Area Forecast Discussion
Issued by NWS Riverton, WY

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000
FXUS65 KRIW 242045
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
245 PM MDT MON AUG 24 2015

.SHORT TERM...TONIGHT THROUGH TUESDAY

A WEAK DISTURBANCE PRODUCED AN EARLY SHOW OF ELEVATED LIGHT SHOWERS
AND A FEW LIGHTNING STRIKES TO SOUTHWEST WY THIS MORNING. AS THIS
IMPULSE TRACKS NORTHEAST OF THE DIVIDE AND AROUND THE HIGH CENTERED
OVER THE FOUR CORNERS REGION...WE SHOULD SEE ANOTHER ROUND OF
AFTERNOON CONVECTION BUT THESE CELLS WILL BE PRIMARILY MTN HUGGERS
WITH LIGHT WINDS ALOFT AND HIGH TEMP/DEW POINT SPREADS AT THE LOWER
ELEVATIONS. SURFACE BASED CONVECTION HAS ALREADY DEVELOPED FROM THIS
WEATHER FEATURE OVER THE UINTA MTNS AND IS TRYING TO MOVE INTO
SOUTHWEST SWEETWATER COUNTY AT THE TIME OF THIS WRITING. INDICATED
ISOLD ACTIVITY MAINLY OVER THE MTNS THROUGH THIS EVENING. AS THE
HIGH CONTINUES TO AMPLIFY TUESDAY...OUR WEST AND NORTHWEST ZONES
WILL BE CLOSEST TO THE RING OF FIRE AROUND THE PERIPHERY OF THE
HIGH AS A WEAK IMPULSE ROUNDS THE HIGH. THIS WX FEATURE WILL
CREATE A LATER SHOW OF CONVECTION TUESDAY...ALBEIT WEAK WITH
UNIMPRESSIVE MOISTURE AND INSTABILITY. RH WILL DECREASE AT THE
LOWER ELEVATIONS DURING THE DAY TUESDAY BUT INCREASE OVER THE
HIGHER PEAKS TUE. ANY CONVECTION THAT FORMS TODAY AND TUE WILL
FEATURE MAINLY SOME DRY LIGHTNING AS WELL AS GUSTY AND ERRATIC
WINDS. TUESDAY WILL LIKELY BE THE HOTTEST DAY OF THE WEEK IN MANY
AREAS WITH HIGHS IN THE MID 90S AT THE LOWER ELEVATIONS EAST OF
THE DIVIDE AND MID 80S WEST. THE MOST EXAGGERATED TEMP/DEW SPREADS
SHOULD OCCUR TO THE EAST WITH CASPER SEEING ANY CUMULUS THAT
MANAGE TO FORM HAVING BASES AROUND 15K WITH A TEMP/DEW SPREAD OF
75 DEGREES. GREAT INGREDIENTS FOR THE TYPE OF T STORMS MENTIONED
ABOVE THAT DEVELOP IN OUR CWA TUE. ONE SIDE NOTE...THE FAR WEST
VALLEYS AND BASINS WILL LIKELY SEE SOME LOW TEMPS IN THE 30S ONCE
AGAIN TONIGHT.

