Area Forecast Discussion
Issued by NWS Riverton, WY

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FXUS65 KRIW 012111
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
311 PM MDT FRI AUG 1 2014

.SHORT TERM...TONIGHT THROUGH SATURDAY

NOT A LOT OF CHANGE TO THE UPR LVLS W/ WV IMAGERY STILL SHOWING UPR
RIDGE JUST TO THE W WITH N/S AXIS STRETCHING FROM THE NRN ROCKIES
THRU THE GREAT BASIN...AND LARGE TROF/CLOSED SYSTEM ACROSS THE ERN
HALF OF THE CONUS. WY IS STUCK AGAIN UNDER WEAK NW FLOW...WITH A
WEAK UPR DISTURBANCE HEADED INTO THE STATE FROM THE NORTH. AT THE
SFC...MODEST LOW P ENTERING THE NERN PART OF WY WITH A WEAK HIGH OVR
THE NW. ISOLATED SHRA/TSRA JUST STARTING TO GO UP OVR THE NRN
MOUNTAINS.

TODAY/TONIGHT...WEAK UPR LVLS CONTINUE WITH THE WEAK SW MENTIONED
ABOVE MAKING ITS WAY INTO THE NRN CWA LATE THIS MORNING...AND
PUSHING A SFC LOW THRU THE ERN FA WITH WEAK FRONT. MONSOONAL
MOISTURE NOT REALLY A FACTOR TODAY...AS IT WILL BECOME AGAIN LATER
THIS WEEKEND. WHILE THE MOUNTAINS WILL SEE THE MAJORITY OF THE
CONVECTION THIS TODAY...THE ADDITION OF THE WEAK LOW/FRONT MOVING
ACROSS THE CWA WILL ALSO PROVIDE FOR A LITTLE LLVL FORCING
ELSEWHERE....MAINLY FROM NATRONA TO THE SW AND THROUGH SWEETWATER
COUNTIES BY THIS AFTERNOON...AND PRIMARILY OVR NEAR HIGHER TERRAIN
IN THOSE AREAS...SUCH AS CASPER MOUNTAIN...THE GREEN AND RATTLESNAKE
MOUNTAINS...ETC. HOWEVER...THE PRESENCE OF THE FRONTAL BOUNDARY IN
THIS AREA MAY GIVE AT LEAST VERY LOW END CHC FOR LIGHT
CONVECTION/PRECIP ACROSS ISOLATED LOWER ELEVATIONS IN THIS AREA.
OVERALL FORCING AND DYNAMICS IS QUITE WEAK AND WILL PRECLUDE STRONG
STORMS MOSTLY ALLOWING FOR ONLY SLOW MOVING PULSY POPCORN TYPE
STORMS WITH MAYBE SOME SMALL HAIL AND FREQUENT LIGHTNING.

SAT...WILL BE A GROUND HOG DAY OF FRIDAY IN MANY RESPECTS...WITH A
LITTLE LESS EMPHASIS ON CONVECTIVE COVERAGE IN THE WESTERN
MOUNTAINS. THE SFC LOW AND FRONT WILL BE WELL SOUTH AND INTO ERN CO
BY THIS POINT WITH LL ERLY FLOW E OF THE DIVIDE...BUT WRLY FLOW W OF
THE DIVIDE. A SLIGHT REORIENTATION OF THE UPR RIDGE AXIS EWD WITH
ALLOW FOR A LITTLE BETTER MID UPR FLOW AND CONVECTION SHOULD MOVE A
LITTLE QUICKER TO THE E OR SE...ONLY 10 TO 15 MPH INSTEAD OF 5 TO
10... BUT STILL A SHOWER OR TWO MAY JUST MAKE IT OFF A MOUNTAIN/HILL
AND AT LEAST INTO THE FOOTHILLS. STORMS SHOULD BEHAVE THEMSELVES FOR
ANOTHER DAY WITH STRONGER THUNDERSTORM DYNAMICS FOUND TO THE N AND
INTO CNTRL MT...BUT NOT THIS FAR SOUTH. POSSIBLE ISOLATED STRONG
STORM NEAR NRN BORDER IN/NEAR ABSAROKAS WHERE SHEAR IS SLIGHTLY
BETTER. OTHERWISE...A COUPLE OF DEG WARMER IS REALLY THE ONLY OTHER
DIFFERENCE FROM FRIDAY.

.LONG TERM...SATURDAY NIGHT THROUGH FRIDAY

WEAK OR DIRTY RIDGE OVER FORECAST AREA UNTIL SUNDAY NIGHT. TEMPERATURES
TO REMAIN VERY WARM WITH LITTLE OR NO PRECIPITATION FOR WEST CENTRAL
WYOMING. A FEW MOUNTAIN SHOWERS WILL PERSIST INTO SUNDAY EVENING.

PATTERN CHANGES ON MONDAY...THEN THROUGH THE WEEK AS PREVIOUSLY
ADVERTISED. MEDIUM RANGE MODELS BRING MORE MOISTURE AND CLOUDS TO
WEST CENTRAL WYOMING WITH WEST OF DIVIDE FIRST TO BE IMPACTED.
TIMING COULD BE A CHALLENGE ON MONDAY...BUT ATMOSPHERE LOOKS
UNSTABLE MOST AREAS BY MID AFTERNOON INTO THE EVENING.

TUESDAY COULD BE THE MOST ACTIVE WEATHER DAY ACROSS THE FORECAST
AREA. MODELS HINT AT DECENT SHORTWAVE AS AFOREMENTIONED RIDGE
FLATTENS OUT. THINKING AT LEAST SCATTERED THUNDERSTORMS ARE IN ORDER
FOR TUESDAY AFTERNOON AND EVENING WITH BEST QPF OVER HIGHER TERRAIN.

