Area Forecast Discussion
Issued by NWS Riverton, WY

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000
FXUS65 KRIW 251703
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1103 AM MDT MON AUG 25 2014

.SHORT TERM...TODAY THROUGH WEDNESDAY NIGHT

A SLUG OF MOISTURE CONTINUES TO MOVE THROUGH SOUTHERN WYOMING THIS
MORNING. ONE ROUND OF SHOWERS AND THUNDERSTORMS IS ABOUT TO MOVE OUT
OF THE FORECAST AREA...BUT ANOTHER ROUND OF ACTIVITY CONTINUES TO
MOVE INTO SOUTHWESTERN SWEETWATER COUNTY. SATELLITE SHOWS SOME
WARMING TOPS WITH THESE STORMS...THOUGH ALSO HAS EMBEDDED SPOTS
WHICH HAVE REMAINED ON THE COLDER SIDE. ANTICIPATED PERIODS OF
SHOWERS AND THUNDERSTORMS TO CONTINUE THIS MORNING.

AN AREA OF LOW PRESSURE NOTED ACROSS CENTRAL IDAHO THIS
MORNING...WHICH IS IN FAIR AGREEMENT TO WHAT MODELS HAVE BEEN
SUGGESTING. THE AREA OF LOW PRESSURE IS EXPECTED TO SLIDE FURTHER
SOUTH TODAY...ENHANCING SOUTHWEST FLOW ACROSS THE FORECAST AREA.
MOISTURE TRAPPED IN THE FLOW WILL SPREAD ACROSS WESTERN WYOMING
DURING THE AFTERNOON AND EVENING HOURS...WITH SHOWERS AND
THUNDERSTORMS FAVORABLE. TEMPERATURES WILL STILL BE ABLE TO WARM IN
THIS PATTERN.

THE AREA OF LOW PRESSURE WILL DROP FURTHER SOUTH INTO TUESDAY...WITH
THE CENTER OF THE SYSTEM EXPECTED TO BE ACROSS WESTERN NEVADA.
CONTINUED MOISTURE IS EXPECTED WITH ADDITIONAL SHOWER ACTIVITY. THE
AREA OF LOW PRESSURE WILL MOVE EAST ON TUESDAY AND INTO WEDNESDAY
MORNING...THOUGH THE SPEED OF ITS MOVEMENT DIFFERS ON EACH MODEL.
REGARDLESS...THE PATH ACROSS SOUTHERN WYOMING IS A FAVORABLE SETUP
FOR SHOWERS AND THUNDERSTORMS...ESPECIALLY ACROSS SOUTHERN WYOMING.
COVERAGE AND INTENSITY OF ASSOCIATED ACTIVITY AGAIN VARIES BY
MODEL...BUT MOST ARE IN AGREEMENT THAT COVERAGE WILL INCREASE
THROUGH THE DAY ON WEDNESDAY. THE AREA OF LOW PRESSURE MOVES FAR
ENOUGH EAST BY LATE WEDNESDAY TO ALLOW SOME DRIER CONDITIONS TO BE
EXPECTED.

.LONG TERM...THURSDAY THROUGH MONDAY

AT 12Z THURSDAY...AN UPPER LOW SHOULD BE ACROSS W/SW COLORADO AND IS
PROGGED TO PUSH SLOWLY SOUTHEAST DURING THE DAY THURSDAY. ALTHOUGH
THIS TRACK COULD RESULT IN SOME SHOWER ACTIVITY OVER THE SOUTHERN
SECTIONS OF THE FORECAST AREA...WILL KEEP THE FORECAST DRY FOR
NOW...AND ALLOW LATER SHIFTS DECIDE IF SOME POPS ARE WARRANTED.
CURRENTLY THE ECMWF IS THE ONLY MODEL SPITTING OUT PRECIPITATION
OVER THE SOUTH THURSDAY.

WEAK RIDGING IS EXPECTED FRIDAY...WITH ENOUGH MOISTURE FOR ISOLATED
CONVECTION MAINLY OVER THE NORTHWESTERN MOUNTAINS AND ADJACENT
LOWER ELEVATIONS.

ATTENTION THEN TURNS TO A TROUGH FOR THIS UPCOMING WEEKEND. THE 00Z
GFS HAS TRENDED TOWARD THE LESS AMPLIFIED SOLUTION THAT THE ECMWF
WAS ADVERTISING LAST NIGHT. AHEAD OF THE MAIN TROUGH...MODELS ARE
SHOWING THE POSSIBILITY OF A SHORTWAVE IMPACTING THE NORTHERN
ROCKIES WHICH COULD RESULT IN SOME CONVECTION...MAINLY OVER THE
NORTHWEST. OTHERWISE...THE MAIN IMPACTS SATURDAY WILL BE AN INCREASE
IN WINDS AS A LEE TROUGH DEVELOPS...WITH WARM TO VERY WARM TEMPS.
SOME AREAS...ESPECIALLY IN THE ROCK SPRINGS TO CASPER
CORRIDOR...COULD HIT RED FLAG CONDITIONS. HOWEVER...RECENT RAINS
WILL HELP MITIGATE THE IMPACTS IF THE RED FLAG WEATHER PARAMETERS
ARE MET.

