153
ACUS01 KWNS 202002
SWODY1
SPC AC 202001

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0301 PM CDT Thu Jun 20 2024

Valid 202000Z - 211200Z

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

...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, the Four Corners, and southern Lower Michigan.

...20z outlook update discussion...
The only changes made to the outlook are described below.
Otherwise, no change was made to the previous outlook and forecast
reasoning appears on track.

...Southern Lower Michigan...
Surface boundary has become draped west to east across southern
Lower MI with a reservoir of lower 70s deg F surface dewpoints
immediately in the vicinity of the front.  Surface streamline
analysis indicates weak surface convergence and preferential storm
development is expected along the boundary through the early
evening.  Strong to severe gusts (50-65 mph) capable of wind damage
will be the primary hazard with the stronger water-laden downdrafts.
 The ongoing thunderstorm activity will likely slowly migrate
east-southeast into southeast Lower MI towards early evening.

...Four Corners...
The northwest periphery of seasonably high moisture will continue to
support additional storm development through the early to mid
evening across this region.  The development of steep 0-3 km lapse
rates and a wind profile promoting organized single cells/multicells
and perhaps transient supercells, will foster a risk for severe
gusts (60-75 mph) through the early to mid evening with the stronger
microbursts.

...Northeast Colorado...
Have expanded the Slight-Risk equivalent severe probabilities
farther south-southwest to east of the Front Range north/northeast
of Denver.  Storms will move east of the higher terrain of the Front
Range and potentially pose a risk for wind/hail with the stronger
storms.

..Smith.. 06/20/2024

.PREV DISCUSSION... /ISSUED 1112 AM CDT Thu Jun 20 2024/

...Eastern NY and New England...
Visible satellite imagery shows strong daytime heating occurring
across all of New England and parts of NY/PA.  A well-defined MCV
currently over eastern Lake Ontario will track eastward into this
warm and very humid air mass (dewpoints in the low 70s), where
afternoon MLCAPE values will exceed 2000 J/kg.  Scattered to
numerous thunderstorms are expected, with storms spreading eastward
through the afternoon towards the coast of southern ME/NH/MA.  Winds
aloft are not particularly strong, suggest early activity may be
rather disorganized.  However, eventual congealing of outflow will
likely result in locally damaging wind gusts.  Hail will also be
possible in the strongest cells.  Please refer to MCD #1340 for
further details.

...Central High Plains...
Latest surface analysis shows south-southeasterly low-level winds
across the NE Panhandle and southeast WY, where dewpoints are in the
50s and lower 60s.  This will help maintain a moist/unstable air
mass in the area, yielding afternoon MLCAPE values of around 1500
J/kg.  Scattered thunderstorms are expected to form over southeast
WY by 20z, where sufficient deep-layer shear and steep lapse rates
will favor supercell structures capable of very large hail and
perhaps a tornado.  Storms will track eastward into the NE Panhandle
and southern SD through the evening, with an increasing risk of
damaging winds (possibly exceeding 65kt).

...Western CO...
Moderately strong southwesterly low/mid-level flow is present today
across western CO, where full heating and diurnal destabilization
will occur.  Morning models continue to show scattered or greater
thunderstorms coverage this afternoon, in a deeply mixed
environment.  Several fast-moving high-based thunderstorms are
expected, with a risk of locally severe winds in the stronger cores.

$$