Area Forecast Discussion
Issued by NWS Riverton, WY

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FXUS65 KRIW 270534
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1134 PM MDT TUE AUG 26 2014

.SHORT TERM...TONIGHT THROUGH WEDNESDAY (ISSUED AT 201 PM MDT)

A 700-300MB VERTICALLY STACKED LOW OVER NORTHERN NEVADA WILL DRIFT
TO THE UTAH/NEVADA LINE BY 06Z WED TONIGHT AND THEN TO CENTRAL UTAH
BY WED. THE H7 CIRCULATION WILL SPLIT WITH ONE CIRCULATION OVER
SWEETWATER COUNTY WEDNESDAY WITH A WEAKER NORTHERN CIRCULATION OVER
NORTHWEST WY. THE SOUTHERN CIRCULATION OVER SWEETWATER COUNTY SHOULD
BE THE MAIN FOCUS AS IT WILL REMAIN SOMEWHAT VERTICALLY STACKED
UNDERNEATH THE UPPER CIRCULATION. Q VECTOR FORCING WILL FOLLOW THE
PATH OF THIS CIRCULATION RESULTING IN A WIDESPREAD AREA OF SHOWERS
OR OCCASIONAL LIGHT TO MODERATE RAINFALL MAINLY OVER SWEETWATER AND
SOUTHERN NATRONA COUNTIES TONIGHT THROUGH WEDNESDAY MORNING WHERE
BETWEEN ONE QUARTER TO ONE HALF OF AN INCH OF RAINFALL COULD OCCUR
IN MANY AREAS. THE LOWEST LIFTED INDICES/HIGHEST CAPES WILL BE IN
THIS SAME GENERAL AREA AFTER 18Z WEDNESDAY WHERE THE BEST CHANCE OF
THUNDERSTORMS WILL BE ALONG WITH LESS THAN A CHANCE TO THE NORTH AND
WEST OF THIS AREA. NORTHWEST WY WILL BE MAINLY DRY WED. TEMPERATURES
SHOULD BE A AROUND 5 DEGREES OR SO WARMER WED THAN TODAY.

.LONG TERM...WEDNESDAY NIGHT THROUGH TUESDAY

UPPER LOW IS EXPECTED TO BE PASSING JUST TO OUR SOUTH TO START THIS
PERIOD WITH LINGERING RAIN/SHOWERS OVER OUR SERN SECTIONS. BEST
CHANCE WILL BE SERN SWEETWATER AND MAYBE CASPER MTN.
OTHERWISE...GRADUAL CLEARING FROM NW TO SE WEDNESDAY NIGHT. BRIEF
SHORTWAVE RIDGING THURSDAY FOR A DRY AND WARMER DAY. NEXT SYSTEM IS
HANDLED DIFFERENTLY BETWEEN THE FURTHER SOUTH NAM AND FURTHER NORTH
GFS. ALTHOUGH EVEN THE GFS HAS ENOUGH DAYTIME HEATING/MID LEVEL
COOLING AND A VERY WEAK FRONTAL BOUNDARY SAGGING SOUTH TO WARRANT AT
LEAST ISOLATED STORMS OVER AND NEAR THE MOUNTAINS. THE NAM WITH ITS
FURTHER SOUTH TRAJECTORY OF THIS WAVE HAS A BETTER SURFACE FRONT
SAGGING SOUTH THURSDAY NIGHT AND FRIDAY MORNING THAT BECOMES A
POTENTIAL FOCUS FOR THUNDERSTORMS IN THE N AND E FRIDAY AFTERNOON.
BETTER LOW LEVEL MOISTURE AND THUS MORE AVAILABLE CAPE IS ALSO
FORECAST BY THE NAM. CURRENT FORECAST ALREADY HAS ISOLATED STORMS IN
MOST OF THE NORTH AND EAST AND THIS SEEMS GOOD WITH NO CHANGES
NEEDED. JUST DAYTIME HEATING AND LIMITED MOISTURE WILL LIKELY FIRE
ISOLATED MTN STORMS AND IF WE CAN GET THE FRONTAL BOUNDARY TO SAG
SWD INTO THE AREA AND HANG AROUND WE COULD SEE A FEW STORMS ACROSS
THE LOWER ELEVATIONS OF THE NORTH...ONE OR TWO OF WHICH COULD BE
RATHER STRONG. DRY AND BREEZY IN THE SOUTH. MAIN PCPN WILL REMAIN
ACROSS THE NORTH WITH THIS SYSTEM WITH SMALLER CHANCES FURTHER SOUTH.

