Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
000 FXUS65 KBOU 222137 AFDBOU AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE DENVER/BOULDER CO 337 PM MDT FRI AUG 22 2014 .SHORT TERM...(THIS EVENING THROUGH SATURDAY) ISSUED AT 336 PM MDT FRI AUG 22 2014 SHORTWAVE MOVING INTO WESTERN COLORADO NOW WITH A LARGE SHIELD OF RAIN SHOWERS OVER THE MOUNTAINS. MORE STABLE AIR IN THE LARGE RAIN SHIELD HAS LIMITED LIGHTNING THERE...WITH STRONGER CONVECTION AROUND THE EDGES. ON THE PLAINS WE WOUND UP WITH A HYBRID OF THE LEADING EDGE OF THE LIFT AND THE EAST/WEST CONVERGENCE ZONE. SURFACE WINDS ARE NORTHEAST AT 10-15 KNOTS FEEDING INTO THIS DEVELOPING RAINBAND. ANOTHER EAST/WEST BAND HAS DEVELOPED NEAR THE SOUTHERN COLORADO BORDER AND WILL ALSO COME NORTH THIS EVENING AHEAD OF THE MAIN RAIN AREA. THERE HAS BEEN SOME SEVERE WEATHER ON THE EAST END OF THE CONVECTION IN KIT CARSON AND CHEYENNE COUNTIES...THREAT SHOULD BE LOWER FURTHER WEST BUT STILL ENOUGH ENERGY FOR SOME THREAT IN OUR EASTERN TIER OF COUNTIES. AS FOR THE HEAVY RAIN THREAT...EVERYTHING SEEMS TO BE MOVING. SOME HEAVY RAIN BUT BACKBUILDING/TRAINING POTENTIAL APPEARS LIMITED. SLOWED DOWN THE CLEARING IN THE MIDDAY UPDATE AND WILL STICK WITH THE EXISTING FORECAST. IT WILL TAKE HALF THE NIGHT FOR THE MAIN AREA OF RAIN TO GET PAST DENVER...AND THERE WILL LIKELY STILL BE SOME WEAKER CONVECTION BEHIND THAT...SO THREAT OF MORNING FOG IS LOOKING LOW. IF IT DID CLEAR OUT NICELY THAN THERE COULD BE SOME DENSE FOG. ON SATURDAY THERE WILL BE DRYING AND WARMING ALOFT AND IT LOOKS LIKE CONVECTION WILL BE FAIRLY WELL CAPPED. STILL EXPECTING SOME ISOLATED SHOWERS AND STORMS...MOST LIKELY OVER THE NORTHERN MOUNTAINS WHERE TEMPERATURES ALOFT WILL BE SLIGHTLY COOLER AND THERE MAY BE A LITTLE LIFT FROM THE WAVE PASSING NORTH OF US. .LONG TERM...(SATURDAY NIGHT THROUGH FRIDAY) ISSUED AT 336 PM MDT FRI AUG 22 2014 A DEEPENING UPPER LEVEL TROUGH OVER THE PACIFIC NORTHWEST IS EXPECTED TO SLIGHTLY INCREASE THE CHANCE OF SHOWERS AND T-STORMS ACROSS THE FCST AREA SATURDAY NIGHT INTO SUNDAY. ON SUNDAY...MODELS SHOW THE TROUGH CLOSING OFF OVER THE NORTHERN ROCKIES AND A WEAK COLD FRONT SLIPPING SOUTH INTO NERN COLORADO EARLY SUNDAY MORNING. 700-500MB SPEC HUMDITIES GRADUALLY RISE TO AROUND 6G/KG IN NERN COLORADO DURING THE DAY SUNDAY. NAM AND GFS SHOW POST- FRONTAL E-SELY BNDRY LAYER LAYER DEVELOPING DURING THE DAY. GFS GENERATES AN AREA OF LIGHT QPF OVER AND ALONG THE FRONT RANGE AND CHEYENNE RIDGE DURING THE AFTERNOON. EUROPEAN AND CANADIAN MODELS ARE LESS OPTIMISTIC ABOUT OUR RAIN CHANCES ON SUNDAY. ALL INDICATE SWLY STEERING WINDS OF 20-30KTS. SO ANY STORMS SHOULD MOVE AT A FAIRLY GOOD CLIP. BEST SHEAR AND