Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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000 FXUS65 KBOU 050859 AFDBOU AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE DENVER/BOULDER CO 259 AM MDT TUE MAY 5 2015 .UPDATE... ISSUED AT 820 PM MDT MON MAY 4 2015 PERSISTENT RAINFALL HAS WARRANTED THE ISSUANCE OF FLASH FLOOD WARNING IN ELBERT COUNTY. RADAR SHOWS THE RAIN TO CONTINUE THERE FOR A COUPLE MORE HOURS ANYWAY. MODELS KEEP SHOWING WIDESPREAD RAIN TO CONTINUE ALL NIGHT OVER MUCH OF THE CWA. WILL MAKE SOME MINOR ADJUSTMENT TO POPS...MAINLY LOWER THEM INT HE FAR NORTHEAST CORNER. && .SHORT TERM...(THIS EVENING THROUGH TUESDAY) ISSUED AT 129 PM MDT MON MAY 4 2015 LIGHTNING HAS BEEN ON THE INCREASE ACROSS THE STATE THIS EARLY AFTERNOON...WITH A FEW STORMS ALONG THE PALMER DIVIDE. STORM MOTION HAS BEEN TOWARDS THE NORTH NORTHEAST...AND RAINFALL RATES THUS FAR OVER THE DIVIDE HAVE BEEN MOSTLY LESS THAN AN INCH AN HOUR. GIVEN THAT...PRECIPITABLE WATER VALUES ARE IN NEAR RECORD TERRITORY FOR EARLY MAY...WITH NAM FORECASTING 0.88 INCHES THIS EVENING. SO WILL HAVE TO WATCH FOR POSSIBLE HEAVY RAIN WITH STORMS...BUT OVERALL THREAT OF SIGNIFICANT FLOODING IS LOW. INITIALLY OVER THE ELEVATED TERRAIN THERE MAY BE SOME SMALL HAIL WITH THESE STORMS. EXPECT CONVECTION TO CONTINUE TO INCREASE THIS EVENING...THEN A TRANSITION TO MOSTLY RAIN SHOWERS LATER THIS EVENING...MIXING WITH STATUS AND FOG OVERNIGHT. LIGHT PRECIPITATION IS EXPECTED TUESDAY EARLY...THEN ANOTHER ROUND WIDESPREAD SHOWERS AND THUNDERSTORMS IN THE AFTERNOON... PROBABLY MORE WIDESPREAD AS THE UPPER LOW APPROACHES FROM THE SOUTHWEST. AGAIN THE MAIN THREAT TUESDAY WILL BE LOCALLY HEAVY RAIN WITH THE STORMS...BUT CANNOT RULE OUT SMALL HAIL AS LIFT ASSOCIATED WITH THE UPPER LOW APPROACHES. .LONG TERM...(TUESDAY NIGHT THROUGH MONDAY) ISSUED AT 129 PM MDT MON MAY 4 2015 A DAMP AND COOL PERIOD WILL PREVAIL THROUGH MUCH OF THE LONG TERM. THE MODELS ARE ALL PRETTY CONSISTENT LIFTING THE LOW OVER COLORADO TUESDAY NIGHT AND WEDNESDAY WITH ATTENDANT QUASIGEOSTROPHIC ASCENT KEEPING THE PRECIPITATION THREAT HIGH. THERE IS A BIT OF LARGE SCALE SUBSIDENCE FORECAST TO MOVE OVERHEAD WEDNESDAY EVENING AND EARLY THURSDAY WHICH WILL PROBABLY RESULT IN LOWER BUT NOT NECESSARILY ZERO POPS DURING THAT TIME FRAME. INCREASING UPSLOPE FLOW AND QG ASCENT ASSOCIATED WITH ANOTHER UPPER LEVEL LOW WILL RETURN LATER THURSDAY AND CONTINUE THROUGH AT LEAST LATE SATURDAY AND PERHAPS INTO SUNDAY. THIS WILL RAMP UP THE PRECIPITATION THREAT AGAIN FOR LATER IN THE WEEK...PERHAPS LEADING TO A SUBSTANTIAL RAIN/SNOW EVENT BY THE WEEKEND...DEPENDING AS USUAL...ON THE EXACT TRACK OF THE CYCLONE. SUBSIDENCE...DRYING AND WARMING LOOK TO BE IN STORE FOR EARLY NEXT WEEK AS THIS SECOND FEATURE MOVES INTO THE GREAT PLAINS. ALL IN ALL IT LOOKS LIKE THE SEVERE WEATHER THREAT SHOULD REMAIN RATHER LOW THROUGH MOST OF THIS TIME FRAME BASED ON FORECAST CAPE VALUES ALTHOUGH THE THREAT OF THUNDERSTORMS WILL BE AROUND... ESPECIALLY DURING THE AFTERNOON AND EVENING HOURS. FORECAST PRECIPITABLE WATER VALUES ARE HIGH ENOUGH TO ALLOW FOR SOME DECENT QPF...ESPECIALLY IN HEAVIER SHOWERS AND THUNDERSTORMS. BURN SCARS IN THE FOOTHILLS COULD HAVE SOME ISSUES IF A STRONGER CONVECTIVE CELL WERE TO PASS BY. && .SHORT TERM...