LIVE MAP (ABOVE) ... SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1257 AM CDT Sun Jul 16 2023
Valid 161200Z - 171200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF
THE CENTRAL PLAINS AND NEW ENGLAND...
...SUMMARY...
Scattered large hail (some very large) and severe wind is possible
across the Central Plains. A few tornadoes will be possible across
portions of the Northeast. Isolated damaging wind gusts will be
possible from the Red River to the Gulf Coast.
...Synopsis...
A large upper-level trough, centered over the western Great Lakes
early this morning, will continue to amplify through the day. A weak
surface low is expected to develop across western/central New York
this morning. Farther west, a cold front extends from Upper
Michigan, across central Wisconsin, into northern Iowa and northern
Nebraska. The front will continue south/east across the Great Lakes
but is expected to stall across the Plains/Corn Belt by mid-day.
...Mid Atlantic to New England...
A very moist airmass is in place across the East Coast with 1.9 to
2.2 inch PWAT values on most 00Z RAOBs and mid 70s dewpoints from
the Carolinas to New England. Within this moist environment, SPC
mesoanalysis suggests an uncapped ML parcel across much of New
England early this morning which should remain through mid-day.
Therefore, despite expansive cloud-cover and minimal surface
heating, expect 1000-1500 J/kg MLCAPE across New England this
morning. Across the same region, surface flow will strengthen
somewhat in response to the developing surface cyclone. A 40 knot
low-level jet will develop and overspread New England between 12Z
and 18Z. This will yield 0-500m SRH around 100 to 150 m2/s2 with
clockwise curvature in the lowest 1km. Given the moist profile,
lapse rates will be very poor which may result in relatively weak
updrafts. However, if stronger, sustained updrafts can develop, a
couple of tornadoes are possible across portions of New England,
primarily before 17Z.
...Central Plains into the Midwest...
A cluster of elevated thunderstorms, visible on composite radar
across northeast Wyoming/southwest South Dakota will likely be
ongoing at the beginning of the period across south-central
Nebraska. Evolution of this activity remains unclear as some 00Z CAM
guidance shows it persisting through the morning and intensifying by
early afternoon as the boundary layer destabilizes while other
guidance has morning activity decaying and new afternoon convection
developing along the remnant outflow boundary. Regardless of the
exact solution, there will be some threat for severe wind gusts and
large hail across northeast Kansas and vicinity.
Across central Kansas, confidence is higher for a very unstable
airmass to develop with the outflow boundary from morning
convection, potentially acting as a focus for thunderstorm
development during the afternoon. Strong instability and 45-50 knots
of effective shear will support supercell storm mode with the
potential for some very large (2+ inch) hail. Storms may eventually
congeal into a cluster across central Kansas with an increasing
damaging wind threat into the evening.
...TX/OK Red River to the Central Gulf Coast...
Thunderstorms will likely be ongoing at the beginning of the period
near the Red River. A cold pool is expected to emanate eastward from
this cluster across north Texas during the morning. A very unstable
airmass is expected by mid day with temperatures in the 90s and
dewpoints in the upper 70s yielding 3000 to 4000 J/kg MLCAPE.
Thunderstorms are expected to reintensify/develop downstream by
midday/early afternoon. Despite mostly weak shear (15 to 20 knots),
some damaging wind gusts will be possible given the extreme
instability present in the region.
..Bentley/Wendt.. 07/16/2023
Read more CHECK UPDATE ZOOM GRAPHIC
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