Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 082140
AFDBOU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DENVER/BOULDER CO
340 PM MDT TUE JUL 8 2014

.SHORT TERM...(THIS EVENING THROUGH WEDNESDAY)
ISSUED AT 339 PM MDT TUE JUL 8 2014

A HOT UPPER LEVEL HIGH REMAINS ANCHORED OVER THE FOUR CORNERS
REGION WITH MONSOON MOISTURE FLOWING NORTHWARD UP OVER THE DESERT
SOUTHWEST AND GREAT BASIN. SOME OF THIS MOIST AND UNSTABLE
SUBTROPICAL AIR HAS WRAPPED AROUND THE TOP OF THIS NEGATIVELY
TILTED RIDGE AND OVER SOUTHERN AND WESTERN PORTIONS OF COLORADO
AS EVIDENT ON H20 VAPOR SATELLITE IMAGERY. MEANWHILE MID-LEVEL AIR
OVER NORTHEAST SECTIONS OF THE STATE HAS DRIED SOME IN THE PAST
12 HOURS...ALTHOUGH SLIGHT COOLING WAS EVIDENT ON RAP AND ACARS
SOUNDINGS OVER DENVER DURING THE PAST COUPLE OF HOURS WITH A WEAK
THERMAL/SHORTWAVE TROUGH MOVING ALONG IN NORTHWEST FLOW ALOFT.
CONVECTION HAS BEEN SLOW TO ORGANIZE TODAY...DUE IN PART TO
WARMING ALOFT AS NOTED ABOVE AND THE STABLE POST-FRONTAL AIRMASS
EAST OF THE MTNS. MID-LEVEL SUBSIDENCE ON THE BACK SIDE OF THE
PASSING SHORTWAVE WAS ALSO OCCURRING OVER NORTHERN PORTIONS OF
THE CWA. WHEREAS WEAKLY ASCENDING AIR WITH CONVECTION INHIBITION
NEARLY GONE AHEAD OF THE SHORTWAVE COUPLED WITH STEEPENING LAPSE
RATES WAS HELPING TO GENERATE SCATTERED SHOWERS/T-STORMS OVER
MTN...FOOTHILL AND HIGH PARK AREAS ROUGHLY SOUTH OF I-70 AT THIS
HOUR. ONLY A MATTER OF TIME BEFORE SOME OF THIS CONVECTION DRIFTS
SOUTHEAST ACROSS THE SOUTHERN URBAN CORRIDOR AND PALMER DIVIDE.
LATEST CAPE PLOTS INDICATE VALUES ALREADY IN THE 500-1500 J/KG
RANGE OVER THE SOUTHERN FOOTHILLS...SOUTH PARK AND WESTERN
SECTIONS OF THE PALMER DIVIDE. IT IS IN THIS AREA THAT THE CHANCE
OF STORMS IS GREATEST...IN THE 40-50 PERCENT RANGE. THESE SAME
STORMS ARE ALSO MORE LIKELY TO PRODUCE HAIL...BRIEF INTENSE
RAINFALL AND GUSTY OUTFLOW WINDS. IS POSSIBLE WE COULD SEE HAIL
STONES UPWARDS OF 3/4 INCH IN DIAMETER. IF IT WERE A BIT
WARMER...EVEN LARGER THAN THIS. OUT ACROSS THE PLAINS A RELATIVELY
COOL AND STABLE POST-FRONTAL AIRMASS HAS PRETTY MUCH CAPPED ANY
CONVECTION THIS AFTERNOON. THERE/S ALWAYS A CHANCE THAT AN OUTFLOW
BOUNDARY MOVING OUT FROM A T-STORM NEAR THE FOOTHILLS COULD SPARK
A STORM OR TWO ON THE PLAINS...BUT THE HRRR...RUC...NAM AND THE
NAM NEST AND ARI SYNTHETIC SATELLITE IMAGERY DO NOT INDICATE THIS
HAPPENING.

WITH THE SHORTWAVE TROUGH PASSING TO THE SOUTHEAST OF THE FORECAST
AREA BY EARLY THIS EVENING...SHOULD SEE A MARKED DECREASED IS
SHOWER AND STORM ACTIVITY...FAR FROM WHAT HAPPENED LAST EVENING.
OVERNIGHT...SHOULD SEE SKIES CLEAR AS A DRIER AND WARMER DEEP
LAYER FLOW SETS UP.

