Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 220952
AFDBOU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DENVER/BOULDER CO
252 AM MST SAT NOV 22 2014

.SHORT TERM...(TODAY THROUGH TONIGHT )
ISSUED AT 252 AM MST SAT NOV 22 2014

ACTIVE WEATHER PATTERN SETTING UP FOR THE SHORT TERM PERIOD AND
CONTINUING INTO EARLY NEXT WEEK. CURRENT OBSERVATIONS SHOW FLOW
ALOFT INCREASING IN THE EARLY MORNING HOURS IN ADVANCE OF POWERFUL
150-160 KNOT UPPER LEVEL JET COMING ASHORE THE CALIFORNIA/OREGON
COAST. THIS SPEED MAX WILL THEN DRIVE ACROSS THE GREAT BASIN
DURING THE AFTERNOON AND EVENING. STRONG UPPER LEVEL DIVERGENCE
COMBINED WITH AT LEAST WEAK BUT SUSTAINED Q-G LIFT AND PACIFIC
MOISTURE PLUME IS STILL ON TRACK TO REACH THE FORECAST AREA LATE
THIS AFTERNOON. SNOW WILL DEVELOP FIRST OVER THE MOUNTAINS OF
WESTERN JACKSON AND GRAND COUNTIES AROUND MID AFTERNOON AND THEN
SPREAD EAST ACROSS THE FRONT RANGE MOUNTAINS DURING THE LATE
AFTERNOON/EARLY EVENING HOURS.

INITIALLY...WEST/SOUTHWEST FLOW ALOFT WILL KEEP HEAVY SNOW LIKELY
CONFINED TO THE MOUNTAINS OF WESTERN JACKSON/GRAND COUNTIES IN
VICINITY OF RABBIT EARS PASS AND MOUNT ZIRKEL WILDERNESS...BUT AS
FLOW TURNS MORE WEST/NORTHWEST AND STRONGER COLD ADVECTION
ARRIVES LATE THIS EVENING INTO THE OVERNIGHT HOURS THE HEAVIER
SNOW BAND WILL SHIFT INTO THE I-70 CORRIDOR OF THE MOUNTAINS
INCLUDING SUMMIT COUNTY. THIS FIRST SHOT OF HEAVIER SNOWFALL IS
EXPECTED TO PRODUCE BETWEEN 4 AND 8 INCHES OVER MOST OF THE
MOUNTAINS BY LATE TONIGHT...WITH UP TO A FOOT FROM RABBIT EARS
PASS AREA NORTHWARD WHERE THE EARLY PORTIONS OF THIS STORM COULD
REALLY POUND THAT AREA WITH STRONG WESTERLY FLOW. GIVEN THE STRONG
FLOW...WE DO EXPECT SOME SPILLOVER SNOW TO AFFECT THE FRONT RANGE
FOOTHILLS MAINLY ALONG THE PEAK TO PEAK HIGHWAY WHERE A COUPLE
INCHES OF SNOW SHOULD ACCUMULATE. THIS TOO ALREADY HANDLED WELL IN
GOING FORECAST. STRONG WINDS WILL PRODUCE CONSIDERABLE BLOWING AND
DRIFTING SNOW AND POOR VISIBILITIES SO EARLIER ISSUED WINTER STORM
WARNINGS FOR ELEVATIONS ABOVE 9000 FEET ARE ON TRACK. HIGH
MOUNTAIN VALLEYS INCLUDING WALDEN AND KREMMLING WILL SEE LIGHTER
SNOW BUT GUSTY WINDS FOR SOME BLOWING SNOW. AT THIS TIME...THE
PERIOD OF MORE SIGNIFICANT SNOWFALL IN VALLEY LOCATIONS IS SEEN TO
BE TOO SHORT AND AMOUNTS SHY OF ADVISORY CRITERIA...BUT WILL BE
MONITORED.

ON THE PLAINS...THERE ARE MORE INDICATIONS FOR A POTENTIAL WEAK
ANTICYCLONE TO DEVELOP TONIGHT JUST BEHIND FRONTAL PASSAGE. THAT
WOULD BRING A BETTER CHANCE OF SNOW TO THE PLAINS SO HAVE
INCREASED POPS JUST A BIT FROM THE DENVER METRO AREA
EAST/SOUTHEAST TOWARD AKRON AND LIMON. WARM ENOUGH INITIALLY IN
THE LOWER ELEVATIONS FOR A MIX OF LIGHT RAIN/SNOW IF WE SEE PRECIP
DEVELOP.

