Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 181623
AFDBOU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DENVER/BOULDER CO
1023 AM MDT SAT APR 18 2015

.UPDATE...
ISSUED AT 1023 AM MDT SAT APR 18 2015

NOT MANY CHANGES TO THE FORECAST AT THIS TIME. THE CENTER OF THE
UPPER LOW HAS MOVED OVER LINCOLN COUNTY WITH A VORTICITY CENTER
HELPING TO KICK OFF SHOWERS AND A FEW THUNDERSTORMS EARLIER THIS
MORNING. AS THE VORTICITY CENTER CONTINUES ROTATING OVER THE
PLAINS...IT WILL COMBINE WITH SOME DAYTIME HEATING TO CONTINUE
PRODUCING SHOWERY ACTIVITY THAT MAY EVENTUALLY MAKE IT BACK TO THE
FOOTHILLS. ANOTHER BAND OF MOISTURE IN THE DEFORMATION REGION TO
THE NORTHWEST OF THE UPPER LOW WILL CONTINUE ROTATING INTO THE
NORTHERN MOUNTAINS THROUGH THE AFTERNOON. ADDITIONAL ACCUMULATING
SNOWFALL SHOULD CONTINUE THROUGH MUCH OF THE DAY WITH AMOUNTS UP
TO A FEW INCHES POSSIBLE. LATE MORNING FORECAST UPDATE WILL
CONTAIN ONLY MINOR CHANGES...CHIEFLY ADDING THE MENTION OF
ISOLATED AFTERNOON THUNDERSTORMS TO THE PLAINS THROUGH THE LATE
MORNING AND AFTERNOON.

&&

.SHORT TERM...(TODAY THROUGH TONIGHT )
ISSUED AT 512 AM MDT SAT APR 18 2015

UPPER LOW NEAR WALSENBURG AT THIS TIME TRACKING SLOWLY EAST. DRY
SLOT HAS CURLED AROUND ACROSS MOST OF EASTERN COLORADO WITH
MOISTURE WRAPPING BACK FROM WYOMING INTO THE COLORADO MOUNTAINS.
AT THIS TIME THE BACK PART OF THIS SYSTEM DOES NOT HAVE STRONG
LIFT WITH IT...BUT THIS IS EXPECTED TO INCREASE DURING THE DAY AS
EVERYTHING CONTINUES TO SPIN AROUND THE LOW CENTER MOVING SLOWLY
EAST. A COMPLEX PATTERN...BUT THE GOOD NEWS IS THE MODELS HAVE
PRETTY GOOD AGREEMENT ON THE BIG PICTURE. DETAILS OF JUST WHERE
THE BANDING STRUCTURE AND CONVECTION ARE VARY CONSIDERABLY. LIKING
THE HRRR PRESENTATION OF THE DEVELOPING BACK EDGE SNOW BAND ACROSS
THE MOUNTAINS...ROUGHLY FROM LARAMIE TOWARD RIFLE THIS MORNING.
HARD TO SAY IF THE NORTH CENTRAL MOUNTAINS WILL BE IN THE BEST OF
THIS...OR IF IT WILL STAY FURTHER WEST WITH THE DRIER AIR CURLING
BACK OVER THE FRONT RANGE. I DID INCREASE THE POPS FOR THE
MOUNTAINS...HELD OFF ON INCREASING AMOUNTS TOO MUCH AS THE SNOW
MAY TEND TOWARD LIGHT SHOWERS IN THE VALLEYS WITH A STEADY
BACKGROUND OF LIGHT OROGRAPHIC SNOW. IF THAT BAND WOBBLES FURTHER
EAST AN ADVISORY MAY BE NEEDED. MEANWHILE ON THE PLAINS THERE IS
DRIER AIR ALOFT...BUT THE LOW LEVELS REMAIN MOIST AND THE COLD
POOL ALOFT WILL BE OVER THIS AREA...AND THERE WILL BE SOME LIFT
FROM THE TIP OF THE WARM ADVECTION NEAR THE LOW CENTER. CONVECTION
SHOULD INCREASE THROUGH THE DAY. NOT AS MUCH OF A THUNDERSTORM
RISK TODAY...CAPES LIKELY AROUND 300 J/KG AROUND DENVER AND 600
NEAR THE EASTERN BORDER. I WOULD SAY NEGLIGIBLE SEVERE THREAT
EXCEPT FOR THE COLD TEMPERATURES...COULD BE SOME HAIL OUT EAST BUT
IT SHOULD BE HARD TO GET LARGE HAIL.

