Area Forecast Discussion
Issued by NWS Riverton, WY

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000
FXUS65 KRIW 262052
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
252 PM MDT TUE MAY 26 2015

.SHORT TERM...TONIGHT THROUGH WEDNESDAY

SLOW MOVING SHOWERS AND THUNDERSTORMS MOVING ACROSS SATURATED SOILS
HAVE PROMPTED THE ISSUANCE OF ANOTHER FLASH FLOOD WATCH FOR MANY OF
OUR EASTERN COUNTIES...NATRONA...EASTERN FREMONT...JOHNSON...
WASHAKIE...AND HOT SPRINGS COUNTIES INCLUDING WIND RIVER CANYON...
THE BIGHORNS AND CASPER MOUNTAIN.

THESE STORMS WILL LIKELY CARRY ON THROUGH THE NIGHT AS AN UPPER
LEVEL DISTURBANCE MOVES NORTHEAST ACROSS THE STATE AFTER
00Z...EXITING THE REGION BY 12Z. SOME STORMS COULD BE STRONG AS IT
MOVES ACROSS THE STATE WITH HAIL OVER ONE HALF INCH...LIGHTNING AND
HEAVY DOWNPOURS CAUSING PONDING OF LOW LYING AREAS AND POTENTIALLY
MORE FLOODING...ESPECIALLY BEFORE MIDNIGHT.

AN UPPER LEVEL LOW CURRENTLY OVER WASHINGTON STATE WILL DRIFT
SOUTHEAST THROUGH THE NIGHT AND INTO WEDNESDAY. SOME DRIER SOUTHWEST
FLOW AHEAD OF THIS SYSTEM WILL MOVE IN DURING THE DAY BUT IT WILL
NOT BE DRY ENOUGH TO PREVENT MORE THUNDERSTORMS OR REMOVE THE
FLOODING THREAT. IN ADDITION...THERE WILL BE DEEPER AND MORE
PRONOUNCED SHEAR THAT WILL LIKELY LEAD TO MORE ORGANIZED STORMS
CAPABLE OF PRODUCING MORE SIGNIFICANT HAIL...NEAR TO REACHING SEVERE
LIMITS IN SOME CASES. IN ADDITION...THE DRIER AIR AND INCREASED MID
LEVEL FLOW COULD ENCOURAGE SOME GUSTIER WINDS WITH THESE STORMS.
LATER IN THE DAY...A COLD FRONT WILL APPROACH FROM THE
NORTH...BRINGING A PUSH OF MORE MOIST AIR AND AN EXPECTED INCREASE
IN STORMS WITH HEAVY RAINFALL...HOWEVER THE STORMS WILL BE MOVING
ALONG A BIT BETTER...AT OVER 20 MPH IN MOST AREAS.

.LONG TERM...WEDNESDAY NIGHT THROUGH TUESDAY

THE WEAK UPPER LOW CURRENTLY OVER EASTERN WA...WILL CONTINUE ITS
EASTWARD TREK AND BE OVER SOUTHERN ID WEDNESDAY NIGHT THURSDAY
MORNING. CONVECTIVE ACTIVITY WILL BE WINDING DOWN ACROSS THE
AREA...WITH SOME LINGERING SHOWERS ACROSS WESTERN PORTIONS BY
SUNRISE THURSDAY. ANOTHER ROUND OF SHOWERS AND THUNDERSTORMS WILL
RETURN ACROSS THE AREA THURSDAY...AS THE LOW BEGINS TO MAKE ITS WAY
OVER WY. THE ASSOCIATED COLD FRONT WILL PUSH TO THE SOUTH AND EAST
DURING THE AFTERNOON...BEFORE BECOMING STATIONARY ACROSS THE I80
CORRIDOR THURSDAY NIGHT. THE STRONGER STORMS THURSDAY AFTERNOON
COULD DEVELOP OVER SOUTHERN JOHNSON AND NATRONA
COUNTIES.

BY FRIDAY...SURFACE FLOW BECOMES MORE NORTHERLY AS THE UPPER
LOW/TROUGH AXIS CONTINUES ITS SLOW EASTWARD TREK INTO THE NORTHERN
HIGH PLAINS. THIS...COUPLED WITH THE STATIONARY FRONT...WILL HELP
PRODUCE WIDESPREAD SHOWERS ACROSS THE AREA. HOWEVER...THE STRENGTH
OF THE STORMS WILL DIMINISH...AND REMAIN A HEAVY RAIN THREAT. BY
SATURDAY...A WEAK RIDGE BUILDS ACROSS THE REGION...WITH ONLY
ISOLATED TO SCATTERED AFTERNOON/EVENING SHOWERS/T-STORMS
POSSIBLE...MAINLY OVER THE HIGHER ELEVATIONS. TEMPERATURES WILL RISE
SLIGHTLY ABOVE NORMAL BY SUNDAY INTO MONDAY...WITH MOST LOCATIONS
REACHING THE WARMEST READINGS OF THE YEAR SO FAR.

BY MONDAY...THE NEXT STORM SYSTEM BEGINS TO MAKES ITS WAY ONSHORE
OVER THE PACIFIC NORTHWEST. AN EJECTING SHORTWAVE FROM IT...COUPLED
WITH DIFFLUENT SOUTHWEST FLOW WILL PRODUCE ANOTHER ROUND OF ISOLATED
TO SCATTERED SHOWERS AND THUNDERSTORMS ACROSS NORTHERN AND CENTRAL
PORTIONS. THIS PATTERN WILL RETURN ON TUESDAY...AS THE STORM SYSTEM
SLOWLY MAKES ITS WAY INLAND OVER EASTERN OR/NORTHERN
CA.

&&

.AVIATION.../00Z ISSUANCE/

AREA OF LOW PRESSURE WILL MOVE SLOWLY TOWARDS WYOMING THE NEXT FEW
DAYS. THIS WILL COMBINE WITH AN UNSTABLE ATMOSPHERE TO PRODUCE MAINLY
SCATTERED AFTERNOON AND EVENING THUNDERSTORMS BOTH WEST AND EAST OF
THE CONTINENTAL DIVIDE. OUTSIDE OF THE STORMS...VFR CONDITIONS CAN
BE EXPECTED ALONG ALL ROUTES. GUSTY SURFACE WIND CAN BE EXPECTED
NEAR ANY THUNDERSTORMS. CHANCES OF SHOWERS AND THUNDERSTORMS THEN
INCREASE LATER THURSDAY...AS THE MID/UPPER LEVEL LOW MOVES OVER
WYOMING. THIS RESULTS IN A GENERALLY CLOUDY SKY THROUGH THU NIGHT.

.FIRE WEATHER...

SHOWERS AND THUNDERSTORMS ARE POSSIBLE EACH AFTERNOON AND EVENING
WITH A GOOD CHANCE OF WETTING RAIN EACH DAY. THERE WILL BE A CHANCE
FOR DRIER AND WARMER WEATHER A DAY OR TWO THIS WEEKEND BUT THERE
IS ANOTHER STORMY PERIOD EXPECTED IMMEDIATELY FOLLOWING. SMOKE
DISPERSAL EACH DAY WILL BE GOOD TO EXCELLENT...EXCEPT FOR SHORT
PERIODS IN THE VERY EARLY MORNING HOURS.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
FLASH FLOOD WATCH UNTIL MIDNIGHT MDT TONIGHT
WYZ005>011-019-020-022.

&&

$$

SHORT TERM...ALLEN
LONG TERM...LAVOIE
AVIATION...KPL
FIRE WEATHER...ALLEN








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