Mesoscale Discussion 0447
NWS Storm Prediction Center Norman OK
0110 PM CDT Mon Apr 14 2025
Areas affected...parts of cntrl/sern SD...swrn MN...nern IA...nern
NE
Concerning...Severe potential...Watch unlikely
Valid 141810Z - 142115Z
Probability of Watch Issuance...5 percent
SUMMARY...Showers spreading southeastward through the mid Missouri
Valley may begin to intensify by 3-4 PM CDT, with a few weak
thunderstorms developing and posing increasing potential for strong
to severe surface gusts while spreading southeastward through the
remainder of the afternoon.
DISCUSSION...In the wake of a deep cyclone, now migrating northeast
of the Upper Great Lakes region, downward mixing of momentum is
already contributing to 30-35+ kt northwesterly surface gusts across
much of the middle Missouri Valley, as boundary-layer warming
progresses. This is occurring just ahead of a vigorous short wave
trough now digging through the western Dakotas, and forecast to
continue rapidly southeastward through early evening.
Models indicate that the mid-level cold core (including -30 to -35C
around 500 mb) will overspread a corridor from central South Dakota
through northeastern Iowa between 20-23Z, coincident with further
strengthening of northwesterly flow (35-40+ kt) in the 850-700 mb
layer and peak afternoon surface heating. As this occurs, forecast
soundings indicate that profiles will become increasingly conducive
to deepening convection capable of producing lightning.
With at least some further intensification of ongoing developing
convection, evaporative cooling and melting of precipitation within
an increasing well-mixed boundary layer (characterized by sizable
surface temperature/dew point spreads on the order of 20+ F),
coupled with the downward mixing of stronger flow aloft, seems
likely to contribute to increasing potential for surface gusts
approaching or briefly exceeding severe limits. This may continue
into early evening, as convection spreads southeastward, before
rapidly diminishing with the onset of boundary-layer cooling.
..Kerr/Mosier.. 04/14/2025
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...MPX...DMX...FSD...OAX...ABR...UNR...
LAT...LON 44969838 44749683 43839520 43419469 42209542 42309648
42919815 43719996 44779996 44969838
MOST PROBABLE PEAK WIND GUST...UP TO 60 MPH
Source link