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000
FXUS65 KRIW 202109
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
309 PM MDT MON MAY 20 2013

.SHORT TERM...TONIGHT THROUGH TUESDAY

TODAY...LARGE STUCK...STACKED...CLOSED LOW OVER THE DAKOTAS
TODAY...NOT GOING ANYWHERE IN A HURRY.  THIS WAVE WILL BEGIN TO OPEN
AND MOVE TUESDAY AS ANOTHER LARGE ALASKAN SYSTEM PLUNGES INTO THE
PAC NW BY TUESDAY NIGHT. IN THE MEANTIME...LOW CLOUDS...SCATTERED
RAIN AND SNOW SHOWERS (ABOVE 8500 FT) WHILE SFC LOW DEVELOPS OVER
WRN CWA AND COLD AIR CONTINUES TO POUR IN ALOFT. MAIN THREAT TODAY
WILL BE STRONG WINDS AROUND MOST THE EASTERN CWA WITH NICE LOW LEVEL
PRESSURE GRADIENT SET UP THIS THIS MORNING...TOGETHER WITH VIGOROUS
NEARLY UNIDIRECTIONAL FLOW ALOFT...GIVING NEAR HIGH WIND CATEGORY FOR
ELEVATIONS ABOVE 7000 FT IN THE OWL CREEK...BRIDGER...AND BIG HORN
MOUNTAINS. SUSTAINED NORTHERLY WINDS OF 40 TO 45 MPH ARE COMMON WITH
OCCASIONAL GUSTS TO 60 MPH ACROSS ELEVATED AREAS. THESE WILL PERSIST
THROUGH AT LEAST LATE AFTERNOON BEFORE QUIETING DOWN EAST OF THE
DIVIDE WITH THE RELAXATION OF THE LL PRESSURE GRADIENT. ACROSS THE
SOUTHERN BIG HORN BASIN AND OWL CREEK/BRIDGER MOUNTAINS...THE STRONG
WIND WILL LIKELY PERSIST A LITTLE LONGER INTO THE EVENING.
SECONDARY THREAT WILL A MORE PERSISTENT PRECIPITATION SHIELD OVER
THE BIG HORN MOUNTAINS AND PORTIONS OF ADJACENT EASTERN COUNTIES
INCLUDING JOHNSON AND NATRONA...AND SECONDLY ALONG AND NEAR THE WIND
RIVER AND ABSORKA MOUNTAINS...PARTICULARLY THE MOUNTAINS THAT HAVE
GOOD NORTHERN EXPOSURE AND WILL TAKE ADVANTAGE OF THE UPSLOPE ALONG
WITH THE REGION SOUTH OF THE WIND RIVER MOUNTAINS WHERE LL
CONVERGENCE AND MODERATE MID AND UPPER LAPSE RATES WILL BE MAXIMIZED.

TONIGHT AND TUESDAY...PRECIP CHANCES WILL BEGIN TO WANE COMPARED TO
THE LAST FEW DAYS AND THE STRONGER WINDS WILL SUBSIDE AS THE CLOSED
LOW TO OUT EAST STARTS TO OPEN AND SLOWLY MIGRATE EASTWARD AND
SURFACE HIGH PRESSURE ALSO BEGINS TO DEVELOP OVER OUR HEADS.  WE
WILL THEN GET SOME NEEDED MILD RIDGING BUILDING IN AHEAD OF THE NEXT
BIG SYSTEM...CURRENTLY LOCATED IN THE ALASKAN/SRN YUKON AREA IN WV
IMAGERY. DRYING...WARMING OF 5 TO 8 DEG OVER TODAY...AND MORE IN THE
WAY OF SUNSHINE WILL BE THE NAME OF THE GAME TOMORROW. THERE WILL BE
SOME MILD THERMAL INSTABILITY WITH INCREASING LAPSE RATES BUT
WORKING POTENTIAL ENERGY THROUGH THE DAY WILL BE MISSING AS
COMBINATION OF OVERALL DRYING AND UPPER LEVEL SHEAR DYNAMICS ON THE
WEAK SIDE (SUBSTENANCE THE GENERAL RULE)...ONLY ISOLATED ELEVATED
CONVECTION OCCURRING OVER THE HIGHEST AREAS OF THE WIND
RIVER...ABSOROKAS AND BIG HORN MOUNTAINS WILL BE POSSIBLE.

