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Day 2 Convective Outlook  
NWS Storm Prediction Center Norman OK
1228 PM CDT Sat Jun 18 2022

Valid 191200Z - 201200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF
EASTERN MONTANA AND WESTERN NORTH DAKOTA...

...SUMMARY...
Scattered severe thunderstorms with damaging gusts and hail are
possible across portions of eastern Montana into western North
Dakota Sunday afternoon and evening. Additional isolated strong
storms may occur into western South Dakota, eastern Wyoming, western
Nebraska and northeast Colorado, as well as parts of the Florida
Peninsula.

...Synopsis...

A highly amplified upper pattern will persist on Sunday. The upper
ridge will be centered over the MS Valley vicinity and will be
flanked by upper troughs over the western U.S. and the Northeast.
These systems will drift eastward through the period, with a more
focused area of large-scale ascent overspreading the northern High
Plains vicinity. Strong deep-layer south/southwesterly flow will
extend over much of the Rockies into western portions of the
northern and central Plains between the western trough and central
states ridge. At the surface, high pressure will persist over the
Great Lakes/Midwest. Continental trajectories within the area of
high pressure will maintain dry conditions across much of the
Midwest, with strong dewpoints confined to Florida and the Gulf
Coast. An increasing baroclinic zone across the Plains will result
in increasing southerly low-level flow, and 60s F dewpoints will
spread across eastern portions of the Great Plains. Deepening
surface low pressure over Saskatchewan and Manitoba into eastern
MT/ND will allow upper 50s to low 60s F dewpoints to filter into
western ND and eastern MT. 

...MT/ND into northeast CO...

A surface trough is forecast to extend across the northern High
Plains on Sunday, with a weak surface low developing near the MT/ND
border. Higher quality boundary-layer moisture is forecast to filter
into eastern MT as this occurs, aiding in moderate to strong
destabilization. Dewpoints will be lower into eastern WY/western
SD/NE and northeast CO, though steep midlevel lapse rates will still
contribute to modest instability (generally 1000 J/kg MLCAPE or
less). Strong heating will result in a well-mixed sub-cloud layer,
with inverted-v thermodynamic profiles evident in regional forecast
soundings. 

High-based thunderstorms will initially develop over higher terrain
and spread northeast. Modest effective shear magnitudes from CO into
eastern WY/western SD will limit longevity of organized convection,
but a dry sub-cloud layer will support strong outflow gusts.

Strong vertical shear, with effective shear magnitudes greater than
40 kt is expected to overlap with strong boundary-layer
moisture/instability across parts of eastern MT into western ND.
Greater potential for organized supercells or bowing segments will
reside across this area, bringing a threat for severe gusts and
large to very large hail. 

...Florida Peninsula...

Similar to the past couple of days, a very moist and unstable
airmass will reside across Florida within northeasterly midlevel
flow on the eastern periphery of the upper ridge. Southwesterly
low-level winds beneath this northeasterly midlevel flow will result
in 20-25 kt effective shear magnitudes amid 1500-2500 J/kg MLCAPE.
Thunderstorm clusters are expected by early afternoon and PW values
greater than 1.7 inches may support water-loaded downdrafts capable
of strong outflow winds. Storm interactions may also result in local
areas of forward-propagating clusters, further supporting
sporadic/isolated damaging gusts.

..Leitman.. 06/18/2022