Area Forecast Discussion
Issued by NWS Riverton, WY

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS65 KRIW 302037
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
237 PM MDT SUN AUG 30 2015

.SHORT TERM...TONIGHT THROUGH MONDAY

A TROUGH AND COLD FRONT CONTINUE TO TRACK EASTWARD ACROSS THE
INTERMOUNTAIN WEST. THE COLD FRONT IS LYING NEAR THE MONTANA BORDER
AND IS EXPECTED TO SURGE SOUTHWARD AGAIN AROUND SUNSET WITH THE
MAIN PUSH ARRIVING TOWARD MIDNIGHT...THOUGH THE TIMING ON COLD
FRONTS CAN BE TRICKY AS THEY OFTEN MOVE FASTER THAN EXPECTED. WE
CAN CONTINUE TO EXPECT RED FLAG CONDITIONS SOUTH OF THE FRONT AND
MUCH COOLER AND MOIST CONDITIONS TO THE NORTH THROUGH THE EARLY
EVENING HOURS.

THERE IS ALSO SOME DECENT LIFT ON THE FRONT SIDE OF THIS TROUGH
WITH JET SUPPORT ALOFT...A THETA E RIDGE LYING APPROXIMATELY FROM
FLAMING GORGE TO KAYCEE...AND QG FORCING ARRIVING LATER IN THE
EVENING. AREAS WITH DECENT LOW LEVEL MOISTURE IN PLACE...ACROSS
THE WEST AND THE SOUTH...AND ON THE OTHER SIDE OF THE FRONT WILL
SEE WET THUNDERSTORMS AND AREAS LIKE THE SOUTHERN BIGHORN
BASIN...NATRONA COUNTY AND FREMONT COUNTY WILL SEE MAINLY DRY
THUNDERSTORMS THROUGH SUNSET...SHOWERS AND STORMS HAVE A BETTER
CHANCE OF PRODUCING A WETTING RAIN THEREAFTER.

MONDAY WILL BE DRY AGAIN BUT LESS WINDY AS WE LOSE THE GRADIENT AT
THE SURFACE AND ALOFT. TEMPERATURES WILL BE CLOSER TO SEASONAL
NORMS WITH HIGHS IN THE LOW TO MID 80S EAST...MID TO UPPER 70S
WEST AND SOUTH. A PLUME OF MOISTURE ACROSS COLORADO COULD BEGIN TO
POKE NORTH INTO SOUTHERN SWEETWATER COUNTY WITH A FEW STRAY
AFTERNOON STORMS POSSIBLE OTHERIWSE IT WILL BE DRY AND RAIN FREE.

.LONG TERM...MONDAY NIGHT THROUGH SUNDAY

MEDIUM-RANGE FORECAST MODELS ARE CONSISTENT AND AGAIN IN FAIRLY GOOD
AGREEMENT THROUGH THE FORECAST PERIOD. WEST-SOUTHWEST FLOW ALOFT ON
TUESDAY WILL BACK TO THE SOUTHWEST WEDNESDAY AND THURSDAY AS A
TROUGH DEEPENS OVER THE PACIFIC NORTHWEST. LIMITED MOISTURE IN
SOUTHWEST FLOW FOR TUESDAY...BUT SOME PRECIPITABLE WATER VALUES
AROUND 0.70 INCHES COULD LEAD TO WEAK CONVECTION IN JOHNSON AND
NATRONA COUNTIES. HOWEVER...WITH DEW POINTS IN THE 30S HAVE
CONTINUED A GENERALLY DRY FORECAST FOR NOW. SOUTHWEST FLOW ADVECTS
IN DRIER AIR FROM THE GREAT BASIN WEDNESDAY AND THURSDAY AND DO NOT
SEE MUCH IN THE WAY OF AVAILABLE MOISTURE FOR ANY CONVECTION.
SURFACE DEW POINTS WILL GENERALLY RANGE FROM 25-35F. ALSO...
WEDNESDAY LOOKS TO BE THE WARMEST DAY OF THE WEEK WITH TEMPERATURES
RUNNING ABOUT 5-10F ABOVE NORMAL AND THE NORTHERN BASINS PUSHING
INTO THE 90S AGAIN. THE COMBINATION OF THE UNSEASONABLY HOT
TEMPERATURES...LOW HUMIDITY...AND INCREASING SOUTHWEST WIND OF 15-30
MPH WILL VERY LIKELY LEAD TO CRITICAL FIRE WEATHER CONDITIONS FOR
WEDNESDAY AND MOST PROBABLY THURSDAY. MOST INTENSE WINDS WILL BE IN
THE CORRIDOR FROM ROCK SPRINGS TO CASPER. THOSE WITH FIRE WEATHER
INTERESTS SHOULD BE AWARE OF THE LIKELIHOOD OF THESE CONDITIONS FOR
WEDNESDAY AND THURSDAY AND BE ON THE ALERT FOR POSSIBLE HIHGLIGHTS
ISSUED EARLY THIS WEEK. FIRST UPPER LOW IN THE PACIFIC NORTHWEST
TROUGH WILL EJECT INTO ALBERTA THURSDAY. THIS UPPER LOW WILL QUICKLY
BE REPLACED BY ANOTHER SHORTWAVE THAT WILL DROP INTO THE BASE OF THE
TROUGH OVER THE INTERMOUNTAIN WEST FOR FRIDAY. UPPER FLOW WILL
PARALLEL SURFACE FRONT THAT WILL BE ORIENTED NORTHEAST-SOUTHWEST
JUST TO THE WEST OF WYOMING FOR FRIDAY. HAVE NUDGED TEMPERATURES UP
A TAD FOR FRIDAY AS IT DOES LOOK LIKE THE COOLER AIR WILL HANG BACK
ONE MORE DAY. AM STILL CONCERNED THAT FRIDAY MAY INDEED BE WARMER
THAN CURRENTLY FORECAST WITH COMPRESSIONAL WARMING AHEAD OF THE
APPROACHING FRONT/TROUGH. MOISTURE WILL RIDE ALONG OUR NORTHWESTERN
ZONES FOR FRIDAY AFTERNOON AND SATURDAY. THEREFORE...HAVE INCREASED
PRECIP CHANCES OVER YELLOWSTONE AND THE SURROUNDING MOUNTAINS.
ENERGY IN THE BASE OF THE TROUGH WILL BEGIN TO EJECT SATURDAY WHILE
AT THE SAME TIME A SURFACE LOW TAKES SHAPE TO OUR SOUTHEAST. THIS
WILL BRING THE COLD FRONT ACROSS THE FORECAST AREA SATURDAY. BOTH
THE ECMWF AND GFS HAVE THE FORECAST AREA DRY SLOTTED SATURDAY AS THE
UPPER LOW TRACKS TO OUR NORTH. BEST CHANCE FOR MEASURABLE PRECIP
OVER THE WEEKEND WILL BE ACROSS THE NORTHERN THIRD OF THE FORECAST
AREA CLOSEST TO THE UPPER LOW. SURFACE HIGH PUSHES INTO WYOMING
SUNDAY AND 700MB TEMPERATURES FALL INTO THE ZERO TO +4C RANGE ACROSS
THE NORTH. THIS WILL LEAD TO COOLER THAN AVERAGE TEMPERATURES FOR
SUNDAY IN ALL BUT SOUTHWEST AND FAR WEST WYOMING.

