Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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000
FXUS65 KBOU 182158
AFDBOU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DENVER/BOULDER CO
358 PM MDT MON AUG 18 2014

.SHORT TERM...(THIS EVENING THROUGH TUESDAY)
ISSUED AT 355 PM MDT MON AUG 18 2014

BANDS OF CONVECTION HAVE DEVELOPED WITH A LITTLE HELP FROM A JET
STREAK OVER NORTHERN COLORADO. BEST DEVELOPED AREA WILL SHIFT FROM
THE CENTRAL MOUNTAINS OVER THE PALMER DIVIDE AREA...BUT THE
EXPECTED CHEYENNE RIDGE CONVECTION IS STARTING TO DEVELOP NOW AND
WILL MOVE ACROSS THE NORTHEAST PART OF THE STATE. WE ALREADY HAD
THE NORTHEAST AREA FAVORED...ADDED A BIT TO THE POPS FOR THE
PALMER DIVIDE AREA. MOISTURE ON THE PLAINS HAS MIXED OUT A BIT...
BUT STILL ABOUT 1000 J/KG OF CAPE TO WORK WITH AND ABOUT 30 KNOTS
OF 0-6 KM SHEAR. EXPECT THAT MOST OF THE CONVECTION WILL BE PRETTY
UPRIGHT...BUT STILL A SMALL THREAT OF SEVERE HAIL AND WIND WITH
THE STRONGEST PULSES OR IF A LINE GETS ORGANIZED ENOUGH.

MAIN AREA OF LIFT SHOULD MOVE EAST OF THE STATE BY MIDNIGHT...SOME
CLOUDS REMAINING BUT RELATIVELY QUIET. STRONGER LIFT AND BETTER
MOISTURE ROTATING AROUND THE RIDGE AXIS WILL MOVE UP INTO WESTERN
COLORADO IN THE MORNING...THEN INTO NORTHEASTERN COLORADO BY
TUESDAY EVENING. WE WILL HAVE SOME WARMING ALOFT ALONG WITH THE
MOISTENING...SO ACROSS THE MOUNTAINS AND THE FRONT RANGE AREAS IT
MAY NOT BE MUCH MORE UNSTABLE. STILL EXPECTING HIGHER COVERAGE OF
STORMS TUESDAY BUT NOT NECESSARILY MORE INTENSE. ON THE PLAINS
THERE WILL BE RICHER LOW LEVEL MOISTURE...MODELS HINTING AT CAPES
IN THE 1500-2500 J/KG RANGE. PROBABLY CAPPED UNTIL LIFT OR OUTFLOW
BOUNDARIES ARRIVE FROM THE WEST IN THE LATE AFTERNOON OR EVENING.
STILL NOT A LOT OF SHEAR...BUT DEFINITELY SOME SEVERE THREAT ON
THE PLAINS LATE IN THE DAY.

.LONG TERM...(TUESDAY NIGHT THROUGH MONDAY)
ISSUED AT 355 PM MDT MON AUG 18 2014

CIRCULATION ABOUT THE UPPER TROUGH ALONG THE WEST COAST AND UPPER
RIDGE OVER THE CENTRAL AND SOUTHERN GREAT PLAINS WILL STREAM LOW AND
MID-LEVEL SUBTROPICAL MOISTURE NORTHWARD UP OVER UTAH AND WESTERN
COLORADO TUESDAY NIGHT. SOME OF THIS MOISTURE MAY MAKE IT EAST OF
THE MTNS AND WITH S-SELY BNDRY LAYER FLOW ON THE PLAINS CYCLONE THIS
MOISTURE UP INTO THE FRONT RANGE FOOTHILLS DURING THE EVENING HOURS.
IN ADDITION...MODELS SHOW A WEAK UPPER AIR DISTURBANCE OVER THE 4-
CORNERS AREA DURING THE AFTERNOON AND PASSING OVER NORTHEAST
COLORADO DURING THE EVENING HOURS...PROVIDING ADDITIONAL LIFT FOR
ISOLATED TO SCATTERED STORMS. MODELS SHOWING BEST CAPE...SHEAR AND
MOISTURE CONVERGING ON THE NERN CORNER OF THE FCST AREA. AT
00Z/WED...NAM INDICATES OVER 2500 J/KG OF SFC BASED CAPE IN THE
CORNER COUNTIES. WHILE THE ECMWF SHOWS ABOUT 1500 J/KG OF CAPE
AND SLIGHTLY LESS THETA-E...AND THE GFS EVEN LESS CAPE AND
MOISTURE AT THAT TIME. THESE LAST TWO MODELS SHOW THE MORE
FAVORABLE STORM BUILDING CONDITIONS DURING THE MID TO LATE
AFTERNOON HOURS. WILL STICK WITH SCATTERED POPS IN THE MTNS AND
ACROSS THE NORTHEAST CORNER OF THE STATE...AND ISOLATED POPS ALONG
THE BASE OF THE FRONT RANGE DURING THE EVENING HOURS...THEN
QUICKLY LOWER POPS REST OF THE NIGHT WITH DRIER POST-TROUGH AIR
MIXING DOWN OUT OF THE MTNS.

