Area Forecast Discussion
Issued by NWS Riverton, WY

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000
FXUS65 KRIW 311711
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1111 AM MDT SUN AUG 31 2014

.SHORT TERM...TODAY THROUGH TUESDAY NIGHT

SHOWERS AND STORMS ONGOING AS A DYNAMIC TROUGH CONTINUES TO MOVE
THROUGH THE REGION. A COLD FRONT MOVED THROUGH ON SATURDAY WITH
ANOTHER REINFORCING COLD FRONT MOVING THROUGH FROM NORTHWEST TO
SOUTHEAST DURING THE MORNING HOURS...IT WILL BE COLD ENOUGH FOR SNOW
ABOVE 9KFT BEHIND THIS FRONT ESPECIALLY DURING THE MORNING HOURS.
ELSEWHERE...SCATTERED RAIN SHOWERS WITH EMBEDDED THUNDER THROUGHOUT
THE DAY WITH PERHAPS MORE OF AN EARLY SHOW OUT WEST GIVEN THE
EXPECTED TIMING OF THE TROUGH...HOWEVER THERE WILL BE ANOTHER WAVE
MOVING THROUGH LATE...BRINGING INCREASED SHOWER ACTIVITY BACK INTO
THE NORTHWEST AFTER SUNSET. SO A RATHER COMPLEX TROUGH WITH MANY
PIECES AND PARTS STILL EXPECTED TO AFFECT THE REGION THROUGH
TONIGHT. STRONGER STORMS WITH SMALL HAIL AND GUSTY WINDS WILL BE
MOST PROBABLE ACROSS NATRONA...EASTERN FREMONT AND SWEETWATER
COUNTIES NEAR A FRONTAL BOUNDARY BUT THERE WILL BE LESS CAPE AND
SHEAR TO WORK WITH TODAY SO NO SEVERE STORMS ARE EXPECTED.
OTHERWISE...MOST IF NOT ALL OF THE FORECAST AREA SHOULD SEE ANOTHER
STORM OR TWO BY TONIGHT.

ASIDE FROM THE RAIN CHANCES...IT WILL BE RATHER WINDY AGAIN TODAY AS
THE GRADIENT REMAINS TIGHT AND THUNDERSTORMS WILL STILL SEND OUT
SOME DECENT OUTFLOWS...THOUGH THEY ARE NOT EXPECTED TO BE AS STRONG
AS THEY WERE ON SATURDAY.

LABOR DAY...THE LAST SHORT WAVE THAT COULD STIR UP MORE SHOWERS AND
STORMS MOVES THROUGH EARLY IN THE DAY WITH EVENTUAL CLEARING AS THE
TROUGH CONTINUES TO MOVE EAST. THERE WILL ALSO BE SOME CONTINUED
BREEZY CONDITIONS AS THE SUBSIDENT SIDE OF THE TROUGH SWINGS THROUGH
AND FLOW SHIFTS TO THE NORTHWEST.

MUCH DRIER AIR MOVES IN ON TUESDAY AS FLOW TURNS MORE ZONAL. HIGH
PRESSURE BUILDING IN FROM THE SOUTH WILL ALSO BRING SOME WARMER AIR
WITH TEMPERATURES REBOUNDING BACK INTO THE 80S EAST OF THE DIVIDE.
THERE COULD BE SOME GUSTS TO 30 MPH ACROSS THE SOUTH ON
TUESDAY...WHICH COULD LEAD TO SOME FIRE WEATHER CONCERNS IN AREAS
WITH FLASHY GRASSY FUELS.

.LONG TERM...WEDNESDAY THROUGH SUNDAY

WEDNESDAY WILL BE DRY FOR MOST OF THE REGION. ISOLATED SHOWERS OR
STORMS FOR THE WESTERN MOUNTAINS AND NORTHERN MOUNTAINS. BREEZY
TO WINDY AREAS AND A WARM DAY. ISOLATED SHOWERS AND STORMS OVER
THE NORTH AND NORTHWEST WED NIGHT AS A TROUGH DEVELOPS OVER THE
PACIFIC NW EAST INTO MONTANA. THIS ELONGATED TROUGH WILL BE THE
FOCUS OF THE WEATHER THURSDAY THROUGH SUNDAY PER THE GFS MODEL.
THE ECMWF IS ALSO SHOWING THIS PATTERN THROUGH SATURDAY BUT MOVES
THE SYSTEM OUT FOR NEXT SUNDAY. A COLD FRONT PUSHES SOUTH INTO
NORTHERN WY LATE WED NIGHT AND THEN CONTINUES TO PUSH SOUTH ON
THURSDAY. THE FRONT LIES ALONG THE CONTINENTAL DIVIDE THURSDAY PM
PER THE GFS WHILE THE ECMWF MOVES IT THROUGH THE WHOLE AREA
THURSDAY. THUS THE FORECAST DILEMMA FOR HIGHS ON THURSDAY. PLUS
THE ECMWF IS COLDER WITH TEMPS ALOFT AND NEAR SURFACE TEMPS THAN
THE GFS THURSDAY...AS WELL AS FRIDAY AND SATURDAY. HAVE BLENDED
THE FORECAST HIGHS AND LOWS THURSDAY THROUGH SATURDAY KEEPING THE
BETTER COOLING EAST OF THE DIVIDE. MOISTURE IS FORECAST TO
INCREASE OVER THE REGION THURSDAY THROUGH SATURDAY IN A SW FLOW
ALOFT. MOISTURE SEEMS TO COME FROM TWO SOURCES...ONE FROM THE
TROUGH TO THE NORTH...THE OTHER FROM THE SW U.S. AROUND THE UPPER
HIGH. FOR NOW HAVE THE TYPICAL ISOLATED TO (IN SOME CASES)
SCATTERED SHOWERS AND STORMS OVER THE REGION THURSDAY THROUGH
SATURDAY. THE FRONTAL BOUNDARY WILL ALSO PLAY A ROLE IN THE PRECIP
CHANCE. OVERALL...A COMPLEX PATTERN FOR THOSE THREE DAYS. NEXT
SUNDAY LOOKS LIKE ISOLATED SHOWERS/STORMS AND WARMER HIGHS MOST
PLACES.

