Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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000
FXUS65 KBOU 241857
AFDBOU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DENVER/BOULDER CO
1157 AM MST MON NOV 24 2014

.UPDATE...
ISSUED AT 1157 AM MST MON NOV 24 2014

ONLY MINOR CHANGES AT THIS TIME. STILL SNOWING FAIRLY HARD IN OUR
MOUNTAINS BUT THE QG FORCING WILL BE MOVING PAST IN THE NEXT
COUPLE OF HOURS SO IT SHOULD BECOME MORE SHOWERY AND LESS
WIDESPREAD. STARTING TO SEE SOME CONVECTIVE DEVELOPMENT ON THE
PLAINS AND THERE IS A LOT OF LIGHT SHOWER ACTIVITY OVER EASTERN
WYOMING BEHIND A WEAK PRESSURE SURGE. COOLER TEMPS...HIGHER
MOISTURE...AND STRONGER WINDS BEHIND THIS THAT WILL SPREAD ACROSS
THE PLAINS THIS AFTERNOON. AREAS NEAR THE FOOTHILLS WILL BE A BIT
SHELTERED BY A DOWNSLOPE COMPONENT SO EXPECT MOST OF THE SHOWERS
WILL BE JUST A LITTLE EAST OF THE FRONT RANGE CITIES. A DUSTING
POSSIBLE IN MANY PLACES...BUT ONLY PLACE I MIGHT EXPECT ANY MORE
SIGNIFICANT ACCUMULATION WOULD BE IF THE SHOWERS PERSIST AGAINST
THE TERRAIN ON THE PALMER DIVIDE. SOMETIMES ELBERT COUNTY IS
FAVORED IN NNW FLOW. TEMPS WILL GET A COUPLE DEGREES HIGHER THAN
WE HAD FORECAST IN THE NEXT HOUR OR TWO...THEN DROP ABOUT 10
DEGREES BY SUNSET.

STILL PLANNING TO LET THE WINTER STORM WARNING EXPIRE AT 5
PM...AND LEAVING THE HIGH WIND WATCH ALONE. THE WATCH IS LOOKING
GOOD THOUGH THERE MAY BE A THREAT BOTH A FEW HOURS EARLIER AND
LATER THAN THE TIME WE HAVE OUTLOOKED.

&&

.SHORT TERM...(TODAY THROUGH TONIGHT )
ISSUED AT 350 AM MST MON NOV 24 2014

SATELLITE SHOWS A NICE SHORT WAVE AND ASSOCIATED MOISTURE REACHING
COLORADO EARLY THIS MORNING. REGIONAL RADARS FROM GRAND JUNCTION
TO SALT LAKE TO RIVERTON AS WELL AS SURFACE OBSERVATIONS HAVE
SHOWN AN INCREASE IN SNOWFALL OVER THE LAST FEW HOURS. AS THIS
FEATURE MOVES INTO THE STATE...WE WILL SEE ANOTHER INCREASE IN
SNOWFALL ACROSS THE COLORADO HIGH COUNTRY EARLY THIS MORNING
WITH SNOWFALL RATES INCREASING SIGNIFICANTLY. FAVORABLE
OROGRAPHICS...SHARP LAPSE RATES AROUND 7.5 C/KM...DEEP
MOISTURE...AND FAVORABLE DENDRITIC GROWTH REGIME SHOULD SUPPORT
SNOWFALL RATES AROUND 1 INCH PER HOUR OVER FAVORED RIDGES FOR A
TIME THIS MORNING. BY EARLY AFTERNOON...THE SNOW RATES ARE
EXPECTED TO DECREASE AS THE AIRMASS BEGINS TO DRY BUT INSTABILITY
WILL STILL ALLOW FOR A FEW BRIEFLY HEAVY SHOWERS. ANOTHER 3-6
INCHES FOR TODAY LOOKS ON TRACK.

