Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 230257
AFDBOU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DENVER/BOULDER CO
857 PM MDT MON SEP 22 2014

.UPDATE...
ISSUED AT 857 PM MDT MON SEP 22 2014

THUNDERSTORMS WITH HEAVY RAIN STILL IMPACTING FAR EAST CENTRAL
COLORADO FROM SOUTHEAST WASHINGTON COUNTY INTO NORTHERN LINCOLN
COUNTY. AREAL FLOOD WARNING FOR THE SOUTHEAST TWO THIRDS OF
WASHINGTON COUNTY WILL CONTINUE INTO EARLY MORNING HOURS WITH A
GOOD 1-3 INCHES OF RAIN AND UP TO AN INCH MORE BEFORE DECREASING
THROUGH 10 PM. OTHERWISE CONVECTION HAS REALLY SETTLED DOWN IN
SLOWLY DRYING AND SUBSIDENT AIRMASS LATE THIS EVENING. WILL HAVE
SOME LOW POPS FOR A FEW SHOWERS LINGERING IN THE HIGH COUNTRY BUT
EVEN THOSE SHOULD BE MOSTLY OVER BY MIDNIGHT. DEPENDING ON
CLEARING LATER TONIGHT...SHOULD SEE SOME PATCHY FOG DEVELOPING IN
THE HIGH MOUNTAIN VALLEYS.

&&

.SHORT TERM...(THIS EVENING THROUGH TUESDAY)
ISSUED AT 140 PM MDT MON SEP 22 2014

UPPER LOW WILL MOVE ACROSS WYOMING THROUGH TONIGHT AS THE
SOUTHERN EXTENT OF THE LOW SWEEPS ACROSS NORTHERN COLORADO. THERE
IS A 60KT JET STREAK ASSOCIATED WITH THE WAVE ACROSS NORTHWEST
COLORADO AND THIS IS AIDING THUNDERSTORM DEVELOPMENT EARLY THIS
AFTERNOON. MODEL QG FIELDS SHOWING WEAK ASCENT THROUGH THIS
EVENING THEN GRADUALLY SUBSIDENCE MOVES IN LATER TONIGHT AND
TUESDAY AS AIRMASS DRIES.

A LINE OF SHOWERS AND THUNDERSTORMS ARE MOVING INTO THE FRONT
RANGE EARLY THIS AFTERNOON AND WILL CONTINUE TO SPREAD EASTWARD
ONTO THE PLAINS DURING THE AFTERNOON. STORMS WILL GATHER STRENGTH
AS THEY MOVE EASTWARD INTO AREA WITH BETTER SHEAR AND MOISTURE.
GIVEN DEWPOINTS NOW IN THE 50S ACROSS MUCH OF THE PLAINS...SURFACE
BASED CAPES INCREASING TO 1000-1500J/KG. STILL A GRADUAL LACK OF
STRONG HEATING WILL KEEP MOST STORMS UNDER SEVERE LIMITS.
HOWEVER...GIVEN BETTER SHEAR PROFILE FURTHER EAST...MIGHT SEE AN
ISOLATED SEVERE STORM.

BEHIND THE TROF LATER TNT...A BIT OF MOUNTAIN WAVE DEVELOPS WITH
SOME DOWNSLOPE WINDS DEVELOP OVER THE FRONT RANGE. WILL INDICATED
SOME CLOUDS AND WINDS WITH THIS FEATURE. FOR TUESDAY
AFTERNOON...LIMITED MOISTURE AND INSTABILITY MAY BE ENOUGH TO
DEVELOP A FEW SHOWERS OVER MOUNTAINS AND HIGHER TERRAIN.
TEMPERATURES WILL BE WARMER ON TUESDAY WITH MORE SUNSHINE
AVAILABLE.

