Area Forecast Discussion
Issued by NWS Riverton, WY

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000
FXUS65 KRIW 192018
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
218 PM MDT SUN OCT 19 2014

.SHORT TERM...TONIGHT THROUGH MONDAY

HIGH PRESSURE SURFACE AND ALOFT WILL PRODUCE A DRY STABLE AIR MASS
OVER WESTERN AND CENTRAL WYOMING TONIGHT AND MONDAY WITH MILD
TEMPERATURES AND LIGHT WIND. MODELS IN VERY GOOD AGREEMENT AT THIS
POINT.

.LONG TERM...MONDAY NIGHT THROUGH SUNDAY

THE BEGINNING OF THE FCST PERIOD HAS THE FA ON THE BACKSIDE OF THE
EXITING UPR RIDGE OR ON THE LEADING EDGE OF APPROACHING TROF...TAKE
YOUR PICK. FLOW THRU THE UPR PATTERN CONTINUES TO TAKE
DISTURBANCES...WHEN THEY HAPPEN...QUICKLY THRU THE FLOW...NOT
ALLOWING FOR MUCH IN THE WAY OF REGIONAL/LOCAL DEVELOPMENT.

SFC LEE SIDE TROFFING E OF BIGHORNS SHOULD JUST BE ONGOING AHEAD OF
THE TROF W/ WEAK CYCLO/FRONTO -GENESIS PROCEEDING THRU THE DAY
TUESDAY...AHEAD OF A MOBILE TROF ALONG/AHEAD OF JET...SOMEWHERE OVER
AND ALONG THE SFC TROF. ATTM...MOISTURE LOOKS TO COME TO THE FA IN
TWO WAYS...BOTH RATHER LIMITED HOWEVER. ONE...FROM THE EPAC RIDING
IN WITH THE SW TROF...THE OTHER FROM THE S/SW AROUND BUILDING HIGH
PRESSURE OVR THE SCNTRL STATES. TRAJECTORY ISSUES WITH THE SRN
MOISTURE BRANCH WILL LARGELY DICTATE JUST HOW MUCH MOISTURE HAS THE
POSSIBILITY OF GETTING INTO THE FA TO BEGIN WITH...AND THEN HOW MUCH
GETS WRUNG OUT OVR THE CNTRL ROCKIES BEFORE ENTERING THE FA WHEN IT
DOES. STILL...CHC TO LOW END LIKELY IN THE MOUNTAINS LOOKS
GOOD...PARTICULARLY TUE NIGHT THRU WED MORNING. AS THIS SYSTEM
CONTINUES TO LOOK QUITE PROGRESSIVE AND POSSIBLY MOISTURE
CHALLENGED...WILL KEEP QPF VALUES FOR ANY 6 HR PERIOD AOB .30IN IN
THE MOUNTAINS...WHICH IS A THIRD TO A HALF OF WHAT SOME MDLS ARE
SPITTING OUT IN THIS SPLIT SITUATION. THIS WILL KEEP 24 HR SNOWFALL
POTENTIAL EVEN OVER THE HIGHEST PEAKS AOB 6IN AT BEST. WILL WATCH
FOR REASONS TO INCREASE/DECREASE THESE LIQUID/FROZEN TOTALS OVER THE
NEXT DAY OR TWO. LOW ELEVATIONS DO NOT CURRENTLY LOOK TO BE IMPACTED
MUCH...WITH SOME LIGHT RAIN PERHAPS MIXING WITH SNOW AT BEST FOR A
BRIEF PERIOD EARLY WED.

BEYOND WED...AS SW TROF QUICKLY EXITS...FLAT MODEST RIDGING RETURNS
TO THE AREA BY WED EVE. FROM THIS POINT ON MDLS BEGIN TO DIVERGE AND
CONTINUE TO INCREASE IN DIFFERENCES THROUGHOUT THE REST OF THE FCST.
WHILE SOME MINOR AMPLITUDE DIFFERENCES ARISE ALONG THE WAY...MAIN
DIFFERENCES SHOWING IN THE ENSEMBLE MEAN OUTPUT OF THE RESPECTIVE MDLS
PING ON HOW TO HANDLE (OR NOT TO HANDLE) AN EJECTING NORTHERN JET AND
THE EFFECT ON THE TROF THAT IS ASSOCIATED WITH IT...LEADING TO
SEVERE TIMING DIFFERENCES BY THE END OF THE FCST PERIOD. LUCKILY...ANY
MOISTURE SOURCE INTO THE REGION WILL BE SEVERELY LACKING DURING MOST
OF THIS TIMEFRAME...SO MOST PRECIP CHCS WILL BE SUPPRESSED BELOW
ISOLATED THRU THE FCST...WITH ONLY LOW END ISOLATED CHCS ARISING BY
SUNDAY...DUE MOSTLY TO THE INFLUENCE OF THE GFS AND ITS FASTER
SOLUTION. NOTHING SPECTACULAR EVEN IF SOMETHING DOES HAPPEN IN THE
GENERALLY VERY PROGRESSIVE AND DRY ATMOSPHERE.

&&

.AVIATION.../00Z ISSUANCE/

VFR CONDITIONS WITH SKC TO FEW 250 WILL PREVAIL ACROSS WESTERN AND
CENTRAL WYOMING THROUGH 00Z TUESDAY WITH HIGH PRESSURE SURFACE AND
ALOFT PRODUCING A DRY STABLE AIR MASS WITH LIGHT SURFACE WINDS.

&&

.FIRE WEATHER...

HIGH PRESSURE SURFACE AND ALOFT WILL DOMINATE THE WEATHER THROUGH
MONDAY NIGHT WITH A DRY STABLE AIR MASS AND SEASONABLY WARM
TEMPERATURES AND LOW WIND SPEEDS. RELATIVE HUMIDITY WILL DIP INTO THE
LOWER 20S AND UPPER TEENS AT TIMES...WINDS SPEEDS WILL REMAIN LOW
HELPING TO AVOID ENHANCED FIRE DANGER.  WIND SPEEDS WILL INCREASE
ON TUESDAY AHEAD OF AN APPROACHING PACIFIC LOW PRESSURE TROUGH ON
TUESDAY. WINDS AND MOISTURE WILL INCREASE TUESDAY NIGHT AND
WEDNESDAY WITH CHANCES OF WETTING RAIN INCREASING ACROSS THE
HIGHER ELEVATIONS OF THE WEST AND ACROSS RAWLINS DISPATCH
AREA...WITH A LOW CHANCE EAST OF THE DIVIDE.

&&

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

$$

SHORT TERM...C.BAKER
LONG TERM...BRAUN
AVIATION...C.BAKER
FIRE WEATHER...C.BAKER





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