393
FXUS65 KBOU 040941
AFDBOU
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DENVER CO
340 AM MDT SAT JUL 4 2009
SHORT TERM
MOST OF THE CONVECTION IS DIMINISHING ATTM AS A WEAK
FRONTAL BOUNDARY LAST EVENING SPARKED ADDITIONAL STORMS ALONG THE
FRONT RANGE AROUND MIDNIGHT. UPSLOPE FLOW HAS DEEPENED TO AROUND
700MB...PER PLATTEVILLE PROFILER AND KFTG VAD WINDS. THIS HAS ALSO
LED TO SOME STRATUS WHICH HAS DEVELOPED IN THE WAKE OF THE
STORMS...MAINLY ALONG THE FOOTHILLS AND ACROSS DOUGLAS COUNTY.
PRECIPITABLE WATER TRENDS ALSO HAVE INCREASED IN THE WAKE OF THE
DEEPENING UPSLOPE FLOW AS VALUES ARE NOW AT/JUST ABOVE AN INCH BASED
ON THE PW TRENDS FROM GPS. LOW LVL MOISTURE VALUES HAVE ALSO BEEN
REPLENISHED WITH DEWPOINTS IN THE MID 50S TO LOWER 60S ACROSS ALL OF
NERN CO. LOOKS LIKE WE'LL HAVE TO HOLD ONTO ISOLD POPS EVEN THIS
MORNING AS CONTINUED SHOWERS ARE RE-GENERATING OVER THE NRN
MOUNTAINS IN VICINITY OF THE 70KT JET STREAK RIDING ACROSS SRN
WYOMING. APPEARS ANOTHER WAVE IS SITUATED ACROSS EASTERN NEVADA AND
WESTERN UTAH WITH CONSIDERABLE AMOUNTS OF LIGHTNING STILL ONGOING AT
THIS HOUR AND ANOTHER WAVE ACROSS SOUTHERN OREGON. THIS WILL LEAD
TO ANOTHER ROUND OF STORMS FOR SATURDAY AFTN AND INTO THE EVENING
HOURS ACROSS MUCH OF THE CWA...ESP MOUNTAINS AND ADJACENT PLAINS.
FORECAST SOUNDINGS INDICATE CAPE VALUES OF 800-1200J/KG ACROSS THE
FRONT RANGE GIVEN TEMPS IN THE UPPER 70S AND DEWPOINTS IN THE LOWER
TO MID 50S. CAPES A BIT LOWER FURTHER EAST WITH A BIT MORE STABILITY
IN PLACE. FREEZING LVLS ALSO A LOWER TODAY...WHILE EXITING 80KT JET
STREAK WILL PUT NERN CO IN FAVORABLE ASCENT REGION OF JET. GIVEN
DECENT 35-40KT MID LVL FLOW...EXPECT SOME STORMS MAY BECOME SEVERE
THIS AFTN OVER THE FRONT RANGE WITH HAIL UP AROUND AN INCH IN
DIAMTER AND DAMAGING WINDS. SPC HAS ALSO TARGETED HIS AREA AND LOOKS
REASONABLE. GIVE PW VALUES OVER AN INCH THIS AFTN...HEAVY RAINERS AS
WELL BUT STORM MOTIONS OF 10-15KT SHOULD BE ENOUGH TO KEEP STORMS
MOVING. FLOOD POTENTIAL AREAS TO WATCH WILL BE DENVER COUNTY AND
ALSO IN THE FORT MORGAN AREA...WHERE HEAVY RAINS YESTERDAY HAVE THE
SOILS WELL SATURATED.
LONG TERM
AXIS OF THE 500MB RIDGE PROGGED OVER ERN UTAH/WRN
WYOMING SUNDAY MORNING WITH NWLY MID-LVL FLOW OVER NERN COLORADO.
MODELS SHOW A WEAK RIPPLE EMBEDDED WITHIN THE FLOW ROUNDING THE TOP
OF THE RIDGE DROPS DOWN THE EAST SIDE OF THE RIDGE OVER NERN
COLORADO DURING THE LATE MORNING AND AFTERNOON HOURS ON SUNDAY.
