Expires:No;;435273 FXUS65 KCYS 201727 AFDCYS AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE CHEYENNE WY 1127 AM MDT MON MAY 20 2013 .UPDATE... ISSUED AT 1125 AM MDT MON MAY 20 2013 ADJUSTED TODAYS GRIDS TO BUMP UP WINDS SLIGHTLY ALONG AND EAST OF THE LARAMIE RANGE. A FEW WIND GUSTS APPROACHING HIGH WIND WARNING CRITERIA. DO NOT THINK A WARNING WILL BE NEEDED BUT CONVECTIVE RAIN SHOWERS COULD PRODUCE A FEW GUSTS AROUND 60 MPH. WINDS WILL DROP SUBSTANTIALLY THIS EVENING. DRY DOWNSLOPE FLOW APPEARS TO BE LIMITED PRECIPITATION OVER WESTERN AND SOUTHERN PORTIONS OF THE FORECAST AREA THIS MORNING AND LATEST COMPUTER MODELS AREA SHOWING LESS QPF OVER THESE AREA TODAY AND TONIGHT. ADJUSTED POPS TO REFLECT LATEST PRECIPITATION CHANCES...LOWERING POPS SOUTH AND WEST. UPDATE ISSUED AT 918 AM MDT MON MAY 20 2013 FORECAST LOOKS TO BE IN GOOD SHAPE THIS MORNING. NOT EXPECTING ANY UPDATES AT THIS TIME. WIND ADVISORY IS WORKING OUT WITH MANY SITES IN THE NEBRASKA PANHANDLE SUSTAINED AROUND 30 MPH AND GUSTING OVER 40 MPH. THIS WILL BE THE CASE THROUGH THE AFTERNOON WITH WINDS BACKING DOWN THIS EVENING. GUSTY WINDS WILL ALSO BE FOUND ACROSS MUCH OF SOUTHEAST WYOMING. SNOW ADVISORY FOR THE SNOWY AND SIERRA MADRE RANGES MARGINAL BUT BEING A LATE SEASON EVENT WILL LET IT RIDE AT LEAST A FEW MORE HOURS. SNOW SHOULD REALLY SHUT DOWN THIS AFTERNOON AS DRIER AIR WORKS INTO THE WESTERN CWA. && .SHORT TERM...(TODAY THU AND TONIGHT) ISSUED AT 411 AM MDT MON MAY 20 2013 THE MAIN CONCERN WITH THIS PORTION OF THE FORECAST PACKAGE IS THE TIMING OF WHEN THE PRECIPITATION BANDS WILL MOVE THROUGH THE AREA TODAY AND TONIGHT. TODAY: LATEST WATER VAPOR LOOP WAS SHOWING A PIECE OF ENERGY ROTATING AROUND THE UPPER LEVEL LOW AND STARTING TO MOVE TOWARDS THE NORTHERN HALF OF THE FORECAST AREA. LATEST OBSERVATIONS WERE SHOWING GOOD PRESSURE FALLS TAKING PLACE ACROSS WESTERN SOUTH DAKOTA WITH THE RADAR RETURNS INCREASING ACROSS EXTREME NORTHEAST WYOMING AND WESTERN SOUTH DAKOTA. THE MODELS ARE IN PRETTY GOOD AGREEMENT IN SHOWING THIS BAND OF PRECIPITATION SHIFTING SOUTH THROUGH THE FORECAST AREA THROUGH THE MORNING AND REACHING AREAS NEAR THE CO/WY AND CO/NE BORDER AROUND MIDDAY. BEHIND THIS BAND OF PRECIPITATION...WE MAY SEE A BREAK FOR A FEW HOURS. HOWEVER...THE MOUNTAINS/RIDGE TOPS MAY ALSO INDUCE SOME AFTERNOON CONVECTION WHICH MAY AFFECT PORTIONS OF THE AREA. IN ADDITION...WE ARE EXPECTING GOOD MIXING TO TAKE PLACE TODAY ESPECIALLY IN THE PRECIPITATION FREE AREAS. AT THIS POINT...IT APPEARS LIKE AREAS EAST OF THE LARAMIE RANGE WILL MOST LIKELY EXPERIENCE THE STRONGER WIND SPEEDS WITH SUSTAINED VALUES OF 25 TO 30 MPH WITH HIGHER GUSTS TO 45 MPH POSSIBLE. THEREFORE...THE WIND ADVISORY LOOKS TO BE A GOOD