ON THE PLAINS...CLOUDS WILL LIKELY LIMIT DAYTIME HEATING BUT
ENOUGH MIXING WITH INCOMING SHORT WAVE AND COOLING ALOFT FOR A FEW
CONVECTIVE SHOWERS AGAIN. THEY MAY START AS EARLY AS 17Z-18Z AS
DISTURBANCE MOVE IN. OTHERWISE...LOOK FOR NEARLY A REPEAT OF
YESTERDAY WITH GUSTY NORTH/NORTHWEST WINDS THROUGH MUCH OF THE
DAY. THE STRONGEST WINDS WITH PEAK GUSTS OF 40-55 MPH WILL OCCUR
IN/NEAR THE FOOTHILLS EARLY THIS MORNING BUT DECREASING STABILITY
WILL BREAK DOWN THE CURRENT MOUNTAIN WAVE. THEN STRONGEST WINDS
WILL LIKELY SHIFT TO THE PLAINS ALONG AND EAST OF I-25 AS STRONGER
MIXING OCCURS.

FOR TONIGHT...SNOW SHOWERS WILL RAPIDLY DECREASE AS QUICK DRYING
AND SUBSIDENCE OCCUR BEHIND TODAYS SHORT WAVE. THIS SHOULD PERMIT
THE WINTER STORM WARNING FOR THE MOUNTAINS TO EXPIRE ON TIME AT
5 PM. WINDS BEGIN TO INCREASE TOWARD 12Z WITH POTENTIAL HIGH WIND
EVENT...SEE LONG TERM PORTION BELOW.

.LONG TERM...(TUESDAY THROUGH SUNDAY)
ISSUED AT 350 AM MST MON NOV 24 2014

STG NW FLOW ALOFT WILL REMAIN OVER THE AREA TUE INTO TUE NIGHT.
CROSS-SECTIONS CONTINUE TO SHOW MOISTURE EMBEDDED IN THE FLOW WITH
AIRMASS SATURATED UP TO 500 MB.  THUS WILL CONTINUE TO SEE
OROGRAPHIC SNOW IN THE MTNS THRU TUE NIGHT.  LAPSE RATES ARE RATHER
STABLE WHICH SHOULD KEEP AMOUNTS ON THE LIGHT SIDE HOWEVER STG WINDS
WILL PRODUCE CONSIDERABLE BLOWING SNOW.  THUS WILL LIKELY NEED A
SNOW/BLOWING SNOW ADVISORY ON TUE.

MEANWHILE WITH A MTN WAVE DEVELOPING ON TUE COMBINED WITH A
STRENGTHENING LOW LVL PRES GRADIENT THE POTENTIAL FOR HIGH WINDS
WILL INCREASE IN AND NR THE FOOTHILLS.  THE HIRES WRF HAS COMPONENT
ALONG WINDS INCREASING TO 70KTS AFTER 12Z WHICH CONTINUE INTO THE
AFTN HOURS.  SO WILL ISSUE A HIGH WIND WATCH FOR TUE IN AND NR THE
FOOTHILLS.  OVER NERN CO IT WILL BE WINDY AS WELL WITH NNW WINDS IN
THE 20 TO 30 MPH RANGE WITH A FEW HIGHER GUSTS.  AS FOR HIGHS WILL
KEEP READINGS IN THE UPPER 40S TO AROUND 50 OVER THE PLAINS.

FOR TUE NIGHT LIGHT SNOW AND BLOWING SNOW WILL CONTINUE IN THE MTNS
DUE TO FAVORABLE OROGRAPHICS.  HIGHS WIND POTENTIAL MAY CONTINUE
TUE NIGHT IN THE FOOTHILLS ALTHOUGH THE LOW LVL PRES GRADIENT DOES
DECREASE.  MEANWHILE A COLD FNT WILL MOVE INTO NERN CO TUE EVENING
AS A STG UPPER LEVEL JET RESIDES OVER THE PLAINS.  AS A RESULT THIS
MAY LEAD TO A CHC OF SNOW OVER THE PLAINS.  AT THIS TIME IT APPEARS
THE CHC OF SNOW WILL STAY EAST OF THE URBAN CORRIDOR DUE TO STG
DOWNSLOPE FLOW COMING OFF THE FOOTHILLS.

