Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 221704
AFDBOU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DENVER/BOULDER CO
1004 AM MST MON DEC 22 2014

.UPDATE...
ISSUED AT 959 AM MST MON DEC 22 2014

NORTHWEST FLOW ALOFT WILL CONTINUE TO PREVAIL TODAY. COLD AIR
ADVECTION WILL LIMIT WARMING TODAY...SO DROPPED HIGH TEMPERATURES
A FEW DEGREES. WARMEST LOCATION WILL BE IN THE FORT COLLINS AND
GREELEY AREAS WHERE DOWNSLOPE FLOW OFF THE CHEYENNE RIDGE WILL
PRODUCE THE WARMEST READINGS. FOR THE MOUNTAINS...WEB CAMERAS AND
RADAR STILL SHOW SNOW FALLING IN MOST OF THE MOUNTAINS...AND UGLY
CONDITIONS AT THE HIGHER PASSES. WILL LEAVE THE HIGHLIGHTS AS IS
FOR THE MOUNTAINS.

FOR TONIGHT AND TUESDAY...CLOSED LOW WILL SINK SOUTH ACROSS THE
CENTRAL PLAINS. STILL LOOKS LIKE STRONG WINDS WILL DEVELOP
OVERNIGHT AND INTO TUESDAY. MODELS STARTING TO INCREASE THE AMOUNT
OF SNOW WITH THIS SYSTEM. JUST A COUPLE INCHES OF SNOW COMBINED
WITH THE STRONG WINDS WOULD PRODUCE HARSH DRIVING AND POSSIBLY
BLIZZARD CONDITIONS. WILL TRY AND PIN DOWN WHERE THE GREAT CHANCE
FOR SNOW WILL BE AND MAY NEED TO GO WITH SOME SORT OF WINTER
HIGHLIGHT FOR THE BLOWING SNOW OVER THE EASTERN PLAINS.

&&

.SHORT TERM...(TODAY THROUGH TONIGHT )
ISSUED AT 333 AM MST MON DEC 22 2014

NO MAJOR CHANGES PLANNED WITH THE LATEST GRIDS. STRONG NORTHWEST
FLOW ALOFT OVER THE AREA EARLY IN THE PERIOD WILL GRADUALLY VEER
AROUND TO NORTHERLY AS UPPER CYCLONE HEADS SOUTH INTO THE CENTRAL
PLAINS. SUFFICIENT MOISTURE AND INSTABILITY IN THIS FLOW FIELD TO
KEEP THE OROGRAPHIC COMPONENT OF THE SNOW GOING IN THE HIGH
COUNTRY DESPITE ANY STRONG QG ASCENT. WITH THIS IN MIND WILL
MAINTAIN THE MOUNTAIN HIGHLIGHT AS IS. THE 07Z EXPIRATION TIME
APPEARS REASONABLE WITH CONDITIONS IMPROVING THIS EVENING.

A FEW SNOW BANDS ARE PRESENT EAST OF THE MOUNTAINS AT 10Z AND
THIS SCENARIO OF OCCASIONAL SNOW BANDS WILL PROBABLY CONTINUE OFF
AND ON TODAY GIVEN THE AFOREMENTIONED FLOW PATTERN. SOME OF THE
HEAVIER ONES COULD PROVIDE A QUICK DUMP OF PRECIPITATION BUT
TEMPERATURES AT LOWER ELEVATIONS WILL LIKELY BE SUFFICIENT TO
PRECLUDE ANY SIGNIFICANT SNOW ACCUMULATIONS. THE PALMER DIVIDE
COULD BE AN EXCEPTION TO THIS. THE MODELS SUGGEST A BETTER CHANCE
OF PRECIPITATION OVER THE NORTHEAST CORNER TONIGHT AS A BLOB OF QG
ASCENT WORKS ITS WAY AROUND THE WESTERN PERIPHERY OF THE PLAINS
CYCLONE. WITH THE EXPECTED WINDS AND THE POSSIBILITY OF SNOW OUT
THERE...CONDITIONS COULD GET A BIT DICEY FOR A TIME LATE IN THE
PERIOD. TOTAL AMOUNTS OF PRECIPITATION ARE NOT EXPECTED TO BE
GREAT SO NO HIGHLIGHT FOR THAT IS NECESSARY AT THIS TIME.

