Alert archive / Montana / Mesoscale Discussions in 2012

Mesoscale Discussion 1636

July 28, 201215 counties in Montana

The Storm Prediction Center issued this mesoscale discussion at Jul 28, 2012, 2:37 PM MDT for 15 counties in Montana. It was in force for 53 min.

The area

The outline as issued.

The facts

Issued
Jul 28, 2012, 2:37 PM MDT (20:37 UTC)
Expired
Jul 28, 2012, 3:30 PM MDT
In force
53 min
Issued by
the Storm Prediction Center
Chance of a watch
40%

Counties Beaverhead County, MT, Broadwater County, MT, Carbon County, MT, Deer Lodge County, MT, Gallatin County, MT, Golden Valley County, MT, Jefferson County, MT, Madison County, MT, Meagher County, MT, Park County, MT, Silver Bow County, MT, Stillwater County, MT, Sweet Grass County, MT, Wheatland County, MT, Yellowstone County, MT

The radar

The Billings radar (KBLX), 167 km from the middle of the area, began a volume at 20:39 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.

The nearest sounding before it

Great_falls, MT (KTFX), launched 12:00Z, 8.6 hours before the alert went out and 205 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-pSkew-T log-p diagram, Great_falls, MT at 12:00Z on 2012-07-28Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 0 joules per kilogram.LCL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Great_falls, MT at 12:00Z on 2012-07-28The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 111 square meters per square second.19395878Sfc1 km3 km6 km9 kmRMLM
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
0 J/kg
Mixed-layer CIN
No buoyant parcel
Mixed-layer LCL
2277 m above ground
0-6 km bulk shear
23 kt
0-1 km storm-relative helicity
111 m²/s²
0-3 km storm-relative helicity
130 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.

267 
ACUS11 KWNS 282038
SWOMCD
SPC MCD 282037
MTZ000-282130-

MESOSCALE DISCUSSION 1636
NWS STORM PREDICTION CENTER NORMAN OK
0337 PM CDT SAT JUL 28 2012

AREAS AFFECTED...SWRN/S-CNTRL MT

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

VALID 282037Z - 282130Z

PROBABILITY OF WATCH ISSUANCE...40 PERCENT

SUMMARY...INCREASING ASCENT ACCOMPANYING AN UPPER IMPULSE OVER THE
GREAT BASIN SHOULD RESULT IN EXPANDING AREAL COVERAGE OF TSTMS THIS
AFTERNOON ACROSS SWRN/S-CNTRL MT. THE POTENTIAL FOR A FEW CLUSTERS
CAPABLE OF PRODUCING STRONG-SVR WIND GUSTS AND HAIL WILL EXIST...AND
COULD REQUIRE ISSUANCE OF A WW.

DISCUSSION...WATER VAPOR LOOP SHOWS A BAND OF MID/UPPER LEVEL ASCENT
OVERSPREADING PARTS OF FAR SWRN MT AND E-CNTRL ID...AHEAD OF AN
UPPER IMPULSE OVER THE WRN GREAT BASIN. TOWERING CU/CB FIELD HAS
BECOME MORE PROMINENT WITHIN THE PAST 1-2 HRS ACROSS THIS AREA AS
TEMPERATURES HAVE WARMED INTO THE 80S F...WITH DEVELOPMENT PRIMARILY
FOCUSED OVER MTN RANGES/HIGHER TERRAIN. WITH TIME...EXPANDING
COVERAGE/CONSOLIDATION OF TSTMS INTO A FEW CLUSTERS MAY OCCUR. THE
PRIMARY LIMITING FACTOR APPEARS TO BE MEAGER BOUNDARY LAYER
MOISTURE...WITH SFC DEW POINTS FALLING INTO THE LOW 40S ACROSS MUCH
OF S-CNTRL MT AS THE BOUNDARY LAYER HAS BECOME WELL-MIXED...YIELDING
MARGINAL MLCAPE VALUES OF 500-1000 J/KG. HOWEVER...MODERATELY STRONG
MIDLEVEL FLOW /YIELDING EFFECTIVE SHEAR VALUES NEAR 40 MPH/ WILL
STILL BE SUPPORTIVE FOR MULTICELL TO OCCASIONAL SUPERCELL CONVECTIVE
MODES...WITH AN ACCOMPANYING THREAT FOR STRONG-SVR WINDS AND HAIL.
CONVECTIVE TRENDS WILL BE MONITORED FOR POSSIBLE WW ISSUANCE.

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

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

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

LAT...LON   45050862 45050957 45041101 44781181 44661269 44861308
            45401371 46271310 46531299 46781154 46940951 46840866
            45770797 45280815 45050862

SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Jul 28, 1:56 PM MDTMesoscale DiscussionSPCHill, Liberty, Pondera, Toole64 min
Jul 28, 2:56 PM MDTMesoscale DiscussionSPCDaniels, Richland, Roosevelt, Sheridan64 min

Nearby

Mesoscale Discussions in Montana, 2012Every 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; radar from the NEXRAD Level II archive.