Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 011657
AFDBOU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DENVER/BOULDER CO
1057 AM MDT FRI AUG 1 2014

.UPDATE...
ISSUED AT 1053 AM MDT FRI AUG 1 2014

ONLY MINOR CHANGES TO DEW POINT AND SKY GRIDS THIS MORNING...NO
NEED TO UPDATE THE PUBLIC ZONES. PLAINS GENERALLY CAPPED WHILE
MOUNTAIN CONVECTION SHOULD SHOW A SIMILAR PATTERN TO YESTERDAY.

&&

.SHORT TERM...(TODAY THROUGH TONIGHT )
ISSUED AT 230 AM MDT FRI AUG 1 2014

WK NLY FLOW ALOFT WILL BE OVER NRN CO AS A DISTURBANCE TRACKS
SLOWLY ACROSS WRN CO. OVERALL BEST MOISTURE WILL REMAIN OVER THE
MTNS AND STN FOOTHILLS WITH A DRIER AIRMASS OVER MOST OF NERN CO.
WILL MENTION SCT AFTN STORMS IN THE MTNS...SRN FOOTHILLS AND OVER
SOUTH PARK. ALONG THE FRONT RANGE AND OVER THE PALMER DIVIDE WILL
KEEP POPS IN THE ISOLD-WDLY SCT RANGE. AFTN HIGHS WILL CONTINUE TO
SLOWLY RISE WITH READINGS IN THE 80S OVER NERN CO.

FOR TONIGHT TSTM ACTIVITY SHOULD GRADUALLY END DURING THE EARLY
EVENING HOURS WITH ONLY A SLIGHT CHC OF SHOWERS IN THE MTNS AFTER
MIDNIGHT.

.LONG TERM...(SATURDAY THROUGH THURSDAY)
ISSUED AT 230 AM MDT FRI AUG 1 2014

MODELS SHOW A TALL UPPER LEVEL RIDGE RESTING OVER THE GREAT BASIN
AND ROCKY MOUNTAIN REGIONS THIS WEEKEND AS AN UPPER TROUGH
BROADENS AND DEEPENS OVER THE NORTHEAST PACIFIC/GULF OF ALASKA.
MODEL CONSENSUS HAS THE 500 MB RIDGE AXIS STAYING WEST OF THE
CONTINENTAL DIVIDE THIS WEEKEND. SUBSIDENCE AND WARMING ALOFT
SHOULD RESULT IN DRIER AND WARMER CONDITIONS FOR AREAS MAINLY EAST
OF THE MTNS. A WARM SOUTHERLY BOUNDARY LAYER FLOW WILL ALSO WARM
TEMPERATURES TO READINGS NEAR TO SLIGHTLY ABOVE AVERAGE SEASONAL
NORMS. WITH THE UPPER RIDGE CENTERED OVER THE COLORADO...THE
SUBTROPICAL MOISTURE PLUME SHOULD DEFLECT WESTWARD AWAY FROM
COLORADO AND UP OVER THE GREAT BASIN. ALTHOUGH SOME OF THIS
MONSOON MOISTURE MAY BACK INTO COLORADO AS FAR EAST AS THE FRONT
RANGE MOUNTAINS...PARTICULARLY ON SUNDAY. THUS A CHANCE OF
THUNDERSTORMS WILL REMAIN IN THE FORECAST FOR THE MTNS AND HIGH
VALLEYS WEST OF THE DIVIDE BOTH DAYS. MEANWHILE T-STORM CHANCES
EAST OF THE MTNS APPEARS QUITE LOW /LESS THAN 10 PERCENT/. SHOULD
ANY STORMS FORM THEY SHOULD REMAIN CONFINED TO THE HIGHER TERRAIN
ALONG THE PALMER DIVIDE...AIDED BY SOUTHEASTERLY UPSLOPE FLOW AND
STEEP LATE DAY LAPSE RATES. ANY PRECIP SHOULD GENERALLY BE LIGHT.

