Area Forecast Discussion
Issued by NWS Riverton, WY

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
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 111038
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
338 AM MST THU FEB 11 2016

.SHORT TERM...TODAY THROUGH SATURDAY NIGHT

THE BIGGEST FORECAST CHALLENGE ONCE AGAIN IS PROVING TO BE
TEMPERATURES. THE STRONG RIDGE HAS BUILT INTO THE AREA FROM THE WEST
ENOUGH TO CREATE VERY STRONG INVERSIONS IN THE VALLEYS AND BASINS.
IN FACT MANY VALLEY HIGH TEMPS HAVE BEEN AND WILL BE LOWER THAN THE
MID SLOPE LOW TEMPS. THE TEMPERATURES WILL CONTINUE TO BE THE MOST
CHALLENGING WEATHER ELEMENT TO PIN DOWN FOR THE NEXT COUPLE OF DAYS
BECAUSE OF THIS. IN ADDITION TO THE INVERSIONS...MANY AREAS AT THE
SAME ELEVATIONS HAVE QUITE A HIGH VARIABILITY OF SNOW COVER WHICH
ALSO HAS BEEN INFLUENCING TEMPS BELOW AND ABOVE THE INVERSIONS.
FOR EXAMPLE...IN AREAS THAT ARE MIXED...CASPER HAS HAD HIGHS IN
THE LOW 50S BUT AREAS JUST TO THE WEST HAVE BEEN STRUGGLING TO
BREAK OUT OF THE 30S AT AND WEST OF THE CPR ASOS DUE TO MORE
CONTINUOUS SNOW COVER JUST WEST OF CASPER. BELOW THE INVERSION...FARSON
HAS BEEN COLDER THAN BPI FOR THE SAME REASON WITH MORE SNOW ON THE
GROUND AROUND FARSON. THE COLDEST TEMPS WILL CONTINUE TO BE ALONG
THE STAR VALLEY AS THIS IS THE MOST PROTECTED LAND FEATURE IN THE
AREA THAT IS CLOSEST TO THE SALT LAKE SFC HIGH. HIGH TEMPS ABOVE
THE INVERSIONS WILL NOT REACH 60 TODAY LIKE THEY DID WED IN A
COUPLE OF AREAS BECAUSE A COUPLE OF WEAK VORT LOBES IN THE NW FLOW
ON THE FRONT SIDE OF THE STRONG RIDGE OVER THE WESTERN UNITED
STATES WILL COOL TEMPS OFF A COUPLE OF DEGREES AT H7 BUT 50S WILL
STILL OCCUR IN MANY MIXED AREAS EAST OF THE DIVIDE ALONG WITH LOW
RH TODAY AND FRIDAY. HIGHS WILL STRUGGLE TO GET ABOVE THE 20S IN
THE STAR VALLEY TODAY AND FRIDAY. THE VORT LOBE WE WILL EXPERIENCE
TODAY AND THE NEXT ONE ON FRIDAY WILL CREATE ENHANCEMENT OF LEE
ENHANCED CLOUDINESS WHICH WILL ENSURE THAT INVERSIONS WILL HOLD.
PATCHY FOG WILL LIKELY FORM AGAIN IN THE WESTERN VALLEYS AND
BASINS LATE TONIGHT AND FRIDAY MORNING. THE NEXT SIGNIFICANT
PACIFIC TROUGH NOW OUT AT 150W OFF THE PACIFIC COAST WILL BEAR
DOWN ON THE ROCKIES FRIDAY NIGHT WITH LOWERING AND THICKENING
CLOUDS IN THE WEST. THERE IS STILL SOME QUESTION AS TO HOW
SUCCESSFUL THIS TROUGH WILL BE AT MOWING DOWN THE PERSISTENT RIDGE
INSTEAD OF TOTALLY SPLITTING BUT SINCE EACH SOUTHEAST BOUND WEAK
VORT LOBE MAY HAVE A TENDENCY TO WEAR DOWN THE RIDGE...WE WILL
ASSUME THAT THE EFFECTS OF THE TROUGH WILL HAVE THE POTENTIAL TO
PRODUCE MEASURABLE SNOWFALL ACROSS THE FAR WEST SAT/SAT NT AS THE
RIDGE AXIS RETROGRADES A LITTLE WEST. WITH 8MB 3 HOURLY SFC
PRESSURE RISES INDICATED FOR THE WIND RIVER BASIN SATURDAY NIGHT
ASCT WITH THE VIGOROUS PACIFIC COLD FRONT...HAVE INCREASED WINDS
IN THAT BASIN TO 25 TO 35 WITH GUSTS TO 45 MPH FOR SATURDAY NT.
THE NOSE OF THE COOLER H7 WINDS WILL LIKELY DIVE INTO JOHNSON
COUNTY SO THEIR WINDS COULD INCREASE NOTICEABLY AS WELL. SOME
LIGHT PRECIP COULD SPILL OVER DVD BY SATURDAY NIGHT. RAIN/SNOW
BANDING IS POSSIBLE OFF THE OWL CREEK/BRIDGER MTNS AND INTO
FREMONT AND NATRONA COUNTIES WITH UNSTABLE H7 NW FLOW SATURDAY NT.
INVERSIONS WILL FINALLY ERODE SATURDAY NIGHT.

