Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 111550
AFDBOU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DENVER/BOULDER CO
950 AM MDT FRI JUL 11 2014

.UPDATE...
ISSUED AT 949 AM MDT FRI JUL 11 2014

MOISTURE HAS INCREASED OVER THE AREA. PRECIPITABLE WATER FROM THE
12Z SOUNDING AT KDNR IS AN INCH AND SATELLITE ESTIMATES ARE RUNNING
A LITTLE OVER AN INCH. MOSTLY SUNNY SKIES THIS MORNING WILL ALLOW
FOR GOOD HEATING WITH HIGHS CLIMBING INTO THE UPPER 80S. LOWER 50S
DEW POINTS COMBINED WITH THE UPPER 80S PRODUCES CAPES OF 500 TO 1000
J/KG. MAIN THREATS TODAY WILL BE THE CHANCE OF LOCALIZED FLASH
FLOODING...HAIL AND STRONG WINDS. BEST CHANCE FOR SEVERE STORMS WILL
BE OVER THE EASTERN PLAINS. NEARLY ALL THE MODELS ARE SHOWING A GOOD
BATCH OF STORMS FORMING OVER THE MOUNTAINS AND FOOTHILLS AND THEN
SPREADING ACROSS THE URBAN CORRIDOR. PLAN ON INCREASING POPS IN THE
21Z TO 02Z TIME FRAME.

&&

.SHORT TERM...(TODAY THROUGH TONIGHT )
ISSUED AT 459 AM MDT FRI JUL 11 2014

THERE ARE STILL A FEW BANDS OF LIGHT SHOWERS THAT APPEAR TO BE
ASSOCIATED WITH WEAK RIPPLES IN THE LIGHT SOUTHWEST FLOW ALOFT.
EXPECT THAT THESE WILL CONTINUE TO DIMINISH THOUGH SOME MOUNTAIN
SHOWERS ARE POSSIBLE THIS MORNING. LOW LEVELS ON THE PLAINS ARE A
LITTLE COOLER/MOISTER AS A RESULT OF OUTFLOW FROM YESTERDAYS
WYOMING/NEBRASKA CONVECTION. THERE MAY ALSO BE SLIGHT WARMING
ALOFT...AND THERE WILL STILL BE SOME CLOUD COVER OVER THE NORTHERN
AND WESTERN PARTS OF OUR AREA. FOR THESE REASONS I WILL BACK AWAY
FROM THE EARLY START TO CONVECTION THAT WE HAD FORECAST...
EXCEPTING SOME ISOLATED ELEVATED CONVECTION. IT WILL LIKELY BE A
MARGINAL ENVIRONMENT THIS AFTERNOON DESPITE THE INCREASED MOISTURE
WITH TEMPERATURES A LITTLE SHORT OF WHAT WOULD BE NEEDED FOR
WIDESPREAD CONVECTION. MOST LIKELY STORMS WILL START ON THE
UPSLOPE CONVERGENCE ZONE EARLY TO MID AFTERNOON AND WORK SLOWLY
TOWARD THE NORTHEAST. THERE MAY BE SOME STORMS ORIGINATING ON THE
PLAINS IN THE AFTERNOON...BUT MOST LIKELY THE PLAINS ACTIVITY WILL
BE RIDING OUTFLOW BOUNDARIES THAT MAY NOT ARRIVE UNTIL
EVENING...SO I LOWERED POPS ON THE EASTERN PLAINS IN THE
AFTERNOON.

WITH PRECIPITABLE WATER UP OVER AN INCH THIS MORNING AND SLOW
STORM MOTIONS EXPECTED...SOME OF THE STORMS WILL PRODUCE HEAVY
RAIN. SEE THE HYDROLOGY SECTION FOR MORE DETAILS. LOW SHEAR WILL
LIMIT THE SEVERE THREAT...BUT WITH THE HIGH WATER CONTENT AND
AROUND 1500 J/KG OF CAPE IN THE RICHER MOISTURE ON THE PLAINS
THERE IS A MARGINAL HAIL/WIND THREAT FROM STRONG PULSES AND
OUTFLOW WINDS.

