Area Forecast Discussion
Issued by NWS Riverton, WY

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FXUS65 KRIW 201704
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1104 AM MDT SUN JUL 20 2014

.SHORT TERM...SUNDAY THROUGH TUESDAY NIGHT

IT LOOKS LIKE ANOTHER HOT DAY ACROSS THE COWBOY STATE WITH A RIDGE
OF HIGH PRESSURE CONTINUING TO CONTROL THE WEATHER. HOWEVER THERE
ARE SOME CHANGES TO THE PATTERN OF THE PAST COUPLE OF DAYS.
SATELLITE IMAGERY SHOWS SOME MID LEVEL MOISTURE STARTING TO MOVE IN
FROM THE SOUTH ACROSS UTAH. AT THE SAME TIME A WEAK SHORTWAVE WILL
APPROACH THE AREA AND BRING A BIT MORE INSTABILITY TO THE AREA. THE
RESULT WILL BE FOR AN INCREASING CHANCE OF SHOWERS AND THUNDERSTORMS
FOR PORTIONS OF WESTERN AND CENTRAL WYOMING. HOWEVER...IT WILL TAKE
A WHILE TO MOISTEN THE ATMOSPHERE SO MOST OF THE DAY SHOULD BE DRY.
CONTINUITY LOOKED REASONABLE FOR COVERAGE OF THE CONVECTION THIS
AFTERNOON SO WE MADE ONLY MINOR TWEAKS MAINLY TO ADD TIMING.
MEANWHILE...EXPECT MAINLY DRY WEATHER ACROSS THE NORTHEASTERN HALF
OF THE COUNTY WARNING AREA. WITH THE BEST MOISTURE EXPECTED TO MOVE
ACROSS WESTERN WYOMING TONIGHT WE KEPT THE CHANCE OF THUNDERSTORMS
GOING THROUGH THE OVERNIGHT. WITH THE HOT TEMPERATURES AND GUSTY
WINDS WE HAVE KEPT THE RED FLAG WARNING FOR THIS AFTERNOON AS WELL.

THE FORECAST FOR MONDAY IS BASED ON SOMETHING SIMILAR TO THE OLD
SING ALONG CARTOONS WHERE THEY STAY FOLLOW THE BOUNCING BALL. ONLY
HERE IT IS FOLLOW THE PRECIPITABLE WATER VALUES...OR PWAT OR PW
VALUES...THE ABBREVIATION METEOROLOGISTS USE TO CONFUSE THE PUBLIC
SINCE WE MUST HAVE A CONTRACTION OR ACRONYM FOR EVERYTHING.
ANYWAY...THE BEST LIFT AND PRECIPITABLE WATER VALUES SHIFT ACROSS
NORTHERN WYOMING SO THE CHANCE OF THUNDERSTORMS WILL SHIFT THERE AS
WELL. AS FOR TEMPERATURES...EXPECT A LITTLE COOLING WITH MORE CLOUD
COVER BUT IT WILL STILL BE ABOVE NORMAL FOR MOST LOCATIONS.

BY TUESDAY CONVECTION SHOULD BECOME A BIT MORE ISOLATED AS HEIGHTS
RISE A BIT MORE AS THE RIDGE BUILDS NORTHWARD JUST A BIT. THIS WILL
ALSO SHOVE THE DEEPER MOISTURE FURTHER NORTHWARD AS WELL. AS A
RESULT WE HAVE CONFINED THE CHANCE OF THUNDERSTORMS TO THE NORTHERN
MOUNTAINS. CONTINUITY HAD THIS REPRESENTED FAIRLY WELL SO WE MADE
FEW CHANGES.

.LONG TERM...WEDNESDAY THROUGH SUNDAY

GFS/ECMWF MODELS SHOW SOME MID AND UPPER LEVEL MOISTURE IN THE SW
FLOW ALOFT WEDNESDAY INTO WED NIGHT. THERE MAY BE A WEAK DISTURBANCE
IN THE FLOW AS WELL. WILL KEEP ISOLATED STORMS ACROSS THE NORTH AND
EAST ZONES...YET A STRAY STORM COULD OCCUR IN THE SOUTH AS WELL.
WILL SEE HOW THIS PLAYS OUT IN TIME. A WEATHER SYSTEM IS FORECAST TO
MOVE ACROSS THE PACIFIC NW STATES WED NIGHT. THE MAIN ISSUE IS THE
TRACK OF THIS SYSTEM THURS AND FRI. THE GFS IS STILL FARTHER SOUTH
THAN THE ECMWF TRACK. THIS DIFFERENCE INFLUENCES THE CHANCE OF
STORMS OVER THE NORTH AND HOW STRONG THE COLD FRONT WILL BE THAT
MOVES INTO THE NORTH THURSDAY NIGHT. THIS IN TURN IMPACTS THE HIGHS
ON FRIDAY OVER THE NORTH AND CENTRAL ZONES. FOR NOW WILL HAVE
ISOLATED STORMS OVER THE NORTH THURS PM AND NIGHT AND DRY ELSEWHERE.
FRIDAY WILL BE DRY FOR THE WHOLE AREA. THE DIFFERENCE IN STORM TRACK
ALSO INFLUENCES THE WEATHER PATTERN NEXT SATURDAY AND SUNDAY. THE
GFS MODEL DIGS THE SYSTEM INTO THE MIDWEST BY SUNDAY WHILE THE ECMWF
IS SLOWER AND HAS IT OVER THE UPPER GREAT LAKES SUNDAY AFTERNOON.
THE FLOW ALOFT IS TO BECOME NW AGAIN NEXT SATURDAY AND SUNDAY BUT
THE GFS IS SHARPER WITH THE FLOW AND HAS COOLER 700MB TEMPS EAST OF
THE DIVIDE. THE ECMWF IS LESS AMPLIFIED AND HAS A LITTLE WARMER
700MB TEMPS. THIS INFLUENCES THE HIGHS FOR NEXT SAT/SUN. THE GFS IS
DRY BOTH DAYS WHILE ECMWF TRIES TO BRING IN MID/UPPER LEVEL MOISTURE
FOR NEXT SUNDAY AND ISOLATED STORMS. WILL KEEP NEXT WEEKEND DRY FOR
NOW AND SEE HOW THIS LOOKS IN THE COMING MODEL RUNS.

