Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 271014
AFDBOU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DENVER/BOULDER CO
414 AM MDT SUN JUL 27 2014

.SHORT TERM...(TODAY THROUGH TONIGHT )
ISSUED AT 413 AM MDT SUN JUL 27 2014

CURRENT OBSERVATIONS SHOW EASTERLY FLOW AND HIGHER DEWPOINTS
PUSHING BACK TOWARD THE FRONT RANGE. THIS WILL HELP SET THE STAGE
FOR A MORE ACTIVE WEATHER DAY WITH STRONGER STORMS AND HEAVY
RAINFALL POTENTIAL. THE LATEST MODELS HAVE TRENDED TOWARD MORE
PRECIPITABLE WATER AVAILABLE FOR TODAY. WHILE CURRENT INTEGRATED
PW VALUES FROM GPS ARE MODEST AROUND 0.80 TO 0.90 INCH...LOW AND
MID LEVEL MOISTURE IS EXPECTED TO BEGIN POOLING ALONG THE FRONT
RANGE THROUGH THE COURSE OF THE DAY WITH PERSISTENT BUT WEAK
EAST/SOUTHEAST FLOW. AT THIS TIME FLASH FLOOD THREAT IS MARGINAL
AND MAINLY SOUTH OF I-70...SEE HYDRO SECTION BELOW FOR MORE
DETAILS. MAIN CHANGE IN THE LAST 12-24 HOURS IS FOR A WEAKER CAP
IN/NEAR THE FRONT RANGE WHICH WOULD BRING A MUCH HIGHER CHANCE OF
THUNDERSTORMS SPREADING AND DEVELOPING SOUTHEAST ACROSS THE I-25
CORRIDOR ESPECIALLY FROM DENVER METRO SOUTHWARD. LOW LEVEL
CONVERGENCE AND EROSION OF CAP WILL LIKELY BE AIDED BY WEAK DENVER
CYCLONE. WITH LOWER LCLS AND WEAK DENVER CONVERGENCE VORTICITY
ZONE MAY EVEN SEE A BRIEF LANDSPOUT TORNADO. ISOLATED SEVERE
THREAT WITH WET MICROBURST POTENTIAL IN THAT AREA AS WELL IF CAPES
REACH 1500 J/KG AS FORECAST SOUNDINGS SUGGEST OVER/NEAR THE PALMER
DIVIDE AREA.

MEANWHILE...THE NORTHEAST CORNER OF THE STATE WILL BE TOO STABLE
TO SUPPORT ANY SHOWERS/STORMS WITH COOLER AND SLIGHTLY DRIER
BOUNDARY LAYER FLOW. THIS WILL LIKELY KEEP AREAS NORTHEAST OF A
LINE FROM NEAR CHEYENNE WYOMING TO AKRON CAPPED AND DRY.

STORMS WILL GRADUALLY DIMINISH AND EXIT THE AREA FROM THE
NORTHWEST TO SOUTHEAST THROUGH THE COURSE OF THE EVENING. COULD BE
SOME PATCHY FOG/STRATUS AGAIN OVERNIGHT WITH MOIST AND WEAK
BOUNDARY LAYER FLOW.

.LONG TERM...(MONDAY THROUGH SATURDAY)
ISSUED AT 413 AM MDT SUN JUL 27 2014

MONDAY LOOKS LIKE A RELATIVELY QUIET DAY AS COOLER LOW LEVEL
TEMPERATURES AND CLOUD COVER SHOULD STABILIZE THE PLAINS. THERE
WILL STILL LIKELY BE SOME CONVECTION...MAINLY OVER AND NEAR THE
MOUNTAINS.

