Area Forecast Discussion
Issued by NWS Riverton, WY

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000
FXUS65 KRIW 131632
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1032 AM MDT SAT SEP 13 2014

.SHORT TERM...TODAY THROUGH MONDAY NIGHT

DECIDED TO REMOVE FOG FROM NORTHERN JOHNSON COUNTY FOR THIS MORNING
GIVEN THE FAIRLY WIDE TEMP/DP SPREADS. KEPT MORNING FOG IN THE
CODY FOOTHILLS. AFTER ANOTHER CHILLY MORNING...WE WILL SEE
TEMPERATURES WARM ABOUT 10 DEGREES TODAY OVER FRIDAY AS HIGH
PRESSURE CONTINUES TO BUILD IN FROM THE WEST. A DEEP TROUGH WILL
SWEEP SOUTHEAST ACROSS CANADA THIS AFTERNOON WHICH WILL GLANCE OUR
CWA TODAY. IT WILL COME THROUGH DRY ALONG WITH SOME INCREASE IN
WEST WIND ACROSS SWEETWATER COUNTY THIS AFTERNOON. THERE WILL BE A
WIND SHIFT TO THE NNE EAST OF THE DIVIDE TONIGHT FROM THE
ASSOCIATED WEAK SHORT LIVED BACKDOOR SURFACE BOUNDARY. OTHER THAN
THAT...THIS SYSTEM WILL BE FAIRLY TRANSPARENT. AS HIGH PRESSURE
CONTINUES TO BUILD EAST TOWARD THE ROCKIES...THE TEMPERATURES WILL
WARM STEADILY THROUGH TUESDAY BY WHICH TIME THE RIDGE AXIS WILL BE
OVER THE WESTERN WY BORDER. HIGHS ON TUESDAY WILL BE AROUND 80 AT
THE LOWER ELEVATIONS EAST OF THE DIVIDE AND IN THE 70S WEST.

.LONG TERM...TUESDAY THROUGH SATURDAY

WARM DESERT SW RIDGE IS FORECAST TO EXPAND AND MOVE INTO THE 4
CORNERS REGION INTO THURSDAY BEFORE BEING SUPPRESSED SWD AHEAD OF A
WEATHER SYSTEM THAT IS EXPECTED TO ARRIVE AROUND FRIDAY. MODELS AND
ENSEMBLES VARY CONSIDERABLY STRENGTH AND SOMEWHAT ON TIMING BUT THEY
ALL GENERALLY HAVE A SYSTEM MOVING EAST ACROSS US ON FRIDAY AND THEN
PROBABLY A DRY POST TROUGH DAY NEXT SATURDAY. SO A WARM RIDGE WILL
DOMINATE TUESDAY THROUGH THURSDAY BUT WITH GRADUALLY INCREASING
MOISTURE FROM THE SOUTHWEST WEDNESDAY INTO FRIDAY. EVEN SOME
MOISTURE FROM FUTURE HURRICANE ODILE MAY COME INTO PLAY AHEAD OF THE
FRIDAY TROUGH. MAINLY HIGH LEVEL MOISTURE IN THE WRN MOUNTAINS WEDNESDAY
.A LITTLE MORE MOISTURE INTO MAINLY THE WEST THURSDAY WITH THE
DEEPER MOISTURE LURKING OFF THE SOUTHWEST. THIS DEEPER MOISTURE WILL
LIKELY ARRIVE THURSDAY NIGHT INTO FRIDAY AHEAD OF OUR EXPECTED
FRIDAY TROUGH. GFS AND NOW THE ECMWF ARE PRETTY BULLISH WITH THE
MOISTURE AS EARLY AS THE FAR WEST THURSDAY AFTN OR EVENING AND
THEN SPREADING EAST ACROSS MOST OF THE AREA THURSDAY NIGHT INTO
FRIDAY MORNING. THE GEM IS ALSO PRETTY BULLISH WITH THIS THURSDAY
NIGHT/FRIDAY SYSTEM. UNTIL THEN...WARMER TUESDAY THROUGH WEDNESDAY
AND POSSIBLY INTO THURSDAY EAST OF THE DIVIDE. THEN CONSIDERABLY
COOLER FRIDAY AND POSSIBLY THROUGH SATURDAY. 00Z ECMWF IS STRONGER
YET NOW WITH THIS SYSTEM AND EVEN BRIEFLY CLOSES IT OFF ALONG THE
SRN BORDER FRIDAY NIGHT.

.AVIATION.../18Z ISSUANCE/

VFR CONDITIONS WILL PREVAIL THROUGH 18Z SUNDAY. SCATTERED MID LEVEL
ALTOCUMULUS AND UPPER LEVEL DENSE CIRRUS WILL BE ENCOUNTERED ACROSS
SOUTHWEST WYOMING...WHILE MOST AREAS WILL BE SKC.  SURFACE WINDS
WEST AT 15 TO 20 KTS WITH GUSTS TO 30 KTS WILL EXIST ACROSS THE
SOUTH THROUGH 02Z SUNDAY.

.FIRE WEATHER...

..DRY WINDY CONDITIONS WILL PRODUCE RED FLAG CONDITIONS FROM
1 PM MDT TO 8 PM MDT ACROSS SWEETWATER COUNTY...

DRY WINDY CONDITIONS WILL DEVELOP ACROSS SWEETWATER COUNTY THIS
AFTERNOON AND CONTINUE INTO THE EVENING. RELATIVE HUMIDITY WILL
DROP BELOW 15 PERCENT WHILE WEST WINDS OF 20 MPH GUST TO 30 MPH.
COMBINING WITH CRITICALLY DRY FUELS...THE WINDY DRY CONDITIONS
WILL PRODUCE RED FLAG CONDITIONS.

A BUILDING AREA OF HIGH PRESSURE WILL REMAIN OVER THE AREA FOR THE
NEXT FEW DAYS. WARMING CONDITIONS ARE EXPECTED THROUGH THE
WEEKEND...WITH HUMIDITY WORKING TO DECREASE AS WELL. ALL ELEMENTS
WILL REMAIN OUTSIDE OF CRITICAL THRESHOLDS...LEAVING FIRE WEATHER
CONCERNS MINIMAL. WEST WINDS WILL INCREASE IN ZONE 279 THIS AFTERNOON.
EAST OF THE DIVIDE AND IN ZONE 279...WINDS WILL VEER TO THE NORTH
NORTHEAST TONIGHT.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
RED FLAG WARNING UNTIL 8 PM MDT THIS EVENING WYZ279.

&&

$$

SHORT TERM...LIPSON
LONG TERM...SKRBAC
AVIATION...C.BAKER
FIRE WEATHER...C.BAKER






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