Scientific Forecaster Discussion
fxus61 klwx 270009
Area forecast discussion
National Weather Service Baltimore Maryland/Washington District of Columbia
809 PM EDT Fri may 26 2017
high pressure will build overhead this evening before moving
offshore toward morning. A warm front will stall out over the
area Saturday through Sunday before a cold front moves into the
area Monday. High pressure may return during the middle portion
of next week.
Near term /until 7 am Saturday morning/...
weak ridging will move overhead for much of the night, leading
to dry weather and slackening winds. Strato-cu from earlier
today should also tend to dissipate, although mid/high clouds
will be on the increase ahead of a developing mesoscale convective system currently
located over Indiana at 8 PM. Moving along a frontal zone, remnants
of that MCS, although weakening, will move into the region
during the late night/early morning hours with increased chances
for rain showers and possibly some rumbles of thunder. No
severe threat anticipated. Highest rain chances prior to 8am
will be from the Allegheny and Potomac Highlands into eastern
West Virginia and northern Maryland. There may also be some
patchy fog in a few areas. Lows tonight generally in the 50s,
except 60s in the urban centers and along the immediate
shorelines of the Chesapeake and Potomac.
Short term /7 am Saturday morning through Sunday night/...
low pressure will pass through the area on the stalled boundary
Saturday. The boundary will separate cooler marine air to the
north vs. Warm and humid air to the south. To the north and east
of the boundary...mostly cloudy skies along with a few showers
are possible due to the low passing through. Showers and
thunderstorms are possible to the south and west of the
boundary. Some thunderstorms have the potential to be severe due
to moderate shear profiles. However...latest guidance suggest
the boundary will be a bit farther south across the Potomac
Highlands into central Virginia. This is where the best chance
for stronger storms are possible Saturday afternoon and evening.
The boundary will remain stalled over our area through Sunday
night. Most places will turn out dry Saturday night after any
evening convection dissipates. More popup showers and
thunderstorms are possible Sunday near the boundary. The best
chance for showers and thunderstorms will be in the Potomac
Highlands into the central Shenandoah Valley...where the
boundary is most likely to set up. A cold front will approach
from the west Sunday night. More showers and a few thunderstorms
are possible. Rain may be locally heavy...especially over the
Allegheny and Potomac Highlands where instability may be a bit
Long term /Monday through Friday/...
a cold front slowly moves away from our region
Monday into Monday night with some showers, and maybe a
thunderstorm, mainly in the first part of the day. Conditions
become drier into Tuesday before a weak cold front moves
through Tuesday night into early Wednesday... which could bring
some scattered showers to our area. Another boundary moves
through Wednesday night into Thursday before it stalls south of
our County Warning Area into Friday.
High temperatures will be in the 70s and 80s... some 60s at
Aviation /00z Saturday through Wednesday/...
VFR conditions are expected through tonight. A few showers and
thunderstorms are possible Saturday as low pressure passes
through. Marine and rain cooled air behind a boundary that will
stall out overhead will likely cause sub-VFR ceilings as early
as late morning Saturday at mrb, mid afternoon at BWI/mtn, and
Saturday night elsewhere. Position of boundary and progression
of morning rainfall will greatly influence likelihood/position
of reduced ceilings.
Low clouds will continue well into Sunday with the boundary
likely being off to the south and west. Showers and a few
thunderstorms are possible Sunday night as a cold front
approaches from the west.
Sub-VFR conditions expected at times on Monday with
some showers and thunderstorms over US as cold front moves
through our area. Conditions become drier/VFR Monday night and
gusty west to northwest winds will continue through this
evening. Winds will quickly diminish around sunset. A Small
Craft Advisory remains in effect through this evening. Gusts
around 20-30 knots are likely...especially across the northern
A boundary will stall near the waters Saturday through Sunday
night. Winds should remain below Small Craft Advisory criteria for most of the
time...but it will be close Sunday night as the pressure
gradient strengthens just a bit ahead of an approaching cold
Periods of showers and thunderstorms move through at
times on Monday as front moves across our region. Conditions
become drier Monday night into Wednesday. Winds will be below
the Small Craft Advisory threshold Monday into Tuesday night, increasing slightly
on Wednesday to near 16 kt.
tidal anomalies have dropped off this afternoon and evening in
the gusty westerly flow, but still likely high enough to produce
another round of minor flooding at Straits Point overnight and
into early Saturday morning. Annapolis may also approach its
The offshore flow will quickly diminish tonight and an onshore
flow will develop for Saturday through Monday. Elevated water
levels are expected and minor flooding is likely. Minor flooding
may occur during the high tide cycles Saturday, although
confidence is higher for Saturday night into Monday.
District of Columbia...none.
Maryland...coastal flood advisory from midnight tonight to 6 am EDT
Saturday for mdz017.
Marine...Small Craft Advisory until 9 PM EDT this evening for