.LONG TERM...(TUESDAY THROUGH SUNDAY)
ISSUED AT 333 AM MST MON DEC 22 2014

STG NNW FLOW ALOFT WILL BE OVER THE AREA ON TUE.  MOISTURE WILL
CONTINUE TO DECREASE IN THE MTNS HOWEVER ENOUGH WILL LINGER AT MTN
TOP FOR -SHSN ESPECIALLY IN THE MORNING HOURS.  OVER NERN CO WITH
UPPER LEVEL JET OVERHEAD AND SOME MOISTURE MOVING ACROSS IN THE
MORNING HOURS THERE WILL BE A CHC OF LIGHT SNOW OVER THE PLAINS.  IN
ADDITION BNDRY LYR WINDS AROUND 50 KTS WILL LIKELY MIX DOWN TO
THE SFC WITH POTENTIAL FOR HIGH WINDS THRU EARLY AFTN SO WILL
ISSUE A WATCH FM THE WY-NE BORDER SOUTH TOWARDS LIMON. AS FOR
HIGHS WILL KEEP READINGS IN THE 35 TO 40 DEGREE RANGE OVER NERN
CO.

ON WED THE FLOW ALOFT WILL BECOME MORE WNW WITH ONLY SOME HIGHER LVL
MOISTURE MOVING ACROSS.  MEANWHILE SFC LEE TROUGH WILL DVLP ALONG
THE FRONT RANGE WITH DOWNSLOPE FLOW INCREASING BY AFTN.  THUS WILL
SEE WARMER TEMPS WITH HIGHS RANGING IN THE LOWER 50S AROUND DENVER
TO THE LOWER TO MID 40S OVER THE FAR NERN PLAINS.

FOR WED NIGHT INTO CHRISTMAS MORNING THE FLOW ALOFT WILL BECOME MORE
WLY. THERE COULD BE SOME POTENTIAL FOR HIGH WINDS IN THE FOOTHILLS
DEPENDING ON STRENGTH OF MTN WAVE AS COMPONENT ALONG WINDS INCREASE
TO 60 KTS.  BY THU AFTN THE FLOW ALOFT WILL BECOME MORE SWLY AS AN
UPPER LEVEL TROUGH MOVES SE INTO THE GREAT BASIN. MOISTURE WILL
BEGIN TO INCREASE IN THE MTNS WITH A CHC OF -SHSN BY AFTN. OVER
NERN CO IT LOOKS GENERALLY DRY AND MILD FOR THU AFTN WITH HIGHS IN
THE 45 TO 50 DEGREE RANGE. BY LATE AFTN AS MID LVL QG ASCENT
INCREASES THERE COULD BE A SLIGHT CHC OF RAIN SHOWERS OVER NERN
CO.

FOR THU NIGHT INTO EARLY FRI THERE IS NOT MUCH AGREEMENT BETWEEN THE
ECMWF AND GFS.  THE ECMWF HAS THE MAIN UPPER LEVEL TROUGH MOVING
ACROSS THU NIGHT WITH A GOOD SHOT OF MID LVL QG ASCENT AS A CDFNT
MOVES INTO NERN CO EARLY THU EVENING WITH INCREASING UPSLOPE FLOW AS
A SFC LOW INTENSIFIES OVER SERN CO. AS A RESULT THIS LEADS TO A GOOD
CHC OF SNOW FM THE MTNS ACROSS THE PLAINS.  MEANWHILE THE GFS KEEPS
THE MAIN SFC LOW OVER NERN CO WITH A BORA TYPE FNT MOVING ACROSS
LATE THU NIGHT INTO FRI MORNING WHICH KEEPS MOST OF THE PCPN IN THE
MTNS AND OVER THE FAR NERN PLAINS.  AT THIS TIME ITS STILL NOT CLEAR
HOW THINGS WILL EVOLVE THU NIGHT INTO EARLY FRIDAY.  FOR NOW WILL
KEEP 20 TO 30 PERCENT POPS OVER NERN CO FOR THU NIGHT.

