Tornado Warning 24, NWS Baltimore/Washington

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
1029 AM EDT Thu May 30 2019

.SYNOPSIS...
A frontal boundary will remain across Pennsylvania today before
crossing the area as a cold front this evening and tonight.
Another frontal system may affect the region over the weekend.
Afterward, Canadian high pressure is poised to settle over the
region through the early portion of next week.

&&

.NEAR TERM /THROUGH TONIGHT/...
A surface frontal boundary continues to take us residence
across Pennsylvania this morning, much like it has the past
couple of days. Surface low pressure near Illinois will track
eastward today, nearing the Ohio Valley later this afternoon.
The aforementioned frontal boundary will sink southward as a
cold front nears to our west. This will set the stage for a
couple rounds of showers and storms, with the first occurring
early this afternoon, and the second late this afternoon and
into this evening as the frontal boundary moves through the
area.

This activity will be supported by a series of shortwave energy
moving across the region. Given the ingredients highlighted
below and the aforementioned synoptic features, the threat for
strong to severe storms exists this afternoon and evening. The
Slight Risk depicted by the Storm Prediction Center now
highlights our entire CWA, with damaging winds the primary
threat, however large hail and an isolated tornado will remain
possible. North central and northeast MD will be favored with
the best dynamics to support an isolated tornado risk given the
proximity to the surface boundary, increasing southerly/veering
winds in the lowest 3km of the boundary layer, and higher 0-1km
SRH values. No major changes made to the current forecast
package.

Previous Discussion:

Out ahead of the front, another very warm day is expected,
although temperatures will be a couple of degrees cooler than
yesterday. Forecast highs range from the mid 80s to low 90s.
This will allow for the development of 1000-1500 J/KG of SBCAPE
across the region, and that coupled with 0-6KM shear values of
40-50 knots will set the stage for another day of
strong to potentially severe thunderstorms. There is relatively
good agreement between various CAMs that initial development
seems likely to occur during the early to mid afternoon hours
across portions of northwestern VA, eastern WV, and western MD
as the initial shortwave moves into the region. This activity
should then propagate eastward during the afternoon hours. A
second round of showers and possible thunderstorms will then be
possible during the late afternoon and evening hours out ahead
of the second shortwave and cold front. Given better agreement
on convective development/coverage between models than in recent
days, approach of a cold front, and somewhat better upper level
forcing, this afternoon and evening will likely have the
highest coverage of scattered showers/thunderstorms across the
region of the past 3 days, although greatest coverage will still
likely lie north of the PA/MD border. Any thunderstorm has the
potential to become severe, with the main threats being large
hail and locally damaging winds.

As the front crosses the region late this evening, conditions
will dry out behind it overnight with lows in the 60s to around
70F.

&&

.SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
An upper level trough will move into WV and central/southern VA
during the day Friday. This will likely help to initiate
scattered showers/thunderstorms again across central VA and
eastern WV. A locally strong thunderstorm is possible with gusty
winds, small hail, and heavy rain. Otherwise, temperatures will
trend downward closer to daily normals, with highs in the low
80s. Brief ridging will build in overhead Friday night with
drying conditions. Lows in the low to mid 60s.

Another cold front will move southeastward towards the region
Saturday, and this may trigger some shower/thunderstorm
development, mainly across northern/western MD and eastern WV.
Highs in the 80s. Lows Saturday night in the 60s.

&&

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
A slow moving cold front will be approaching on Sunday allowing for
scattered showers and thunderstorms. A strong mid-level shortwave
will spin up a surface low along the front -to our north- late
Sunday into Monday as it pulls the front away from us into Monday.
This slow moving system could keep some isolated to scattered
showers Sunday night into Monday. Drier conditions arrive late on
Monday as high pressure builds over our area. Northwesterly flow
will allow for slightly below normal temperatures on Monday night.
The high will be over us on Tuesday and will move offshore on
Wednesday. Another front will approach our area on Thursday.

&&

.AVIATION /14Z THURSDAY THROUGH MONDAY/...
Predominate VFR conditions forecast the next several days, but
opportunities for daily showers/storms will deliver episodes of
sub VFR conditions at times. The first chance of said episodes
will occur this afternoon and evening as scattered showers and
storms are expected, with the potential for some thunderstorms
to deliver heavy rain, gusty winds, and hail. CHO has the
lowest probability to see thunderstorms, with MRB/BWI/MTN having
the highest. Additional scattered showers/thunderstorms may
affect CHO on Friday, and isolated showers/thunderstorms remain
possible Saturday, this time mainly MRB.

Periods of subVFR condtions are possible on Sunday into Sunday night
as front approaches and moves across our area. High pressure/VFR
conditions expected behind the front on Monday -with some gusty
winds. Dry/VFR conditions remain into Tuesday.

&&

.MARINE...
SCA conditions are forecast to return to the waters this
afternoon as winds strengthen ahead of an approaching cold
front. The potential exists for the need of Special Marine
Warnings as strong to severe storms remains possible over the
waters. The front will cross the waters this evening and
tonight, and winds may approach SCA criteria for a time tonight,
but will leave forecast just below at this time. Sub-SCA
conditions expected Friday and Saturday.

Periods of SCA may be needed for Sunday into Monday as a front moves
across our area, and then on Monday behind this front. Winds should
be on the decrease Tuesday as high pressure sits overhead.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...None.
VA...None.
WV...None.
MARINE...Small Craft Advisory from 2 PM this afternoon to 9 PM EDT this
     evening for ANZ530>543.

&&

SYNOPSIS...MM/BKF
NEAR TERM...MM/BKF
SHORT TERM...MM
LONG TERM...IMR
AVIATION...MM/IMR/BKF
MARINE...MM/IMR/BKF

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