Alert archive / North Dakota / Mesoscale Discussions in 2012

Mesoscale Discussion 1637

July 28, 20124 counties in Montana; 5 counties in North Dakota

The Storm Prediction Center issued this mesoscale discussion at Jul 28, 2012, 2:56 PM MDT for 4 counties in Montana; 5 counties in North Dakota. It was in force for 64 min.

The area

The outline as issued.

The facts

Issued: Jul 28, 2012, 2:56 PM MDT (20:56 UTC)
Expired: Jul 28, 2012, 4:00 PM MDT
In force: 64 min
Issued by: the Storm Prediction Center
Chance of a watch: 40%

Counties Daniels County, MT, Richland County, MT, Roosevelt County, MT, Sheridan County, MT, Burke County, ND, Divide County, ND, McKenzie County, ND, Mountrail County, ND, Williams County, ND

The nearest sounding before it

Glasgow Intl Airport, MT (KGGW), launched 12:00Z, 8.9 hours before the alert went out and 234 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.

Skew-T log-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.

Mixed-layer CAPE: 731 J/kg
Mixed-layer CIN: -239 J/kg
Mixed-layer LCL: 1885 m above ground
0-6 km bulk shear: 19 kt
0-1 km storm-relative helicity: 41 m²/s²
0-3 km storm-relative helicity: 42 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted, in the capitals the NWS used until 2016.

855 
ACUS11 KWNS 282056
SWOMCD
SPC MCD 282056 
NDZ000-MTZ000-282200-

MESOSCALE DISCUSSION 1637
NWS STORM PREDICTION CENTER NORMAN OK
0356 PM CDT SAT JUL 28 2012

AREAS AFFECTED...FAR NERN MT...NWRN ND

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 

VALID 282056Z - 282200Z

PROBABILITY OF WATCH ISSUANCE...40 PERCENT

SUMMARY...A LOCALIZED THREAT FOR STRONG-SVR WIND GUSTS AND HAIL MAY
ACCOMPANY A RIGHT-MOVING SUPERCELL APPROACHING THE CANADIAN BORDER.
IT IS UNCLEAR WHETHER CONVECTIVE COVERAGE WILL BE SUFFICIENT TO
WARRANT A WW...BUT TRENDS WILL BE MONITORED.

DISCUSSION...VISIBLE SATELLITE/RADAR LOOPS SHOW A DISCRETE
RIGHT-MOVING SUPERCELL OVER SRN SK...WITH ADDITIONAL CONVECTIVE
TOWERS FORMING ALONG A TRAILING BOUNDARY TO THE SW. THIS APPEARS TO
HAVE FORMED IN ASSOCIATION WITH A WEAK UPPER IMPULSE EMBEDDED IN
MODERATE WLY FLOW ALOFT...AND IS MOVING ALONG/NEAR A WEAK STATIONARY
BOUNDARY POSITIONED JUST E OF THE ND/MT STATE LINE. DOWNSTREAM
ENVIRONMENT /I.E. OVER FAR NERN MT AND NWRN ND/ REMAINS FAVORABLE
FOR MAINTAINING CONVECTIVE VIGOR WITH CONTINUED S-SEWD
PROGRESSION...WITH SFC DEW POINTS NEAR 60 F SUPPORTING MLCAPE VALUES
NEAR 1500 J/KG. PRIMARY THREATS APPEAR TO BE LOCALIZED STRONG-SVR
WIND GUSTS /OWING TO HOT/WELL-MIXED BOUNDARY LAYER/ AND HAIL /GIVEN
STEEP MIDLEVEL LAPSE RATES AND EFFECTIVE SHEAR NEAR 20 MPH/.
ADDITIONAL CONVECTIVE DEVELOPMENT MAY ALSO OCCUR ON THE WRN FLANK OF
THE TRAILING OUTFLOW BOUNDARY...POTENTIALLY AFFECTING PARTS OF FAR
NERN MT.

..ROGERS/CORFIDI.. 07/28/2012

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

ATTN...WFO...BIS...GGW...

LAT...LON   49010236 48250213 47730236 47470271 47310430 47680543
            48970592 49010236

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jul 28, 1:56 PM MDT	Mesoscale Discussion	SPC	Hill, Liberty, Pondera, Toole	64 min
Jul 28, 2:37 PM MDT	Mesoscale Discussion	SPC	Beaverhead, Broadwater, Carbon, Deer Lodge, Gallatin, Golden Valley and 9 more	53 min

Nearby

Mesoscale Discussions in North Dakota, 2012 Mesoscale Discussions in Montana, 2012 Every mesoscale discussion in 2012

Sources

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.