WITH REGARD TO WIND...THE CROSS MOUNTAIN FLOW INCREASES TO AROUND
35 KTS AND A RATHER STRONG MOUNTAIN TOP STABLE LAYER THIS MORNING
SHOULD RESULT IN FAVORABLE MOUNTAIN WAVE PROFILE. CHINOOK PATTERN
IN PLACE SO STRONGER AND OCCASIONAL GUSTS MAINLY IN THE 45 TO 55
MPH RANGE SHOULD STAY CONFINED TO LOCATIONS IN/RIGHT NEXT TO THE
FOOTHILLS. WINDS INCREASE FURTHER LATER THIS AFTERNOON/EVENING BUT
MOUNTAIN WAVE STRUCTURE IS EXPECTED TO BREAK DOWN AS MOUNTAIN TOP
STABILITY DECREASES.

TEMPERATURES WILL BE QUITE MILD FROM THE FOOTHILLS DOWN ONTO THE
PLAINS WITH WARM ADVECTION AND INCREASING DOWNSLOPE COMPONENT.
DENVER METRO SHOULD SEE 60F AS LONG AS MOUNTAIN WAVE CLOUDS DONT
THICKEN TOO QUICKLY. MOST GUIDANCE SHOWS GENERALLY THIN BAND OF
MOUNTAIN WAVE CLOUDS TIL AFTERNOON WHEN MORE WIDESPREAD CLOUDINESS
WILL DEVELOP.

.LONG TERM...(SUNDAY THROUGH FRIDAY)
ISSUED AT 252 AM MST SAT NOV 22 2014

NWLY FLOW ALOFT WILL CONTINUE ON SUN AS AN UPPER LEVEL TROUGH
DEEPENS OVER THE CNTRL AND NRN US.  CROSS-SECTIONS SHOW MOISTURE
DEPTH WILL DECREASE SOME IN THE MTNS HOWEVER LAPSE RATES WILL BE IN
THE 7-8 C/KM RANGE SO OROGRAPHIC SNOW WILL CONTINUE THRU THE DAY
WITH AREAS OF BLOWING SNOW OVER THE HIGHER PASSES.  AT LOWER
ELEVATIONS WILL SEE A BORA TYPE FNT MOVE ACROSS THE PLAINS EARLY
WITH GUSTY NWLY WINDS THRU THE AFTN.  HIGHS WILL DROP BACK INTO THE
LOWER TO MID 40S OVER NERN CO.

FOR SUN NIGHT INTO MON NWLY FLOW ALOFT WILL CONTINUE AS A FEW
DISTURBANCES EMBEDDED IN THE FLOW MOVE ACROSS.  CROSS-SECTIONS SHOW
MOISTURE DEPTH INCREASING IN THE MTNS BY 12Z MON WHICH WILL CONTINUE
THRU THE AFTN.  LAPSE RATES WILL REMAIN IN THE 7-8 C/KM RANGE WITH
FAVORABLE OROGRAPHIC COMPONENT SO WILL SEE PERIODS OF MDT TO HEAVY
SNOW.  WINDS WILL REMAIN GUSTY AS WELL WITH BLOWING SNOW ESPECIALLY
ABV 10000 FT.  AT LOWER ELEVATIONS A WK MTN WAVE MAY SET UP LATE SUN
NIGHT INTO EARLY MON MORNING AS COMPONENT ALONG WINDS INCREASE TO
AROUND 50 KTS.  THUS THERE MAY BE SOME POTENTIAL FOR A MARGINAL HIGH
WIND EVENT IN THE FOOTHILLS BETWEEN 06Z AND 15Z.  OTHERWISE IT WILL
REMAIN WINDY OVER THE PLAINS THRU THE AFTN HOURS WITH GUSTY NNW
WINDS.  AS FAR AS PCPN THERE IS SOME POTENTIAL FOR A CHC OF -SHSN
MON AFTN OVER NERN CO AS A DISTURBANCE TRACKS ACROSS.  LAPSE RATES
OVER NERN CO ARE FCST TO BE IN THE 8-9 C/KM RANGE.  BEST CHC WILL
PROBABLY BE EAST OF I-25 AND OVER THE PALMER DIVIDE AS AREAS NR THE
FOOTHILLS WILL BE FIGHTING STRONG DOWNSLOPE COMPONENT.  AS FOR HIGHS
850-700 MB COOL A FEW MORE DEGREES SO WILL KEEP READINGS IN THE
UPPER 30S TO LOWER 40S.

BY MON NIGHT MOISTURE WILL BEGIN TO DECREASE IN THE MTNS WITH
STABILITY INCREASING SO SNOW SHOULD DECREASE IN BOTH COVERAGE AND
INTENSITY.  MEANWHILE WITH MTN TOP STABILITY INCREASING INTO TUE
MORNING MAY SEE ANOTHER ROUND OF STRONGER WINDS IN THE MTNS AND
FOOTHILLS.  ON TUE THE FLOW ALOFT WILL REMAIN NWLY WITH MOISTURE
INCREASING IN THE MTNS.  LAPSE RATES ARE ONLY FCST TO BE IN THE 4-5
C/KM RANGE SO ADDITIONAL SNOW AMOUNTS SHOULD BE ON THE LIGHT SIDE.
OVER NERN CO GUSTY NWLY WINDS WILL CONTINUE OVER THE PLAINS.  HIGHS
WILL BE IN THE MID TO UPPER 40S ACROSS NERN CO.

