Area Forecast Discussion
Issued by NWS Riverton, WY

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000
FXUS65 KRIW 260906
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
306 AM MDT FRI JUN 26 2015

.SHORT TERM...TODAY THROUGH SUNDAY NIGHT

HIGH PRESSURE CONTINUES TO BUILD TODAY OVER THE FORECAST
AREA...HELPING TO KEEP ADDITIONAL STORM ACTIVITY FROM DEVELOPING
THIS MORNING. PATCHY FOG WILL BE POSSIBLE AS A SIDE EFFECT FROM
SHOWER ACTIVITY ON THURSDAY ACROSS NATRONA AND JOHNSON COUNTY THIS
MORNING. ANY FOG DEVELOPMENT SHOULD LIFT BY THE LATE MORNING HOURS
UNDER THE CONTINUED INFLUENCE OF THE RIDGE OF HIGH PRESSURE. DESPITE
STRENGTHENING HIGH PRESSURE...SOME MOISTURE WILL IMPACT THE CENTRAL
MOUNTAINS...ALLOWING A FEW SHOWERS AND THUNDERSTORMS TO BE POSSIBLE
THIS AFTERNOON AND INTO THE EARLY EVENING. COVERAGE IS NOT LOOKING
OVERLY FAVORABLE...AND SHOULD ANY SHOWERS DEVELOP THEY SHOULD BE
SHORT LIVED.

THE AREA OF HIGH PRESSURE WILL BRING WARMING CONDITIONS THROUGH THE
WEEKEND...WITH SOME BASINS SEEING VALUES IN THE MID 90S. DAYTIME
HUMIDITY WILL ALSO DECREASE UNDER THE DRIER AIR. THANKFULLY...MOST
OF THE AREA SHOULD EXPERIENCE GENERALLY LIGHT WIND.

AFTERNOON MOISTURE WILL STRENGTHEN OVER THE NEXT COUPLE OF
DAYS...ALLOWING ADDITIONAL SHOWER AND THUNDERSTORM POTENTIAL EACH
DAY. STILL...SHOWER AND THUNDERSTORM ACTIVITY IS GENERALLY EXPECTED
TO REMAIN CONFINED TO THE MOUNTAIN LOCATIONS.

.LONG TERM...MONDAY THROUGH FRIDAY

SYNOPSIS...STRONG UPPER LEVEL HIGH PRESSURE WILL REMAIN OVER THE
GREAT BASIN/INTERMOUNTAIN WEST THROUGH THE PERIOD.  HIGHS ACROSS
MOST BASINS AND VALLEYS MAINLY RANGE FROM THE UPPER 80S TO MID 90S
THROUGH THE PERIOD.  THUNDERSTORM ACTIVITY WILL BE MOSTLY ISOLATED
AND CONFINED TO THE NORTHERN HALF OF THE AREA.

DISCUSSION...THE MAIN OVERALL TREND IN MEDIUM-RANGE GUIDANCE THIS
MORNING WAS TO KEEP HIGHER HEIGHTS ACROSS THE ROCKIES...OR LESS
FLATTENING OF UPPER HIGH OVER THE GREAT BASIN BY `RIDGE RIDERS`
PUSHING ACROSS THE NORTHERN ROCKIES.  GFS MAINTAINS HIGHER HEIGHTS
OVER THE AREA IN THE LATTER PART OF THE WEEK THAN THE ECMWF.  THE
MAIN FORECAST PROBLEM WILL BE HOW FAR UPPER HIGH DRIFTS NW FROM THE
GREAT BASIN ACROSS THE INTERMOUNTAIN WEST THROUGH NEXT WEEK.  IF
CURRENT MODEL TRENDS CONTINUE...MORE OF THE AREA WILL REMAIN UNDER
THE INFLUENCE OF THE UPPER HIGH AND A HOTTER MORE STABLE AIRMASS
THROUGH THE WEEK.

