Area Forecast Discussion
Issued by NWS Riverton, WY

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FXUS65 KRIW 222035
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
235 PM MDT MON SEP 22 2014

.SHORT TERM...TONIGHT AND TUESDAY

DUAL CENTER UPPER LOW IS MOVING NE ACROSS THE AREA EARLY THIS
AFTERNOON WITH A COUPLE BANDS OF SHOWERS AND ISOLATED
THUNDERSTORMS OUT AND ABOUT. THE `OLD` ORIGINAL CIRCULATION IS
NEARING THE ID/MT/WY TRIPLE POINT WHILE THE NEWER CIRCULATION THAT
DEVELOPED OVER THE UPPER GREEN EARLY THIS MORNING HAS BECOME MORE
ORGANIZED AS IT MOVED FROM THE WIND RIVER BASIN INTO THE SRN
BIGHORN BASIN THIS AFTERNOON. THERE WILL CONTINUE TO BE GOOD CHANCE OF
SHOWERS AND A FEW THUNDERSTORMS ALONG THE TRACK INTO EARLY THIS
EVENING BEFORE IMPROVEMENT BEGINS...AT LEAST ON THE SHOWER FRONT.
ENOUGH INSTABILITY FOR ISOLATED TSTMS JUST ABOUT ANYWHERE...
ESPECIALLY IN AREAS THAT HAD SOME HEATING. MAIN ISSUE AGAIN/STILL
OUT WEST WILL BE THE LOW CLOUDS AND POTENTIAL FOG AGAIN. ADDED
AREAS OF FOG AND MORE CLOUDS WEST OF THE DIVIDE TO ACCOUNT FOR
THIS. EAST OF THE DIVIDE...THE FAVORED W TO NW GAP FLOW AREAS WILL
SEE SOME WIND OVERNIGHT AS THE TROUGH/LOW MOVES OFF TO THE EAST.
HEIGHTS START TO BUILD TOMORROW BUT THERE IS SOME RESIDUAL
MOISTURE IN THE MOUNTAINS AND WITH APPROACH OF WEAK THERMAL
TROUGH/SHORTWAVE IN THE NW...IT MAY HELP FIRE A FEW LATE DAY
SHOWERS/TSTMS IN THE NW MOUNTAINS TUESDAY. OTHERWISE...DRY AND
WARMER TUESDAY.

.LONG TERM...TUESDAY NIGHT THROUGH MONDAY

AS EX-COL...NOW CLOSED LOW TROF...EXITS STAGE RIGHT AND INTO THE
CNTRL PLAINS...A QUICKLY AMPLIFYING RIDGE WILL RETURN TO THE FORECAST
AREA...ALONG WITH MAINLY SUNNY/DRY SKIES THROUGH THURSDAY AND INTO
FRI. THIS WILL ALSO BRING BACK ANOTHER PERIOD OF POSSIBLE NEAR RECORD
HEAT...ESPECIALLY ON THURSDAY...AND POSSIBLY CONTINUING OVER PORTIONS
OF THE CWA THRU FRIDAY. ALL THIS IS AHEAD OF ANOTHER LARGE
AMPLIFYING TROF OVR THE EPAC AND EVENTUALLY THE WRN CONUS.

