Area Forecast Discussion
Issued by NWS Riverton, WY

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000
FXUS65 KRIW 261713
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1113 AM MST MON JAN 26 2015

.SHORT TERM...TODAY THROUGH WEDNESDAY NIGHT

NW FLOW CONTINUES OVR WY WITH RIDGE WEST AND TROF EAST. JET
FOLLOWING RIDGE...ENCOMPASSING ENTIRE WRN CONUS...WITH COL
CONTINUING OVR THE EPAC WEST OF BAJA. SFC SHOWS HI P WEST...LOWER P
EAST...PROVIDING SOME MIXED AREAS WITH GUSTY WINDS...ESPECIALLY
ACROSS THE SRN/SERN FCST ZONES.

BEGINNING OF FCST HAS SOME AREAS OF PATCHY FOG IN THE USUAL
SPOTS...ESPECIALLY WEST OF THE DIVIDE. OTHERWISE...SKIES CLEAR OR
CLEARING WITH PLENTY OF SUNSHINE. BY TONIGHT...NW FLOW WILL BE
VIRTUALLY ELIMINATED...WHILE THE BAJA COL BEGINS TO KICK NWD AND
UNFOLD INTO AN OPEN WAVE. TUE WILL BE ANOTHER DAY SUNNY DAY ACROSS
MOST OF THE FA EXCEPT FOR THE SWRN ZONES WHICH WILL HAVE INCREASING
CLOUDS THRU THE DAY AS THE BAJA COL CONTINUES TO HEAD THIS
DIRECTION. ADDITIONALLY...THRU THE DAY ON TUE AND TUE NIGHT...SFC P
FIELD WILL BECOME BETTER SUITED FOR PRODUCING GUSTY SW WINDS...WITH
ADDITIONAL HELP IN THIS CASE FROM ALOFT AS UPR RIDGE ORIENTS ITSELF
FAR ENOUGH E TO TO ALLOW NEARLY UNIDIRECTIONAL SW FLOW THRU MID
LVLS. THIS TOGETHER WITH WARMING LL TEMPS...WILL ALLOW MODERATELY
STRONGER WINDS ALOFT TO INCREASE THE SFC WINDS ADIABATICALLY. THERE
WILL LIKELY BE A FEW ISOLATED AREAS THAT WILL BLOW WARNING
CRITERIA...SUCH AS OUTER DRIVE...HOWEVER MOST LOCATIONS CURRENTLY
LOOK TO REMAIN JUST BELOW WARNING LEVELS. BUT THIS WILL BE SOMETHING
TO WATCH OVR THE NEXT DAY OR SO.

TUE NIGHT INTO WED MORNING...AS THE FORMER COL FROM BAJA HEADS INTO
THE REGION AS AN OPEN WAVE...BUT STILL BE ABLE TO PRODUCE SOME
PRECIP STARTING BY BRUSHING THE WRN TO NWRN FCST AREA THRU THE
OVERNIGHT PERIOD INTO WED MORNING. POP CHANCES RISE ACCORDINGLY THRU
THE OVERNIGHT PERIOD TUE AND THRU THE DAY WED. THE FLEETING NATURE
OF THIS DISTURBANCE STILL LOOKS TO PRECLUDE HIGH QPF OR ASSOCIATED
SNOWFALL THRU THE END OF THIS FCST PERIOD...REMAINING BELOW ADVISORY
CRITERIA FOR THE MOST PART IN BOTH THE WESTERN MOUNTAINS AND
VALLEYS. THE UPR WAVE ITSELF WILL MAKE A RIGHT TURN ACROSS
WY...WITH H7 WINDS TURNING TO THE NW...BRING SOME CHANCES FOR
RAIN...RAIN/SNOW MIX...AND WET SNOW...TO THE AREAS EAST OF THE
DIVIDE BY MID-DAY WED...CONTINUING S AND E OUT OF THE FA DURING
THE EVENING PERIOD. AS MIXED PRECIP PRESENT ITSELF...IN ADDITION
TO FAST MOVEMENT IN AND OUT OF THE CWA...NOT MUCH ACCUMULATION IS
EXPECTED E OF THE DIVIDE. COOLER HIGH ELEVATIONS OF THE MOUNTAINS
WILL BE PRIVY TO THE BETTER AMOUNTS...BUT STILL BELOW 3 INCHES
EVEN IN THE BIGHORNS.

