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682
FXUS65 KBOU 300151
AFDBOU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DENVER/BOULDER CO
751 PM MDT TUE JUL 29 2014

.UPDATE...
ISSUED AT 724 PM MDT TUE JUL 29 2014

THIS EVENING WE HAVE TWO AREAS OF CONVECTION...ALONG THE WYOMING
BORDER IN WELD COUNTY TO THE SSE ACROSS NORTHERN WASHINGTON
COUNTY...THEN ALONG AND SOUTH OF THE PALMER DIVIDE. WITH LIGHT
WINDS ALOFT STORMS HAVE MOVED SLOWLY WITH RAINFALL RATES OF AN
INCH IN A HALF HOUR...WITH THE HIGHEST REPORT OVER 3 INCHES IN AN
HOUR NEAR WINDSOR THIS AFTERNOON. EXPECT THIS CONVECTION TO
SLOWLY SLIDE EAST AND SLOWLY WEAKEN OVERNIGHT.

AS UPPER TROUGH DROPS SOUTH TOMORROW...WE WILL LIKEY SEE
CONVECTION SLIDE SOUTH...THE BIG QUESTION IS HOW EARLY...SECOND
QUESTION IS WHETHER THE BULK OF THE CONVECTION WILL BE CONFINED TO
THE MOUNTAINS AND FOOTHILLS. BEST IDEA IS SHOWERS AND
THUNDERSTORMS SLIDING SOUTH IN THE MORNING AND EARLY
AFTERNOON...WITH SOME DRYING FROM THE NORTH LATE AFTERNOON. ONCE
AGAIN WE WILL HAVE TO WATCH FOR SLOW MOVING THUNDERSTORMS
PRODUCING HEAVY RAIN.

FOR NOW GIVEN THE QUESTIONS...NO CHANGES TO PREVIOUS FORECAST.

&&

.SHORT TERM...(THIS EVENING THROUGH WEDNESDAY)
ISSUED AT 333 PM MDT TUE JUL 29 2014

THUNDERSTORMS HAVE BECOME ORGANIZED AS THE FRONT EDGE OF THE
SYNOPTIC SCALE SHOWERS RAN INTO THE EASTERLY WINDS ON THE PLAINS.
EXPECT THIS AREA TO REMAIN THE FOCUS OVER THE NEXT SEVERAL HOURS
SPREADING EAST INTO THE INFLOW. ALSO EXPECT A NEW AREA OF STORMS
TO DEVELOP OVER THE FOOTHILLS IN A COUPLE OF HOURS AS THE
EASTERLIES COMBINED WITH OUTFLOW FROM THE CURRENT CONVECTION
PUSHES UPHILL INTO THE INCOMING SHOWER AREA. THIS MAY RESULT IN
WIDESPREAD RAINFALL THAT IS HEAVIER THAN WAS FORECAST AS THE
SECOND AREA COULD SPREAD BACK EASTWARD OVERNIGHT. THIS WOULD HIT
THE AREA FROM DENVER NORTH TO THE STATE LINE HARD THIS EVENING.
TRENDED FORECAST THIS WAY...THOUGH STILL NOT SURE WE WILL HAVE THE
SUSTAINED LARGE SCALE UPSLOPE BEYOND THE CURRENT TRENDS MENTIONED
ABOVE. FOR THE TIME BEING...RAISED FORECAST RAINFALL A BIT...NOW
SHOWING 1.5 TO 2.5 INCHES INSTEAD OF THE 1 TO 2 THAT WE HAD...AND
RAISED POPS FURTHER.

FOR WEDNESDAY STILL SOME QUESTIONS AS IT WILL BE COOLER AND THERE
WILL BE A BIT LESS OF EVERYTHING TO WORK WITH. SOME OF THE MODELS
GENERATE A SUBSTANTIAL BATCH OF CONVECTION THAT DROPS FROM SE
WYOMING ACROSS THE FRONT RANGE CITIES WEDNESDAY MORNING.
CONDITIONS MAY STILL BE FAVORABLE FOR HEAVY RAIN AT THAT TIME...IT
WILL BE DRYING FURTHER EAST AND LATER IN THE DAY. WE ALREADY HAD
PRETTY HIGH POPS AND QPF FOR WEDNESDAY SO I HAVE LEFT THAT ALONE
AND WILL KEEP THE FLASH FLOOD WATCH RUNNING THROUGH WEDNESDAY. I
SUSPECT THE THREAT MAY BE LOWER IN THE AFTERNOON...BUT WE COULD
HAVE ADDITIONAL PROBLEMS IN THE MORNING ESPECIALLY GIVEN WHAT WILL
BE HAPPENING OVERNIGHT.

