Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 261625
AFDBOU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DENVER/BOULDER CO
1025 AM MDT TUE AUG 26 2014

.UPDATE...
ISSUED AT 1025 AM MDT TUE AUG 26 2014

MOIST AIRMASS OVER THE AREA TODAY. PRECIPITABLE WATER VALUES ARE
AROUND AN INCH ALONG THE FRONT RANGE WITH AN INCH AND A QUARTER
OVER THE PLAINS. THE MOISTURE MAY INCREASE A LITTLE INTO THE
EVENING HOURS. CAPES WILL REACH UP TO 2000 J/KG. SHEAR IS NOT AS
GOOD AS YESTERDAY WITH 500 MB LEVEL WINDS DECREASING TO LESS THAN
20 KNOTS. THIS WILL KEEP THE SEVERE THREAT LOW...BUT A FEW WILL
BE POSSIBLE OVER THE EASTERN PLAINS. BECAUSE OF THE MOISTURE AND
SLOWER MID LEVEL WINDS...THERE WILL BE A THREAT FOR FLASH
FLOODING. SO WILL KEEP THE FLASH FLOOD WATCH IN EFFECT OVER PARTS
OF THE PLAINS WHERE THE BEST STORM COVERAGE AND MOISTURE IS
EXPECTED TO BE.

EXPECT STORMS TO START FORMING EARLY THIS AFTERNOON OVER THE
HIGHER TERRAIN AND THEN SPREAD EASTWARD. WILL KEEP HIGH POPS IN
THE FORECAST FOR THIS AFTERNOON AND TONIGHT.

THE UPPER LEVEL LOW WILL CONTINUE TO BRING SHOWERS AND STORMS
THROUGH THURSDAY. INCREASED POPS FOR THESE DAYS TO REFLECT THE
WET PATTERN THAT WILL LINGER THROUGH THURSDAY.

&&

.SHORT TERM...(TODAY THROUGH TONIGHT )
ISSUED AT 349 AM MDT TUE AUG 26 2014

IN COLORADO WE GET A SMALL HANDFULL OF DAYS EACH YEAR IN WHICH
THUNDERSTORMS CAN OCCUR AROUND THE CLOCK. WE ARE IN ONE OF THOSE
PATTERNS TODAY...AS WE CAN SEE ON RADAR EARLY THIS MORNING...
ANOTHER IN A SERIES OF THUNDERSTORMS WAS MOVING THROUGH DIA AT
4AM. WE STILL EXPECT THE CONVECTION THIS MORNING TO END FROM THE
WEST...TO BE REPLACED BY AREAS OF FOG AND STRATUS.

THUNDERSTORMS WILL BLOSSOM OVER THE HIGH COUNTRY THIS MORNING...
THEN SPREAD TO THE PLAINS DURING THE AFTERNOON. I SLOWED THE
TRANSITION TO PLAINS CONVECTION BY A COUPLE OF HOURS.  WITH DIV Q
ALOFT...AND A POSSIBLE WEAK UPPER TROUGH COMBINED WITH A MOIST AND
UNSTABLE AIRMASS...THUNDERSTORMS WILL BECOME WIDESPREAD
TONIGHT...ESPECIALLY FOR THE PALMER DIVIDE AND THE COUNTIES JUST
NORTH OF THE PALMER DIVIDE. IT IS DIFFICULT TO TELL AT THIS HOUR
OF THE MORNING EXACTLY HOW THE CONVECTION DEVELOPS...BUT IF STORMS
STALL OR THERE ARE TRAINING ISSUES WITH THE THUNDERSTORMS THE RISK
OF FLOODING ESCALATES. FOR THESE REASONS WE ARE ISSUING A FLASH
FLOOD WATCH FOR TONIGHT OVER THE PALMER DIVIDE...EASTERN ADAMS AND
EASTERN ARAPAHOE AND WASHINGTON COUNTIES.

IT WILL BE ANOTHER MILD DAY FOR AUGUST WITH TEMPERATURES IN THE
MID TO UPPER 70S ON THE PLAINS.

.LONG TERM...(WEDNESDAY THROUGH MONDAY)
ISSUED AT 349 AM MDT TUE AUG 26 2014

AN ANOMALOUSLY COOL AND MOIST AIRMASS ACCOMPANYING AN UPPER LEVEL
SHORTWAVE TROUGH WILL CONTINUE ITS SLOW EASTWARD PROGRESS ACRS
COLORADO ON WEDNESDAY. MODELS ALSO SHOW A FAIRLY DEEP PLUME OF
SUBTROPICAL MOISTURE FLOWING NEWRD OVER SRN AND ERN PORTIONS OF
COLORADO DURING THE DAY AHEAD OF THE TROUGH. WIND FIELDS SHOW SOME
OF THIS MOISTURE CURVING WESTWARD UP AGAINST THE EAST FACE OF THE
FRONT RANGE. WHILE LARGE SCALE LIFT APPEARS MODEST ACCORDING TO QG
VERTICAL VELOCITY FIELDS...OROGRAPHIC LIFT AND DESTABILIZATION OF
THE AIRMASS DUE TO COOLING ALOFT SHOULD BE SUFFICIENT TO GIVE US A
GOOD CHANCE OF SHOWERS AND THUNDERSTORMS ON WEDNESDAY...
PARTICULARLY OVER AND ALONG THE FRONT RANGE LATE IN THE DAY.
PRECIPITABLE WATER VALUES ON WEDNESDAY LOOK SIMILAR TO THOSE
EXPECTED TODAY...ANYWHERE FROM 0.90 INCH UP AGAINST THE FOOTHILLS
TO AROUND 1.5 INCH IN EASTERN PARTS OF THE CWA. THEREFORE STORMS
ROUGHLY EAST OF A STERLING TO LIMON LINE WILL HAVE THE POTENTIAL
TO PRODUCE LOCALLY HEAVY RAINFALL. TEMPERATURES ON THE PLAINS
WEDNESDAY EXPECTED TO BE AS MUCH AS 8-10F BELOW AVERAGE FOR THE
DATE. AVERAGE HIGH FOR DENVER ON THE 27TH IS 85F. HIGH COUNTRY
TEMPERATURES ALSO QUITE COOL WITH HIGHS ABOVE TIMBERLINE POSSIBLY
NOT GOING ABOVE 45F.

