Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 240503
AFDBOU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DENVER/BOULDER CO
1003 PM MST SUN NOV 23 2014

.UPDATE...
ISSUED AT 955 PM MST SUN NOV 23 2014

SNOWFALL HAS EASED ACROSS THE HIGH COUNTRY THIS EVENING AS MANY
WEATHER CAMS AND SFC OBSERVATIONS ARE ONLY INDICATING LIGHT
SPORATIC SNOWFALL AT THIS TIME. THE MTN TOP LAYER HAS DRIED AND
STABILIZED SOME RESULTING IN THIS DROP OFF IN PRECIP. WINDS
LIKEWISE HAVE WEAKENED THIS EVENING...ALTHOUGH A FEW HIGH MTN
REPORTING SITES ARE STILL MEASURING GUSTS IN THE 35-45KT RANGE.
MEANWHILE SKIES CONTINUE TO CLEAR ON THE PLAINS WITH ONLY A FEW
SNOW FLURRIES HANGING ON OVER THE PALMER DIVIDE AND UP AGAINST THE
FOOTHILLS. THEY TOO SHOULD COME TO AN END IN THE NEXT HOUR OR SO.

ATTENTION NOW TURNS TO THE COLD POOL CONVECTION/PRECIPITATION
BLOSSOMING OVER ERN IDAHO/WRN WYOMING AT THIS TIME. QG VERTICAL
VELOCITY FIELDS INDICATE WEAK TO MODERATE DEEP LAYER ASCENT WITH
THIS FEATURE. MODELS SHOW THIS EXPANDING AREA OF PRECIP RACING
SOUTHEAST AND REACHING NORTHWEST COLORADO BY AROUND MIDNIGHT.
MODELS TRACK THIS LIFT AND MOISTURE SOUTHEASTWARD OVER THE NORTH-
CENTRAL AND WEST CENTRAL MTNS OF COLORADO LATE TONIGHT AND FINALLY
ACRS SOUTH CENTRAL/SOUTHEAST COLORADO BY MID-MORNING MONDAY. WITH
ITS PASSAGE...SHOULD SEE SNOWFALL RESUMING IN OUR MOUNTAIN AREAS
AND PROBABLY BECOMING HEAVY AT TIMES LATE TONIGHT AND EARLY
MONDAY MORNING. SNOWFALL RATES OF 1-2 INCHES PER HOUR NOT OUT OF
THE QUESTION ON THE HIGHER PASSES/RIDGES DURING THIS PERIOD. IN
ADDITION SHOULD SEE WEST-SOUTHWESTERLY WINDS INCREASING THROUGH
10Z/TONIGHT WITH GUSTS TO AROUND 45KTS PRODUCING BLOWING SNOW
LEADING TO POOR VISIBILITIES ON THE HIGH PASSES. FOR THESE
REASONS...WILL HANG ONTO THE WINTER STORM WARNING EVEN IN THE
MIDST OF THE CURRENT LULL IN PRECIP AND WIND. FINALLY SHOULD SEE
SWLY FLOW ALOFT BECOMING NWLY AND STRONGER WITH PASSAGE OF THE
WEATHER DISTURBANCE. AS A RESULT SHOULD DOWNSLOPE WIND SPEEDS
INCREASING LEE SLOPE OF THE FRONT RANGE. MODEL CROSS SECTIONS
SHOW 45-55KT CROSS MTN W-NWLY FLOW MOVING DOWNSLOPE AND POSSIBLY
REACHING THE LOWER FOOTHILLS BY 12Z...IF NOT SOONER. COULD SEE
GUSTS IN THE 40-50 MPH RANGE IN HIGH WIND PRONE AREAS NEAR THE
BASE OF THE FOOTHILLS BY MORNING.

