Alert archive / Montana / Mesoscale Discussions in 2009

Mesoscale Discussion 620

April 28, 20095 counties in Montana

The Storm Prediction Center issued this mesoscale discussion at Apr 28, 2009, 5:45 PM MDT for 5 counties in Montana. It was in force for 3 hr.

The area

The outline as issued.

The facts

Issued: Apr 28, 2009, 5:45 PM MDT (23:45 UTC)
Expired: Apr 28, 2009, 8:45 PM MDT
In force: 3 hr
Issued by: the Storm Prediction Center

Counties Glacier County, MT, Liberty County, MT, Pondera County, MT, Teton County, MT, Toole County, MT

The radar

The Great Falls radar (KTFX), 94 km from the middle of the area, began a volume at 23:44 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, 11.8 hours before the alert went out and 320 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-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

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: 1253 m above ground
0-6 km bulk shear: 34 kt
0-1 km storm-relative helicity: 141 m²/s²
0-3 km storm-relative helicity: 185 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.

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SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Apr 28, 4:45 PM MDT	Mesoscale Discussion	SPC	Powder River	3 hr

Nearby

Mesoscale Discussions in Montana, 2009 Every 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.