Weather Service Report


811 
FXUS65 KRIW 251800
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1200 PM MDT MON MAY 25 2015

.SHORT TERM...TODAY THROUGH WEDNESDAY NIGHT

WV IMAGERY SHOWING EXPANDING LARGE TROF IN CONTROL OF THE WRN 2/3S 
OF THE CONUS WITH TWO CLOSED LOWS CIRCULATING WITHIN THE TROF...ONE 
OVR THE HIGH PLAINS INCLUDING WY...THE OTHER UPSTREAM AND OVR THE 
NWRN CONUS. SFC SHOWS WEAK P GRADS ACROSS THE WEST...WITH LOW P AND 
A WEAK COLD WELL FRONT OFF TO THE E AND SE OVR THE CENTRAL 
PLAINS...WHILE WEAK HIGH P HAS SPREAD ACROSS MT.   

MORNING RAIN AND SNOW SHOWERS IN ADDITION TO SOME PATCHY FOG WILL 
CONTINUE OVR MUCH OF THE FA E OF THE DIVIDE. THE UPR LVL SYSTEM 
PUSHES EWD INTO THE PLAINS WITH TRANSITIONAL SW RIDGING TAKING PLACE 
ACROSS THE WRN FA WHILE THE ERN PORTION OF THE FA WILL BE UNDER THE 
EXITING TROF INFLUENCE AND SOME RETURN VORTICITY ROTATING BACK OVR 
THE FA FROM OUT OF THE NE. SHOWER AND THUNDER ACTIVITY WILL REEMERGE 
BY THE AFTERNOON AS TEMPS WARM AND ATMOSPHERE BECOMES MORE UNSTABLE. 
CAPE OF 500 TO 1000 J/KG AND LOW SHEAR CHARACTERIZES THE MID/LATE 
AFTERNOON ATMOSPHERE. STORM MOVEMENT WILL BE ON THE SLOW SIDE AT 
LESS THAN 15 MPH...MUCH LIKE THE STORMS OF LATE LAST WEEK...ONLY 
STORM MOVEMENT WILL BE FROM NW TO SOUTHEAST GENERALLY. WILL CANCEL 
THE CURRENT FLASH FLOOD WATCH THIS MORNING AS PRECIPITATION RATES 
HAVE BECOME VERY LIGHT ACROSS MOST OF THE FA AND THE FLASHINESS IS 
GONE FOR NOW WITH ALL PAST FLASH FLOOD WARNINGS CONVERTED TO EITHER 
FLOOD WARNINGS OR ADVISORIES. MODERATE TO MAJOR FLOODING OCCURRING
NEAR SUSSEX WY ON THE POWDER RIVER. ANOTHER CERTAINLY HYDRO
SPECIFIC DAY...BUT ON A MORE SCATTERED BASIS AS CONVECTION BECOMES
LIKELY THIS AFTERNOON...SO A FLASH FLOOD WATCH MAY BE NECESSARY
ONCE AGAIN LATER TODAY AS CONVECTIVE COVERAGE BECOMES MORE
APPARENT. PWS WILL FALL SOME OVR WHAT THEY HAVE BEEN THE PAST
COUPLE OF DAYS...GENERALLY AOB 0.5 WEST OF THE DIVIDE...TO AROUND
0.75 ACROSS PORTIONS E OF THE DIVIDE. OTHER THAN A COUPLE OF
STRONGER CORES ABLE TO PRODUCE SMALL HAIL...SEVERE WX SHOULD BE
LIMITED...WITH SLOW MOVING OR TERRAIN TIED HEAVY RAIN PRODUCERS
THE MAIN THREAT.