&&

.AVIATION.../00Z ISSUANCE/

A COLD FRONT WILL CONTINUE TO PUSH EAST ACROSS THE INTERMOUNTAIN
WEST WITH SFC WINDS GENERALLY FROM THE SOUTHWEST TO WEST ACROSS MUCH
OF THE STATE AHEAD OF THE COLD FRONT...WINDS WILL BRIEFLY SWITCH TO
THE NW BEHIND THE FRONT WITH SOME AREAS OF 30-40KT GUSTS BEHIND THE
FRONT VCNTY KBYG KPOY KU68. THE MAIN AREA OF ISOLD-SCT -TSRA VCNTY
AND SOUTH OF A KEVW- KLND- KCPR LINE WITH HIGH BASED WINDY STORMS
EXPECTED INTO THE EARLY EVENING. THE COLD FRONT WILL BRING DRIER AIR
AND GUSTY WEST WIND INTO NW WYOMING MID TO LATE THIS
AFTERNOON...PUSHING ACROSS NORTH AND CENTRAL WYOMING LATE THIS
EVENING. CLEAR SKIES AND DIMINISHING WIND WILL PREVAIL ACROSS THE
AREA BEHIND THE FRONT EARLY MONDAY MORNING.

&&

.FIRE WEATHER...

...RED FLAG WARNING FOR PORTIONS OF CENTRAL AND NORTHERN WYOMING
THROUGH THE EVENING HOURS...

A COLD FRONT ASSOCIATED WITH THE TROUGH DIGGING TO THE WEST REMAINS
IN THE AREA NEAR THE MONTANA BORDER THIS AFTERNOON WITH COOLER
TEMPERATURES AND MODERATE HUMIDITY TO THE NORTH OF IT AND RED FLAG
TO NEAR RED FLAG CONDITIONS JUST TO THE SOUTH OF IT. MODELS ARE
CALLING FOR SOUTHWEST FLOW TO OVERTAKE THE FRONT AND CAUSE IT TO
RETREAT BACK NORTH FOR THE LATE AFTERNOON HOURS. THE MAIN FRONTAL
SURGE WILL COME LATER TONIGHT WITH STEADY 25 TO 35 MPH WINDS IN
JOHNSON COUNTY AND NORTHERN BIGHORN COUNTY BEHIND THE
FRONT...EXTENDED THE NORTHERN RED FLAG WARNINGS TO 3AM TO COVER THE
FRONTAL PASSAGE THOUGH IT MAY HAPPEN SOONER.

IN ADDITION...ISOLATED TO WIDELY SCATTERED MIXED WET AND DRY
THUNDERSTORMS ARE EXPECTED TO CONTINUE TO DEVELOP INTO THE EVENING
HOURS...WITH A FEW PERSISTING INTO THE NIGHT...ESPECIALLY EAST OF
THE DIVIDE.

IT WILL BE DRY BEHIND THE FRONT FOR MONDAY BUT A BIT COOLER. THERE
WILL BE SOME 20MPH BREEZES IN THE AFTERNOON BUT RED FLAG CONDITIONS
ARE NOT EXPECTED.

IT SILL LOOKS LIKE THERE COULD BE WIDESPREAD RED FLAG CONDITIONS MID
WEEK...STAY TUNED FOR UPDATES ON THE NEXT SYSTEM.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
RED FLAG WARNING UNTIL 9 PM MDT THIS EVENING FOR WYZ280-283-285-
289-300.

RED FLAG WARNING UNTIL 3 AM MDT MONDAY FOR WYZ275-276-281-282-
287.

&&

$$

SHORT TERM...ALLEN
LONG TERM...CNJ
AVIATION...ALLEN
FIRE WEATHER...ALLEN



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.