Area Forecast Discussion
Issued by NWS Riverton, WY

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000
FXUS65 KRIW 031711
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1110 AM MDT THU SEP 3 2015

.SHORT TERM...TODAY THROUGH SATURDAY NIGHT

A FEW SHOWERS MOVING TOWARDS WESTERN WYOMING THIS MORNING. MENTION
OF ISOLATED SHOWERS THROUGH THE EARLY MORNING...WITH CONDITIONS
EXPECTED TO IMPROVE DURING THE MID-LATE MORNING HOURS. A DRIER
SOUTHWEST FLOW TO DEVELOP OVER THE AREA TODAY. THE PACIFIC NORTHWEST
TROUGH CONTINUES TO DIG TODAY AS THE SYSTEM SLOWLY MOVES SOUTH. SOME
ENERGY WILL MOVE THROUGH THE FORECAST AREA THIS
AFTERNOON...GENERATING SOME ISOLATED TO SCATTERED SHOWERS AND
THUNDERSTORMS.COVERAGE LOOKS MOST FAVORABLE OVER THE NORTHERN
MOUNTAINS....AND REACHING INTO THE JACKSON VALLEY.

AS THE AREA OF LOW PRESSURE CONTINUES TO DIG SOUTH ON
FRIDAY...ANOTHER PUSH OF MOISTURE WILL MOVE INTO THE STATE FROM THE
SOUTHWEST. SHOWERS AND THUNDERSTORMS ARE POSSIBLE...MAINLY OVER THE
MOUNTAIN LOCATIONS. SOME MODEL VARIANCE DEMONSTRATED ON FRIDAY. THE
GFS SHOWS THAT THE PUSH OF MOISTURE MAY BE STRONGER...WITH SHOWERS
COVERING A LOT OF THE FORECAST AREA. HOWEVER...THIS MODEL IS THE
CURRENT OUTLIER IN A SEA OF DRIER MODEL SOLUTIONS. LEFT THE LIMITED
PRECIPITATION FORECAST FOR NOW.

WEATHER BECOMES MORE INTERESTING SATURDAY AFTERNOON AS A STRONG COLD
FRONT MOVES TOWARDS THE STATE. THIS FRONT IS ASSOCIATED WITH THE
AREA OF LOW PRESSURE WHICH WILL BE WORKING ITS WAY THROUGH THE
INTERMOUNTAIN WEST THROUGH THE WEEKEND. ASIDE FROM COLDER
TEMPERATURES...MODELS INDICATE DECENT STORM COVERAGE SATURDAY
AFTERNOON. AS THE FRONT MOVES FURTHER INTO THE STATE SATURDAY
NIGHT...EXPECTING SHOWER COVERAGE TO ALSO INCREASE...WITH SCATTERED
TO NUMEROUS SHOWERS AND THUNDERSTORMS ANTICIPATED SATURDAY EVENING.
THE BEST COVERAGE LOOKS TO BE WEST OF THE DIVIDE THROUGH THE EVENING
HOURS. THE WAVE OF LOW PRESSURE WILL LIFT NORTHEAST AS IT MOVES
THROUGH WYOMING OVER THE WEEKEND...HELPING TO KEEP SHOWER ACTIVITY
GENERALLY ACROSS THE NORTHERN HALF OF CENTRAL AND WESTERN WYOMING.

