Area Forecast Discussion
Issued by NWS Riverton, WY

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FXUS65 KRIW 270541
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1138 PM MDT SUN OCT 26 2014

UPDATE...UPDATED TO ADD 06Z AVIATION DISCUSSION

.SHORT TERM...TONIGHT THROUGH MONDAY

THE WAVE OF LOW PRESSURE CONTINUES TO MOVE THROUGH THE STATE TODAY.
SHOWERS WILL SPREAD ACROSS THE AREA...ESPECIALLY IMPACTING WESTERN
AND NORTHERN WYOMING. SNOWFALL WILL BE PRESENT...WITH THE BEST
ACCUMULATIONS ANTICIPATED OVER THE WESTERN MOUNTAINS.

THE CORE OF THE LOW PRESSURE WILL MOVE GENERALLY EAST OF THE
FORECAST AREA BY LATE MONDAY MORNING...DRAGGING ITS AXIS BEHIND IT.
COLDER TEMPERATURES WILL BE PREVALENT ACROSS THE AREA ON MONDAY AS
THIS SYSTEM USHERS IN COLDER H7 TEMPERATURES. THE AXIS OF THE TROUGH
WILL SLIDE THROUGH THE FORECAST AREA BY MONDAY EVENING...WITH
BUILDING NORTHWEST FLOW EXPECTED TO FOLLOW IN ITS WAKE.

THE BUILDING NORTHWEST FLOW MONDAY AFTERNOON WILL WORK TO WEAKEN
SHOWER COVERAGE ACROSS THE FORECAST AREA...WITH MOST SHOWERS ONLY
LINGERING OVER THE HIGHER ELEVATIONS AND PORTIONS OF EASTERN
WYOMING.

.LONG TERM...MONDAY NIGHT THROUGH SUNDAY

THE GLOBAL MODELS ARE ACTUALLY IN PRETTY GOOD AGREEMENT ON THE LONG
WAVE PATTERN THROUGH THE FORECAST PERIOD. THE UPPER LEVEL PATTERN
WILL TREND TOWARD MORE AMPLIFIED FLOW. USUALLY THIS FAR OUT THERE
ARE AT LEAST SOME PHASING DIFFERENCES BUT THERE IS SOME DECENT
AGREEMENT TODAY.

OUR FIRST COOL AND UNSETTLED TROUGH WILL BE MOVING THROUGH AT THE
BEGINNING OF THE PERIOD WITH SWIFT ZONAL FLOW CONTINUING ACROSS THE
AREA. SOME MODERATION OF THE AIRMASS BEGINS AS THE RIDGE TO OUR
SOUTH BEGINS TO REPLACE THE EXITING TROUGH. THE FLOW WILL BEGIN TO
AMPLIFY AS A COLD CORE ARCTIC LOW DIVES SOUTHEAST INTO THIS TROUGH
MID WEEK AS IT MOVES INTO NEW ENGLAND. FURTHER WEST...A RAPIDLY
DEEPENING LOW OVER THE GULF OF ALASKA SUPERCHARGED BY THE LEFT EXIT
REGION OF A 150KT JET...EVENTUALLY IT EVOLVES INTO AN OPEN WAVE THAT
DIGS ALONG THE WESTERN CONUS. IN RESPONSE...THE RIDGE TO OUR SOUTH
WILL AMPLIFY AND TAKE OVER OUR SENSIBLE WEATHER THURSDAY THROUGH
SATURDAY WITH WARM AND DRY CONDITIONS EXPECTED. THERE COULD BE A
PERIOD OF GUSTY SOUTHWEST FLOW AS THE WESTERN TROUGH
APPROACHES...ESPECIALLY ON SATURDAY AHEAD OF THE NEXT COLD FRONT. IF
THIS NEXT SYSTEM DIGS AS MUCH AS THE CURRENT MODELS ADVERTISE THERE
COULD BE SOME SNOW AS LOW AS 5KFT ON SUNDAY AND SUNDAY NIGHT.

FOR HALLOWEEN ON FRIDAY...IT LOOKS WARM BUT BREEZY FOR MUCH OF
THE AREA. STRONGEST WINDS WILL BE BETWEEN ROCK SPRINGS AND CASPER
AND AS FAR WEST AS SHOSHONI AROUND TRICK OR TREAT TIME WITH
SOUTH/SOUTHWEST WINDS OF 15 TO 25 MPH EXPECTED....THE OCCASIONAL
GUST TO 40 MPH IS POSSIBLE IN FAVORED AREAS. SO DEFINITELY BREEZY
ENOUGH TO MAKE YOUR SUPERHERO CAPE LOOK COOL BUT NOT STRONG ENOUGH
TO BLOW IT INTO SOUTH DAKOTA.

&&

.AVIATION.../06Z DISCUSSION/

WEST OF THE DIVIDE KBPI/KJAC/KPNA/KRKS ROUTES
SNOW SHOWERS WERE DECREASING ACROSS THE WEST AT 06Z WITH SOME BANDS
OF -SHRA REMAINING PRIMARILY VCNTY KJAC FROM TETON TO TOGWOTEE
PASS.  ISOLD TO SCT -SHSN WILL LINGER OVER THE AREA THROUGH MID TO
LATE MORNING WITH HIGHER MTN OBSCURATIONS AND AREAS OF MVFR
CIGS...ESPECIALLY VCNTY KJAC-KDUB OVER TOGWOTEE PASS.  SUBSIDENCE
AND DRYING WILL RESULT IN CLEARING ACROSS THE AREA MONDAY AFTERNOON
ALONG WITH W-NW WINDS 15-25KT ACROSS THE INTERSTATE 80.  WINDS WILL
DIMINISH MONDAY EVENING WITH VFR CONDITIONS PREVAILING THROUGH 12Z
TUESDAY.

EAST OF THE DIVIDE...KCPR/KCOD/KLND/KRIW/KWRL ROUTES

ISOLD TO SCT -SHSN...MORE NUMEROUS OVER THE BIGHORN RANGE...WILL BE
ENCOUNTERED ALONG AND N-E OF A VCNTY KCOD-KWRL-KCPR LINE THROUGH 15Z
ALONG WITH LCL MVFR CONDITIONS...WHILE THE BIGHORN RANGE AND THE
DIVIDE REMAIN FQTLY OBSCURED.  RAPID CLEARING FROM W-E WILL OCCUR
LATE MONDAY MORNING/MONDAY AFTERNOON WITH W-NW WINDS AT 10-20KTS
PERSISTING VCNTY AND E OF A KBYG-KRIW LINE THROUGH THE AFTERNOON.
DIMINISHING WIND AND VFR...SKC-SCT250...CONDITIONS WILL FOLLOW
MONDAY NIGHT.

&&

.FIRE WEATHER...

A TROUGH OF LOW PRESSURE CONTINUES TO SLIDE THROUGH WESTERN AND
CENTRAL WYOMING TODAY. THIS SYSTEM WILL CONTINUE TO SPREAD SHOWER
ACTIVITY ACROSS WESTERN AND NORTHERN WYOMING. AS THE AXIS OF THE
TROUGH SLIDES THROUGH THE STATE TONIGHT AND TOMORROW
MORNING...EXPECT MUCH COOLER TEMPERATURES...WITH INCREASING
HUMIDITY. WITH THE ANTICIPATION OF SOME PRECIPITATION ACROSS
AREAS...FIRE WEATHER CONCERNS WILL BE MUTED THROUGH MONDAY.

&&

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

$$

SHORT TERM...BRANHAM
LONG TERM...ALLEN
AVIATION...AEM
FIRE WEATHER...BRANHAM








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