FOR FRI INTO FRI NIGHT NWLY FLOW ALOFT WILL BE OVER THE AREA WITH
SOME MOISTURE IN THE MTNS WHICH WILL LEAD TO A CHC OF OROGRAPHIC
SNOW. OVER NERN CO WILL KEEP FCST DRY FOR NOW WITH HIGHS DROPPING
BACK INTO THE UPPER 20S TO LOWER 30S.

BY THE WEEKEND THE ECMWF AND GFS SHOW WEAK UPPER LEVEL RIDGING ON
SAT WITH ONLY A SLIGHT CHC OF -SHSN IN THE MTNS WITH DRY CONDITIONS
ELSEWHERE.  HIGHS WILL GENERALLY BE IN THE 30S ACROSS NERN CO.  BY
SUN THE GFS MOVES ANOTHER UPPER LEVEL TROUGH ACROSS THE AREA ALONG
WITH A CDFNT.  THIS WOULD LEAD TO ANOTHER GOOD CHC OF SNOW IN THE
MTNS WITH AT LEAST A SLIGHT CHC OF SNOW OVER NERN CO AS HIGHS STAY
IN THE 30S. MEANWHILE THE ECMWF DEVELOPS A DEEPER UPPER LEVEL TROUGH
OVER THE WRN US WHICH KEEPS THE FLOW SWLY ON SUNDAY.  THIS WOULD
LEAD TO A LOWER CHC OF SNOW IN THE MTNS WITH NO PCPN OVER NERN CO
ALTHOUGH HIGHS WOULD STILL STAY IN THE 30S.

&&

.AVIATION...(FOR THE TAFS THROUGH 18Z TUESDAY MORNING)
ISSUED AT 959 AM MST MON DEC 22 2014

SCATTERED RAIN AND SNOW SHOWERS WILL BE POSSIBLE THROUGH THIS
EVENING IN THE DENVER AREA. THESE WILL BE SHORT LIVED AND MAY DROP
CEILINGS TO 4000 FEET FOR A SHORT TIME. WIND FORECAST WILL BE
CHALLENGING FOR TODAY. EXPECT WINDS TO SWITCH TO THE NORTHWEST TO
NORTH BY 18Z. WINDS MAY ANTICYCLONE BETWEEN 19Z AND 02Z...WHICH
COULD PRODUCE A WIND DIRECTION FROM NORTHEAST TO SOUTHEAST. FOR THE
TAFS...WILL KEEP A NORTHERLY COMPONENT THOUGH CERTAINTY IS LOWER
THAN NORMAL.

FOR TONIGHT...BEST CHANCE FOR SNOW WILL BE OVER THE EASTERN PLAINS.
LIGHT SNOW MAY CLIP KDEN AND KAPA. WINDS WILL BE GUSTY AFTER 06Z
WITH GUSTS TO 40 KNOTS POSSIBLE AT KDEN.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
HIGH WIND WATCH FROM LATE TONIGHT THROUGH TUESDAY AFTERNOON FOR
COZ038-041>051.

WINTER STORM WARNING UNTIL MIDNIGHT MST TONIGHT FOR COZ031>034.

WINTER WEATHER ADVISORY UNTIL MIDNIGHT MST TONIGHT FOR COZ030.

&&

$$

UPDATE...MEIER
SHORT TERM...ET
LONG TERM...RPK
AVIATION...MEIER



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