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000
FXUS65 KRIW 052316
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
416 PM MST WED MAR 5 2014

.SHORT TERM...TONIGHT THROUGH FRIDAY
AS THE FLAT RIDGE THAT GAVE US A BRIEF VISIT TODAY SLIDES OFF TO
THE EAST...THE GRADIENT WILL TIGHTEN...BACK AND BECOME MORE
DIFLUENT AS WE GET A MORE DIRECT FEED OF THE PACIFIC. THIS WILL
RESULT IN THICKENING CLOUDS OUT WEST ALONG WITH SNOWFALL BREAKING
OUT AROUND MID EVENING IN THE FAR WEST. PRECIPITATION WILL LIKELY
BEGIN AS A MIXTURE OF RAIN AND SNOW IN THE VALLEYS THIS EVENING.
AFTER MIDNIGHT THE PRECIP WILL BE ALL SNOW AND WILL BECOME
STEADIER AS ISENTROPIC LIFT GETS UNDERWAY IN THE WEST. THE STEADY
SNOWFALL WILL CONTINUE THROUGH THE MORNING HOURS THURSDAY...THEN
BECOMING MORE INTERMITTENT BY THURSDAY AFTERNOON AS THE AIR MASS
BECOMES MORE UNSTABLE. THERE COULD EVEN BE AN ISOLATED LIGHTNING
STRIKE OUT WEST NOT TO UNLIKE WHICH OCCURRED TUESDAY EVENING. THE
SNOW WILL MIX WITH OR CHANGE TO RAIN IN THE FAR WEST VALLEYS
THURSDAY AFTERNOON AS H7 TEMPS RISE TO BETWEEN -2C AND
ZERO...WHICH...BY THE WAY IS COOLER THAN THE 2 TO 3C TEMPS EARLIER
MODEL RUNS WERE FORECASTING. THE FIRST SHORTWAVE TROUGH WITHIN THE
MAIN TROUGH WILL COME THROUGH THURSDAY AND WILL BE MARKED BY THE DISTINCTIVE
BAND OF PRECIP THAT WILL SLIDE NORTH TO SOUTH...MAINLY AFFECTING
AREAS WEST OF THE DIVIDE THURSDAY MORNING BEFORE PRECIPITATING ON
SWEETWATER COUNTY BY MID DAY THURSDAY. SNOW WILL CONTINUE IN THE
FAR WEST THURSDAY NIGHT AND INTO FRIDAY. ON FRIDAY...THE SECOND
PIECE OF ENERGY WILL COME THROUGH AS THE SECOND SHORTWAVE TROUGH
MOVES THROUGH AND SHIFTS THE WINDS AROUND AT THE BOUNDARY LEVEL
12Z FRIDAY DURING THE MAIN FROPA. EXPECT COOLER TEMPS FRIDAY ON
THE BACK SIDE OF THE MAIN TROUGH SO EXPECT MAINLY ALL SNOW FOR
FRIDAY OUT WEST. CANT RULE OUT THE POSSIBILITY OF AN ISOLATED
LIGHTNING STRIKE ONCE AGAIN FRIDAY AFTERNOON MAINLY IN THE WEST. BY
LATE FRIDAY...EXPECT UP TO 8 TO 10 INCHES IN THE WESTERN MTNS...2
TO 3 INCHES TOTAL BETWEEN MELTS IN THE WESTERN VALLEYS AND 4 TO 7
INCHES IN THE FOOTHILLS.

A FLOOD ADVISORY IS IN AFFECT FOR THE STAR VALLEY TONIGHT THROUGH
LATE THIS EVENING BECAUSE OF ABOVE FREEZING TEMPS AND A HEAVY
SNOW PACK RANGING ROUGHLY FROM 30 TO 50 INCHES IN MANY AREAS. WILL
LIKELY EXPERIENCE MINOR SMALL STREAM AND URBAN FLOODING ONCE AGAIN
THURSDAY AFTERNOON AS TEMPS ONCE AGAIN RISE ABOVE FREEZING AND
SOME RAIN FALLS OVER THE AREA.

