Area Forecast Discussion
Issued by NWS Riverton, WY

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000
FXUS65 KRIW 050941
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
341 AM MDT WED AUG 5 2015

.SHORT TERM...TODAY THROUGH FRIDAY NIGHT

ANOTHER EAST BOUND UPPER LEVEL DISTURBANCE WILL BE FOLLOWING
CLOSE BEHIND TUESDAY EVENINGS WEATHER SYSTEM THIS MORNING. THIS
NEXT WEATHER FEATURE IS ALREADY SPREADING LIGHT SHOWERS INTO FAR
WESTERN WY. THIS ACTIVITY WILL INCREASE THROUGH THE LATE MORNING
HOURS AS MOISTURE AND INSTABILITY INCREASE WITH THE PASSAGE OF
THIS SHORTWAVE. A STRONGER SHORTWAVE TROUGH THAT JUST MADE
LANDFALL ONTO THE PACIFIC COAST WILL CONTINUE TO INCREASE THE
COVERAGE OF SHOWERS AND THUNDERSTORMS TO WESTERN WYOMING WITH
NUMEROUS CONVECTIVE ACTIVITY EXPECTED TO LAST THROUGH THE EVENING
HOURS THERE. MUCH OF THIS CONVECTIVE ACTIVITY WILL SPREAD INTO
AREAS EAST OF THE DIVIDE LATER TODAY. EXPECT LIKELY POPS FAR WEST
AND A GOOD CHANCE OF SHOWERS ELSEWHERE. LOCALLY HEAVY
RAINFALL...SMALL HAIL...GUSTY WINDS AND FREQUENT LIGHTNING WILL BE
THE MAIN THREATS...ESPECIALLY ACROSS THE NORTH HALF OF THE CWA. A
FEW SHOWERS WILL LINGER IN THE FAR NORTH AFTER MIDNIGHT TONIGHT.
DRY SOUTHWEST WINDS WILL INCREASE AHEAD OF THE ASCT PACIFIC COOL
FRONT TODAY WITH A WIND SHIFT EXPECTED WITH THE FRONT. NW TO N
WINDS WILL CONTINUE FOR A FEW HOURS AFTER THE FROPA THIS
EVENING...ESPECIALLY EAST OF THE DIVIDE WHERE THREE HOURLY POST
FRONTAL SURFACE PRESSURE RISES OF 7MB ARE EXPECTED.

DRIER AIR WILL FILTER INTO THE AREA THURSDAY ALONG WITH SLIGHTLY
COOLER AIR.

THEN ISOLATED LATE DAY T STORMS ARE EXPECTED AGAIN FRIDAY AS A
CLOSED LOW TRAVELING NORTHEAST ACROSS SOUTHERN CANADA DRAGS A
SHORTWAVE EAST ACROSS THE NORTHERN ROCKIES AND GIVES OUR CWA A
GLANCING BLOW.

ON FRIDAY NIGHT...A MORE PROMINENT SHORTWAVE WILL INCREASE
CONVECTIVE ACTIVITY ACROSS THE FAR WEST.




.LONG TERM...SATURDAY THROUGH WEDNESDAY

NOT A LOT OF CHANGE IN THE MEDIUM RANGE THINKING SINCE LAST NIGHT.
CURRENT UPPER CIRCULATION OFF THE CA COAST OUT NEAR 34N/136W IS
STILL FORECAST TO MOVE INLAND ON FRIDAY AND THEN GET IN THE SW FLOW
AROUND THE TX/OK UPPER HIGH AND MOVE INTO WRN WYO LATE SATURDAY.
SCATTERED TSTMS ARE A GOOD BET ALONG ITS PATH WITH A FEW STRONGER
STORMS EXPECTED. SOME GUSTY WINDS...VERY WARM TEMPS AND POSSIBLY
DRIER STORMS AROUND THE EDGES WILL LIKELY LEAD TO INCREASED FIRE
DANGER. LINGERING MOISTURE/INSTABILITY ACROSS THE NORTH SUNDAY WILL
KEEP SOME SHOWERS/TSTMS GOING UP THERE BEFORE WE DRY OUT FOR EARLY
NEXT WEEK. AS MENTIONED YESTERDAY...THERE IS SOME INDICATION OF A
WEAK INITIAL MONSOON SURGE...AT LEAST IN THE MID LEVELS...MOVING UP
ON TUESDAY LEADING TO AT LEAST A FEW SHOWERS/TSTMS IN THE MTNS AND
SW WHICH COULD INCREASE ON WEDNESDAY. THE ECMWF KEEPS THE HIGH
FAIRLY STATIONARY OVER NRN TX WITH A STRONGER TROUGH ALONG THE CA
COAST TUE INTO WED WITH SOME MOISTURE SPREADING NWD. THE GFS EXPANDS
THE HIGH TO THE IDEAL 4-CORNERS REGION BUT THE MOISTURE SURGE IS
STILL LIMITED. WE WILL STILL NEED TO WATCH THIS PATTERN CLOSELY TO
SEE IF THIS ENDS UP BEING A SIGNIFICANT MONSOONAL SURGE TUESDAY INTO
WEDNESDAY OF NEXT WEEK OR JUST ENOUGH TO GET A FEW STORMS GOING.

&&

.AVIATION.../12Z ISSUANCE/

ISOLATED SHOWERS AND STORMS WILL OCCUR OVER NW WY THROUGH 18Z. A
WEATHER SYSTEM WILL MOVE TOWARD WY THIS AFTERNOON AND ACROSS
NORTHERN WY TONIGHT. NEW SHOWERS AND STORMS WILL FORM OVER WESTERN
WY AROUND 18Z AND THIS ACTIVITY WILL MOVE EAST DURING THE AFTERNOON
AND EVENING HOURS. EXPECT LOCAL MVFR CONDITIONS IN HEAVY RAIN.
MOUNTAINS WILL BE OBSCURED AT TIMES. A COLD FRONT WILL PUSH THROUGH
WY FROM 00Z TO 06Z THURS WITH A WIND SHIFT TO THE NORTH OR
NORTHWEST. SHOWERS AND STORMS WILL DECREASE BY 06Z ACROSS THE REGION.

&&

.FIRE WEATHER...

SHOWERS AND THUNDERSTORMS WILL INCREASE IN WESTERN WYOMING THROUGH
THE MORNING HOURS TODAY AS ANOTHER EAST BOUND UPPER LEVEL
DISTURBANCE FOLLOWS CLOSELY BEHIND TUESDAY EVENINGS WEATHER
SYSTEM...BEFORE SPREADING EAST OF THE DIVIDE BY EARLY TO MID
AFTERNOON. GUSTY WINDS AND LIGHTNING WILL BE THE MAIN THREATS FROM
THIS ACTIVITY. WINDS WILL ALSO INCREASE OUT OF THE SOUTHWEST
ACROSS THE SOUTHERN AND SOUTHWESTERN ZONES. DRY WEATHER RETURNS
THURSDAY...WITH GUSTY WEST WIND ACROSS THE SOUTHERN ZONES ALLOWING
FOR ENHANCED FIRE DANGER.

&&

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

$$

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


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