Area Forecast Discussion
Issued by NWS Riverton, WY

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000
FXUS65 KRIW 212017
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
217 PM MDT THU AUG 21 2014

.SHORT TERM...TONIGHT THROUGH FRIDAY

SHOWERS AND A FEW THUNDERSTORMS WILL CONTINUE INTO THE EVENING BUT
WITHOUT ANY SIGNIFICANT FORCING...ACTIVITY IS EXPECTED TO BE WEAK
AND WILL DIMINISH AND WILL MAINLY BE LIMITED TO THE NORTHWEST THIS
EVENING. THE MODELS HAVE SLOWED DOWN A BIT WITH THE PROGRESSION OF
THE NEXT TROUGH SO INSTEAD OF SHOWERS DEVELOPING BY SUNRISE THEY ARE
EXPECTED TO START A BIT LATER TOWARD NOON ON FRIDAY WHEN WIDESPREAD
SHOWERS WILL DEVELOP OVER WESTERN WY AND WILL SPREAD TOWARD CENTRAL
WY AFTER 21Z FRIDAY ONCE THE NEGATIVELY TILTED TROUGH OVER THE PAC
NW CLOSES OFF OVER WASHINGTON AND OREGON AND THE SOUTHWEST FLOW
AHEAD OF THIS LOW INCREASES. IT ALSO LOOKS LIKE THE
ATTENDANT DYNAMICS WILL HOLD OFF UNTIL THE BEGINNING OF THE LONG
TERM PERIOD AS WELL...BUT A COLD FRONT WILL TRY TO DIP INTO NORTHERN
AND WESTERN WYOMING LATE IN THE PERIOD...WITH SOME ENHANCEMENT
EXPECTED ALONG AND BEHIND THE FRONT...SO OVERALL FRIDAY WILL BE A
SHOWERY DAY WITH A FEW THUNDERSTORMS POSSIBLE ACROSS THE NORTH AND
WEST WITH SOME TEMPERATURE REBOUND EAST OF THE DIVIDE IN THE
SOUTHWEST FLOW WHILE THE WEST AND NORTH REMAIN UNSEASONABLY COOL.

.LONG TERM...FRIDAY NIGHT THROUGH THURSDAY

OVERALL...EXTENDED WILL BE CHARACTERIZED BY BELOW AVG TEMPS AND MUCH
HIGHER THAN NORMAL PRECIPITATION CHANCES.

FRI NIGHT THRU SUNDAY...CYCLO/FRONTO GENESIS ONGOING OVR THE FA FRI
NIGHT WITH THE APPROACH OF THE W/NW CONUS TROF. FRONT/BOUNDARY(S)
CUTTING DIAGONALLY FROM SW TO NCNTRL WY W/ LOW OVR CNTRL WY. TWO
DISTINCT MOISTURE SOURCES...ONE FROM THE MONSOONALISH DESERT SW/SRN
ROCKIES...THE OTHER FROM THE EPAC...WITH BOTH OF THOSE AREAS COMING
TOGETHER INTO THE NRN HIGH AND NRN PLAINS...NE OF THIS FA.
ISOLATED TO WIDELY SCATTERED SHRA/TSRA AHEAD OF LOW/FRONT...
SCATTERED TO NUMEROUS SHRA/ISO TSRA BEHIND OVR THE W/NW CWA.
CHANGEOVER TO SOME LIGHT SNOWFALL OVERNIGHT FOR ELEVATIONS ABOVE
10500 FT TO BEGIN WITH FRI NIGHT...FALLING TO 9000 TO 9500 FT BY
SAT NIGHT. IN THESE AREAS...EXPECT 12 HRS SNOWFALL TOTALS DURING
THE EVENING/OVERNIGHT PERIODS TO EXTEND UP TO A COUPLE OF INCHES
EACH NIGHT AT THE HIGHER ELEVATIONS...WITH LOCALIZED AREAS
SATURDAY NIGHT RECEIVING UP TO 3 INCHES. WITH THE STRONG UPR TROF
TAKING ITS TIME TO MOVE ACROSS THE REGION...COUNTING AT LEAST TWO
BONAFIDE FRONTAL PUSHES BETWEEN FRI NIGHT AND SUN NIGHT.
ATTM...SAT/SAT NIGHT LOOKS TO BE THE BUSIEST OF THE NEAR FCST
PERIOD AS LEE SIDE LOW DEVELOPS OVR ERN/SERN WY DOWN TO THE S INTO
ERN CO...PULLING ANOTHER QUICKLY DEVELOPING SFC LOW AND FRONT THRU
THE FA DURING THE EVENING/OVERNIGHT PERIOD(S). STRONGER STORMS
PERHAPS ACROSS NATRONA COUNTY FOR A COUPLE OF HRS LATE
AFTERNOON/EARLY EVENING. SUNDAY...POST FRONTAL WITH (FINALLY)
EXITING UPR TROF. EMPHASIS WILL BE ON THE COOL TEMPERATURES LEFT
OVER...SKIES TRYING TO CLEAR SOME FROM SOUTH TO NORTH...AND MOST
PRECIP CHCS BEING RELEGATED TO THE NRN/NWRN FA...ESPECIALLY THE
MOUNTAINS WHERE BOTH TERRAIN FORCING AND INSTABILITY WILL BE
MAXIMIZED.

