Area Forecast Discussion
Issued by NWS Riverton, WY

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FXUS65 KRIW 030902
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
302 AM MDT MON AUG 3 2015

.SHORT TERM...TODAY THROUGH WEDNESDAY NIGHT

WV IMAGERY SHOWING STAGNANT LARGE SCALE PATTERN WITH RIDGE WRN
CONUS...TROF ERN CONUS. UPR LVL CENTER OF THIS HIGH NOW LOCATED OVR
NRN MEXICO WITH A SMALL BUT RATHER STRONG EMBEDDED SW/MCV
DEVELOPING OVR SFC TROF/FRONT IN UT. FURTHER UPSTREAM TO THE NW OVR
BC...A LARGE DEEP LOW WILL BEGIN ITS MIGRATION SEWD...READY TO
AFFECT THE FA SOMETIME ON WED ALONG WITH ANOTHER WAVE NOW CENTERED
OFFSHORE NRN CALIFORNIA. OTHERWISE...AT THE SFC LOWER P WEST OF THE
DIVIDE...HIGHER P EAST/NORTHEAST WITH NOW NEAR STATIONARY FRONT
DIVIDING THESE TWO AREAS.

TODAY...UPR LVL RIDGE AXIS ROTATES CLOCKWISE ACROSS WY...WITH AXIS
CENTERING OVR WY. AS UPR SUBTROPICAL SW/MCV...THAT WE HAVE BEEN
TRACKING NOW FOR SEVERAL DAYS...CONTINUES TO MOVE THIS DIRECTION OUT
OF UT...BETTER MONSOONAL-LIKE MOISTURE WILL ACCOMPANY THIS
DISTURBANCE AND FEED ACROSS WY FROM THE S/SW. ASSOCIATED PWS WILL
ALSO INCREASE TO HIGHER THAN NORMAL...APPROACHING AN INCH OR MORE IN
SOME LOCATIONS. MODERATE TO OCCASIONALLY HEAVY RAINFALL...ESPECIALLY
WITH EMBEDDED THUNDERSTORMS...WILL BE COMMON WEST OF THE
DIVIDE...LEADING INTO PORTIONS OF CENTRAL WY BY EVENING. THE
DEVELOPING MCV/DISTURBANCE WILL BRING WIDELY VARIABLE STORM MOTION
AS IT ROTATES THRU THE FA. FAVORED LOCATIONS FOR HEAVIEST QPF THRU
THE AFTERNOON AND EARLY EVENING WILL BE LOCATED UNDER THE PROJECTED
PATH OF THE DISTURBANCE WHICH WILL BE CO-LOCATED WITH THE DEEPEST
MOISTURE OVR THE REGION TO THE SOUTH OF THE AREA BOUNDED BY THE WIND
RIVER MOUNTAINS ON THE NORTH...AND THE SALT/WYOMING RANGES ON THE
WEST. 1 TO 3 INCHES OF TOTAL RAINFALL CAN BE EXPECTED ON A LOCALIZED
BASIS...ESPECIALLY OVER THE HIGH TERRAIN OF SOUTHWEST MOUNTAIN GROUP
WHERE THE MODEST MOVEMENT TO THE NORTH THRU THE DAY AND NIGHT...
ALONG WITH THE RATHER TIGHT ROTATION OF THE COMPLEX...WILL PIN THE
MOST LIKELY AREA FOR FLASH FLOODING OVER FAVORED PORTIONS OF THE
CENTRAL AND SOUTHWEST MOUNTAINS. WILL POST A FLASH FLOOD WATCH FOR
THE SALT/WYOMING/AND WIND RIVER MOUNTAINS FOR THIS AFTERNOON AND
EVENING. ADDITIONALLY...MONDAY AFTERNOON...FROM EASTERN FREMONT
COUNTY...EAST TO NATRONA AND SOUTHERN JOHNSON COUNTY...MAY SEE A
BRIEF PERIOD OF ISOLATED STRONGER STORMS WITH GUSTY STRONG WINDS AND
SMALL HAIL POSSIBLE ALONG WITH BRIEF HEAVY RAIN INCREASING FAVORABLE
DYNAMICS.

TUESDAY WILL ADD A DEVELOPING SFC TROF/LEE CYCLONE OVR ERN WY INTO
THE MIX...INCREASING AND PUSHING MOISTURE WWD INTO THE ERN ZONES.
THE FOOTHILLS OF THE ERN SIDE OF THE  BIGHORN MOUNTAINS WILL BE THE
MOST SUSCEPTIBLE TO HEAVIER RAINFALL AMOUNTS...AND THERE WILL SOME
POSSIBILITY FOR ISOLATED AREAS OF FLASH FLOODING TUESDAY
AFTERNOON/EVENING.