BY SUNDAY NIGHT ATTENTION TURNS TO A DEVELOPING MID-LEVEL CYCLONE/
SHORTWAVE TROUGH OVER THE LOWER DESERT SOUTHWEST WHICH MODELS SHOW
MOVING UP THE WEST SIDE THE UPPER RIDGE. MODELS SHOW THIS
PERTURBATION PASSING OVER ERN NEVADA/WRN UTAH MONDAY MORNING...THEN
OVER NRN UTAH/WRN WYOMING MONDAY NIGHT...AND EVENTUALLY OVER ERN
WYOMING/NERN COLORADO BY LATE ON TUESDAY AS IT ROUNDS THE TOP OF
THE UPPER RIDGE. MODELS DIFFER SOME AS TO THE EXACT LOCATION AND
AMPLITUDE OF THIS FEATURE...BUT ALL INDICATE AN INCREASE IN DEEP
LAYER MOISTURE...INSTABILITY AND SHEAR OVER THE CWA LEADING TO A
GREATER RISK OF T-STORMS TUESDAY AFTERNOON AND EVENING. AT THE
PRESENT TIME...IT APPEARS THE BEST SHEAR...LOW LEVEL MOISTURE AND
AND INSTABILITY FOR ISOLATED SVR T-STORMS WILL BE FOUND ACRS THE
NORTHEAST CORNER OF THE STATE. HOWEVER SHOULD LOW-LEVEL WINDS
TURN MORE EASTERLY AS THE GFS IS HINTING AT...COULD SEE SOME OF
THIS ACTION CLOSER TO THE FRONT RANGE.

AS THE SHORTWAVE TROUGH PASSES TUESDAY NIGHT...BY A WEAK COLD
FRONT DROPS SOUTH OUT OF WYOMING RESULTING IN COOLER TEMPERATURES
ON WEDNESDAY...POSSIBLE AS MUCH AS 5-8 DEG F COOLER ON THE
PLAINS. GFS AND DGEX ALSO INDICATE ANOTHER ROUND OF RELATIVELY
MOIST UPSLOPE FLOW EAST OF THE MTNS. HIGHS ON THE PLAINS
WEDNESDAY MAY NOT GET OUT OF THE 70S. HOWEVER THE ECMWF DOES NOT
LOOK AS COOL NOR AS WET. FOR NOW...WILL TREND TOWARDS THE GFS/DGEX
SOLUTIONS BASED ON THEIR RECENT PERFORMANCE. THAT SAID...THURSDAY
MAY NOT BE ALL THAT MUCH WARMER OR DRIER AS YET ANOTHER COOL AND
MOIST UPPER TROUGH TAKES SHAPE OVER THE WESTERN CONUS AND AS
SUBTROPICAL MOISTURE CONTINUES TO STREAM IN FROM OFF THE BAJA
PENINSULA. NEXT WEEK/S WEATHER JUST PLAIN LOOKS UNSETTLED.

&&

.AVIATION...(FOR THE TAFS THROUGH 18Z SATURDAY MORNING)
ISSUED AT 1053 AM MDT FRI AUG 1 2014

VFR THROUGH TONIGHT. ISOLATED SHOWERS AND THUNDERSTORMS MAINLY
SOUTH AND WEST OF DENVER...JUST A SLIGHT CHANCE OF A PERIOD OF
VARIABLE WINDS TO 25 KNOTS.

&&

.HYDROLOGY...
ISSUED AT 230 AM MDT FRI AUG 1 2014

THERE WILL BE A CHANCE OF AFTERNOON THUNDERSTORMS OVER THE MOUNTAINS
AND SOUTHERN FOOTHILLS WITH ONLY A SLIGHT CHANCE OVER THE URBAN
CORRIDOR AND PALMER DIVIDE.  RAINFALL AMOUNTS WILL GENERALLY BE ONE
HALF INCH OR LESS.

TUESDAY AND WEDNESDAY TURN COOLER AND WETTER WITH THUNDERSTORMS
ON TUESDAY POSSIBLY GENERATING LOCALLY HEAVY RAINFALL DURING THE
LATE AFTERNOON AND EVENING HOURS. DIFFICULT TO SAY EXACTLY WHERE
THIS MAY OCCUR...BUT WITH A MOIST UPSLOPE IN PLACE..IT IS MORE
LIKELY THE HEAVIER RAINFALL IS OCCUR OVER AND NEAR THE FRONT RANGE.
IT IS STILL TOO EARLY TO KNOW IF THIS WILL RESULT IN ANY FLASH
FLOODING.

&&

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

$$

UPDATE...GIMMESTAD
SHORT TERM...RPK
LONG TERM...BAKER
AVIATION...GIMMESTAD
HYDROLOGY...BAKER/RPK


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