ON WEDNESDAY...THE GREAT BASIN TROUGH AND GREAT PLAINS RIDGE
CONTINUE THEIR SLOW EASTWARD MIGRATION CAUSING THE MONSOON MOISTURE
PLUME TO ALSO SHIFT EAST PLACING SQUARELY OVER COLORADO. HOWEVER...
MODELS INDICATE DRYING WITHIN THE PLUME...PARTICULARLY BELOW 500 MBS
WITH THE 0-5KM FLOW VEERING FROM SOUTHERLY TO WEST-SOUTHWESTERLY
THROUGH THE DAY. PRECIPITABLE WATER VALUES STILL REMAIN HIGH...
GENERALLY IN THE 0.75-0.90 RANGE ON THE PLAINS. SO WITH HEATING AND
THE AVAILABLE MOISTURE...SHOULD SEE ANOTHER ROUND OF STORMS BUT WITH
LESS COVERAGE...ESPLY EAST OF THE MTNS. SHOULD SEE AN END TO THIS
CONVECTIVE ACTIVITY OVERNIGHT...THOUGH A FEW SHOWERS/STORMS MAY
LINGER OVERNIGHT IN THE HIGH COUNTRY WITH THE PLUME HANGING OVER THE
AREA.

ON THURSDAY AND FRIDAY...THE UPPER TROUGH OUT WEST IS PROGGED TO
PASS OVER COLORADO DURING THIS PERIOD. THE GFS SHOWS A DEEPER...
WETTER AND A FASTER MOVING TROUGH...WHILE THE ECMWF A SLOWER...LESS
WET AND LESS AMPLIFIED TROUGH. THE CANADIAN GEM IS IN BETWEEN THE
TWO. WILL GO WITH A BLEND HERE AND HANG ON TO A SLIGHT CHANCE OF
AFTERNOON AND EVENING STORMS ON THE PLAINS AND SOMEWHAT BETTER
CHANCES FOR STORMS IN THE HIGH COUNTRY.

OVER THE WEEKEND...MEDIUM RANGE MODELS GENERALLY AGREE THAT A BROAD
UPPER TROUGH WILL FORM OVER AND NORTH OF THE WRN U.S./WRN CANADIAN
BORDER EARLY IN THE WEEKEND. FROM THERE THE GFS DIGS THE TROUGH AND
A GOOD BATCH OF ABNORMALLY COOL CANADIAN AIR SOUTHWARD ALONG THE
SPINE OF THE NORTHERN/CENTRAL ROCKIES. WHEREAS THE ECMWF DOES NOT
SHOW A TROUGH AS AMPLIFIED AND MUCH OF THIS COOL AIR SLUFFING OFF
TOWARDS THE DAKOTAS. BASED ON THE GFS...COULD SEE A BIG JUMP IN
CLOUD COVER AND STORMS OVER NERN COLORADO LATE SUNDAY AND MONDAY.
THE ECMWF...NOT SO MUCH. ONCE AGAIN WILL GO WITH A BLEND OF THE TWO
MODELS AND COME UP WITH THE FCST FOR SUNDAY AND MONDAY.

&&

.AVIATION...(FOR THE TAFS THROUGH 00Z TUESDAY LATE AFTERNOON)
ISSUED AT 355 PM MDT MON AUG 18 2014

VFR THROUGH TUESDAY. ISOLATED THUNDERSTORMS WILL GIVE A CHANCE OF
A WIND SHIFT OR TWO THROUGH EARLY THIS EVENING...BUT LITTLE OTHER
IMPACT IS EXPECTED. ON TUESDAY AFTERNOON THERE WILL BE GREATER
STORM COVERAGE...GREATER THREAT OF WIND SHIFTS AND A CHANCE OF
NEEDING INSTRUMENT APPROACHES TO KDEN AFTER 21Z.

&&

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

$$

SHORT TERM...GIMMESTAD
LONG TERM...BAKER
AVIATION...GIMMESTAD



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