BEYOND TUESDAY...DECIDED MAINLY TO GO WITH THE GFS MODEL. SHORTWAVES
EJECT FROM WEAK MID/UPPER LEVEL TROUGH OVER THE WESTERN UNITED
STATES. THIS PATTERN SHOULD ALSO RESULT IN DIFFLUENT FLOW ALOFT THRU
EARLY THURSDAY. THEREFORE...THERE WILL BE A CHANCE FOR SHOWERS AND
THUNDERSTORMS ESPECIALLY WITH THE HEATING OF EACH DAY. SPEAKING OF
TEMPERATURES...THEY SHOULD BE NORMAL TO SLIGHTLY BELOW NORMAL DURING
THIS TIME. FRIDAY ALSO LOOKS COOL IF GFS IS THE MORE ACCURATE MODEL.


&&

.AVIATION.../00Z ISSUANCE/

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

VFR CONDITIONS WILL PREVAIL THROUGH THE PERIOD. ISOLATED TO WIDELY
SCATTERED SHOWERS AND STORMS WILL OCCUR FROM UNTIL 03Z TONIGHT IN THE
ABSAROKA...WIND RIVER AND BIG HORN MOUNTAINS. LITTLE IF ANY OF THIS
ACTIVITY WILL DIRECTLY EFFECT THE  LOWER ELEVATIONS OR TERMINAL
SITES...HOWEVER KCOD AND KLND WILL CARRY VCSH UNTIL 02Z. A FEW
SHOWERS WILL LINGER OVER THE BIGHORN MOUNTAINS TILL 08Z TONIGHT.
AFTER 19Z SATURDAY...ISOLATED TO WIDELY SCATTERED SHOWERS AND STORMS
CAN BE EXPECTED ONCE AGAIN OVER THE AREAS MOUNTAINS. BOTH KCOD AND
KCPR WILL CARRY VCTS FROM 19Z THROUGH THE END OF THE FORECAST.

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

VFR CONDITIONS WILL PREVAIL THROUGH THE PERIOD. ISOLATED TO
SCATTERED SHOWERS AND STORMS WILL OCCUR UNTIL 04Z TONIGHT IN THE
MOUNTAINS. LITTLE IF ANY OF THIS ACTIVITY WILL DIRECTLY EFFECT THE
TERMINAL SITES OR MOST LOWER ELEVATIONS EXCEPT AN ISOLATED VALLEY OR
TWO. WILL CARRY VCTS/SH FOR KJAC AND KPNA UNTIL 05Z. A FEW SHOWERS
WILL LINGER OVER THE MOUNTAINS UNTIL 06Z FRIDAY. BY 19Z
SATURDAY...ISOLATED TO WIDELY SCATTERED SHOWERS AND STORMS CAN BE
EXPECTED ONCE AGAIN OVER THE REGION`S MOUNTAINS. ONLY KJAC WILL
CARRY VCTS/SH FROM 20Z THROUGH THE END OF THE FORECAST.

&&

.FIRE WEATHER...

AN UPPER LEVEL DISTURBANCE AND WEAK SURFACE FRONT MOVING ACROSS THE
FORECAST AREA WILL BRING SLOW MOVING ISOLATED TO SCATTERED
THUNDERSTORMS MAINLY TO THE REGIONS MOUNTAINS AND A FEW ADJACENT
VALLEYS THIS AFTERNOON AND THROUGH EVENING. TEMPERATURES WILL BE
SEASONABLY WARM WITH MINIMUM RH VALUES RANGE FROM 20 TO 40 PERCENT
FOR MOST LOCATIONS EXCEPT THE BIG HORN BASIN WHICH COULD SEE RH
VALUES AS LOW A 15 PERCENT IN PLACES. LITTLE WIND IS EXPECTED
HOWEVER. SATURDAY...A SIMILAR SET UP TO THAT ON FRIDAY WITH A REPEAT
OF SHOWERS AND THUNDERSTORMS MAINLY OVER THE HIGH TERRAIN OF THE
REGION. HIGH TEMPERATURES WILL WARM A FEW MORE DEGREES OVER THOSE OF
TODAY...HOWEVER MINIMUM RH VALUES WILL REMAIN ABOUT THE SAME AND
WIND WILL ALSO REMAIN ON THE LIGHTER SIDE...WITH GENERALLY
EASTERLIES EAST OF THE DIVIDE AND WESTERLIES WEST OF THE DIVIDE.
SUNDAY AND INTO THE BEGINNING OF THE NEXT WORK WEEK...MONSOONAL
MOISTURE WILL START A RETURN...BRINGING ANOTHER DAY OF SHOWERS AND
THUNDERSTORMS TO THE MOUNTAINS SUNDAY. MONDAY AND TUESDAY LOOK TO
BOTH COOL OFF AND INCREASE MOISTURE WITH MUCH BETTER CHANCES FOR FOR
SIGNIFICANT RAINFALL ACROSS THE ENTIRE FORECAST AREA. WINDS MAY PICK
UP A BIT SUNDAY AFTERNOON ACROSS THE SOUTH AS A SURFACE LOW PRESSURE
SYSTEM DEVELOPS ACROSS THE SOUTHWEST REGION.

&&

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

$$

SHORT TERM...BRAUN
LONG TERM...KPL
AVIATION...BRAUN
FIRE WEATHER...BRAUN




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