LIVE MAP (ABOVE) ... SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1248 AM CDT Mon May 22 2023
Valid 221200Z - 231200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE
SOUTHERN HIGH PLAINS...
...SUMMARY...
Severe thunderstorms are possible across portions of the southern
High Plains this afternoon and evening. Large hail and damaging
gusts will be the primary hazards with these storms. Additional
strong to isolated severe thunderstorms are possible across portions
of Montana, and parts of southern Alabama/Georgia into Florida.
...Southern High Plains...
Weak mid-level disturbance is currently located along the northern
periphery of a detached weak southern branch (southeast CO/northeast
NM). This feature is expected to drift into the eastern TX Panhandle
later today which will allow northwesterly flow at 500mb to
strengthen a bit across the TX Panhandle into portions of northwest
TX. Seasonally cool 500mb temperatures (minus 10-12C) will persist
across much of the southern Plains and strong boundary-layer heating
across this region will contribute to steep lower tropospheric lapse
rates. Scattered convection is ongoing ahead of this mid-level
feature from southwest KS into the TX South Plains. However, it's
not particularly strong or organized at this time. In the absence of
a notable LLJ, this activity should remain disorganized and weak
through sunrise, and likely continue to weaken through 18z. With
time boundary-layer heating will remove inhibition and surface
parcels will breach convective temperatures, likely by 21z. Latest
thinking is scattered robust storms will evolve within northwest
flow regime, aided by the weak disturbance, across the High Plains
of west TX. This activity should propagate slowly southeast during
the late afternoon/evening with an attendant threat for hail/wind.
...MT...
High-level diffluent flow will overspread MT ahead of a strong,
progressive trough Monday. Latest data suggests one 500mb speed max
will translate trough the base of the trough over OR before ejecting
into northwest MT by 23/00z, then into southern AB by the end of the
period. This evolution would allow meaningful height falls to spread
across the northern Rockies which will encourage a surface front to
surge into central MT by late afternoon. While boundary-layer
moisture is not particularly high across the northern High Plains,
it appears PW values should increase to around 1 inch ahead of the
surface wind shift. Surface heating and orographic influence should
lead to scattered, potentially robust, convection initiating across
the higher terrain by 20z. This activity would then spread northeast
toward lower elevations where steep lapse rates and thermodynamic
profiles would appear supportive of gusty winds along with some hail
threat.
...FL Region...
25-30kt 500mb westerly flow will persist across the FL Peninsula
Monday as low-latitude southern stream will continue into the day2
period. It's not entirely clear whether a weak disturbance will
actually influence convection during the day, but seasonally cool
mid-level temperatures and boundary layer heating will prove
instrumental in thunderstorm development. Robust convection is
possible across the Peninsula into southeast AL. Gusty winds are the
primary concern with scattered convection that materializes by mid
day and continues into the early evening.
..Darrow/Thornton.. 05/22/2023
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