.LONG TERM...TUESDAY NIGHT THROUGH THURSDAY

CONVECTION WILL LINGER OVER THE FAR WEST MOUNTAINS INTO TUESDAY
EVENING AS A WEAK SHORTWAVE RIPPLES NE ACROSS THE AREA. A
POTENTIALLY MORE INTERESTING SCENARIO SETS UP ON WEDNESDAY OVER
MAINLY THE NW THIRD OR SO. A SURFACE HIGH DEVELOPS BEHIND OUR UPPER
LOW AND PUSHES A GENTLE BOUNDARY SOUTH AND THEN WWD ACROSS AREAS
EAST OF THE DIVIDE TUESDAY NIGHT. A DRIER S TO SW FLOW OVER THE SRN
THIRD WILL PUSH NWD DURING THE DAY ALONG WITH A POTENTIAL WEAK
SHORTWAVE COMING UP FROM THE SSW. LOWERING PRESSURES OVER THE NRN
GREAT BASIN WILL ALSO HELP TO DRAW SOME OF THIS MOISTURE WWD. THE NW
MTNS WILL BE THE MOST FAVORED FOR STRONGER CONVECTION BUT WITH THE
SW STEERING FLOW ALOFT SOME STORMS MAY FORM OVER THE MTNS AND DRIFT
NE ACROSS THE FOOTHILLS AND POTENTIALLY PARTS OF THE CENTRAL BASINS
LATE IN THE DAY WEDNESDAY. INDICATED SOME HAIL AND GUSTY WIND
WORDING IN THE STORMS FOR THIS AREA FROM ABOUT LANDER AND RIVERTON
NORTH TO CODY AND THEN WWD THROUGH THE NW MTNS. ON THURSDAY...THE
DRIER AIR WILL LIKELY MIX OUT FURTHER NORTH WITH THE
BOUNDARY/CONVERGENCE RETREATING TO THE FAR NRN AND NERN SECTIONS
WHERE A FEW STRONGER STORMS MAY STILL FIRE. TEMPERATURES WILL BE
WARMING AS THIS WARMER...DRIER AIR MOVES NWD WEDNESDAY INTO THURSDAY.

