Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 172238 CCA
AFDBOU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DENVER/BOULDER CO
438 PM MDT SUN AUG 17 2014

...CORRECTION TO LAST PARAGRAPH OF LONG TERM DISCUSSION...

.SHORT TERM...(THIS EVENING THROUGH MONDAY)
ISSUED AT 245 PM MDT SUN AUG 17 2014

THE CONVECTIVE CLOUDINESS IS MAINLY OVER THE FOOTHILLS...
ADJACENT PLAINS...ALONG WITH PARK AND DOUGLAS COUNTIES. THERE ARE
A FEW MOVING EASTWARD OVER THE FOOTHILLS AND URBAN CORRIDOR. THE
DEW POINTS ARE IN THE MID 30S TO MID 40S F FOR THE PLAINS AND
FOOTHILLS. THE FAR NORTHEAST CORNER STILL HAS SOME MID 40S TO
LOWER 50S F READINGS. THE AIRCRAFT SOUNDINGS SHOW LIMITED CAPE AT
THIS TIME. MODELS SHOW THE UPPER RIDGE AXIS TO SHIFT SLIGHTLY
EASTWARD OVERNIGHT AND MONDAY. THE FLOW ALOFT WILL BECOME MORE
WEST-NORTHWESTERLY OVERNIGHT INTO MONDAY. THE SYNOPTIC SCALE
ENERGY REMAINS BENIGN THE NEXT TWO PERIODS. FOR MOISTURE...IT WILL
REMAIN LIMITED THROUGH MONDAY AFTERNOON. PRECIPITABLE WATER VALUES
ARE IN THE 0.50 INCH RANGE OVER THE HIGH FOOTHILLS TO 1.00 INCH
OVER THE EASTERN PLAINS MONDAY AFTERNOON. MONDAY AFTERNOON`S DEW
POINTS ARE PROGGED IN THE LOWER 40S TO LOWER 50S FOR THE PLAINS
AND FOOTHILLS. MONDAY AFTERNOON`S CAPE VALUES ARE IN THE 500-1500
J/KG RANGE THROUGHOUT THE CWA. THE QPF FIELDS FROM THE GFS ONLY
HAVE A TINY BIT OF MEASURABLE RAINFALL PROGGED TONIGHT. THERE IS
SOME MEASURABLE RAINFALL PROGGED ON MOST OF THE MODELS FOR MONDAY
AFTERNOON...THE MOST OVER THE SOUTHERN HALF OF THE CWA. FOR POPS
...10-20%S OVER THE SOUTHERN CWA EARLY THIS EVENING. FOR MONDAY
AFTERNOON...10-20%S FOR MOST AREAS. TEMPERATURES LOOK TO BE
0.5-1.5 C COOLER MONDAY AFTERNOON THEN CURRENT READINGS.

.LONG TERM...(MONDAY NIGHT THROUGH SUNDAY)
ISSUED AT 245 PM MDT SUN AUG 17 2014

LARGE UPPER RIDGE OVER COLORADO MONDAY NIGHT SHIFTS EAST OF THE
STATE ON TUESDAY AND CONTINUES ITS EASTWARD PROGRESSION OVER THE
CENTRAL GREAT PLAINS ON WEDNESDAY. WITH ITS PASSING...MEAN 0-5KM AGL
FLOW ACRS COLORADO TURN SOUTHWESTERLY...WHICH DRAWS MONSOONAL/
SUBTROPICAL MOISTURE UP FROM THE DESERT SOUTHWEST. MEANWHILE...AN
UPPER AIR CYCLONE SPINNING OFF THE WASHINGTON COAST TODAY IS PROGGED
TO MIGRATE SOUTHWARD EXPANDING INTO A DEEP UPPER TROUGH/CLOSED LOW
OVER CNTRL CALIFORNIA AND WESTERN NEVADA BY TUESDAY. MODELS SHOW A
COUPLE OF ENERGY SPOKES ROUNDING THE BASE OF THE TROUGH AND LIFTING
NEWRD OVER THE FOUR CORNERS REGION. THEY SHOW THE FIRST AND STRONGER
OF THESE SPOKES/SHORTWAVES ON THE NOSE OF AN +80KT JET PASSING OVER
N-CNTRL/NERN COLORADO TUESDAY AFTERNOON WITH YET A SECOND MUCH LESS
ORGANIZED WAVE PASSING WEDNESDAY EVENING. MID/UPPER-LEVEL QG
VERTICAL VELOCITY FIELDS INDICATE THE BEST LIFT OVER THE NERN CORNER
OF COLORADO AROUND 00Z/WED WHERE LAYER PW VALUES FCST TO BE IN THE
1.0 TO 1.3 INCH RANGE. AHEAD THIS SHORTWAVE...SHEAR AND STABILITY
PROFILES LOOKS SUITABLE FOR ISOLATED TO WIDELY SCATTERED STORMS ONCE
THE CIN DISAPPEARS ABOUT 21Z ACCORDING TO MODEL SOUNDINGS. ONE OR
TWO STORMS IN THIS AREA MAY PRODUCE HAIL AND LOCALLY HEAVY RAINFALL.
BY EVENING SWLY BNDRY LAYER FLOW DEVELOPS AND BEGINS FLUSHING OUT LOW-
LEVEL MOISTURE ALONG THE FRONT RANGE. THIS SHOULD CAUSE A QUICK WEST-
TO-EAST END TO STORM ACTIVITY ON THE PLAINS. WHEREAS ISOLATED
SHOWERS/STORMS COULD LINGER IN THE HIGH COUNTRY THRU MID-EVENING
WITH THE MID-LEVEL MOISTURE PLUME STILL HANGING OVER THE AREA.