MEANWHILE...A STRONG SFC HIGH SLIDING SEWRD OUT OF SOUTH DAKOTA AND
ACROSS CNTRL NEBRASKA TURNS LOW-LEVEL FLOW S-SELY ON THE PLAINS OF
ERN COLORADO. NAM AND TO LESSER EXTENT THE GFS SHOW THE FORMATION OF
A DENVER CYCLONE JUST EAST OF THE METRO AREA AROUND MIDDAY. MODELS
SHOW THE CYCLONE SHEARING APART DURING THE AFTERNOON AS BNDRY LAYER
FLOW BACKS AROUND MORE TO AN ELY COMPONENT. LOW LEVEL FLOW DRIVES A
THETA-E RIDGE UP INTO NERN COLORADO WITH THE HIGHER VALUES UP ALONG
THE SRN FTHLS AND OVER THE PALMER DIVIDE. NAM INDICATES MID-
AFTERNOON SFC BASED CAPE VALUES UP AROUND 2500 J/KG ACROSS ERN
DOUGLAS AND ELBERT COUNTIES. WHEREAS CAPE VALUES NOT AS HIGH ON THE
GFS...THE MODEL DOES SHOW A FINGER OF ELEVATED CAPE EXTENDING NWRD
ACROSS ERN ARAPAHOE...LINCOLN...WASHINGTON AND LOGAN COUNTIES ABOUT
THE TIME THE SHORTWAVE PASSES BY. BOTH MODELS INDICATE INITIAL STORM
DEVELOPMENT ACROSS THE NERN CORNER OF THE STATE DURING THE MORNING
HOURS. BY AFTERNOON...NEW STORM GROWTH APPEARS TO SHIFT WESTWARD TO
AREAS OVER AND NEAR THE FRONT RANGE AND ACROSS THE PALMER DIVIDE
WITH THE REINFORCED MOIST UPSLOPE FLOW. NAM QPF FIELDS INDICATE THE
GREATER PCPN AMOUNTS OVER THE PALMER DIVIDE SOUTH/SOUTHEAST OF
DENVER WHERE THE BEST INSTABILITY...VERTICAL SHEAR AND MOISTURE ALL
COME TOGETHER. WITH NWLY TRANSPORT WINDS...SUSPECT WE/LL SEE A DROP
OFF IN T-STORM FORMATION/COVERAGE UP TOWARDS THE WYOMING BORDER AS
MODELS SHOW WEAK SUBSIDENCE AND DRIER AIR MOVING IN AT MID-LEVELS ON
THE BACK SIDE OF THE PASSING SHORTWAVE. SPC CONVECTIVE OUTLOOK HAS
MOST OF ERN COLORADO UNDER A SLIGHT RISK ON SUNDAY. CAN/T ARGUE WITH
THAT. ALTHOUGH SUSPECT LARGE HAIL AND DAMAGING T-STORM WINDS WILL BE
MAIN THREAT...AND MAINLY SOUTH AND EAST OF THE DENVER METRO AREA.
SCATTERED CONVECTION EXPECTED TO LINGER INTO THE EVENING BUT AS
DRIER AIR AND SUBSIDENCE SPREADS IN FM THE NORTHWEST SHOULD SEE
STORM ACTIVITY PRETTY MUCH WINDING DOWN BY MIDNIGHT...UNLIKE WHAT
WE/LL SEEN THE PAST FEW NIGHTS.
BY MONDAY...AIRMASS CONTINUES TO WARM AND STABILIZE ALOFT AS THE
UPPER RIDGE CURRENTLY OUT WEST AMPLIFIES AND SHIFTS EASTWARD. Q-G
VERTICAL MOTION FIELDS INDICATE INCREASING SUBSIDENCE IN THE 700-500
MB LAYER FOR MOST OF THE DAY. HOWEVER...MODELS CONTINUE TO SHOW
LOW-LEVEL MOISTURE BEING TRANSPORTED NWRD INTO NERN COLORADO...WITH
MID/LATE AFTERNOON CAPES IN THE 1000-2000 J/KG RANGE. EVEN WITH A
RELATIVELY STRONG MID-LEVEL INVERSION IN PLACE...LOW POPS STILL
IN ORDER WITH BEST CHANCE FOR MEASURABLE PCPN EAST OF A FORT MORGAN
TO ELBERT LINE. LOOK FOR TEMPERATURES ON MONDAY TO BE 5-10F ABOVE
THOSE ON SUNDAY.
TUESDAY THROUGH THURSDAY...MID-LEVELS LOOK EVEN DRIER AND MORE
STABLE AS THE UPPER RIDGE MIGRATES ACROSS THE STATE. TEMPERATURES
ALOFT ALSO CONTINUE TO WARM WITH THE FCSTD 700 MB TEMP OVER DENVER
AROUND 16C ON TUESDAY...19C ON WEDNESDAY AND AROUND 20C ON THURSDAY.
THEREFORE SHOULD SEE A PERIOD OF LOW TO MID 90S ON THE PLAINS AND
60S TO LOWER 80E IN THE HIGH COUNTRY. ANY STORMS THAT MANAGE TO FORM
LATE IN THE DAY WILL PROBABLY BE HIGH BASED AND PRODUCE MAINLY GUSTY
MICROBURST WINDS AND ONLY A BRIEF RAINFALL.
BY FRIDAY MAY SEE BIT OF AN INCREASE IN T-STORM ACTIVITY AS THE
PLUME OF MONSOONAL MOISTURE BECOMES RE-ESTABLISHED OVER NEW MEXICO
AND ERN COLORADO.
AVIATION...VARYING IFR/MVFR CIGS EARLY THIS AM
ESP IN/NR
FOOTHILLS AND DOUGLAS COUNTY. EXPECT THUNDERSTORMS TO DEVELOP THIS
AFTN...MAINLY IN THE 20-01Z TIME FRAME. SURFACE WINDS WILL SHIFT
N-NE BY AFTN AS HIGH PRESSURE BUILDS SOUTHWARD FROM WYOMING.
BOU WATCHES/WARNINGS/ADVISORIES
NONE.
ENTREKIN/BAKER
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