858 FXUS65 KCYS 210856 AFDCYS AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE CHEYENNE WY 256 AM MDT SUN JUL 21 2013 .SHORT TERM...(TODAY THROUGH TUESDAY) ISSUED AT 300 AM MDT SUN JUL 21 2013 FORECAST CHALLENGES DEAL WITH SEVERE CONVECTIVE POTENTIAL/LOCATIONS EAST AND FIRE WEATHER POSSIBILITIES WEST TODAY. CURRENTLY...HAVE A FRONTAL BOUNDARY EXTENDING FROM CENTRAL MONTANA...SOUTH THROUGH CASPER AND THEN DOWN TO AROUND DENVER THIS MORNING. THIS BOUNDARY IS SEPARATING VERY DRY AIR TO THE WEST FROM MORE MOIST AND UNSTABLE AIR EAST OF THE LARAMIE RANGE THIS MORNING. DEWPOINTS OUT OVER SOUTHWESTERN WYOMING IN THE 20S WHILE UPPER 50S RESIDE IN THE PANHANDLE. TO OUR SOUTHWEST...OVER THE CALIFORNIA BAJA...A LOW PRESSURE SYSTEM RESIDES WITH SIGNIFICANT MONSOON MOISTURE OVER ARIZONA AND NEW MEXICO. THE MONSOON MOISTURE THAT HAS BEEN OVER OUR AREA THE PAST FEW DAYS HAS BEEN SHUNTED SOUTH TO CENTRAL COLORADO. THINK FOR THE MOST PART TODAY...SOUTHEAST WYOMING IS GOING TO BE DRY WITH THE MONSOON MOISTURE OVER COLORADO. THE PANHANDLE IS ANOTHER STORY THOUGH. BY THIS AFTERNOON...THE FRONTAL BOUNDARY LOOKS TO HAVE MOVED INTO THE PANHANDLE WITH DRY WEST WINDS WEST OF THE BOUNDARY HERE OVER SOUTHEAST WYOMING AND MOIST SOUTHEAST WINDS IN THE PANHANDLE EAST OF THE BOUNDARY. STILL WILL BE UNSTABLE OUT THERE THIS AFTERNOON WITH THE NAM SHOWING 1000-1500 J/KG CAPES. SO DO THINK WE WILL SEE ONE MORE DAY OF POSSIBLE SEVERE CONVECTION IN THE PANHANDLE TODAY. THOUGH THE STORM PREDICTION CENTER HAS THE ENTIRE PANHANDLE IN A SLIGHT RISK AREA TODAY...DO BELIEVE THE SEVERE CONVECTION WILL BE MOST LIKELY THE NORTHERN HALF OF THE PANHANDLE...SAY FROM ALLIANCE TO POSSIBLY LUSK. PRECIP QUICKLY ENDS THIS EVENING WITH LOSS OF DAYTIME HEATING AND DRIER AIR MOVING IN BEHIND THAT BOUNDARY. FOR MONDAY...WE STAY IN A DRY WEST TO NORTHWEST FLOW. HAVE A SHORTWAVE TRACKING ACROSS MONTANA MONDAY AFTERNOON. SOUNDINGS FOR MONDAY SHOWING US POSSIBLY MIXING UP TO 500MBS WITH PWS DOWN AROUND .2 TO .3 INCHES ACROSS MUCH OF SOUTHEAST WYOMING. GOING TO BE A BREEZY DAY WITH GUSTS TO 30-35 MPH POSSIBLE. BY MONDAY NIGHT...WINDS BEGIN TO SHIFT TO THE EAST ONCE AGAIN BEHIND THE SHORTWAVE. START TO GET SOME MOISTURE RETURN TO THE PANHANDLE...SO COULD SEE SOME AFTERNOON CONVECTION OUT THERE. ADDED SOME SLIGHT CHANCE POPS FOR THE NORTHERN PANHANDLE TUESDAY AFTERNOON. .LONG TERM...(TUESDAY NIGHT THROUGH SATURDAY) ISSUED AT 243 AM MDT SUN JUL 21 2013 LONG RANGE MODELS IN GOOD AGREEMENT...SHOWING A RETURN OF THE MONSOON FLOW AND SUBTROPICAL MOISTURE TO THE FORECAST AREA BY LATE THIS WEEK. FOR WEDNESDAY...MODELS SHOW THE UPPER LEVEL HIGH...WHICH WAS CENTERED NEAR CENTRAL COLORADO ON TUESDAY...DRIFTING TO THE SOUTH AND WEAKENING. MODELS NOW SHOWING THE POTENTIAL FOR A HIGHER COVERAGE OF THUNDERSTORMS FOR WEDNESDAY COMPARED TO PREVIOUS RUNS AS THE FLOW ALOFT BECOMES WESTERLY AND THE UPPER LEVEL HIGH WEAKENS A BIT FASTER COMPARED TO YESTERDAY. MODEL SOUNDINGS INDICATE CAPE VALUES AROUND 2000 J/KG WITH GOOD LLVL INSTABILITY. THE ONLY LIMITING FACTOR WILL BE DRY AIR ALOFT...RESULTING IN DRY AIR ENTRAINMENT ABOVE 10K FEET AGL. MODELS SHOW THIS DRY LAYER ERODING DURING THE DAY...SO INCREASED POP BETWEEN 20 TO 30 PERCENT HIGHEST ALONG THE LARAMIE RANGE. EXPECT CONVECTION TO INITIATE ALONG THE LARAMIE RANGE AND THE SNOWY RANGE...AND