Area Forecast Discussion
Issued by NWS Riverton, WY

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000
FXUS65 KRIW 230925
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
325 AM MDT SAT APR 23 2016

.SHORT TERM...TODAY THROUGH MONDAY NIGHT

A FAIRLY COMPLEX PATTERN SETTING UP ACROSS THE AREA. AN AREA OF LOW
PRESSURE CONTINUES TO MOVE INTO THE INTERMOUNTAIN WEST TODAY. THIS
SYSTEM WILL PUSH MOISTURE ACROSS WESTERN WYOMING THIS MORNING...WITH
ACTIVITY SPREADING TO INCLUDE MUCH OF THE AREA BY THE LATE AFTERNOON
HOURS. INSTABILITY IS APPARENT WITH THE SYSTEM...WITH THE PRESENCE
OF THUNDERSTORMS EXPECTED THIS AFTERNOON. MODELS SHOW THE BEST
INSTABILITY QUICKLY MOVING EAST THIS AFTERNOON...WITH THE BEST LAPSE
RATES MOVING GENERALLY EAST OF THE CONTINENTAL DIVIDE BY THE LATE
AFTERNOON HOURS. REGARDLESS...GUSTY WIND AND SMALL HAIL MAY
ACCOMPANY ANY STORM ACTIVITY TODAY. ADDITIONALLY...AHEAD OF THE
ARRIVAL OF THE BEST MOISTURE PUSH...GRADIENT WIND WILL INCREASE OVER
THE WIND PRONE AREAS THIS AFTERNOON. THIS WILL COMBINE WITH WARM AND
DRY CONDITIONS...LEADING TO THE FAMILIAR CONCERNS WITH ANY
AGRICULTURAL BURNING THIS AFTERNOON.

MEANWHILE...COOLING TEMPERATURES WILL CONVERT SHOWERS TO SNOWFALL
ACROSS THE NORTHWESTERN MOUNTAINS BY THE LATE AFTERNOON TO EARLY
EVENING HOURS. SNOWFALL WILL CONTINUE THROUGH THE OVERNIGHT HOURS AS
THE CORE OF THE LOW PRESSURE SYSTEM MOVES EASTWARD ACROSS CENTRAL
WYOMING. PERIODS OF LIGHT TO MODERATE SNOWFALL WILL CONTINUE ACROSS
THE NORTHWESTERN MOUNTAINS THROUGH SATURDAY NIGHT. THE BEST SNOWFALL
ACCUMULATIONS ARE GENERALLY ABOVE 8000 FT WHERE 5 TO 8 INCHES WILL
BE POSSIBLE. NEWLY OPENED ACCESS POINTS TO YELLOWSTONE MAY BECOME
MESSY WITH EVEN THE 3 TO 4 INCHES ACCUMULATION THROUGH SATURDAY
NIGHT. WITH THESE IMPACTS IN MIND...A WINTER WEATHER ADVISORY HAS
BEEN ISSUED FOR YELLOWSTONE AND THE GRAND TETON AND GROS VENTRE
AREAS BEGINNING THIS EVENING.

THE AREA OF LOW PRESSURE WILL BE OVER EASTERN WYOMING BY EARLY
SUNDAY MORNING...LEAVING COOLER TEMPERATURES AND WRAPAROUND MOISTURE
IN ITS WAKE. THIS MAY RESULT IN INCREASED SNOWFALL OVER THE BIGHORN
MOUNTAINS ON SUNDAY. THIS SCENARIO WILL CONTINUE TO BE MONITORED FOR
ANY NEEDED HIGHLIGHTS. SHOWER ACTIVITY WILL PERSIST ACROSS THE
NORTHERN TWO THIRDS OF THE AREA THROUGH MONDAY MORNING.

ANY BREAK FROM MOISTURE IS EXPECTED TO BE BRIEF AS ANOTHER AREA OF
LOW PRESSURE DIGS INTO THE DESERT SOUTHWEST MONDAY AFTERNOON. THIS
SYSTEM WILL AGAIN SPREAD SHOWER AND ISOLATED THUNDERSTORM ACTIVITY
ACROSS WESTERN WYOMING MONDAY AFTERNOON...WHICH WILL SPREAD TO
INCLUDE THE MAJORITY OF THE AREA BY MONDAY EVENING.

