Area Forecast Discussion
Issued by NWS Riverton, WY

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FXUS65 KRIW 281731
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1131 AM MDT TUE OCT 28 2014

.SHORT TERM...TODAY THROUGH THURSDAY NIGHT

SAT IMAGERY SHOWS UPR TROF OVR THE CENTER OF THE CONUS WITH RIDGES
OVR BOTH COASTS. WEAK JET FLOW ROUGHLY FOLLOWS THE LOWER PORTION OF
THIS PATTERN WITH THE NOSE OF AN UPSTREAM JET STREAK...DUE TO ARRIVE
NEARBY ON WEDNESDAY...CURRENTLY LOCATED NEAR 41.5/-135 LAT LON. SFC
HAS HIGH PRESSURE SLOWLY BUILDING IN FROM THE WEST.

A LITTLE WARMER EVEN UNDER NW FLOW...WITH DRYING AND PLENTY OF
SUNSHINE AROUND FOR MOST LOCATIONS IN ADDITION TO H7 TEMPS WARMING
ABOUT 5 DEG C THRU THE DAY. OTHERWISE THERE ARE TWO SHORT STORIES OF
MINOR CONCERN THRU THE FCST PERIOD. THE FIRST HAS TO DO WITH
INCREASING WINDS OVR THE USUAL SPOTS ON WEDNESDAY AHEAD OF AND WITH
ARRIVAL OF THE EMBEDDED JET STREAK/SW...MENTIONED ABOVE...MOVING
THRU THE NW FLOW. SFC RESPONSE WILL ALSO HELP TO INCREASE WINDS...AS
WARMER LL TEMPS AND SOME DOWNSLOPING CREATE A WEAK TROF OVR THE
CNTRL BASINS AND ALSO E OF THE BIGHORN MOUNTAINS. THIS INCREASING P
GRAD WILL BE ACCOMPANIED BY INCREASED THERMAL AND OMEGA GRAD IN/NEAR
THE FOOTHILLS OF NRN AND CNTRL MOUNTAINS...ESPECIALLY THE ABSAROKAS.
THIS PATTERN WILL ALSO PRODUCE FAVORABLE MOUNTAIN WAVE ACTION
SOMETIME AROUND MID-DAY (PLUS/MINUS) FOR A SHORT PERIOD.
ATTM...HOWEVER...IT APPEARS THAT EVENT CONDITIONS WILL BE MARGINAL
AND A HIGH WIND WATCH WILL NOT BE NEEDED AS PEAK GUSTS IN THE
MOUNTAINS LOOK TO TOP OUT AT AROUND 60 TO 65 MPH...WHILE THE CODY
FOOTHILLS SEE GUSTS OF 30 TO 45 MPH. PERHAPS AN ISOLATED GUST UP TO
55 MPH MAY BE FOUND NEAR CLARK WY. THE WIND CORRIDOR ACROSS THE
SOUTH AND SOUTHEASTERN FA WILL ALSO EXPERIENCE ENHANCED SFC FLOW BY
MID/LATE AFTERNOON AS THE P GRAD INCREASES BETWEEN HIGH PRESSURE IN
PLACE TO THE SW AND A BUILDING LEE TROF TO THE E. LARGELY
UNIDIRECTIONAL SFC/ALOFT FLOW AND INCREASING INSTABILITY UP THROUGH
700 MB WILL AID IN THE INCREASED WIND SPEED. HOWEVER...PEAK GUSTS
SHOULD TOP OUT AT BETWEEN 30 AND 40 MPH WITH A COUPLE OF ISOLATED
LOCATIONS ACHIEVING 45 TO 50 MPH GUSTS.

THE SECOND STORY...WHICH IS EVEN LESS OF AN EVENT WITH LITTLE
IMPACT...ALSO HAS TO DO WITH INCREASED FLOW IN THE MID AND UPR LVLS
ASSOCIATED THE APPROACH OF THE UPR JET/SW AND ITS ABILITY TO BRIEFLY
HELP SQUEEZE OUT A FEW EXTRA DROPS OF PRECIP OVR MAINLY WINDWARD
SLOPES OF THE NWRN WY MOUNTAIN AREAS. THE PROBLEM IS...MOISTURE WILL
BE FLEETING AND AS WELL AS MOSTLY LACKING...WITH NEAR SATURATION ON
WRN SLOPES ONLY ATTAINABLE OVR A COUPLE OF SHORT HOURS. GENERALLY LESS
THAN A TENTH OF AN INCH OF PRECIP IS EXPECTED AT BEST...GIVING
PERHAPS A QUICK INCH OR LESS OF SNOW OVR PREFERRED ISOLATED
LOCATIONS. OVERNIGHT WED AND THRU THE END OF THE FCST PERIOD...UPR
RIDGING ALOFT AND INCREASING PRESSURE AT THE SFC WILL STABILIZE THE
ATMOSPHERE AND LESSEN WIND CONCERNS...WITH ONLY CLOUDY SKIES WEST
AND NORTH...AND PARTLY CLOUDY SKIES ELSEWHERE THE ONLY REAL WEATHER
OF THE PERIOD.