THEN EVENTUALLY PUSH EASTWARD ACROSS THE HIGH PLAINS DURING THE AFTERNOON. WESTERN NEBRASKA MAY NOT SEE ANY TSTORMS UNTIL WEDNESDAY EVENING. THURSDAY APPEARS TO BE THE DAY TO WATCH IN THE LONG TERM. MODELS SHOW THE UPPER LEVEL HIGH BUILDING WESTWARD ACROSS THE GREAT BASIN REGION...ALLOWING A VIGOROUS OPEN WAVE TROUGH TO DIG SOUTHWARD AROUND THE NORTHEAST QUADRANT OF THE UPPER HIGH. AMPLE SUBTROPICAL MOISTURE WITH PW/S OVER 1 INCH WILL INTERACT WITH SURFACE CONVERGENCE AND A VERY UNSTABLE BOUNDARY LAYER TO PRODUCE SCATTERED/NUMEROUS SHOWERS AND TSTORMS THURSDAY THROUGH THURSDAY NIGHT. THIS ACTIVITY WILL LIKELY LINGER ALL NIGHT LONG THROUGH FRIDAY MORNING. FRIDAY WILL BE SIMILAR WITH MORE IN THE WAY OF MODERATE TO HEAVY SHOWERS INSTEAD OF WIDESPREAD TSTORMS. DUE TO HIGHER CONFIDENCE...INCREASED POP BETWEEN 30 TO 50 PERCENT ACROSS THE WHOLE AREA AND WILL LIKELY INCREASE PROBABILITIES FURTHER IF MODEL TRENDS CONTINUE. WILL HAVE TO WATCH THE POTENTIAL FOR FLASH FLOODING DUE TO SLOW STORM MOTION. HIGH TEMPERATURES WILL LIKELY BE BELOW NORMAL EACH DAY WITH HIGHS IN THE 70S TO LOW 80S POSSIBLE DUE TO CLOUD COVER AND PRECIP. ALTHOUGH THE PATTERN IS NOT EXPECTED TO CHANGE MUCH NEXT WEEKEND...THE COVERAGE OF SHOWERS AND TSTORMS MAY NOT BE AS HIGH ON SATURDAY DUE TO THICK CLOUD COVER...LIMITING WIDESPREAD DEEP CONVECTION IN THE THE AFTERNOON. COOL TEMPERATURES WILL LINGER INTO NEXT WEEK. && .AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SUNDAY NIGHT) ISSUED AT 1138 PM MDT SAT JUL 20 2013 STORMS HAVE CLEARED THE FORECAST AREA THIS EVENING...ALTHOUGH SOME REDEVELOPMENT ACROSS CENTRAL WYOMING AND SOUTHWEST SOUTH DAKOTA COULD MOVE SOUTHEAST ACROSS NORTHERN PORTIONS OF THE CWA OVERNIGHT. INCLUDED IMPACT FROM SHOWERS AND STORMS AT KAIA...KCDR AND KBFF WITH SCT LOWER CIGS POSSIBLE IN THE WAKE OF THIS ACTIVITY THROUGH THE EARLY MORNING. SOUTHERLY FLOW UP THE CHEYENNE RIDGE COULD ALSO BRING LOW CIGS TO KCYS LATE TONIGHT...BUT WILL QUICKLY DISSIPATE AS WINDS SHIFT TO A DOWNSLOPE COMPONENT THROUGH THE EARLY MORNING. A SCATTERED COVERAGE OF THUNDERSTORMS CAN THEN BE EXPECTED OVER EASTERN PORTIONS OF THE CWA SUNDAY AFTERNOON AND EVENING WITH MVFR CIGS AND VSBYS POSSIBLE. VFR CONDITIONS WILL OCCUR ELSEWHERE THROUGH TOMORROW. && .FIRE WEATHER... ISSUED AT 300 AM MDT SUN JUL 21 2013 HOT AND DRY WEATHER EXPECTED FOR CARBON COUNTY TODAY WHILE AREAS EAST OF THE LARAMIE RANGE STILL STAND A CHANCE OF SEEING A FEW MORE WETTING RAINS THIS AFTERNOON. OUT WEST IN CARBON COUNTY...FORECAST SOUNDINGS SHOWING THE POSSIBILITY OF MIXING WINDS DOWN FROM 18K FEET IN A VERY DRY AIRMASS. BOTH THE NAM AND GFS SOUNDINGS SHOWING AT LEAST 25KTS AT THAT LEVEL...NAM SHOWING 30KTS. AFTERNOON HUMIDITIES EXPECTED TO FALL INTO THE UPPER SINGLE DIGITS OUT THAT WAY TODAY. WENT AHEAD WITH A RED FLAG WARNING FOR ZONES 303-307 TODAY. CONDITIONS SIMILAR FOR MONDAY AS A DISTURBANCE MOVES THROUGH MONTANA. WINDS SHOULD BE A LITTLE STRONGER OUT THERE IN CARBON COUNTY. SO WILL ISSUE A FIRE WEATHER WATCH FOR THE SAME ZONES FOR MONDAY. && .CYS WATCHES/WARNINGS/ADVISORIES... WY...RED FLAG WARNING FROM NOON TODAY TO 6 PM MDT THIS EVENING FOR WYZ303>307. FIRE WEATHER WATCH FROM MONDAY MORNING THROUGH MONDAY AFTERNOON FOR WYZ303>307. NE...NONE. && $$ SHORT TERM...CLAYCOMB LONG TERM...TJT AVIATION...TJT FIRE WEATHER...CLAYCOMB