Area Forecast Discussion
Issued by NWS Riverton, WY

Home | Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

000
FXUS65 KRIW 300845
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
245 AM MDT TUE SEP 30 2014

.SHORT TERM...TODAY THROUGH THURSDAY NIGHT

PREVIOUS FORECAST LOOKS TO BE ON TRACK...MOST OF THE ACTIVITY WILL
BE EAST OF THE AREA TODAY AS WE TRANSITION TO MOIST WESTERLY FLOW.
RAPID LEE CYCLOGENESIS IS ALREADY BEGINNING NEAR THE NE/WY/SD TRIPLE
POINT...WHICH WILL TRANSLATE TO A NOTICEABLE INCREASE IN WESTERLY
WINDS ACROSS THE FORECAST AREA... ESPECIALLY ACROSS THE SOUTH EARLY.
THE LOW WILL MOVE NORTH AND EAST DURING THE MORNING...SWITCHING
WINDS TO THE NORTHWEST ACROSS OUR NORTHERN HALF OF THE FORECAST
AREA...AND ENCOURAGING A COLD FRONT TO DIP SOUTH...WHICH COULD LEAD
TO GUSTS OVER 40 MPH WINDS IN NORTHERN JOHNSON COUNTY IF EVERYTHING
LINES UP RIGHT. ASIDE FROM THE WIND...OROGRAPHIC LIFT ACROSS THE
WEST...A COLD FRONT DIPPING INTO THE NORTH...AND A DEFORMATION AXIS
POKING INTO OUR EASTERN ZONES COULD KEEP SOME MORE PERSISTENT RAIN
GOING IN THESE AREAS...WITH SNOW ABOVE 8500FT IN THE WESTERN
MOUNTAINS AND YELLOWSTONE. IT WILL BE VERY WEAKLY UNSTABLE
ELSEWHERE...AND THAT COMBINED WITH DECENT RESIDUAL MOISTURE COULD
ALLOW FOR SOME ISOLATED AFTERNOON SHOWERS IN BETWEEN. IT WILL
DEFINITELY STILL BE A COOL...MOIST AND RAW DAY FOR MUCH OF THE AREA.

INTO WEDNESDAY...A REENFORCING SHOT COULD ARRIVE IN THE WESTERLY
FLOW...WITH YET ANOTHER WEATHER SYSTEM FOR WEDNESDAY KEEPING SHOWERS
IN THE FORECAST AND DIPPING SNOW LEVELS DOWN BELOW 7000FT ACROSS THE
WEST AND NORTH. THESE NEXT COUPLE OF SYSTEMS ARE NOT EXPECTED TO
AMOUNT TO MUCH PRECIPITATION BUT THEY HAVE A BETTER SHOT AT LAYING
DOWN A WETTING RAIN AND A MOUNTAIN SNOW ACROSS THE NORTH...BASICALLY
THE ONLY AREA IN OUR CWA THAT DID NOT GET MUCH OUT OF THE WEEKEND
STORM. 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. OUR LAST WAVE SHOULD
EXIT WEDNESDAY EVENING LEAVING BEHIND A VERY COOL AND FROSTY NIGHT
FOR MUCH OF THE FORECAST AREA.

THE NEXT APPROACHING SHORTWAVE FOR THURSDAY LOOKS TO BE A GLANCING
BLOW WITH JUST A SLIGHT CHANCE OF RAIN IN THE FAR NRN/ERN ZONES
THURSDAY WITH GUSTY NORTH WINDS AND CLOUDS. COULD ALSO SEE SOME
GUSTY WINDS IN THE CODY FOOTHILLS WEDNESDAY NIGHT INTO THURSDAY
MORNING AHEAD OF THIS SYSTEM. ELSEWHERE...IT WILL BE MAINLY DRY AND
REMAINING COOL WITH SWIFT NORTHWEST FLOW ALOFT TRANSLATING TO A FEW
20 TO 35 MPH BREEZES DEVELOPING ACROSS THE SOUTH.

.LONG TERM...FRIDAY THROUGH TUESDAY

THE LONG RANGE MODELS ARE IN GOOD AGREEMENT THROUGH SUNDAY WITH THE
WEATHER PATTERN. ON MONDAY AND TUESDAY THE GFS AND GEM MODELS TRY TO
SAG A COLD FRONT ALONG THE MONTANA/WY BORDER WITH PRECIP GETTING
CLOSE MONDAY NIGHT AND TUESDAY ALONG THE BORDER. THE ECMWF IS
DIFFERENT EARLY NEXT WEEK AND KEEPS THE COOLER AIR IN SOUTHERN
CANADA/NORTHERN MONTANA AND DRY WEATHER ALONG THE NORTHERN WY
BORDER. FOR NOW WILL COMPROMISE AND KEEP THE FORECAST DRY AND KNOCK
A DEGREE OR TWO OFF THE HIGH TEMPS IN THE FAR NORTH MONDAY AND
TUESDAY. THERE WILL BE PERIODS OF MID AND HIGH CLOUDS MOVING THROUGH
THE AREA FRIDAY THROUGH TUESDAY WITH LIMITED AMOUNTS OF CUMULUS
CLOUDS. HIGH TEMPS WILL BE SEASONAL TO SLIGHTLY ABOVE NORMAL FRIDAY
THROUGH NEXT TUESDAY. EXPECT BREEZY AREAS IN THE AFTERNOON THROUGH
SUNSET OVER THE WEEKEND INTO EARLY NEXT WEEK. BOTTOM LINE...GOOD
FALL WEATHER FOR SEEING FALL FOLIAGE OR OTHER OUTDOOR ACTIVITIES.

&

.AVIATION.../12Z 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...FROM A SYSTEM IN THE PLAINS. THIS SHOULD CHANGE
QUICKLY THIS 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. A 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.

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 POSSIBLE ACROSS WESTERN AND CENTRAL WYOMING AGAIN
TODAY...THOUGH NOT AS MUCH AS THERE WAS THIS WEEKEND. SHOWERS WILL
BE MORE SCATTERED TODAY ACROSS THE NORTH...WEST AND EAST WITH
ISOLATED SHOWERS AND A THUNDERSTORM OR TWO ACROSS THE SOUTH. IT WILL
REMAIN COOL AND CLOUDY THROUGH THURSDAY AS A SERIES OF DISTURBANCES
AND COLD FRONTS MOVE THROUGH THE REGION. IT WILL BE WARMER AND DRIER
ON FRIDAY WITH SWIFT WEST TO NORTHWEST FLOW CONTINUING.

&&

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

&&

$$

SHORT TERM...ALLEN
LONG TERM...AR
AVIATION...WM
FIRE WEATHER...ALLEN






USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.