Area Forecast Discussion
Issued by NWS Riverton, WY

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FXUS65 KRIW 300536
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1136 PM MDT MON SEP 29 2014

.SHORT TERM...MONDAY NIGHT THROUGH TUESDAY

AS OF 2 PM THUNDERSTORMS ARE BEGINNING TO FIRE ACROSS PORTIONS OF
THE COUNTY WARNING AREA. DUE TO COOL TEMPERATURES AND CLOUD COVER
AROUND MUCH OF THE MORNING NO SEVERE STORMS ARE ANTICIPATED. IN
ADDITION...NOT AS MUCH RAIN IS EXPECTED AS WELL WITH PRECIPITABLE
WATER LEVELS MUCH LOWER THAN YESTERDAY. HOWEVER...WITH THE COOL
TEMPERATURES AND LOW WET BULB ZERO TEMPERATURES THERE COULD BE SOME
SMALL HAIL WITH ANY THUNDERSTORM. AND OF COURSE GUSTY WINDS...PUT
THAT PRETTY MUCH DESCRIBES ANY THUNDERSTORM IN WYOMING. THESE WILL
BE AROUND INTO THE EARLY EVENING UNTIL THE LOSS OF DAYTIME HEATING
STABILIZES THE ATMOSPHERE AGAIN. AND ONCE AGAIN...THERE WILL BE SOME
FOG AROUND ALTHOUGH NOT AS WIDESPREAD AS LAST NIGHT. A MORE
INTERESTING THING WILL HAPPEN FURTHER EAST HOWEVER.

LEE CYCLOGENESIS WILL TAKE PLACE TO THE EAST OF WYOMING LATE TONIGHT
AND INTO TUESDAY. THIS WILL LEAD TO TWO THINGS. THE FIRST WILL BE
FOR THE DEVELOPMENT OF SOME SOAKING RAIN AS MOISTURE WRAPS AROUND
THE LOW. ALL THE MODELS ARE IN GOOD AGREEMENT THAT THE HEAVIEST RAIN
SHOULD REMAIN TO THE EAST OF THE AREA. HOWEVER...IT IS CLOSE ENOUGH
THAT WE HAVE ADDED SOME UPPED POPS AND QPF JUST A BIT IN EASTERN
PORTIONS OF JOHNSON AND NATRONA COUNTIES. THE OTHER EFFECT WILL BE
TO TIGHTEN THE PRESSURE GRADIENT ACROSS MUCH OF THE AREA. THIS WILL
LEAD TO A GUSTY BREEZE FOR MANY AREAS. AT THIS TIME...700 MILLIBAR
WINDS ARE NOT ENOUGH TO SUPPORT HIGH WIND HIGHLIGHTS...BUT IT WILL
BE BLUSTERY IN FAVORED AREAS LIKE ROCK SPRINGS...CASPER AND BUFFALO.
MEANWHILE...OUT WEST ANOTHER SYSTEM WILL MOVE INTO THE WESTERN
MOUNTAINS AND BRING ANOTHER ROUND OF RAIN AND HIGHER ELEVATION SNOW
SHOWERS. WITH 700 MILLIBAR TEMPERATURES REMAINING AROUND 0 CELSIUS
SNOW LEVELS SHOULD REMAIN ABOVE 8500 FEET THROUGH TUESDAY AFTERNOON.
MEANWHILE...IN BETWEEN THESE SYSTEMS WITH CYCLONIC CURVATURE AND
WEAK INSTABILITY REMAINING WE HAVE MAINTAINED THE FORECAST OF MAINLY
ISOLATED AFTERNOON SHOWERS AND STORMS.