AS FOR WIND...DECIDED TO UPGRADE THE HIGH WIND WATCH TO A WARNING
FOR THE CODY FOOTHILLS FOR TONIGHT AND THURSDAY MORNING SINCE THE
H7 WINDS WILL INCREASE TO 50 KNOTS AND THERE IS BUT A HINT OF A
MTN WAVE WITH A FROUDE NUMBER NEAR 1...ALBEIT A WEAK UPSTREAM MTN
TOP INVERSION. ONLY A 10C H7 TEMP GRADIENT BETWEEN YNP TO THE CODY
FOOTHILLS SO WENT WITH A LOW GRADE HIGH WIND WARNING THERE. ONLY 3
TO 4 DECAMETER HEIGHT LINES AT H7 SPACED OUT ACROSS WY THURSDAY
ALONG WITH ONLY A 10MB SFC PRESSURE GRADIENT BETWEEN GCC AND RKS
SO WILL ONLY ISSUE ANOTHER SPS FOR THE SOUTHERN WIND CORRIDOR FOR
TONIGHT AND THURSDAY.

EXPECT HIGHS IN THE LOW TO MID 50S THURSDAY EAST OF THE DIVIDE BUT
WILL SHY AWAY FROM UPPER 50S GIVEN THE CLOUDINESS EXPECTED WHICH
IS WHAT WE WOULD REACH IF THIS AREA COMPLETELY MIXED OUT.

SOME SPOTTY PRECIP WILL MAKE IT EAST OF THE DIVIDE FRIDAY
AFTERNOON WITH THE FROPA.

.LONG TERM...FRIDAY NIGHT THROUGH WEDNESDAY OUR THURSDAY/FRIDAY
SYSTEM WILL BE EXITING THE FORECAST AREA NORTH TO SOUTH FRIDAY
NIGHT...PUSHED ALONG BY A RIDGE DUE TO FOLD OVER THE AREA THIS
WEEKEND. 700MB TEMPERATURES WILL RISE INTO THE 99TH PERCENTILE FOR
THIS TIME OF YEAR...SO A VERY MILD WEEKEND IT WILL BE. LIMITING
FACTORS WILL BE REMAINING SNOW COVER AND HIGH CLOUDS MOVING OVER
THE RIDGE...TEMPERATURES EAST OF THE DIVIDE WERE KEPT IN THE 50S
IN THE BASINS WITH LOW TO MID 40S EXPECTED IN THE WESTERN VALLEYS.
THE LOW ELEVATION SNOW PACK IS ALREADY RIPE AND READY TO MELT SO
EXPECT CONTINUED PONDING OF WATER AND SOME MINOR FLOODING IN LOW
LYING AREAS. THIS ACTIVITY IS EXPECTED TO CONTINUE THROUGH SUNDAY
AND POSSIBLY MONDAY.

FLOW TURNS ZONAL ON MONDAY...USHERING IN OUR NEXT WEATHER SYSTEM. AN
INFLUX OF COLD AIR INTO THE WEST WILL SLOW SNOW MELT BUT THE ARRIVAL
OF THE RIGHT ENTRANCE REGION OF THE JET AND A SHORT WAVE DISTURBANCE
WILL BRING ANOTHER ROUND OF SNOW MONDAY NIGHT. THE GLOBAL MODELS
DISAGREE ON EXACTLY WHERE THE HEAVIEST SNOW WILL FALL BUT THE WEST
WILL IS THE MOST LIKELY TO RECEIVE MEASURABLE SNOW IN THE FAVORABLE
WESTERLY UPSLOPE FLOW.

RE ENFORCEMENTS ARRIVE ON TUESDAY AS ANOTHER WAVE DIGS ACROSS THE
INTER MOUNTAIN WEST...DRAGGING DOWN A SHOT OF ARCTIC AIR AND BRINGING
UPSLOPE FLOW...AND A CHANCE OF SNOW EAST OF THE DIVIDE. THERE REMAIN
SOME DISCREPANCIES IN THE GLOBAL MODELS FOR THIS SYSTEM...THE EC
REMAINS MORE BULLISH...ESPECIALLY EAST OF THE DIVIDE...WHILE THE GFS
BYPASSES THE CENTRAL BASINS WITH MORE SNOW EXPECTED ACROSS THE NORTH
AND THE SOUTH. KEPT PRECIPITATION CHANCES BROAD DUE TO THE
UNCERTAINTY.

ON THE BACK SIDE OF OUR TUESDAY SYSTEM...THERE LOOKS TO BE THE EVER
PRESENT SWD MOVING SHORTWAVE THAT MAY KEEP WEDNESDAY MORNING
UNSETTLED WITH A CHANCE OF SNOW SHOWERS ACROSS MUCH OF THE AREA.
POPS WERE KEPT IN THE CHANCE CATEGORY FOR MOST OF THE MOUNTAINS AND
SLIGHT CHANCE IN THE LOWER ELEVATIONS FOR NOW WITH SOME CLEARING
POSSIBLE WEDNESDAY EVENING.