.LONG TERM...SUNDAY THROUGH THURSDAY

A STRONG PACIFIC COLD FRONT SHOULD BE THROUGH THE ENTIRE FORECAST
AREA OR NEARLY SO BY 12Z SUNDAY...WITH WINDY TO VERY WINDY
WESTERLY WINDS IN TYPICAL SPOTS SUCH AS THE LEE SIDE OF MOUNTAIN
RANGES AND IN THE CENTRAL/SOUTHERN WIND CORRIDORS. MUCH OF THE
PRECIPITATION BY SUNRISE SUNDAY SHOULD BE NORTH OF THE FORECAST
AREA ACROSS MONTANA...BUT THERE SHOULD BE SOME LINGERING SHOWERS
OVER THE NORTHWEST AND POSSIBLY EXTREME NORTH. THIS SYSTEM WILL
BE COLD ENOUGH FOR ANY LINGERING PRECIP SUNDAY MORNING TO BE
MAINLY SNOW ABOVE 7000 FEET ACROSS THE NORTHWEST. THE WIND
COMBINED WITH A DRY ATMOSPHERE IN WAKE OF THE COLD FRONT WILL LEAD
TO ELEVATED AND PERHAPS CRITICAL FIRE WEATHER CONDITIONS ACROSS
PORTIONS OF FREMONT...NATRONA AND SWEETWATER COUNTIES.

MONDAY THROUGH WEDNESDAY...MEDIUM RANGE MODELS ARE SHOWING ONE OR
TWO SHORTWAVE TROUGHS OF VARYING INTENSITIES/TRACKS DIVING
SOUTHEAST OUT OF BRITISH COLUMBIA ACROSS THE NORTHERN
ROCKIES/PLAINS. THE 00Z GFS SHOWS ONE STRONGER AND SLOWER SYSTEM
WHILE THE ECMWF IS SHOWING A COUPLE WEAKER SYSTEMS. HAVE BROAD
BRUSHED SLIGHT MOUNTAIN POPS OVER THE NORTHWEST/NORTH FROM MONDAY
AFTERNOON THRU WEDNESDAY NIGHT TO ACCOUNT FOR THESE SYSTEMS.

TEMPERATURES WILL BE SEASONAL TO BELOW AVERAGE THROUGH THE
EXTENDED.

&&

.AVIATION.../18Z ISSUANCE/

VFR CONDITIONS WILL PREVAIL THROUGH THE FORECAST PERIOD. AN UPPER
LEVEL DISTURBANCE WILL LIFT NE FROM COLORADO ACROSS EASTERN WYOMING
IN THE EVENING...SPREADING ISOLATED SHOWERS AND THUNDERSTORMS MAINLY
VCNTY AND SOUTH OF A KRKS-KCPR LINE. ANOTHER AREA OF SHOWERS AND
THUNDERSTORMS WILL BE ALONG/NEAR A FRONTAL BOUNDARY NEAR THE
MONTANA/WYOMING BORDER THAT SHOULD SAG SOUTHWARD INTO
NORTHERN/NORTHWESTERN WYOMING THIS EVENING/OVERNIGHT. ACTIVITY NEAR
THIS BOUNDARY WILL BE ISOLATED TO WIDELY SCATTERED.

&&

.FIRE WEATHER...

SOUTHWEST FLOW WITH DAILY MOISTURE PUSHES WILL REMAIN THE PATTERN
OVER THE NEXT COUPLE DAYS. HUMIDITIES ACROSS SOME OF THE CENTRAL
FIRE ZONES MAY DECREASE INTO THE UPPER TEENS...BUT ARE GENERALLY
ANTICIPATED TO REMAIN ABOVE CRITICAL LEVELS. ADDITIONALLY... THOSE
LOCATIONS WHICH MAY EXPERIENCE THE LOWEST HUMIDITY LEVELS WILL
EITHER SEE TOO LIGHT OF WIND...OR WILL HAVE SOME HUMIDITY RECOVERY
BEFORE WIND STARTS UP. THE PASSAGE OF A COLD FRONT SATURDAY IS THE
NEXT BIGGEST STORY. AHEAD OF THE FRONT...CONDITIONS WILL START TO
COOL WITH INCREASING HUMIDITY. SHOWERS WILL SPREAD ACROSS THE
NORTHERN THIRD OF THE STATE WITH THE MOVEMENT OF THE COLD
FRONT THROUGH SATURDAY NIGHT.

&&

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

&&

$$

SHORT TERM...BRANHAM
LONG TERM...WM
AVIATION...JB
FIRE WEATHER...BRANHAM


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