ACUS01 KWNS 201250
SWODY1
SPC AC 201249

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0749 AM CDT Thu Jun 20 2024

Valid 201300Z - 211200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE
NORTH-CENTRAL HIGH PLAINS AND NORTHEAST/NEW ENGLAND...

...SUMMARY...
Storms may produce scattered damaging wind gusts over parts of the
Northeast and New England mainly this afternoon. Scattered severe
storms are also expected over parts of the north-central High
Plains.

...Northeast States/New England...
The prominent upper anticyclone currently centered over the middle
Atlantic will gradually build westward across the CONUS today, while
some flattening of the ridge will occur over the Northeast and
especially New England. The stronger mid-level westerlies will be
located closer to the international border and across eastern
Canada, with weaker winds aloft over the lower Great Lakes into
southern New England. A surface cold front will advance south into
northern Maine, extending westward into southern lower Michigan by
midday, with subsequent southeastward movement expected across the
Northeast through early evening.

This boundary will serve as the focus for intensifying convection
later today as surface temperatures quickly soar through the 80s
into the lower 90 F, with a weak mid-level impulse/MCV near Lake
Ontario this morning being an additional influence. While deep-layer
shear will not be particularly strong in most areas, PW values are
seasonally moist with 1.5-2 inches expected, contributing to upwards
of 2000-3000 MLCAPE this afternoon particularly across upstate New
York and interior New England/southern Maine. Damaging winds will be
possible with the strongest storms this afternoon.

...North-Central Plains...
Weak mid-level height rises will occur over the central Plains
through tonight, with a belt of moderately strong west-southwesterly
flow aloft, and few embedded disturbances, from Utah/Wyoming toward
the Dakotas and Upper Midwest. Surface cyclogenesis, focused across
northeast Colorado later today, will contribute to a
north-northwestward flux of low-level moisture across the central
High Plains/eastern Wyoming and Black Hills vicinity.

Initial thunderstorm development/intensification will occur over the
mountains toward southeast Wyoming/Colorado Front Range by
mid-afternoon, with subsequent development into the nearby High
Plains this evening, in areas near/north of the surface low/triple
point and east/northeastward-extending front. Initial storm mode
should be supercellular and large hail is expected.

Aided by an early evening strengthening of a southerly low-level
jet, storms will likely consolidate and grow upscale into a possible
MCS within the warm-advection zone focused across western/northern
Nebraska and south-central/southern South Dakota. Severe wind gusts
could materialize along the leading edge of the MCS.

...Central Rockies/Four Corners Area...
While not overly moist regionally, a west-northwestward flux of
moisture and a moderately strong belt of southwesterly mid-level
flow will contribute to sustained thunderstorms, particularly from
mid-afternoon through early evening. Some of these may produce
severe-caliber downbursts.

...South Texas...
Supercell/brief tornado related to Tropical Storm Alberto is
expected to continue to diminish this morning as it moves inland and
weakens over northeast Mexico.

...Central/eastern Montana...
A weak mid-level disturbance, moderately strong flow aloft, and an
adequately moist boundary layer may contribute to some
strong/locally severe storms late this afternoon and early evening,
with hail/gusty winds possible.

..Guyer/Leitman.. 06/20/2024

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