FOR TUESDAY AND WEDNESDAY...A WEAK TROUGH MOVING IN FROM THE WEST
WILL FLATTEN THE RIDGE AND CREATE A DEFORMATION ZONE IN THE AREA
OF COLORADO. MODELS HAVE FAIR CONSISTENCY ON THIS SCENARIO AND THE
TIMING...BUT THE EXACT PLACEMENT AND AMOUNT OF RAIN GENERATED VARY
SOMEWHAT. MANY MODEL SOLUTIONS DEVELOP AN AREA OF SIGNIFICANT RAIN
FROM THE NORTHERN COLORADO MOUNTAINS ACROSS EASTERN COLORADO
TUESDAY AFTERNOON AND TUESDAY NIGHT...WITH A PREFERENCE FOR A
BULLSEYE OVER THE FOOTHILLS OF BOULDER AND LARIMER COUNTIES.
MODEL RAINFALL IS GENERALLY IN THE HALF TO ONE INCH RANGE OVER
THE PLAINS...WITH MAXIMA OF TWO INCHES IN THE FOOTHILLS. IT LOOKS
LIKE THE ENVIRONMENT WILL STILL ALLOW THUNDERSTORMS IN ADDITION TO
MORE WIDESPREAD RAIN...SO WE WILL NEED TO BE WATCHING THE FLASH
FLOOD THREAT IN THIS PERIOD AS IT APPEARS THAT MANY FAVORABLE
INGREDIENTS WILL EXIST AND THE FOCUS WILL BE ON AREAS WITH
INCREASED VULNERABILITY. NOT A SURE THING YET THOUGH AS THE FOCUS
MAY NOT REMAIN IN ONE PLACE AS LONG AS IS SHOWN...OR MAY BE
ELSEWHERE AS IN THE LATEST GFS THAT HAS THIS BAND FURTHER
SOUTHWEST AND MOSTLY MISSES OUR AREA. I DID RAISE POPS FOR THIS
TIME PERIOD AND WILL MENTION POSSIBLE FLOODING IN THE HAZARDOUS
WEATHER OUTLOOK.

FOR LATER WEDNESDAY THROUGH THE REST OF THE WEEK...A WARMING AND
DRYING TREND. WOULD NOT BE SURPRISED TO SEE A RELATIVELY QUIET DAY
WEDNESDAY IN THE WAKE OF THE RAIN AS LOW LEVELS WILL BE COOL
AGAIN AND THERE SHOULD BE SOME WARMING ALOFT. STILL SOME
THUNDERSTORMS EACH DAY WITH A RETURN TO FAVORING AREAS IN AND NEAR
THE MOUNTAINS. THERE MAY BE ANOTHER INCREASE EARLY NEXT WEEK.

&&

.AVIATION...(FOR THE TAFS THROUGH 12Z MONDAY MORNING)
ISSUED AT 413 AM MDT SUN JUL 27 2014

PATCHY STRATUS STILL EXPECTED TO DEVELOP AROUND DAYBREAK WITH
POTENTIAL CEILINGS AROUND 2000 FT AGL. CHANCE OF CEILINGS IS ABOUT
50-60% AT THIS TIME FROM 12Z/13Z-16Z. ONCE DAYTIME HEATING
OCCURS...SHOULD SEE CLOUD DECK LIFT TO SCT-BKN AROUND 4130 FT AGL
BY 18Z. THUNDERSTORM CHANCES WILL BE HIGHER AGAIN TODAY SO TEMPO
THUNDER AND VRB20G35KT WINDS WARRANTED FOR 21Z-02Z. STORMS WILL BE
LOWER BASED WITH HEAVY RAIN AND VISIBILITY RESTRICTIONS TO 1-2SM
IN THUNDERSTORM CORES. STORM THREAT WILL DECREASE BY 03Z WITH
VFR CONDITIONS OVERNIGHT. LOW THREAT AROUND 20-30 PERCENT OF MVFR
CEILINGS OR FOG AFTER 10Z MONDAY BUT AT THIS TIME MAIN THREAT
WOULD BE NORTH OF THE FRONT RANGE AIRPORTS.

