Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 261554
AFDBOU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DENVER/BOULDER CO
954 AM MDT SAT JUL 26 2014

.UPDATE...
ISSUED AT 945 AM MDT SAT JUL 26 2014

MID-LEVEL CLOUD BANK ON SATELLITE AND ISOLATED RAIN SHOWERS
ON RADAR OVER THE NORTHERN MTNS/NORTHERN FRONT RANGE FOOTHILLS
BEING GENERATED BY A WEAK WEATHER DISTURBANCE UP AROUND 500MBS
NOW PASSING OVER THE NORTH CENTRAL COLORADO. MESOSCALE MODELS
APPEAR A BIT BEHIND WITH REGARD TO MOVING THIS FEATURE THROUGH
THE AREA. MUCH OF WHAT IS FALLING FROM THESE CLOUDS IS LIKELY
NOT REACHING THE VALLEY FLOORS. EXPECT THIS DISTURBED WEATHER TO
MOVE EAST OF THE CWA LATE THIS MORNING OPENING THE DOOR TO A
SHORT PERIOD OF SUNSHINE WHICH WILL HELP DESTABILIZE AN ALREADY
MOIST MTN TOP LAYER. THIS WILL LEAD TO TODAY`S MAIN ROUND OF
SHOWERS AND T-STORMS. INTEGRATED PRECIPITABLE WATER VALUES IN THE
AREA CONTINUE TO RISE. AT LAST CHECK THE IPW OVER DENVER WAS A
MOIST 0.97 INCH...WITH AN EVEN WETTER IPW OF 1.11 INCH OVER GRAND
JUNCTION. MEANWHILE...A POST-FRONTAL AIRMASS IS NOW IN PLACE EAST
OF THE MTNS BUT YOU COULDN/T TELL BY TEMPERATURES ALREADY IN THE
UPPER 70S/LOWER 80S. HAVE ALSO NOTICED ONLY A SLIGHT DIP IN SFC
DEWPOINTS WITH +50F DEWPTS THE RULE. NORTHERLY SFC WINDS WERE
ALREADY TURNING EAST-NORTHEASTERLY ON THE PLAINS. MODELS SHOW
THIS UPSLOPE FLOW PERSISTING UNTIL STORMS OVER THE FRONT RANGE
SEND OUT STRONG/GUSTY OUTFLOW WINDS AS MESOSCALE MODELS INDICATE
HAPPENING AFTER 19Z. MEANWHILE ANOTHER WEAK UPPER AIR DISTURBANCE
NOW OVER SOUTHERN UTAH IS FORECAST TO MAKE SLOW NORTHEASTWARD
PROGRESS OVER THE NEXT 12-18 HOURS. HOWEVER CAN ALREADY SEE
ELEVATED CONVECTION OUT AHEAD OF THIS FEATURE SPREADING OVER
WESTERN COLORADO. AT THEIR PRESENT SPEED...SHOULD SEE THESE
CONVECTIVE CLOUDS SPREADING OVER THE NORTHERN/CENTRAL MTNS OF
COLORADO BY AROUND MIDDAY. OUR CURRENT FORECAST HAS LIKELY POPS
FOR THE MTNS THIS AFTERNOON AND EARLY EVENING. SEE LITTLE REASON
TO CHANGE THAT. ALSO HAVE SCATTERED POPS FOR THE MTN VALLEYS AND
ADJACENT HIGH PLAINS...AND ISOLATED STORMS FARTHER OUT ON THE
PLAINS LATER TODAY WHERE THE LOWER ATMOSPHERE LOOKS DRIER AND NOT
AS UNSTABLE. MAIN CONCERN EAST OF THE MTNS WILL BE THE THREAT OF
DOWNBURST WINDS AND STRONG AND GUSTY OUTFLOW WINDS AS WELL AS
LIGHTNING. COULD SEE LOCALIZED RAIN AMOUNTS APPROACHING AN INCH
IN THE HIGH COUNTRY...WHILE MOST AREAS ON THE PLAINS LITTLE MORE
AN A TENTH OF AN INCH. BUT WITH IPW VALUES UP AROUND AN INCH...CAN
NOT RULE OUT ISOLATED AMOUNTS ON THE PLAINS AND PALMER DIVIDE
NEARING AN INCH LATE AFTERNOON AND EARLY THIS EVENING. FORECAST
GRIDS HAVE BEEN MODIFIED TO REFLECT CURRENT SATELLITE AND RADAR
DATA AND THE WEATHER PROSPECTS MENTIONED ABOVE.