.LONG TERM...(SATURDAY THROUGH THURSDAY)
ISSUED AT 459 AM MDT FRI JUL 11 2014

ON SATURDAY...THE UPPER RIDGE OF HIGH PRESSURE WILL STRETCH FM THE
GREAT BASIN INTO THE SRN GREAT PLAINS. THE FLOW OVER NERN CO WILL
BE NORTHWESTERLY WITH A TROUGH BRUSHING ACROSS THE CWFA AS A
SYSTEM PASSES TO THE NORTH AND EAST. THIS WL USHER IN A SLIGHTLY
COOLER AMS. ELY UPSLOPE WINDS WILL CONTINUE TO TRANSPORT LOW
LEVEL MOISTURE INTO THE FRONT RANGE. PW VALUES WILL REMAIN WELL
ABOVE ONE INCH ALONG AND EAST OF THE FRONT RANGE FOOTHILLS. SFC
BASED CAPES IN THE 500-600 J/KG RANGE FOR DENVER WITH PW VALUES
AROUND 1.2 INCHES. STORM MOTIONS ALONG THE FRONT RANGE A LITTLE
SLOWER...UNDER 10 KTS...SO THIS WILL DEFINITELY ELEVATED THE
POTENTIAL FOR FLASH FLOODING IN AND NEAR THE FOOTHILLS. FURTHER
EAST...STORM MOTIONS AROUND 15 KTS...CAPES NEAR 800 J/KG WITH PW
VALUES CLOSE TO 1.3 INCHES. SOME DIRECTIONAL SHEAR AS WELL SO A
STORM OR TWO COULD REACH SEVERE CRITERIA. MAIN CONCERN WILL BE
FLASH FLOODING. ON SUNDAY...THERE WILL THE AMS WILL BE A LITTLE
DRIER..AROUND ONE INCH WITH CAPES CLOSE TO 800 J/KG ALONG THE
FRONT RANGE...STILL MOIST OVER THE NORTHEAST PLAINS WITH CAPES
CLOSER AROUND 100O J/KG SUNDAY AFTERNOON. THE OVERALL POTENTIAL
FOR HEAVY RAIN PRODUCING THUNDERSTORMS WILL CONTINUE...WITH A
SLIGHTLY GREATER RISK OF SEVERE THUNDERSTORMS PRODUCING LARGE HAIL
AND DAMAGING WET MICROBURST WINDS OVER THE NERN PLAINS. ON
MONDAY...THE RIDGE WILL BE OVER THE WESTERN U.S...WITH NERN CO
UNDER NORTHWEST FLOW ALOFT AS A LARGE SCALE TROUGH STRETCHES FM
THE GREAT LAKES REGION TOWARDS HUDSON BAY. ANOTHER FRONT WL SLIP
INTO NERN CO ON MONDAY. THE BEST CHC OF STORMS ON MONDAY WILL BE
IN AND NEAR THE FOOTHILLS AND PALMER DIVIDE. NORTHWESTERLY FLOW
WITH BETTER INSTABILITY IN THE AFTERNOON WILL BE PRESENT TUESDAY
AFTERNOON AND EVENING...SIMILAR SCENARIO ON WEDNESDAY. A DRIER
NWLY FLOW ALOFT WITH INCREASING SUBSIDENCE ALOFT ASSOCIATED WITH A
RIDGE OF HIGH PRESSURE SHOULD DECREASE THE TSTM POTENTIAL OVER THE
CWFA BY THURSDAY OF NEXT WEEK.

&&

.AVIATION...(FOR THE TAFS THROUGH 18Z SATURDAY MORNING)
ISSUED AT 949 AM MDT FRI JUL 11 2014

THUNDERSTORMS WILL LIKELY IMPACT THE DENVER AIRPORTS TODAY SOMETIME
BETWEEN 21Z AND 02Z. HEAVY RAIN...HAIL AND STRONG WINDS WILL BE
POSSIBLE WITH THE STORMS. LIGHT WINDS THIS MORNING WILL TURN
NORTHEASTERLY BY 18Z. ONCE THE CONVECTION MOVES OFF TO THE
EAST...NORTH TO NORTHWEST WINDS ARE EXPECTED FOR THE EVENING AND
OVERNIGHT HOURS. THERE WILL BE A SLIGHT CHANCE FOR FOG AND LOW
CLOUDS SATURDAY MORNING. WILL HOLD OFF FROM MENTIONING NOW UNTIL THE
CHANCES INCREASE.

