Area Forecast Discussion
Issued by NWS Riverton, WY

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000
FXUS65 KRIW 031917
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
117 PM MDT FRI JUL 3 2015

.SHORT TERM...TONIGHT THROUGH SATURDAY

HIGH PRESSURE REMAINS OVER THE NORTHERN AND CENTRAL HIGH PLAINS
WITH LOW PRESSURE OVER THE GREAT BASIN RESULTING IN NORTHEAST LOW
LEVEL FLOW...WITH COOLER AND MORE MOIST AIR OVER THE NORTH AND
EAST...AND DRIER AND WARMER AIR OVER THE SOUTHWEST. ISOLATED TO
SCATTERED SHOWERS AND THUNDERSTORMS WILL DEVELOP ALONG AND EAST OF
THE CONTINENTAL DIVIDE AND OVER THE BIGHORN MOUNTAINS THROUGH THE
EVENING WITH A FEW BECOMING STRONG ENOUGH TO MOVE OFF THE
MOUNTAINS AND INTO THE MORE STABLE AIR IN THE LOWER ELEVATIONS OF
THE WIND RIVER AND BIGHORN BASINS AND THE EASTERN PLAINS OF
JOHNSON AND NATRONA COUNTIES. CLEARING WILL BE WIDESPREAD
OVERNIGHT AND THROUGH SATURDAY MORNING. THE AIR MASS WILL BE
WARMER AND DRIER ON SATURDAY WITH ANOTHER ROUND...WITH LESS
COVERAGE...OF AFTERNOON AND EVENING SHOWERS AND THUNDERSTORMS
ALONG AND EAST OF THE CONTINENTAL DIVIDE. FEWER STORMS ARE
EXPECTED OVERALL AND ESPECIALLY IN THE LOWER ELEVATIONS.

.LONG TERM...SATURDAY NIGHT THROUGH FRIDAY

BEGINNING OF FCST...QUITE A PROTECTIVE CAP IN PLACE WITH FEW
THUNDERSTORMS ABLE TO INITIATE EXCEPT OVR THE HIGHEST PEAKS IN THE
AREA AND PERHAPS OVR A DEVELOPING AREA OF LOW PRESSURE ACROSS THE
SRN FA AND ITS ASSOCIATED DEVELOPING WARM FRONT INTO SRN NATRONA
COUNTY. RELATIVELY LOW CAPE AND SHEAR... 300 - 700 J/KG AND 20 KTS
OR LESS RESPECTIVELY...WILL YIELD ONLY ISOLATED MODEST THUNDER IN
THESE AREAS WITH GUSTY WINDS THE MOST LIKELY CULPRIT.

SUNDAY...A COUPLE OF UPR LVL WAVES EMBEDDED IN BOTH THE THE SRN FLOW
AROUND THE HIGH AND THE NRN FLOW WILL COME TOGETHER AND PROVIDE EXTRA
MOISTURE AND LIFT ABOVE A DIVING CANADIAN COLD FRONT THAT WILL MOVE
S ACROSS THE FA DURING THE DAY. ADDITIONALLY...THE SFC LOW THAT WAS
DEVELOPING OVR SRN WY WILL BE INSPIRED TO JUMP EWD...SPINNING UP
INTO A LEE CYCLONE ACROSS THE HIGH PLAINS OF SERN WY AND NERN CO.
MUCH COOLER WITH CHCS FOR PRECIP...IN THE FORM OF STRONG SHOWERS AND
EMBEDDED THUNDERSTORMS...INCREASING OVR THE ENTIRE FA BY SUNDAY
AFTERNOON. DYNAMICS WILL BE CHARACTERIZED BY LONG SKINNY CAPE WITH
COPIOUS AMOUNTS OF MOISTURE...PWS AT OR IN EXCESS OF 1 INCH FOR MOST
ALL LOCATIONS...AND DEEP SHEAR AROUND 30 KTS PLUS/MINUS. MOST STORMS
E OF THE DIVIDE WILL HAVE THE POTENTIAL TO ROTATE AND MAINTAIN
THEMSELVES FOR A WHILE. ALTHOUGH STORM MOVEMENT SHOULD RUN 20 TO 30
KTS...EXPECT EMBEDDED CORES WITH VERY HEAVY RAIN...AND SMALL
HAIL...POSSIBLY LOTS OF IT...BRINGING A POSSIBILITY OF SOME FLASH
FLOODING. THE LOCATION OF THE DEVELOPING LEE CYCLONE WILL PIN THE
AREA FOR STRONGEST STORM POTENTIAL NEARING SEVERE ACROSS NATRONA
COUNTY...PARTICULARLY THE ERN/SRN HALF...WHERE ANYTHING WILL BE
POSSIBLE...ESPECIALLY BY MID TO LATE AFTERNOON. THRU SUNDAY
NIGHT...WITH VERY MOIST N TO NERLY LOW TO MID LVL FLOW WRAPPING
AROUND THE CYCLONE...AND THE POTENTIAL FOR SOME MID LVL
FRONTOGENESIS MOVING OVR THE ERN ZONES IN RESPONSE TO ANOTHER
EMBEDDED UPR WAVE...AN AREA OF SOME CONCERN WILL BE THE AREA ERN
SLOPES OF THE BIGHORNS...ESPECIALLY THE SRN PORTION FROM RED WALL TO
KAYCEE AND POINTS SWD TO THE RATTLESNAKE RANGE WHERE LL CONVERGENCE
WILL BE MAXIMIZED OVERNIGHT.