&&

.AVIATION...(FOR THE TAFS THROUGH 18Z SUNDAY MORNING)
ISSUED AT 945 AM MDT SAT JUL 26 2014

EAST-NORTHEAST POST-FRONTAL WINDS WILL SPREAD OVER REMAINING
PORTIONS OF THE DENVER METRO AREA DURING THE NEXT HOUR OR SO AT
SPEEDS GENERALLY UNDER A 12KTS. PASSING MID AND HIGH CLOUD WILL
MOVE OFF THE FRONT RANGE LATER THIS MORNING ALLOWING FOR MORE
SUNSHINE AND HEATING. BY EARLY AFTERNOON...HIGH BASED T-STORMS
FORMING OVER THE FRONT RANGE ARE EXPECTED TO SEND OUT GUSTY
OUTFLOW FLOW...INITIALLY IMPACTING KBJC...THEN KAPA AND FINALLY
KDEN SAY AROUND 20Z WITH GUSTS POTENTIALLY 35-40KTS. DO NOT SEE
MUCH IN THE WAY OF RAINFALL...BUT CANNOT RULE OUT A BRIEF INTENSE
RAINFALL CAUSING VSBYS TO LOWER TO 4-5 MILES. ISOLATED TO
SCATTERED SHOWERS AND T-STORMS OVER AND AROUND DENVER COULD LINGER
UNTIL MID-EVENING...THEN GRADUALLY CLEARING OVERNIGHT. GUSTY AND
ERRATIC WINDS WITH OUTFLOW BOUNDARIES CRISS-CROSSING THE METRO
AREA SHOULD SETTLE DOWN TO A TYPICAL DRAINAGE WIND PATTERN AFTER
03Z THIS EVENING...WITH SPEEDS GENERALLY UNDER 10KTS.

.SHORT TERM...(TODAY THROUGH TONIGHT )
ISSUED AT 329 AM MDT SAT JUL 26 2014

TODAY WILL FEATURE A BATTLE BETWEEN DRIER LOW LEVEL AIR PUSHING
ACROSS THE PLAINS AND MID/UPPER LEVEL MOIST PLUME ROTATING AROUND
THE UPPER RIDGE. CURRENT WATER VAPOR LOOP SHOWS A LARGE MOISTURE
PLUME ROTATING NORTHEAST FROM ARIZONA INTO UTAH...WHICH IS
SCHEDULED TO REACH COLORADO DURING PEAK HEATING THIS AFTERNOON.
MEANWHILE...A WEAK SURFACE COLD FRONT WAS PUSHING SOUTHEAST ACROSS
WYOMING AND WILL MOVE ACROSS NORTHEAST COLORADO THIS MORNING. MUCH
DRIER LOW LEVEL AIR WITH DEWPOINTS IN THE 30S AND 40S WERE BEHIND
THIS FRONT. THE FRONT IS EXPECTED TO GRADUALLY WASH OUT THIS
AFTERNOON WITH WEAK EASTERLY UPSLOPE FLOW AND SOME MODERATION OF
THE DRYING LATER THIS AFTERNOON. AT THE SAME TIME...NUMEROUS
SHOWERS AND STORMS ARE EXPECTED TO DEVELOP IN THE HIGH COUNTRY AS
MOISTURE PLUME ROTATES ACROSS THE STATE AND INTERACTS WITH DAYTIME
HEATING. THE STORMS SHOULD HAVE MODEST SUCCESS AT HOLDING TOGETHER
AS THEY COME ACROSS THE FRONT RANGE AS COOL FRONT WASHES OUT AND
CAP WEAKENS/BREAKS. CAPES ARE QUITE LIMITED AND GENERALLY LESS
THAN 500 J/KG...BUT RELATIVELY DEEP AND DRY SUBCLOUD LAYER WOULD
SUPPORT STRONG AND GUSTY OUTFLOW WINDS IN AND NEAR ANY STORMS. AS
THEY MOVE EAST ACROSS THE PLAINS...THEY WILL ENCOUNTER A DEEPENING
AND STRENGTHENING STABLE AIRMASS SO EXPECT A GRADUAL
WEAKENING/DISSIPATION AS THEY MOVE TO THE EAST. OVERALL...LIKED
THE LATEST MESOSCALE MODEL OUTPUT INCLUDING THE HRRR/RAP/WRF WHICH
SHOWS THIS SAME SCENARIO. ANY HEAVY RAIN THREAT EVEN IN THE
MOUNTAINS AND FOOTHILLS WOULD BE LIMITED BY RATHER FAST STORM
MOVEMENT. STRONGER STORMS COULD STILL PUT DOWN A HALF INCH IN
15-20 MINUTES.

PRECIPITATION IS EXPECTED TO DECREASE RATHER QUICKLY THIS EVENING
AS AIRMASS GETS WORKED OVER AND STABILIZES WITH LOSS OF DAYTIME
HEATING. THEN SKIES WILL GRADUALLY CLEAR ALTHOUGH SOME CLOUD
REDEVELOPMENT POSSIBLE LATER TONIGHT WITH RETURN FLOW OF MOISTURE.