FOR TUE NIGHT AXIS OF STRONGER UPPER LEVEL WINDS IN NWLY FLOW ALOFT
WILL BE OVER NERN CO WITH SOME MID LVL MOISTURE EMBEDDED IN THE
FLOW.  THUS COULD SEE A SLIGHT CHC OF -SHSN MAINLY NR THE WY-NE
BORDER.  IN THE MTNS EXPECT SOME LINGERING LIGHT SNOW TUE NIGHT DUE
TO FAVORABLE OROGRAPHICS.  ONCE AGAIN THERE WILL BE SOME POTENTIAL
FOR HIGH WINDS IN THE MTNS AND FOOTHILLS TUE NIGHT INTO WED MORNING
AS MTN WAVE INTENSIFIES AND COMPONENT ALONG WINDS INCREASE TO 50-55
KTS. ON WED WILL KEEP IN A CHC OF -SHSN IN THE MTNS WHILE OVER
NERN CO WILL HAVE A DRY FCST WITH HIGHS IN THE IN THE UPPER 40S
TO LOWER 50S. WINDS WILL REMAIN GUSTY AT TIMES ESPECIALLY NR THE
WY-NE BORDER AREA.

FOR WED NIGHT INTO THANKSGIVING THE DIVERGENCE BETWEEN THE ECMWF AND
GFS CONTINUES. THE ECMWF HAS AN UPPER LEVEL RIDGE BUILDING INTO THE
AREA WITH MUCH WARMER TEMPS IN THE 60S OVER NERN CO AND DRY
CONDITIONS.  MEANWHILE THE GFS HAS NRN CO IN NWLY FLOW ALOFT AS A
COLD FNT MOVES INTO NERN CO BY THU MORNING WITH HIGHS ONLY IN THE
30S.  THERE IS SOME MOISTURE BEHIND THE FNT WHICH COULD LEAD TO A
SLIGHT CHC OF SNOW IF IT DOES MOVE INTO NERN CO AS THE GFS SHOWS.
AT THIS POINT NOT SURE WHAT TO BELIEVE SO WILL KEEP READINGS IN THE
UPPER 40S TO LOWER 50S FOR NOW AND KEEP A DRY FCST TO REMAIN
CONSISTENT WITH SURROUNDING OFFICES.  ON FRI THE GFS KEEPS A SHALLOW
LYR OF COLD AIR OVER NERN CO WHICH WOULD KEEP HIGHS MAINLY IN THE
30S OVER THE PLAINS WHILE THE ECMWF HAS READINGS IN THE 60S.  AS FOR
PCPN NEITHER MODEL HAS MUCH MOISTURE SO WILL KEEP DRY FCST IN
PLACE.

&&

.AVIATION...(FOR THE TAFS THROUGH 12Z SUNDAY MORNING)
ISSUED AT 252 AM MST SAT NOV 22 2014

SOUTHWEST WINDS AROUND 10-15 KNOTS AT KDEN AND KAPA ARE EXPECTED
TO TURN MORE WESTERLY BY 20Z-23Z. HOWEVER...MOUNTAIN WAVE ACTIVITY
WILL KEEP A CHANCE OF LIGHT EASTERLY FLOW AT TIMES THROUGH THE
DAY...AND ALSO POTENTIAL FOR A FEW WESTERLY GUSTS TO AROUND 25
KTS. MEANWHILE...KBJC WILL LIKELY STRONGER WESTERLY WINDS PREVAIL
WITH GUSTS AROUND 30 KTS POSSIBLE THROUGHOUT THE DAY DUE TO
MOUNTAIN WAVE. FOR TONIGHT...WINDS ARE EXPECTED TO TURN MORE
NORTHWESTERLY TOWARD 06Z-10Z WITH FRONTAL PASSAGE. SLIGHT CHANCE
OF A PASSING LIGHT RAIN/SNOW SHOWER AFTER FRONT ESPECIALLY IF
WINDS TURN MORE NORTHERLY. VFR CONDITIONS WILL PREVAIL WITH
GRADUAL THICKENING OF CLOUDS WITH CEILINGS LOWERING FROM AROUND
20 THOUSAND FEET TO BRIEFLY AS LOW AS 5000-8000 FT 06Z-10Z
SUNDAY.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WARNING FROM 5 PM THIS AFTERNOON TO 5 PM MST MONDAY
FOR COZ031-033-034.

&&

$$

SHORT TERM...BARJENBRUCH
LONG TERM...RPK
AVIATION...BARJENBRUCH



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