FXUS65 KRIW 192106
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
205 PM MST SUN JAN 19 2003

...TODAY THROUGH WEDNESDAY...
WYOMING UNDER NORTHWEST FLOW WITH AC CLOUDS SPILLING INTO WYOMING
OVER THE RIDGE BETWEEN RATHER IMPRESSIVE LOOKING CIRCULATION OFF THE
SOUTHWEST COAST AND LARGE HUDSON BAY LOW.  ANOTHER WINDY DAY FOR ROCK
SPRINGS THROUGH CASPER TODAY AS PRESSURE GRADIENT REMAINS TIGHT OVER
THE AREA. WINDS AT CODY HAVE CALMED DOWN WITH PRESSURE FALLS TO THEIR
WEST WEAKENING THE LEE TROF THAT EXTENDED IN THE BIG HORN BASIN
EARLIER. JOHNSON COUNTY 55 TO 60 DEGREES TODAY.  WEATHER LOOKS FAIRLY
QUIET THROUGH MONDAY WITH THE WIND SLACKING OFF A BIT IN THE WIND
CORRIDOR.  NEXT WEATHER FEATURE STILL WELL OFF THE WEST COAST.  SOME
ENERGY FROM THIS FEATURES SHEARS AWAY AND JOINS A CHUNK OF ENERGY
ROUNDING THE HUDSON LOW.  THIS WILL DROP SOUTH OVER WYOMING TUESDAY
NIGHT BRINGING A CHANCE OF SNOW TO THE WEST MONDAY NIGHT AND TUESDAY.
TRANSITORY RIDGE THEN BUILDS IN WEDNESDAY WITH THE NEXT WAVE ON ITS
HEELS. FORECAST PROBLEM WILL BE EAST OF THE DIVIDE TRYING TO
DETERMINE HOW FAR WEST COLD FRONT WILL PROGRESS. IT WILL HAVE TO
BATTLE WEST TO SOUTHWEST FLOW.  MODELS MAINLY HAVE IT PROGRESSING
AS FAR WEST AS JOHNSON AND NATRONA COUNTIES.  LOOKS GOOD FOR TUESDAY
THOUGH TUESDAY NIGHT AND WEDNESDAY I HAVE GOOD CONFIDENCE IT WILL
MAKE TO THE CONTINENTAL DIVIDE.  BEING JANUARY...FEEL COLD AIR WILL
SLIP RIGHT UNDERNEATH WARMER AIR. MODELS TRYING TO BRING UP SOME LOW
LEVEL MOISTURE IN THE SOUTHEAST FLOW AROUND SURFACE HIGH INTO THE
CWA.  FOR SNOW HAVE CHANCE OF POPS TUESDAY NIGHT IN JOHNSON...NATRONA
AND BIG HORNS.  JOHNSON AND BIG HORNS WEDNESDAY. COLDEST AIR WILL
STAY NORTH AND EAST OF THE AREA...BUT BIG CHANGE ON THE WAY FOR THOSE
IN THE 40S AND 50S TODAY AND TOMORROW.    TWB

...WEDNESDAY NIGHT THROUGH SUNDAY...
THE SAGA REMAINS ON HOW LONG THE COLD AIR WILL HANG AROUND EAST OF
THE DIVIDE. FIRST...WEST OF THE DIVIDE IT WILL REMAIN FAIRLY MILD
THROUGH THE PERIOD. IF THE LONG RANGE MODELS ON TARGET A SERIES OF
WEATHER SYSTEMS WILL MOVE OVER/THROUGH THE MEAN RIDGE IN THE WEST
U.S. AND BRING MOISTURE INTO W/NW WYOMING AT TIMES. THUS POPS IN THE
FORECAST NEARLY EACH DAY WITH THE BEST CHANCE OF POPS IN THE MTNS.
SOUTHWEST ZONES TO REMAIN MOSTLY DRY THROUGH SUNDAY. EAST OF THE
DIVIDE THE FRONTAL BOUNDARY WILL LIKELY MOVE OUT DURING THE DAY
THURSDAY BUT TRY AND MOVE BACK IN THURS NT/FRI AM BEHIND A PASSING WX
SYSTEM. HAVE NOT STRAYED FAR FROM PREVIOUS FORECAST AND WOULD LIKE
TO SHOW CONSISTENT FORECAST TREND UNTIL THIS ARCTIC AIRMASS DECIDES
WHAT COURSE IT WANTS TO TAKE. THE OVERALL WINTER PATTERN SO FAR HAS
BEEN FOR THE COLD AIR TO LAST ONLY A FEW DAYS FOLLOWED BY WARMER AIR
(EXCEPT THE SNOW COVERED BASINS THAT GET TRAPPED IN THE INVERSION).

.RIW...NONE.