Alert archive / Montana / Mesoscale Discussions in 2012
Mesoscale Discussion 1634
The Storm Prediction Center issued this mesoscale discussion at Jul 28, 2012, 1:56 PM MDT for 4 counties in Montana. It was in force for 64 min.
The area
The outline as issued.
The facts
- Issued
- Jul 28, 2012, 1:56 PM MDT (19:56 UTC)
- Expired
- Jul 28, 2012, 3:00 PM MDT
- In force
- 64 min
- Issued by
- the Storm Prediction Center
- Chance of a watch
- 20%
Counties Hill County, MT, Liberty County, MT, Pondera County, MT, Toole County, MT
The radar
The Great Falls radar (KTFX), 115 km from the middle of the area, began a volume at 19:56 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, 7.9 hours before the alert went out and 108 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
- 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
The text
As transmitted, in the capitals the NWS used until 2016.
409
ACUS11 KWNS 281956
SWOMCD
SPC MCD 281956
MTZ000-282100-
MESOSCALE DISCUSSION 1634
NWS STORM PREDICTION CENTER NORMAN OK
0256 PM CDT SAT JUL 28 2012
AREAS AFFECTED...PORTIONS NWRN/N-CNTRL MT
CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY
VALID 281956Z - 282100Z
PROBABILITY OF WATCH ISSUANCE...20 PERCENT
SUMMARY...ISOLATED STRONG-SVR TSTMS DEVELOPING IN THE IMMEDIATE LEE
OF THE ROCKIES OF NWRN MT MAY POSE A THREAT FOR DMGG WINDS/HAIL WITH
EWD PROGRESSION OVER THE HIGH PLAINS. SPARSE COVERAGE OF THE THREAT
SHOULD PRECLUDE THE NEED FOR WW.
DISCUSSION...ISOLATED TSTMS HAVE DEVELOPED NEAR A WEAK STATIONARY
BOUNDARY POSITIONED W-E OVER PONDERA/LIBERTY COUNTIES MT...WITH
UPWARD VERTICAL MOTION LIKELY ENHANCED BY GLANCING INFLUENCE OF A
SHORTWAVE UPPER TROUGH MOVING ACROSS ALBERTA. STRONG DIABATIC
HEATING HAS OCCURRED OVER THE HIGH PLAINS BENEATH STEEP MIDLEVEL
LAPSE RATES...RESULTING IN MLCAPE VALUES NEAR 1000 J/KG...DESPITE
MODEST BOUNDARY LAYER MOISTURE /E.G. SFC DEW POINTS IN THE 40S TO
NEAR 50 F/. MODERATELY STRONG MIDLEVEL FLOW /SAMPLED AT 30-40 MPH
PER 12Z RAOBS/ ATOP GRADUALLY VEERING LOW-LEVEL WINDS WILL BE
SUFFICIENT FOR SMALL MULTICELL CLUSTERS OR A FEW
SUPERCELLS...CAPABLE OF PRODUCING LARGE HAIL. ADDITIONALLY...A
LOCALIZED DMGG WIND THREAT MAY ACCOMPANY THESE STORMS GIVEN THE
PRESENCE OF STEEP LOW-LEVEL LAPSE RATES WITHIN A DEEP/WELL-MIXED
BOUNDARY LAYER.
..ROGERS/CORFIDI.. 07/28/2012
...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...
ATTN...WFO...TFX...
LAT...LON 48970925 48460929 48010933 47911134 47871240 48191285
48971284 48970925SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Jul 28, 2:37 PM MDT | Mesoscale Discussion | SPC | Beaverhead, Broadwater, Carbon, Deer Lodge, Gallatin, Golden Valley and 9 more | 53 min |
| Jul 28, 2:56 PM MDT | Mesoscale Discussion | SPC | Daniels, Richland, Roosevelt, Sheridan | 64 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.