Area Forecast Discussion
Issued by NWS Riverton, WY

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FXUS65 KRIW 270941
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
341 AM MDT SUN JUL 27 2014

.SHORT TERM...TODAY THROUGH TUESDAY NIGHT
HIGH PRESSURE ALOFT AND AT THE SURFACE AS WELL AS CONFLUENT FLOW
ALOFT WILL ASSURE UNEVENTFUL WEATHER TODAY. THE RH WILL BE LOW
BUT THE WINDS WILL BE LIGHT. ON MONDAY A WEAK VORT LOBE WILL
TRAVEL UP THE BACK SIDE OF THE RIDGE AND WILL PRODUCE LOW POPS FOR
LATE MONDAY. A MUCH BETTER CHANCE OF SCATTERED THUNDERSTORMS IS
EXPECTED FOR TUESDAY AFTERNOON AND EVENING AS A CLOSED LOW
DEVELOPS OVER IDAHO AND THE INCREASINGLY DIFLUENT SOUTHWEST FLOW
INCREASES OVER THE AREA AHEAD OF THIS H5 CLOSED LOW. IN
ADDITION...A MID LEVEL CIRCULATION WILL DEVELOP OVER EASTERN
FREMONT COUNTY AND WILL DRIFT TO THE CPR AREA INCREASING THE
CHANCES FOR THUNDERSTORMS. ANY STORMS THAT FORM WILL NOT BE HIGH
BASED TUESDAY AS DEW POINTS CREEP UP INTO THE 40S AND HIGH TEMPS
DROP ABOUT 10 DEGREES SO LOCALLY HEAVY RAINFALL WILL BE LIKELY
FROM SOME OF THESE CELLS.

.LONG TERM...WEDNESDAY THROUGH SUNDAY
UPPER LEVEL RIDGE AXIS TO REMAIN ROUGHLY ALONG 110W THROUGH THE
PERIOD.  SUB-TROPICAL UPPER LOW MOVING NORTHWARD ACROSS THE GREAT
BASIN ON TUESDAY WILL REACH ITS NORTHWARD EXTENT ACROSS EASTERN
IDAHO WEDNESDAY MORNING.  GFS AND ECMWF HAVE REACHED BETTER
AGREEMENT ON TRACK FOLLOWING THIS APEX...SHEARING OUT THE UPPER
LOW SE ACROSS THE SOUTH HALF OF WYOMING WEDNESDAY AND WEDNESDAY
NIGHT. THIS TRACK WILL PUT THE MOST WIDESPREAD SHOWERS AND
THUNDERSTORMS ROUGHLY ALONG AND SOUTH OF A JACKSON TO CASPER LINE
WITH THIS ACTIVITY GRADUALLY SHIFTING SOUTH AND EAST WEDNESDAY
NIGHT INTO SE WYOMING AND COLORADO. FORECAST CONTINUES TO GO ON
THE LOW SIDE OF GUIDANCE HIGH TEMPERATURES ON WEDNESDAY ACROSS THE
SOUTH WITH MOSTLY CLOUDY SKIES AND GOOD SHOWER AND THUNDERSTORM
COVERAGE. WE WILL STILL SEE THE POTENTIAL FOR SOME HEAVY RAIN WITH
SLOW-MOVING LOW TOP CONVECTION...ESPECIALLY ALONG THE TRACK OF THE
UPPER LOW. ON THE PLUS SIDE...THIS TRACK LOOKS TO BE OVER SOME OF
THE DRIEST PARTS OF THE STATE ACROSS SWEETWATER COUNTY UP TO THE
SOUTHERN WIND RIVER RANGE AND GREEN MOUNTAINS.

REMNANTS OF MONSOONAL PLUME ARE SHIFTED FURTHER WEST ON THURSDAY
FROM THE FOUR CORNERS REGION NW ACROSS IDAHO...SO A DRIER AIRMASS
WILL PREVAIL OVER CENTRAL WYOMING WITH ISOLATED TO SCATTERED
THUNDERSTORMS BLOSSOMING OVER THE HIGH TERRAIN ACROSS THE WEST.

GFS AND ECMWF TRACK THE NEXT CLUSTER OF SUB-TROPICAL DISTURBANCES
FURTHER OUT AROUND THE PERIPHERY OF THE RIDGE...NORTH ACROSS IDAHO
FRIDAY AND NE-E ACROSS NW WYOMING AND MONTANA FRIDAY NIGHT.  THIS
WILL BRING A BETTER CHANE OF THUNDERSTORMS TO THE NW MTNS ON FRIDAY
WITH SOME OF THIS ACTIVITY PUSHING INTO THE CENTRAL BASINS.

DETERMINISTIC SOLUTIONS SHOW MUCH LESS AGREEMENT NEXT WEEKEND WITH
INDIVIDUAL DISTURBANCES ROTATING AROUND THE PERIPHERY OF THE
RIDGE...BUT GENERALLY AGREE ON KEEPING PLUME OF MONSOONAL MOISTURE
RUNNING SE-NW FROM THE FOUR CORNERS REGION ALONG AND WEST OF THE
CONTINENTAL DIVIDE...WHERE THE "RING OF FIRE" CONVECTION WILL
BLOSSOM WITH DAYTIME HEATING.

&&

.AVIATION.../12Z ISSUANCE/

ISOLATED HIGH BASED CONVECTION COULD OCCUR MAINLY OVER EXTREME
SOUTHERN WYOMING NEAR THE UTAH/COLORADO BORDER THIS
AFTERNOON/EVENING. THE MAIN HAZARD FROM THIS ACTIVITY WILL BE SOME
STRONG GUSTY WINDS. OTHERWISE...VFR CONDITIONS WILL OCCUR
TODAY...WITH A MAINLY LIGHT EASTERLY SURFACE FLOW.

&&

.FIRE WEATHER...
HIGH PRESSURE WILL KEEP WARM AND DRY CONDITIONS OVER THE FORECAST
AREA THROUGH TODAY. MANY AREAS WILL SEE HUMIDITY DIP INTO THE LOW
TEENS DURING THE AFTERNOON HOURS. RELATIVELY LIGHT WIND EXPECTED
THROUGH TODAY...KEEPING CRITICAL FIRE BEHAVIOR MUTED. THE NEXT
MORE WIDESPREAD ROUND OF SHOWER ACTIVITY LOOKS TO DEVELOP LATE
MONDAY AND INTO TUESDAY. WEDNESDAY ALSO LOOKING FAVORABLE FOR
SHOWER AND THUNDERSTORM ACTIVITY... ESPECIALLY FOR AREAS WEST OF
THE DIVIDE. THREATS WITH ACTIVITY COULD BE DRY LIGHTNING AND GUSTY
WIND.

&&

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

$$

SHORT TERM...LIPSON
LONG TERM...AEM
AVIATION...WM
FIRE WEATHER...LIPSON








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