WEDNESDAY NIGHT...THE UPPER TROUGH SLOWLY PASSES OVER THE FCST AREA.
FLOW AROUND THE BOTTOM SIDE OF THE TROUGH APPEARS TO ADVECT IN DRIER
AIR FROM THE FOUR CORNERS REGION WHICH COULD RESULT IN EITHER A LULL
IN PRECIPITATION OR ONLY JUST DELAY THE THE NEXT ROUND OF WRAP
AROUND PRECIPITATION ON THE BACK SIDE OF THE PASSING TROUGH. FOR NOW
WILL HANG ONTO SCATTERED POPS ON THE PLAINS AND SCATTERED TO LIKELY
POPS IN THE MTNS WEDNESDAY EVENING. THEN REDUCE POPS ON THE PLAINS
AFTER MIDNIGHT BUT KEEP POPS ON THE HIGH SIDE IN THE HIGH COUNTRY
WITH OROGRAPHIC LIFT GENERATED ON THE BACK SIDE OF TROUGH.
TEMPERATURES POSSIBLY COLD ENOUGH FOR A BIT OF SNOW ON THE HIGHER
PEAKS BY MORNING.

THURSDAY...MODELS SHOW THE TROUGH EXITING THE AREA...BUT SOME SHOW
MOIST NELY UPSLOPE FLOW AND RESPECTABLE QPF OVER AND ALONG THE
FRONT RANGE DURING THE DAY. WHILE THE OTHER MODELS SHOW A MUCH DRIER
NWLY FLOW OFF THE FRONT RANGE WITH THE TROUGH PULLING AWAY. FOR NOW
WILL GO ALONG WITH SURROUNDING WFOS AND HOLD ONTO SCATTERED POPS ON
THE PLAINS AND SCATTERED TO LIKELY POPS IN THE HIGH COUNTRY. HOWEVER
EXPECT LOWER QPF AMOUNTS. THURSDAY STILL LOOKS COOLER THAN AVERAGE
WITH LITTLE CHANGE IN TEMPERATURES FROM THE DAY BEFORE.

FRIDAY THROUGH LABOR DAY...WARMER TEMPERATURES AND MUCH DRIER
CONDITIONS FORECAST TO RETURN TO THE AREA OVER THE LABOR DAY WEEKEND
AS A STRONG HIGH PRESSURE RIDGE BUILDS IN FROM THE WEST.
TEMPERATURES SHOULD RETURN TO NEAR AVERAGE BY SUNDAY. COULD SEE A
SLIGHT DIP IN TEMPERATURES ON LABOR DAY WITH A WEAK...MOSTLY DRY
COLD FRONT BRUSHING THE AREA.

&&

.AVIATION...(FOR THE TAFS THROUGH 18Z WEDNESDAY MORNING)
ISSUED AT 1025 AM MDT TUE AUG 26 2014

THUNDERSTORMS WILL BE LIKELY IN THE DENVER AREA LATER THIS
AFTERNOON AND EVENING. THE BEST CHANCE FOR STORMS WILL BE 22Z TO
02Z...THOUGH THE THREAT FOR STORMS WILL CONTINUE INTO THE
OVERNIGHT HOURS. HEAVY RAIN...SMALL HAIL AND WIND GUSTS TO 40
KNOTS WILL BE POSSIBLE WITH THE STRONGER STORMS.

LOW CLOUDS WILL BE POSSIBLE EARLY WEDNESDAY MORNING WITH CEILINGS
BELOW 3000 FEET.

&&

.HYDROLOGY...
ISSUED AT 349 AM MDT TUE AUG 26 2014

RAINFALL RATES OF 2 INCHES IN AN HOUR WILL BE POSSIBLE WITH
THUNDERSTORMS TONIGHT. THE GREATEST FLOOD RISK WILL BE ALONG AND
NORTH OF THE PALMER DIVIDE AND THAT IS THE AREA IN THE FLASH FLOOD
WATCH. IT IS POSSIBLE THAT THE WATCH COULD BE EXPANDED FOR A
LARGER AREA IN EASTERN COLORADO.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
FLASH FLOOD WATCH FROM 6 PM MDT THIS EVENING THROUGH LATE
TONIGHT FOR COZ041-045>047-049.

&&

$$

UPDATE...MEIER
SHORT TERM...RTG
LONG TERM...BAKER
AVIATION...MEIER
HYDROLOGY...RTG


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