WITH REGARD TO TEMPERATURES...WEAK FRONT SHOULD BRING ANOTHER
DEGREE OR TWO OF COOLING TO THE PLAINS...BUT STILL REACH OR EXCEED
90F OVER THE LOWER ELEVATIONS. HIGH ONCE AGAIN WILL LIKELY OCCUR
BY EARLY AFTERNOON BEFORE MORE WIDESPREAD SHOWER AND STORM
OUTFLOWS AND CLOUD COVER PROVIDES COOLING BY MID TO LATE
AFTERNOON.

.LONG TERM...(SUNDAY THROUGH FRIDAY)
ISSUED AT 329 AM MDT SAT JUL 26 2014

THE BROAD HIGH PRESSURE RIDGE ALOFT WILL BEGIN TO BUILD NORTH AND
WEST OF COLORADO ON SUNDAY AS THE FLOW ALOFT TRANSITIONS TO
NORTHWEST. ANOTHER COLD FRONT WILL PUSH SOUTHWARD OVER NORTHEAST
COLORADO EARLY SUNDAY MORNING WITH COOLER LOW LEVELS. THIS WILL
KEEP THE ATMOSPHERE FAIRLY CAPPED WITH LOW LEVEL STABILITY FOR
MUCH OF THE DAY. THIS WILL RESULT IN MOST OF THE STORMS REMAINING
IN THE MOUNTAINS AND HIGHER TERRAIN. MUCH COOLER TEMPERATURES AS
WELL FOR SUNDAY AFTERNOON WITH READINGS ONLY AROUND 80 DEGREES
ACROSS THE PLAINS. COULD CERTAINLY SEE SOME HEAVY RAINERS IN THE
MOUNTAINS AS PW VALUES REMAIN ABOVE AN INCH.

ON MONDAY THE LOW LEVEL FLOW SHIFTS MORE SOUTHEAST WITH MOIST LOW
LEVEL FLOW. AIRMASS BECOMES MORE UNSTABLE MONDAY AFTERNOON WITH A
BETTER CHANCE FOR STORMS OVER THE ENTIRE AREA. SHEAR PROFILE
IMPROVES THROUGH THE COLUMN AND SUFFICIENT INSTABILITY FOR EVEN A
FEW SEVERE STORMS ALONG WITH HEAVY RAIN.

FOR TUESDAY...LONG RANGE MODELS NOW SHOW A WEAK TROF WHICH ROTATES
AROUND AND SLIGHTLY UNDERCUTS THE RIDGE ACROSS COLORADO BRINGING
AN EVEN BETTER CHANCE FOR STORMS. COOLER AGAIN ON TUESDAY WITH
MORE CLOUD COVER AND TEMPERATURES AROUND 80 DEGREES. APPEARS LATE
TUESDAY AND INTO EARLY WEDNESDAY MAY BE THE COOLEST AND WETTEST
PORTION OF THE WEEK WITH THE POTENTIAL FOR HEAVY RAIN WITH THE
STORMS.

FOR WEDNESDAY THROUGH FRIDAY...A CONTINUATION OF THE NORTHWEST
FLOW PATTERN WITH THE RIDGE ALOFT ANCHORED TO THE WEST OF
COLORADO. THIS WILL KEEP A COOL AND RELATIVELY WET PATTERN WITH
BELOW NORMAL TEMPERATURES AND ABOVE NORMAL CHANCES FOR SHOWERS
AND THUNDERSTORMS.

&&

.AVIATION...(FOR THE TAFS THROUGH 12Z SUNDAY MORNING)
ISSUED AT 329 AM MDT SAT JUL 26 2014

SOUTHWEST WINDS AROUND 10-15 KTS WILL PREVAIL UNTIL WEAK FRONTAL
ARRIVAL AROUND 13Z-14Z. THEN LOOK FOR NORTHEAST WINDS AROUND 10
KTS GRADUALLY SHIFTING MORE EASTERLY DURING THE DAY. SIMILAR
THUNDERSTORM CHANCES TO YESTERDAY WITH GUSTY OUTFLOW WINDS
BECOMING MORE LIKELY...ENOUGH FOR TEMPO VRB20G35KT WINDS FROM
20Z/21Z-01Z AND POSSIBLY TEMPO -TSRA. LITTLE CHANCE OF ANY VSBY
RESTRICTION GIVEN DRIER LOW LEVELS. STORM CHANCES WILL DECREASE
RAPIDLY BY 01Z-02Z WITH VFR CONDITIONS PERSISTING THROUGH SUNDAY
MORNING.


&&

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

$$

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



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