Area Forecast Discussion
Issued by NWS Riverton, WY

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000
FXUS65 KRIW 260527
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1125 PM MDT WED MAR 25 2015

UPDATE...ADDED 06Z AVIATION DISCUSSION BELOW.

.SHORT TERM...TONIGHT THROUGH THURSDAY (ISSUED AT 145 PM MDT)

INSTABILITY ACROSS OUR ERN ZONES IS AIDING IN SOME WEAK SHOWERS AND
LOWER CIGS WHILE WARM ADVECTION SPILLOVER CLOUDS ARE ALREADY MOVING
INTO THE WEST. WILL KEEP THE SHOWERS IN THE ERN ZONES THROUGH 00Z
BEFORE RETREATING THEM INTO THE MOUNTAINS. STORM SYSTEM CAME THROUGH
ABOUT AS EXPECTED LAST NIGHT/EARLY THIS MORNING EXCEPT THE MAIN
BAND WAS NOT AS INTENSE IN NATRONA COUNTY WHERE AMOUNTS WHERE
GENERALLY ONLY A SKIFF TO 2 INCHES. THE REST OF THE AREA WORKED
OUT WELL. AS THE RIDGE MOVES/BUILDS IN THE ISENTROPIC UPGLIDE
INCREASES ENOUGH TO PRODUCE SOME CONSIDERABLE MID AND HIGH CLOUDS
ACROSS THE AREA TONIGHT AND THURSDAY WITH THE ATMOSPHERE
MOISTENING ENOUGH OVER THE NRN MOUNTAINS TO POSSIBLY PRODUCE SOME
VERY LIGHT SNOW OF FLURRIES AT TIMES TONIGHT AND THURSDAY.
OTHERWISE...ROUGHLY 10 DEGREES WARMER ON THURSDAY ACROSS MUCH OF
THE AREA AND DRY.

.LONG TERM...THURSDAY NIGHT THROUGH WEDNESDAY

BEGINNING OF FCST...UPR RIDGE ACROSS WRN CONUS...SW AND SFC FRONT
THRU ERN WY AND OFF INTO THE CNTRL/SRN PLAINS WITH LARGE TROF OVR
THE ERN 2/3S OF THE CONUS. SFC WILL HAVE HI P BEGINNING TO TAKE
HOLD...BUILDING IN FROM THE SW.

FAIRLY GOOD AGREEMENT AMONG THE LR MDLS THRU SUN MORNING BEFORE SIG
DIFFERENCES BEGIN TO ARISE. BETWEEN NOW AND THEN...RIDGING AND
WARMING THRU SAT MORNING AHEAD OF THE NEXT WX SYSTEM. CYCLOGENESIS
ACROSS THE NWRN CONUS WILL OCCUR FRI NIGHT...MATURING AND RACING
EWD...BUSTING INTO THE RIDGE AND ARRIVING W/ FRONT NEAR THE WRN FA
BY MID-DAY SAT. ALTHOUGH THIS SYSTEM DYNAMICALLY WILL BE DECENT
ENOUGH...ESPECIALLY WHEN ASSOCIATED 100 KT JET IS COMBINED WITH THE
LL FRONT...GOOD CONVECTIVE NATURE...AND TERRAIN FEATURES...THE SPEED
OF MOVEMENT AND GENERAL LACK OF MOISTURE WILL KEEP PRECIP TOTALS ON
THE LOW SIDE AT LESS THAN A TENTH OF AN INCH UNDER THE BEST
CIRCUMSTANCES. HOWEVER...THAT SAID...THE IMPACT OF THE DAY THAT WILL
RESULT FROM THIS ACTIVITY WILL INCLUDE A RAPID INCREASE IN SFC WINDS
OUT OF THE WEST...BOTH JUST AHEAD OF AND BEHIND THE FRONT... AS  THE
LOWER LVLS WARM...UPPER LEVEL WINDS INCREASE...AND THE SFC P GRAD
TIGHTENS VERY QUICKLY. AS A MATTER OF FACT...MOST OF THE FA CAN
EXPECT WINDS TO BECOME WRLY 20 TO 30 MPH WITH GUSTS RANGING FROM 40
TO 50 MPH. THIS COMBINED WITH DECLINING RH VALUES BY AFTERNOON WILL
PUT SOME OF THE CWA UNDER NEAR RED FLAG CONDITIONS...ESPECIALLY FIRE
WX ZONES 279 280 AND 289. WILL MONITOR OVR THE NEXT 24 HRS FOR
POSSIBLE FWW. ADDITIONALLY...A FEW OF THE HIGH BASED SHOWERS MAY
PRODUCE SOME ISOLATED LIGHTNING SAT AFTERNOON...ESPECIALLY ACROSS
THE NRN FA WHERE MID LVL CONVECTIVE DYNAMICS WILL BE
STRONGER...BUT AGAIN OVR MOISTURE DEPRIVED LOWER LEVELS.