&&

.HYDROLOGY...
ISSUED AT 413 AM MDT SUN JUL 27 2014

PRECIPITABLE WATER VALUES BY LATE AFTERNOON/EARLY EVENING ARE
EXPECTED TO INCREASE TO AROUND 1.1 INCH...WELL ABOVE THE 75TH
PERCENTILE FOR JULY. IT WOULD TAKE 1.25 INCH AS SHOWN IN THE
WETTEST GFS SOLUTION TO REACH THE 2ND STANDARD DEVIATION OR NEAR
THE 95TH PERCENTILE. NOT LIKELY WE WILL SEE THAT...BUT STILL A
CHANCE WE COULD REACH THOSE NUMBERS WHICH WOULD INCREASE THE
FLASH FLOOD THREAT. MOST MODELS SUGGEST THE WARM CLOUD DEPTH
INCREASING TO ABOUT 5000 FT...SUFFICIENT FOR HEAVY RAINERS. AT THE
SAME TIME...NORTHWEST STEERING WINDS BEGIN TO WEAKEN BUT STORMS
SHOULD BE MOVING CLOSE TO 15 MPH FROM THE NORTHWEST AND STORM
INFLOW IS QUITE WEAK. AT THIS POINT...MOST PARAMETERS ARE MARGINAL
FOR FLASH FLOOD THREAT WITH MOST OF THE STRONGER STORMS PRODUCING
1 INCH OF RAIN IN 20-30 MINUTES...BUT A SLOWER MOVING STORM COULD
PRODUCE 2 INCHES IN AN HOUR OR LESS. HIGHEST LIKELIHOOD OF THESE
STRONGER STORMS AND FLASH FLOODING IS CERTAINLY FARTHER SOUTH INTO
PUEBLOS FORECAST AREA FROM TELLER AND EL PASO COUNTY
SOUTHWARD...BUT DEPENDING ON AMOUNT OF MOISTURE POOLING THERE IS
SOME THREAT ROUGHLY ALONG AND SOUTH OF THE I-70 CORRIDOR FAVORING
PARK...JEFFERSON...AND DOUGLAS COUNTIES. WILL CONTINUE TO MONITOR
LATEST PW TRENDS BUT FLASH FLOOD WATCH COULD STILL BE ISSUED FOR
THOSE AREAS.

AIRMASS WILL REMAIN FAVORABLE FOR HEAVY RAIN THIS WEEK WITH
PRECIPITABLE WATER OVER AN INCH...LIGHT WINDS ALOFT AND A
FAVORABLE DIRECTION PROFILE...UPSLOPE WINDS...AND A DEEP WARM
CLOUD LAYER. MAIN THREAT APPEARS TO BE LATE TUESDAY INTO EARLY
WEDNESDAY WHEN MORE SUSTAINED LIFT COULD CREATE NUMEROUS SLOW
MOVING THUNDERSTORMS. UPSLOPE WINDS WOULD FOCUS THE MAIN FLOOD THREAT
IN AND NEAR THE FRONT RANGE FOOTHILLS...MODELS CURRENTLY FAVOR
BOULDER AND LARIMER COUNTIES WITH A WIDESPREAD TWO INCHES OF RAIN.
THERE IS A GOOD CHANCE OF EMBEDDED THUNDERSTORMS THAT WOULD
PRODUCE LOCALIZED HEAVIER RAINFALL IN A FEW HOURS. FOR LATER
WEDNESDAY THROUGH SATURDAY THE THREAT WILL CONTINUE BUT
THUNDERSTORMS ARE EXPECTED TO BE LESS WIDESPREAD AND LESS
PERSISTENT SO THE FLOOD THREAT SHOULD BE LOWER AND MORE LOCALIZED.

&&

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

$$

SHORT TERM...BARJENBRUCH
LONG TERM...GIMMESTAD
AVIATION...BARJENBRUCH
HYDROLOGY...BARJENBRUCH/GIMMESTAD


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