CURRENTLY...MONDAY LOOKS TO BE THE WARMEST DAY THROUGH THIS PERIOD
WITH UPPER HIGH CENTERED OVER UTAH AND H7 TEMPS PROGGED FROM 21C IN
THE SW TO AROUND 17C IN THE NE.  THIS WILL TRANSLATE INTO LOWER TO
MID 90S ACROSS MOST VALLEYS AND BASINS WITH SOME READINGS NEAR 100
IN THE BIGHORN BASIN.  A SERIES OF PACIFIC DISTURBANCES THEN BEGIN
TO PUSH ACROSS THE NORTHERN PERIPHERY OF THE UPPER HIGH ACROSS THE
NORTHERN ROCKIES BEFORE DIVING SE ACROSS THE NORTHERN PLAINS THROUGH
THE REMAINDER OF THE WEEK...DRIVING OCCASIONAL WEAK FRONTAL
BOUNDARIES SOUTH INTO NORTHERN AND CENTRAL WYOMING. CONFIDENCE ON
THE STRENGTH AND TIMING OF THESE DISTURBANCES AND ASSOCIATED
FRONTS REMAIN LOW...BUT FORECAST REFLECTS THE OVERALL WEAKER
FURTHER NORTHWARD TREND WITH THESE SYSTEMS...KEEPING THUNDERSTORM
COVERAGE ISOLATED ACROSS NORTHERN AND CENTRAL AREAS TUESDAY
THROUGH FRIDAY AND TRENDING TEMPERATURES WARMER...OR ONLY A SLIGHT
OVERALL COOLING TREND IF ANY. MUCH OF THE AREA...ESPECIALLY
WESTERN WYOMING...WILL LIKELY SEE ELEVATED FIRE DANGER HEADING
INTO THE FOURTH OF JULY WEEKEND IN THIS PATTERN.

&&

.AVIATION.../12Z ISSUANCE/

MVFR/IFR CEILINGS AND POSSIBLY SOME FOG ARE EXPECTED TO IMPACT
PORTIONS OF JOHNSON AND NATRONA COUNTIES...INCLUDING THE KCPR
TERMINAL THROUGH ABOUT 16Z. OTHERWISE...VFR CONDITIONS WITH ONLY FEW
TO SCT CLOUDS ARE EXPECTED WITH MAINLY LIGHT WINDS. VERY ISOLATED
AFTERNOON CONVECTION IS POSSIBLE OVER THE MOUNTAINS...BUT CONVECTION
WILL BE HARD PRESSED TO DEVELOP AS A STRONG UPPER RIDGE BUILDS INTO
THE AREA. LATE FRIDAY NIGHT...BOUNDARY LAYER MIGHT MOISTEN UP ENOUGH
FOR THE POSSIBILITY OF FOG/LOW CLOUDS OVER JOHNSON AND NATRONA
COUNTIES. HOWEVER FOG/LOW CLOUDS WILL BE LESS WIDESPREAD THAN WHAT
OCCURS THIS MORNING.

&&

.FIRE WEATHER...

HIGH PRESSURE WILL HELP TO BRING DRIER CONDITIONS FOR THE NEXT FEW
DAYS. SOME AFTERNOON SHOWERS AND THUNDERSTORMS WILL BE
POSSIBLE...MAINLY ACROSS CENTRAL WYOMING. CONFIDENCE IN STORM
DEVELOPMENT IS GENERALLY LOW UNDER THE BUILDING RIDGE OF LOW
PRESSURE. EXPECT WARMING TEMPERATURES TO CONTINUE...WITH DAYTIME
HUMIDITY DECREASING INTO THE TEENS...ESPECIALLY ACROSS SOUTHWESTERN
WYOMING. WIND SHOULD GENERALLY REMAIN LIGHT UNDER THE INFLUENCE OF
THE HIGH PRESSURE.

&&

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

$$

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



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