&&

.AVIATION.../18Z ISSUANCE/

VFR WILL PREVAIL FOR MOST TERMINALS THROUGH THE FORECAST PERIOD. THE
EXCEPTIONS WILL BE KJAC THROUGH 22Z WITH PERIODS OF MVFR IN LOW CIGS
AND KCOD WITH MVFR IN LOW CIGS AND POSSIBLE VIS RESTRICTIONS
OCCASIONALLY THROUGH 16Z MONDAY. LARGE UPPER LEVEL TROUGH CONTINUES
TO EXPAND ACROSS THE COUNTRY TODAY WITH ANOTHER EMBEDDED DISTURBANCE
MOVING ACROSS WYOMING THIS TODAY...THEN INTO THE HIGH PLAINS BY 00Z
MONDAY...WITH ANOTHER TO FOLLOW BETWEEN 06Z AND 18Z
MONDAY...AFFECTING MAINLY THE NORTHERN FORECAST AREA. ISOLATED TO
SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS WILL CONTINUE ACROSS
CENTRAL AND NORTHERN WYOMING THROUGH 00Z BEFORE BECOMING MORE
ISOLATED IN NATURE FOR MOST LOCATIONS EXCEPT FOR THE NORTHWEST WHICH
WILL REMAIN MORE SCATTERED. YELLOWSTONE NATIONAL PARK TO VCNTY
COD-BYG AND NORTH WILL REMAIN MOST ACTIVE AND MOST LIABLE FOR MVFR
CONDITIONS TO PERSIST. SNOW LEVELS WILL HOVER BETWEEN 9-10KFT IN
ACROSS THE NORTH...WITH MOUNTAIN OBSCURATIONS AND AREAS OF MVFR TO
OCCASIONAL IFR CONDITIONS. THE OTHER AREA OF MORE ORGANIZED
SHRA/ISOLD TSRA COVERAGE IS EXPECTED FROM VCNTY AND NORTH OF A
KJAC-KRIW-KCPR LINE THROUGH THE AFTERNOON AND EARLY EVENING.
HOWEVER...CONDITIONS WILL GENERALLY IMPROVE FROM WEST TO EAST
THROUGH THE AFTERNOON AND EVENING. THERE WILL BE A SLIGHT
POSSIBILITY FOR PATCHY FOG DEVELOPING WHERE BETTER RAINS HAVE FALLEN
ESPECIALLY IN WESTERN/NORTHWESTERN MOUNTAIN/VALLEY LOCATIONS...SUCH
AS NEAR KJAC AFTER 10Z MONDAY. KCOD MAY BE THE MOST LIKELY TO SEE
SOME VIS REDUCTION DUE TO MIST/FOG AS MORE PERSISTENT PRECIPITATION
WILL CONTINUE IN AND AROUND THE AREA OVER A LONGER PERIOD.

&&

.FIRE WEATHER...

SHOWERS AND THUNDERSTORMS WITH A GOOD CHANCE OF WETTING RAIN
POSSIBLE ACROSS THE ENTIRE FORECAST AREA AGAIN TODAY. A COLD FRONT
MOVING THROUGH EARLY THIS MORNING WILL BRING ANOTHER CHANCE FOR SNOW
ABOVE 9KFT IN THE NORTHERN MOUNTAINS. THERE WILL BE A LULL IN THE
ACTIVITY FROM WEST TO EAST THIS AFTERNOON INTO THE EVENING BEFORE
THE NEXT WAVE MOVES IN...HOWEVER THIS WAVE WILL BE LESS IMPACTFUL
WITH ONLY A FEW SHOWERS AND STORMS EXPECTED ACROSS THE NORTHERN
THIRD OF THE STATE. IT WILL BE WINDY AGAIN TODAY...THOUGH NOT AS
GUSTY AS SATURDAY. TEMPERATURES WILL BE LOWER AND HUMIDITY HIGHER
TODAY WITH PLENTY OF CLOUD COVER...SO FIRE DANGER WILL BE LOW. IT
WILL BEGIN TO DRY OUT ON MONDAY...ESPECIALLY ACROSS THE SOUTH...BUT
CONTINUED COOL AND WINDY. MUCH WARMER AND DRIER AIR MOVES IN ON
TUESDAY WITH A STEADY WESTERLY WIND OF 20 TO 30 MPH ACROSS MUCH OF
RAWLINS AND CASPER DISPATCH WITH FIRE WEATHER CONCERNS POSSIBLY
RISING A BIT IF THE RH CAN DROP LOW ENOUGH.

&&

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

&&

$$

SHORT TERM...ALLEN
LONG TERM...AR
AVIATION...JB
FIRE WEATHER...ALLEN










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