Area Forecast Discussion
Issued by NWS Riverton, WY

Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

037
FXUS65 KRIW 011759 AAA
AFDRIW

AREA FORECAST DISCUSSION...UPDATE
NATIONAL WEATHER SERVICE RIVERTON WY
1100 AM MST MON FEB 1 2016

.SHORT TERM...TODAY THROUGH WEDNESDAY NIGHT

TODAY AND TONIGHT...A LARGE UPPER LOW ENTERS THE FOUR CORNERS AREA
AROUND NOON WITH WRAP AROUND MOISTURE MAKING IT AS FAR WEST AS THE
WIND RIVER BASIN AND AS FAR NORTH AS JOHNSON COUNTY. SINCE THE WIND
RIVER BASIN WILL BE ON THE EDGE OF THE PRECIPITATION AND THERE WILL
BE SOME DOWNSLOPING OFF OF THE OWL CREEKS...WENT AHEAD AND KEPT
AREAS NORTH OF LANDER OUT OF THE ADVISORY EVEN THOUGH THE HUDSON
AREA WILL LIKELY ACCUMULATE MORE THAN 3 INCHES...IF THE WINDS OFF OF
THE OWL CREEKS ARE NOT AS STRONG AS ANTICIPATED...RIVERTON COULD
ACCUMULATE ADVISORY LEVEL SNOWS. IT IS DIFFICULT TO TELL AT THIS
TIME WHERE THAT GRADIENT WILL SET UP...SO STAY TUNED.

ANOTHER TRICKY AREA WILL BE CASPER AND EASTERN SWEETWATER COUNTY.
THE HEAVIEST SNOW AND STRONGEST WINDS LOOK LIKE THEY WILL STAY ALONG
INTERSTATE 80 EAST OF ROCK SPRINGS AND CASPER WILL ALSO GET SEVERAL
INCHES OF SNOW OUT OF THIS STORM WITH OVER 3 INCHES LIKELY ACROSS
THE METRO AREA...AND UP TO 10 INCHES ON CASPER MOUNTAIN. 700MB FLOW
IS A LITTLE TOO EASTERLY FOR CASPER...AS IS THE SURFACE FLOW...BUT
THE LAYER TEMPERATURES OVER CASPER SUPPORT GOOD DENDRITIC
GROWTH...THE LONG PERIOD OF TIME THAT THE CASPER AREA SHOULD BE IN
THE HEAVIER SNOW...AND THE ADDED IMPACT OF THE WIND ON THE FALLING
SNOW WOULD PUT IT IN THE HIGH END ADVISORY TO LOW END WARNING
CRITERIA. THIS IS ANOTHER AREA THAT SHOULD BE WATCHED CLOSELY FOR
POTENTIAL UPDATES LATER THIS MORNING...BUT DID NOT SEE ENOUGH
CHANGES TO THE FORECAST TO JUSTIFY AN UPGRADE AT THIS TIME. EITHER
WAY...EXPECT THE EVENING COMMUTE TO BE DIFFICULT AND SLOW TODAY.

SOUTH PASS IS ALSO EXPECTED TO BE IMPACTED BY THIS STORM NEAR
BLIZZARD CONDITIONS POSSIBLE AT TIMES...THOUGHT ABOUT ADDING THE
OTHER SIDE OF THE WIND RIVERS TO THE ADVISORY BUT THERE WILL BE
CONSIDERABLE DOWNSLOPING FOR MUCH OF THE ZONE AND THOUGHT THAT THE
ADVISORY ALONG THE UPSLOPE PORTION OF THE WIND RIVERS ADEQUATELY
COVERS THE THREAT FOR SOUTH PASS. REGARDLESS OF WHETHER THERE IS AN
ADVISORY OR WARNING...TRAVEL WILL BE DIFFICULT TO IMPOSSIBLE FOR
HIGH PROFILE VEHICLES AND LIGHT TRAILERS ALONG PORTIONS OF
INTERSTATES 80 AND 25 AND THEIR FEEDER ROUTES...AS WELL AS OVER
SOUTH PASS AS THE DAY GOES ON.

