Area Forecast Discussion
Issued by NWS Riverton, WY

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000
FXUS65 KRIW 271741
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1041 AM MST FRI FEB 27 2015

.SHORT TERM...TODAY THROUGH SUNDAY NIGHT

A PUSH OF MOISTURE MOVING IN THE NORTHWEST FLOW WILL KEEP SOME LIGHT
SHOWER ACTIVITY ACROSS NORTHWESTERN WYOMING TODAY. THE VERY WEAK
DISTURBANCE USHERING THIS MOISTURE PUSH WILL CONTINUE TO MOVE EAST
THROUGH THE FORECAST AREA OVERNIGHT. THE MOISTURE IS EXPECTED TO
INCREASE AND SPREAD ACROSS THE NORTHERN THIRD OF THE FORECAST AREA
BY SATURDAY MORNING. TEMPERATURES WILL BE ABLE TO WARM
SLIGHTLY...THOUGH WILL STILL REMAIN COOL.

AN AREA OF LOW PRESSURE OVER THE PACIFIC NORTHWEST WILL DIVE SOUTH
ON SATURDAY...ARRIVING OVER CALIFORNIA SATURDAY. AS THIS SYSTEM
MOVES SOUTH IT WILL BRING COOLING TEMPERATURES...AND SEND ADDITIONAL
PULSES OF MOISTURE OVER THE FORECAST AREA. THE BEST OF THESE PULSES
IS NOT EXPECTED TO ARRIVE UNTIL LATE SATURDAY AFTERNOON...AND WILL
PRIMARILY IMPACT SOUTHWESTERN WYOMING. THIS SYSTEM WILL CONTINUE TO
MOVE SOUTH THROUGH SUNDAY WITH PRECIPITATION LINGERING OVER SOUTHERN
WYOMING THROUGH SUNDAY AFTERNOON. A BRIEF PERIOD OF DRY CONDITIONS
POSSIBLE SUNDAY NIGHT...THOUGH MODELS DO INDICATE THE POTENTIAL FOR
ADDITIONAL MOISTURE ACROSS SOUTHERN WYOMING DURING THE LATE EVENING
HOURS OF SUNDAY.

.LONG TERM...MONDAY THROUGH FRIDAY

MAIN CHANGE FOR TONIGHT ARE THE MODELS NOT SHOWING AS MUCH ENERGY
DIGGING INTO THE GREAT BASIN/INTER-MOUNTAIN WEST MONDAY NIGHT AND
TUESDAY AS LAST NIGHT. MORE SHEARING OR JUST OVERALL LESS ENERGY.
THE SYSTEM THE MODELS TRACK FROM KAMCHATKA YESTERDAY IS STILL THE
SAME BUT THE END SOLUTION IS JUST DIFFERENT. STILL LOOKS LIKE SNOW
SPREADING S AND SE ACROSS THE AREA MONDAY NIGHT INTO EARLY TUESDAY
AND TURNING SHARPLY COLDER. SOME FAIRLY DECENT QG FORCING MAY
COMBINE WITH SOME INITIAL RRQ JET DYNAMICS MONDAY NIGHT AND THEN
LEFT EXIT REGION ON TUE WITH THE NEXT JET APPROACHING. WITH LESS
ENERGY TO THE WEST...MOVEMENT IS FASTER AND NOW WE MAY ACTUALLY
CLEAR BY WEDNESDAY MORNING LEADING TO SOME BITTER COLD LOWS. A
COLD COUPLE DAYS THOUGH FOR TUE AND WED. ON THE PLUS SIDE...THE
RIDGE FLATTENS MORE QUICKLY WITH A RATHER FAST MODERATION THURSDAY
INTO FRIDAY ON THE GFS. BACK TRACKING A LITTLE...THE WEEKEND
SYSTEM ENERGY LINGERS JUST TO THE SOUTH TO START THIS PERIOD
MONDAY WITH CONTINUED POTENTIAL FOR CLOUDS AND MAYBE EVEN SOME
VERY LIGHT PCPN IN OUR FAR SRN ZONES. OTHERWISE... DETERIORATING
CONDS BEGINNING LATER MONDAY ONWARD WITH OUR AFOREMENTIONED MONDAY
NIGHT/TUE SYSTEM FAST APPROACHING. RIGHT AT THE END OF THE MEDIUM
RANGE PERIOD...THE MODELS DIVERGE AS TO THE HANDLING OF A PIECE OF
ENERGY CURRENTLY COMING OFF THE ASIA COAST. THE GFS BRINGS IT
FURTHER OVER THE RIDGE AND INTO THE NRN PLAINS WHILE THE EURO
BRINGS THIS SHORTWAVE AT A LITTLE LOWER LATITUDE ALLOWING IT TO
DIG SE INTO OUR AREA NEXT FRIDAY NIGHT. KEEPING IT DRY FOR NOW.
THE GFS WOULD HAVE A MUCH NICER DAY ON FRIDAY WHILE THE ECMWF IS
ALREADY DIGGING THE LOW TOWARDS US WITH FALLING TEMPS BEHIND A
COLD FRONT.

