Area Forecast Discussion
Issued by NWS Riverton, WY

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000
FXUS65 KRIW 141642
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1042 AM MDT SUN SEP 14 2014

.SHORT TERM...TODAY THROUGH TUESDAY NIGHT

ANOTHER DRY SHORTWAVE TROUGH NOW DIVING SSE OVER CENTRAL ALBERTA
WILL BE DIVING SOUTHEAST ACROSS THE NORTHERN PLAINS TODAY WHICH
WILL RESULT IN A TIGHTENING SURFACE PRESSURE GRADIENT. AS A
RESULT...WEST WINDS WILL INCREASE ACROSS SOUTHWEST WYOMING
INCLUDING SWEETWATER AND SOUTHERN LINCOLN COUNTIES ALONG WITH
LOWERING RH PROMPTING THE ISSUANCE OF ANOTHER RED FLAG WARNING FOR
THIS AREA VALID 2 PM THROUGH 8 PM TODAY. SEE NO REASON WHY THESE
WEATHER CONDITIONS SHOULD BE MUCH DIFFERENT THAN WHAT OCCURRED IN
SOUTHWEST WYOMING SATURDAY WITH THE PREVIOUS GLANCING FROM THE
OTHER DRY SOUTHEAST BOUND SHORTWAVE ON THE FRONT SIDE OF THE
APPROACHING RIDGE OF HIGH PRESSURE. COULD SEE SOME BUILD UPS OVER
THE UINTA MTNS THIS AFTERNOON WHERE SOME CAPES WILL BE IN EXTREME
SOUTHERN WY. AFTER TODAY ITS JUST A MATTER OF THE RIDGE AXIS
APPROACHING THE ROCKIES ALONG WITH A STEADY WARMING TREND THROUGH
TUESDAY. THE RIDGE AXIS SHOULD BE OVER WEST CENTRAL WY BY 12Z WED.
MAINLY LIGHT WINDS ARE EXPECTED IN MOST AREAS MONDAY AND TUESDAY.

.LONG TERM...WEDNESDAY THROUGH SUNDAY

WARM RIDGE AXIS MOVES OVHD WEDNESDAY IN ADVANCE OF OUR EWD MOVING
PACIFIC SHORTWAVE. MODELS HAVE STRUGGLED WITH TIMING AND WHETHER
THIS SYSTEM WILL SPLIT WITH MORE ENERGY EITHER REMAINING BEHIND TO
THE SW OR COMING THROUGH AS A WEAKER MORE ELONGATED TROUGH. GENERAL
ENSEMBLE MEMBERS OF VARIOUS MODELS GENERALLY SHOW A TROUGH COMING
THROUGH BUT WITH ENOUGH WEAKNESS ON THE SOUTH END TO GIVE THAT KIND
OF IDEA SOME CREDENCE. GFS IS PROBABLY THE STRONGEST RIGHT NOW WITH
THE 00Z ECMWF THE WEAKEST AND THE GEM IN THE MIDDLE. ALL HAVE SOME
POTENTIAL FOR A DECENT MOISTURE SURGE FROM THE DESERT SW WITH BOTH
MONSOONAL AND SOME HURRICANE ODILE MOISTURE. DEPENDING ON THE
STRENGTH OF THE TROUGH COULD SEE ENOUGH OF A SURGE FOR SOME HEAVIER
SHOWERS AND THUNDERSTORMS IN THE WEST AND SOUTH THURSDAY AFTERNOON
INTO THURSDAY EVENING. ANOTHER SHORTWAVE MOVE MOVE SE ACROSS THE AREA ON
FRIDAY IN DEVELOPING NW FLOW. THE ECMWF IS HOLDING THE RIDGE TO
THE WEST INTO SUNDAY WHILE THE GFS RACES IT IN FOR A MUCH WARMER
AND DRIER WEEKEND. THE ECMWF HAS ANOTHER POTENTIAL SHORTWAVE
DROPPING SWD SATURDAY NIGHT TO REINFORCE THE COOL AIR IN THE NW
FLOW ALREADY IN PLACE. THE ECMWF WOULD KEEP IT COOL THROUGH THE
WEEKEND...ESPECIALLY EAST OF THE DIVIDE WITH HIGHS IN THE 60S TO
LOWER 70S. THE GFS WOULD HAVE US BACK IN THE 80S BY SUNDAY. SIDING
TOWARDS THE ECMWF WITH THE STRONG GULF OF ALASKA UPPER LOW PUMPING
UP THE RIDGE AND THE MORE REALISTIC WAVELENGTH SHOWN DOWNSTREAM
COMPARED TO THE GFS.

.AVIATION.../18Z ISSUANCE/

VFR CONDITIONS WILL PREVAIL THROUGH 18Z MONDAY. A GUSTY WIND WILL
OCCUR AGAIN IN SOUTHERN AND SOUTHWEST WYOMING FROM ABOUT 19Z UNTIL
01Z MONDAY. THIS WOULD INCLUDE KRKS...KBPI...AND KPNA TERMINAL
SITES.

.FIRE WEATHER...

LOW RELATIVE HUMIDITY AND GUSTY WEST WINDS COMBINING WITH CRITICAL
FUELS WILL PRODUCE RED FLAG CONDITIONS ACROSS UINTA...SWEETWATER AND
SOUTHERN LINCOLN COUNTIES SUNDAY AFTERNOON FROM 2 PM UNTIL 8 PM MDT.
THUS A NEW RED FLAG WARNING HAS BEEN ISSUED.

DRY WEST NORTHWEST FLOW ALOFT WITH HIGH PRESSURE WILL REMAIN OVER
WESTERN AND CENTRAL WYOMING THROUGH TODAY. SCATTERED MID AND HIGH
CLOUDS WILL MOVE ACROSS THE SOUTHWEST AND FAR NORTH...WHILE MOST
AREAS REMAIN CLEAR. TEMPERATURES WILL CONTINUE TO WARM. DRY AND
BREEZY CONDITIONS WITH WARMING WILL CONTINUE THROUGH TUESDAY.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
RED FLAG WARNING FROM 2 PM THIS AFTERNOON TO 8 PM MDT THIS
EVENING WYZ277-279.

&&

$$

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





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