Mesoscale Discussion 77

Issued

Feb 13, 2021, 4:38 PM MST (23:38 UTC)

Expired

Feb 13, 2021, 6:45 PM MST

In force

2 hr

Issued by

the Storm Prediction Center

Concerning

Severe potential...watch unlikely

Chance of a watch

5%

Counties Gila County, AZ, Yavapai County, AZ

The Flagstaff radar (KFSX), 38 km from the middle of the area, began a volume at 23:40 UTC, the scan nearest the moment this went out.

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600 
ACUS11 KWNS 132338
SWOMCD
SPC MCD 132338 
AZZ000-140145-

Mesoscale Discussion 0077
NWS Storm Prediction Center Norman OK
0538 PM CST Sat Feb 13 2021

Areas affected...The Mogollon Rim and adjacent portions of northern
and central Arizona

Concerning...Severe potential...Watch unlikely 

Valid 132338Z - 140145Z

Probability of Watch Issuance...5 percent

SUMMARY...Scattered thunderstorms will continue to develop across
and east-southeast of the Mogollon Rim vicinity through 6-8 PM MST. 
Some could approach the Greater Phoenix Metropolitan area, but
activity, in general, may tend to pass by to the north and
northeast.

DISCUSSION...The left exit region of an intense, broadly
cyclonically curved mid/upper jet streak (90-100+ kt around 500 mb)
is gradually digging southeast of the southern Great Basin, into the
Mogollon Rim vicinity (and adjacent plateau and deserts) of northern
and central Arizona.  This will continue through early evening, with
associated lift and mid-level cooling overspreading areas which have
undergone seasonably modest boundary-layer warming and mixing. 

Despite weak CAPE, this has been sufficient to support considerable
scattered weak low-topped thunderstorm activity, which seems likely
to persist while spreading with the forcing across much of the
remainder of the Mogollon Rim vicinity through 01-03Z.  Although the
convection is not particularly intense, based on the forecast
soundings, where the environment has not already been impacted by
precipitation, the cooling within the well-mixed sub-cloud layer
(due to melting graupel and evaporation) will probably continue to
contribute to downward mixing of the higher momentum just off the
surface.  This appears to include 40-50+ kt in the lowest 3-6 km
AGL, contributing to the continuing potential for a few severe
surface gusts exceeding severe criteria.

..Kerr/Guyer.. 02/13/2021

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

ATTN...WFO...FGZ...PSR...

LAT...LON   35311307 35551142 34810940 34070973 33611059 34031222
            34561328 35311307

Mesoscale Discussions in Arizona, 2021Every mesoscale discussion in 2021

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.