AS FOR THE HIGH TEMPS...HOT WEDNESDAY. REMAINING HOT CENTRAL AND
SOUTH THURSDAY WITH COOLER HIGHS OVER THE NW AND NORTH AS THE COLD
FRONT MAKES IT INTO THOSE AREAS. HIGHS FRIDAY COOLER MOST PLACES
WITH THE BEST COOLING NOTED OVER THE NORTH AND NORTHEAST ZONES. HAVE
MADE ADJUSTMENTS TO THE FRIDAY HIGHS. HIGHS SATURDAY A LITTLE WARMER
SOUTH AND SOUTHWEST WITH LITTLE CHANGE EAST OF THE DIVIDE. THEN A
LITTLE WARMER ALL AREAS NEXT SUNDAY. THIS THINKING LEANS MORE TOWARD
THE WARMER ECMWF MODEL FOR NOW. BOTTOM LINE...SUMMER HEAT AND MAINLY
DRY IN THE EXTENDED PERIOD.

.AVIATION.../18Z ISSUANCE/

EXPECT VFR CONDITIONS THROUGH 18Z MONDAY AT ALL TERMINALS. MAIN
SMOKE PLUMES THAT HAVE BEEN CAUSING SOME LOCALIZED 6SM IN THE
MORNINGS WILL SHIFT NORTH OF THE STATE TODAY AS FLOW ALOFT BACKS
MORE TO THE SOUTHWEST. MOISTURE THAT HAS REMAINED JUST SOUTH OF
THE WYOMING BORDER WILL PUSH SLOWLY NORTHEAST INTO WYOMING TODAY.
BEST CHANCE FOR ISOLATED SHOWERS AND STORMS WILL BE SOUTHWEST OF A
KBPI-KRKS LINE. HAVE OPTED TO LEAVE ANY MENTION OF VCSH OR VCTS
OUT OF THOSE TERMINALS AS CONVECTION STILL LOOKS TO BE LIMITED.
INSTABILITY NOT IMPRESSIVE AND DYNAMICS ARE LACKING...SO ANY
CONVECTION WILL BE DEPENDENT UPON DIURNAL HEATING. BETTER MOISTURE
OVER CA/NV WILL CIRCULATE NORTHEAST AND REACH THE FAR WEST AROUND
06Z/MONDAY. HAVE INCLUDE SOME LATE NIGHT VCSH AT KJAC TO ACCOUNT
FOR THIS AREA OF MOISTURE AND APPROACHING SHORTWAVE. WEST TO
SOUTHWEST WIND WILL AGAIN BLOW 15G30KTS TODAY IN THE CORRIDOR FROM
KRKS-KCPR BEGINNING BETWEEN 17Z-19Z. OTHER TERMINALS CAN EXPECT
INCREASING WIND BETWEEN ABOUT 19Z-21Z WITH SPEEDS 12G24KTS. KWRL
TO REMAIN LIGHT AND VARIABLE THROUGH THE FORECAST PERIOD. WINDS
WILL DECREASE WITH THE SETTING SUN BETWEEN 02Z AND 03Z/SUNDAY.

.FIRE WEATHER...

THE CONTINUED COMBINATION OF HOT TEMPERATURES...LOW RELATIVE
HUMIDITY AND GUSTY WINDS WILL BRING MORE CRITICAL FIRE WEATHER TO
SWEETWATER AND NATRONA COUNTIES. AS A RESULT...THE RED FLAG WARNING
WILL BE CONTINUED. OTHERWISE...A SURGE OF MOISTURE WILL MOVE
NORTHWARD INTO SOUTHERN WYOMING AND BRING ISOLATED TO WIDELY
SCATTERED LATE DAY AND EVENING THUNDERSTORMS. THIS MOISTURE WILL
SURGE NORTHWARD AT NIGHT AND KEEP THE CHANCE OF THUNDERSTORMS GOING
IN WESTERN WYOMING AT NIGHT. EXPECT ANOTHER HOT DAY FOR MONDAY WITH
THE CHANCE OF THUNDERSTORMS ACROSS NORTHERN WYOMING. CRITICAL FIRE
WEATHER IS STILL POSSIBLE.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
RED FLAG WARNING UNTIL 8 PM MDT THIS EVENING WYZ279-280.

&&

$$

SHORT TERM...HATTINGS
LONG TERM...AR
AVIATION...C.BAKER
FIRE WEATHER...HATTINGS






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