Area Forecast Discussion
Issued by NWS Riverton, WY

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FXUS65 KRIW 170912
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
312 AM MDT THU JUL 17 2014

.SHORT TERM...THURSDAY THROUGH SATURDAY NIGHT

THE RADAR IS FINALLY QUIET EARLY THIS MORNING IN THE HUMBLE RIVERTON
WEATHER ABODE AS THE UPPER LEVEL LOW THAT CAUSED ALL OF THE MISCHIEF
OF THE PAST COUPLE OF DAYS MOVES TO THE SOUTHEAST. THE ONE
LEFTOVER MAY BE SOME PATCHY FOG IN NATRONA COUNTY WITH YESTERDAYS
STORMS SO WE ADDED SOME UNTIL 9 AM. RIDGING IS NOW BUILDING
ACROSS THE AREA AND SHOULD BRING DRY WEATHER THROUGH THE MORNING
HOURS. THERE WILL STILL BE THE CHANCE FOR A FEW SHOWERS AND
THUNDERSTORMS THIS AFTERNOON HOWEVER AS A SHORTWAVE MOVES OVER THE
TOP OF THE AFOREMENTIONED RIDGE. HOWEVER...WITH A MUCH DRIER
AIRMASS OVER THE AREA AND HIGHER HEIGHTS...COVERAGE SHOULD BE
RATHER LIMITED. AT THIS TIME...THIS LOOKS TO BE MAINLY OVER THE
HIGHER ELEVATIONS OF THE WESTERN MOUNTAINS WITH THE HIGHER
ELEVATION HEAT SOURCE. BUT EVEN HERE...THE VAST MAJORITY OF THE
DAY WILL BE RAIN FREE. WITH MORE SUNSHINE AND HIGHER
THICKNESSES...TEMPERATURES WILL BE ON AN UPWARD TREND BUT ONLY
BACK TO NEAR NORMAL LEVELS FOR MOST LOCATIONS.

BY FRIDAY...MANY AREAS WILL ONCE AGAIN EXPERIENCE ABOVE NORMAL
TEMPERATURES AS RIDGING BUILDS TO THE SOUTH. THIS MEANS HIGH
TEMPERATURES IN THE 90S RETURNING TO MANY OF THE BASIN LOCATIONS.
THIS WILL ALSO LEAD TO LOWER RELATIVE HUMIDITY THAT MAY INCREASE
FIRE DANGER. ANOTHER IN THE PARADE OF SHORTWAVES WILL ROUND THE BASE
OF THE RIDGE AND BRING ANOTHER RISK OF THUNDERSTORMS. HOWEVER...LIKE
THE PREVIOUS ONE THERE IS NOT MUCH MOISTURE TO WORK WITH SO ACTIVITY
WILL BE FAIRLY ISOLATED. CONTINUITY HAD THE COVERAGE HANDLED PRETTY
WELL SO WE MADE FEW CHANGES.

ABOVE NORMAL TEMPERATURES WILL ONCE AGAIN BE THE RULE FOR SATURDAY
WITH THE RIDGE STILL CONTROLLING THE WEATHER. ONE DIFFERENCE IS THAT
THE MODELS ARE SHOWING A BIT MORE MONSOONAL MOISTURE STARTING TO
CREEP INTO SOUTHERN PORTIONS OF WYOMING. THIS MAY HELP TO ENHANCE
CONVECTION ACROSS SOUTHERN PORTIONS OF WYOMING. ONCE
AGAIN...CONTINUITY HAS THIS HANDLED FAIRLY WELL SO AT THIS POINT WE
MADE ONLY COSMETIC CHANGES.

.LONG TERM...SUNDAY THROUGH THURSDAY

UPPER HIGH PRESSURE EXPANDS ACROSS THE SOUTHERN AND CENTRAL ROCKIES
SUNDAY THROUGH TUESDAY WITH BOTH GFS AND ECMWF SHOWING H5 600 DM
HIGH OVER SW COLORADO BY 00Z WEDNESDAY.  THERE IS GENERAL AGREEMENT
OF MEDIUM RANGE GUIDANCE ON SOME FLATTENING OF FLOW WED NT/THUR
TIMEFRAME AS TROUGH OFF THE NW COAST IS KICKED EAST ACROSS
SOUTHERN CANADA.

FOR DAY TO DAY WEATHER HIGHLIGHTS...

