Area Forecast Discussion
Issued by NWS Riverton, WY

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FXUS65 KRIW 311956
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
156 PM MDT SUN MAY 31 2015

.SHORT TERM...TODAY THROUGH TUESDAY NIGHT

RIDGE OF HIGH PRESSURE OVER THE FORECAST AREA TODAY WILL HELP TO
DELAY SHOWER AND THUNDERSTORM ACTIVITY UNTIL THE LATE AFTERNOON AND
EVENING AS MOISTURE FILLS IN ACROSS THE AREA. PRIOR TO STORM
DEVELOPMENT...SOME PATCHY FOG WILL BE POSSIBLE ACROSS THE WESTERN
VALLEYS. ANY FOG DEVELOPMENT SHOULD LIFT BY THE LATE MORNING HOURS.
STORMS MAY AGAIN PRODUCE SMALL HAIL AND GUSTY WIND INTO THE EVENING
HOURS. THE RIDGE REMAINS OVER THE AREA THROUGH MONDAY MORNING.

AS THE RIDGE MOVES EASTWARD...INCREASING SOUTHWEST FLOW WILL MOVE
OVER THE AREA TO HELP INITIATE AFTERNOON SHOWERS AND THUNDERSTORMS.
MONDAY LOOKS LIKE AN INTERESTING DAY ACROSS THE FORECAST AREA...WITH
THE POTENTIAL FOR SOME STRONGER THUNDERSTORMS. CAPE AND LIFTED INDEX
VALUES STRENGTHEN THROUGH THE AFTERNOON...THOUGH THE BEST INSTABILITY
LOOKS TO BE NORTH AND ESPECIALLY EAST OF THE FORECAST AREA.
REGARDLESS...STRONG STORMS ARE NOT OUT OF THE QUESTION. STORMS LOOKS
MOST FAVORABLE ACROSS JOHNSON AND NATRONA COUNTIES...AND ACROSS THE
EASTERN HALF OF THE BIG HORN BASIN. CONDITIONS WILL CONTINUE TO BE
MONITORED AND UPDATED AS THIS SYSTEM ADVANCES. STRONG WIND AND HAIL
LOOK TO BE THE BEST THREATS WITH STORM ACTIVITY WITH MODELS SHOWING
PWATS GENERALLY LESS THAN AN INCH.

ACTIVITY SHOULD WEAKEN THROUGH THE OVERNIGHT HOURS OF MONDAY...BUT
THE TREND OF AFTERNOON SHOWERS AND THUNDERSTORMS WILL CONTINUE
TUESDAY WITH ANOTHER...WEAKER...SURGE OF MOISTURE EXPECTED. SHOWERS
AND THUNDERSTORMS FOR TUESDAY LOOK MORE FAVORABLE FOR DEVELOPMENT
ACROSS NORTHERN WYOMING WITH DRYING CONDITIONS FAVORABLE OVERNIGHT.

.LONG TERM...WEDNESDAY THROUGH SUNDAY

AN ACTIVE WEATHER PATTERN CONTINUES THROUGH THE EXTENDED WITH DAILY
BOUTS OF ISOLATED TO SCATTERED CONVECTION. EXPECT SOME BOUTS OF
STRONG TO POSSIBLY SEVERE CONVECTION DURING THE LONG TERM...ESPECIALLY
ALONG AND NORTH OR EAST OF ANY SURFACE BOUNDARY. ALSO CONSECUTIVE
WARM TO VERY WARM DAYS IN THE SHORT TERM INTO THE LONG TERM...WILL
PROMOTE HIGH ELEVATION SNOWMELT. THIS COMBINED WITH LOCALIZED
HEAVY RAINFALL FROM THUNDERSTORMS AND ALREADY SATURATED GROUNDS
WILL KEEP LOCALIZED FLOODING A CONCERN.

A COUPLE OF SHORTWAVES IN THE WEST/SOUTHWEST FLOW...AND A QUASI-
STATIONARY FRONT WILL KEEP CHANCES OF CONVECTION GOING WEDNESDAY
AND THURSDAY...WITH THE BEST CHANCES OVER THE NORTH...WITH THE
LEAST OVER THE FAR SOUTH.

