Area Forecast Discussion
Issued by NWS Riverton, WY

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000
FXUS65 KRIW 051740 AAA
AFDRIW

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE RIVERTON WY
1140 AM MDT SAT JUL 5 2014

.SHORT TERM...SATURDAY THROUGH MONDAY NIGHT

IT CERTAINTY WILL FEEL LIKE SUMMER TODAY ACROSS THE COWBOY STATE AS
A RIDGE DOMINATES THE WEATHER FOR SATURDAY. THIS WILL LIKELY BE THE
HOTTEST DAY OF THE YEAR SO FAR FOR MANY AREAS. THERE COULD EVEN BE
SOME TRIPLE DIGIT TEMPERATURES IN THE WARMER LOCATIONS LIKE THE BIG
HORN BASIN. AS FOR THE CHANCE OF ANY THUNDERSTORMS...HIGH HEIGHTS
SHOULD PREVENT MOST OF THEM. HOWEVER...THERE WILL BE JUST ENOUGH
MOISTURE LEFT OVER FOR THE SLIGHT CHANCE OF A FEW TO FIRE THIS
AFTERNOON AND EVENING...MAINLY OVER THE MOUNTAINS. AS A RESULT...WE
ADDED SOME ISOLATED ACTIVITY. HOWEVER...THE VAST MAJORITY OF THE
AREA WILL BE JUST DRY AND HOT.

EXPECT MORE OF THE SAME TOMORROW. HOWEVER...WITH SLIGHTLY LOWER
THICKNESSES TEMPERATURES MAY COOL OFF JUST A FEW DEGREES COMPARED TO
TODAY. HOWEVER...IT WILL CONTINUE TO BE A HOT DAY WITH MOST LOWER
ELEVATIONS SEEING ANOTHER DAY WITH HIGHS INTO THE 90S. AGAIN...THE
VAST MAJORITY OF THE AREA SHOULD BE RAIN FREE. HOWEVER...THERE ARE
SOME MODEL DISCREPANCIES WITH THE GFS SHOWING A WEAK BACK DOOR COLD
FRONT MOVING INTO FAR NORTHERN PORTIONS OF THE COUNTY WARNING AREA
WITH THE CHANCE OF SOME LATE DAY OR EVENING CONVECTION. THE NAM IS
MAINLY DRY EXCEPT FOR BIG HORN MOUNTAINS...WHICH MOST OF THE MODELS
SEEM TO THINK ARE WETTER THAN THE AMAZON RAIN FOREST MOST OF THE
TIME. FOR NOW WE ADDED SOME SLIGHT POPS TO THE NORTHERN MOUNTAINS
FOR THE AFTERNOON AND EVENING HOURS.

AS FOR MONDAY...ALL MODELS SHOW THE AXIS OF THE RIDGE CONTINUING TO
DRIFT WESTWARD AND AND THE BACK DOOR FRONT SAGGING SOUTHWESTWARD
INTO PORTIONS OF THE COUNTY WARNING AREA EAST OF THEN DIVIDE. THIS
SHOULD TAKE THE EDGE OFF OF THE HEAT WITH MOST AREAS SEEING HIGH
TEMPERATURES RETREATING BACK INTO THE 80S. AS FOR THE CHANCE OF
THUNDERSTORMS...THE MODELS CONTINUE TO DIFFER WITH THE GFS HAVING
MORE COVERAGE THAN THE NAM. WITH THE DIFFERENCES...WE MADE ONLY
MINOR CHANGES WITH THE MOST COVERAGE DURING THE EVENING HOURS.