&&

.SHORT TERM...(THIS EVENING THROUGH MONDAY)
ISSUED AT 329 PM MST SUN NOV 23 2014

SOME SNOW SHOWERS ON THE RADAR RIGHT NOW. BEST OVER THE HIGH
MOUNTAINS...WITH A FEW OVER THE FOOTHILLS AND IMMEDIATE PLAINS.
THERE IS A FAIRLY STRONG NORTH-NORTHWESTERLY WIND FIELD OVER MOST
OF THE PLAINS RIGHT NOW. THERE ARE SOME GUSTS TO AROUND 35 KNOTS
OVER THE NORTHERN AND EASTERN PLAINS. MODELS SHOW THE UPPER TROUGH
AXIS THROUGH THE CWA WITH NORTHWESTERLY FLOW ALOFT TONIGHT AND
MONDAY. THE SPEEDS ARE 40 TO 70 KNOTS AND INCREASING BY 00Z MONDAY
AFTERNOON LATE. THERE IS PRETTY STRONG DOWNWARD QG MOTION FOR THE
CWA BOTH TONIGHT AND MONDAY. THE BOUNDARY LAYER FLOW IS ALL
NORTHWESTERLY DOWNSLOPING FOR ALL THE CWA TONIGHT AND MONDAY. FOR
MOISTURE...IT STAYS PRETTY DEEP IN THE MOUNTAINS TONIGHT AND
MONDAY. AFTER THIS EVENING`S CONVECTION...THE PLAINS DO NOT HAVE
A LOT OF MOISTURE OVER THEM. IT INCREASES ON MONDAY...ESPECIALLY
JUST EAST OF THE URBAN CORRIDOR IN THE MORNING...THEN MOISTURE IS
PRETTY GOOD OVER ALL THE PLAINS BY AFTERNOON. THE QPF FIELDS SHOW
MEASURABLE SNOWFALL TONIGHT AND MONDAY IN THE MOUNTAINS...WITH A
TAD OVER THE PLAINS MONDAY AFTERNOON. FOR POPS...WILL GO
WIDESPREAD FOR THE MOUNTAINS TONIGHT AND MONDAY CONTINUING THE
HIGHLIGHTS FOR THE THREE HIGH MOUNTAIN ZONES. NO OTHER HIGHLIGHTS.
FOR THE WESTERN HALF OF THE PLAINS EARLY THIS EVENING...10-30%S.
ON MONDAY AFTERNOON WILL GO WITH 20%S FOR THE PLAINS FOR SNOW
SHOWERS. FOR TEMPERATURES...MONDAY`S HIGHS ARE CLOSE TO A TAD
COOLER THAN TODAY`S.

.LONG TERM...(MONDAY NIGHT THROUGH SUNDAY)
ISSUED AT 329 PM MST SUN NOV 23 2014

A STRING OF SHORTWAVES CONTINUES TO MOVE THROUGH THE NORTHWEST
FLOW ALOFT THIS WEEK. STILL GOOD AGREEMENT ON THE RIDGE GRADUALLY
BUILDING UPSTREAM DURING THE WEEK WITH FLOW GOING MORE WESTERLY AS
IT UNDERCUTS THE RIDGE BY THIS WEEKEND. STILL HUGE DISAGREEMENTS
ON THE EXACT DETAIL OF HOW FAR NORTH THE BAROCLINIC ZONE WITH BIG
IMPLICATIONS FOR TEMPERATURES AND ANY THREAT OF SNOW FROM THURSDAY
ON.

MAIN CHANGE IN THE SHORT TERM WAS TO BEEF UP THE CHANCE OF SNOW IN
THE MOUNTAINS AS THE MOISTURE RETREATS NORTHWARD MORE SLOWLY THAN
PREVIOUSLY FORECAST. THIS WILL GENERALLY BE LIGHT...AND STABILITY
GOES AWAY AS WARM ADVECTION ALOFT KICKS IN. HOWEVER MOISTURE AND
WIND ARE BOTH SUBSTANTIAL TUESDAY NIGHT...AND THERE IS MOIST WARM
ADVECTION AT MID LEVELS...SO THERE SHOULD BE MORE WIDESPREAD SNOW
WITH SOME ACCUMULATION. FOR THE PLAIN I REINTRODUCED SOME 10-20
PERCENT CHANCES AS THE SHORTWAVES PASS MONDAY EVENING AND AGAIN
LATE TUESDAY...BUT IF THESE DO DEVELOP THEY SHOULD ONLY BE LIGHT
SHOWERS.

