Alert archive / Montana / Mesoscale Discussions in 2012
Mesoscale Discussion 1797
The Storm Prediction Center issued this mesoscale discussion at Aug 21, 2012, 1:45 PM PDT for Clearwater County, Idaho County, Lemhi County, Idaho; 14 counties in Montana. It was in force for 2 hr.
The area
The outline as issued.
The facts
- Issued
- Aug 21, 2012, 1:45 PM PDT (20:45 UTC)
- Expired
- Aug 21, 2012, 3:45 PM PDT
- In force
- 2 hr
- Issued by
- the Storm Prediction Center
- Chance of a watch
- 20%
Counties Clearwater County, ID, Idaho County, ID, Lemhi County, ID, Beaverhead County, MT, Broadwater County, MT, Deer Lodge County, MT, Granite County, MT, Jefferson County, MT, Lake County, MT, Lewis and Clark County, MT, Madison County, MT, Mineral County, MT, Missoula County, MT, Powell County, MT, Ravalli County, MT, Sanders County, MT, Silver Bow County, MT
The radar
The Missoula radar (KMSX), 80 km from the middle of the area, began a volume at 20:46 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
Spokane, WA (KOTX), launched 12:00Z, 8.8 hours before the alert went out and 235 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.
- Mixed-layer CAPE
- 0 J/kg
- Mixed-layer CIN
- No buoyant parcel
- Mixed-layer LCL
- 2599 m above ground
- 0-6 km bulk shear
- 7 kt
- 0-1 km storm-relative helicity
- -48 m²/s²
- 0-3 km storm-relative helicity
- -37 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted, in the capitals the NWS used until 2016.
891 ACUS11 KWNS 212046 SWOMCD SPC MCD 212045 MTZ000-IDZ000-212245- MESOSCALE DISCUSSION 1797 NWS STORM PREDICTION CENTER NORMAN OK 0345 PM CDT TUE AUG 21 2012 AREAS AFFECTED...NORTHERN ID/WESTERN MT CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY VALID 212045Z - 212245Z PROBABILITY OF WATCH ISSUANCE...20 PERCENT SUMMARY...ISOLATED DAMAGING WIND AND POSSIBLY SOME SEVERE HAIL POTENTIAL WILL EXIST LATE THIS AFTERNOON/EARLY EVENING FROM PORTIONS OF NORTHERN ID INTO WESTERN MT. DISCUSSION...VISIBLE SATELLITE IMAGERY IS INDICATIVE OF AN INCREASING/DEEPENING CU FIELD...ALONG WITH A FEW ISOLATED TSTMS AS OF 2030Z...ESPECIALLY OVER THE MOUNTAINS/HIGHER TERRAIN OF NORTHERN ID INTO SOUTHWEST MT. IN THE WAKE OF AN INITIAL MID-LEVEL IMPULSE MOVING INTO SOUTHERN ALBERTA...A MORE SUBSTANTIAL TROUGH OVER THE PACIFIC NORTHWEST IS BEGINNING TO INFLUENCE THE REGION PER WATER VAPOR IMAGERY. AS THE BOUNDARY LAYER CONTINUES TO WARM IN THE SHORT-TERM...THE AFOREMENTIONED SCENARIO SHOULD OTHERWISE ENCOURAGE ADDITIONAL TSTM DEVELOPMENT OVER THE NEXT FEW HOURS FROM NORTHERN ID INTO WESTERN MT. THE WELL-MIXED NATURE OF THE BOUNDARY LAYER /30-45 F SFC TEMP-DEWPOINT SPREADS/ AND ASSOCIATED DOWNDRAFT POTENTIAL WILL ACCOUNT FOR THE POSSIBILITY OF ISOLATED DAMAGING WINDS AS FORCING FOR ASCENT/SOUTHWESTERLY WINDS ALOFT CONTINUE TO MARKEDLY INCREASE...A TREND ALREADY NOTED IN REGIONAL WSR-88D VWP DATA. SOME HAIL MAY BE POSSIBLE AS WELL. ..GUYER/MEAD.. 08/21/2012 ...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT... ATTN...WFO...BYZ...TFX...PIH...MSO...BOI...OTX... LAT...LON 45761576 48141578 48041290 46141061 44111343 45761576
Nearby
Mesoscale Discussions in Montana, 2012Mesoscale Discussions in Idaho, 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.