MEDIUM RANGE MODELS ARE IN GOOD AGREEMENT WITH A TROUGH PUSHING INTO
THE WEST COAST WEDNESDAY NIGHT...BECOMING A CUT OFF UPPER LOW OVER
CENTRAL CALIFORNIA THURSDAY INTO THURSDAY NIGHT. GLOBAL MODELS THEN
KEEP THIS UPPER LOW ACROSS CENTRAL/SOUTHERN CALIFORNIA OR SOUTHERN
GREAT BASIN AREA THROUGH SATURDAY NIGHT. MODELS THEN SLOWLY FILL
THIS UPPER LOW...AND LIFT IN NORTHEAST ACROSS THE ROCKIES EARLY NEXT
WEEK. THE 00Z MODELS ARE SHOWING SOME SIGNIFICANT ENERGY ROTATING
AROUND THIS UPPER LOW FRIDAY WHICH COULD IMPACT THE FORECAST AREA
WITH A GOOD SHOT OF CONVECTION. THE UNSETTLED WEATHER THEN CONTINUES
INTO THE WEEKEND FROM THE AFOREMENTIONED CUT OFF UPPER LOW...AS WELL
AS SOME NORTHERN STREAM ENERGY SKIRTING THE AREA WITH POSSIBLY A
COLD FRONT PUSHING SOUTH INTO THE AREA SATURDAY NIGHT AND SUNDAY.
WILL KEEP POPS MAINLY SLIGHT TO CHANCE WITH A PEAK IN THE
AFTERNOON/EVENING EACH DAY...BUT THERE WILL UNDOUBTEDLY BE SLIGHT
VARIANCES EACH DAY DEPENDING ON TIMING/PLACEMENT OF DISTURBANCES AND
SURFACE BOUNDARIES. THE WEEKEND HAS THE BEST POTENTIAL FOR
WIDESPREAD/STEADIER PRECIPITATION...ESPECIALLY IF THE NORTHERN
STREAM SYSTEM CAN ADD AN UPSLOPE COMPONENT TO WRING OUT THE
MOISTURE.

TEMPERATURES LOOK TO BE SEASONAL TO SLIGHTLY BELOW AVERAGE THROUGH
THE EXTENDED.

.AVIATION.../18Z ISSUANCE/

EAST OF THE DIVIDE...KCOD/KCPR/KLND/KRIW/KWRL ROUTES

VFR CONDITIONS WILL PREVAIL TODAY AND TONIGHT. ISOLATED
THUNDERSTORMS AND SCATTERED SHOWERS WILL OCCUR AFTER 20Z WITH LOCAL
MVFR CONDITIONS IN OR NEAR STORMS. AFTER 03Z ONLY ISOLATED SHOWERS
WILL OCCUR THROUGH 06Z MON.

WEST OF THE DIVIDE...KBPI/KJAC/KPNA/KRKS ROUTES

VFR CONDITIONS WILL PREVAIL TODAY AND TONIGHT. ISOLATED
THUNDERSTORMS AND SCATTERED SHOWERS WILL OCCUR AFTER 20Z WITH
LOCAL MVFR CONDITIONS. AFTER 03Z ONLY ISOLATED SHOWERS WILL OCCUR
THROUGH 06Z MON.

.FIRE WEATHER...

AFTERNOON SHOWERS AND THUNDERSTORMS WILL REMAIN THROUGH THE NEXT FEW
DAYS....AS TEMPERATURES CONTINUE TO WARM UNDER A STRENGTHENING AREA
OF HIGH PRESSURE. THOUGH HIGH PRESSURE USUALLY BRINGS MORE BENIGN
CONDITIONS WITH LOWERING HUMIDITY...THIS RIDGE HAS EXTRA MOISTURE
WITH IT. THIS ADDITIONAL MOISTURE WILL HELP INCREASE SHOWER AND
THUNDERSTORM ACTIVITY THROUGH MONDAY EVENING. SOME STRONGER STORMS
MAY DEVELOP ON MONDAY...RESULTING IN STORMS WITH STRONG
WIND...HAIL...AND FREQUENT LIGHTNING. THIS SCENARIO CONTINUES TO BE
MONITORED...WITH THE BEST OPPORTUNITY APPEARING TO BE ACROSS EASTERN
WYOMING. AREAS OF CONTINUED RAINFALL WILL HELP TO ALLEVIATE FIRE
WEATHER CONCERNS...THOUGH THUNDERSTORM ACTIVITY ALWAYS RAISES SOME
CONCERN OVER THOSE AREAS WHICH ARE EXPERIENCING DRIER FUELS.

&&

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

$$

SHORT TERM...BRANHAM
LONG TERM...WM
AVIATION...C.BAKER
FIRE WEATHER...BRANHAM





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