.LONG TERM...TUESDAY THROUGH SATURDAY

THE TUESDAY WEATHER SYSTEM SEEMS TO SPLIT INTO PIECES AS IT MOVES
ACROSS THE ROCKIES. THE NORTHERN PIECE MOVES THROUGH WY WHILE THE
SOUTHERN PIECE MOVES THROUGH SOUTHERN COLORADO. THUS A COOL AND
POTENTIALLY WET DAY ACROSS THE AREA TUESDAY INTO TUESDAY NIGHT.
SOME LOWER ELEVATIONS MAY SEE RAIN TURN TO SNOW TUESDAY NIGHT.
THE ECMWF MODEL IS COLDER THAN THE GFS AS OF THE 00Z RUN. WILL
HAVE TO KEEP AN EYE ON IT. THE WEATHER SYSTEM MOVES OUT WEDNESDAY
WITH LINGERING SHOWERS EXPECTED. THURSDAY LOOKS LIKE SCATTERED
SHOWERS AND ISOLATED STORMS OVER THE WEST AND SOUTHWEST. EAST OF
THE DIVIDE LOOKS MOSTLY DRY AS ONLY ISOLATED SHOWERS THURS PM AND
EVENING. THE NEXT WEATHER SYSTEM WISHES TO TAKE AIM ON THE AREA
FRIDAY INTO SATURDAY. WILL HAVE A CHANCE OF PRECIP BOTH DAYS.
PLENTY OF TIME TO WATCH THIS WEATHER SYSTEM AND ADJUST AS NEEDED.
TEMPS WILL BE ON THE COOL SIDE TUESDAY AND WEDNESDAY. THEN
SLIGHTLYMILDER FOR THURSDAY THROUGH SATURDAY.

&&

.AVIATION.../12Z ISSUANCE/

WEST OF THE CONTINENTAL DIVIDE...KJAC/KRKS/KPNA/KBPI AIRPORTS

AN UPPER LEVEL LOW PRESSURE SYSTEM AND ASSOCIATED COLD FRONT WILL
SPREAD NMRS LOW VFR/MVFR SHRA AND WDLY SCT TSRA TO VCNTY OF THE
CONTINENTAL DIVIDE BY 18Z.  SNOW LEVELS WILL BE INITIALLY NEAR 9KFT
WITH MTN OBSCURATIONS BECOMING WIDESPREAD IN THE AFTERNOON.
WIDESPREAD IFR RASN WITH SNOW LEVELS LOWERING TO NEAR 7KFT ARE
EXPECTED VCNTY AND NORTH OF A KJAC-KDUB LINE BEHIND THE COLD FRONT
AFTER 00Z SUNDAY WITH SCT-NMRS SHRASN SOUTH OF THIS LINE. SNOW
LEVELS WILL LOWER TO MOST VALLEY FLOORS AFTER 06Z SUNDAY WITH SNOW
SHOWERS REMAINING MORE NMRS ACROSS THE NORTHWEST.

EAST OF THE CONTINENTAL DIVIDE...KCPR/KCOD/KRIW/KWRL/KLND AIRPORTS

SOUTH TO SOUTHWEST SFC WINDS WILL INCREASE 16Z-20Z SATURDAY AHEAD OF
AN APPROACHING UPPER LEVEL LOW PRESSURE SYSTEM AND ASSOCIATED COLD
FRONT.  WDLY SCT TSRA/SHRA IS EXPECTED TO SPREAD EAST OF THE DIVIDE
INTO CENTRAL WYOMING 20-22Z SATURDAY WITH MORE ORGANIZED STRONGER
STORMS EXPECTED ALONG AND NORTH OF A FRONTAL BOUNDARY VCNTY WY/MT
LINE. LOWERING CIGS AND INCREASING SHRA ARE EXPECTED THROUGH
SATURDAY NIGHT AS THE UPPER LEVEL LOW PRESSURE SYSTEM MOVES OVER THE
AREA.  SNOW LEVELS WILL LOWER TO BTWN 7-8KFT ACROSS THE 6Z-12Z
SUNDAY WITH MTNS BECOMING MOSTLY OBSCURED...ESPECIALLY THE ABSAROKA
AND BIGHORN RANGES.

&&

.FIRE WEATHER...

WARM...DRY...AND WINDY CONDITIONS WILL BE PRESENT THIS AFTERNOON FOR
AREAS EAST OF THE CONTINENTAL DIVIDE. THE STRONGEST WIND LOOKS TO
IMPACT THE WIND CORRIDOR BETWEEN ROCK SPRINGS AND CASPER. BECAUSE OF
THIS COMBINATION...AGRICULTURAL BURNING IS AGAIN DISCOURAGED THIS
AFTERNOON. OTHERWISE...SHOWERS AND THUNDERSTORMS ARE ANTICIPATED
OVER WESTERN WYOMING TODAY...WITH ACTIVITY SPREADING EAST OF THE
DIVIDE DURING THE LATE AFTERNOON HOURS. THE NORTHWESTERN MOUNTAINS
ARE FAVORABLE TO SEE SIGNIFICANT ACCUMULATING SNOWFALL LATE THIS
EVENING...WHERE A WINTER WEATHER ADVISORY HAS BEEN ISSUED. PERIODS
OF SHOWER ACTIVITY WILL THEN REMAIN IN THE FORECAST THROUGH MONDAY
EVENING AS A SERIES OF LOW PRESSURE SYSTEMS IMPACT THE AREA.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...

WINTER WEATHER ADVISORY FROM 6 PM THIS EVENING TO NOON MDT
SUNDAY FOR WYZ001-012.

&&

$$

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



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