Area Forecast Discussion
Issued by NWS Riverton, WY

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FXUS65 KRIW 310846
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
246 AM MDT FRI JUL 31 2015

.SHORT TERM...TODAY THROUGH SUNDAY NIGHT

WV IMAGERY SHOWING RIDGE WRN CONUS...TROF ERN CONUS. UPR LVL CENTER
OF THIS HIGH LOCATED OVR NM WITH A SMALL BUT STRONGER EMBEDDED WAVE
OVR SFC LOW...VERY TROPICAL LOOKING...OVR THE NRN BAJA REGION.
UPSTREAM OVR WA...WEAK SW ATOP OF RIDGE WHICH WILL ARRIVE OVR NERN
WY THIS EVE. UPR BUBBLE WILL LARGELY PROTECT THE FA AND POINTS
WEST...FOR NOW...FROM MOST PRECIP ACTIVITY...KEEPING LOW CHANCES FOR
POPS OVR THE ERN CWA TO THE HIGH/CNTRL PLAINS. SFC HAS GENERAL HIGH
P ACROSS THE FA...WITH LOW P AND AN ATTENDANT WEAK WARM FRONT FROM
ERN UT INTO WRN CO.

HOT AND DRY FOR THE MOST PART WITH AMPLIFIED PORTION OF THE RIDGE
AXIS CAPPING MOST OF THE FA...KEEPING SHOWERS AND STORMS AT A
MINIMUM...LARGELY RELEGATED ON AN ISOLATED BASIS TO A FEW OF THE
HIGHEST PEAKS...SUCH AS THE ABSAROKAS AND BIGHORNS LATE TODAY/THIS
EVE. ADDITIONALLY TODAY...LOW P OVR UT WILL ALLOW FOR A WEAK WARM
FRONT TO BUILD ACROSS THE WY/CO BORDER AREA...LIFTING ACROSS ERN WY
INTO FRI EVENING WITH SOME MODEST MOISTURE RETURNING TO ERN
WY...WITH SOME LOW CHCS FOR THUNDER BY THIS EVENING AS A SMALL SW
TROF ARRIVES OVERHEAD THRU THE RIDGE THIS EVENING. ATTM...DOES NOT
LOOK LIKE MUCH OF THIS MOISTURE WILL MAKE IT BACK INTO THE ERN
ZONES...BUT CASPER MOUNTAIN...AND TO A LESSER EXTENT THE REST OF
NATRONA OR JOHNSON COUNTY MAY SEE AN ISOLATED LATE DAY T-STORM.
SATURDAY WILL BE WITHOUT PRECIP EVERYWHERE AS DRY AIR ADVECTS FROM
THE WEST OVR THE FA AND ANY SIGNIFICANT MOISTURE IS HELD AT BAY TO
THE SOUTH. SUNDAY...HOTTEST DAY OF THE PERIOD...BUT WEAK MOISTURE
DOES START TO SLOWLY WORK ITS WAY TOWARD AND INTO THE FA THRU THE
DAY...ALLOWING FOR LOW CHANCE PRECIP ACROSS FAVORED MOUNTAIN RANGES
LATER SUNDAY EVENING AND OVERNIGHT PERIOD. THIS WILL BE A PRECURSOR
TO SOMEWHAT BETTER CHCS FOR PRECIP LATER MONDAY...AS THE UPR RIDGE
AXIS ROTATES CLOCKWISE AND CENTERS THRU THE CENTER OF WY...AND SOME
MODEST MONSOONAL TYPE MOISTURE STARTS TO FEED ACROSS THE
INTERMOUNTAIN WEST JUST AHEAD OF  WHAT WAS THE BAJA DISTURBANCE
DESCRIBED ABOVE.