ON WEDNESDAY...DAY APPEARS TO START OUT DRY WITH WESTERLY MTN TOP
FLOW AND A SOUTH-SOUTHWESTERLY FLOW LOWER DOWN. THROUGH THE
DAY...SHOULD SEE MOISTURE LEVELS INCREASING AGAIN AS MONSOONAL
MOISTURE FLOWS IN FROM UTAH. THIS TIME...THE WEST SLOPE AND HIGHER
AREAS UP ALONG THE CONTINENTAL DIVIDE WILL HAVE THE BETTER CHANCE
FOR SHOWERS/T-STORMS...SOME POSSIBLY PRODUCE LOCALLY HEAVY
RAINFALL AND SMALL HAIL. EAST SLOPE AREAS MAY GET INTO THE ACT BUT
NOT UNTIL MID TO LATE AFTERNOON. COULD SEE A FEW STORMS MOVE OFF
THE FOOTHILLS AND AS THEY DO PRODUCE OUTFLOW THAT IGNITES
ADDITIONAL STORM DEVELOPMENT ON THE PLAINS. AT THIS TIME...STORM
COVERAGE ON THE PLAINS DURING THE DAY DOES NOT LOOK MUCH MORE THAN
ISOLATED. FINALLY TEMPERATURES ON THE PLAINS WEDNESDAY ARE PROGGED
TO BE AS MUCH AS 10-12 DEGS F WARMER THAN TODAY...WITH ONLY
SLIGHTLY WARMER TEMPERATURES IN THE HIGH COUNTRY.

.LONG TERM...(WEDNESDAY NIGHT THROUGH TUESDAY)
ISSUED AT 339 PM MDT TUE JUL 8 2014

SOME STORMS WILL BE POSSIBLE WEDNESDAY EVENING...MAINLY ALONG THE
FOOTHILLS AND ACROSS THE PALMER DIVIDE WHERE MODELS SHOW CAPES
AROUND 500 J/KG. PRECIPITABLE WATER VALUES RANGE FROM 0.70 INCHES
ALONG THE FOOTHILLS TO AROUND TO 0.90 INCHES FAR EASTERN PLAINS...
WITH 0.60 INCHES ACROSS THE MOUNTAINS. SO...BRIEF HEAVY RAIN WILL
BE POSSIBLE WITH SOME OF THE STORMS. AIRMASS STABILIZES BY
MIDNIGHT... SO MOST CONVECTION SHOULD END AT THAT TIME. THERE MAY
BE A FEW SHOWERS OR STORMS LINGERING FAR EASTERN CORNER AND ACROSS
THE HIGHER MOUNTAINS. ON THURSDAY...UPPER LEVEL RIDGE WILL BE OVER
COLORADO WITH WEAKER WEST NORTHWEST FLOW ALOFT. WITH CENTER OF THE
UPPER HIGH OVER NORTHERN NEW MEXICO...MAIN FLOW OF SUBTROPICAL
MOISTURE TO BE ACROSS WESTERN COLORADO AND EASTERN UTAH. STILL
SUFFICIENT MOISTURE ACROSS CENTRAL AND EASTERN COLORADO FOR A
CHANCE OF THUNDERSTORMS BY THE AFTERNOON WITH THE BEST CHANCE
ACROSS THE MOUNTAINS AND FOOTHILLS. PRECIPITABLE WATER VALUES
INCREASE TO AROUND 0.70 ACROSS THE MOUNTAINS WITH READINGS RANGING
FROM 0.80 ALONG THE FOOTHILLS TO OVER AN INCH FAR EASTERN PLAINS.
POTENTIAL FOR STORMS TO PRODUCE BRIEF HEAVY RAIN. FAIRLY LIGHT
STEERING WINDS COULD CREATE SOME LOCALIZED FLOODING PROBLEMS.
FAIRLY WARM AIRMASS WITH RIDGE OVERHEAD. HIGHS IN THE LOWER AND
MIDDLE 90S EXPECTED ACROSS THE PLAINS. FOR FRIDAY...UPPER RIDGE
STILL OVER COLORADO WITH FLOW ALOFT MORE WESTERLY. SUBTROPICAL
MOISTURE TO CONTINUE TO SPREAD NORTHWARD ACROSS WESTERN COLORADO
WITH A BIT MORE MOISTURE OVER EASTERN COLORADO. THIS NOTED BY AN
INCREASE IN PRECIPITABLE WATER VALUES...WITH OVER AN INCH ACROSS
THE PLAINS. SUFFICIENT MOISTURE FOR A CHANCE OF THUNDERSTORMS
DURING THE AFTERNOON AND EVENING. BEST CHANCE OF THUNDERSTORMS TO
BE ACROSS THE MOUNTAINS AND FOOTHILLS. MODELS SHOWING A MID LEVEL
DISTURBANCE MOVING ACROSS WYOMING DURING THE AFTERNOON AND
EVENING. SOME INCREASE IN MID LEVEL ASCENT ACROSS THE NORTHERN
BORDER...WHICH MAY HELP INCREASE THE THUNDERSTORM CHANCES NEAR THE
WYOMING BORDER. STORMS TO PRODUCE BRIEF HEAVY RAINFALL...BUT
APPEARS THERE WILL BE ENOUGH STORM MOTION TO KEEP ANY FLOOD THREAT
MINIMAL. AIRMASS STILL FAIRLY WARM WITH HIGHS IN THE LOW AND
MIDDLE 90S ACROSS THE PLAINS. ON SATURDAY: RIDGE RETROGRADES
SLIGHTLY WITH NORTHWEST FLOW ALOFT ACROSS COLORADO. MAIN BATCH OF
SUBTROPICAL MOISTURE MOVES ACROSS UTAH...RESULTING IN A SLIGHT
DECREASE IN PRECIPITABLE WATER ACROSS COLORADO. SHOULD SEE LESS
THUNDERSTORM ACTIVITY AS A RESULT...WITH THE BEST CHANCE OVER THE
MOUNTAINS. AIRMASS COOLER WITH HIGHS IN THE MID 80S ACROSS THE
PLAINS.