.LONG TERM...SUNDAY THROUGH THURSDAY

MOIST NW FLOW BEHIND OUR SATURDAY SHORTWAVE AS LONGWAVE RIDGE AXIS
HOLDS TO THE WEST WILL LIKELY LEAD TO A WARM ADVECTION/UPGLIDE
PATTERN SUNDAY INTO MONDAY. COULD SEE SOME SIGNIFICANT SNOW IN THE
FAR WEST SUNDAY INTO AT LEAST PART OF MONDAY. TEMPS WARM ENOUGH THAT
ANY PCPN COULD START MIXING WITH OR CHANGING TO RAIN IN THE FAR WEST
VALLEYS MONDAY...ESPECIALLY THE FURTHER SOUTH ZONES. SIGNIFICANT
WIND WILL LIKELY BE BLOWING DURING THIS TIME DUE TO THE FAST
FLOW...INCREASE SFC PRESSURE GRADIENT...SHORTWAVE DIVING SE AND
ADDED SUPPORT FROM JET ALOFT. HEIGHTS TRY AND REBUILD AROUND THE
MIDDLE OF THE WEEK WITH ONE GLANCING SHORTWAVE POSSIBLY AFFECTING
THE FAR NERN ZONES LATE TUESDAY WITH AT LEAST A FRONTAL BOUNDARY AND
SOME INCREASED WIND. THE NEXT WEAKENING TROUGH...AS IT MOVES THROUGH
THE MEAN RIDGE...ARRIVES LATE WED NGT/THURSDAY WITH SOME LIGHT TO
POTENTIALLY MODERATE SNOW FOR THE WEST AND A LITTLE FOR THE SOUTH
WITH ANOTHER ROUND OF GUSTY TO STRONG WIND. SNOW WILL CONTINUE TO
MELT...ESPECIALLY EAST OF THE DIVIDE LEADING TO A BETTER CHANCE OF
SOME MIXED DAYS AS SHORTWAVES AND INCREASED PRESSURE GRADIENT HELP
BREAK THE INVERSIONS. MOST AREAS WILL BE ON THE TEMP UPTREND SUNDAY
THROUGH MIDWEEK WITH SOME COOLER/COLDER AIR ARRIVING IN THE WEST
NEXT THURSDAY.

&&

.AVIATION.../12Z ISSUANCE/
AREAS OF FOG AND LOW CLOUDS IN FAR WEST WY THROUGH 17Z WITH MVFR TO
LIFR CONDITIONS EXPECTED. OTHERWISE VFR CONDITIONS TO PREVAIL OVER
THE REGION THROUGH 00Z.

AFTER 00Z...SCATTERED SNOW SHOWERS OVER THE NORTHERN WY MOUNTAINS
WITH LOCAL MVFR CONDITIONS AND SOME MOUNTAIN OBSCURATION THROUGH 12Z
FRI. THE REST OF THE REGION WILL SEE VFR CONDITIONS FROM 00Z TO 12Z
FRIDAY.

&&

.FIRE WEATHER...

STEEP TEMPERATURE INVERSIONS...ESPECIALLY IN THE WESTERN VALLEYS
WILL LEAD TO VERY POOR SMOKE DISPERSION THIS WEEK.
WINDS...HOWEVER...WILL BE ON THE BREEZY SIDE ACROSS THE USUAL WIND
PRONE AREA OF CENTRAL WYOMING...WHICH WILL IMPROVE SMOKE DISPERSION
IN THESE AREAS. THE NEXT POTENTIAL FOR MEASURABLE SNOW WILL BE
ACROSS FAR WESTERN WYOMING SATURDAY AND SATURDAY NIGHT. WINDS WILL
INCREASE IN MANY AREAS BY SATURDAY.

&&

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

$$

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


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