&&

.AVIATION.../18Z ISSUANCE/

FREQUENT MOUNTAIN OBSCURATIONS ALONG AND WEST OF THE CONTINENTAL
DIVIDE THROUGH THE FORECAST PERIOD. ALSO...FOOTHILL OBSCURATIONS IN
THE VICINITY OF KLND AND KRIW WILL DISSIPATE EARLY THIS AFTERNOON.
EXPECT MORE WIDESPREAD OBSCURATIONS DEVELOPING FROM NORTH TO SOUTH
AFTER 03Z/SAT THROUGH 09Z/SAT.

EAST OF THE DIVIDE...KCOD/KCPR/KLND/KRIW/KWRL ROUTES

IFR/MVFR CONDITIONS WITH LOW STRATUS DECK AT KRIW AND KLND THIS
MORNING. EDGES HAVE BEEN SLOW TO ERODE. HAVE BACKED OFF THE
DISSIPATION OF THE STRATUS UNTIL 19Z-20Z. MORE SUNSHINE HAS BEEN
STARTING TO SHOW THROUGH SINCE 17Z. OTHER TERMINALS WILL BE VFR
THROUGH THIS AFTERNOON. ANOTHER SURGE OF COLD AIR WILL BRING A
RETURN OF LOW CLOUDS AND MVFR OR LOW VFR CEILINGS OVER NORTHERN
WYOMING BETWEEN 00Z-06Z/SAT. THIS AREA OF CLOUDS AND LIGHT SNOW WILL
PUSH SOUTH THROUGH THE NIGHT. KWRL IS THE LEAST LIKELY OF THE
TERMINALS TO SEE AN EXTENDED PERIOD OF LIGHT SNOW. BEST CHANCE FOR
MVFR VISIBILITIES THROUGH 18Z/SAT WILL BE FROM KLND-KCPR WHERE WEAK
UPSLOPE WOULD BE FAVORABLE AFTER THE COLD FRONT PUSHES SOUTH.

WEST OF THE DIVIDE...KBPI/KJAC/KPNA/KRKS ROUTES

AREAS OF LOW CLOUDS AND LIGHT SNOW ACROSS PORTIONS OF THE FAR WEST
MOUNTAINS AND VALLEYS THIS MORNING. IFR/MVFR CONDITIONS AT KJAC ARE
LIKELY TO HANG ON THROUGH ABOUT 00Z/SAT. EXPECT THAT WHILE
VISIBILITIES WILL IMPROVE CEILINGS WILL BE MVFR OR LOW VFR THROUGH
THE FORECAST PERIOD. MVFR STRATUS DECK WILL LIFT AT KBPI EARLY THIS
AFTERNOON. EXPECT CONDITIONS THERE AND AT KPNA TO REMAIN VFR THROUGH
THE FORECAST PERIOD. SOME PESKY STRATUS AROUND KRKS BUT BELIEVE THE
SUN WILL WIN OUT AND LEAVE VFR THROUGH TODAY. COLD FRONTAL SURGE
WILL BRING GUSTY EAST-NORTHEAST WIND TO KRKS BEGINNING BETWEEN
09Z/SAT AND 12Z/SAT. WHILE CONDITIONS WILL BE VFR THROUGH
18Z/SAT...POSSIBLE RETURN TO MVFR CONDITIONS WITH SNOW/WIND
COMBINATION BY 00Z/SUN OR SHORTLY THEREAFTER. WILL BE ADDRESSING
THIS MORE WITH THE 00Z TAF SET THIS AFTERNOON.

&&

.FIRE WEATHER...

A SOMEWHAT BUSY FORECAST PERIOD ACROSS THE AREA. SHOWER ACTIVITY
WILL REMAIN POSSIBLE OVER THE NORTHERN THIRD OF THE AREA AS A
DISTURBANCES MOVES ACROSS THE AREA IN THE CONTINUED NORTHWEST FLOW.
AFTER A VERY SLIGHT WARMING TODAY...TEMPERATURES WILL AGAIN COOL
SATURDAY AS AN AREA OF LOW PRESSURE MOVES SOUTH ALONG THE PACIFIC
COASTLINE. AS THIS SYSTEM PROGRESSES...IT WILL SPREAD ADDITIONAL
SHOWERS ACROSS SOUTHWESTERN WYOMING...WITH SOUTHERN WYOMING
EXPERIENCING THE BRUNT OF THE SHOWER ACTIVITY.

&&

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

&&

$$

SHORT TERM...BRANHAM
LONG TERM...PS
AVIATION...CNJ
FIRE WEATHER...BRANHAM





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