MOST OF THE DYNAMIC FORCING WITH THE LOW WILL REMAIN TO THE SOUTH
BUT THERE WILL BE SOME DIFFUSE FORCING FOR ASCENT ALONG THE FRONT
END OF THE TROUGH AS IT DIGS ACROSS THE INTERMOUNTAIN WEST. THIS
SYSTEM WILL BE LESS CONVECTIVE WHEN COMPARED TO THE LAST SYSTEM SO
THAT AT LEAST REMOVES ONE ELEMENT OF CHAOS. ASIDE FROM THE
AFOREMENTIONED AREAS...THERE WILL BE AT LEAST A CHANCE FOR LIGHT
SNOW NORTH AND WEST OF THE ADVISED AREAS WITH GENERALLY LESS THAN AN
INCH OF SNOW EXPECTED.

TUESDAY...GRADUAL DRYING AND SOME CLEARING AS OUR STORM PULLS OUT
INTO THE PLAINS WITH OCCASIONAL FLURRIES LEFTOVER INTO THE
AFTERNOON. CHILLY NORTHWEST FLOW WILL TAKEOVER WITH A CHANCE FOR A
WEAK DISTURBANCE PASSING THROUGH LATE TUESDAY NIGHT...WHICH COULD
DELIVER A LITTLE MORE THAN A FLURRY ACROSS THE NORTH AND WEST...IN
ADDITION TO WIND CHILLS BELOW ZERO ACROSS WESTERN AND CENTRAL
WYOMING...WITH SOME WIND CHILLS APPROACHING 20 BELOW ALONG THE
INTERSTATE 80 CORRIDOR AND IN THE WESTERN MOUNTAINS.

WEDNESDAY...RIDGING BUILDS INTO THE REGION WITH SOME FLATTENING LATE
WEDNESDAY NIGHT. WAA AND DIFLUENT FLOW AHEAD OF AN APPROACHING SHORT
WAVE WILL INCREASE THE CHANCE FOR SNOW IN THE WESTERN MOUNTAINS
LATE...OTHERWISE WEDNESDAY WILL BE BREEZY...ESPECIALLY IN THE CODY
FOOTHILLS AND ACROSS THE SOUTH...AND COOL AS MILD AIR ALOFT TAKES
ITS TIME FILTERING IN FROM THE WEST.

.LONG TERM...THURSDAY THROUGH MONDAY

A WEATHER SYSTEM WILL MOVE THROUGH THE REGION THURSDAY AND THURS
NIGHT...EXITING THE EASTERN ZONES FRIDAY MORNING. THE SYSTEM IS
WEAKER ON THE GFS/ECMWF MODELS TONIGHT THAN LAST NIGHT...THUS
IMPACT MAY BE LESS. KEEP BEST CHANCE OF SNOW IN THE MOUNTAINS WITH
LESSER CHANCE LOWER ELEVATIONS. FRIDAY AND SATURDAY LOOK DRY FOR
MOST PLACES. SOME LIGHT SNOW MAY DEVELOP IN NW WY SATURDAY
AFTERNOON AHEAD OF THE NEXT WEATHER SYSTEM. HIGH TEMPS THURSDAY
SEASONABLY COLD...THEN SLIGHTLY MILDER FRIDAY AND SATURDAY.

THE WEATHER PATTERN BECOMES HIGHLY AMPLIFIED SATURDAY NIGHT
THROUGH NEXT SUNDAY AND MONDAY. A BIG RIDGE OFF THE WEST COAST
OCCURS WHILE A BIG TROUGH DEVELOPS IN THE PLAINS AND GREAT LAKES.
THE VERY COLD AIR WILL HEAD OFF INTO THAT REGION BUT THERE WILL BE
SOME COLDER AIR MOVING INTO WY FOR SUNDAY AND MONDAY. THE ECMWF
MODEL IS COLDER THAN THE GFS THIS FAR OUT. LEANED TOWARD THE
COLDER ECMWF MODEL FOR HIGHS AND LOWS NEXT SUNDAY AND MONDAY. AS
FOR SNOW CHANCES...SOME LIGHT SNOW IS EXPECTED SUNDAY WITH THE
ONSET OF THE COLDER AIR. THEN SCATTERED LIGHT SNOW TO OCCUR
MONDAY. PLENTY OF TIME TO WATCH THIS PATTERN CHANGE AND MAKE
ADJUSTMENTS AS NEEDED.

