Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 251108
AFDBOU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DENVER/BOULDER CO
408 AM MST TUE NOV 25 2014

.SHORT TERM...(TODAY THROUGH TONIGHT )
ISSUED AT 407 AM MST TUE NOV 25 2014

CROSS MOUNTAIN FLOW AND PRESSURE GRADIENTS ARE INCREASING EARLY
THIS MORNING AND WILL CONTINUE TO DO SO UNTIL AROUND NOON. THE
CROSS MOUNTAIN COMPONENT STRENGTHENS TO AROUND 50 KTS TODAY AND A
WELL DEFINED MOUNTAIN TOP STABLE LAYER WILL PROMOTE DEVELOPMENT OF
A HIGHLY AMPLIFIED MOUNTAIN WAVE. IN ADDITION...AS THE UPPER
LEVEL JET MAX PASSES OFF TO OUR NORTH BY 15Z-18Z...WE WILL ALSO BE
GETTING IN SUBSIDENT PORTION OF THE UPPER JET WHICH IS ALSO
FAVORABLE FOR HIGH WINDS...WHILE AT THE SAME TIME CROSS MOUNTAIN
PRESSURE GRADIENTS MAX OUT WITH DP/DN VALUES REACHING 225-250
WHICH IS VERY HIGH. THIS ALL PROMOTES A POTENTIALLY DAMAGING HIGH
WIND EVENT IN/NEAR THE FRONT RANGE FOOTHILLS TODAY...MOST LIKELY
PEAKING AROUND 18Z. GIVEN THE ABOVE MENTIONED PARAMETERS...A
COUPLE OF THE FAVORED HIGH WIND SPOTS COULD SEE GUSTS REACH 90-100
MPH.

WITH REGARD TO MOUNTAIN SNOW...THE LAPSE RATES ARE QUITE POOR FOR
MOST OF THE DAY WITH READINGS NEAR 3-4 C/KM. OROGRAPHIC SNOW
MODELS PRODUCES ONLY VERY LIGHT SNOW WITH THESE LAPSE RATES AS
VERTICAL MOTION RESPONSE TO OROGRAPHY IS POOR. HOWEVER...GIVEN THE
PROXIMITY OF THE UPPER LEVEL JET MOVING OVERHEAD ALWAYS HAVE TO
MAINTAIN SOME CAUTION SO GOING FORECAST IS ON TRACK. THERE IS ALSO
SOME IMPROVEMENT IN LAPSE RATES BY EVENING...SO 4-8 INCH AMOUNTS
FOR THE FRONT RANGE MOUNTAINS INTO SUMMIT COUNTY LOOKS
GOOD...WHILE RABBIT EARS PASS AREA COULD VERY WELL SEE ANOTHER
6-12 INCHES. WINTER WEATHER ADVISORY ALREADY ISSUED THROUGH
TONIGHT AND COULD SEE LOCAL BLIZZARD CONDITIONS DEVELOP IN EXPOSED
AREAS DUE TO STRENGTH OF WIND.

OTHER CONCERN IS THREAT OF SNOW ON THE PLAINS TONIGHT. CROSS
SECTIONS ALL POINT TO EITHER A SHALLOW LAYER OF POTENTIAL
INSTABILITY OR AT THE VERY LEAST A SHALLOW LAYER OF SLANTWISE
CONVECTION WITH PRESENCE OF CONDITIONAL SYMMETRIC INSTABILITY.
THERE IS ALSO A BACKDOOR COLD FRONT NOW SHOWN TO SLIP ALL THE WAY
BACK TO DENVER TOWARD MIDNIGHT SO ANYWHERE ALONG AND BEHIND THAT
FRONT THE SHALLOW UPSLOPE COULD BE ENOUGH TO PRODUCE SNOWFALL.
HAVE INCREASED POPS OVER THE PLAINS...WITH THE MOST LIKELY AREA TO
SEE AT LEAST SOME LIGHT SNOW ACCUMULATION OF AN INCH OR TWO
POSSIBLE FROM NORTHERN WELD COUNTY TOWARD FORT MORGAN. AGAIN...
CANT RULE OUT SNOW MAKING IT ALL THE WAY BACK TO DENVER SO
INTRODUCED SOME POPS CLOSER TO THE FRONT RANGE AS WELL.

WINDS SHOULD GRADUALLY DECREASE THIS EVENING AS MOUNTAIN TOP
STABLE LAYER LIFTS AND FLOW ALOFT/GRADIENT SLOWLY RELAX.

TEMPERATURES A WILD CARD TODAY WITH RATHER THICK MID/HIGH LEVEL
CLOUD DECK BUT STRONG DOWNSLOPE COMPONENT IN PLAY. SHAVED A FEW
DEGREES OFF MAINLY IN LOW LYING AREAS GIVEN CURRENT COLD TEMPS
AND THICKENING OF CLOUDS. THIS COULD ALSO AFFECT WIND PATTERNS ON
THE PLAINS AS WELL.

