Mesoscale Discussion 847

Issued

Jun 9, 2016, 11:44 AM MDT (17:44 UTC)

Expired

Jun 9, 2016, 2:15 PM MDT

In force

3 hr

Issued by

the Storm Prediction Center

Chance of a watch

95%

Counties Broadwater County, MT, Fergus County, MT, Garfield County, MT, Golden Valley County, MT, Judith Basin County, MT, McCone County, MT, Meagher County, MT, Musselshell County, MT, Petroleum County, MT, Wheatland County, MT

The Billings radar (KBLX), 124 km from the middle of the area, began a volume at 17:44 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 239Jun 9, 1:00 PM MDT

122 
ACUS11 KWNS 091745
SWOMCD
SPC MCD 091744 
MTZ000-092015-

MESOSCALE DISCUSSION 0847
NWS STORM PREDICTION CENTER NORMAN OK
1244 PM CDT THU JUN 09 2016

AREAS AFFECTED...PORTIONS OF MONTANA

CONCERNING...SEVERE POTENTIAL...WATCH LIKELY 

VALID 091744Z - 092015Z

PROBABILITY OF WATCH ISSUANCE...95 PERCENT

SUMMARY...THE POTENTIAL FOR SUPERCELL TSTMS WITH SIGNIFICANTLY
SEVERE HAIL...SVR WIND GUSTS...AND PERHAPS A COUPLE OF TORNADOES IS
INCREASING. SVR TSTMS WILL LIKELY BE ONGOING BY AROUND 20Z-21Z...AND
A WW WILL LIKELY BE ISSUED WITHIN THE NEXT COUPLE OF HOURS.

DISCUSSION...VISIBLE SATELLITE LOOPS INDICATE RELATIVELY EARLY
DEVELOPMENT OF DIURNAL...TERRAIN-ENHANCED CUMULUS FIELDS OVER THE
WRN/CNTRL MT MOUNTAINS...FROM THE BITTERROOT RANGE TO THE SWRN MT
MOUNTAINS TO THE LITTLE AND BIG BELT MOUNTAINS. THIS IS LIKELY A
MANIFESTATION OF THE STRENGTHENING LARGE-SCALE ASCENT ACCOMPANYING A
MID-LEVEL SPEED MAX PRESENTLY ORBITING THE SERN SEMI-CIRCLE OF A
CYCLONE CENTERED OFF THE PACIFIC COAST. WATER VAPOR LOOPS SUGGEST
THAT THE SPEED MAX IS ALREADY SPREADING ACROSS WRN MT. GIVEN THE
ASSOCIATED ENHANCED LARGE-SCALE ASCENT...DIURNAL CONVECTIVE
INITIATION OVER THE MOUNTAINS WILL LIKELY OCCUR EARLIER TODAY THAN
TYPICAL OF PATTERNS LACKING LARGE-SCALE ASCENT. BY 19Z-20Z...TSTMS
WILL LIKELY BECOME WIDELY SCATTERED FROM THE HELENA/BUTTE REGION
TOWARD THE LEWISTOWN AREA...AND THEN SPREAD ENEWD INVOF AND
IMMEDIATELY ON THE COOL SIDE OF A QUASI-STATIONARY BOUNDARY ANALYZED
FROM BETWEEN JORDAN AND GLENDIVE...TO S OF LEWISTOWN...TO NEAR
BUTTE.

THE AIR MASS NEAR/N OF THE BOUNDARY CONTINUES TO DESTABILIZE OWING
TO THE LACK OF ANY SUBSTANTIAL INFLUXES OF CONTINENTAL AIR SUBJECTED
TO DOWNSLOPE WARMING/DRYING. SUCH FLUXES WILL PRINCIPALLY AFFECT THE
GREAT FALLS TO CUT BANK TO HAVRE AREA AMIDST SWLY FLOW
ALOFT...LEAVING A 90-120-MILE-WIDE CORRIDOR CENTERED ON HELENA TO
LEWISTOWN TO E OF JORDAN WITH MLCAPE AROUND 750-1500 J/KG. THIS WILL
BE AIDED BY STEEP MID-LEVEL LAPSE RATES OVERLYING ADEQUATE LOW-LEVEL
MOISTURE -- E.G. DEWPOINTS REMAIN IN THE 50S ACROSS PORTIONS OF
CNTRL MT ON THE COOL SIDE OF THE BOUNDARY. AS 50-65 KT OF EFFECTIVE
BULK SHEAR OVERLAPS WITH THE DESTABILIZING AIR MASS...TSTMS THAT
DEVELOP WILL LIKELY BECOME SUPERCELLULAR QUICKLY. FORECAST WIND
PROFILES SUPPORT LONG/CURVED HODOGRAPHS THROUGH MUCH OF THE
CONVECTIVE LAYER...WITH EFFECTIVE SRH AROUND 100-200 M2/S2 THIS
AFTERNOON. PERSISTENT MESOCYCLONES WILL HAVE THE POTENTIAL TO
PRODUCE SIGNIFICANT SEVERE HAIL...SVR WIND GUSTS...AND PERHAPS A
COUPLE OF TORNADOES.

PRESENT INDICATIONS ARE THAT THE GREATEST TORNADO POTENTIAL WILL
EXTEND FROM MEAGHER COUNTY TO JUDITH BASIN COUNTY TO FERGUS AND
PETROLEUM COUNTIES...AND EXTREME NRN PARTS OF WHEATLAND...GOLDEN
VALLEY...AND MUSSELSHELL COUNTIES. ENHANCED VERTICAL VORTICITY ALONG
THE SFC BOUNDARY...COMBINED WITH A WEAK NLY-FLOW COMPONENT IN THE
LOWEST 1 KM MODESTLY ELONGATING LOW-LEVEL HODOGRAPHS...MAY SUPPORT
SUSTAINED LOW-LEVEL MESOCYCLONES IN THESE AREAS. THIS IS ALSO WHERE
RELATIVELY GREATER BOUNDARY-LAYER MOISTURE EXISTS IN PROXIMITY TO
THE BOUNDARY. HOWEVER...GIVEN SOME TENDENCY FOR SFC
TEMPERATURE-DEWPOINT SPREADS TO INCREASE FAVORING MORE
OUTFLOW-DOMINANT TSTMS...AND GIVEN THE LIMITED LOW-LEVEL MASS
RESPONSE PREVENTING HODOGRAPHS IN THE LOWEST 1 KM AGL FROM BECOMING
ESPECIALLY LONG...THE OVERALL TORNADO POTENTIAL MAY BE MITIGATED TO
SOME EXTENT. REGARDLESS...SIGNIFICANTLY SEVERE HAIL AND SEVERE WIND
GUSTS WILL LIKELY ACCOMPANY CONVECTION THIS AFTERNOON --
PARTICULARLY IN THE 20Z-00Z TIME FRAME.

..COHEN/DIAL.. 06/09/2016

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

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

LAT...LON   46131011 46051160 46301208 46871167 47481039 48060805
            48180580 47840474 46980551 46500744 46131011

Mesoscale Discussions in Montana, 2016Every mesoscale discussion in 2016

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.