FXUS65 KRIW 122013
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
213 PM MDT MON MAY 12 2008

.SHORT TERM...TONIGHT THROUGH THURSDAY
SATELLITE SHOWS TROUGH CONTINUING TO DIG INTO THE GREAT BASIN AS
COLD ADVECTION AND 140KT JET MAX AID ITS SWD MOVEMENT. CURRENT
FORECAST PROBLEM WITH BE INTENSITY AND DURATION OF THE UPSLOPE
FROM LND TO CPR THIS EVENING. THE NAM12 HAS BACKED AWAY FROM ANY
SIGNIFICANT FORCING AND QPF THIS EVENING WHILE THE GFS STILL HAS A
3-6 HOUR PERIOD OF STEADY .25 INCH PCPN CONTOURS ACROSS MOST OF
THIS AREA. THE MAIN DIFFERENCE IS THE POSITION OF THE RIGHT
ENTRANCE REGION JET STREAK DYNAMICS THIS EVENING...ESPECIALLY FOR
THE CPR AREA WHERE THE GFS IS FURTHER NORTH AFFECTING CPR. MAY
NEED A SNOW ADVISORY FOR CPR MTN AT LEAST. CPR WILL INITIALLY BE
RAIN OR RAIN AND SNOW MIXTURE WHICH MAY HELP IN LOWER OVERALL SNOW
TOTALS. WILL CONTINUE IDEA OF AN INCH OR TWO AROUND LANDER WITH
BRIEF UPSLOPE AS LOW QUICKLY DROPS SOUTH. SOME LIGHT SNOW SHOWERS
MAY LINGER INTO THE MORNING IN THE S HALF BUT THEN WE GET A BRIEF
BREAK BEFORE THE NEXT SYSTEM SNEAKS DOWN FROM THE NORTH. THIS
SYSTEM IS CURRENTLY IN THE GULF OF ALASKA AND WILL RIDE OVER THE
TOP OF THE RIDGE AND THEN SWD INTO WYOMING. SEVERAL SHORTWAVES
ACTUALLY COME DOWN IN THIS NLY FLOW WEDNESDAY INTO THURSDAY. HAVE
CONTINUED TREND OF HIGHER POPS IN THE NRN MTNS AND EAST OF THE DIVIDE.
TEMPERATURES WILL CONTINUE BELOW NORMAL THROUGH THE PERIOD WITH
SOME MODERATION TUESDAY INTO WEDNESDAY.

.LONG TERM...THURSDAY NIGHT THROUGH MONDAY
MEDIUM RANGE MODELS SHOW ANOTHER WEAK DISTURBANCE IN THE
NORTHERLY FLOW AFFECTING THE AREA THURSDAY NIGHT...AND HAVE
INCREASED POPS A BIT...EAST OF THE DIVIDE FOR THIS SYSTEM. FRIDAY
THROUGH SUNDAY...THE STRONG RIDGE ACROSS THE WEST COAST IS
EXPECTED TO MOVE SLIGHTLY EASTWARD AND HAVE MORE OF AN INFLUENCE
ON THE WEATHER ACROSS THE FORECAST AREA. THIS WILL RESULT IN
WARMER AND DRIER CONDITIONS OVER THE AREA. ENOUGH
INSTABILITY...AND SUFFICIENT MEAN MOISTURE WILL BE PRESENT TO
INCLUDE THE POSSIBILITY OF A FEW MOUNTAIN SHOWERS IN THE AFTERNOON
AND EVENING...FRIDAY THROUGH SUNDAY. SATURDAY APPEARS TO BE THE
DRIEST DAY WITH LEAST AMOUNT OF MOISTURE AVAILABLE. THIS STRONG
RIDGE IS EXPECTED TO FLATTEN OUT...BY SUNDAY NIGHT/MONDAY...WITH A
MORE PROGRESSIVE PATTERN REDEVELOPING. THE 00Z ECMWF IS SLIGHTLY
SLOWER IN BREAKING DOWN THIS RIDGE. THIS WARM UP THIS
WEEKEND...HAS THE POTENTIAL TO CAUSE SOME RAPID SNOWMELT OVER THE
MOUNTAINS WHICH COULD CREATE SOME HYDROLOGICAL ISSUES...ESPECIALLY
ON SMALLER STREAMS AND CREEKS.

&&

.AVIATION...
AN AREA OF LOW PRESSURE WILL KEEP SNOW AND RAIN SHOWERS PRESENT
ACROSS MUCH OF CENTRAL AND WESTERN WYOMING THROUGH THIS EVENING.
UPSLOPE CONDITIONS WILL CAUSE RAIN TO CONVERT TO SNOWFALL OVER THE
WIND RIVER BASIN AFTER 03Z THIS EVENING. SNOW SHOWERS AND THEIR
ASSOCIATED MVFR TO IFR CONDITIONS WILL THEN BE LIKELY THROUGH 06Z
FOR KLND...KRIW...KRKS...AND KCPR BEFORE BEGINNING TO TAPER OFF.
SNOW AND RAIN SHOWERS CONTINUE TO TAPER OFF THROUGH TUESDAY
AFTERNOON ACROSS THE REMAINDER OF CENTRAL AND EASTERN WYOMING...WITH
GENERALLY DRY CONDITIONS AND WIDESPREAD VFR CONDITIONS EXPECTED
AFTER 18Z TUESDAY.

&&

.FIRE WEATHER...
CURRENT COLD SYSTEM WILL BRING ISOLATED EVENING THUNDERSTORMS TO
THE WEST CENTRAL AND SW PORTIONS OF THE AREA WITH CONSIDERABLE
SHOWERS OF RAIN AND SNOW IN MOST AREAS. THIS SYSTEM WILL GRADUALLY
MOVE SOUTH OF THE AREA ON TUESDAY WITH TEMPERATURES WARMING AROUND
10 DEGREES BUT STILL CONSIDERABLY BELOW NORMAL. MIN RH'S WILL VARY
FROM THE UPPER 20S TO UPPER 30S WITH MAINLY 40S IN THE HIGH COUNTRY.
ANOTHER SYSTEM WILL COME DOWN FROM THE NORTH ON WEDNESDAY BRINGING
WITH IT ANOTHER CHANCE OF SHOWERS THAT WILL LINGER INTO THURSDAY...
ESPECIALLY EAST OF THE DIVIDE. TEMPERATURES WILL CONTINUE BELOW
NORMAL AND MIN RH'S WILL RISE SOME WEDNESDAY AND THURSDAY WITH 35
TO 45 PERCENT ACROSS THE LOWER ELEVATIONS WITH 40S AND 50S IN THE
HIGH COUNTRY. WINDS WILL SHIFT AROUND WITH EACH SYSTEM WITH
GENERALLY NORTH TO NORTHEAST WINDS TONIGHT AND THEN SHIFTING TO
THE SOUTHWEST BY LATER TUESDAY NIGHT AND BACK TO THE NORTH ON WEDNESDAY.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...SNOW ADVISORY FROM 3 PM THIS
AFTERNOON TO 6 AM TUESDAY FOR WYZ022.

&&

$$

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