MONDAY AND BEYOND...WHERE PREVIOUS LR MDL RUNS HAD THE GFS AND EURO
DIVERGING QUITE A BIT W/ RESPECT TO HANDLING ANOTHER WRN CONUS
TROF...THE EURO HAS COME AROUND TO THE GFS (AND OTHER MDLS) WAY OF
THINKING ...KEEPING THE TROF MORE PROGRESSIVE AND NOT CUTTING IT OFF
IN THE GREAT BASIN AS BEFORE. ACTUAL SIMILARITIES BETWEEN MDLS NOW
REMAIN GOOD AND CONSISTENT THRU NEXT THU....FROM THE UPR LVLS DOWN
TO THE SFC. NEXT STORM/RAINIEST PERIOD CONTINUES TO LOOK LIKE MON
NIGHT THRU TUE MORNING...W/ LITTLE AS NEXT UPR TROF WAVE AXIS AND
SFC FRONT PUSHES THRU W/ SOME CHC FOR PRECIP EVERYWHERE ONCE AGAIN.
FROM WED THRU THU...PRECIP CHCS DROP CONSIDERABLY AND BECOME MORE
DIURNAL WITH EXITING TROF ALOFT TRANSITIONING TO MODEST
RIDGING.

&&

.AVIATION.../00Z ISSUANCE/

AN ACTIVE PERIOD WILL CONTINUE THROUGH THIS TAF PERIOD AS WELL...AND
BEYOND INTO SATURDAY. THIS SYSTEM WILL CONTINUE TO BRING A SERIES OF
DISTURBANCES AND COLD FRONTS ALONG WITH SCT SHRA/ISOLD TSRA.

DURING THIS TAF PERIOD...MOST ACTIVITY WILL BE VCNTY AND NW OF A
KEMM-KDUB-KBYG LINE MORE ISOLD SOUTH OF THIS LINE. LCL IFR/LIFR FG
AND CIGS MAY DEVELOP IN THE WESTERN VALLEYS AFTER 09Z TONIGHT...
MAINLY VCNTY KJAC-KAFO. THE ATMOSPHERE WILL QUICKLY STABILIZE AFTER
3Z FRIDAY WITH MOST SHOWER AND THUNDERSTORM ACTIVITY MOVING NE INTO
MONTANA AND THE NORTHERN PLAINS. ISOLD-SCT TSRA WILL BLOSSOM IN THE
SAME GENERAL AREA ACROSS THE WEST AND NORTH TOMORROW AFTERNOON.

&&

.FIRE WEATHER...

THE ACTIVE AND WET PATTERN CONTINUES WITH A HIGH LIKELIHOOD OF
WETTING RAIN THROUGH SATURDAY FOR THE ENTIRE FORECAST AREA...WITH
THE MOST RAIN...AND POSSIBLY HIGH ELEVATION SNOW...POSSIBLE ACROSS
THE WEST AND NORTH. A POTENT PACIFIC STORM SYSTEM WILL APPROACH THE
AREA LATER TONIGHT WITH NUMEROUS SHOWERS AND A FEW THUNDERSTORMS
SPREADING FROM NORTHWEST TO SOUTHEAST LATER TONIGHT THROUGH FRIDAY
AND INTO SATURDAY. COOLER WEATHER WILL FILTER IN BEHIND THIS WEATHER
SYSTEM WITH SNOW LEVELS LOWERING TO 8000 FEET IN THE NORTHERN
MOUNTAINS BY LATE SATURDAY NIGHT. HIGH TEMPERATURES IN MOST LOWER
ELEVATIONS BY SATURDAY WILL STRUGGLE TO GET ABOVE 70. WINDS WILL BE
GENERALLY LIGHT EXCEPT FOR BRIEF GUSTY WINDS NEAR THUNDERSTORMS AS
WELL AS DURING THE COLD FRONTAL PASSAGE THIS WEEKEND.

&&

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

$$

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




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