.LONG TERM...(WEDNESDAY NIGHT THROUGH TUESDAY)
ISSUED AT 333 PM MDT TUE JUL 29 2014

SOME DECREASE IN THE SHOWER AND THUNDERSTORM ACTIVITY WEDNESDAY
EVENING AS FORCING FROM MID LEVEL SHORTWAVE MOVES EAST OF THE
CFWA AND SLIGHTLY DRIER AIR SPREADS IN FROM THE NORTH. BEST CHANCE
FOR STORMS TO BE ACROSS THE MOUNTAINS AND PALMER DIVIDE. STORMS
WILL STILL BE CAPABLE FOR PRODUCING LOCALLY HEAVY RAIN...BUT
FLASH FLOOD THREAT SHOULD BE DECREASING. THUS WILL NOT EXTEND THE
FLASH FLOOD WATCH INTO THE EVENING HOURS. OVERNIGHT...AIRMASS TO
CONTINUE TO STABILIZE AND BECOME A BIT DRIER WITH ONLY SOME WEAK
CONVECTION POSSIBLE OVER THE HIGHER TERRAIN. ON THURSDAY...UPPER
RIDGE ACROSS GREAT BASIN WITH NORTHWEST FLOW ALOFT OVER COLORADO.
MODELS KEEP SOME MONSOONAL MOISTURE OVER THE AREA...MAINLY OVER
THE MOUNTAINS. BOUNDARY LAYER WIND AND RH PROGS SUGGEST SOME
POTENTIAL FOR LOW CLOUDS AND FOG IN AND NEAR THE FOOTHILLS DURING
THE MORNING...BUT FOG POTENTIAL APPEARS LIMITED AT THIS TIME TO
INCLUDE IN GRIDS. OTHERWISE A FEW STORMS POSSIBLE OVER THE HIGHER
TERRAIN DURING THE MORNING...THEN STORM CHANCES INCREASE ACROSS
THE AREA DURING THE AFTERNOON AND EVENING. BEST CHANCE FOR STORMS
TO BE OVER THE HIGHER TERRAIN. THOUGH AIRMASS TO BE A BIT
DRIER...STORMS WILL BE CAPABLE OF PRODUCING LOCALLY HEAVY RAIN.
LOOKS TO BE ENOUGH FLOW ALOFT TO KEEP STORMS MOVING...LIMITING
THE FLASH FLOOD THREAT. STILL...BURN AREAS AND LOCATIONS WHICH
RECEIVED DECENT RAIN FROM THE RECENT STORMS WILL NEED TO BE
MONITORED. AIRMASS TO BE A BIT WARMER THOUGH TEMPERATURES WILL
REMAIN BELOW NORMAL.

FOR FRIDAY AND SATURDAY...UPPER LEVEL RIDGE BEGINS SHIFTING EAST
INTO COLORADO WITH WEAKENING NORTHWEST FLOW ALOFT. MODELS SHOW AN
INCREASE IN MONSOONAL MOISTURE WHICH MAY LEAD TO A BETTER CHANCE
FOR AFTERNOON AND EVENING THUNDERSTORMS. BEST CHANCE FOR STORMS TO
BE ACROSS THE MOUNTAINS AND ALONG THE FOOTHILLS. LOCALLY HEAVY
RAIN WILL CONTINUE TO BE A CONCERN...WITH AN INCREASING CHANCE FOR
SOME SLOW MOVING STORMS. TEMPERATURES TO BE SLIGHTLY WARMER...BUT
REMAINING BELOW NORMAL.