LABOR DAY WEEKEND WILL SEE A SERIES OF SYSTEMS AND FRONTS IMPACT THE
AREA IN VARIOUS WAYS. THE NRN MOUNTAINS WILL SEE THE HIGHEST IMPACT
AND BEST CHANCE OF PCPN WITH SOME LIGHT HIGHER ELEVATION SNOW SUNDAY
MORNING AND MONDAY NIGHT PER THE GFS. THOSE ARE THE BEST CHANCES
BASED ON CURRENT GFS TIMING WITH SNOW LEVELS RISING TO THE HIGHEST
PEAKS IN BETWEEN THIS TWO MAIN SYSTEMS. ECMWF IS FASTER WITH THE
SECOND SYSTEM. WILL LEAN ON THE GFS OVERALL WITH SOME NUDGE
TOWARDS THE ECMWF. FOR YELLOWSTONE NATIONAL PARK...THE FIRST FRONT
APPROACHES LATE IN THE DAY SATURDAY WITH A THUNDERSTORMS EXPECTED
ALONG THE FRONT WITH FALLING TEMPERATURES INTO THE EVENING. AHEAD
OF IT...IT WILL BE A WARM TO VERY WARM DAY AND WINDY WITH
INCREASING FIRE CONCERNS. THE SERN HALF LOOKS LIKE RH`S WILL BE
WELL DOWN INTO THE TEENS WITH SW WINDS 25-40 MPH. RECENT MOISTURE
HAS CERTAINLY MOISTENED UP THE FUELS BUT IF THE AREAS REMAIN WITH
CRITICAL FUELS...FIRE WEATHER WATCHES MAY EVENTUALLY BE NEEDED
DEPENDING ON HOW THE RH LOOKS. OTHERWISE...THE MAIN WEATHER AHEAD
OF THE SATURDAY NIGHT FRONT WILL BE THE WARM AND WINDY CONDITIONS.
MUCH COOLER TO DOWNRIGHT COLDER SUNDAY WITH SOME WIND CONTINUING.
STILL A GOOD CHANCE OF SHOWERS UP NORTH WITH HIGHER MOUNTAIN SNOW
ABOVE 9-10K. SNOW LEVEL COULD BE EVEN LOWER FOR A WHILE SUNDAY
MORNING. CONTINUED WINDY ON LABOR DAY WITH LOW RH`S IN THE SOUTH
HALF WITH SHOWERS AND A FEW THUNDERSTORMS RETURNING TO YNP BY LATE
IN THE AFTERNOON OR EVENING WITH SNOW LEVELS LOWERING ONCE
AGAIN...MAYBE AS LOW AS 8-9K MONDAY NIGHT. COOLER AGAIN TUESDAY
WITH PCPN LINGERING IN THE BIGHORNS MAINLY OTHERWISE...DRY.
OTHERWISE...ANOTHER UNSEASONABLY COOL AGAIN WITH SOME WIND IN THE
SOUTH WHICH WILL HAVE THE QUOTE WARMEST CONDITIONS.

&&

.AVIATION.../06Z ISSUANCE/

SHOWERS WILL INCREASE IN COVERAGE OVER SOUTHERN WY BY 14Z. THEN THE
SHOWERS AND ISOLATED STORMS WILL OCCUR OVER THE SOUTHERN PORTION OF
THE REGION IMPACTING TERMINAL SITES FROM KBPI TO KCPR. SEE TERMINAL
FORECASTS FOR MORE DETAILS. AREAS OF MVFR CONDITIONS WILL OCCUR IN
THE SOUTH ALONG WITH MOUNTAIN OBSCURATION. CONDITIONS WILL IMPROVE
AFTER 03Z ACROSS THE SOUTH AS SHOWERS DECREASE AND CEILINGS RISE.

OVER THE NORTH VFR CONDITIONS WILL PREVAIL WITH ISOLATED SHOWERS AND
STORMS FROM 19Z UNTIL 02Z...MAINLY OVER AND NEAR THE MOUNTAINS.

&&

.FIRE WEATHER...

AN AREA OF LOW PRESSURE WILL KEEP SHOWERS AND THUNDERSTORMS AROUND
THROUGH THIS EVENING...ESPECIALLY ACROSS SOUTHWESTERN WYOMING. AS
THE SYSTEM MOVES EASTWARD OVER THE NEXT COUPLE DAYS...EXPECT
CONTINUED SHOWER ACTIVITY WITH SOME HEAVY RAIN POSSIBLE WEDNESDAY
AND INTO THURSDAY...ESPECIALLY OVER SOUTHERN WYOMING. DAYTIME HUMIDITY
WILL REMAIN ELEVATED WITH THIS SYSTEM...AND COOLER TEMPERATURES
ARE ALSO ANTICIPATED. FIRE WEATHER CONCERNS REMAIN FAIRLY MINIMAL
THROUGH FRIDAY AT THIS TIME. HOWEVER...SWEETWATER...FREMONT AND
NATRONA COUNTIES WILL LIKELY EXPERIENCE WINDIER...DRIER AND WARMER
CONDITIONS SATURDAY.

&&

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

&&

$$

SHORT TERM...LIPSON
LONG TERM...SKRBAC
AVIATION...AR
FIRE WEATHER...LIPSON











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