FOR THE LATER DAYS...SUNDAY THROUGH TUESDAY: UPPER RIDGE ACROSS
GREAT BASIN SUNDAY WITH NORTHWEST FLOW ALOFT ACROSS COLORADO. BOTH
GFS AND ECMWF SHOW THE RIDGE SHIFTING EAST INTO COLORADO MONDAY
AND TUESDAY. SUBTROPICAL MOISTURE TO SHIFT EAST INTO WESTERN
COLORADO AS A RESULT....BRINGING A BETTER CHANCE FOR AFTERNOON AND
EVENING THUNDERSTORMS ALONG WITH SLIGHTLY WARMER TEMPERATURES.

&&

.AVIATION...(FOR THE TAFS THROUGH 00Z WEDNESDAY LATE AFTERNOON)
ISSUED AT 339 PM MDT TUE JUL 8 2014

ISOLATED T-STORMS ARE EXPECTED TO TRACK SOUTHEAST ACROSS THE
DENVER METRO AREA NOW THROUGH 01Z THIS EVENING. THE MAJORITY OF
THESE STORMS WILL PRODUCE LITTLE MORE THAN A BRIEF LIGHT
TO MODERATE RAINSHOWER...GUSTY ERRATIC OUTFLOW WINDS AND
OCCASIONAL CLOUD-TO-GROUND LIGHTNING. HOWEVER STORMS CROSSING
SOUTHERN AND WESTERN SECTIONS OF THE METRO AREA HAVE THE POTENTIAL
TO PRODUCE SMALL HAIL AND HEAVIER RAINFALL. OVERALL...EAST-
SOUTHEAST SURFACE WINDS WILL PREVAIL AT SPEEDS OF 8-14KT THROUGH
EARLY EVENING...THEN THE TYPICAL DRAINAGE WIND PATTERN WILL SET
UP FOR THE REMAINDER OF THE NIGHT. ON WEDNESDAY...EXPECT SOUTH-
SOUTHWESTERLY WINDS UNDER 11 KTS DURING THE MORNING HRS THEN
WEST- NORTHWESTERLY AT 8-14KTS IN THE AFTERNOON.

&&

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

$$

SHORT TERM...BAKER
LONG TERM...D-L
AVIATION...BAKER


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