.LONG TERM...MONDAY THROUGH FRIDAY

IT APPEARS THAT THE LONG RANGE MODELS ARE NOW LATCHING ON TO A
WEATHER SYSTEM ROTATING THROUGH THE GREAT BASIN MONDAY. A PORTION
OF THIS WAVE MOVES INTO WY MONDAY AFTERNOON AND THEN PROGRESSES
NORTHWARD THROUGH TUESDAY MORNING. CURRENT FORECAST FOR MONDAY
THROUGH TUESDAY MORNING REFLECTS A HIGHER PRECIP CHANCE IN SOME
AREAS AND DID NOT ALTER THAT FORECAST MUCH. A SOUTHWEST FLOW ALOFT
IS FORECAST TUE PM THROUGH FRIDAY. THIS IS DUE TO AN UPPER LEVEL
STORM SYSTEM THAT ROTATES OFF THE WEST COAST OF CANADA TUESDAY AND
THEN GRADUALLY SINKS SOUTH TO JUST OFF THE NW COAST OF THE U.S.
NEXT FRIDAY. IN THIS SW FLOW ALOFT A FEW WEATHER DISTURBANCES PASS
THROUGH WHICH WOULD BRING A LITTLE HIGHER CHANCE OF STORMS. TIMING
THESE THAT FAR OUT IS NOT EASY OR CONSISTENT. THE 00Z RUNS BRING
ONE DISTURBANCE THROUGH ON WEDNESDAY FOLLOWED BY ANOTHER THURS
NIGHT. I ADJUSTED SOME PRECIP CHANCES ON THOSE DAYS AND NIGHTS BUT
I EXPECT THE TIMING TO CHANGE IN THE COMING DAYS. AS FOR
TEMPS...MONDAY NOW LOOKS COOLER DUE TO MORE CLOUDS AND GREATER
COVERAGE OF SHOWERS OR STORMS. TUE THROUGH FRIDAY WILL BE WARM TO
LOCALLY HOT WITH 80S TO LOW 90S FOR MOST LOWER ELEVATIONS...WITH
UPPER 70S TO LOW 80S IN THE WESTERN VALLEYS. AS STATED
PREVIOUSLY...THE LIGHTNING THAT IS PRODUCED BY THE STORMS NEXT
WEEK WILL LIKELY START SOME FIRES IN PLACES WHERE THE FUELS ARE
RIPE FOR BURNING. THIS THREAT WILL CONTINUE TO BE ANALYZED OVER
THE COMING DAYS.

&&

.AVIATION.../12Z ISSUANCE/

VFR CONDITIONS ARE EXPECTED THROUGH 12Z SATURDAY. THE WIND WILL BE
LIGHT AND VARIABLE AND FOCUS ON TERRAIN INFLUENCES. A FEW FAIR
WEATHER CUMULUS MAY DEVELOP OVER A FEW LOCATIONS. ISOLATED SHOWERS
MAY DEVELOP AFTER 21Z ACROSS EASTERN WYOMING BUT WILL STAY AWAY FROM
TAF SITES.

&&

.FIRE WEATHER...

MINIMUM RH VALUES ARE EXPECTED TO REMAIN IN THE SINGLE DIGITS TO LOW
TEENS THROUGH THE WEEKEND ACROSS THE SOUTH AND LOW ELEVATION AREAS
EAST OF THE DIVIDE...WITH UPPER TEENS AND 20S OVER THE MOUNTAINS.
RELATIVE HUMIDITY WILL HAVE LITTLE TIME RECOVERING
OVERNIGHT...ESPECIALLY AT MID SLOPE WHERE RHS MAY NOT RISE OUT OF
THE MID 20S IN THE CENTRAL WYOMING RANGES. GENERALLY LIGHT WINDS ARE
EXPECTED THROUGH THE WEEKEND...WITH ONLY A FEW LIGHT BREEZES
POSSIBLE IN THE AFTERNOON AND EVENINGS ACROSS THE LOWER ELEVATIONS
OF CENTRAL AND SOUTHERN WYOMING. OTHERWISE...A VERY DRY ATMOSPHERE
WITH HIGH PRESSURE AT THE SURFACE AND ALOFT WILL KEEP MOST CHANCES
FOR ANY PRECIPITATION ISOLATED AND RELEGATED TO MAINLY A FEW
MOUNTAIN OR EASTERN ZONES LATER TODAY. LITTLE IF ANY CHANCE FOR
SHOWERS/STORMS WILL OCCUR ON SATURDAY AT ANY LOCATION. SUNDAY WILL
SEE THE WARMEST TEMPERATURES OF THE WEEKEND...HOWEVER MOISTURE WILL
SLOWLY ALSO BE INCREASING WITH ISOLATED THUNDERSTORM CHANCES
RETURNING LATER IN THE DAY AND OVERNIGHT...WITH WIDELY SCATTERED
CHANCES FOR PRECIPITATION BY MONDAY AFTERNOON.

&&

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

&&

$$

SHORT TERM...BRAUN
LONG TERM...AR
AVIATION...HATTINGS
FIRE WEATHER...BRAUN



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