SUNDAY...A SUB-TROPICAL DISTURBANCE ORIGINATING ALONG THE COAST OF
BAJA CALIFORNIA WILL ROTATE AROUND THE PERIPHERY OF THE UPPER HIGH
ACROSS THE GREAT BASIN SUNDAY AND NE ACROSS WYOMING SUNDAY NIGHT.
THIS WILL BRING ISOLATED THUNDERSTORMS INTO THE SOUTH AND WEST
DURING THE AFTERNOON AND ACROSS CENTRAL WYOMING SUNDAY NIGHT.
RAINFALL AMOUNTS ARE EXPECTED TO BE LIGHT WITH MAINLY MID AND HIGH
LEVEL MOISTURE ABOVE A DRY BOUNDARY LAYER.

MONDAY AND TUESDAY...UPPER HIGH WILL BRING A VERY WARM AND STABLE
AIRMASS ACROSS SOUTHERN AND CENTRAL WYOMING WITH "THE RING OF FIRE"
OR ARC OF CONVECTION SHUNTED FURTHER NORTH...ACROSS THE WESTERN
MOUNTAINS AND NORTHERN BASINS MONDAY...AND ACROSS THE NORTHERN
MOUNTAINS AND FAR NORTH ON TUESDAY.  EXPECT HIGHS IN THE LOWER TO
MID 90S ACROSS THE CENTRAL BASINS WITH MOSTLY 80S IN THE WESTERN
VALLEYS.

WEDNESDAY AND THURSDAY...WEDNESDAY LOOKS TO BE THE HOTTEST DAY
ACROSS THE SOUTH AND CENTRAL WITH H7 20-22C THERMAL RIDGE AHEAD OF
PACIFIC COLD FRONT.  WE ARE LIKELY TO SEE SOME TRIPLE DIGIT
TEMPERATURES ACROSS THE LOWER BIGHORN BASIN AND EAST CENTRAL WY.
FRONTAL PASSAGE WEDNESDAY NIGHT WILL BRING SLIGHT CHANCES OF
THUNDERSTORMS ACROSS THE NORTH ALONG WITH COOLER TEMPERATURES ON
THURSDAY...BUT THIS FRONT IS EXPECTED TO HAVE LITTLE EFFECT ACROSS
THE SOUTH HALF OF THE AREA EXCEPT TO POSSIBLY KICK UP THE WINDS A
BIT.


&&

.AVIATION.../12Z ISSUANCE/

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

VFR CONDITIONS WILL PREVAIL THROUGH THE PERIOD. AN AREA OF FOG WAS
EXPANDING WESTWARD EARLY THIS MORNING BTWN DGW AND CPR WILL LIKELY
BE VCNTY KCPR 11Z-15Z. ISOLATED SHOWERS AND STORMS WILL OCCUR
FROM 20Z UNTIL 04Z FRIDAY IN THE ABSAROKA AND WIND RIVER
MOUNTAINS. A FEW OF THESE WILL DRIFT EAST INTO THE NEARBY
FOOTHILLS AND COULD IMPACT THE KLND AND KCOD AIRPORTS WITH A GUSTY
WIND AND BRIEF RAINFALL. ISOLATED SHOWERS AND STORMS WILL ALSO
OCCUR IN THE NORTHERN BIGHORN MOUNTAINS FROM 22Z UNTIL 06Z FRIDAY.


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

VFR CONDITIONS WILL PREVAIL THROUGH THE PERIOD. ISOLATED SHOWERS AND
STORMS WILL OCCUR OVER THE WESTERN MOUNTAINS AFTER 20Z AND CONTINUE
THROUGH 04Z FRIDAY. THE KJAC AIRPORT MAY BE IMPACTED BY THIS
ACTIVITY WITH A GUSTY WIND AND BRIEF RAINFALL.
&&

.FIRE WEATHER...

TODAY WILL BE A WARMER AND DRIER DAY ACROSS THE AREA AS A RIDGE OF
HIGH PRESSURE BUILDS INTO WYOMING. A WEAK UPPER LEVEL DISTURBANCE
WILL MOVE OVER THE TOP OF THE RIDGE AND MAY BRING ISOLATED
THUNDERSTORMS TO THE NORTHERN AND WESTERN MOUNTAINS BUT MOST PLACES
SHOULD BE DRY TODAY. RELATIVE HUMIDITY VALUES WILL BE LOWER TODAY
BUT SHOULD STILL REMAIN ABOVE CRITICAL LEVELS FOR MOST LOCATIONS.
HOT TEMPERATURES WILL RETURN FOR FRIDAY ALONG WITH GUSTY BREEZES IN
NORTHERN AND SOUTHERN ZONES. WITH LOW RELATIVE HUMIDITY THIS COULD
LEAD TO ELEVATED FIRE DANGER. ISOLATED THUNDERSTORMS ARE ONCE AGAIN
POSSIBLE ACROSS THE NORTHERN AND WESTERN MOUNTAINS.
&&

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

$$

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







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