&&

.AVIATION.../00Z ISSUANCE/
EAST OF THE DIVIDE...KCOD/KCPR/KLND/KRIW/KWRL ROUTES

DRY CONDITIONS WITH MAINLY LEE ENHANCED HIGH CLOUDINESS AND SOME
MID CLOUDS ARE EXPECTED THROUGH TONIGHT. THE BASINS AND VALLEYS
WILL SEE FAIRLY LIGHT WINDS THROUGH THE PERIOD WHILE THE
MOUNTAINS...FOOTHILLS AND WIND CORRIDOR FROM SOUTH PASS TO KCPR
WILL BE BREEZY TO WINDY. STRONG WINDS WILL DEVELOP OVER THE CODY
FOOTHILLS TONIGHT...AND CREATE SOME LLWS AT KCOD TERMINAL. COULD
ALSO SEE SOME LLWS AT KLND TONIGHT.

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

CLOUDS WILL INCREASE AND THICKEN OVER THE FIELD OF CUMULUS CLOUDS
BELOW THROUGH EARLY THIS EVENING AS YET ANOTHER STORM SYSTEM
APPROACHES THE REGION WITH SOME SNOW BREAKING OUT ACROSS NORTHWEST
WYOMING BY MID EVENING. A GOOD BET THAT KJAC WILL SEE SNOW...WITH
INCREASING CHANCES AS THE NIGHT PROGRESSES. SOUTH OF KJAC...HIGH
ELEVATIONS SNOW AND LOW ELEVATION RAIN AND SNOW TOWARD LATE
MORNING. BREEZY WESTERLY WINDS ARE EXPECTED TO DEVELOP TODAY OVER
SWEETWATER COUNTY...WITH BREEZY SOUTHERLY WIND IN JACKSON HOLE.

&&

.FIRE WEATHER...
NO FIRE WEATHER CONCERNS THROUGH THE REST OF THE WEEK. HOWEVER...AND
WARMER WEATHER IS ON THE WAY EAST OF THE DIVIDE WITH HIGH
TEMPERATURES AT THE LOWERS ELEVATIONS REACHING INTO THE 50S TO NEAR
60 ON THURSDAY AND AGAIN ON SATURDAY THROUGH POSSIBLY MONDAY...WITH
SUNDAY EXPECTED TO BE THE WARMEST DAY. OTHERWISE...WEST TO SOUTHWEST
WINDS OF 20 TO 30 MPH WITH GUSTS NEAR 50 CAN BE EXPECTED TONIGHT
THROUGH THURSDAY MORNING ACROSS THE SOUTHEASTERN DISPATCH ZONES.
STRONG WINDS WILL DEVELOP OVER THE SAME PERIOD IN THE CODY FOOT HILL
REGION. ADDITIONALLY...THE NEXT IN A SERIES OF UPPER LEVEL
DISTURBANCES COMBINING WITH PACIFIC MOISTURE WILL BEGIN TO PUSH INTO
THE WESTERN ZONES TONIGHT WITH PRECIPITATION INCREASING DRAMATICALLY
ACROSS THE WESTERN MOUNTAINS BY THURSDAY MORNING. SOME MOUNTAIN
AREAS MAY RECEIVE UP TO A FOOT OF NEW SNOW BY SUNDOWN THURSDAY.
THURSDAY NIGHT THROUGH FRIDAY...WIDESPREAD SHOWER ACTIVITY WILL BE
AVAILABLE ACROSS THE WESTERN DISPATCH ZONES...BUT WITH ONLY A FEW
INCHES OF ADDITIONAL SNOWFALL BY THE END OF THE DAY FRIDAY. WINDS
WILL ALSO DECREASE FROM THURSDAY AFTERNOON THROUGH FRIDAY.


&&

.RIW WATCHES/WARNINGS/ADVISORIES...
HIGH WIND WARNING FROM 8 PM THIS EVENING TO 11 AM MST THURSDAY
WYZ003.

&&

$$

SHORT TERM...LIPSON
LONG TERM...ALLEN
AVIATION...LIPSON
FIRE WEATHER...ALLEN