Mesoscale Discussion 1053

Issued

Jun 4, 2012, 2:17 PM MDT (20:17 UTC)

Expired

Jun 4, 2012, 3:45 PM MDT

In force

88 min

Issued by

the Storm Prediction Center

Chance of a watch

95%

The Great Falls radar (KTFX), 96 km from the middle of the area, began a volume at 20:21 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

• Severe Thunderstorm Watch 354Jun 4, 4:30 PM MDT
• Tornado Watch 355Jun 4, 5:50 PM MDT

520 
ACUS11 KWNS 042017
SWOMCD
SPC MCD 042017 
MTZ000-042145-

MESOSCALE DISCUSSION 1053
NWS STORM PREDICTION CENTER NORMAN OK
0317 PM CDT MON JUN 04 2012

AREAS AFFECTED...PORTIONS OF NRN/CNTRL/WRN MT

CONCERNING...SEVERE POTENTIAL...SEVERE THUNDERSTORM WATCH LIKELY 

VALID 042017Z - 042145Z

PROBABILITY OF WATCH ISSUANCE...95 PERCENT

SUMMARY...THE THREAT FOR SEVERE THUNDERSTORMS WILL INCREASE THIS
AFTERNOON ACROSS PARTS OF MONTANA. LARGE HAIL AND DAMAGING WINDS
WILL BE THE PRIMARY CONCERNS WITH THIS ACTIVITY...AND A SVR TSTM
WATCH WILL BE ISSUED BY 2100Z. WHILE A TORNADO THREAT CANNOT BE
RULED OUT ACROSS PARTS OF CNTRL/N-CNTRL MT.

DISCUSSION...EARLY-AFTERNOON SFC MESOANALYSIS PLACES A WARM FRONT
EXTENDING FROM A LOW OVER NERN ORE EWD ACROSS CNTRL ID INTO SWRN MT
THAT ARCS NEWD INTO E-CNTRL MT BEFORE EXTENDING SEWD INTO THE
DAKOTAS. A NE-SW ORIENTED ZONE OF SFC PRESSURE FALLS AOA 2 MB PER 2
HRS EXTENDS FROM NEAR THE HAVRE AREA SWWD TOWARD GREAT FALLS AND
FARTHER SW INTO SWRN MT AND E-CNTRL ID....WHICH LIKELY REFLECTS THE
COMBINED IMPACTS OF MODEST LEE CYCLOGENESIS SUPERIMPOSED ON
INCREASING LARGE-SCALE FORCING FOR ASCENT. THE ISALLOBARIC RESPONSE
TO THE PRESSURE FALLS WILL HELP THE FRONT GRADUALLY ADVANCE NWD
THROUGH LATE AFTERNOON WHILE STRONG INSOLATION/DIABATIC HEATING
CONTINUES TO ERODE ANTECEDENT CONVECTIVE INHIBITION.

A PLUME OF RELATIVELY RICH LOW-LEVEL MOISTURE...WITH SFC DEWPOINTS
IN THE UPPER 40S TO THE 50S...EXTENDS ACROSS ERN MT...AND INTO PARTS
OF CNTRL MT NORTH OF THE WARM FRONT. THESE DEWPOINTS SHOULD BE
MAINTAINED THROUGH THE AFTERNOON WHILE TEMPERATURES CONTINUE TO
RISE...AS VERTICAL MIXING OCCURS INTO ENHANCED PACIFIC MOISTURE
OVERLAYING THE AREA /PW VALUES IN EXCESS OF 0.8 INCH PER GPS DATA/.
GIVEN THE AFOREMENTIONED LOW-LEVEL MOISTURE BENEATH 700-500-MB LAPSE
RATES OF 7-8 C/KM...MLCAPE VALUES WILL LIKELY INCREASE TO 750-1500
J/KG. TOWERING CUMULUS FIELD IS BECOMING INCREASINGLY AGITATED PER
VISIBLE SATELLITE IMAGERY FROM SWRN MT INTO CNTRL ID...WHERE CINH IS
FIRST TO BE ERODED AS MOUNTAINS SERVE AS ELEVATED HEAT SOURCES.
STORMS WILL TRACK QUICKLY NNEWD TO ENEWD ACROSS THE NRN ROCKY
MOUNTAIN FRONT AND ADJACENT HIGH PLAINS OF CNTRL/N-CNTRL MT INTO THE
EARLY EVENING.

GIVEN STRONG MID-LEVEL FLOW SUPPORTING 45-55 KT OF DEEP
SHEAR...JUXTAPOSED WITH THE AFOREMENTIONED BUOYANCY...PERSISTENT
SUPERCELL STRUCTURES WILL BE POSSIBLE /POSSIBLY EVOLVING INTO BOWING
LINE SEGMENTS/...ESPECIALLY WITH CONVECTION ACROSS CNTRL/N-CNTRL MT
NEAR AND NORTH OF THE WARM FRONT. SVR WIND/HAIL WILL BE OF CONCERN
WITH THESE STORMS...AND SOME SIGNIFICANTLY SVR WIND WILL BE POSSIBLE
AS DCAPE VALUES CLIMB TO 1000-1300 J/KG.

A TORNADO THREAT MAY ALSO DEVELOP WITH THE STRONGEST/MOST PERSISTENT
SUPERCELLS NEAR AND NORTH OF THE FRONT...EAST OF THE FRONT RANGE
TOWARD GREAT FALLS AND HAVRE. BACKED SFC WINDS IN THESE AREAS WILL
SUPPORT THE GREATEST LOW-LEVEL HODOGRAPH CURVATURE.
HOWEVER...RELATIVELY HIGH LFC/LCL HEIGHTS AND AT LEAST MODEST SFC
TEMPERATURE-DEWPOINT SPREADS...WILL ALSO ACT TO LIMIT THE TORNADO
POTENTIAL. THIS AREA WILL CONTINUE TO BE MONITORED FOR A POTENTIAL
UPGRADE TO A TORNADO WATCH LATER THIS AFTERNOON INTO THE
EVENING...SHOULD A SUPERCELL THREAT APPEAR MORE LIKELY TO EVOLVE
WITHIN THE HELICITY-RICH ENVIRONMENT NEAR AND NORTH OF THE WARM
FRONT.

..COHEN/CARBIN.. 06/04/2012

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...BYZ...GGW...TFX...

LAT...LON   44731285 45301347 45641354 45711317 45541270 45721213
            46081231 46451212 46751222 47171271 47651291 48041280
            48291307 48661346 48941349 49021226 49021090 48870919
            47960829 46620833 45600869 45080914 45221013 45091124
            44801217 44731285

Mesoscale Discussions in Montana, 2012Every mesoscale discussion in 2012

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.