.LONG TERM...(WEDNESDAY THROUGH MONDAY)
ISSUED AT 407 AM MST TUE NOV 25 2014

NW FLOW ALOFT WILL CONTINUE ON WED WITH A GRADUAL DECREASE IN
MOISTURE IN THE MTNS.  LIGHT OROGRAPHIC SNOWS WILL CONTINUE IN THE
MORNING BUT SHOULD DIMINISH BY AFTN.  OVER NERN CO BACKSIDE OF UPPER
LEVEL JET WILL STILL BE OVER THE PLAINS IN THE MORNING AND WITH WEAK
UPSLOPE FLOW BEHIND FNT THERE WILL BE A CHC OF MORNING SNOW. AT
THIS TIME WILL KEEP BEST CHC EAST OF I-25. AS FAR AS WINDS THEY
WILL REMAIN GUSTY IN THE MTNS AND HIGHER FOOTHILLS HOWEVER THREAT
OF ADDITIONAL HIGH WINDS LOOK LOW AT THIS TIME. HIGHS OVER NERN CO
WILL RANGE FM THE UPPER 40S TO NR 50 AT DENVER TO THE UPPER 30S TO
LOWER 40S OVER THE FAR NERN CORNER.

FOR THANKSGIVING AND FRI THE FLOW ALOFT WILL BECOME MORE WLY WITH
ONLY SOME HIGHER LEVEL MOISTURE MOVING ACROSS.  THUS WILL NOT
MENTION ANY PCPN.  WITH SFC LEE TROUGH OVER ERN COLORADO AND
DOWNSLOPE WLY LOW LVL FLOW SHOULD SEE ABV NORMAL TEMPS BOTH DAYS
ACROSS NERN CO WITH READINGS IN THE 60S.  AS FOR HIGH WIND POTENTIAL
IN THE MTNS AND FOOTHILLS ALTHOUGH THERE IS A DECENT MTN WAVE WED
NIGHT INTO THU COMPONENT ALONG WINDS ARE ONLY IN THE 35 TO 40 KT
RANGE.  HOWEVER FOR THU NIGHT INTO FRI COMPONENT ALONG WINDS ARE
FCST TO RANGE FM 50-60KTS SO HIGH WIND POTENTIAL WILL INCREASE.

BY SAT LITTLE CHANGE EXPECTED AS THE FLOW ALOFT WILL CONTINUE WLY
WITH CROSS-SECTIONS SHOWING MOISTURE CONFINED TO THE UPPER LVLS.
THUS WILL KEEP FCST DRY. ONCE AGAIN WILL LIKELY SEE GUSTY WINDS
IN THE MTNS AND FOOTHILLS. OVER NERN CO SHOULD SEE ANOTHER MID DAY
WITH TEMPS IN THE 60S. FOR SUN A CDFNT IS FCST MOVE INTO NERN CO
WHICH WILL DROP TEMPS BACK INTO THE 40S. CURRENT CROSS-SECTIONS
DO NOT SHOW MUCH MOISTURE WITH THE FNT SO WILL NOT MENTION ANY
PCPN. IN THE MTNS THE FLOW ALOFT WILL BE SWLY WITH ONLY SOME MID
AND HIGH LEVEL CLOUDS EXPECTED AND NO PCPN. ON MON SWLY FLOW ALOFT
WILL BE OVER THE AREA WITH NO PCPN EXPECTED. WILL KEEP HIGHS NEAR
SEASONAL LEVELS.

&&

.AVIATION...(FOR THE TAFS THROUGH 12Z WEDNESDAY MORNING)
ISSUED AT 407 AM MST TUE NOV 25 2014

MAIN CONCERN TODAY SURROUNDS WINDS. CHINOOK TYPE SETUP WILL FAVOR
KBJC WITH STRONG WINDS THROUGH THIS EVENING WITH POTENTIAL OF 50
PLUS KT GUSTS MAINLY 15Z-00Z. HOWEVER...EVEN AT KDEN AND
KAPA THE SLIGHTLY ENHANCED SOUTHWEST FLOW THIS MORNING MAY BECOME
QUITE GUSTY WITH POTENTIAL OF A FEW 35 KNOT PLUS WESTERLY
CROSSWINDS IF MOUNTAIN WAVES BREAK THROUGH. MAIN THREAT OF THOSE
STRONGER CROSSWINDS WOULD BE 16Z-00Z.

LATER TONIGHT...A COLD FRONT SHOULD BACK ACROSS THE FRONT RANGE
AIRPORTS BY 06Z WITH A BRIEF 1-3 HOUR WINDOW OF LOW LEVEL WIND
SHEAR GIVEN SHALLOW NATURE OF FRONT. CHANCE OF GENERALLY LIGHT
SNOW SHOWERS AND MVFR CEILINGS DEVELOPING BEHIND THE FRONT.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
HIGH WIND WARNING UNTIL 5 AM MST WEDNESDAY FOR COZ035-036-038-
039.

WINTER WEATHER ADVISORY FROM 11 AM THIS MORNING TO 5 AM MST
WEDNESDAY FOR COZ031-033-034.

&&

$$

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



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