693
ACUS11 KWNS 171909
SWOMCD
SPC MCD 171908
COZ000-NEZ000-SDZ000-WYZ000-172145-

Mesoscale Discussion 2079
NWS Storm Prediction Center Norman OK
0208 PM CDT Tue Sep 17 2024

Areas affected...eastern Wyoming...northeastern/east central
Colorado...adjacent southwestern South Dakota and western Nebraska

Concerning...Severe potential...Watch possible

Valid 171908Z - 172145Z

Probability of Watch Issuance...60 percent

SUMMARY...High-based thunderstorm development appears increasingly
probable across and east of the Front Range by 3-5 PM MDT,
accompanied by increasing potential for strong to severe wind gusts
while spreading through the adjacent high plains through early
evening.  One or two severe weather watches are possible, though
timing remains somewhat uncertain.

DISCUSSION...Downstream of a vigorous short wave trough pivoting
northeastward toward the Wyoming/Colorado Rockies, southwesterly
mid/upper flow is in the process of strengthening.  This is forecast
to include speeds of 40-70+ kt in the 500-300 mb layer across and
northeast of the Front Range, above a boundary layer across the high
plains which is becoming strongly heated and deeply mixed.  Surface
temperature/dew points already have commonly reached 40-45 degrees
across much of eastern Colorado and Wyoming.

While boundary-layer moisture content is generally low, various
model output indicates that steepening lower/mid-tropospheric lapse
rates, along the leading edge of mid-level cooling now approaching
the Front Range, will support increasing high-based convective
development along and east of the higher terrain by 20-22Z.
Updrafts might not be particularly intense, at least initially as
activity begins to spread toward the high plains, but sub-cloud
evaporative cooling and downward mixing of cloud-bearing mean flow
on the order of 50 kt are likely to contribute to the risk for
strong to severe downbursts.  Thereafter, the potential for strong
to severe wind gusts may gradually become more widespread as
convective outflow becomes more widespread and strengthens while
surging northeastward and eastward.

..Kerr/Gleason.. 09/17/2024

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...UNR...GLD...PUB...BOU...CYS...

LAT...LON   43860453 43310377 42380364 41490341 39840284 38860290
            38430401 39050489 40020512 41470531 42270551 43080550
            43860453