INTO THE BEYOND...UNSETTLED CONDITIONS CONTINUE. AS MENTIONED
BEFORE...MDLS BEGIN TO DIVERGE...PARTICULARLY W/ REGARD TO TIMING
DIFFERENCES THIS TIME AROUND. THIS WILL MAINLY AFFECT THE ARRIVAL
OF THE DISTURBANCE MOVING INTO THE REGION TUE...THE EURO BEING THE
FIRST TO ARRIVE AND LEAVE...OTHERS FOLLOWING. SPATIAL TRENDS BETWEEN
THE MDLS...HOWEVER...DO KEEP THE BETTER WX PARAMETERS MAINLY ACROSS
THE NRN THIRD OF THE CWA...SO REALLY JUST A MATTER OF STRETCHING CHC
POPS ENOUGH TO FIT WITHIN THE UNCERTAINTY OF ALL THE MDLS. TEMPORAL
DIFFERENCES DECREASE AFTER WED...WITH THE CONSENSUS OF ARRIVAL OF
THE NEXT WX MAKER TO BE MID-DAY THU IN THE WEST...PERHAPS
INFLUENCING MUCH OF THE FA...AND CONTINUING THRU AT LEAST FRI
MORNING.

&&

.AVIATION.../06Z ISSUANCE/

VFR CONDITIONS WILL PREVAIL ACROSS THE AREA THROUGH 12Z FRIDAY.
GUSTY W-NW WINDS ALONG THE LEE SLOPES OF THE DIVIDE...VCNTY
KCOD-KRIW...WILL CONTINUE OVERNIGHT BEFORE DIMINISHING AFTER 15Z
THUR.  WINDS IN THESE AREAS WILL LIKELY PICK UP AGAIN AROUND SUNSET
THURSDAY EVENING.  OTHERWISE...OCNL CIGS FL130-150 WILL BE
ENCOUNTERED ACROSS THE NORTHERN HALF OF WYOMING THROUGH 00Z FRIDAY.

&&

.FIRE WEATHER...

SNOW SHOWERS WILL RETREAT TO THE MOUNTAINS TONIGHT AND DECREASE TO
FLURRIES OR VERY LIGHT SNOW. THE LOWER ELEVATIONS WILL BE DRY AND
ABOUT 10 DEGREES WARMER ON THURSDAY WITH BREEZY TO LOCALLY WINDY
AREAS. MIN RH`S WILL BE ABOUT 25 TO 40 PERCENT. A MORE SIGNIFICANT
WARMUP WILL OCCUR FRIDAY INTO SATURDAY. BY SATURDAY...HIGHS WILL
BE IN THE 60S TO LOWER 70S EAST OF THE DIVIDE WITH MIN RH`S IN THE
UPPER TEENS TO LOWER 20S ALONG WITH INCREASING WIND AHEAD OF AN
APPROACHING COLD FRONT. EXPECT ELEVATED FIRE DANGER ON SATURDAY.

&&

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

&&

$$

SHORT TERM...PS
LONG TERM...BRAUN
AVIATION...AEM
FIRE WEATHER...PS











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