(THIS EVENING THROUGH TUESDAY) ISSUED AT 129 PM MDT MON MAY 4 2015 LIGHTNING HAS BEEN ON THE INCREASE ACROSS THE STATE THIS EARLY AFTERNOON...WITH A FEW STORMS ALONG THE PALMER DIVIDE. STORM MOTION HAS BEEN TOWARDS THE NORTH NORTHEAST...AND RAINFALL RATES THUS FAR OVER THE DIVIDE HAVE BEEN MOSTLY LESS THAN AN INCH AN HOUR. GIVEN THAT...PRECIPITABLE WATER VALUES ARE IN NEAR RECORD TERRITORY FOR EARLY MAY...WITH NAM FORECASTING 0.88 INCHES THIS EVENING. SO WILL HAVE TO WATCH FOR POSSIBLE HEAVY RAIN WITH STORMS...BUT OVERALL THREAT OF SIGNIFICANT FLOODING IS LOW. INITIALLY OVER THE ELEVATED TERRAIN THERE MAY BE SOME SMALL HAIL WITH THESE STORMS. EXPECT CONVECTION TO CONTINUE TO INCREASE THIS EVENING...THEN A TRANSITION TO MOSTLY RAIN SHOWERS LATER THIS EVENING...MIXING WITH STATUS AND FOG OVERNIGHT. LIGHT PRECIPITATION IS EXPECTED TUESDAY EARLY...THEN ANOTHER ROUND WIDESPREAD SHOWERS AND THUNDERSTORMS IN THE AFTERNOON... PROBABLY MORE WIDESPREAD AS THE UPPER LOW APPROACHES FROM THE SOUTHWEST. AGAIN THE MAIN THREAT TUESDAY WILL BE LOCALLY HEAVY RAIN WITH THE STORMS...BUT CANNOT RULE OUT SMALL HAIL AS LIFT ASSOCIATED WITH THE UPPER LOW APPROACHES. .LONG TERM...(TUESDAY NIGHT THROUGH MONDAY) ISSUED AT 129 PM MDT MON MAY 4 2015 A DAMP AND COOL PERIOD WILL PREVAIL THROUGH MUCH OF THE LONG TERM. THE MODELS ARE ALL PRETTY CONSISTENT LIFTING THE LOW OVER COLORADO TUESDAY NIGHT AND WEDNESDAY WITH ATTENDANT QUASIGEOSTROPHIC ASCENT KEEPING THE PRECIPITATION THREAT HIGH. THERE IS A BIT OF LARGE SCALE SUBSIDENCE FORECAST TO MOVE OVERHEAD WEDNESDAY EVENING AND EARLY THURSDAY WHICH WILL PROBABLY RESULT IN LOWER BUT NOT NECESSARILY ZERO POPS DURING THAT TIME FRAME. INCREASING UPSLOPE FLOW AND QG ASCENT ASSOCIATED WITH ANOTHER UPPER LEVEL LOW WILL RETURN LATER THURSDAY AND CONTINUE THROUGH AT LEAST LATE SATURDAY AND PERHAPS INTO SUNDAY. THIS WILL RAMP UP THE PRECIPITATION THREAT AGAIN FOR LATER IN THE WEEK...PERHAPS LEADING TO A SUBSTANTIAL RAIN/SNOW EVENT BY THE WEEKEND...DEPENDING AS USUAL...ON THE EXACT TRACK OF THE CYCLONE. SUBSIDENCE...DRYING AND WARMING LOOK TO BE IN STORE FOR EARLY NEXT WEEK AS THIS SECOND FEATURE MOVES INTO THE GREAT PLAINS. ALL IN ALL IT LOOKS LIKE THE SEVERE WEATHER THREAT SHOULD REMAIN RATHER LOW THROUGH MOST OF THIS TIME FRAME BASED ON FORECAST CAPE VALUES ALTHOUGH THE THREAT OF THUNDERSTORMS WILL BE AROUND... ESPECIALLY DURING THE AFTERNOON AND EVENING HOURS. FORECAST PRECIPITABLE WATER VALUES ARE HIGH ENOUGH TO ALLOW FOR SOME DECENT QPF...ESPECIALLY IN HEAVIER SHOWERS AND THUNDERSTORMS. BURN SCARS IN THE FOOTHILLS COULD HAVE SOME ISSUES IF A STRONGER CONVECTIVE CELL WERE TO PASS BY. && .AVIATION...(FOR THE TAFS THROUGH 12Z WEDNESDAY MORNING) ISSUED AT 257 AM MDT TUE MAY 5 2015 FOG IS THICKENING AND EXPECT 1/4SM TO 1/2SM VISIBILITY TO PERSIST AT KDEN THROUGH 12Z-15Z AS LONG AS EASTERLY FLOW HOLDS IN PLACE. SOME CHANCE THAT A MORE SOUTHEASTERLY LOW LEVEL FLOW COULD DEVELOP WHICH WOULD ERODE FOG...BUT AT THIS TIME SEEMS RATHER LOW PROBABILITY. KBJC WILL LIKELY REMAIN SOCKED IN AS WELL WHILE KAPA IS ON THE EDGE AND COULD SEE QUITE VARIABLE CONDITIONS. && .HYDROLOGY... ISSUED AT 840 PM MDT MON MAY 4 2015 AS MENTIONED ABOVE...THE MAIN PROBLEM AREA HAS TURNED OUT TO BE ELBERT COUNTY WITH SOME TRAINING OF CELLS...BUT MOSTLY ALMOST STATIONARY CELLS. THE RAINFALL BEGAN IN THE EASTERN HALF OF THE COUNTY AROUND 2 PM MDT AND HASEN`T REALLY STOPPED SINCE. WE HAVE BEEN UNABLE TO FIND ANY REAL MEASUREMENTS AS OF YET AND THE RADAR ESTIMATES HAVE BEEN CONTAMINATED BY PLENTY OF SMALL HAIL. THE WARNING IS OUT UNTIL 10 PM MDT AND WE MAY NEED TO EXTEND IT. && .BOU WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...RJK SHORT TERM...RTG LONG TERM...ET AVIATION...BARJENBRUCH HYDROLOGY...RJK

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