.LONG TERM...TUESDAY NIGHT THROUGH MONDAY

SHORTWAVE NEARING THE B.C. COAST WILL BE OUR NEXT WEATHER SYSTEM
THAT AFFECTS US TUESDAY NIGHT AND WEDNESDAY AS IT DIGS SE ACROSS THE
AREA. MODERATE TROUGH DYNAMICS WILL BEGIN IMPACTING NW WYO TUESDAY
EVENING GRADUALLY SLIDING SOUTH INTO CENTRAL WYO WEDNESDAY MORNING.
COULD SEE A DECENT QUARTER TO HALF INCH OF PCPN IN THE NW MOUNTAINS
WITH 2 TO 4 INCHES OF SNOW ABOVE 9K...MAYBE AN INCH OR TWO DOWN TO
AS LOW AS 7-8K AND A BRIEF CHANGEOVER DOWN TO AS LOW AS 6K IN THE
CODY FOOTHILLS EARLY WEDNESDAY MORNING. OTHERWISE...THE CODY
FOOTHILLS SHOULD SEE A TENTH OR TWO OF LIQUID WITH LOCALLY HIGHER
AMOUNTS. THE BIGHORNS SHOULD ALSO RECEIVE A TENTH TO QUARTER OF AN
INCH OF LIQUID TUESDAY NIGHT WITH SOME SIMILAR SNOW LEVELS AND A
COUPLE INCHES AT PASS LEVEL. ADDITIONAL LIGHT MOUNTAIN SNOW AND
FOOTHILL RAIN WILL CONTINUE INTO WEDNESDAY. MODELS ARE WEAKENING THE
CIRCULATION SOME AS IT MOVES INTO CENTRAL WYO WEDNESDAY SO TOUGH
CALL ON MEASURABLE PCPN IN THE LOWEST ELEVATIONS. SHOULD DEFINITELY
SEE SOME LIGHT PCPN IN THE FOOTHILLS AND MOUNTAINS WITH LIGHT HIGHER
ELEVATION SNOW BUT CONFIDENCE NOT THAT HIGH ON MEASURABLE PCPN IN
THE HEART OF SAY THE WIND RIVER BASIN. SRN SWEETWATER COUNTY HAS A
DECENT SHOT OF RAIN ON WEDNESDAY THOUGH. NEXT APPROACHING SHORTWAVE
FOR THURSDAY WHICH IS CURRENTLY OVER ALASKA LOOKS TO BE A GLANCING
BLOW WITH JUST A COLD FRONT IMPACTING THE FAR NRN/ERN ZONES THURSDAY
WITH GUSTY NORTH WINDS AND CLOUDS. SMALL CHANCE OF A PASSING MAINLY
MTN SPRINKLE/FLURRY IN THE BIGHORNS THURSDAY SO LEFT IN THE SLIGHT
CHANCES. NEW ECMWF IS MORE BULLISH SO WE`LL HAVE TO WATCH THIS
CLOSELY. COULD ALSO SEE SOME GUSTY WINDS IN THE CODY FOOTHILLS
WEDNESDAY NIGHT INTO THURSDAY MORNING AHEAD OF THIS SYSTEM. AFTER
THAT...RIDGE BUILDS INTO THE WEST WITH OUR AREA ON THE FRINGES OF
SEWD PASSING SHORTWAVES. NRN MOUNTAINS ESPECIALLY COULD SEE A FEW
SHOWERS FROM ONE OR TWO OF THESE BUT CURRENT MODEL TRENDS KEEP MOST
OF THE ENERGY WELL NORTH...ESPECIALLY SUNDAY INTO MONDAY.

&&

.AVIATION.../06Z ISSUANCE/

EAST OF THE DIVIDE...KCOD/KCPR/KLND/KRIW/KWRL ROUTES

THROUGH 18Z...THE MAIN CONCERN WILL BE PATCHY FOG...MAINLY OVER THE
NORTHERN BIGHORN BASIN...AND AN OUTSIDE CHANCE FOR SOME STRATUS OVER
JOHNSON. OTHERWISE CONSIDERABLE HIGH LEVEL CLOUDINESS OVER THE
EXTREME EAST. THIS SHOULD CHANGE QUICKLY TUESDAY AFTERNOON WITH
INCREASING MID LEVEL CLOUDINESS AND ISOLATED TO LOCALLY SCATTERED
CONVECTION DEVELOPING. INSTABILITY IS ON THE WEAK SIDE...SO KEPT
VCTS OUT OF MOST TAF SITES. THE ASSOCIATED COLD FRONT WILL PUSH
SOUTH ACROSS THE AREA TONIGHT. IN WAKE OF THIS FRONT...EXPECT MVFR
CEILINGS TO DEVELOP...WITH A DECENT CHANCE OF PRECIPITATION
ESPECIALLY OVER THE NORTH TONIGHT. IT IS A CLOSE CALL IF THE FRONT
AND/OR LOW CLOUDS WILL REACH KCPR...KRIW...KLND BY 12Z WEDNESDAY.

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

LOW CLOUDS WITH CEILINGS BETWEEN 020-050 KFT AGL WILL BE COMMON THIS
MORNING WITH INCREASING CHANCES OF SHOWERS THIS MORNING. THERE COULD
ALSO BE SOME FOG OR IFR CEILINGS EARLY THIS MORNING...BEFORE THE
SHOWER ACTIVITY DEVELOPS IN EARNEST HELPING TO DISSIPATE THE FOG.
WIDESPREAD VALLEY RAIN/MOUNTAIN SNOW SHOWERS ARE EXPECTED TO DEVELOP
AROUND 15Z...ESPECIALLY OVER THE FAR WEST AND LAST THROUGH MID
AFTERNOON. INSTABILITY IS VERY WEAK...AND WILL ONLY HAVE VCTS AT
KJAC WHERE THERE IS A BIT MORE LIFT. MUCH OF THIS ACTIVITY WILL EXIT
THE AREA BETWEEN 22Z AND 01Z...BUT ANOTHER SURGE OF MOISTURE COULD
BRING SHOWER ACTIVITY BACK IN THE AREA AFTER 06Z. MOUNTAINS WILL BE
OBSCURED MUCH OF THE TIME.

&&

.FIRE WEATHER...

WETTING RAIN LIKELY ACROSS WESTERN AND CENTRAL WYOMING THROUGH THIS
EVENING...THOUGH NOT AS MUCH AS THERE WAS THIS WEEKEND. SHOWERS AND
STORMS BECOME MORE ISOLATED TO SCATTERED ON TUESDAY BUT IT WILL
REMAIN COOL AND MOSTLY CLOUDY. ANOTHER REINFORCING SHOT OF COLD AIR
POSSIBLE ON WEDNESDAY WITH MORE WETTING RAIN AND MOUNTAIN SNOW
POSSIBLE. DRIER AND WARMER WEATHER MAY RETURN FOR THURSDAY AND INTO
THE WEEKEND.

&&

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

&&

$$

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








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