Alert archive / Montana / Mesoscale Discussions in 2007

Mesoscale Discussion 839

May 19, 200710 counties in Montana

The Storm Prediction Center issued this mesoscale discussion at May 19, 2007, 9:04 PM MDT for 10 counties in Montana. It was in force for 56 min.

The area

The outline as issued.

The facts

Issued: May 19, 2007, 9:04 PM MDT (03:04 UTC)
Expired: May 19, 2007, 10:00 PM MDT
In force: 56 min
Issued by: the Storm Prediction Center

Counties Carter County, MT, Custer County, MT, Fergus County, MT, Garfield County, MT, Musselshell County, MT, Petroleum County, MT, Powder River County, MT, Prairie County, MT, Rosebud County, MT, Treasure County, MT

The nearest sounding before it

Glasgow Intl Airport, MT (KGGW), launched 00:00Z, 3.1 hours before the alert went out and 217 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: 1211 m above ground
0-6 km bulk shear: 53 kt
0-1 km storm-relative helicity: 126 m²/s²
0-3 km storm-relative helicity: 243 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.1

Open this sounding in Storm Lab

The text

As transmitted, in the capitals the NWS used until 2016.

000 
ACUS11 KWNS 200304
SWOMCD
SPC MCD 200304 
SDZ000-MTZ000-WYZ000-200400-

MESOSCALE DISCUSSION 0839
NWS STORM PREDICTION CENTER NORMAN OK
1004 PM CDT SAT MAY 19 2007

AREAS AFFECTED...CNTRL AND ERN MT

CONCERNING...SEVERE THUNDERSTORM WATCH 280...

VALID 200304Z - 200400Z

THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 280
CONTINUES.

ISOLATED SEVERE THREAT MAY PERSIST ANOTHER HOUR OR TWO FROM CNTRL
THROUGH SERN MT AND INTO NERN WY. HOWEVER...OVERALL TRENDS ARE FOR
INTENSITIES TO CONTINUE DECREASING. WW 280 WILL BE ALLOWED TO EXPIRE
AT 04Z.

OBJECTIVE ANALYSIS SHOWS AXIS OF MARGINAL INSTABILITY REMAINS OVER
CNTRL MT. WV IMAGERY IMPLIES STRONGER ASCENT ATTENDING NEWD
ADVANCING SHORTWAVE TROUGH IS SHIFTING NE OF THIS REGION TOWARD NERN
MT. THIS ALONG WITH ONSET OF NOCTURNAL COOLING SHOULD LIMIT UPSTREAM
DEVELOPMENT OVER THE HIGHER TERRAIN. EXISTING STORMS ARE SPREADING
NEWD TOWARD NERN MT WHERE COOLER AND DRYER AIR IN POST FRONTAL ZONE
HAS STABILIZED THE ATMOSPHERE. SOME DESTABILIZATION MAY OCCUR OVER
ERN MT AS THE LOW LEVEL JET STRENGTHENS...BUT INSTABILITY IS
EXPECTED TO REMAIN MARGINAL AND ELEVATED IN THIS REGION. STORMS WILL
LIKELY PERSIST THROUGH NERN MT NEXT FEW HOURS AS THE LOW LEVEL JET
STRENGTHENS AND DEEP LAYER ASCENT SHIFTS EWD INTO THIS AREA.
HOWEVER...THE THERMODYNAMIC ENVIRONMENT WILL LIKELY REMAIN TOO
MARGINAL FOR A MORE ROBUST SEVERE THREAT.

..DIAL.. 05/20/2007

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...UNR...BYZ...GGW...TFX...

46020448 44820401 44590486 45840683 46480866 47070966
47990905 47630630

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
May 20, 1:45 PM MDT	Mesoscale Discussion	SPC	Big Horn, Carbon, Carter, Custer, Golden Valley, Musselshell and 7 more	60 min
May 20, 2:33 PM MDT	Severe Thunderstorm Watch	SPC	Big Horn, Carbon, Carter, Custer, Dawson, Fallon and 13 more	9 hr

Nearby

Mesoscale Discussions in Montana, 2007 Every mesoscale discussion in 2007

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.