FXUS65 KRIW 050529
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1030 PM MST SAT FEB 4 2012

.SHORT TERM...TONIGHT THROUGH TUESDAY

WITH AN UPPER LEVEL LOW OVER THE GREAT BASIN AND A HIGH PRESSURE
RIDGE EXTENDING FROM THE PACIFIC NORTHWEST INTO SOUTHWEST CANADA
WILL CONTINUE TO PRODUCE RATHER UNUSUAL EASTERLY FLOW OVER THE
WESTERN AND CENTRAL WYOMING WITH DRY AND COOL CONDITIONS TONIGHT
THROUGH MONDAY...WITH RATHER LIGHT WINDS. SOME HIGH CLOUDS WILL
MOVE ACROSS THE SOUTHERN AND CENTRAL AREAS IN THE EASTERLY FLOW.
SOME LOW STRATUS AND FOG WILL BE POSSIBLE IN THE RIVER VALLEYS
LATE AT NIGHT AND THROUGH THE MORNING HOURS. THE UPPER LOW WILL
MOVE NORTH AS A CANADIAN COLD FRONT MOVES SOUGH MONDAY NIGHT AND
TUESDAY BRINGING A THREAT OF VERY LIGHT SNOW TO NORTHERN...EASTER
AND CENTRAL AREAS. AT THIS TIME ACCUMULATIONS LOOK TO BE WELL
UNDER AN INCH...BUT TEMPERATURES SHOULD COOL AND MORE STRATUS
CLOUDS SHOULD BE AROUND.

.LONG TERM...TUESDAY NIGHT THROUGH SATURDAY

THE GFS AND THE ECMWF BRING A NORTHERN STREAM CLIPPER TYPE SYSTEM
THROUGH THE AREA WITHOUT ANY FANFARE TUESDAY NIGHT. THEN THE HIGH
AMPLITUDE RIDGE OVER THE FAR WEST WILL KEEP CONDITIONS DRY WITH
STRONG NOCTURNAL VALLEY AND BASIN INVERSIONS THROUGH AT LEAST
THURSDAY. STILL NEED TO WAIT AND SEE HOW THE MODELS HANDLE THIS
NARROW RIDGE BECAUSE A SWAY IN EITHER DIRECTION COULD DETERMINE
WHETHER OR NOT ANY POTENTIAL ARCTIC OUTBREAKS COULD DIVE SOUTH
TOWARD WYOMING ON THE EAST SIDE OF THE RIDGE. SEVERAL DAYS AGO THE
MODELS HAD A HARD TIME DETERMINING HOW FAR EAST OR WEST THE OMEGA
BLOCK PRESENTLY OVER THE AREA WOULD SET UP SO WILL WATCH FOR MODEL
TRENDS FOR THE POSITIONING OF THE AFOREMENTIONED RIDGE DURING THE
NEXT SEVERAL RUNS. SOUTHWEST WINDS WILL BEGIN TO INCREASE ALONG THE
SOUTHERN WIND CORRIDOR TOWARD THE END OF THE WEEK AS THE PATTERN
BECOMES LESS BLOCKY AND A MORE PROGRESSIVE FLOW PATTERN ENSUES.

&&

.AVIATION.../06Z ISSUANCE/

UPPER HIGH PRESSURE OVER MONTANA AND UPPER LEVEL LOW PRESSURE OVER
THE GREAT BASIN WILL KEEP A DRY EASTERLY FLOW OVER THE AREA TODAY.
SOME PATCHY VALLEY FOG WILL RESULT IN PARTIAL TERRAIN
OBSCURATIONS...LOCAL IFR CONDITIONS DURING THE MORNING IN THE
WESTERN VALLEYS AND WIND RIVER BASIN OR VCNTY
KJAC...KBPI...KRKS...KLND. OTHERWISE MAINLY FEW-SCT150 MSL AND SOME
HIGHER CLOUDS WILL ROTATE WESTWARD ACROSS SOUTHERN AND CENTRAL
WYOMING. WINDS WILL REMAIN LIGHT...10 KNOTS OR LESS AT ALL
TERMINALS. A WEAK CANADIAN COLD FRONT WILL PUSH SOUTH ACROSS THE
MONTANA/WYOMING BORDER 09Z-12Z MONDAY BUT LOWER CLOUDS WILL STAY
NORTH OF THE BORDER THROUGH 12Z.

&&

.FIRE WEATHER...

WITH AN UPPER LEVEL LOW OVER THE GREAT BASIN AND A HIGH PRESSURE
RIDGE EXTENDING FROM THE PACIFIC NORTHWEST INTO SOUTHWEST CANADA
WILL CONTINUE TO PRODUCE RATHER UNUSUAL EASTERLY FLOW OVER THE
WESTERN AND CENTRAL WYOMING WITH DRY AND COOL CONDITIONS TONIGHT
THROUGH MONDAY...WITH RATHER LIGHT WINDS AND LOW MIXING HEIGHTS
FOR POOR SMOKE DISPERSAL.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...C.BAKER
LONG TERM...LIPSON
AVIATION...AEM
FIRE WEATHER...C.BAKER







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