&&

.HYDROLOGY...
ISSUED AT 459 AM MDT FRI JUL 11 2014

PRECIPITABLE WATER IS UP TO 1.1 INCHES THIS MORNING AND IS
EXPECTED TO REMAIN NEAR THAT VALUE TODAY. MEAN LOW TO MID LEVEL
WINDS THIS AFTERNOON ARE EXPECTED TO BE AROUND 10 MPH...BUT THE
SETUP OF SW WINDS AROUND 25 MPH AT 500 MB AND LOW LEVEL NE WINDS
WILL ENCOURAGE FORWARD PROPAGATION ONCE THE STORMS GET GOING...SO
ONCE THERE ARE ORGANIZED OUTFLOW STORMS SHOULD MOVE FASTER. THIS
WOULD MEAN THE FLOOD RISK WOULD BE HIGHEST FOR THE INITIAL STORMS
OVER THE FOOTHILLS BEFORE THEY START MOVING...AND ALSO FOR ANY
EARLY STORMS THAT WOULD DEVELOP ON THEIR OWN ON THE PLAINS. THERE
IS A BIT OF A WARM CLOUD LAYER...3000 TO 5000 FEET. ALL THIS ADDS
UP TO FAVORABLE CONDITIONS FOR HEAVY RAIN...BUT NOT STRONGLY
FAVORABLE FOR FLASH FLOODING. STRONGER STORMS COULD PRODUCE 1-2
INCHES IN 1-2 HOURS...MAYBE MORE IF A STORM ON THE PLAINS COULD
REMAIN STATIONARY. WILL HOLD OFF ON A FLASH FLOOD WATCH AT THIS
TIME...THREAT APPEARS TO BE A NOTCH LOWER WHERE THE MAIN IMPACT
WOULD BE IF ONE OF THESE STRONGER STORMS HAPPENS TO HIT A BURN
AREA OR URBAN AREA.

THE CHANCE OF THUNDERSTORMS WILL CONTINUE THROUGH THE WEEKEND.
OVERALL THE AIRMASS TO REMAIN MOIST SATURDAY. LOCALLY HEAVY RAIN
WILL OCCUR WITH THE STRONGER STORMS SATURDAY. SLOWER STORM
MOTIONS ALONG THE FRONT RANGE...LESS THAN 10 KTS...WILL ELEVATE
THE FLASH FLOOD THREAT ESPECIALLY IN THE BURN AREAS. THIS WILL BE
A BIGGER CONCERN IF TRAINING OR NEAR STATIONARY STORMS DEVELOP IN
THE EARLY STAGES ALONG THE FRONT RANGE...AND/OR HEAVY RAINFALL
DEVELOPS OVER ALREADY SATURATED SOILS. IN ANY EVENT...A FLASH
FLOOD WATCH MAY BE NECESSARY AT SOME POINT FOR THE FRONT RANGE
FOOTHILLS ON SATURDAY. FURTHER EAST...THE STORM MOTIONS WILL BE
CLOSER TO 15 KTS WHICH SHOULD HELP TO OFFSET THE FLASH FLOOD
THREAT.

ON SUNDAY...THERE MAY SOME DRYING. THE DRYING HOWEVER...MAY ONLY
INCREASE THE SEVERE POTENTIAL ACROSS THE NORTHEAST PLAINS. PW
VALUES WILL STILL BE AOA ONE INCH WHICH WILL ALLOW THE THREAT OF
LOCALLY HEAVY RAINFALL AND THE POTENTIAL FOR FLASH FLOODING TO
CONTINUE. THE MOIST AIRMASS WILL REMAIN OVER THE REGION MONDAY
THROUGH WEDNESDAY...THEN THE TSTM COVERAGE IS EXPECTED TO DECREASE
AS THE AIRMASS DRIES OUT AND BECOMES INCREASINGLY SUBSIDENT ALOFT.

&&

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

$$

UPDATE...MEIER
SHORT TERM...GIMMESTAD
LONG TERM...COOPER
AVIATION...MEIER
HYDROLOGY...COOPER/GIMMESTAD



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