THURSDAY NIGHT THROUGH MONDAY

A STRONGER SHORTWAVE IS EXPECTED TO ROTATE AROUND OUR LARGE PACNW
AND NRN GREAT BASIN UPPER LOW THURSDAY NIGHT WHICH WILL PUSH A COOL
FRONT MUCH OF THE AREA WITH THE BIGGEST COOL DOWN FRIDAY IN THE
CENTRAL AND WRN ZONES. STILL MILD BUT NOT AS WARM AS THURSDAY.
ISOLATED THUNDERSTORMS MAY STILL FIRE ACROSS THE FAR NORTH WHERE
TROUGH DYNAMICS AND DAYTIME HEATING CREATE ENOUGH INSTABILITY AND
LIFT. THURSDAY NIGHT WILL BE A MILD NIGHT AS THIS BOUNDARY LIFTS
NORTH AND A GUSTY SOUTH TO SOUTHWEST WIND BLOWS IN MANY AREAS
OVERNIGHT. MODELS ARE KEEPING A FAIRLY DRY AIRMASS OVER THE AREA ON
SATURDAY BUT WITH MOIST GROUND AND DAYTIME HEATING WILL KEEP
ISOLATED THUNDERSTORMS GOING ACROSS THE NORTH THIRD TO HALF. ON
SUNDAY...THE UPPER LOW REDEVELOPS FURTHER SOUTH INTO THE GREAT BASIN
AGAIN AS A STRONG SHORTWAVE DROPS SE BEHIND THE OLD LOW. STRONG
DYNAMICS WILL LIKELY ROTATE NW ACROSS THE AREA ON SUNDAY WITH AN
INCREASING CHANCE OF THUNDERSTORMS. A VERY MOIST AIRMASS WILL BE
JUST TO THE EAST OF US LATE IN THE WEEKEND AND IF SOME OF THIS GETS
DRAWN JUST A LITTLE FURTHER WWD...SOME STRONG STORMS MAY FIRE IN THE
ERN ZONES. OUT WEST...THERE WILL BE LESS MOISTURE BUT STRONGER
DYNAMICS FROM THE SHORTWAVE ROTATING NWD ACROSS THE WEST. WILL
INDICATE SCATTERED THUNDERSTORMS OVER THE ABSAROKAS WITH ISOLATED
STORMS ACROSS MOST OF THE NW AND NERN ZONES. PLENTY OF SHORTWAVES IN
THE SW FLOW ON MEMORIAL DAY WITH THE POTENTIAL FOR THUNDERSTORMS
CONTINUING ACROSS AT LEAST THE NRN MOUNTAINS AND POTENTIALLY
ELSEWHERE EVEN THOUGH THE MODELS ARE SHOWING STORMS MAINLY CONFINED
TO THE NRN MOUNTAINS. EACH DAY WILL HAVE TO BE WATCHED CLOSELY AS
WITH MOIST GROUND AND DAY TIME HEATING WILL LIKELY CREATE MORE
INSTABILITY THAN THE MODELS ARE SHOWING RIGHT NOW.


&&

.AVIATION.../00Z ISSUANCE/

ISOLATED TO SCATTERED LIGHT RAIN SHOWERS CONTINUES TODAY ACROSS MUCH
OF THE REGION THROUGH THE MID EVENING PERIODS...AND PERHAPS A TIL
AROUND 06Z NEAR KRKS. SHOWER CONDITIONS WILL KEEP MVFR CONDITIONS
AROUND AS WELL. GUSTY WIND WILL OCCUR AT MANY TERMINAL SITES
THROUGH THIS EVENING WITH THE WIND DECREASING MOST TERMINALS AFTER
03Z THIS EVENING. BEST AREA FOR WIND TODAY WILL OCCUR IN THE
CORRIDOR BETWEEN KRIV AND KWRL WITH GUSTS TO 60 KT POSSIBLE ABOVE
7000 FT MSL. VFR CONDITIONS WILL THEN PREVAIL AFTER 06Z TUE
ALTHOUGH ISOLATED SHOWERS BE A VERY SLIGHT POSSIBILITY OVER THE
HIGHEST ELEVATIONS ON TUESDAY.

&&

.FIRE WEATHER...
THE BACK END OF A COOL AND WET STORM SYSTEM WILL CONTINUE TO IMPACT
THE AREA THROUGH THIS EVENING BEFORE IMPROVING CONDITIONS RETURN
TONIGHT AND THROUGH TUESDAY. ISOLATED SHOWERS WEST OF THE DIVIDE
MOST AREAS WILL PRODUCE OFF AND ON LIGHT RAIN WITH HIGH ELEVATION
SNOW (ABOVE 8500 FT) THROUGH THIS EVENING ALONG WITH PERIODS OF
GUSTY NORTH TO NORTHWEST WINDS RUNNING 30 TO 40 MPH ABOVE 7000 FT.
ANOTHER STORM SYSTEM WILL BRING A CHANCE OF THUNDERSTORMS TO THE
NORTHWEST FIRE ZONES ON WEDNESDAY WITH GUSTY SOUTH TO SOUTHEAST
WINDS ACROSS THE AREA.

&&

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

$$

SHORT TERM...BRAUN
LONG TERM...SKRBAC
AVIATION...BRAUN
FIRE WEATHER...BRAUN