Flood Warning until noon EDT Monday for mdz017.
Coastal Flood Advisory until midnight EDT tonight for mdz018.
Coastal Flood Advisory until 4 am EDT Monday for mdz011.
Virginia...coastal Flood Advisory until 3 PM EDT this afternoon for
Coastal Flood Advisory until 5 am EDT Monday for vaz054.
Marine...Small Craft Advisory from 6 PM this evening to 6 PM EDT Monday
Gale Warning until 6 PM EDT this evening for anz531>533-
Small Craft Advisory from 6 am to 6 PM EDT Monday for anz534-
Gale Warning until 6 am EDT Monday for anz534-537-543.
Small Craft Advisory until 6 PM EDT Monday for anz530-536-538.
Small Craft Advisory until 6 am EDT Monday for anz535.