CALL FOR THE NEBRASKA PANHANDLE. TONIGHT: NOT COMPLETELY CONFIDENT ON HOW THINGS WILL PAN OUT. THE MODELS ARE REALLY NOT SHOWING ANY DISTINCT DISTURBANCES MOVING THROUGH EASTERN WYOMING. HOWEVER...THERE IS SOME INDICATION THAT A PIECE OF ENERGY MAY TRY TO PIVOT THROUGH THE NEBRASKA PANHANDLE. THIS WILL BE A TOUGH CALL ON WHO WILL RECEIVE THE MAJORITY OF THE PRECIPITATION. AT THIS JUNCTURE...WE WOULD VENTURE TO SAY THE NORTHERN NEBRASKA PANHANDLE WILL SEE THE MAJORITY OF THE RAINFALL. HOWEVER...IF THERE IS ENOUGH UPPER LEVEL DIFFLUENCE SOUTHEAST WYOMING MAY SEE A DECENT CHANCE OF MORE RAINFALL. WE WILL PLAY THE CONSERVATIVE ROUTE FOR NOW WITH PRECIPITATION CHANCES BEYOND 00Z. SNOW CHANCES WILL ALSO PERSIST OVER THE MOUNTAINS WITH TOTAL SNOW ACCUMULATION POSSIBLY REACHING THE 4-7 INCH RANGE BEFORE DIMINISHING LATE. TUESDAY: THE MODELS ARE STILL SHOWING GOOD EVIDENCE OF THE UPPER LEVEL RIDGE BUILDING INTO THE AREA WHICH WILL ALLOW FOR GRADUAL CLEARING FROM WEST TO EAST. THE MODELS ARE ALSO PICKING UP ON A WEAK UPPER LEVEL WAVE MOVING THROUGH THE RIDGE TUESDAY MORNING. NOT COMPLETELY SURE THAT THIS FEATURE WILL PAN OUT SINCE THE LATEST WATER VAPOR LOOP IS CURRENTLY SHOWING THIS WAVE LIFTING RAPIDLY NORTHEAST WHICH SHOULD CAUSE IT TO SHEAR OUT FAIRLY RAPIDLY. WE DID KEEP A SMALL CHANCE OF SHOWERS IN THE WESTERN HALF OF THE FORECAST AREA DURING THE MORNING HOURS...BUT MOST OF THE ACTIVITY SHOULD BEGIN TO DISSIPATE BY MIDDAY. THE MAJORITY OF THE AREA SHOULD SEE SOME SUNSHINE EXCEPT FOR THE EXTREME NORTHEAST PART OF THE FORECAST AREA WHERE THE TAIL END OF THE CYCLONIC FLOW FROM THE CLOSED LOW WILL STILL AFFECT THAT REGION. .LONG TERM...(TUESDAY THROUGH SUNDAY) ISSUED AT 411 AM MDT MON MAY 20 2013 THE MODELS CONTINUE TO ADVERTISE STRENGTHENING SOUTHWESTERLY FLOW ALOFT AND INCREASING LLVL MOISTURE ADVECTION ON WEDNESDAY AND THURSDAY. SOUTHEASTERLY SFC WINDS ACROSS THE PLAINS WILL BEGIN TO TRANSPORT THE HIGHER DEWPOINTS TO AREAS ALONG AND EAST OF THE LARAMIE RANGE BY WEDNESDAY AFTN. THIS TRANSLATES INTO WEAK INSTABILITY WITH THE GFS AND NAM SHOWING LI VALUES OF -1C TO -2C OVER THE PLAINS OF SOUTHEAST WY. PRECIP CHANCES LOOK BETTER ON THURSDAY AFTN AS A SHORTWAVE EJECTS NORTHWARD ON THE EASTERN SIDE OF THE PACIFIC NORTHWEST UPPER LOW. THIS SHORTWAVE WILL INTERACT WITH BETTER SFC INSTABILITY AND DEEP LAYER SHEAR OF 40 KTS SUGGESTS SOME POTENTIAL FOR STRONG TO MARGINALLY SEVERE STORMS. STRATUS DEVELOPMENT OVER THE PLAINS LOOKS POSSIBLE ON THURSDAY NIGHT WITH THE MOIST SE UPSLOPE. APPEARS THAT THERE WILL BE AT LEAST A SLIGHT CHANCE OF SHOWERS AND TSTMS EACH AFTN ALONG AND EAST OF THE LARAMIE RANGE FROM FRIDAY INTO THE WEEKEND AS THE UPPER LEVEL TROUGH IS LOCATED ALONG THE WEST COAST. HARD