Area Forecast Discussion
Issued by NWS Riverton, WY

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000
FXUS65 KRIW 300559
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1158 PM MDT FRI AUG 29 2014

.SHORT TERM...TONIGHT AND SATURDAY (ISSUED AT 250 PM MDT)

MORNING SHORTWAVE IS MOVING OFF TO THE EAST WITH SHALLOW FRONTAL
BOUNDARY HANGING ACROSS THE NERN ZONES. WEAK CONVECTION FIRING
OVER THE HIGHER TERRAIN. A FEW STORMS MAY TRY AND COME OFF THE
MOUNTAINS INTO THE EARLY EVENING. OTHERWISE...WE AWAIT THE NEXT
DISTURBANCES TO AFFECT THE AREA THROUGH SATURDAY. MAIN SHORTWAVE
IS MOVING INTO THE PACNW AND THIS WILL BE THE ONE TO PUSH A STRONG
FRONT ACROSS THE AREA DURING THE DAY SATURDAY. LEANING TOWARDS THE
FASTER GFS SOLUTION WHICH PUSHES THE FRONT ACROSS MOST OF THE AREA
BY LATE AFTERNOON. THE NAM IS SLOWER AND HOLDS OFF IN THE SERN
ZONES UNTIL AFTER MAX HEATING. EVEN WITH THAT SAID...THE MODELS
ARE PICKING UP ON THE MOISTURE ENCROACHING FROM THE WEST. WE
APPEAR TO HAVE TWO MOISTURE SOURCES NOW MOVING THROUGH NRN CA AND
INTO NV ATTM. THE NRN PIECE OF THIS STILL SEEMS TO BE OLD
HURRICANE LOWELL MOISTURE WHILE THE BIGGER `BLOB` IS SOME OF OLD
HURRICANE MARIE`S MOISTURE. IT`S LOOKING LIKE THIS MOISTURE WILL
MOVE INTO THE SW TOWARDS MORNING AND THEN ACROSS THE SOUTH BY
MIDDAY WITH MAINLY LGT SHOWERS. THE COMBINATION OF THAT...THE
APPROACHING FRONT AND LEFT NOSE OF THE JET WILL LIKELY GET
ANOTHER ROUND OF CONVECTION GOING FURTHER NORTH TOO INTO NWRN WYO.
AS THE DAY WEARS ON...HEATING AT THE SURFACE...COOLING IN THE MID
LEVELS...FRONTAL BOUNDARY AND INCREASING JET STREAK DYNAMICS WILL
LIKELY LEAD TO A FEW STRONGER THUNDERSTORMS OVER THE WEST SATURDAY
AFTERNOON. COULD SEE SOME OF THESE STRONGER THUNDERSTORMS ALSO
ACROSS THE FAR NORTH AS NEW FRONTAL BOUNDARY SAGS SOUTH INTO THE
AREA. FURTHER SOUTH...SHOWERS AND THUNDERSTORMS WILL BE ON THE
INCREASE ALONG THE FRONT WITH INCREASING SW WINDS AHEAD OF IT AT
SPEEDS OF 25 TO 40 MPH QUITE COMMON. WARM AHEAD OF THE FRONT BUT
LIKELY NOT AS WARM AS IT COULD BE WITH EXPECTED FASTER FRONTAL
TIMING.

.LONG TERM...MONDAY THROUGH FRIDAY
OVERALL...LR MDLS IN FAIRLY GOOD AGREEMENT AT BOTH UPR AND LWR LVLS
THROUGHOUT THE FORECAST PERIOD. STUNNED.

SAT NIGHT...THE PROGRESSIVE NATURE OF THE UPR LVLS WILL SPREAD MUCH
STRONGER UPR FLOW OVERHEAD RESULTING IN INCREASED NET UPWARD LIFT
THRU THE DAY SAT...CONTINUING INTO THE EVENING. THIS WILL GREATLY
IMPROVE CONVECTIVE CHANCES ALONG WITH SOME GROWTH POTENTIAL INTO
THE EVENING PERIOD...WITH A FEW STRONG STORMS EXPECTED. STRONGER
STORMS WILL BE CHARACTERIZED BY MOSTLY SMALL HAIL AND STRONGER GUSTY
WINDS ACROSS THE NRN ZONES...WITH MORE OF A STRONG WIND GUST/BRIEF
HEAVY RAIN SITUATION OVER THE SRN ZONES. SHEAR WILL MAINLY BE
AVAILABLE IN THE FORM OF SPEED SHEAR W/ HEIGHT THIS DAY...AS
INCREASING UNIDIRECTIONAL SW FLOW OVERRUNS THE CWA...LENDING ITSELF
TO AMBIENT GUSTY WEST TO SOUTHWEST WINDS TO BEGIN WITH. PUTTING ANY
THUNDERSTORMS INTO THIS ATMOSPHERE WILL ONLY INCREASE THE LIKELIHOOD
FOR A FEW STRONG TO MARGINALLY SVR GUSTS AS STORMS RACE TO THE ENE
AT 30 PLUS MPH. SIGNIFICANT FLOODING RAINFALL DOES NOT LOOK TO BE A
PROBLEM WITH THIS EVENT.