MONDAY MORNING...HEAVY SHOWERS WILL CONTINUE ALONG AND AHEAD OF A
SECONDARY FRONT THAT LOOKS TO HEADED THRU THE CNTRL AND SRN FA. SOME
MODEST SHRA/TSRA REDEVELOPMENT WILL OCCUR OVR THE HIGHER MOUNTAINS
RINGING THE BASINS BY MONDAY AFTERNOON. HOWEVER...THE MOST LIKELY
AREA FOR SHOWERS AND ISOLATED THUNDER WILL OCCUR OVR THE SRN FA
ALONG AND BEHIND A NOW SLOWING FRONT.

THRU THE END OF THE FCST...SEASONALLY COOL WITH A SLOW WARMING TREND
AND CONTINUED CHANCES FOR PRECIP WILL ACCOMPANY AN EQUALLY SLOW
TRANSITION FROM NW FLOW TO...FLAT...AND ON TO MODEST RIDGING BY THE
END OF THE FCST. DIFFERENCES BETWEEN LR MDLS AREA PLENTY BUT NOT
HUGELY IMPACTFUL. BLEND OF CURRENT TIMING FOR THE UPR LVL`S
EVOLUTION AND POSSIBLE EJECTING EMBEDDED WAVES PUTS A LITTLE BETTER
CHANCE FOR AFTERNOON/EVE PRECIP E OF THE DIVIDE TUE...WEST OF THE
DIVIDE WED AND THU...PUSHING NWD BY FRIDAY. THE STRONGEST STORMS FOR
THIS PORTION OF THE FCST LOOK TO FIND THEMSELVES OVR NATRONA TO ERN
FREMONT COUNTY LATER ON TUESDAY...BUT STILL REMAIN BELOW SEVERE
LEVELS FOR THE MOST PART.

&&

.AVIATION.../00Z ISSUANCE/

AN UPPER LEVEL DISTURBANCE WILL PUSH SE ACROSS NORTHERN WYOMING
THIS EVENING. ISOLD-WDLY SCT -TSRAGS MAINLY VCNTY AND NORTH OF A
KJAC- KLND-KCPR LINE THROUGH 06Z...WITH DRIER AND MORE STABLE
CONDITIONS TO THE SOUTH. BRIEF MVFR CONDITIONS WILL BE POSSIBLE
WITH ANY STORMS. MOST OF THIS ACTIVITY WILL CLEAR THE AREA OR
DISSIPATE WITH SUNSET...WITH SKC-FEW FL150-200 PREVAILING AFTER
06Z SATURDAY. CLEARING WILL BE WIDESPREAD AFTER 06Z. THE AIR MASS
WILL BE DRIER AND MORE STABLE ON SATURDAY. ISOLATED MOUNTAIN
SHOWERS AND THUNDERSTORMS WILL OCCUR FROM 19Z - 00Z SUNDAY ALONG
AND EAST OF THE CONTINENTAL DIVIDE AND OVER THE BIGHORN MOUNTAINS.

&&

.FIRE WEATHER...

HIGH PRESSURE REMAINS OVER THE NORTHERN AND CENTRAL HIGH PLAINS
WITH LOW PRESSURE OVER THE GREAT BASIN RESULTING IN NORTHEAST LOW
LEVEL FLOW...WITH COOLER AND MORE MOIST AIR OVER THE NORTH AND
EAST...AND DRIER AND WARMER AIR OVER THE SOUTHWEST. ISOLATED TO
SCATTERED SHOWERS AND THUNDERSTORMS WILL DEVELOP ALONG AND EAST OF
THE CONTINENTAL DIVIDE AND OVER THE BIGHORN MOUNTAINS THROUGH THE
EVENING WITH A FEW BECOMING STRONG ENOUGH TO MOVE OFF THE
MOUNTAINS AND INTO THE MORE STABLE AIR IN THE LOWER ELEVATIONS OF
THE WIND RIVER AND BIGHORN BASINS AND THE EASTERN PLAINS OF
JOHNSON AND NATRONA COUNTIES. CLEARING WILL BE WIDESPREAD
OVERNIGHT AND THROUGH SATURDAY MORNING. THE AIR MASS WILL BE
WARMER AND DRIER ON SATURDAY WITH ANOTHER ROUND...WITH LESS
COVERAGE...OF AFTERNOON AND EVENING SHOWERS AND THUNDERSTORMS
ALONG AND EAST OF THE CONTINENTAL DIVIDE. FEWER STORMS ARE
EXPECTED OVERALL AND ESPECIALLY IN THE LOWER ELEVATIONS.

&&

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

$$

SHORT TERM...C.BAKER
LONG TERM...BRAUN
AVIATION...C.BAKER
FIRE WEATHER...C.BAKER


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