Area Forecast Discussion
Issued by NWS Riverton, WY

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000
FXUS65 KRIW 252120
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
320 PM MDT FRI JUL 25 2014

.SHORT TERM...TONIGHT THROUGH SATURDAY

A DISTURBANCE WILL LEAVE A FEW SHOWERS OVER SOUTHEASTERN SWEETWATER
AND SOUTHEASTERN NATRONA COUNTIES TODAY. SHOWER ACTIVITY SHOULD
GENERALLY END BY THE EARLY EVENING HOURS...WITH A RIDGE OF HIGH
PRESSURE REMAINING OVER THE AREA. THIS RIDGE WILL GENERALLY LEAVE
DRY CONDITIONS OVER THE FORECAST AREA FOR SATURDAY.

WARM TEMPERATURES...DRY HUMIDITY...AND GUSTY WINDS TO 30 MPH WILL
PERMIT THE RED FLAG WARNING TO CONTINUE ACROSS SWEETWATER COUNTY
THROUGH SATURDAY EVENING. SIMILAR TO THE PAST COUPLE DAYS...CRITICAL
CONDITIONS WILL LULL DURING THE OVERNIGHT HOURS...BUT INCREASE
THROUGH THE AFTERNOON HOURS. OTHERWISE...A RELATIVELY BENIGN DAY IS
EXPECTED ACROSS THE FORECAST AREA FOR SATURDAY.

.LONG TERM...SATURDAY NIGHT THROUGH FRIDAY

WITH HIGH PRESSURE OVER THE NW NORTHERN PLAINS AND LOW SURFACE
PRESSURE OVER THE GREAT BASIN...LOW LEVEL FLOW ON SUNDAY WILL BE
GENERALLY EASTERLY. HOWEVER...THE MID TO UPPER LEVELS WILL BE
FAIRLY DRY...THUS MOSTLY SUNNY SKIES AND NEAR NORMAL TEMPERATURES.

BY MONDAY...THE HIGH PRESSURE OVER THE SOUTHERN ROCKIES WILL BEGIN
TO BRING SOME INSTABILITY AND MID LEVEL MOISTURE NORTHWARD OVER
WYOMING. SHOWERS AND STORMS SHOULD DEVELOP IN THE AFTERNOON AND
FOCUS BOTH ACROSS SOUTHWEST WY AND THE BOUNDARY HELD UP ON THE
CONTINENTAL DIVIDE. THE CONVECTIVE ACTIVITY APPEARS TO BE
ISOLATED AT THIS TIME. THE GFS IS EMPHASIZING PRECIPITATION DURING
THE MONDAY NIGHT TIME FRAME...AS COMPARED TO THE ECMWF AND TYPICAL
DIURNAL PATTERN. HAVE KEPT THE FORECAST MORE IN LINE WITH THE
ECMWF FOR THIS EXTENDED PERIOD. ON TUESDAY...A SHORTWAVE TROUGH
MOVES NORTHWARD FROM THE GREAT BASIN INTO CENTRAL IDAHO. DYNAMICS
AND MOISTURE ARE POINTING TO TUESDAY BEING A DAY OF WIDESPREAD
SHOWERS AND THUNDERSTORMS ACROSS THE AREA...ALTHOUGH THEY DON`T
APPEAR TO BE TERRIBLY STRONG AT THIS TIME. THERE COULD BE SOME
POTENTIAL FOR SLOW MOVING SYSTEMS COMBINED WITH THE PRECIPITABLE
WATER VALUES OVER AN INCH THAT GENERATE HEAVY RAIN AND POSSIBLE
FLASH FLOODING.

AS THE TROUGH ROUNDS THE TOP OF THE RIDGE...THE FOCUS ON WEDNESDAY
SHIFTS TO WESTERN WYOMING WITH THE CONVECTIVE ACTIVITY. LOW LEVEL
EASTERLY WILL KEEP MOIST COOL AIR IN THE CENTRAL TO EASTERN PART
OF THE STATE. EXPECTING CONVECTIVE ACTIVITY TO TAPER OFF IN LATE
EVENING HOURS...WHEREAS TUESDAY NIGHT THE ACTIVITY IS POSSIBLE TO
CONTINUE ALL NIGHT.

AT THIS POINT IS WHERE A SUBTLE DIFFERENCE APPEARS BETWEEN THE 12Z
GFS AND 12Z ECMWF...THE ECMWF BRINGS ANOTHER WEAK TROUGH INTO
SOUTHERN MONTANA THURSDAY TO ACCENTUATE THE CONVECTIVE ACTIVITY IN
NORTHWEST WYOMING AS WELL AS KEEP TEMPERATURES A LITTLE COOLER.
THE GFS HOWEVER KEEPS THE TROUGH BACK IN EASTERN OREGON AND
AMPLIFIES THE RIDGE UP THE SPINE OF THE ROCKIES FOR A DRIER
THURSDAY. A SWITCH OCCURS ON FRIDAY WHEN THE GFS IS WET AND THE
ECMWF GOES DRY IN WESTERN WYOMING. BOTH MODELS INDICATE NEAR
NORMAL TEMPS FOR THE LATTER END OF THE WEEK. OVERALL IT WILL BE AN
ACTIVE WEEK NEXT WEEK.

&&

.AVIATION.../00Z ISSUANCE/

GENERALLY VFR CONDITIONS WILL BE FOUND ACROSS THE FORECAST AREA
THROUGH THE FORECAST PERIOD. A FEW ISOLATED SHOWERS WILL BE POSSIBLE
SOUTHEAST OF A LINE FROM KRKS TO KCPR...MAINLY THROUGH 02Z THIS
EVENING. GUSTY WIND ACROSS SOUTHEASTERN WYOMING SHOULD WEAKEN AFTER
03Z THIS EVENING. VFR CONDITIONS WILL BE FOUND ACROSS THE AREA ON
SATURDAY UNDER THE PRESENCE OF HIGH PRESSURE. ANOTHER ROUND OF GUSTY
WIND WILL RETURN TO KRKS AFTER 18Z SATURDAY WITH GUSTS UP TO 25 KTS
POSSIBLE.

&&

.FIRE WEATHER...

CRITICAL FIRE WEATHER CONDITIONS WILL PERSIST OVER THE MAJORITY OF
CRITICALLY DRY ZONES THROUGH THIS EVENING. MUCH OF THE AREA WILL SEE
RELIEF FROM RED FLAG CONDITIONS WITH DIMINISHED WIND UNDER THE
PRESENCE OF THE AREA OF HIGH PRESSURE. HOWEVER...SWEETWATER COUNTY
WILL AGAIN SEE AN INCREASE IN WIND DURING SATURDAY AFTERNOON. WITH
HOT AND DRY CONDITIONS EXPECTED TO REMAIN AS WELL...THE RED FLAG
WARNING FOR FIRE WEATHER ZONE 279 HAS BEEN EXTENDED THROUGH SATURDAY
EVENING. OTHERWISE...HOT AND DRY CONDITIONS WILL PERSIST...BUT
WEAKENED WIND WILL KEEP CONDITIONS FROM EXPERIENCING WIDESPREAD
CRITICAL FIRE BEHAVIOR THROUGH SATURDAY.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
RED FLAG WARNING UNTIL 9 PM MDT THIS EVENING
WYZ280-283-285-287-300.

RED FLAG WARNING UNTIL 9 PM MDT SATURDAY WYZ279.

&&

$$

SHORT TERM...BRANHAM
LONG TERM...MCDONALD
AVIATION...BRANHAM
FIRE WEATHER...BRANHAM






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