Mesoscale Discussion 839

Issued

Jun 7, 2016, 12:50 PM MDT (18:50 UTC)

Expired

Jun 7, 2016, 3:15 PM MDT

In force

2 hr

Issued by

the Storm Prediction Center

Chance of a watch

5%

Counties Broadwater County, MT, Cascade County, MT, Deer Lodge County, MT, Fergus County, MT, Gallatin County, MT, Golden Valley County, MT, Granite County, MT, Jefferson County, MT, Judith Basin County, MT, Lewis and Clark County, MT, Madison County, MT, Meagher County, MT, Park County, MT, Powell County, MT, Silver Bow County, MT, Stillwater County, MT, Sweet Grass County, MT, Wheatland County, MT

The Great Falls radar (KTFX), 138 km from the middle of the area, began a volume at 18:51 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.

214 
ACUS11 KWNS 071850
SWOMCD
SPC MCD 071850 
MTZ000-072115-

MESOSCALE DISCUSSION 0839
NWS STORM PREDICTION CENTER NORMAN OK
0150 PM CDT TUE JUN 07 2016

AREAS AFFECTED...PORTIONS OF MONTANA

CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY 

VALID 071850Z - 072115Z

PROBABILITY OF WATCH ISSUANCE...5 PERCENT

SUMMARY...TSTMS WILL CONTINUE TO INCREASE IN NUMBER AND INTENSITY
DURING THE NEXT SEVERAL HOURS...AND A FEW TSTMS MAY PRODUCE
MARGINALLY SVR HAIL/WIND. WW ISSUANCE WILL NOT BE NECESSARY.

DISCUSSION...MESO-BETA-SCALE ASCENT ON THE ERN/SRN PERIPHERY OF A
MID-LEVEL IMPULSE ASSOCIATED WITH LIGHTNING NEAR MISSOULA...AND
DIURNALLY ENHANCED OROGRAPHIC CIRCULATIONS AMIDST A MODESTLY MOIST
AIR MASS /PW AROUND 0.75-0.85 INCH PER GPS DATA AND THE 12Z TFX
RAOB/...WILL FACILITATE AN INCREASE IN TSTM COVERAGE/INTENSITY
THROUGHOUT THE AFTERNOON HOURS. INCREASING CUMULUS COVERAGE/DEPTH
AND ISOLATED LIGHTNING DEVELOPMENT ARE ALREADY ONGOING OVER THE
LITTLE BELT MOUNTAINS SE OF GREAT FALLS...WITH OTHER CUMULUS
DEVELOPMENT OCCURRING OVER MOUNTAINS ELSEWHERE...ASIDE FROM THE
ONGOING CONVECTION CLOSER TO THE IMPULSE NEAR MISSOULA.

TSTMS SHOULD BECOME SCATTERED TO PERHAPS NUMEROUS BY 21Z-22Z.
DESPITE MLCAPE REMAINING MODEST -- I.E. AROUND 500-1250 J/KG --
GIVEN THE DEARTH OF RICH BOUNDARY-LAYER MOISTURE...UPDRAFT
ACCELERATIONS OWING TO STEEP TROPOSPHERIC LAPSE RATES MAY SUPPORT
ISOLATED MARGINALLY SVR HAIL WITH THE MOST INTENSE CORES. ISOLATED
MARGINALLY SVR WIND GUSTS MAY ALSO OCCUR...ESPECIALLY BY MID/LATE
AFTERNOON AS COLD POOLS LOCALLY AMALGAMATE AND SPREAD GENERALLY EWD
ACROSS THE LOWER ELEVATIONS/PLAINS OF CNTRL MT WHERE SUB-CLOUD
EVAPORATIONAL COOLING WILL ENHANCE DOWNDRAFT ACCELERATIONS.
HOWEVER...THE PAUCITY OF DEEP SHEAR AMIDST LARGER-SCALE RIDGING WILL
MITIGATE CONVECTIVE ORGANIZATION...AND THIS SHOULD INHIBIT OVERALL
SUSTENANCE OF INDIVIDUAL INTENSE CONVECTIVE ELEMENTS AND TEND TO
MARGINALIZE THE SVR POTENTIAL.

..COHEN/DIAL.. 06/07/2016

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

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

LAT...LON   45011087 45071232 45501325 46471391 47351289 47861100
            47710951 47090863 46290847 45320920 45011087

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.