Saturday, June 6, 2009

MESO: Mesoscale Discussion 0959

ACUS11 KWNS 061544
SWOMCD
SPC MCD 061544
WYZ000-061715-

MESOSCALE DISCUSSION 0959
NWS STORM PREDICTION CENTER NORMAN OK
1044 AM CDT SAT JUN 06 2009

AREAS AFFECTED...NE WY

CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY

VALID 061544Z - 061715Z

THE NEED FOR A WW IS NOT CURRENTLY ANTICIPATED...BUT TRENDS WILL BE
MONITORED FOR THE POSSIBILITY OF AN INCREASING SEVERE THREAT.

WATER VAPOR IMAGERY INDICATES A FAIRLY SIGNIFICANT MID-LEVEL
CIRCULATION IS IN THE PROCESS OF LIFTING OUT OF THE NORTHERN GREAT
BASIN. THIS FEATURE IS EXPECTED TO WEAKEN WITHIN A CONFLUENT REGIME
ACROSS THE NORTHERN ROCKIES INTO THE NORTHERN PLAINS...BUT FORCING
IS EXPECTED TO BE SUFFICIENT TO SUPPORT THUNDERSTORM DEVELOPMENT
ACROSS THE BIG HORNS VICINITY LATE THIS MORNING. LIGHTNING DATA
INDICATES THAT INITIATION IS ALREADY UNDERWAY...AS INHIBITION
WEAKENS WITH HEATING ACROSS THE HIGHER TERRAIN.

STEEP MID-LEVEL LAPSE RATES APPEAR TO BE CONTRIBUTING TO MIXED LAYER
CAPE ON THE ORDER OF 500 J/KG...BUT RUC GUIDANCE SUGGESTS THIS COULD
INCREASE UP TO AROUND 1000 J/KG IN SOUTHEASTERLY UPSLOPE FLOW ACROSS
NORTHEAST WYOMING BY THIS AFTERNOON. GIVEN COOL THERMODYNAMIC
PROFILES...POTENTIAL INSTABILITY...COUPLED WITH FAVORABLE DEEP LAYER
SHEAR BENEATH 40-50+ KT 500 MB FLOW... PROBABLY WILL BE SUFFICIENT
FOR A FEW STRONG/SEVERE STORMS CAPABLE OF PRODUCING AT LEAST
MARGINALLY SEVERE HAIL. THE TENDENCY SHOULD BE FOR ACTIVITY TO
MOVE/PROPAGATE SOUTHEASTWARD ALONG A FRONTAL ZONE ACROSS NORTHEAST
WYOMING...TO THE WEST OF THE BLACK HILLS... BETWEEN NOW AND 18-20Z.

..KERR.. 06/06/2009

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

ATTN...WFO...UNR...CYS...RIW...

LAT...LON 44260710 44580571 43380442 42610478 43060620 43380726
44260710

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