LOOKING AHEAD TO SUNDAY THROUGH TUESDAY. UPPER RIDGE SHIFTS
ACROSS COLORADO SUNDAY WITH FAIRLY LIGHT NORTHWEST FLOW ALOFT.
MONSOONAL MOISTURE WILL CONTINUE TO ADVECT INTO THE AREA...WITH
DECENT CHANCE FOR THUNDERSTORMS. LOCALLY HEAVY RAIN TO REMAIN A
THREAT. FLOW ALOFT BECOMES SOUTHWEST MONDAY AND TUESDAY AS MODELS
SHIFT THE RIDGE EAST AND BRING AN UPPER TROUGH INTO THE GREAT
BASIN. SOME DECREASE IN THE MONSOONAL MOISTURE...STILL ENOUGH FOR
A CHANCE OF AFTERNOON AND EVENING THUNDERSTORMS. TEMPERATURES LOOK
TO BE SLIGHTLY BELOW NORMAL.

&&

.AVIATION...(FOR THE TAFS THROUGH 00Z WEDNESDAY LATE AFTERNOON)
ISSUED AT 740 PM MDT TUE JUL 29 2014

THERE WILL BE SOME THUNDERSTORMS ON THE APPROACHES INTO DIA...THE
LINGERING STORMS ARE MOST LIKELY OVER THE PALMER DIVIDE...SO APA
HAS THE BEST CHANCE OF STORMS OVERNIGHT. WITH THE MOIST AIRMASS
AND THE NUMBER OF STORMS THIS AFTERNOON...WOULD NOT BE SURPRISED
TO SEE MVFR OR IFR CONDITIONS OVERNIGHT DUE TO THE HIGH LEVEL OF
MOISTURE IN THE ATMOSPHERE. MORE STORMS ARE POSSIBLE AT ALL AREA
AIRPORTS WEDNESDAY.

&&

.HYDROLOGY...
ISSUED AT 333 PM MDT TUE JUL 29 2014

EXPECT THE FOCUS FOR THUNDERSTORMS WILL CONTINUE TO SHIFT EAST
THIS EVENING...SO STRONGEST STORMS WITH HEAVIEST RAIN WILL TARGET
FAR NORTHEAST COLORADO. AS WE HAVE SEEN TODAY...RAINFALL RATES OF
2 INCHES IN AN HOUR ARE LIKELY TO CONTINUE. A LARGE AREA OF STORMS
OVER NORTHWEST COLORADO WILL REACH THE COLORADO AND WYOMING
BORDER BY SUNRISE...THEN ARE EXPECTED TO DROP SOUTH ACROSS THE
DIVIDE...FOOTHILLS...AND URBAN CORRIDOR IN THE MORNING AND EARLY
AFTERNOON. WITH HIGH PRECIPITABLE WATER VALUES...BUT SOMEWHAT
COOLER TEMPERATURES ON WEDNESDAY...COULD AGAIN SEE 0.75 TO 1 INCH
AMOUNTS IN A HALF HOUR IN THE STRONGER STORMS. A FLASH FLOOD WATCH
WILL REMAIN IN EFFECT UNTIL 6PM ON WEDNESDAY.

THE IT APPEARS
THERE WILL BE ONE OR MORE LARGE AREAS OF THUNDERSTORMS WITH
MODERATE TO HEAVY RAIN THIS EVENING...AND POSSIBLY ALL NIGHT.
FOCUS WILL BE MAINLY ALONG THE FRONT RANGE DURING THE EARLY
EVENING...LIKELY SPREADING EASTWARD OVERNIGHT. EXPECT MOST OF THE
STORMS TO PRODUCE 1-2 INCH PER HOUR RAINFALL RATES...BUT THEY
COULD BE SUSTAINED FOR A LONG TIME. END RESULT SHOULD BE MINOR
FLOODING IN MANY AREAS AND SEVERAL LOCATIONS THAT EXPERIENCE
SIGNIFICANT FLASH FLOODING.

WIDESPREAD RAINFALL MAY BE ENOUGH TO PRODUCE FLOODING ON THE
LARGER RIVERS INCLUDING THE SOUTH PLATTE. RIVER FORECASTERS ARE
EVALUATING THE SITUATION. IF THE AREA CURRENTLY EXPERIENCING
STRONG THUNDERSTORMS REMAINS THIS WAY THROUGH THE EVENING...THEN
RIVER FLOODING WILL BE LIKELY WEDNESDAY MORNING.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
FLASH FLOOD WATCH THROUGH WEDNESDAY AFTERNOON FOR COZ033>047-049.

&&

$$

UPDATE...RTG
SHORT TERM...GIMMESTAD
LONG TERM...D-L
AVIATION...RTG
HYDROLOGY...RTG




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