FOR TONIGHT THE BACK EDGE BAND WILL TRANSLATE ACROSS OUR AREA AS
THE LOW MOVES EAST. THIS SHOULD BRING A BETTER CHANCE OF
SHOWERS. NORTH WINDS ALSO INCREASING...WHICH COULD WARM/DRY AREAS
NORTH OF DENVER BUT ENHANCE THE THREAT OF SNOW SOUTH OF DENVER.
THE NORTH WIND SHOULD ALSO BRING A FEW DEGREES OF
COOLING...LOWERING SNOW LEVELS BACK DOWN TO 5-6 THOUSAND FEET.
HOWEVER AIR TEMPERATURES WILL STILL BE ABOVE FREEZING IN MOST
AREAS...SO STILL EXPECTING LITTLE IMPACT FOR THE METRO AREA.

.LONG TERM...(SUNDAY THROUGH FRIDAY)
ISSUED AT 512 AM MDT SAT APR 18 2015

THERE IS WEAK TO MODERATE NORTHWESTERLY JET LEVEL FLOW OVER THE
CWA SUNDAY THROUGH MONDAY NIGHT. THERE IS WEAK DOWNWARD SYNOPTIC
SCALE ENERGY FOR THE CWA SUNDAY...THEN BENIGN ENERGY SUNDAY NIGHT
THROUGH MONDAY NIGHT. THERE IS NORTHERLY FLOW IN THE LOWER LEVELS
ON SUNDAY...WITH WEAKER NORTHEASTERLIES SUNDAY NIGHT. BOUNDARY
LAYER WINDS ARE NORTHWESTERLY ON MONDAY...THEN A HINT AT NORMAL
DRAINAGE PATTERNS MONDAY NIGHT. FOR MOISTURE...THERE IS PLENTY FOR
THE CWA SUNDAY AND SUNDAY NIGHT...THE NAM BEING THE DRIEST. THERE
IS QUITE A BIT OF MOISTURE STILL AROUND BOTH MONDAY AND MONDAY
NIGHT...THE GFS BEING THE WETTEST. THERE IS A BIT OF CAPE OVER THE
FAR SOUTHWEST FORECAST AREA LATE DAY SUNDAY DAY. THERE IS A BIT
MORE CAPE OVER ALL THE HIGH COUNTRY LATE DAY MONDAY...BUT STILL
PRETTY MEAGER AMOUNTS. THE QPF FIELDS HAVE SOME MEASURABLE
PRECIPITATION MOSTLY OVER THE WESTERN TWO-THIRDS OF THE CWA
SUNDAY AFTERNOON INTO MONDAY EVENING. FOR POPS...20-50%S ARE GOOD
SUNDAY INTO MONDAY...THE LOWER NUMBERS FOR THE PLAINS. FOR
TEMPERATURES...SUNDAY`S HIGHS ARE A BIT COLDER THAN TODAY`S BEHIND
THE COLD FRONT LATE TONIGHT...EARLY SUNDAY MORNING. MONDAY`S HIGHS
ONLY WARM UP 1-2 C FROM SUNDAY`S.  FOR THE LATER DAYS...TUESDAY
THROUGH FRIDAY...THERE IS AN UPPER RIDGE TUESDAY THROUGH THURSDAY
NOW ON THE MODELS. THE NEXT UPPER TROUGH LOOKS WEAKER THAN IT DID
ON YESTERDAY`S 00Z RUNS AND IT COMES THROUGH THURSDAY NIGHT AND
FRIDAY.

&&

.AVIATION...(FOR THE TAFS THROUGH 18Z SUNDAY MORNING)
ISSUED AT 1023 AM MDT SAT APR 18 2015

THE COOL...MOIST AND SLIGHTLY UNSTABLE AIRMASS WILL REMAIN OVER
NORTHEAST COLORADO THROUGH THIS AFTERNOON AND EVENING. MAY NEED TO
MENTION SOME THUNDERSTORMS AT THE DENVER AREA AIRPORTS THROUGH THE
AFTERNOON. WARMER DEW POINTS ARE MOVING INTO DENVER FROM THE
NORTHEAST SO THE THREAT OF SNOW IS GOING DOWN FOR THE REST OF THIS
AFTERNOON. STILL MAY SEE A MIX OF RAIN AND SNOW LATER TONIGHT AS
SHOWERS CONTINUE AND TEMPERATURES COOL DOWN. SHOWERS COULD BE LONG
LIVED THROUGH THE EVENING AS THE UPPER LOW PULLS OUT OF COLORADO
AND MOISTURE ON THE NORTHWEST SIDE OF THE LOW ROTATES INTO THE
DENVER AREA.

&&

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

$$

UPDATE...DANKERS
SHORT TERM...GIMMESTAD
LONG TERM...RJK
AVIATION...DANKERS


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