SUNDAY AND MONDAY...THE UPR TROF CONTINUES CROSSING THE STATE FROM W
TO E...WITH MUCH COOLER CONDITIONS FOR SURE AND CONTINUED GUSTY W TO
WSW WINDS ACROSS THE SRN FA AND HIGHER MOUNTAIN RIDGE. PRECIP CHCS
WILL ALSO BE ENDING FROM W TO E THROUGH THE DAY SUNDAY...WITH
ANOTHER SMALL SHOT AT PRECIP SUNDAY NIGHT AS A SMALL EMBEDDED SW
TRAVELS QUICKLY THRU THE FLOW AND OVR NRN WY. MONDAY WILL SEE THE
LAST CONVECTIVE CHC FOR PRECIP FOR A FEW DAYS...AND EVEN THEN JUST
ACROSS THE NRN REACHES OF THE CWA...AS THE EVER WIDENING AND EWD
MOVING UPR TROF TAKES OVR MUCH OF THE CONUS AND THE WEST GIVES WAY
TO FLAT RIDGING.

TUESDAY THRU FRIDAY... THE FA ENTERS A MODEST WARMING AND DRYING
PERIOD WITH TEMPS RETURNING TO LOW END SEASONAL...WITH ONLY EVER SO
SLIGHT CHCS FOR DIURNAL MOUNTAINS ISO SHRA/TSRA LATER
WEDNESDAY...INCREASING TO PERHAPS WIDELY SCATTERED MOUNTAIN
CONVECTION THU AFTERNOON...THEN ISOLATED TO WIDELY SCATTERED ACROSS
THE MOUNTAINS...AND NRN/CNTRL BASINS ONE FRIDAY...AS THE FA BEGINS
TO FEEL THE EFFECTS OF THE NEXT IN A CONSTANT PROGRESSION OF UPR LVL
TROFS BEGINS TO DIG INTO THE WRN CONUS AND MORPH THE UPR LVLS OVR WY
FROM NEAR ZONAL TO SWRLY. THIS WILL ALSO GENERATE AT LEAST OF COUPLE
OF LEE SIDE FRONTS BETWEEN WED AND FRI...ALSO HELPING IN
FORCING/FOCUSING. THE LIMITING FACTOR LATE WITH THE LATE WEEK
ACTIVITY WILL BE AVAILABLE MOISTURE...OR RELATIVE LACK THEREOF.
HOWEVER...THEE ARE INDICATIONS THAT BEYOND THIS FORECAST PERIOD THE
WEST ONCE AGAIN GETS REINVIGORATED WITH MOISTURE FROM THE TROPICAL
SOUTH AS THE UPR LVL PATTERN WITH DEEP TROFING W AND A STRONG SRN
CONUS HIGH SQUEEZE MOISTURE BACK INTO THE ROCKIES.

.AVIATION.../06Z ISSUANCE/

ISOLATED SHOWERS AND THUNDERSTORMS WILL CONTINUE ACROSS THE WEST
OVERNIGHT AHEAD OF AN APPROACHING COMPLEX UPPER TROUGH.  THE INITIAL
ENERGY WITH THIS SYSTEM WILL PUSH INTO THE WEST LATE SATURDAY
MORNING AND ACROSS CENTRAL WYOMING SATURDAY AFTERNOON.  THE SYSTEM
WILL DRIVE A COLD FRONT SOUTH ACROSS NORTH CENTRAL WYOMING...AND
THIS BOUNDARY WILL BE THE FOCUS FOR STRONGER THUNDERSTORMS SATURDAY
AFTERNOON...PRIMARILY VCNTY AND NORTH OF A KDUB-KWRL-50SM S KBYG
LINE.  SOME OF THESE STORMS WILL BE CAPABLE OF MARGINALLY SEVERE
HAIL AND BRIEF MVFR/IFR CONDITIONS.  SOUTH OF THE FRONT...WSW WINDS
AT 20-30KTS WILL PREVAIL IN THE AFTERNOON ALONG WITH WIDELY SCT
THUNDERSTORMS.  THE MAIN HAZARD WITH THESE STORMS WILL BE ERRATIC
OUTFLOW WIND GUSTS NEAR 40KTS.   MOST OF THIS ACTIVITY WILL MOVE
EAST INTO THE HIGH PLAINS SATURDAY EVENING.  THE BACK SIDE OF THIS
TROUGH WILL PUSH INTO WESTERN WYOMING EARLY SUNDAY MORNING SPREADING
SCT-NMRS SHRA/ISOLD TSRA AND HIGHER MTN OBSCURATIONS ACROSS THE WEST
AND NORTH...OR PRIMARILY VCNTY AND W-N OF A KPNA-KCOD-KBYG LINE.

.FIRE WEATHER...
ISOLATED THUNDERSTORMS AROUND AND NEAR THE MOUNTAINS TODAY WITH A
FEW SHOWERS POSSIBLE OVERNIGHT...ESPECIALLY IN THE FAR WEST. A NEW
WEATHER SYSTEM WILL BRING AN INCREASING CHANCE OF SHOWERS AND
THUNDERSTORMS FROM WEST TO EAST SATURDAY WITH INCREASING SOUTHWEST
WIND AHEAD OF IT. THERE WILL BE ELEVATED FIRE WEATHER CONDITIONS
IN THE SWEETWATER...FREMONT...NATRONA AND SOUTHERN JOHNSON
COUNTIES AHEAD OF THE COLD FRONT DUE TO STRONG SOUTHWEST WIND OF
25 TO 40 MPH WITH A BRIEF PERIOD WHEN RH`S MAY DROP INTO THE UPPER
TEENS. HOWEVER...THE COLD FRONT AND EVEN SOME SHOWERS WILL MOVE
INTO THE CENTRAL PART OF THE AREA BY LATE MORNING TO AROUND NOON
WITH HIGHER RH`S AND SOME SHOWER AND ISOLATED THUNDERSTORM
ACTIVITY. OTHER AREAS WILL HAVE HIGHER RH`S BUT STILL A PERIOD
WINDY CONDITIONS AND SOME THUNDERSTORMS.

&&

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

&&

$$

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









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