.LONG TERM...TUESDAY THROUGH SATURDAY

RIDGE AXIS HOLDS THROUGH OUR WEST THROUGH WEDNESDAY BEFORE
REDEVELOPING TO OUR S OR SE AGAIN THURSDAY AND THEN POTENTIALLY
EXPANDING FRIDAY INTO SATURDAY. THE 00Z GFS IS ONCE AGAIN SHOWING A
LARGE CLOSED UPPER HIGH BUILDING OVER COLORADO AS EARLY AS THURSDAY
NIGHT AND THEN EXPANDING NWD INTO SATURDAY. THE 12Z ECMWF KEPT THE
MAIN UPPER HIGH/RIDGE AXIS MORE OVER THE SERN U.S WHILE THE 00Z EURO
BUILDS A RIDGE NWWD INTO THE PACNW. THE GFS SOLUTION ALLOWS FOR
MOISTURE AROUND THE WEST EDGE OF THE HIGH WHICH WOULD BE ENOUGH TO
FIRE OFF LATE DAY THUNDERSTORMS EACH DAY. THE COOLEST DAY WILL BE
TUESDAY IN THIS SCENARIO WITH TEMPERATURES WARMING BACK UP WEDNESDAY
INTO THURSDAY. THE GFS IS VERY HOT WITH THE CLOSER PROXIMITY OF A
597 HEIGHT H7 UPPER WITH H7 TEMPERATURES OF 17-20C FROM THURSDAY
ONWARD...PEAKING SATURDAY. THE NEW ECMWF IS NOW BUILDING THE RIDGE
NWWD INTO THE PACNW. THE ECMWF HAS A STRONG SHORTWAVE THAT PUSHES
EAST ACROSS THE NRN ROCKIES ON FRIDAY AND THE RIDGE BUILDS BEHIND
THIS SYSTEM. THE GFS DOESN`T REALLY HAVE THIS STRONG SHORTWAVE.
TOUGH CALL ON THE WHICH EVOLUTION WILL BE RIGHT. UPPER RIDGE/HIGH TO
OUR SOUTH IS CLIMATOLOGICALLY FAVORED BUT WE`VE ALSO HAD A TENDENCY
FOR NW FLOW TO DEVELOP THIS SPRING AND EARLY SUMMER. COULD SEE SOME
DECENT STORMS AGAIN TUESDAY WITH MOIST E-SE FLOW WITH SURFACE HIGH
STILL OFF TO THE N OR NE. LEE TROUGHING BEGINS TO ESTABLISH ITSELF
ON WEDNESDAY WHICH MAY PUSH THE BEST STORMS TO OUR ERN ZONES.
MONSOONAL MOISTURE MAY THEN REDEVELOP THURSDAY ONWARD BEING DRAWN UP
IN THE SW FLOW ON MULTIPLE DISTURBANCES SIMILAR TO THE LAST COUPLE
DAYS IF THE GFS IS RIGHT. THE ECMWF WOULD BE DRIER AND NOT AS HOT
WITH THE DEVELOPING NW FLOW. HOWEVER...THERE COULD STILL BE A FRONT
THAT DROPS DOWN IN THIS NW FLOW THAT THE ECMWF SHOWS THAT WOULD BE
A FOCUS FOR TSTM DEVELOPMENT. THE GEM IS A COMPROMISE BETWEEN THE
00Z GFS AND OLDER 12Z ECMWF WITH UPPER RIDGE OVER THE SERN U.S.
AND ANOTHER HIGH CENTER BETWEEN CO AND SRN WYO AT THE END OF THE
MEDIUM RANGE PERIOD. THE GFS ENSEMBLES SUPPORT A UPPER HIGH
SOMEWHERE TO OUR SE AS DOES THE ECMWF ENSEMBLES. LEANING THAT WAY
WOULD OPEN THE DOOR FOR MOISTURE TO WORK AROUND THE PERIPHERY OF
THE UPPER HIGH WITH EMBEDDED DISTURBANCES SIMILAR TO THE PAST
COUPLE DAYS. WILL LEAVE THUNDERSTORM CHANCES IN BASED ON THIS
IDEA FOR THURSDAY THROUGH SATURDAY AND FINE TUNE WITH TIME.

.AVIATION.../18Z ISSUANCE/

VFR/NSW CONDITIONS WITH UNLIMITED CIGS WILL PREVAIL. SOME CU
DEVELOPMENT COULD OCCUR OVER THE MOUNTAINS LATE THIS AFTERNOON
WITH SOME GUSTY WIND EMINATING FROM THESE BUILDUPS WITH A VERY
ISOLATED -TSRA/-SHRA POSSIBLE AFTER 20Z AND DIMINISHING AFTER 03Z.

.FIRE WEATHER...

DRY AND HOT CONDITIONS WILL MOVE OVER THE AREA TODAY WITH HUMIDITY
FALLING BELOW 15 PERCENT IN MANY AREAS. A GUSTY BREEZE WILL BE
PRESENT IN SOME LOCATIONS DURING THE AFTERNOON. THE COMBINATION OF
THESE CONDITIONS AND CRITICALLY DRY FUELS WILL LEAD TO THE
CONTINUATION OF THE RED FLAG WARNING FOR NATRONA AND SOUTHERN
JOHNSON COUNTIES. EVEN AREAS OUTSIDE OF THE RED FLAG AREA COULD SEE
AN INCREASE IN FIRE BEHAVIOR SHOULD ANY FIRES BEGIN OVER THE NEXT
COUPLE DAYS. A WEAK COLD FRONT MOVING SOUTHWARD WILL BRING COOLER
TEMPERATURES AND SOMEWHAT HIGHER HUMIDITY FOR THE BEGINNING OF THE
NEXT WORK WEEK.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
RED FLAG WARNING UNTIL 9 PM MDT THIS EVENING WYZ280-281.

&&

$$

SHORT TERM...HATTINGS
LONG TERM...SKRBAC
AVIATION...ALLEN
FIRE WEATHER...HATTINGS





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