.LONG TERM...(TUESDAY NIGHT THROUGH MONDAY)
ISSUED AT 140 PM MDT MON SEP 22 2014

UPPER TROUGH CONTINUES TO SLIDE EAST AWAY FROM THE
COLORADO FRONT RANGE TUESDAY NIGHT AS AN UPPER RIDGE BUILDS TO OUR
SOUTHWEST. A DRIER AND WARMER NORTHWEST FLOW ALOFT MOVES OVER THE
AREA OVERNIGHT AND WEDNESDAY AS THE UPPER RIDGE REACHES
NORTHEASTWARD ACROSS COLORADO AND NORTHERN GREAT PLAINS. THERE IS
STILL AN OUTSIDE CHANCE THAT STRONG DAYTIME HEATING AND A MODESTLY
MOIST SELY LOW-LEVEL FLOW COULD SPARK A FEW STRAY SHOWERS OR T-
STORMS OVER THE HIGHER TERRAIN IN JEFFERSON...DOUGLAS...PARK AND
SUMMIT COUNTIES LATE ON WEDNESDAY. OTHERWISE A DRY AND VERY WARM DAY
ON TAP FOR EVERYWHERE ELSE. TEMPERATURE GUIDANCE INDICATES HIGHS
GENERALLY 6-12F ABOVE AVERAGE ON WEDNESDAY. CAN/T ARGUE WITH THAT.
THE UNSEASONABLY WARM AND DRY WEATHER IS LIKELY TO PERSIST THROUGH
THURSDAY AS THE CORE OF A 591 DECAMETER HIGH TRACKS NORTHEASTWARD
ACRS THE STATE. THURSDAY APPEARS EVEN DRIER AND SLIGHTLY WARMER
ACCORDING TO THE GFS AND ECMWF WITH STRONG MID-LEVEL SUBSIDENCE.
WHEREAS THE NAM SHOWS THIS WARM CORE RIDGE CLOSING OFF NORTHEAST OF
COLORADO DURING THE DAY. THIS OPENS THE DOOR TO A BATCH OF
SUBTROPICAL MOISTURE POOLING OVER ERN ARIZONA/WRN NEW MEXICO. NAM
SHOWS SOME OF THIS MOISTURE MEANDERING NWRD UP ALONG THE SPINE OF
THE ROCKIES AND OVER SWRN PORTION OF THE FCST AREA BY THURSDAY
AFTERNOON. NAM INDICATES POCKETS OF LIGHT QPF IN THIS AREA. THE
LATEST RUN OF THE CANADIAN MODEL LOOKS ABOUT THE SAME...ALTHOUGH IT
KEEPS THE PRECIP SOUTH OF THE CWA ON THURSDAY.

ON FRIDAY...THE UPPER RIDGE CLOSES OFF AS IT CONTINUES ITS
NORTHEASTWARD MIGRATION OVER THE NRN GREAT PLAINS/SRN CENTRAL
CANADA. FLOW ALOFT OVER COLORADO BECOME PREDOMINANTLY SWLY IN
ADVANCE OF A DEEPENING UPPER TROUGH PLOWING INTO THE WEST COAST. GFS
SHOWS SUBTROPICAL MOISTURE POOLED OVER ARIZONA/NEW MEXICO AT THAT
TIME SPREADING NWRD OVER ERN UTAH AND WRN/SWRN COLORADO DURING THE
DAY. WHILE AREAS EAST OF THE MTNS APPEAR TO REMAIN DRY. MODEL
GUIDANCE CONTINUES AN UPWARD TREND IN TEMPERATURES ON FRIDAY.
HOWEVER SHOULD THIS MOISTURE/CLOUD COVER ARRIVE EARLIER THAN
PREDICTED...TEMPS MAY NOT GET AS WARM AS THOSE ON THURSDAY.

OVER THE WEEKEND...MOISTURE SPREADS NORTHWARD FROM THE DESERT
SOUTHWEST IN ADVANCE OF A DEEP UPPER TROUGH WHICH THE GFS SHOWS
CLOSING OFF OVER SRN IDAHO/NRN UTAH BY SUNDAY. EARLIER MODEL RUNS
SHOWED THIS HAPPENING FARTHER SOUTH OVER SOUTH CENTRAL PORTIONS OF
THE GREAT BASIN AND ABOUT 12 HRS EARLIER. AT ANY RATE...DURING THE
WEEKEND SHOULD SEE A GRADUAL TREND TOWARDS COOLER AND WET CONDITIONS
BEGINNING IN THE MTNS AND HIGH VALLEYS ON SATURDAY AND OUT ACRS THE
PLAINS OF NERN COLORADO ON SUNDAY. BY EARLY NEXT WEEK...MODELS SHOW
THE CLOSED UPPER LOW LIFTING NERWD OVER THE NRN ROCKIES/NRN GREAT
PLAINS WHICH POSITIONS A SWATH OF DRY...STABLE AIR OVER OUR FCST
AREA. DETAILS REMAIN FUZZY THAT FAR OUT. SO WILL GO WITH A SLIGHT
CHANCE OF PRECIP MAINLY FOR THE MTNS AND HANG ONTO THE NEAR SEASONAL
TEMPERATURES OFFERED BY MODEL GUIDANCE.

&&

.AVIATION...(FOR THE TAFS THROUGH 06Z TUESDAY EVENING)
ISSUED AT 857 PM MDT MON SEP 22 2014

THUNDERSTORM THREAT HAS ENDED AT KDEN AND THE FRONT RANGE AIRPORTS.
MID LEVEL CLOUD DECK STILL SCT-BKN BUT EVEN THAT SHOULD GRADUALLY
BREAK THROUGH THE REST OF THE NIGHT. VFR CONDITIONS WILL PERSIST
WITH NORMAL DRAINAGE WINDS TONIGHT...THEN SHIFTING WEST/NORTHWEST
BY 18Z-20Z TUESDAY.

&&

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

$$

UPDATE...BARJENBRUCH
SHORT TERM...ENTREKIN
LONG TERM...BAKER
AVIATION...BARJENBRUCH



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