Mesoscale Discussion 1609

Issued

Jul 26, 2012, 2:07 PM MDT (20:07 UTC)

Expired

Jul 26, 2012, 4:00 PM MDT

In force

113 min

Issued by

the Storm Prediction Center

Chance of a watch

5%

The Great Falls radar (KTFX), 125 km from the middle of the area, began a volume at 20:09 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.

423 
ACUS11 KWNS 262008
SWOMCD
SPC MCD 262007
MTZ000-WYZ000-IDZ000-262200-

MESOSCALE DISCUSSION 1609
NWS STORM PREDICTION CENTER NORMAN OK
0307 PM CDT THU JUL 26 2012

AREAS AFFECTED...WRN/CNTRL MT...A SMALL PART OF ERN ID...NWRN WY

CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY

VALID 262007Z - 262200Z

PROBABILITY OF WATCH ISSUANCE...5 PERCENT

SUMMARY...A VERY ISOLATED THREAT FOR SVR THUNDERSTORMS WILL EXIST
INTO THE EVENING HOURS. GIVEN THE VERY LIMITED SPATIAL EXTENT OF ANY
SVR THREAT...WW ISSUANCE IS NOT NEEDED.

DISCUSSION...AN ARC OF MID-LEVEL CLOUDS/EMBEDDED THUNDERSTORMS
ASSOCIATED WITH LOW/MID-LEVEL WAA -- RELATED TO MODEST AMPLIFICATION
OF A RIDGE OVER THE NRN ROCKIES -- EXTENDS FROM NRN ID INTO W-CNTRL
MT. THE WAA MAY SUPPORT ADDITIONAL ISOLATED THUNDERSTORM DEVELOPMENT
DURING THE NEXT FEW HOURS. ISOLATED CONVECTIVE DEVELOPMENT HAS THE
GREATEST CHANCE OF OCCURRING OVER N-CNTRL MT...WHICH WILL EXIST
BENEATH THE NRN FRINGES OF THE RIDGE. MODEST VERTICAL DEVELOPMENT OF
THE CUMULUS FIELD HAS OCCASIONALLY BEEN NOTED IN THIS REGION INVOF
THE ROCKY MOUNTAIN FRONT. FARTHER SOUTH...WARMER TEMPERATURES ALOFT
TOWARD THE CORE OF THE RIDGE MAY SUPPRESS CONVECTIVE DEVELOPMENT AS
EVIDENCED BY THE RELATIVELY FLAT CUMULUS FIELD OVER THE MOUNTAINS.
HOWEVER...AN ISOLATED STORM OR TWO CANNOT BE RULED OUT OWING TO
OROGRAPHIC ASCENT COMBINED WITH ADDITIONAL DIURNAL
HEATING/DESTABILIZATION.

ENHANCED MID-LEVEL FLOW OVER THE NRN FRINGES OF THE AMPLIFYING RIDGE
WILL SUPPORT 25-40 KT OF EFFECTIVE BULK SHEAR...WHICH MAY
CONDITIONALLY SUPPORT ORGANIZED STORM STRUCTURES. HOWEVER...WITH
LIMITED LOW-LEVEL MOISTURE -- I.E. SFC DEWPOINTS IN THE 40S TO
AROUND 50F -- ONLY MARGINAL INSTABILITY WILL BE PRESENT -- I.E.
MLCAPE VALUES GENERALLY FROM 200 TO 800 J/KG. THIS SHOULD INHIBIT
STORM STRENGTH. AND...WITH THE ABSENCE OF STRONGER FORCING FOR
ASCENT...STORM COVERAGE IS EXPECTED TO BE GREATLY LIMITED.

..COHEN/HART.. 07/26/2012

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

ATTN...WFO...BYZ...RIW...TFX...PIH...MSO...

LAT...LON   44701301 46381410 48621496 49011350 48931171 48491027
            46140847 44770899 44181019 44171165 44701301

Mesoscale Discussions in Montana, 2012Mesoscale Discussions in Idaho, 2012Mesoscale Discussions in Wyoming, 2012Every mesoscale discussion in 2012

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.