Alert archive / Montana / Mesoscale Discussions in 2021
Mesoscale Discussion 1325
The Storm Prediction Center issued this mesoscale discussion at Jul 21, 2021, 2:40 PM MDT for 14 counties in Montana. It was in force for 95 min.
The area
The outline as issued.
The facts
- Issued
- Jul 21, 2021, 2:40 PM MDT (20:40 UTC)
- Expired
- Jul 21, 2021, 4:15 PM MDT
- In force
- 95 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch unlikely
- Chance of a watch
- 20%
Counties Deer Lodge County, MT, Flathead County, MT, Glacier County, MT, Granite County, MT, Jefferson County, MT, Lake County, MT, Lewis and Clark County, MT, Mineral County, MT, Missoula County, MT, Pondera County, MT, Powell County, MT, Ravalli County, MT, Silver Bow County, MT, Teton County, MT
The radar
The Missoula radar (KMSX), 24 km from the middle of the area, began a volume at 20:42 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, 8.7 hours before the alert went out and 251 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
- 158 J/kg
- Mixed-layer CIN
- -180 J/kg
- Mixed-layer LCL
- 1952 m above ground
- 0-6 km bulk shear
- 23 kt
- 0-1 km storm-relative helicity
- 27 m²/s²
- 0-3 km storm-relative helicity
- 33 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
639 ACUS11 KWNS 212041 SWOMCD SPC MCD 212040 MTZ000-IDZ000-212215- Mesoscale Discussion 1325 NWS Storm Prediction Center Norman OK 0340 PM CDT Wed Jul 21 2021 Areas affected...Western Montana and Northeast Idaho Concerning...Severe potential...Watch unlikely Valid 212040Z - 212215Z Probability of Watch Issuance...20 percent SUMMARY...Convective initiation occurring amid an environment conducing to support a damaging wind and severe hail threat. Watch issuance unlikely at this time. DISCUSSION...Regional satellite shows a broad area of cumulus development over portions of western Montana, likely in association with ascent from a mid-level short-wave trough entering the region, as evidenced in water vapor imagery. Additionally, strong heating in the wake of mid- and high-level clouds/smoke has allowed surface temperatures to warm into the mid 80s F, producing strong low-level lapse rates amid rich low-level moisture, characterized by dew point temperatures in the mid 50s F. These conditions, along with moderate mid-level lapse rates and cool mid-level temperatures (evident in an 18z sounding from southwest MT) have led to sufficient destabilization for convective initiation, with MLCAPE near 1000 J/kg. The aforementioned short-wave is embedded within marginally enhanced southwesterly mid-level flow, sufficient to produce 35-40 kt of effective bulk shear. Current expectation is for storms to become more numerous in the next 1-2 hours. Given the aforementioned thermodynamic and kinematic conditions, storms may become organized enough to produce damaging winds and severe hail in the strongest cells. At this time, it does not appear that storm coverage will be expansive enough to warrant watch issuance. However, convective trends will continue to be monitored. ..Karstens/Hart.. 07/21/2021 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...TFX...MSO...OTX... LAT...LON 45431533 47411516 48941341 48411194 45591165 45431533
Nearby
Mesoscale Discussions in Montana, 2021Every mesoscale discussion in 2021
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.