Alert archive / Montana / Mesoscale Discussions in 2011

Mesoscale Discussion 1663

July 19, 20119 counties in Montana

The Storm Prediction Center issued this mesoscale discussion at Jul 19, 2011, 2:49 PM MDT for 9 counties in Montana. It was in force for 86 min.

The area

The outline as issued.

The facts

Issued
Jul 19, 2011, 2:49 PM MDT (20:49 UTC)
Expired
Jul 19, 2011, 4:15 PM MDT
In force
86 min
Issued by
the Storm Prediction Center

Counties Blaine County, MT, Cascade County, MT, Chouteau County, MT, Fergus County, MT, Hill County, MT, Judith Basin County, MT, Liberty County, MT, Petroleum County, MT, Phillips County, MT

The radar

The Great Falls radar (KTFX), 149 km from the middle of the area, began a volume at 20:50 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, 8.8 hours before the alert went out and 98 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 2011-07-19Temperature 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 2011-07-19The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 46 square meters per square second.1939587897Sfc1 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
3005 m above ground
0-6 km bulk shear
32 kt
0-1 km storm-relative helicity
46 m²/s²
0-3 km storm-relative helicity
197 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.

652 
ACUS11 KWNS 192049
SWOMCD
SPC MCD 192049 
MTZ000-192215-

MESOSCALE DISCUSSION 1663
NWS STORM PREDICTION CENTER NORMAN OK
0349 PM CDT TUE JUL 19 2011

AREAS AFFECTED...CNTRL THROUGH N-CNTRL MT

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 

VALID 192049Z - 192215Z

ISOLATED DOWNBURST WINDS WILL BE POSSIBLE INTO THE EARLY TO MIDDLE
EVENING AS STORMS INCREASE ACROSS CNTRL MT. WW ISSUANCE IS POSSIBLE
BUT NOT LIKELY GIVEN THAT COVERAGE OF SEVERE EVENTS IS EXPECTED TO
REMAIN SOMEWHAT ISOLATED.

OROGRAPHIC FORCING EMBEDDED WITHIN ZONE OF DEEPER ASCENT ASSOCIATED
WITH PROGRESSIVE SHORTWAVE TROUGH MOVING INTO THE NRN ROCKIES WILL
LIKELY SUPPORT ADDITIONAL STORMS DEVELOPING FROM W-CNTRL THROUGH
CNTRL MT INTO THE EVENING. DEEPLY MIXED BOUNDARY LAYERS WITH STEEP
LAPSE RATES...TEMPERATURE-DEWPOINT SPREADS AROUND 50F AND MLCAPE AOB
1000 J/KG IS SUPPORTING HIGH BASED STORMS THAT WILL LIKELY DEVELOP
UPDRAFT ROTATION GIVEN 40-50 KT EFFECTIVE SHEAR. THIS ENVIRONMENT
WILL SUPPORT POTENTIAL FOR DOWNBURSTS AND AT LEAST MARGINALLY SEVERE
HAIL. OVERALL THREAT APPEARS SOMEWHAT LIMITED BY A RELATIVELY
SHALLOW CAPE LAYER WITH MODEST INSTABILITY...AND COVERAGE OF SEVERE
EVENTS IS EXPECTED TO REMAIN ISOLATED.

..DIAL.. 07/19/2011

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

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

LAT...LON   48920876 48620730 47110782 46391043 47311222 48621156
            48920876

Nearby

Mesoscale Discussions in Montana, 2011Every mesoscale discussion in 2011

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.