ATTM...GOOD CONTINUITY BETWEEN MORE POPULAR EXTENDED MDLS ONLY LASTS
THRU PART OF FRIDAY BEFORE FALLING APART...WITH THE GEM...OF
COURSE...HALF-WAY BETWEEN THE GFS AND EURO. IT`S NOT REALLY A
QUESTION OF IF IT WILL HAPPEN AS IT MAY HAVE BEEN 4-5 DAYS
AGO...IT`S REALLY ALL ABOUT TIMING...AND TO A LESSER EXTENT RIGHT
NOW...THE OUTCOME AND IMPACT. STILL...BY SAT NIGHT/SUN MORNING...IT
LOOKS LIKE A LARGER AND MORE SOMEWHAT MORE VIGOROUS VERSION TODAY`S
TROF WILL BE AT HAND...BECOMING NEGATIVELY TILTED AND ALL. BASICALLY
THE GFS STARTS THINGS EARLIER...BECOMING NEG TILTED AND CLOSING OFF
A LOW IN THE TROF...AND THEN KEEPS THE TROF AROUND IN SEVERAL
ITERATIONS THRU A MUCH LONGER PERIOD WELL BEYOND THE EXTENDED. THE
EURO ON THE OTHER HAND...NEVER REALLY DEVELOPS A CLOSED LOW/TROF
SYSTEM IN THE GREAT BASIN...INSTEAD KEEPING IT OPEN THRU THE FCST
PERIOD...PROVIDING FOR A MORE PROGRESSIVE WX SCENARIO.
REGARDLESS...IT DOES LOOK LIKE THE BEST POTENTIAL FOR PRECIP WILL BE
ON SUNDAY IN THE W OR SW AS ALL SCENARIOS HAVE MAIN TROF AXIS TO THE
WEST OF THE FA WITH A GOOD SW FETCH ALOFT. THE SFC IS ANOTHER MATTER
HOWEVER...AS GFS HAS DEVELOPING LEE SIDE LOW/CYCLOGENESIS IN ERN CO
WITH A DEVELOPING FRONT ORIENTED ROUGHLY FROM W TO NE AND MOISTURE
WRAPPING AROUND THIS FEATURE INCLUDING THE UPR LVL
COMPONENT....BRINGING BETTER PRECIP FROM THE SW AND INTO THE ERN FA.
THE EURO ON THE OTHER HAND DEVELOPS A LOW/FRONT TO THE SW AND BRINGS
IT AND POSSIBLY A DEVELOPING WARM FRONT UP THRU THE STATE AND INTO
THE NRN HIGH PLAINS KEEPING A DEVELOPING FRONT MORE PROGRESSIVE N/S
ORIENTED FRONT WITH THE BULK OF MOISTURE/PRECIP PINNED AT AND BEHIND
THE FRONT OFF TO THE WEST...SPLITTING AS IT MOVES ACROSS THE FA.
OTHERWISE...TEMPS BEGIN FALLING OFF SAT...DECREASING FURTHER SUN AND
MON. BREEZY SAT AND SUN...BUT WIND DIRECTION AND EVEN SPEED WILL
CHANGE DEPENDING ON WHICH MDL WINS OUT IN THE END.

&&

.AVIATION.../00Z ISSUANCE/
CONSIDERABLE LOW CLOUDS AND PATCHY FOG IN AND AROUND THE MOUNTAINS
WILL CONTINUE WEST OF THE CONTINENTAL DIVIDE NOT ONLY THIS AFTERNOON
BUT WILL LIKELY BECOME EVEN MORE OF A AVIATION CONCERN AGAIN TONIGHT
AS MORE FOG REDEVELOPS AND VERY LOW STRATUS REDEVELOPS IN SOME
AREAS. IN ADDITION SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS WILL
CONTINUE THROUGH 02Z THIS EVENING. WIDESPREAD MOUNTAIN OBSCURATION
WILL CONTINUE THROUGH TONIGHT. AFTER MORNING LOW CLOUDS AND
FOG...CONDITIONS WILL GRADUALLY IMPROVE WITH VFR IN MOST AREAS BY
LATE MORNING. ISOLATED THUNDERSTORMS ARE POSSIBLE IN THE NORTHWEST
MOUNTAINS TUESDAY AFTERNOON.

EAST OF THE DIVIDE...SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS
WILL LINGER IN THE NORTH HALF OF THE AREA INTO THE EVENING WITH
MORE ISOLATED COVERAGE FURTHER SOUTH. IMPROVEMENT WILL GRADUALLY
RETURN WITH SHOWERS DIMINISHING LATER THIS EVENING. TUESDAY WILL
BE DRY IN MOST AREAS WITH JUST A SMALL CHANCE OF AN ISOLATED
THUNDERSTORM IN THE MOUNTAINS.

&&

.FIRE WEATHER...

AN UPPER LEVEL LOW WILL EXIT THE STATE BY TUESDAY MORNING. THERE
WILL BE A GOOD CHANCE OF SHOWERS AROUND THE MOUNTAINS YET INTO THIS
EVENING WITH ISOLATED THUNDERSTORMS ACROSS THE NORTH HALF. TUESDAY
WILL BE DRY EXCEPT FOR A SMALL CHANCE OF ISOLATED LATE DAY SHOWERS
OR THUNDERSTORMS IN THE NORTHERN MOUNTAINS. A WARM...DRY RIDGE OF
HIGH PRESSURE WILL MOVE IN FOR MIDWEEK WITH MUCH WARMER TEMPERATURES
AND LOWERING AFTERNOON RH`S. SOME SPOTS EAST OF THE DIVIDE MAY SEE
RH`S DOWN AROUND 15 PERCENT BY THURSDAY AFTERNOON. NO SIGNIFICANT
WINDS ARE EXPECTED BUT IT WILL BE IN THE 80S TO AROUND 90 EAST OF
THE DIVIDE.

&&

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

&&

$$

SHORT TERM...SKRBAC
LONG TERM...BRAUN
AVIATION...SKRBAC
FIRE WEATHER...SKRBAC








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