Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 211534
AFDBOU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DENVER/BOULDER CO
934 AM MDT THU AUG 21 2014

.UPDATE...
ISSUED AT 934 AM MDT THU AUG 21 2014

ANOTHER ROUND OF ISOLATED TO SCATTERED THUNDERSTORMS IS EXPECTED
TODAY. BEST CHANCE WILL BE LATER IN THE DAY...LATE AFTERNOON AND
EVENING. CURRENT FORECAST INDICATES THE BEST CHANCE WILL BE DURING
THE EVENING HOURS AND THIS STILL APPEARS ON TRACK. WILL JUST MAKE
MINOR TWEAKS TO LINE UP WITH THE LATEST TRENDS FOR TODAY.

THERE WILL BE A BETTER CHANCE FOR STORMS ON FRIDAY. UPPER LEVEL
LOW SPINNING OVER SOUTHERN CALIFORNIA WILL LIFT NORTHEAST THROUGH
THE NEXT COUPLE OF DAYS. THIS SHOULD BRING A SWATH OF SHOWERS AND
STORMS SOMETIME FRIDAY. THE GFS AND ECMWF ARE A LITTLE STINGY WITH
PRECIPITATION. WOULD EXPECT MOST AREAS TO SEE SOME MOISTURE
BECAUSE OF THE WELL DEFINED SYSTEM. PLAN ON INCREASING POPS FOR
FRIDAY TO SHOW THERE WILL BE A BETTER CHANCE FOR SHOWERS AND
STORMS.

&&

.SHORT TERM...(TODAY THROUGH TONIGHT )
ISSUED AT 301 AM MDT THU AUG 21 2014

A WEAK DISTURBANCE IN SW FLOW ALOFT WAS MOVING ACROSS NERN CO EARLY
THIS MORNING WITH LINGERING SHOWERS AND A FEW STORMS OVER THE FAR
ERN PLAINS.  BY THIS AFTN SOME DRIER AIR WILL MOVE ACROSS THE AREA
WITH SOME WK MID LVL SUBSIDENCE WHICH MAY LOWER TSTM CHANCES ACROSS
THE AREA.  BY THIS EVENING THE GFS SHOWS A WK DISTURBANCE MOVING
OVER THE AREA IN SW FLOW ALOFT WHICH LEADS TO A BETTER CHC OF
CONVECTION IN THE EVENING HOURS OVER THE PLAINS.  ON THE OTHER HAND
THE ECMWF DOES NOT SHOW THIS FEATURE AND HAS NO PCPN OVER THE PLAINS
TONIGHT.  FOR NOW WILL JUST KEEP A SLIGHT CHC OF TSTMS OVER THE
PLAINS FOR TONIGHT.  AS FOR HIGHS 850-700 READINGS CHANGE LITTLE FM
YESTERDAY SO WILL KEEP HIGHS MAINLY IN THE UPPER 80S TO LOWER 90S
ACROSS NERN CO.


.LONG TERM...(FRIDAY THROUGH WEDNESDAY)
ISSUED AT 301 AM MDT THU AUG 21 2014

ON FRIDAY AND FRIDAY NIGHT SOUTHWESTERLY FLOW ALOFT WILL BE OVER
COLORADO WITH A FAIR AMOUNTS OF SUBTROPICAL MOISTURE OVER THE
STATE...AHEAD OF AN UPPER TROUGH NEAR THE FOUR CORNERS REGION. THE
LATEST NAM12 STILL WANTS TO LIFT THIS TROUGH NORTHEAST INTO
COLORADO FRIDAY AFTERNOON AND EVENING. INCREASING INSTABILITY IN
THE AFTERNOON COUPLED WITH WEAK QG ASCENT FM THE TROUGH...WILL
SPAWN THUNDERSTORMS ACROSS THE CWFA...FIRST IN THE MOUNTAINS THEN
ACROSS THE NORTHEAST PLAINS. THE NAM12 FORECAST SOUNDING AT KDEN
IS QUITE MOIST WITH PW VALUES AROUND 1.15 INCHES BUT CAPES ARE
FAIRLY LOW...AROUND 100 J/KG. STORM MOTIONS WILL BE AROUND 20 MPH.
COULD BE FAIRLY DECENT COVERAGE FOR SHOWERS AND SOME TSTMS...BUT
IF THE CAPES ARE LOW THEN THE STORMS MAY BE LESS INTENSE...WITH
BRIEF HEAVY RAIN THE MAIN ISSUE.

