Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 031053
AFDBOU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DENVER/BOULDER CO
453 AM MDT THU SEP 3 2015

.SHORT TERM...(TODAY THROUGH TONIGHT )
ISSUED AT 453 AM MDT THU SEP 3 2015

MOISTURE LEVELS OVER THE STATE HAVE BEEN GRADUALLY INCREASING
OVERNIGHT AS SOUTHWESTERLY FLOW ALOFT CONTINUES. THE INCREASE IN
MOISTURE SHOULD LEAD TO AN INCREASE IN SHOWER ACTIVITY THIS
AFTERNOON...INITIALLY OVER THE MOUNTAINS AND THEN OUT ACROSS THE
PLAINS IN THE LATE AFTERNOON AND EVENING. LIGHTNING DETECTION HAS
ALREADY RECORDED SOME THUNDERSTORMS OVER THE SAN JUAN MOUNTAINS
THIS MORNING...AND THE KGJX RADAR IS SHOWING A BAND OF SHOWERS
OVER SOUTHWESTERN COLORADO AS THE LEADING EDGE OF THE SUBTROPICAL
MOISTURE ADVANCES NORTHWARD. HAVE BUMPED THE POPS IN THE CENTRAL
MOUNTAINS UP TO LIKELY FOR THIS AFTERNOON. OTHER PARTS OF THE
COUNTY WARNING AREA SHOULD SEE SCATTERED SHOWERS AND THUNDERSTORMS
THROUGH THE EARLY EVENING. MODEL SOUNDINGS ON THE PLAINS SHOW A
BIT OF AN INVERTED-VEE PATTERN...INDICATIVE OF MORE GUSTY WINDS
THAN HEAVY RAIN. SOUNDINGS OVER THE MOUNTAIN SHOW DEEPER SATURATED
CONDITIONS. AN UPPER LEVEL JET WILL BE MOVING INTO THE STATE FROM
THE SOUTHWEST WITH THE DIFFLUENCE AHEAD OF THE JET BEING IN A
FAVORABLE POSITION TO ENHANCE CONVECTION THROUGH THE AFTERNOON
HOURS. TEMPERATURES WILL BE A LITTLE COOLER TODAY SINCE SKIES WILL
BE GETTING CLOUDY BY MID-AFTERNOON.

SHOWERS WILL MOVE OFF TO THE NORTHEAST PLAINS DURING THE EVENING
HOURS WITH DRYING CONDITIONS RETURNING TO THE FORECAST AREA
OVERNIGHT.

.LONG TERM...(FRIDAY THROUGH WEDNESDAY)
ISSUED AT 453 AM MDT THU SEP 3 2015

SUBTROPICAL MOISTURE IN SSW FLOW ALOFT WILL CONTINUE OVER THE AREA
ON FRI AS ANOTHER POSSIBLE DISTURBANCE MOVES ACROSS IN THE
AFTN/EVENING.  PRECIPITABLE WATER VALUES RANGE FM 0.5"-0.7" OVER THE
HIGHER TERRAIN WITH AROUND AN INCH OVER THE PLAINS.  WILL KEEP SCT
POPS IN THE MTNS HOWEVER NOT SURE ABOUT OVERALL COVERAGE OVER THE
PLAINS.  FOR NOW WILL MENTION A CHC CLOSER TO THE FRONT RANGE WITH A
SLIGHT CHC FURTHER EAST OVER THE PLAINS.  AS FOR HIGHS READINGS WILL
REMAIN ABV NORMAL ACROSS NERN CO WITH TEMPS IN THE UPPER 80S TO
LOWER 90S.

ON SAT AN UPPER LEVEL TROUGH WILL MOVE INTO THE GREAT BASIN WITH
INVREASING SWLY FLOW ALOFT.  ONCE AGAIN THERE ARE SOME DIFFERENCES
BETWEEN THE ECMWF AND GFS AS THE ECMWF SHIFTS THE MAIN PLUME OF
SUBTROPICAL MOISTURE EAST OF THE AREA WHILE THE GFS KEEPS IT OVER
ERN COLORADO.  STILL NOT SURE HOW THINGS WILL EVOLVE SO WILL ONLY
MENTION A SLIGHT CHC OF STORMS OVER THE AREA.  AS FOR HIGHS ONCE
AGAIN READINGS WILL BE IN THE UPPER 80S TO LOWER 90S ACROSS NERN CO.