THE INITIAL COLD FRONT WITH THIS TROUGH IS EXPECTED TO PUSH ACROSS
THE COWBOY STATE FROM WEST TO EAST IN THE SATURDAY NIGHT/SUNDAY TIME
FRAME...WITH POSSIBLY A SECONDARY COLD FRONT PUSHING SOUTH INTO THE
AREA SUNDAY NIGHT INTO MONDAY. MUCH OF THE DYNAMICS WITH THIS SYSTEM
BASED ON ITS CURRENT TRACK WILL REMAIN NORTH OF THE AREA WITH THE
BEST SHOT OF PRECIPITATION OVER THE NORTH...WITH VERY SLIM CHANCES
OVER THE SOUTH. THUS COULD SEE A MAINLY DRY COLD FRONT WITH WINDY
CONDITIONS ESPECIALLY OVER THE CENTRAL AND SOUTHERN AREAS FOR
SUNDAY. ALTHOUGH TEMPS ARE EXPECTED TO BE COOLER SUNDAY...THERE
COULD AGAIN BE A POSSIBILITY FOR ELEVATED FIRE WEATHER CONDITIONS
SUNDAY DEPENDING UPON HOW DRY THE AIR MASS IS BEHIND THE INITIAL
COLD FRONT. THERE IS ALSO THE POSSIBILITY THAT SOME MOISTURE FROM
HURRICANE MARIE COULD GET CAUGHT UP IN THE FLOW WITH THE TROUGH
DURING THE WEEKEND. THERE IS PLENTY OF TIME TO WATCH HOW ALL OF
THIS EVOLVES.

.AVIATION.../18Z ISSUANCE/

EAST OF THE DIVIDE...KCOD/KCPR/KLND/KRIW/KWRL ROUTES

SCATTERED SHOWERS WITH ISOLATED THUNDERSTORMS WILL DEVELOP ALONG
AND NEAR THE CONTINENTAL DIVIDE 18Z TO 20Z AND THE MOVE EAST
NORTHEAST AT 20 TO 25 KTS THROUGH 06Z. AS THE SHOWERS AND
THUNDERSTORMS MOVE INTO MORE STABLE AIR OVER NORTHERN WYOMING...
RAPID WEAKENING AND DISSIPATION IS EXPECTED.  AREAS OF MOUNTAIN
OBSCURATIONS WILL OCCUR WITH MVFR TO IFR CEILINGS AND VISIBILITIES
REDUCED IN HEAVY RAIN. PARTIAL CLEARING WILL OCCUR FROM 09Z
THROUGH 15Z.

WEST OF THE DIVIDE...KBPI/KJAC/KPNA/KRKS ROUTES

WIDESPREAD SHOWERS WITH EMBEDDED THUNDERSTORMS WILL CONTINUE AND
BECOME HEAVIER OVER THE WESTERN MOUNTAINS UP TO NEAR THE
CONTINENTAL DIVIDE 18Z TO 20Z AND THE MOVE EAST NORTHEAST AT 20 TO
25 KTS THROUGH 06Z. RAPID WEAKENING AND DISSIPATION IS EXPECTED AFTER
06Z WITH VALLEY STRATUS AND FOG DEVELOPING 09Z THROUGH 12Z.  AREAS
OF MOUNTAIN OBSCURATIONS WILL OCCUR WITH MVFR TO IFR CEILINGS AND
VISIBILITIES REDUCED IN HEAVY RAIN. MVFR TO IFR CEILINGS AND
VISIBILITIES IN STRATUS AND FOG IS EXPECTED IN THE VALLEYS FROM
09Z THROUGH 15Z.

.FIRE WEATHER...

PERIODS OF SHOWERS AND THUNDERSTORMS REMAIN POSSIBLE THROUGH THE
NEXT FEW DAYS. ANOTHER AREA OF LOW PRESSURE IS ANTICIPATED TO IMPACT
THE STATE LATE TUESDAY AND INTO WEDNESDAY. THIS SYSTEM WILL
ESPECIALLY IMPACT SOUTHERN WYOMING...WITH COOLER TEMPERATURES AND
ENHANCED SHOWER COVERAGE. THE CONTINUED ANTICIPATION OF SHOWERS AND
THUNDERSTORMS COUPLED WITH COOLER TEMPERATURES LEAVES LITTLE CONCERN
FOR FIRE WEATHER BEHAVIOR FOR THE NEXT FEW DAYS.

&&

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

$$

SHORT TERM...BRANHAM
LONG TERM...WM
AVIATION...C.BAKER
FIRE WEATHER...BRANHAM






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