.LONG TERM...FRIDAY THROUGH TUESDAY

RIDGE AXIS OVERHEAD TO BEGIN THIS PERIOD FOR A MILD...DRY HALLOWEEN
WITH SOME WIND INCREASING AS THE DAY WEARS ON. ALTHOUGH THE SLOWER
ECMWF WOULD RESULT IN LESS WIND THAN THE FASTER GFS. WITH THE
STRENGTH OF THE RIDGE TO THE EAST...THE SLOWER ECMWF MAY BE END UP
BEING CORRECT IN TIMING. EITHER WAY...MOST OF THE LOWER ELEVATIONS
WILL HAVE HIGHS IN THE 60S FRIDAY WITH UPPER 40S AND 50S FOR MOST
OF THE HIGHER ELEVATIONS. THE NEXT STORM SYSTEM TO DEAL WITH IS
CURRENTLY OVER THE ERN ALEUTIANS. MODELS ARE IN GENERAL AGREEMENT
WITH THE EVOLUTION EXCEPT FOR THE TIMING. LEANING CLOSE TO THE
ECMWF BUT NOT QUITE AS SLOW BASED ON COLLABORATION. SYSTEM LOOKS
QUITE DYNAMIC WITH INCREASING QG FORCING AND POTENTIAL LEFT EXIT
REGION JET DYNAMICS AS IT MOVES THROUGH LATER SATURDAY INTO
SATURDAY EVENING WITH SWRN WYOMING TAKING THE BRUNT AS THE DAY
WEARS ON SATURDAY WITH WIDESPREAD RAIN AND SNOW SHOWERS AND LINE
OF THUNDERSTORMS QUITE POSSIBLE. AS THE UPPER LOW LIFTS NE
OVERNIGHT...SHOULD SEE WIDESPREAD SNOW ALONG AND NW OF THE TRACK
WITH THE PEAK BEING OVER OUR NWRN MOUNTAINS. POTENTIAL FOR SOME
DECENT SNOW AMOUNTS IN A SHORT AMOUNT OF TIME. SYSTEM LIFTS NE
INTO MT AND WRN ND ON SUNDAY WITH DECREASING CHANCES OF PCPN
ACROSS THE AREA. LINGERING LONGEST IN THE MOUNTAINS. WEAK
SHORTWAVE IN THE NW FLOW WILL HAVE TO BE WATCHED FOR MONDAY BUT
FOR NOW ONLY 20-30 POPS COVER THE NW. COLD AIR BEHIND THIS SYSTEM
SHOULD RESULT IN A COUPLE COLD MORNINGS WITH LOWS MAINLY 20S EAST
AND TEENS WEST. NW FLOW WILL CONTINUE INTO TUESDAY BUT SIGNIFICANT
DIFFERENCES ON AMOUNT OF UPSTREAM RIDGING WITH THE NEXT SYSTEM
MOVING INTO THE ERN PACIFIC. TEMPERATURES WILL LIKELY STRUGGLE TO
THE NEAR NORMAL RANGE ON TUESDAY. UPPER 40S TO LOWER 50S EAST AND
MAINLY 40S WEST.

&&

.AVIATION.../18Z ISSUANCE/

VFR CONDITIONS EXPECTED THROUGH THE MAJORITY OF THE FORECAST
PERIOD. A WEAK WAVE OF LOW PRESSURE WILL MOVE THROUGH NORTHERN
WYOMING LATE TONIGHT AND INTO WEDNESDAY MORNING...POTENTIALLY
GENERATING SOME WEAK SHOWER ACTIVITY. MOST ACTIVITY WILL BE
CONFINED TO THE HIGHER ELEVATIONS.

SOME GUSTY WIND WILL BE FOUND ACROSS THE CORRIDOR BETWEEN KRKS AND
KCPR THIS AFTERNOON. ALSO SPEAKING OF WIND...STRONGER MOUNTAIN
RELATED WIND IS EXPECTED OVERNIGHT NEAR THE TERMINALS OF KCOD AND
KLND. WHILE THE STRONGEST SURFACE WIND IS NOT ANTICIPATED TO
IMPACT EITHER OF THESE TERMINALS...SOME LLWS WILL BE POSSIBLE
BETWEEN 06Z AND 15Z WEDNESDAY.

&&

.FIRE WEATHER...


ENHANCED FIRE DANGER ACROSS EASTERN FREMONT COUNTY AND MOST OF
NATRONA COUNTY...AS BREEZY WEST WINDS COMBINE WITH WARMER AND
DRIER CONDITIONS...WITH MINIMUM RH VALUES BOTTOMING OUT IN THE
UPPER TEENS. ELSEWHERE...FIRE DANGER WILL REMAIN RELATIVELY LOW TODAY
AS COOL TEMPERATURES COMBINE WITH MINIMUM RH VALUES RANGING MOSTLY
ABOVE 20 PERCENT. WEDNESDAY WILL SEE A SIMILAR SET-UP BUT WITH
WINDS INCREASING EVEN MORE...KEEPING FIRE DANGER ELEVATED ACROSS
THOSE SAME AREAS. PLEASE SEE THE FIRE WEATHER PLANNING FORECAST FOR
MORE DETAIL.


&&

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

$$

SHORT TERM...BRAUN
LONG TERM...SKRBAC
AVIATION...BRANHAM
FIRE WEATHER...BRAUN





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