.LONG TERM...TUESDAY NIGHT THROUGH MONDAY

A COUPLE WEAK DISTURBANCES IN THE FLOW LATE TUESDAY WITH LIMITED
INSTABILITY AND MAINLY OVER THE MOUNTAINS. MODELS HAVE TRENDED
FURTHER NORTH WITH OUR WED/WED NGT SYSTEM. THE MAIN DISTURBANCE/VORT
NOW DEVELOPS IN BAJA AND LIFTS NWD MORE INTO WRN OR EVEN NWRN WYO ON
WEDNESDAY. SIGNIFICANT TIMING AND LOCATION DIFFERENCES EXIST AGAIN
TODAY. THE OTHER VORT STILL ROTATES NWD OUT OF AZ BUT IS MUCH WEAKER
IN THE GUIDANCE TODAY AS IT MOVES INTO FAR SRN WYO WED. GFS INIT
LOOKS BETTER THAN THE NAM TODAY BASES ON STLT AND AM FOLLOWING IT
TODAY WITH MAIN SHORTWAVE ARRIVING IN THE SW WED AFTN INTO EARLY
WED EVENING AND THEN MOVING NE INTO THE BIG HORN BASIN WED NGT
BEFORE EXITING THE NERN ZONES THUR MORNING. SIGNIFICANT MOISTURE
SURGE STILL EXPECTED WITH PW`S SURGING TO AROUND ONE INCH IN THE
WEST AND SOUTH LATE WEDNESDAY AND THEN MOVING ALONG THE PATH OF
THIS SYSTEM WED NGHT. NOT A LOT OF CAPE TO WORK WITH BUT SOME IN
THE FAR SOUTH LATE WED AND IN THE FAR WEST. OTHERWISE...WE`LL
LIKELY HAVE A FEW HEAVIER SHOWERS/TSTMS TO DEAL WITH LATE WED INTO
WED NGT. ON THURSDAY...WE GET SOME DECENT DAYTIME HEATING OUT WEST
WITH SOME BUILDING CAPES LIKELY LEADING TO SCT AFTN
CONVECTION...ESPECIALLY IN THE MTNS. IN THE ERN ZONES...SYSTEM MAY
ACTUALLY BE CLOSE ENOUGH YET FOR A SLIGHT CHANCE OF MORNING
SHOWERS WITH PERHAPS ISOLD AFTN CONVECTION STILL
POSSIBLE...ESPECIALLY IN THE MTNS. IN THE MEDIUM RANGE
PERIOD...THE ECMWF HAS TRENDED STRONGLY TOWARDS THE GFS OVER THE
WEEKEND AS EXPECTED WITH A SHORTWAVE AT HIGH LATITUDES WEST OF
THE DATELINE MOVING E/SE TOWARDS OUR ERN PACIFIC TROUGH KICKING IT
OUT OVER THE WEEKEND WITH MOST ENERGY ENDING WELL TO OUR NORTH.
ANOTHER SYSTEM CURRENTLY ON THE OTHER SIDE OF THE GLOBE AT HIGH
LATITUDE WILL THEN HELP TO GET THIS LOW MOVING INLAND AT THE END
OF THIS PERIOD. MORE MODEL DIFFERENCES EARLY NEXT WEEK THOUGH. OVERALL
A FAIRLY DRY AND WARM TO VERY WARM SW FLOW PATTERN WITH A FEW
RIPPLES AFFECTING MAINLY THE NWRN PORTIONS WITH LIMITED MAINLY MTN
CONVECTION. WINDS MAY INCREASE BY MON AFTN AHEAD OF OUR UPPER
TROUGH THAT SHOULD MOVE INLAND INTO THE PACNW ON MONDAY.

&&

.AVIATION.../00Z ISSUANCE/

MAINLY VFR CONDITIONS WILL PREVAIL THROUGH TUESDAY IN
SPITE OF THE SMOKE. ISOLATED SHOWERS AND STORMS WILL OCCUR OVER
WESTERN WY UNTIL 03Z. OUTFLOW WIND GUSTS TO 30 KNOTS WILL OCCUR FROM
SOME OF THE STORMS AND SHOWERS. ANOTHER ROUND OF ISOLATED SHOWERS
AND THUNDERSTORMS WILL OCCUR LATE IN THE AFTERNOON ON
TUESDAY...MAINLY OVER THE WESTERN MOUNTAINS.

&&

.FIRE WEATHER...

ELEVATED FIRE DANGER ACROSS THE ENTIRE FORECAST AREA THROUGH TUESDAY
AS WARM AND VERY DRY CONDITIONS CONTINUE.

WARMING CONTINUES ALONG WITH MINIMUM RH VALUES DROPPING INTO THE
LOWER TO MID TEENS EXCEPT 15 TO 20 PERCENT FAR WEST WITH ISOLATED
MAINLY MOUNTAIN STORMS THIS EVENING AND TUESDAY. WINDS WILL BE
RELATIVELY LIGHT IN MOST AREAS EXCEPT ALONG ELEVATED SOUTHWEST TO
NORTHEAST ORIENTED CANYONS WHERE SOUTHWEST WINDS COULD GUST TO 15 TO
20 MPH AT TIMES IN THE AFTERNOON. SOME LOWER ELEVATIONS WILL SEE A
SLIGHT DROP IN RH TUESDAY AFTERNOON OVER THIS AFTERNOON BUT HIGH
ELEVATIONS SHOULD SEE AT LEAST A SLIGHT INCREASE. INCREASING DEEP
DRY INSTABILITY ACROSS THE CENTRAL AND NORTHERN FORECAST AREA TODAY
AND TUESDAY...WILL PUSH HAINES VALUES TO EXTREME VALUES BETWEEN 5
AND 6...ESPECIALLY TUESDAY. ADDITIONALLY...AS MENTIONED
ABOVE...THERE WILL BE LOW CHANCES FOR ISOLATED DRY TYPE
THUNDERSTORMS WEST OF THE DIVIDE...MORE ISOLATED AND CONFINED TO THE
MOUNTAINS TUESDAY. INCREASING MOISTURE AND PRECIPITATION CHANCES
WILL ARRIVE ON WEDNESDAY...BRINGING A REPRIEVE FROM THE HOT AND DRY
CONDITIONS.

&&

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

&&

$$

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


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