Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 280148
AFDBOU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DENVER/BOULDER CO
748 PM MDT WED MAY 27 2015

.UPDATE...
ISSUED AT 748 PM MDT WED MAY 27 2015

THE 00Z SOUNDING FROM DNR SHOWED THE SURFACE BASE CAPE WAS CLOSE
TO A 1000 J/KG...BUT ALSO SHOWED CAP FROM 600MB TO 500MB. AN
OUTFLOW BOUNDARY FROM CONVECTION OVER THE EASTERN PLAINS HELPED
BREAK THE CAP WITH THE STORM OVER DENVER. STILL A SLIGHT CHANCE
FOR ADDITIONAL STORMS THIS EVENING...MAINLY OVER NORTHERN PARTS OF
THE FRONT RANGE WHERE THE OUTFLOW BOUNDARY IS CURRENTLY MOVING
NORTHWEST. WILL KEEP LOW POPS IN THROUGH THE EVENING AND THEN HAVE
THE FORECAST DRY AFTER MIDNIGHT. ADJUSTED POPS FOR THIS.

&&

.SHORT TERM...(THIS EVENING THROUGH THURSDAY)
ISSUED AT 242 PM MDT WED MAY 27 2015

CONVECTION OVER THE PLAINS HAS DEVELOPED WITH REPORTS OF SEVERE
OVER FAR EASTERN COLORADO THAT WILL CONTINUE THROUGH THE AFTERNOON
AND INTO THE EVENING HOURS. CLOSER TO THE FOOTHILLS STORMS WILL
BRING BRIEF HEAVY RAIN WITH SMALL HAIL AND WIND GUSTS TO 40 MPH.
FURTHER EAST ALONG A LINE FROM LIMON NORTH TO STERLING WILL BRING
INCREASED CHANCES OF SEVERE STORMS WITH HAIL UP TO 2 INCHES...WIND
GUSTS UP TO 60 MPH AND A POSSIBLE TORNADO. OVERNIGHT THE SURFACE
TROUGH WILL MOVE SOUTHEAST BRINGING SUBSIDENCE IN HELPING TO
STABILIZE CONVECTION.

FOR THURSDAY THE UPPER LEVEL TROUGH WILL MOVE SOUTH INTO COLORADO
KEEPING MOISTURE LEVELS HIGH OVER THE PLAINS. WITH TEMPERATURES
PROGGED TO BE 1 TO 2 DEGREES HIGHER TOMORROW INSTABILITY WILL ONCE
AGAIN BE HIGH ENOUGH TO AID IN THE DEVELOPMENT OF AFTERNOON
CONVECTION. MAIN THREATS WILL BE GUSTY WINDS AND LARGE HAIL OVER
THE PLAINS BY THE AFTERNOON.

.LONG TERM...(THURSDAY NIGHT THROUGH WEDNESDAY)
ISSUED AT 242 PM MDT WED MAY 27 2015

COLD FRONT WILL DROP ACROSS NORTHEASTERN COLORADO FRIDAY MORNING.
LATEST MODEL RUNS ARE PUTTING MORE EMPHASIS ON THE LEADING PART OF
THIS SHORTWAVE TROUGH THAT COMES THROUGH THURSDAY EVENING...TAKING
THE EDGE OFF OF THE LIFT FOR FRIDAY AS THE LOW LEVEL TEMPERATURE
GRADIENT WILL ALREADY BE THROUGH. THE SHIFT TO NORTHEAST WINDS IS
ALSO OUT OF PHASE WITH THE BEST MOISTURE...NOT COMING UNTIL LATE
IN THE DAY. IT STILL LOOKS WET WITH THE AIRMASS SATURATING
EVENTUALLY AND NEUTRAL STABILITY BY FRIDAY EVENING. TREND WAS A
LITTLE SLOWER WITH EVERYTHING AS WELL...I JUST MADE MINOR
ADJUSTMENTS TO THE TIMING. THREAT OF A WIDESPREAD HEAVY RAIN IS
LOOKING LOW NOW. THE 12Z GFS STILL HAD MORE THAN A HALF INCH OF
RAIN OVER THE NORTHERN FRONT RANGE FOOTHILLS...EVERYTHING ELSE IS
LIGHTER AND THE CONSENSUS IS NOW MORE LIKE A QUARTER INCH IN AND
NEAR THE MOUNTAINS...IN LINE WITH OUR CURRENT QPF FORECAST.

WITH THE SLIGHTLY SLOWER TIMING I HELD ON TO SOME POPS SATURDAY
MORNING. THERE SHOULD BE SHARP WARMING/DRYING ALOFT DURING THE
MORNING THOUGH...THEN JUST MARGINAL CONDITIONS FOR DIURNAL STORMS
IN THE AFTERNOON. STILL SOME SUNSHINE AND LOW LEVEL MOISTURE
REMAINING THOUGH. RIDGE BUILDS SUNDAY AND MONDAY FOR WARMER
TEMPERATURES...BUT STILL THE LOW LEVEL MOISTURE REMAINS SO LOW
POPS ARE IN ORDER. LATEST GUIDANCE IS WARMER AND MID LEVEL
TEMPERATURES SUPPORT 80S ON THE PLAINS...SO WENT AHEAD AND NUDGED
THESE DAYS A BIT HIGHER.

SOME QUESTIONS ABOUT THE UPSTREAM TROUGH. GFS EJECTS A WEAK
SHORTWAVE THAT PASSES OVER COLORADO WEDNESDAY. ENOUGH FOR
INCREASED LATE DAY CONVECTION STARTING TUESDAY EVENING...BUT
STILL GENERALLY A DRY ENVIRONMENT. ECMWF IS SLOWER WITH THIS
TROUGH AND HOLDS SOUTHWEST FLOW ALOFT OVER US. THIS COULD STILL BE
ENOUGH FOR SOME LEE TROUGHING TO GENERATE A DRYLINE AND SOME
UPTICK IN CONVECTION. FOR NOW A SLIGHT COOLING WITH LOW POPS IS IN
ORDER...HOLDING OFF ON ANYTHING MORE FOR NOW.

&&

.AVIATION...(FOR THE TAFS THROUGH 06Z THURSDAY EVENING)
ISSUED AT 748 PM MDT WED MAY 27 2015

THERE WILL BE A SLIGHT CHANCE FOR A THUNDERSTORM THROUGH 06Z...
NOT ENOUGH OF A CHANCE TO MENTION IN THE TAFS. WINDS WILL BE
SOUTHERLY AT KDEN AND KAPA THROUGH THURSDAY MORNING...15Z AND THEN
BECOME LIGHT AND VARIABLE. THERE WILL BE A CHANCE FOR
THURSDAY...AFTER 21Z.

&&

.HYDROLOGY...
ISSUED AT 242 PM MDT WED MAY 27 2015

FLOOD WARNINGS CONTINUE FOR THE SOUTH PLATTE RIVER AT KERSEY AS
WELL AS CACHE LA POUDRE AT GREELEY. RIVER READINGS ARE STILL AT OR
ABOVE FLOOD STAGE. BRIEF HEAVY RAIN WITH STORMS TODAY AND TOMORROW
ARE NOT EXPECTED TO ALTER THE CURRENT RIVER STAGE.

&&

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

$$

UPDATE...MEIER
SHORT TERM...BOWEN
LONG TERM...GIMMESTAD
AVIATION...MEIER
HYDROLOGY...BOWEN


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