BY SUN THE UPPER LEVEL TROUGH WILL MOVE ENE ACROSS THE NRN ROCKIES
WITH DRY WSW FLOW ALOFT ACROSS THE AREA.  A WK COOL FNT WILL MOVE
ACROSS NERN CO DURING THE DAY HOWEVER 850-700 MB TEMPS ONLY DROP A
DEGREE OR TWO SO AFTN HIGHS WILL STILL BE IN THE MID TO UPPER 80S.
LOW LEVEL MOISTURE BEHIND THIS WK FNT IS LACKING SO WILL NOT MENTION
ANY TSTMS.  WITH INCREASING LOW LVL FLOW AND LOW HUMIDITY LEVELS
FIRE DANGER WILL INCREASE ESPECIALLY OVER THE HIGHER TERRAIN.

ON MON DRY WSW FLOW ALOFT WILL CONTINUE OVER THE AREA WITH GUSTY
WINDS AND LOW HUMIDITY LEVELS OVER THE HIGHER TERRAIN SO FIRE DANGER
WILL REMAIN ELEVATED.  OVER NERN CO A SFC LEE TROUGH WILL BE IN
PLACE WHICH WILL LEAD TO ANOTHER DRY DAY OVER MOST OF THE PLAINS.
HOWEVER THE ECMWF DOES SHOW AN INCREASE IN LOW LVL MOISTURE OVER THE
FAR ERN PLAINS WHICH COULD LEAD TO SOME ISOLATED LATE AFTN/EVENING
STORMS ALONG A WK CONVERGENCE ZN.  AS FOR HIGHS WILL KEEP READINGS
IN THE LOWER TO MID 80S OVER NERN CO.

BY TUE THE ECMWF SHOWS DRY WLY FLOW ALOFT ACROSS THE AREA WITH A
COLD FNT MOVING ACROSS NERN CO. MEANWHILE THE GFS MOVES ANOTHER
UPPER LEVEL TROUGH QUICKLY ACROSS THE NRN ROCKIES WITH DRY WSW FLOW
ALOFT AND HOLDS OFF THIS FNT UNTIL TUE NIGHT. THE PREVIOUS RUN OF
THE GFS HAD THIS TROUGH A BIT FURTHER SOUTH WITH MORE MOISTURE ALONG
WITH A WK FNT MOVING INTO NERN CO BY AFTN. THUS THIS SETUP WOULD
HAVE PRODUCED AT LEAST A SLIGHT CHC OF TSTMS WHILE THE LATEST
SOLUTION HAS NOTHING. THE PREVIOUS RUN OF THE ECMWF DID NOT SHOW THE
COLD FNT MOVING INTO TUE NIGHT AND HAD ENOUGH LOW LVL MOISTURE OVER
PORTIONS OF THE PLAINS FOR SOME WDLY SCT STORMS.  AT THIS POINT WILL
LEAVE PREVIOUS FCST ALONE AND KEEP LOW POPS IN THE FCST WITH HIGHS
IN THE LOWER TO MID 80S ACROSS NERN CO.

FOR WED DRY WLY FLOW ALOFT IS SUPPOSED TO BE OVER THE AREA HOWEVER
THE ECMWF AND GFS DIFFER ON THEIR SFC SOLUTIONS.  THE GFS SHOWS
COOLER AIR MOVING INTO NERN CO BEHIND A FNT WITH READINGS IN THE
UPPER 70S TO LOWER 80S WHILE THE ECMWF SHOWS A LEE TROUGH OVER
ERN CO WITH ABOVE NORMAL TEMPS. ONCE AGAIN NOT SURE WHICH WAY TO
LEAN SO WILL JUST GO WITH A BLEND OF THE ECMWF/GFS.

&&

.AVIATION...(FOR THE TAFS THROUGH 12Z FRIDAY MORNING)
ISSUED AT 453 AM MDT THU SEP 3 2015

AVIATION IMPACTS SHOULD BE MINIMAL THROUGH THIS MORNING AND INTO
EARLY AFTERNOON. LATER THIS AFTERNOON...SHOWERS AND THUNDERSTORMS
ARE EXPECTED TO MOVE ACROSS THE DENVER AREA...MOVING FROM THE
SOUTHWEST TO NORTHEAST. GUSTY WINDS AND BRIEF HEAVY RAIN ARE GOING
TO BE THE MAIN THREATS AS THE STORMS MOVE THROUGH. CEILINGS SHOULD
REMAIN ABOVE 6000-8000 FEET AGL. SHOWERS WILL MOVE OFF TO THE EAST
BY ABOUT 9 PM TONIGHT WITH NO ADDITIONAL WEATHER EXPECTED AFTER
THAT.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...DANKERS
LONG TERM...RPK
AVIATION...DANKERS



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