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350
FXUS65 KRIW 011723
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1023 AM MST SUN FEB 1 2015

.SHORT TERM...TODAY THROUGH TUESDAY NIGHT (ISSUED AT 310 AM MST)

THE NORTHERN STREAM SHORTWAVE IS NOW MAKING ITS WAY ACROSS
NORTHERN AND EASTERN WY AND HAS DRIVEN A COLD FRONT SOUTH TO THE
CONTINENTAL DIVIDE. THE INITIAL SHOT OF SNOWFALL FROM THE ASCT
COLD FRONT WAS A QUICK HITTER...AFFECTING AREAS MAINLY EAST AND
NORTH OF RIVERTON. BEHIND THE FRONT...NARROW NORTHWEST SOUTHEAST
ORIENTED SNOW BANDS HAVE SET UP WITH THE MOST PROMINENT ONE
SITUATED OVER CAMPBELL CORNER BETWEEN RIVERTON AND SHOSHONI AT THE
TIME OF THIS WRITING. NVA BEHIND THIS WEATHER FEATURE WILL PUSH
THE CLOUDS AND SNOWFALL OFF TO THE EAST LATER THIS MORNING. HIGH
TEMPERATURES TODAY BEHIND THE COLD FRONT WILL COOL DOWN THE MOST
FROM SATURDAYS HIGHS IN JOHNSON COUNTY WHICH IS IN THE MOST DIRECT
PATH OF THE COLD AIR ADVECTION. HIGH TEMPS WILL LIKELY REMAIN IN
THE UPPER 20S AT THE LOWER ELEVATIONS THERE TODAY. EXCEPT FOR MUCH
OF SWEETWATER COUNTY...ALMOST ALL AREAS EAST AND WEST OF THE
DIVIDE WILL REMAIN BELOW FREEZING TODAY. MOSTLY SUNNY SKIES ARE
EXPECTED BY LATE MORNING EAST OF THE DIVIDE TODAY. THE RIDGE THAT
IS AMPLIFIED ALONG THE PACIFIC COAST WILL FLATTEN CONSIDERABLY BY
THE TIME IT REACHES THE ROCKIES LATER TODAY. THE CIRCULATION OVER
45N/145W WILL EJECT A PACIFIC SHORTWAVE THAT WILL WEAKEN AS IT
RIDES UP AND OVER THE FLATTENED RIDGE AND APPROACHES WYOMING FROM
THE WEST NORTHWEST AS THE UPPER FLOW BACKS TO A MORE DIRECT FLOW
OFF THE PACIFIC. THIS WILL RESULT IN MAINLY LIGHT SNOWFALL
BREAKING OUT IN FAR WESTERN WY TONIGHT. THE SNOWFALL WILL TAPER
OFF IN THE FAR WEST LATER MONDAY BEFORE MORE SIGNIFICANT SNOWFALL
ARRIVES MONDAY NIGHT WITH THE POTENTIAL FOR SIGNIFICANT SNOWFALL
ACCUMULATION WITH SOME OF IT SPREADING INTO SWEETWATER COUNTY.
THEN AFTER A SHORT RESPITE FROM THE FAR WESTERN WY SNOWFALL
TUESDAY ALONG WITH A POSSIBLE BRIEF MIXTURE OF RAIN IN THE LOWER
ELEVATIONS...MORE SIGNIFICANT SNOWFALL IS EXPECTED TUESDAY NIGHT
WITH A MORE ROBUST SHORTWAVE ALONG WITH ADDITIONAL ISENTROPIC
LIFT. THIS ISENTROPIC LIFT WILL LIKELY SPREAD INTO SWEETWATER
COUNTY WITH LIGHT SNOW SPREADING INTO SWEETWATER COUNTY ONCE
AGAIN. A COLD FRONT WILL BE ASSOCIATED WITH THIS TUESDAY NIGHT
FEATURE AND WILL HELP SPREAD SOME SNOWFALL TO AREAS EAST OF THE
DIVIDE LATE TUESDAY NIGHT ALONG WITH SOME WEAK Q VECTOR FORCING.
OVERALL...MONDAY AND TUESDAY WILL FEATURE SEASONABLY MILD
CONDITIONS WITH THE WARMEST TEMPERATURES EXPECTED EAST OF THE
DIVIDE WITH DOWNSLOPE FLOW. AS FOR WIND...THE GRADIENT DOES NOT
DIRECTLY INDICATE HIGH WIND EARLY NEXT WEEK BUT H7 WINDS DO
INCREASE TO 50 KNOTS ON TUESDAY SO THE SOUTHERN WIND CORRIDOR AND
THE HIGHER ELEVATIONS WILL PROBABLY SEE THE HIGHEST WINDS TUESDAY
BUT BREEZY CONDITIONS WILL PERSIST IN THESE AREAS MONDAY THROUGH
TUESDAY NIGHT. THE FROUDE NUMBER IS SLATED TO BE AROUND ONE
TUESDAY NIGHT AROUND CLARK SO THAT AREA COULD SEE THE STRONGER
WINDS DURING THAT PERIOD.

