Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 222140
AFDBOU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DENVER/BOULDER CO
340 PM MDT FRI MAY 22 2015

.SHORT TERM...(THIS EVENING THROUGH SATURDAY)
ISSUED AT 340 PM MDT FRI MAY 22 2015

AREAS OF RAIN FROM THIS MORNINGS UPPER DISTURBANCE HAVE JUST ABOUT
CLEARED THE NORTHERN PARTS OF THE FORECAST AREA WHILE AN AREA
SHOWERS AND THUNDERSTORMS HAS DEVELOPED OVER THE PALMER DIVIDE.
CONVECTION THAT HAS BEEN FORMING IN THE WARM AIR ON THE SOUTH SIDE
OF THE PALMER DIVIDE HAS BEEN WEAKENING AS IT PROGRESSES INTO THE
COOLER AIR PRESENT OVER THE NORTHERN SIDE OF THE DIVIDE.
ADDITIONAL SHOWERS SHOULD CONTINUE DEVELOPING FOR A FEW MORE HOURS
WITH THUNDER STILL POSSIBLE DUE TO ELEVATED INSTABILITY. SHOWERS
ARE MOVING FAST ENOUGH THAT FLASH FLOODING RAINS ARE NOT A THREAT.
SHOWERS SHOULD END THIS EVENING AS THE AIRMASS COOLS FURTHER AND
STABILIZES.

OVERNIGHT...LIGHT EASTERLY FLOW AND THE MOIST BOUNDARY LAYER
SHOULD ALLOW AREAS OF FOG AND STRATUS TO DEVELOP. FOR
TOMORROW...THE MAIN UPPER LEVEL LOW WHICH IS CURRENTLY OVER
ARIZONA WILL BE EJECTING OVER WESTERN COLORADO TOMORROW AFTERNOON.
STRONG DYNAMICS ASSOCIATED WITH THIS FEATURE WILL COMBINE WITH
ABUNDANT LOW LEVEL MOISTURE AND A DEEPENING SURFACE LOW TO SET THE
STAGE FOR AN OUTBREAK OF SEVERE THUNDERSTORMS ACROSS THE PLAINS.
HAVE INCREASED POPS TO THE LIKELY CATEGORY AND ALSO MENTIONED THAT
SOME STORMS MAY BE SEVERE. HEAVY RAIN FROM THESE STORMS MAY CAUSE
LOCALIZED FLOODING PROBLEMS. STAY TUNED FOR THE LATEST FORECAST
PRODUCTS.

.LONG TERM...(SATURDAY NIGHT THROUGH FRIDAY)
ISSUED AT 340 PM MDT FRI MAY 22 2015

SHOWERS AND THUNDERSTORMS CONTINUE ACROSS NORTH CENTRAL AND
NORTHEASTERN COLORADO SATURDAY NIGHT AS THE UPPER LEVEL LOW MOVES
ACROSS THE STATE. THE ACTIVITY WILL BE MOST NUMEROUS NORTH OF
INTERSTATE 70...WITH A THREAT OF SEVERE STORMS MAINLY NORTH AND EAST
OF DENVER DURING THE EVENING. THERE WILL BE THE POTENTIAL FOR
ADDITIONAL FLOODING AS LOCALLY HEAVY RAINFALL WILL BE POSSIBLE. THE
UPPER LOW WILL LIFT NORTH INTO NORTHEASTERN WYOMING AND WESTERN
SOUTH DAKOTA BY SUNDAY EVENING. COULD SEE SOME LOW CLOUD...DRIZZLE
AND FOG SUNDAY MORNING ON THE PLAINS...WITH SCATTERED SHOWERS AND
THUNDERSTORMS BY AFTERNOON. LESS SHEAR AND INSTABILITY SHOULD KEEP
STORMS BELOW SEVERE LEVELS.

IN THE MOUNTAINS...RAIN AND SNOW WILL BE LIKELY AS MOISTURE ON THE
BACK SIDE OF THE LOW WRAPS INTO NORTH CENTRAL COLORADO. THE SNOW
LEVEL WILL REMAIN ABOVE 8500 FEET WITH A FEW INCHES OF SNOW POSSIBLE
ABOVE 10 THOUSAND FEET.