SHOWERS MOSTLY END TONIGHT EXCEPT FOR SMALL CHANCES REMAINING 
PRIMARILY OVR THE MOUNTAINS AND YELLOWSTONE PARK AREA AS A SMALL UPR 
WAVE BRUSHES THE REGION. THRU THE DAY TUESDAY...INFLUENCES FROM THE 
UPSTREAM TROF/CLOSED LOW SYSTEM PUSHES THE SW RIDGE EAST...AND UPR 
SWRLY FLOW BEGINS TO OVERTAKE THE FA WHILE AN EMBEDDED SW MOVES 
ACROSS THE WRN FA IN THE AFTERNOON...HELPING TO INITIATE A NEW BATCH 
OF SHOWERS AND THUNDERSTORMS...ESPECIALLY W OF THE DIVIDE. MORE 
ISOLATED STORMS E OF THE DIVIDE...HOWEVER...MAY BE SOMEWHAT STRONGER 
LATER IN THE DAY...IF/WHEN THEY CAN GO...OFFERING UP HALF INCH OR 
GREATER SIZE HAIL. CONVECTION WILL DECREASE ONCE AGAIN 
OVERNIGHT...EXCEPT AGAIN OVR THE NW FA WHICH WILL BE POSITIONED BEST 
TO TAKE ADVANTAGE OF THE DYNAMICS AND TRAJECTORY OF THE APPROACHING 
TROF AND ITS MOISTURE. WED...POSITION OF THE APPROACHING UPR WAVE 
ALONG WITH LEE TROFFING/WEAK CYCLOGENESIS WILL DRYSLOT MUCH OF THE 
SW TO CNTRL FA...WITH SCATTERED TSRA WITH ADEQUATE CAPE AND SHEAR 
BREAKING OUT AROUND THIS AREA. CONVECTIVE INDICES WILL FAVOR SOME 
STORM ORGANIZATION WED...WITH STORMS ABLE TO ROTATE AND A FEW 
PRODUCING NEAR SEVERE HAIL..ESPECIALLY OVR THE BIGHORN BASIN AND ERN 
CWA. STORMS WILL ALSO MOVE AT A FASTER CLIP...25 TO 30 MPH AND 
HOPEFULLY WITH SOMEWHAT LESS POTENTIAL OF 
FLOODING.                   

.LONG TERM...THURSDAY THROUGH MONDAY

VERY BUSY NIGHT TONIGHT SO NOT A LOT OF TIME TO DELVE INTO THE 
EXTENDED DETAILS. STILL LOOKS LIKE ANOTHER UPPER LOW MOVING SLOWLY 
EAST ACROSS THE AREA THURSDAY INTO FRIDAY WITH A GOOD CHANCE OF MORE 
SHOWERS AND A FEW THUNDERSTORMS. A TRANSITORY RIDGE IS THEN 
EXPECTED OVER THE WEEKEND AND POSSIBLY THROUGH MONDAY WITH WARMER 
AND DRIER WEATHER. THERE IS A POTENTIAL SHORTWAVE THOUGHT THAT MOVES 
JUST TO OUR NORTH SUNDAY OR MONDAY WITH A BETTER SHOT OF 
SHOWERS/TSTMS FOR AT LEAST THE MOUNTAINS. MORE TIME TO LOOK AT ALL 
THIS TOMORROW NIGHT HOPEFULLY. 

.AVIATION.../18Z ISSUANCE/

AN UPPER LOW PRESSURE SYSTEM WILL CONTINUE TO SLOWLY MOVE EAST FROM 
SOUTHEAST WYOMING INTO WESTERN NEBRASKA TONIGHT. WRAPAROUND
PRECIPITATION WILL CONTINUE TO RESULT IN AREAS OF MVFR...LOCAL IFR
CIGS IN -RA VCNTY AND EAST OF THE DIVIDE AND ALONG THE INTERSTATE
80 CORRIDOR THROUGH 21Z. THESE CONDITIONS WILL BE MORE LOCALIZED
WEST OF THE DIVIDE WITH PATCHY FOG PARTIALLY OBSCURING TERRAIN
THROUGH 21Z.

CIGS WILL LIFT INTO PRIMARILY VFR CATEGORIES ACROSS THE AREA AFTER 
21Z MONDAY. THE BETTER INSTABILITY AND MOISTURE WILL BE FOUND
VCNTY AND WEST OF THE DIVIDE WHERE SCT -SHRA AND ISOLD -TSRA ARE
EXPECTED FROM 20Z MON-02Z TUE.

SKIES WILL PARTIALLY CLEAR MONDAY NIGHT WITH PATCHY FOG PARTIALLY 
OBSCURING TERRAIN ACROSS THE AREA EARLY TUESDAY MORNING.

.FIRE WEATHER...

FIRE DANGER LOW AND WILL REMAIN LOW THROUGH MOST OF 
THE WORK WEEK. SEASONALLY COOL TO WARM TEMPERATURES WILL COMBINE 
WITH RELATIVELY MOIST ATMOSPHERIC CONDITIONS TO PRODUCE DECENT 
CHANCES FOR SHOWERS AND THUNDERSTORMS EACH AFTERNOON AND EVENING.

&&

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

$$

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




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