Area Forecast Discussion
Issued by NWS Riverton, WY

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000
FXUS65 KRIW 180520
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1120 PM MDT FRI OCT 17 2014

UPDATE...UPDATED TO ADD 06Z AVIATION DISCUSSION.

.SHORT TERM...TONIGHT THROUGH SATURDAY (ISSUED AT 143 PM MDT)

PATTERN VERY CLOSE TO THAT OF THURSDAY...WITH SAT IMAGERY SHOWING
MODEST RIDGING WEST WITH A COUPLE OF WEAK UPR WAVES UPSTREAM MOVING
THIS WAY...ONE JUST NOW TOPPING THE RIDGE AND MOVING ACROSS WRN
WY...THE OTHER JUST NOW PUSHING EWD ACROSS NV. THE SFC SHOWS HIGH
PRESSURE IN PLACE ACROSS MOST OF THE FA. SFC WINDS ON THE LOW SIDE
UNDER THESE CONDITIONS...REMAINING MOSTLY SO THRU THE FCST PERIOD.
THE ONLY REAL EFFECT THE UPR WAVES WILL HAVE ON THE FCST AREA AS
THEY MOVE THRU THE UPR FLOW OVER THE NEXT DAY WILL BE TO BRING
PERIODIC INCREASES IN MID/UPR CLOUDINESS. OTHERWISE...H7 TEMPS WILL
WARM 2-3 DEGREES OVR THE NEXT 24 TO 36 HRS...WITH THE SFC
CORRESPONDINGLY WARMING 5+ DEG OVER THOSE OF TODAY FOR MOST
LOCATIONS.

.LONG TERM...SATURDAY NIGHT THROUGH FRIDAY

LONG WAVE LOW PRESSURE TROUGHS OFF THE WEST COAST AND OVER THE
EASTERN U.S. WILL REMAIN IN PLACE THROUGH THE EXTENDED FORECAST.
THIS PLACES A LARGE HIGH PRESSURE RIDGE OVER THE GREAT PLAINS.
WESTERN AND CENTRAL WYOMING ENDS UP WITH WEST TO SOUTHWEST FLOW
ALOFT.  MODELS INDICATE SHORT WAVE LOW PRESSURE TROUGHS SKIRT TO
THE NORTH OF WYOMING OVER THE NORTHERN ROCKIES ACROSS MONTANA AND
SOUTHERN CANADA AND TO THE SOUTH ACROSS CENTRAL AND SOUTHERN GREAT
BASIN.  SATURDAY NIGHT THROUGH MONDAY NIGHT LOOKS DRY AND RELATIVELY
MILD.  ONE OF THE NORTHERN SHORT WAVE TROUGHS LOOKS TO BE STRONG
ENOUGH TO BRING SOME SHOWERS TO THE WESTERN AND NORTHERN MOUNTAINS
AND COOLS TEMPERATURES FOR TUESDAY NIGHT AND WEDNESDAY. THEN
FORECAST DRIES OUT AGAIN WITH WARMING THROUGH FRIDAY.  MAIN SPREAD
IN THE EXTENDED MODELS OCCURS ACROSS THE NORTHERN ROCKIES...MONTANA
AND SOUTHERN CANADA IN TRACK OF SHORT WAVE TROUGHS WHERE DIFFERENCES
IN TIMING OF SHORT WAVE TROUGHS INCREASES UNCERTAINTY.

&&

.AVIATION.../00Z ISSUANCE/

ALL TERMINALS TO BE VFR THROUGH THE FORECAST PERIOD. SHORTWAVE NEAR
THE CALIFORNIA COAST WILL SPREAD MID-HIGH CLOUDS ACROSS THE FORECAST
AREA THROUGH SATURDAY AFTERNOON AS IT DIVES TO THE DESERT SOUTHWEST.
TAIL END OF A WEAK NORTHERN STREAM WAVE WILL SWEEP EAST ACROSS WYO
AFTER 00Z/SUN. SURFACE WINDS WILL BRIEFLY GO TO THE NORTHWEST AND
HIGH CLOUDS WILL PUSH EAST. SURFACE WINDS WILL BE LESS THAN 10KTS
EXCEPT FOR KCPR WHERE SOUTHWEST WIND G14KT POSSIBLE 17Z-21Z/SAT.

&&

.FIRE WEATHER...

FIRE DANGER IS LOW...AND WILL REMAIN RELATIVELY LOW THROUGH THE
WEEKEND ACROSS THE ENTIRE FORECAST AREA. COOLER TEMPERATURES AND LOW
WIND SPEEDS CONTINUE FOR ANOTHER DAY AS HIGH PRESSURE LINGERS ACROSS
THE REGION. SATURDAY AND SUNDAY...A BUILDING UPPER LEVEL RIDGE WILL
BRING SOME WARMER TEMPERATURES FOR THE WEEKEND. HOWEVER MID-LEVEL
MOISTURE WILL ALSO BE ON THE INCREASE...KEEPING SOME CLOUDS IN
THE SKY AND RELATIVE HUMIDITY VALUES ABOVE CRITICAL LEVELS FOR
THE MOST PART. WINDS WILL BECOME MORE WESTERLY OVER THE
WEEKEND...HOWEVER SPEEDS WILL REMAIN ON THE LOW SIDE.

&&

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

$$

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








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