SPC MD 1342

MD 1342 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR FOUR CORNERS INTO SOUTHERN NEVADA
MD 1342 Image


Mesoscale Discussion 1342
NWS Storm Prediction Center Norman OK
0301 PM CDT Sat Jul 24 2021

Areas affected...Four Corners into southern Nevada

Concerning...Severe potential...Watch unlikely 

Valid 242001Z - 242200Z

Probability of Watch Issuance...20 percent

SUMMARY...Several clusters of thunderstorms across northern New
Mexico and southern Utah have recently shown signs of
intensification. These storms and additional development may pose a
risk for damaging winds or small hail this afternoon and evening.

DISCUSSION...Within a monsoonal flow regime beneath a weak upper
low, strong diurnal heating and weak ascent have allowed several
clusters of thunderstorms to become established over portions of the
Southwest in the last couple of hours. As heating and orographic
ascent continue, additional thunderstorm development appears likely.
Within the high PWAT airmass, SPC mesoanalysis indicates 500-1000
J/kg of MLCAPE has developed. While thermodynamics are favorable for
robust updrafts, a blocking ridge of high pressure in the mid levels
should limit flow aloft and resulting vertical shear to below 25
kts. A multicellular storm mode is expected with the stronger storms
capable of damaging wind gusts and small hail. A locally greater
risk of damaging wind gusts may develop if storm outflows are able
to evolve into small clusters as suggested by some hi-res guidance.
However, given the low predictability and expected limited severe
threat, a watch is unlikely at this time.

..Lyons/Hart.. 07/24/2021

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

ATTN...WFO...ABQ...GJT...FGZ...SLC...VEF...

LAT...LON   36521526 37381456 37601320 37611229 37571105 37230966
            37010892 36630819 36250784 35800784 35230798 34800888
            34740966 34721061 34851193 35021295 35191412 36521526 

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SPC MD 1341

MD 1341 CONCERNING SEVERE POTENTIAL...WATCH POSSIBLE FOR PARTS OF SOUTHERN LAKE MICHIGAN...NORTHERN ILLINOIS AND ADJACENT NORTHWESTERN INDIANA...INTO PARTS OF SOUTHEASTERN IOWA
MD 1341 Image


Mesoscale Discussion 1341
NWS Storm Prediction Center Norman OK
0300 PM CDT Sat Jul 24 2021

Areas affected...Parts of southern Lake Michigan...northern Illinois
and adjacent northwestern Indiana...into parts of southeastern Iowa

Concerning...Severe potential...Watch possible 

Valid 242000Z - 242200Z

Probability of Watch Issuance...60 percent

SUMMARY...Widely scattered to scattered strong thunderstorm
development appears increasingly possible through 5-7 PM CDT,
particularly around the Greater Chicago metropolitan area, posing a
risk for a few strong downbursts.

DISCUSSION...Deepening convective development is ongoing along a
zone of boundary-layer confluence near/south of a slowly southward
advancing convective outflow boundary, with thunderstorms beginning
to initiate near/northwest of the Greater Chicago metropolitan area.

This coincides with a low-level thermal ridge axis, along which
strong daytime heating has contributed to steepening near surface
lapse rates and mixed-layer CAPE on the order of 2000+ J/kg. This is
also near the southwestern periphery of larger-scale mid-level
troughing shifting across and to the east of the Great Lakes
vicinity, where 30-40 kt northwesterly flow around 500 mb is
contributing to strong deep-layer shear.

Although forcing for ascent, particularly in mid/upper levels, may
only allow for widely scattered thunderstorm development to the
west-southwest of southern Lake Michigan late this afternoon, much
of the Greater Chicago metro may be impacted.  This could include an
upscale growing line or clusters of storms with the potential to
produce at least a few strong downbursts.

..Kerr/Hart.. 07/24/2021

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

ATTN...WFO...IWX...LOT...ILX...DVN...

LAT...LON   41619143 42308965 42558661 41638688 41228927 40569141
            41619143 

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