TO PINPOINT AN AFTERNOON THAT WILL HAVE GREATER COVERAGE OF STORMS AT THIS POINT. THE GFS HAS THE SFC TROUGH ALONG THE WY-NE BORDER ON SATURDAY AND SUNDAY...WHICH WOULD KEEP THE BEST MOISTURE AND INSTABILITY OVER THE PANHANDLE. THE ECMWF PULLS THE HIGH DEWPOINTS FURTHER WEST ALONG THE FRONT RANGE. NEEDLESS TO SAY...THE SHORTWAVES EJECTING ACROSS THE CWA WILL PLAY A BIG FACTOR IN THE SFC PRESSURE FIELD AND RESULTANT MOISTURE ADVECTION. WITH MODERATE SOUTHWESTERLY FLOW AND GOOD INSTABILITY...THE POTENTIAL WILL LIKELY EXIST FOR SOME STRONG TO SEVERE STORMS. && .AVIATION...(FOR THE 12Z TAFS THROUGH 12Z TUESDAY MORNING) ISSUED AT 551 AM MDT MON MAY 20 2013 THE MAIN CONCERN WITH THIS TAF ISSUANCE IS THE CEILING HEIGHTS AND HOW GUSTY WIND SPEEDS WILL BE. LATEST RADAR LOOP WAS SHOWING SCATTERED LIGHT RAIN SHOWERS STILL LINGERING ACROSS RWL WITH ANOTHER BATCH OF SHOWERS MOVING INTO THE NORTHERN NEBRASKA PANHANDLE. THE SHOWERS ACROSS THE NORTHERN PANHANDLE ARE ASSOCIATED WITH A PIECE OF SHORTWAVE ENERGY MOVING THROUGH WESTERN SOUTH DAKOTA. THIS BAND OF SHOWERS SHOULD CONTINUE TO PUSH SOUTH THROUGH THE COURSE OF DAY AND BRING RAIN TO ALL OF THE PANHANDLE SITES BY MIDDAY. CYS AND LAR SHOULD ALSO SEE THIS BAND OF SHOWERS BY AROUND 18Z. CEILINGS SHOULD DROP INTO THE MVFR CATEGORY ONCE THIS BAND OF SHOWERS MOVES THROUGH...BUT THE CEILINGS SHOULD GENERALLY STAY IN THE VFR CATEGORY UNTIL THEN. THE EXCEPTION WILL BE IN RWL WHERE THEY ARE STARTING OUT IN THE IFR CATEGORY...BUT SHOULD IMPROVE TO MVFR BY 15Z. NORTHWEST WINDS WILL BE ON THE INCREASE ACROSS THE AREA THIS MORNING DUE TO STRONG HIGH PRESSURE BUILDING INTO CENTRAL WYOMING WHILE LOW PRESSURE KEEPS ITS GRIP OVER THE NORTHERN PLAINS. THIS WILL PUT MOST OF THE AREA IN A SQUEEZE PLAY SITUATION WHICH WILL CAUSE WIND SPEEDS TO INCREASE TO 25 TO 30KTS WITH SOME GUSTS TO 40KTS BY MID MORNING. && .FIRE WEATHER... ISSUED AT 411 AM MDT MON MAY 20 2013 GUSTY NORTHWEST WINDS WILL BE IN PLACE TODAY WHICH MAY AFFECT THE MORGAN CREEK PRESCRIBED BURN AREA. HOWEVER...BENEFICIAL RAINFALL SHOULD TEND TO SUPPRESS ANY FIRE CONCERNS TODAY. THE BENEFICIAL RAINFALL TODAY THROUGH TONIGHT SHOULD ALSO KEEP THE MAJORITY OF THE AREA IN GREENUP AND POSSIBLY INCREASE THE GREEN UP POTENTIAL IN THE PANHANDLE. AFTER A BRIEF DRYING OUT PERIOD ON WEDNESDAY...HIGHER DEWPOINTS (50+) WILL RETURN TO AREAS EAST OF THE LARAMIE RANGE ON THURSDAY AND KEEP CONDITIONS MOIST THROUGH THE WEEKEND. && .CYS WATCHES/WARNINGS/ADVISORIES... WY...WINTER WEATHER ADVISORY UNTIL 6 PM MDT THIS EVENING FOR WYZ112- 114. NE...WIND ADVISORY UNTIL 9 PM MDT THIS EVENING FOR NEZ002-003-019>021- 054-055-095-096. && $$ UPDATE...LIEBL SHORT TERM...REC LONG TERM...FINCH AVIATION...REC FIRE WEATHER...REC