ON WED BRISK NW FLOW ALOFT WILL CONTINUE HOWEVER CROSS-SECTIONS
SHOW MOISTURE DECREASING IN THE MTNS SO SNOW CHANCES SHOULD
GRADUALLY END BY MIDDAY. HOWEVER IT WILL CONTINUE WINDY WITH AREAS
OF BLOWING SNOW. SFC LOW PRES WILL REDEVELOP NR THE FOOTHILLS AS
THE FNT REMAINS OVER THE FAR NERN PLAINS. AREAS ALONG THE FRONT
RANGE MAY WARM INTO THE MID TO UPPER 50S WHILE READINGS NR THE CO-
NE BORDER REMAIN IN THE 40S. MEANWHILE THERE STILL COULD BE SOME
THREAT OF HIGH WINDS IN THE FOOTHILLS ON WED ALTHOUGH THE MID LVL
FLOW WILL NOT BE AS STG.

FOR THANKSGIVING AND FRIDAY THERE IS FINALLY AGREEMENT BETWEEN THE
MODELS AS THE FLOW ALOFT BECOMES MORE ZONAL.  CROSS-SECTIONS SHOW
ONLY SOME HIGHER LVL MOISTURE EMBEDDED IN THE FLOW SO WILL ONLY
MENTION A SLIGHT CHC OF -SHSN IN THE MTNS WITH DRY CONDITIONS
ELSEWHERE.  WINDS WILL CONTINUE TO BE GUSTY OVER THE HIGHER TERRAIN
AND ACROSS THE PLAINS BOTH DAYS HOWEVER HIGH WIND THREAT LOOKS LOW
AT THIS TIME.  MEANWHILE WITH A DECENT SFC LEE TROUGH NOW FCST TO
RESIDE OVER ERN CO AND DOWNSLOPE WLY FLOW COMING OFF THE HIGHER
TERRAIN THIS WILL LEAD TO WARMER TEMPS.  READINGS BOTH DAYS COULD
RISE INTO THE 60S OVER MOST OF NERN CO BASED ON LATEST 850-700 MB
TEMPS.

BY SAT WLY FLOW ALOFT WILL REMAIN OVER THE AREA WITH ONLY SOME MID
AND HIGH LVL MOISTURE THUS WILL KEEP FCST DRY EXCEPT FOR A SLIGHT
CHC OF -SHSN IN THE MTNS.  THE FLOW ALOFT DOES INCREASE FRI NIGHT
INTO SAT WITH A STABLE LYR AT MTN TOP SO HIGH WIND THREAT MAY
INCREASE OVER THE HIGHER TERRAIN.  THE GFS SHOWS A COLD FNT MOVING
INTO NERN CO BY SAT AFTN WHILE THE ECMWF HAS IT MOVING IN SAT NIGHT.
DEPENDING ON THE TIMING OF THIS FNT TEMPS COULD EITHER REMAIN
SEVERAL DEGREES ABV NORMAL ON SAT OR DROP BACK TO NR SEASONAL LEVELS
OVER NERN CO.  ON SUN IT STILL LOOKS MAINLY DRY OVER THE AREA WITH
COOLER TEMPS ACROSS NERN CO DUE TO PASSAGE OF THE COLD FNT SO WILL
KEEP HIGHS IN THE 40S.

&&

.AVIATION...(FOR THE TAFS THROUGH 00Z TUESDAY LATE AFTERNOON)
ISSUED AT 1157 AM MST MON NOV 24 2014

SCATTERED SNOW SHOWERS EXPECTED THIS AFTERNOON ALONG WITH GUSTY
NORTH TO NORTHWEST WINDS. CEILINGS MAY REQUIRE INSTRUMENT
APPROACHES TO KDEN FOR A FEW HOURS...AND THERE MAY BE LOCALIZED
IFR CONDITIONS IN SHOWER BANDS BUT THEY WILL BE SHORT LIVED.
SHOWERS WILL BE OUT OF THE DENVER AREA BY 02Z.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
HIGH WIND WATCH FROM LATE TONIGHT THROUGH TUESDAY AFTERNOON FOR
COZ035-036-038-039.

WINTER STORM WARNING UNTIL 5 PM MST THIS AFTERNOON FOR COZ031-
033-034.

&&

$$

UPDATE...GIMMESTAD
SHORT TERM...BARJENBRUCH
LONG TERM...RPK
AVIATION...GIMMESTAD


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