MESO: Mesoscale Discussion 2325

ACUS11 KWNS 111638
SWOMCD
SPC MCD 111638
WYZ000-MTZ000-IDZ000-112045-

MESOSCALE DISCUSSION 2325
NWS STORM PREDICTION CENTER NORMAN OK
1138 AM CDT SAT OCT 11 2008

AREAS AFFECTED...PORTIONS OF WY/S CNTRL MT

CONCERNING...HEAVY SNOW

VALID 111638Z - 112045Z

MDT TO HVY SNOW EXPECTED TO CONTINUE ACROSS PORTIONS OF WY/MT NEAR
THE BIGHORN BASIN OVER THE NEXT FEW HRS. BY THE 18-20Z TIME FRAME
SNOWFALL RATES/ACCUMULATIONS WILL RAPIDLY INCREASE...WITH 3 IN/HR
RATES POSSIBLE THEREAFTER. WINDS WILL ALSO INCREASE THROUGH THE
DAY...WITH SUSTAINED SPEEDS NEAR 25 TO 35 MPH WITH HIGHER
GUSTS...SUBSTANTIALLY REDUCING VISIBILITIES IN BLOWING SNOW.

AN UNSEASONABLY STRONG UPPER LOW AND POLAR JET MAX WILL CONTINUE TO
STRENGTHEN AND LIFT NEWD. AS THIS OCCURS...PORTIONS OF WY/MT WILL
REMAIN UNDER STRONG UPPER DIVERGENCE...WHICH WILL CONTRIBUTE TO
INTENSIFYING UPWARD VERTICAL MOTION. FURTHERMORE...MOISTURE FROM
HURRICANE NORBERT IS QUICKLY BEING ADVECTED NWD...EVIDENCED IN GOES
PWAT IMAGERY. AS ISENTROPIC LIFT INCREASES THROUGH THE
DAY...AFOREMENTIONED UPPER DIVERGENCE AND MOISTURE WILL CONTRIBUTE
TO INTENSIFYING SNOWFALL RATES AT TIMES GREATER THAN OR EQUAL 3
INCHES...AND LARGE ACCUMULATIONS OF SNOW...ESPECIALLY OVER AND EAST
OF THE HIGHER TERRAIN OF THE BIG HORN...ABSAROKA...AND WIND RIVER
MOUNTAINS WHERE UPSLOPE WILL CONTRIBUTE TO VERTICAL MOTION.
HOWEVER...GIVEN SUBFREEZING TEMPERATURES...EVEN LOWER VALLEYS WILL
RECEIVE SIGNIFICANT ACCUMULATIONS.

FARTHER S OF THESE AREAS IN SWRN/S CNTRL WY AND NERN UT...HEAVY
SNOWFALL WITH RATES OF 2-3 INCHES AN HOUR MAY BE POSSIBLE BY
AFTERNOON AS INSTABILITY INCREASES...ALONG WITH THE POTENTIAL FOR
CONVECTIVE SNOW/THUNDERSNOW.

..HURLBUT.. 10/11/2008

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

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

42230835 41860991 42891087 43991121 45271099 45640982
45640806 44790696 43210700 42520755

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