.LONG TERM...WEDNESDAY THROUGH SUNDAY

ACTIVE START TO THE MEDIUM RANGE PERIOD WITH EXPECTED MOIST WNW FLOW
AND SHORTWAVE INTERACTING WITH A STRONG COLD FRONT EAST OF THE
DIVIDE. COULD SEE A DECENT BAND OF SNOW ALONG AND BEHIND THE FRONT
WHERE THE FORCING ALOFT INTERSECT THIS FRONT. INCREASED POPS TO AT
LEAST CHANCE IN THE LOWER ELEVATIONS OF CENTRAL WYO THROUGH AT LEAST
THE MORNING BEFORE SOME IMPROVEMENT LATE. LOWERED HIGHS ALSO BEHIND
THIS FRONT. BRIEF RIDGING THURSDAY BEFORE FLOW STARTS TO FLATTEN
WITH STRONG...MOIST WLY FLOW DEVELOPING FOR FRIDAY THROUGH THE
WEEKEND...ESPECIALLY WITH THE GFS SOLUTION. THE ECMWF HAS MORE
RIDGING SUNDAY FOR A DRY AND MILD DAY WITH PCPN NOT RETURNING UNTIL
NEXT MONDAY MORNING. STUCK WITH THE MODEL BLEND WHICH SHOWS
INCREASING CHANCES OF MTN SNOW OUT WEST AGAIN NEXT SUNDAY NIGHT.
SO GOING WITH INCREASE POPS FRIDAY NIGHT CONTINUING THROUGH SATURDAY
WITH A POTENTIAL BREAK SATURDAY NIGHT INTO SUNDAY BEFORE ANOTHER
ROUND HITS SOMETIME SUNDAY OR SUNDAY NIGHT. THE MAIN WEATHER EAST OF
THE DIVIDE FOR MUCH OF THIS PERIOD WILL BE MILD EARLY FEBRUARY
TEMPERATURES WITH CONSIDERABLE WIND. POTENTIAL FOR SOME HIGH WINDS
IN THE WIND CORRIDOR FRIDAY THROUGH SUNDAY AND ALONG THE CODY
FOOTHILLS. H7 TEMPS LOOKS TO BE ABOVE 0C FRIDAY AND AGAIN SUNDAY
WITH A BRIEF COOLDOWN SATURDAY BEHIND OUR SAT SHORTWAVE THAT
PRODUCES ALL THE SNOW IN THE WRN MTNS BEFORE WARMING AGAIN SUNDAY.
ENOUGH GRADIENT AND WARM AIR ALOFT TO MIX MUCH OF THE AREA PRODUCING
HIGHS IN THE 40S AND 50S FOR MUCH OF THE LATTER HALF OF THE
EXTENDED. COLDEST DAY WILL BE WEDNESDAY WITH A CHILLY START TO
THURSDAY THEN CONSIDERABLY WARMER ON FRIDAY. MOST LIKELY A LITTLE
DROP SATURDAY THEN WARMER AGAIN NEXT SUNDAY.

&&

.AVIATION.../18Z ISSUANCE/

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

VFR CONDITIONS WILL PREVAIL OVER THE REGION FROM 19Z THROUGH 18Z
MONDAY. A SOUTHWEST WIND WILL PICK UP THROUGH THE WIND CORRIDOR
KRKS-KCPR AND ALONG THE EASTERN FOOTHILLS OF THE DIVIDE FROM 00Z MON
THROUGH 18Z MONDAY.

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

VFR CONDITIONS WILL PREVAIL THROUGH 00Z. CIGS ARE EXPECTED TO LOWER
ACROSS THE FAR WEST AFTER 00Z WITH MVFR/IFR CIGS AND -SN PREVAILING
ACROSS MUCH OF THE WEST...VCNTY AND NORTH OF A KPNA-KAFO LINE
THROUGH 18Z MONDAY. LCL MVFR/IFR -SN WILL BE ENCOUNTERED FURTHER
SOUTH ALONG KBPI-KRKS ROUTES AFTER 03Z MON THROUGH 18Z MONDAY.

&&

.FIRE WEATHER...

A WEATHER SYSTEM WILL BRING SOME LIGHT SNOW EAST OF THE DIVIDE THIS
MORNING. VALLEY FOG IS EXPECTED IN THE FAR WEST THIS MORNING. THEN
MOSTLY DRY THIS AFTERNOON THROUGH MONDAY EAST OF THE DIVIDE. WEST
OF THE DIVIDE WILL BE DRY THIS MORNING. LIGHT SNOW DEVELOPS OVER
THE NORTHWEST MOUNTAINS THIS AFTERNOON. PERIODS OF SNOW FOR THE
WESTERN MOUNTAINS AND FAR WEST VALLEYS TONIGHT THROUGH TUESDAY
NIGHT.

&&

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

&&

$$

SHORT TERM...LIPSON
LONG TERM...PS
AVIATION...AEM/AR
FIRE WEATHER...LIPSON













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