771
ACUS01 KWNS 052001
SWODY1
SPC AC 051959

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0259 PM CDT Wed Jun 05 2024

Valid 052000Z - 061200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
OF THE UPPER MIDWEST...GREAT
LAKES...NORTHEAST...MID-ATLANTIC...PARTS OF SOUTHERN AND COASTAL
TEXAS...AND SOUTHERN MISSISSIPPI...

...SUMMARY...
Strong storms are possible across portions of the Upper Midwest,
Great Lakes, Northeast, Mid-Atlantic, parts of southern and coastal
Texas, and southern Mississippi.

...20z Update...

Minor adjustments were made to the MRGL areas across northern IN and
LA/MS where morning/afternoon thunderstorms have moved eastward.

Marginal risks continue across portions of MN/WI to the
Mid-Atlantic, TX/LA/MS, and ME/NH. A few thunderstorms with
transient rotation have been observed across Central and Eastern
Virginia. See MCD 1175 for more information.

Thunderstorm development is expected to increase in coverage across
portions of MN/WI through the rest of the afternoon. Daytime heating
has yielded MLCAPE around 500 J/kg as mid-level flow increases from
a speed max moving through the trough located across Canada into the
Great Lakes region. Deep layer shear will increase across the
region, mainly across southern MN into northern IA, which may allow
for a few more organized clusters capable of damaging winds and hail
through the afternoon. The Marginal Risk handles this threat well,
with no changes needed this afternoon.

..Thornton/Dean.. 06/05/2024

.PREV DISCUSSION... /ISSUED 1122 AM CDT Wed Jun 05 2024/

...Synopsis...
Water-vapor imagery shows a mid-level shortwave trough over the
western Great Lakes/mid MS Valley with the primary vorticity lobe
rotating northeastward through the Upper Great Lakes through the
early evening.  A blocking pattern located over the Northeast into
Quebec will weaken as a mid-level speed max moves quickly from the
western Dakotas southeastward into the southern Great Lakes by early
Thursday morning.  In the low levels, a cold front will arc
southeastward into the Great Lakes from an occluded low over
Manitoba/western Ontario.  The trailing portion of the front will
progress eastward across the southern Great Lakes/OH Valley, while
the convectively augmented effective front stalls over the northwest
Gulf Coast states.

...MN/WI to the Mid-Atlantic this afternoon/evening...
Surface heating and lingering boundary-layer moisture will
contribute to weak-moderate buoyancy in an environment with
sufficient westerly deep-layer shear/hodograph length for scattered,
low-topped cells to produce isolated severe gusts and marginally
severe hail this afternoon across MN/WI.

Farther southeast over the southern Great Lakes/OH Valley, ascent
associated with the aforementioned Great Lakes mid-level disturbance
will aid in storm development this afternoon as heating weakens
convective inhibition.  Relatively moist low levels (surface
dewpoints 65-70 deg F) will contribute to MLCAPE around 1000 J/kg.
Moderate deep-layer vertical shear (effective bulk shear 20-30 kt)
along with poor midlevel lapse rates around 6 C/km, will favor
mostly strong to locally severe multicells.  Isolated 50-65 mph
gusts and marginally severe hail are the primary hazards.

Remnant, convectively enhanced midlevel troughs will move
east-northeastward from WV and AL, coincident with the diurnal
heating cycle near and east of the Appalachians.  Widely scattered
storm clusters will be possible this afternoon from GA into the
western Carolinas, but poor lapse rates and weak vertical shear will
limit any severe threat.  Though lapse rates will be similarly poor
into the Mid-Atlantic, there will be a zone of stronger low-level
shear/hodograph curvature across northern VA/MD in advance of the
MCV approaching from WV.  Here, a few weakly rotating storms could
produce isolated wind damage and a brief/weak tornado.

...TX/LA/MS...
Remnant MCS will continue to push southward through the middle TX
coast through early afternoon and offshore the southwest LA coast.
Several observation sites late this morning recorded strong gusts
(40-45 kt) but the overall displacement of the gust front from the
thunderstorm cores will likely limit gust potential.  A few storms
may develop farther west this afternoon/evening along the trailing
outflow boundary in the area around DRT.  Large CAPE/steep lapse
rates will support both strong updrafts and downdrafts, though weak
vertical shear will generally limit storm longevity and the
magnitude of any hail/wind threat.  Farther east over LA/MS,
scattered thunderstorms are forecast to develop near the residual
outflow.  An isolated hail/wind threat may develop with the stronger
storms as one or two clusters develops by mid-late afternoon and
early evening.

...ME/NH this afternoon...
Downstream of shortwave ridging in the midlevels, a weak northwest
flow regime will persist this afternoon over northern New England.
Lingering low-level moisture, surface heating in cloud breaks
southeast of the higher terrain, and very subtle midlevel vorticity
maxima will support a few thunderstorms this afternoon across
southern/eastern ME and part of NH.  The latest forecast soundings
show MLCAPE of 1000-1500 J/kg and effective bulk shear near 25 kt
(with longer hodographs aloft) will be sufficient for semi-organized
storms capable of producing isolated wind damage and marginally
severe hail for a few hours this afternoon.

$$