THERE WILL ALSO BE A FAVORABLE PERIOD FOR AN AMPLIFIED MOUNTAIN
WAVE. THIS LOOKS BEST LATE MONDAY NIGHT THROUGH THE DAY
TUESDAY...THEN IT WILL REMAIN WINDY INTO WEDNESDAY BUT THE
PROSPECTS FOR AMPLIFICATION WILL BE LESS. LOOKS LIKE A DECENT HIGH
WIND THREAT FOR THE FRONT RANGE MOUNTAINS AND FOOTHILLS. PLAINS
WILL BE WINDY BUT MAINLY DUE TO MIXING AND DOES NOT LOOK LIKE A
HIGH WIND THREAT THERE EXCEPT SOME STEADY  THE MOUNTAIN WAVE HOT
SPOTS RIGHT NEXT TO THE FOOTHILLS. WEDNESDAY IS A WARM DAY WITH
DECREASING WINDS.

WE STILL HAVE THE SAME DILEMMA WITH THE POSITION OF THE COLD FRONT
AND JET FOR THURSDAY INTO THE WEEKEND. OPERATIONAL RUNS CONTINUE
TO HOLD THE FRONT STALLED ACROSS NEBRASKA ON THURSDAY...THEN
SAGGING A LITTLE BY FRIDAY...THEN PULLING BACK TOWARD THE
NORTHEAST AS THE FLOW ALOFT GOES MORE WESTERLY THIS WEEKEND.
CRITICAL QUESTION IS HOW MUCH SOUTHWARD PROGRESS THE FRONT MAKES
AND HOW SOON. MODELS CONTINUE TO OSCILLATE WITH MOST OF THE
ENSEMBLE RUNS COLDER...AND SOME QUITE COLD. FOR EXAMPLE THE 12Z
OPERATIONAL GFS MOS HAS A HIGH OF 70 IN DENVER FRIDAY WHILE THE
OPERATIONAL ECMWF MOS BRING THE COLD AIR IN STRONGLY AND HAS A
HIGH OF 27. SINCE THESE FRONTS DO TEND TO DROP SOUTH MORE THAN THE
MODELS SHOW...WE WILL CONTINUE TO HEDGE DOWNWARD BELOW THE
OPERATIONAL GFS. IT COULD EASILY BE 10 DEGREES WARMER...OR 20
DEGREES COLDER...OR PERHAPS BOTH SOMEWHERE IN OUR AREA. THERE IS
ALSO A SMALL CHANCE OF LIGHT RAIN OR SNOW AS THE JET OVERRUNS THE
FRONT...BUT ODDS OF ANYTHING SIGNIFICANT IN OUR AREA CONTINUE TO
LOOK PRETTY SMALL.

&&

.AVIATION...(FOR THE TAFS THROUGH 06Z MONDAY EVENING)
ISSUED AT 955 PM MST SUN NOV 23 2014

VFR CONDITIONS EXPECTED AT DENVER AREA TERMINALS FOR THE REMAINDER
OF THE NIGHT. SHOULD ALSO SEE MID AND HIGH CLOUDS SPREADING OVER
THE AREA LATER TONIGHT AS A WEATHER SYSTEM TO OUR NORTHWEST MOVES
CLOSER TO THE AREA. DO NOT SEE ANY SNOWFALL IN THE METRO AREA
THROUGH LATE MORNING. THEN PARTS OF THE DENVER METRO AREA
INCLUDING DIA COULD SEE A FEW LIGHT RAIN SHOWERS OR RAIN/SNOW
SHOWERS DURING THE AFTERNOON HOURS. SNOW ACCUMULATION IS NOT
ANTICIPATED. AS FOR WINDS...TERMINALS WILL CONTINUE TO SEE WEST-
SOUTHWEST WINDS OF 7-16KTS OVERNIGHT...WITH KBJC NEAR THE
FOOTHILLS POSSIBLY SEEING GUSTS TO AROUND 45 MPH TOWARDS MORNING.
WINDS THROUGH THE DAY MONDAY WILL BECOME NORTHWESTERLY AT
10-20KTS WITH GUSTS IN THE 25-35KT RANGE DURING THE AFTERNOON.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WARNING UNTIL 5 PM MST MONDAY FOR COZ031-033-034.

&&

$$

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



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