WED/WED NIGHT...THE BC LOW/SW TROF WILL COMBINE WITH WHAT`S LEFT
FROM THE NRN CA DISTURBANCE...ADVECTING MOISTURE AND LIFT OVR THE
FA...ADDING TO LOCAL TERRAIN CONVERGENCE AS THEY FURTHER DESTABILIZE
THE ATMOSPHERE...ALLOWING FOR INCREASED CHANCES FOR PRECIPITATION
ACROSS THE FA...ALTHOUGH ON MORE OF AN ISOLATED TO WIDELY SCATTERED
BASIS...EXCEPT FOR THE YNP REGION WHO MAY SEE SCATTERED
PRECIPITATION.

.LONG TERM...THURSDAY THROUGH MONDAY

MEDIUM RANGE PERIOD STARTS WITH THE ABOVE MENTIONED SHORTWAVE
EXITING THE AREA WITH JUST A FEW LINGERING SHOWERS/TSTMS ACROSS
THE FAR NORTH BEFORE OUR UPPER HIGH IN THE NM/WRN TX VICINITY
REBUILDS AND RAISES OUR HEIGHTS AGAIN FOR FRIDAY. MONSOONAL
MOISTURE SURGE LOOKS SET TO MOVE NWD FRIDAY NIGHT INTO SATURDAY
WITH POTENTIAL EMBEDDED DISTURBANCE. AT THE SAME TIME...THE TROUGH
CURRENTLY OFF THE WEST COAST MAY FOLLOW THIS MONSOONAL SHORTWAVE
AND HIT THE W/NW LATE SAT/SAT NGT. BEST CHANCE OF SHOWERS/TSTMS
EXISTS DURING THIS PERIOD SIMILAR TO TODAY. RIDGE/HEIGHTS THEN
REBUILD SUNDAY INTO MONDAY WITH A DRIER SW FLOW BUT POSSIBLE
RIPPLES TO DEAL WITH.

&&

.AVIATION.../12Z ISSUANCE/

AN UPPER LEVEL LOW PRESSURE SYSTEM OVER NORTHERN UTAH WILL DRIFT NE
ACROSS WYOMING TODAY AND TONIGHT.  THIS SYSTEM WILL SPREAD SCT-NMRS
SHRA AND ISOLD TSRA VCNTY AND SOUTH OF INTERSTATE 80 12Z-18Z...TO
VCNTY AND SOUTH OF A KCPR-KRIW-KJAC LINE BY 00Z TUESDAY. AREAS OF
MVFR CONDITIONS WITH LCL IFR CONDITIONS ALONG WITH INCREASING MTN
OBSCURATIONS WILL DEVELOP ALONG THE LINE OF -SHRA/TSRA PUSHING
NORTH.  THE LINE OF SHRA WITH AREAS OF MVFR/LCL IFR CONDITIONS AND
FQT MTN OBSCURATIONS WILL BE MAINLY ALONG AND EAST OF THE
CONTINENTAL DIVIDE BY 12Z TUESDAY WITH A DRIER WESTERLY FLOW PUSHING
INTO SW WYOMING ALONG WITH IMPROVING CIGS.

&&

.FIRE WEATHER...

FIRE DANGER DECREASES TODAY...AND REMAINS ON THE LOWER SIDE THROUGH
AT LEAST WEDNESDAY...AS MOIST AND SOMEWHAT COOLER CONDITIONS
ACCOMPANY AN UPPER LEVEL DISTURBANCE THAT WILL ROTATE ACROSS THE
FORECAST AREA TODAY...EXITING LATER ON TUESDAY. MINIMUM RH VALUES
WILL INCREASE EVERYWHERE TODAY ABOVE CRITICAL LEVELS EXCEPT FOR THE
NORTHERN BIGHORN BASIN WHERE VALUES WILL STILL DROP INTO THE MID
TEENS (PERCENT). MONSOONAL-LIKE MOISTURE WILL FEED INTO THE REGION
OVER THE NEXT TWO DAYS...INCREASING CHANCES FOR SHOWERS AND EMBEDDED
THUNDER THIS MORNING ACROSS THE FAR SOUTHERN/SOUTHWESTERN
ZONES...SPREADING INTO THE CENTRAL AND NORTHERN FORECAST AREA LATER
TONIGHT...EVENTUALLY ENDING UP ACROSS EASTERN/NORTHEASTERN WYOMING
TUESDAY AFTERNOON AND EVENING. HEAVY RAIN IS EXPECTED AT TIMES.
LATER WEDNESDAY WILL SEE A RENEWED CHANCE FOR MORE RAINFALL ACROSS
THE REGION...ALTHOUGH ON A MORE ISOLATED TO WIDELY SCATTERED
BASIS.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
FLASH FLOOD WATCH FROM THIS AFTERNOON THROUGH LATE TONIGHT FOR
WYZ014-015-024.

&&

$$

SHORT TERM...BRAUN
LONG TERM...PS
AVIATION...AEM
FIRE WEATHER...BRAUN


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