&&

.AVIATION.../18Z ISSUANCE/

SNOW AND CONSIDERABLE BLOWING SNOW WILL CONTINUE TODAY AND TONIGHT
AS A LARGE WINTER STORM IMPACTS THE CENTRAL AND SOUTHERN ROCKIES.
WIDESPREAD IFR CONDITIONS IN VSBY REDUCTIONS AND LOW CIGS REMAIN FOR
MUCH OF THE TAF FORECAST PERIOD ALONG AND SOUTHEAST OF KEMM-KLND-
KBYG LINE. STRONG NORTH TO NORTHEAST WINDS WILL OCCUR IN MUCH OF THE
SAME AREA CAUSING THE BLOWING SNOW. AIRFIELD MINIMUMS COULD OCCUR
FOR SEVERAL HOURS AT KRKS DUE TO VSBY RESTRICTIONS IN SN AND BLSN
WITH THE BEST CHANCE BETWEEN 19Z AND 01Z. ALSO CPR COULD ALSO SEE
AIRFIELD MINIMUMS...BUT CONFIDENCE IS NOT AS HIGH AS KRKS. HAVE KEPT
BOTH TERMINALS JUST ABOVE AIRFIELD MINIMUMS FOR NOW. KPNA MAIN ISSUE
WILL BE LOW LEVEL WIND SHEAR FROM THE NORTHEAST TODAY...AS
DOWNSLOPING SHOULD KEEP THEM DRY. KJAC TERMINAL WILL BE LEAST
IMPACTED FROM THIS SYSTEM WITH ONLY SOME SNOW SHOWERS IMPACTING THE
AREA...WITH VFR CONDITIONS EXPECTED WITH A BREEZE FROM THE NORTH.

PLEASE SEE THE AVIATION WEATHER CENTER FOR THE LATEST INFORMATION ON
ICING AND TURBULENCE FORECASTS.

&&

.FIRE WEATHER...

PERIODS OF SNOW AND GUSTY WINDS ACROSS THE FORECAST AREA WILL RESULT
IN FAIR TO GOOD SMOKE DISPERSION TODAY...ESPECIALLY ACROSS CASPER
AND RAWLINS DISPATCH. MIXING HEIGHTS LOWER A BIT AFTER TODAY BUT
VARIABLE CLOUD COVER AND OCCASIONAL BREEZES WILL KEEP SMOKE
DISPERSION FROM BOTTOMING OUT ACROSS THE BOARD...THOUGH THERE WILL
BE SOME INVERSIONS RETURNING TO VALLEYS AND BASINS AFTER
TONIGHT...WITH SOME IMPROVEMENT DURING THE DAY. THERE WILL BE A FEW
SHOTS AT SOME MORE SNOW AS THE WEEK MOVES ALONG BUT NOTHING
ORGANIZED OR WIDESPREAD ON THE HORIZON. A STRONG RIDGE COULD BE
BUILDING IN NEXT WEEK...WITH DRIER AND CALMER WEATHER
POSSIBLE...IN ADDITION TO SOME STRONG INVERSIONS IN ANY SNOW
COVERED VALLEYS OR BASINS.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...

WINTER WEATHER ADVISORY FROM 9 AM THIS MORNING TO 9 AM MST
TUESDAY FOR WYZ015-018>020-022.

WINTER WEATHER ADVISORY UNTIL 9 AM MST TUESDAY FOR WYZ027>030.

&&

$$

SHORT TERM...ALLEN
LONG TERM...AR
AVIATION...WM/LIPSON
WEATHER...ALLEN



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.