.LONG TERM...THURSDAY THROUGH MONDAY

FOR THURSDAY AND THURSDAY NIGHT...THE MAIN FOCUS WILL BE AN UPPER
LOW PUSHING INTO SOUTHERN CALIFORNIA/DESERT SOUTHWEST. MODELS
SHOW THE POSSIBILITY OF SOME ENERGY FROM THIS SYSTEM EJECTING OUT
AND IMPACTING THE EXTREME SOUTHERN PORTIONS OF THE FORECAST AREA.
OTHERWISE...DRY AND MILD JANUARY CONDITIONS ARE EXPECTED THURSDAY.
ALTHOUGH SOME ENERGY FROM THIS UPPER LOW COULD CONTINUE TO IMPACT
THE SOUTHERN PORTION OF THE AREA FRIDAY...ATTENTION WILL SHIFT TO
THE NORTHERN STREAM. GLOBAL MODELS ARE IN DECENT AGREEMENT WITH A
SHORTWAVE TROUGH AND ASSOCIATED COLD FRONT DIVING SOUTHEAST OUT OF
CANADA IN THE LATE FRIDAY INTO SATURDAY TIME FRAME. THIS COULD
RESULT IN SOME SNOWFALL EAST OF THE DIVIDE...BUT WILL KEEP LOW POPS
CONFINED MAINLY TO THE MOUNTAINS FOR NOW FRIDAY NIGHT AND SATURDAY.

ALTHOUGH MEDIUM RANGE GUIDANCE GENERALLY SHOW NORTHWEST FLOW
SATURDAY THROUGH MONDAY...THEY HAVE SIGNIFICANT TEMPERATURE
DIFFERENCES ESPECIALLY SUNDAY AND MONDAY. THE GFS IS MUCH MILDER
SINCE IT EJECTS A SIGNIFICANT PIECE OF THE GULF OF ALASKA LOW
THROUGH A RIDGE OVER BRITISH COLUMBIA...BEFORE DIVING IT SOUTHEAST
OVER THE AREA SUNDAY AND MONDAY. THE 00Z ECMWF AND GEM SHOW THE
UPPER RIDGE OVER BRITISH COLUMBIA HANGING TOUGH...WITH MORE OF A
DIRECT...COLDER FLOW OUT OF CANADA. THE ECMWF SOLUTION SEEMS TO BE
MORE PLAUSIBLE...BUT EVEN IT WAS MUCH WARMER YESTERDAY. THUS HAVE
DECIDED TO KEEP FORECAST ON THE WARM SIDE...BUT COOLER THAN MEX MOS
GUIDANCE EARLY NEXT WEEK. BOTH SOLUTIONS SUPPORT A CHANCE OF
SNOWFALL OVER THE NORTHWEST AND NORTHERN MOUNTAINS...POSSIBLY
SPILLING INTO THE LOWER ELEVATIONS AT TIMES. THE SOUTHWEST PORTION
OF THE AREA WOULD BE THE DRIEST IN THIS SCENARIO. DUE TO TIMING
DIFFERENCES WILL BROAD BRUSH SLIGHT NORTHWEST/NORTHERN MOUNTAIN
POPS...AND KEEP THE LOWER ELEVATIONS MAINLY DRY UNTIL THERE IS
BETTER MODEL CONTINUITY.

&&

.AVIATION.../18Z ISSUANCE/

VFR CONDITIONS WILL PREVAIL OVER THE REGION THROUGH TUESDAY
AFTERNOON. AREAS OF LOW CLOUDS AND FOG SHOULD BURN OFF BY AROUND 19
OR 20Z IN THE FAR WESTERN VALLEYS. LOCAL MVFR OR IFR CONDITIONS WILL
OCCUR UNTIL 19Z. THE JACKSON AIRPORT MAY BE IMPACTED BY LOW CLOUDS
OR FOG THROUGH 19Z. PATCHY FOG MAY REFORM IN THE WESTERN VALLEYS
AFTER 8Z TONIGHT.

&&

.FIRE WEATHER...

FIRE DANGER REMAINS LOW FOR MOST AREAS. MIXING/INVERSION HEIGHTS
WILL REMAIN ON THE LOWER SIDE...1000 TO 1500 FEET AT MOST...THROUGH
TUESDAY NIGHT FOR MOST LOCATIONS NORTH OF A ROCK SPRINGS TO CASPER
LINE. POOR SMOKE DISPERSION IS ALSO FORECAST FOR THE SAME LOCATIONS
THROUGH THE SAME PERIOD. SOUTH OF THIS LINE...BETTER MIXING WILL
OCCUR ON TUESDAY. PRECIPITATION IS NOT EXPECTED ANYWHERE OVER THE
FORECAST AREA UNTIL LATE TUESDAY NIGHT WHEN INCREASED MOISTURE
FOLLOWING AN UPPER LEVEL DISTURBANCE HEADS INTO THE WEST AND
NORTHWEST ZONES...THEN EAST ACROSS THE REST OF THE FORECAST AREA ON
WEDNESDAY. WHILE EVERYONE WILL STAND A CHANCE TO GET SOME MEASURABLE
PRECIPITATION...AMOUNTS WILL GENERALLY REMAIN BELOW A TENTH OF AN
INCH FOR MOST LOCATIONS.

&&

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

&&

$$

SHORT TERM...BRAUN
LONG TERM...WM
AVIATION...HATTINGS
FIRE WEATHER...BRAUN










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