ON MONDAY THE ATMOSPHERE DRIES OUT SOMEWHAT AS THE FLOW BECOMES MORE
ZONAL. HOWEVER...THERE SHOULD BE ENOUGH RESIDUAL MOISTURE COMBINED
WITH DAYTIME HEATING TO PRODUCE ISOLATED TO SCATTERED SHOWERS AND
THUNDERSTORMS...MOST NUMEROUS OVER THE MOUNTAINS. WARMER AND DRIER
WEATHER IS EXPECTED ON TUESDAY...AS AN UPPER LEVEL RIDGE OF HIGH
PRESSURE BUILDS OVER THE ROCKY MOUNTAIN REGION. LOW LEVEL MOISTURE
AND SHEAR LOOKS TO BE LIMITED WITH THE MODELS SHOWING INVERTED V
SOUNDINGS. THIS WOULD RESULT IN GUSTY THUNDERSTORMS WITH LIGHT TO
MODERATE RAINFALL...HOWEVER A FEW STRONGER STORMS CAN NOT BE RULED
OUT. SHOWERS AND STORMS WILL INCREASE SOMEWHAT BY WEDNESDAY AS AN
UPPER TROUGH APPROACHES COLORADO FROM THE WEST. GFS SOUNDING SHOW
CAPES ACROSS FAR NORTHEAST PLAINS ABOVE 2000 J/KG AND SOME SHEAR.
THEREFORE...WOULDN`T BE SURPRISED TO SEE SOME SEVERE STORMS OVER
PORTIONS OF THE PLAINS.

SLIGHTLY COOLER TEMPERATURES AND SCATTERED SHOWERS AND THUNDERSTORMS
ARE EXPECTED ON THURSDAY AS THE WEAK UPPER TROUGH MOVES ACROSS
COLORADO. ON FRIDAY...THE UPPER LOW MOVES INTO THE CENTRAL PLAINS
STATES...WITH A NORTHWEST FLOW ALOFT SETTING UP OVER COLORADO.
COOLER UNSETTLED WEATHER IS EXPECTED TO RETURN BY FRIDAY
AFTERNOON...AS A COLD FRONT MOVES INTO NORTHEASTERN COLORADO. THE
GFS IS STRONGER WITH THE FRONT AND HAS MORE PRECIPITATION ALONG THE
FRONT RANGE URBAN CORRIDOR THAN THE ECMWF. HAVE DECIDED TO RAISE
POPS SOMEWHAT DURING THIS PERIOD.

&&

.AVIATION...(FOR THE TAFS THROUGH 00Z SATURDAY LATE AFTERNOON)
ISSUED AT 340 PM MDT FRI MAY 22 2015

THE THREAT OF RAIN SHOWERS ONE OR TWO THUNDERSTORMS WILL CONTINUE
IN THE EARLY EVENING. MVFR CONDITIONS WILL BE POSSIBLE AS SHOWERS
MOVE OVER. OVERNIGHT...LIGHT EASTERLY FLOW AND A VERY MOIST
AIRMASS MAY LEAD TO THE DEVELOPMENT OF AREAS OF STRATUS AND FOG.
THIS MAY DROP CEILINGS AND VISIBILITIES TO LOW IFR FOR A FEW
HOURS BEFORE AND AFTER SUNRISE. TOMORROW AFTERNOON WILL FEATURE
SCATTERED THUNDERSTORMS WITH HEAVY RAIN AND MVFR CONDITIONS AT
TIMES.

&&

.HYDROLOGY...
ISSUED AT 340 PM MDT FRI MAY 22 2015

RAINFALL AMOUNTS EARLIER TODAY WERE LIGHT ENOUGH THAT ONLY SMALL
RISES HAVE BEEN REGISTERED ON LOCAL RIVERS. SPOTTY SHOWER ACTIVITY
THIS EVENING SHOULD NOT BE OF TOO MUCH ADDITIONAL CONSEQUENCE.
SOIL MOISTURE CONDITIONS WILL BE GIVEN AN 18-24 HOUR PERIOD TO
RECOVER THROUGH TOMORROW AFTERNOON. BUT WHEN THUNDERSTORMS DEVELOP
SATURDAY AFTERNOON...RUNOFF WILL BE FAST TO BEGIN. FLASH FLOODING
MAY BE A POSSIBILITY TOMORROW AFTERNOON AND EVENING...BUT IT IS
HARD TO TELL AT THIS TIME WHERE THE FOCUS OF HEAVY PRECIPITATION
IS GOING TO BE.

THE CACHE LA POUDRE AND SOUTH PLATTE RIVERS REMAIN ABOVE FLOOD
STAGE IN LARIMER AND WELD COUNTIES...AND WILL BE THAT WAY FOR A
COUPLE MORE DAYS.

&&

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

$$

SHORT TERM...DANKERS
LONG TERM...KALINA
AVIATION...DANKERS
HYDROLOGY...DANKERS



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