ON WEDNESDAY...MEAN 0-5KM FLOW TURNS MORE WESTERLY WHICH FURTHER
DRIES OUT THE BOUNDARY LAYER EAST OF THE MTNS. PW VALUES ALONG THE
FRONT RANGE START OUT AROUND AN INCH AND PRESUMABLY FALL TO AROUND
3/4 INCH BY EVENING. THAT/S EVEN WITH MID- AND HIGH-LEVEL MOISTURE
PLUME STILL OVER THE AREA JUST AHEAD OF THE WEAK SHORTWAVE. CAN SEE
SCATTERED TO BROKEN CLOUD COVER AND AT LEAST A SLIGHT CHANCE OF
AFTERNOON AND EVENING T-STORMS ON WEDNESDAY. DOWNSLOPE FLOW OFF THE
FRONT RANGE/PALMER DIVIDE WILL HELP TO WARM TEMPERATURES 1-2 DEG C.

BY THURSDAY...THE LARGE SCALE HEIGHT AND CIRCULATION PATTERN OVER
THE WESTERN CONUS BEGINS TO MOVE. GFS SHOWS THE 500MB TROUGH OVER
THE WEST COAST OPENING UP AND MOVING EAST ACRS THE GREAT BASIN...
WITH AN EVEN STRONGER SWLY FLOW OVER COLORADO. THIS KEEPS THE
AIRMASS OVER THE AREA RELATIVELY MOIST AND UNSTABLE. WHEREAS THE
ECMWF INDICATES MORE OF A SPLIT FLOW PATTERN. IT/S FORECASTING THE
WEST COAST LOW TO DROP FARTHER SOUTH OFF OF SRN CALIFORNIA AND THE
OPEN WAVE TROUGH OVER THE PACIFIC NORTHWEST TO RACE EAST OVER THE
NRN ROCKIES. THIS PLACES NERN COLORADO UNDER A NEARLY ZONAL FLOW
ALOFT LEADING TO FURTHER DRYING. CANADIAN AND DGEX MODELS LOOK
SOMEWHAT SIMILAR TO THE EC. SO SLIDING WITH THE MAJORITY...WILL
TREND DRIER AND WARMER ON THURSDAY.

FRIDAY-SUNDAY...GFS MOVES THE UPPER TROUGH EAST OF COLORADO ON
FRIDAY WHILE THE OTHER MODELS STILL HAVE THE FCST AREA UNDER A
RELATIVELY DRY ZONAL FLOW. OVER THE WEEKEND...MODELS SHOW ANOTHER
BROAD TROUGH AND COOL AIRMASS SWINGING OUT OF SWRN CANADA. THE GFS
KEEPS THIS TROUGH NORTHWEST OF COLORADO THROUGH SUNDAY...WHILE THE
ECMWF RACES IT EASTWARD ACRS MONTANA...WYOMING AND NRN COLORADO.
THE SLOWER GFS SHOWS MONSOON MOISTURE SURGING NORTHWARD AGAIN OVER
COLORADO THIS WEEKEND WHILE THE EC SHOWS THE MONSOON PLUME REMAINING
WELL SOUTH OF THE STATE. FOR THIS 3-DAY PERIOD...WILL GO WITH LOW
POPS MAINLY OVER THE HIGH COUNTRY...AND TEMPERATURES NEAR TO
SLIGHTLY BELOW AVERAGE.

&&

.AVIATION...(FOR THE TAFS THROUGH 00Z MONDAY LATE AFTERNOON)
ISSUED AT 245 PM MDT SUN AUG 17 2014

THERE IS A PRETTY DECENT...ALTHOUGH SMALL...CELL TO MOVE JUST
SOUTH OF DIA THE NEXT HALF HOUR. NORMAL DIURNAL WIND PATTERNS
SHOULD PREVAIL TONIGHT AND MONDAY...AFTER THE STORM OUTFLOWS MOVE
AWAY. CEILINGS SHOULD STAY ABOVE 6000 FEET AGL EVEN WITH THE
STORM ALTHOUGH OUTFLOW WIND GUSTS COULD GET TO 35 KNOTS.

&&

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

$$

SHORT TERM...RJK
LONG TERM...BAKER
AVIATION...RJK


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