BY 12Z SATURDAY...THE FLOW ALOFT WILL WESTERLY. THERE WILL BE SOME
BRIEF SUBSIDENCE BEHIND THE TROUGH AND DRIER...ESPECIALLY IN THE
LOWER LEVELS WITH WLY DOWNSLOPE WINDS IN THE MORNING. SATURDAY
AFTERNOON AND EVENING...ANOTHER SYSTEM WILL DROP OUT OF THE
NORTHERN ROCKIES AND PASS ACROSS WYOMING SATURDAY NIGHT INTO
SUNDAY MORNING. THE FORECAST SOUNDINGS SHOW THE AMS DESTABILIZING
BY LATE IN THE DAY WITH CAPES CLOSE TO 600 J/KG BY 00Z AT DENVER.
PW VALUES WL NOT BE AS HIGH BUT BETTER DIRECTIONAL SHEAR WITH THE
STORMS. LOW LEVEL SELY SFC WINDS WILL DEVELOP IN THE AFTN ALONG
WITH INCREASING SOUTHWESTERLY WINDS ALOFT. A JET MAX IS PROGGED TO
PASS AROUND THE BASE OF THE TROUGH AND ACROSS COLORADO AT THAT
TIME. COULD SEE SOME BANDED UPRIGHT CONVECTION ASSOCIATED WITH
THIS FEATURE. THERE WILL BE A GOOD CHANCE OF TSTMS OVER THE
MOUNTAINS IN THE AFTN AND OVER THE URBAN CORRIDOR AND NORTHEAST
PLAINS SATURDAY NIGHT. WITH THE FLOW ALOFT INCREASING...SOME OF
THE STORMS COULD PRODUCE MORE WIND AS WELL.

ON SUNDAY...THE UPPER TROUGH WL SHIFT TO THE NORTHEAST IN THE
MORNING AND A COLD FRONT WILL SLIP INTO THE URBAN CORRIDOR AND
NORTHEAST PLAINS. AMS MAY BE TOO STABLE FOR TSTMS OVER THE
NORTHEAST PLAINS IN THE AFTN...BUT TSTMS STILL AN ISSUE OVER THE
MOUNTAINS AND PALMER DIVIDE. SUNDAY NIGHT...A DRIER SOUTHWESTERLY
FLOW ALOFT SHOULD HELP TO STABILIZE THE AIRMASS OVERNIGHT.

MONDAY AND TUESDAY WILL REMAIN UNSETTLED. THE MDLS BRING ANOTHER
UPPER TROUGH OUT OF THE NORTHERN ROCKIES MONDAY NIGHT AND MOVE IT
ACROSS NORTHERN COLORADO ON TUESDAY. AS A RESULT IT SHOULD AGAIN
BE COOL WITH ANOTHER FRONT MOVING INTO THE FORECAST AREA ON
TUESDAY. THERE WILL BE ANOTHER CHANCE OF SHOWERS AND TSTMS AS
WELL...WITH THE BEST COVERAGE IN THE HIGH COUNTRY. BY
WEDNESDAY...AN UPPER LEVEL RIDGE MAY FINALLY END MUCH OF THE TSTMS
POTENTIAL OVER CO WITH A DRY AND SUBSIDENT AIRMASS IN PLACE.

&&

.AVIATION...(FOR THE TAFS THROUGH 18Z FRIDAY MORNING)
ISSUED AT 934 AM MDT THU AUG 21 2014

LIGHT WINDS THIS MORNING ARE EXPECTED TO TURN TO THE SOUTHEAST
AFTER 18Z. ANOTHER ROUND OF THUNDERSTORMS IS EXPECT TODAY...WITH
THE BEST CHANCE BEING 23Z TO 04Z. GUSTY OUTFLOW WINDS FROM
THUNDERSTORMS WILL LIKELY CAUSE WINDS TO SHIFT A COUPLE OF TIMES
LATE THIS AFTERNOON AND THIS EVENING. BRIEF HEAVY RAIN WILL ALSO
BE POSSIBLE FROM THE STORMS.

&&

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

$$

UPDATE...MEIER
SHORT TERM...RPK
LONG TERM...COOPER
AVIATION...MEIER


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