Alert archive / Montana / Mesoscale Discussions in 2009
Mesoscale Discussion 331
The Storm Prediction Center issued this mesoscale discussion at Mar 29, 2009, 9:03 PM MDT for 7 counties in Montana; 6 counties in Wyoming. It was in force for 6 hr.
The area
The outline as issued.
The facts
- Issued
- Mar 29, 2009, 9:03 PM MDT (03:03 UTC)
- Expired
- Mar 30, 2009, 3:00 AM MDT
- In force
- 6 hr
- Issued by
- the Storm Prediction Center
Counties Big Horn County, MT, Carbon County, MT, Custer County, MT, Fallon County, MT, Powder River County, MT, Rosebud County, MT, Stillwater County, MT, Big Horn County, WY, Fremont County, WY, Hot Springs County, WY, Johnson County, WY, Sheridan County, WY, Washakie County, WY
The radar
The Billings radar (KBLX), 171 km from the middle of the area, began a volume at 03:03 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
Riverton, WY (KRIW), launched 00:00Z, 3.1 hours before the alert went out and 245 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
- 2739 m above ground
- 0-6 km bulk shear
- 64 kt
- 0-1 km storm-relative helicity
- 68 m²/s²
- 0-3 km storm-relative helicity
- 104 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted, in the capitals the NWS used until 2016.
000
ACUS11 KWNS 300304
SWOMCD
SPC MCD 300303
MTZ000-WYZ000-300900-
MESOSCALE DISCUSSION 0331
NWS STORM PREDICTION CENTER NORMAN OK
1003 PM CDT SUN MAR 29 2009
AREAS AFFECTED...NCNTRL/NERN WY AND SERN MT
CONCERNING...HEAVY SNOW
VALID 300303Z - 300900Z
H7 LOW APPEARS TO BE GRADUALLY REFORMING/DEVELOPING SEWD FROM ALONG
THE MT/WY BORDER INTO NERN WY LATE THIS EVENING. DEEP LAYER FLOW
HAS TURNED MORE NELY ACROSS SERN MT AND SHOULD DO SO ACROSS NERN WY
THROUGH THE NEXT SVRL HOURS. UPSLOPE ENHANCED SNOWFALL HAS BEEN IN
PROGRESS ACROSS THE BIG HORNS OF MT MOST OF THIS EVENING. SNOW
RATES SHOULD INCREASE FARTHER SOUTH ACROSS THE BIG HORNS IN WY
BETWEEN 06-08Z. MEANWHILE...COLD AIR HAS CURLED SWD THROUGH THE BIG
HORN BASIN AND SNOWFALL RATES WILL ALSO INCREASE ACROSS THE ERN/NRN
SLOPES OF THE WIND RIVER AND OWL MOUNTAINS RANGES...FOR AT LEAST A
FEW HOURS THIS EVENING.
IN ADDITION TO THE UPSLOPE ENHANCED SNOWFALL RATES OF 1-2 INCHES PER
HOUR...MODEST H7-H5 FRONTOGENETICAL FORCING WILL FOCUS A PROLONGED
HEAVY SNOWBAND EXTENDING FROM THE BIG HORNS NEWD ACROSS SRN
ROSEBUD...POWDER RIVER...CARTER...SRN CUSTER AND SRN FALLON COUNTIES
IN SERN MT THROUGH 12Z. THIS BAND SHOULD RELAX AND REDEVELOP
FARTHER E IN SD/ND AS THE MID-LVL LOW CONTINUES TO TRANSLATE EWD
BEYOND THE BLACK HILLS.
IN ADDITION TO THE FALLING SNOW...CONSIDERABLE BLOWING SNOW
/BLIZZARD CONDITIONS/ WILL EVOLVE SEWD WITH TIME AS THE PRESSURE
GRADIENT TIGHTENS ALONG THE BACKSIDE OF THE MID-LVL SYSTEM.
..RACY.. 03/30/2009
...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...
ATTN...WFO...BYZ...RIW...
LAT...LON 42810879 44280927 45640969 46060762 46430599 46580427
46170411 45590425 45050627 44680651 43440626 42810879SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Mar 30, 5:36 AM MDT | Mesoscale Discussion | SPC | Crook | 4 hr |
Nearby
Mesoscale Discussions in Montana, 2009Mesoscale Discussions in Wyoming, 2009Every mesoscale discussion in 2009
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.