LOW-LEVEL MOISTURE CONVERGENCE IS PROGGED TO MOVE AWAY FROM THE NRN FRONT RANGE AND OVER THE NERN CORNER OF THE CWA SUNDAY EVENING. ON MONDAY...THIS SAME SOUTHWEST FLOW ALOFT APPEARS TO DRY SLOT THE FCST AREA IN THE MORNING. ALTHOUGH LATER IN THE DAY...A SECOND WAVE OF ANOMALOUSLY LOW HEIGHTS ASSOCIATED WITH SIGNIFICANT COOLING ALOFT SWINGS SOUTHWARD OUT OF THE PACIFIC NORTHWEST. JET SHEAR INDUCED LIFT ON THE SOUTHEAST SIDE OF THIS TROUGH WILL COMBINE WITH POST-FRONTAL LOW- LEVEL UPSLOPE FLOW ON THE PLAINS RESULTING IN ANOTHER SHOT OF PRECIP. HOWEVER...MONDAY PRECIPITABLE WATER AND SPECIFIC HUMIDITY VALUES LOWER THAN CURRENT VALUES. SO PRECIP AMOUNTS MONDAY AFTERNOON AND NIGHT FROM ISOLATED TO SCATTERED STORM COVERAGE NOT EXPECTED TO BE SIGNIFICANT. GFS SHOWS THE UPPER TROUGH AXIS AND MAIN COLD POOL ALOFT PASSING OVER THE FCST AREA DURING THE DAY TUESDAY. WHILE THE 12Z ECMWF AND CANADIAN GEM SHOW THIS UPPER TROUGH AND COLD AIR ALOFT PASSING OVERHEAD WEDNESDAY MORNING. THAT SET...ALL THREE MODELS SHOW COOLER TEMPERATURES AND A CONTINUED CHANCE OF SHOWERS/T-STORMS ON TUESDAY...GENERALLY EAST OF THE MTNS. BY MID-WEEK...MOISTURE AND COOL AIR FLUSH OUT WITH NWLY FLOW ALOFT AS A LARGE HIGH PRESSURE RIDGE BUILDING OVER THE WESTERN CONUS. && .AVIATION...(FOR THE TAFS THROUGH 00Z SATURDAY LATE AFTERNOON) ISSUED AT 336 PM MDT FRI AUG 22 2014 SCATTERED SHOWERS WILL INCREASE LATER THIS AFTERNOON WITH ISOLATED THUNDERSTORMS. THERE WILL BE AREAS OF MVFR CEILINGS AND VISIBILITIES THIS EVENING...WITH CONDITIONS LIFTING BETWEEN 04Z AND 08Z. THERE IS A SLIGHT CHANCE OF IFR/LIFR IN FOG EARLY SATURDAY MORNING...THEN VFR CONDITIONS ARE EXPECTED FOR THE REST OF SATURDAY WITH ONLY ISOLATED THUNDERSTORMS IN THE AFTERNOON. && .HYDROLOGY... ISSUED AT 336 PM MDT FRI AUG 22 2014 SOME OF THE THUNDERSTORMS ON THE PLAINS WILL PRODUCE HEAVY RAIN THROUGH THIS EVENING. FAST CELL MOTIONS WILL LIMIT THE FLOOD THREAT HOWEVER. TRAINING OF CELLS WOULD BE REQUIRED...AND AT THIS TIME EVERYTHING IS MOVING. MOST PLACES WILL EXPERIENCE A PERIOD OF MODERATE TO HEAVY RAIN AS THE BAND MOVES OVER...WITH 1 TO 2 INCHES OF RAIN IN 1 TO 2 HOURS AND EXPECT THAT THIS WILL BE MAINLY TOWARD THE LOWER END OF THIS RANGE. STILL SOME POTENTIAL FOR HEAVIER OR MORE PROLONGED RAIN...BUT THE STRONGEST CONVECTION AND BEST MOISTURE WILL BE SHIFTING EAST OF OUR AREA AFTER THE NEXT COUPLE OF HOURS. FURTHER WEST THERE WILL BE SOME SIGNIFICANT RAINFALL...BUT NOT AS INTENSE AND THE FLOOD THREAT LOOKS LOW EVEN IN THE BURN AREAS. && .BOU WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...GIMMESTAD LONG TERM...BAKER AVIATION...GIMMESTAD HYDROLOGY....GIMMESTAD

USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.