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000
FXUS65 KBOU 071057
AFDBOU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DENVER/BOULDER CO
357 AM MST SAT DEC 7 2013

.SHORT TERM...UPPER LEVEL TROUGH IS MOVING INTO THE GREAT BASIN
EARLY THIS MORNING AND WILL PUSH EAST ACROSS COLORADO TONIGHT.
THERE IS MODERATE Q-G VERTICAL MOTION WITH THIS DISTURBANCE...AND
LIGHT SNOW WAS ALREADY DEVELOPING FROM THE HIGH COUNTRY INTO
CENTRAL UTAH IN WARM ADVECTION. THE SNOW WILL LIKELY OVERSPREAD
THE HIGH COUNTRY THROUGH THE DAY AS LIFT INCREASES...WITH SOME
SNOW SPILLING OUT ONTO THE PLAINS BY MID/LATE AFTERNOON AS THE
LIFT AND MOISTURE INCREASE. ANY SNOW ON THE PLAINS IS EXPECTED TO
BE LIGHT THROUGH TONIGHT THOUGH AS DOWNSLOPE FLOW JUST ABOVE THE
BOUNDARY LAYER WOULD BE A SIGNIFICANT LIMITING FACTOR.
ACCUMULATIONS IN THE HIGH COUNTRY WILL ALSO BE LIMITED A BIT BY
SOUTHWESTERLY FLOW TODAY. HOWEVER...COLD ADVECTION AND MORE
FAVORABLE WEST/NORTHWEST FLOW KICKS IN LATE TONIGHT. LOCAL
OROGRAPHIC SNOW MODEL SHOWS MARGINAL NUMBERS THROUGH THE EVENT
EVEN FACTORING IN 20 TO 1 SNOW/LIQUID RATIOS...BUT SYNOPTIC SCALE
LIFT SHOULD ADD ON A COUPLE INCHES. RIGHT NOW...LOOKS LIKE WE WILL
BE JUST SHY OF ADVISORY CRITERIA WITH GENERALLY 4-8 INCH TOTALS
THROUGH SUNDAY MORNING BUT WILL CONTINUE TO MONITOR. ON THE
PLAINS...ANY ACCUMULATION SHOULD BE LESS THAN AN INCH EXCEPT THE
FAR NORTHEAST CORNER WHERE A COUPLE SPOTS COULD PICK UP AN INCH OR
TWO WHERE DOWNSLOPE IS LESS PRONOUNCED AWAY FROM THE FRONT RANGE.

WITH REGARD TO TEMPERATURES...THERE IS ALREADY SOME MODERATION
NOTED AS WARM ADVECTION AND INCREASED CLOUDS HAVE REALLY BOOSTED
TEMPERATURES IN THE HIGH COUNTRY. MEANWHILE...ON THE PLAINS...
MODERATION WILL BE TEMPERED BY THE SHALLOW ARCTIC COLD POOL IN
PLACE WHICH IS IN REALLY NO HURRY TO MOVE. THE SOUTHERLY LOW LEVEL
FLOW IS INCREASING ON THE EASTERN PLAINS/PALMER DIVIDE AREA SO WE
WILL BE VERY CLOSE TO WIND CHILL ADVISORY CRITERIA THROUGH THE MID
MORNING HOURS...BUT GRADUAL MODERATION IS OCCURRING WHERE STRATUS
HAS DEVELOPED. OVERALL...RAISED FORECAST MAX TEMPS IN THE
MOUNTAINS/HIGH VALLEYS DUE TO IMPROVED MIXING ALREADY...WHILE
LOWERED THEM A COUPLE DEGREES ON THE PLAINS.

.LONG TERM...THE UPPER TROUGH THAT PRODUCES SOME LIGHT SNOW
OVER THE MOUNTAINS AND PLAINS TONIGHT WILL BE MOVING OUT OF THE
STATE SUNDAY MORNING. THIS WILL BRING AN END TO THE SNOW ON THE
PLAINS BY EARLY AFTERNOON. OROGRAPHIC SNOW SHOWERS WILL CONTINUE
IN THE MOUNTAINS AS NORTHWEST FLOW ALOFT PREVAILS. HAVE MADE FEW
CHANGES TO THE PREVIOUS FORECAST SINCE MODELS HAVE BEEN
CONSISTENT WITH THE PROGRESSION OF THE UPPER TROUGH FOR THE LAST
FEW DAYS. THE COMBINATION OF LOW SUN ANGLE AND MORNING CLOUDS FROM
THE DEPARTING WEATHER SYSTEM WILL HELP KEEP TEMPERATURES COLD
THROUGH SUNDAY AFTERNOON. THEN...CLEARING SKIES LATE IN THE DAY
AND OVERNIGHT WILL ALLOW TEMPERATURES TO DROP BELOW ZERO THROUGH
MONDAY MORNING. WARMING THROUGH THE REST OF NEXT WEEK STILL
APPEARS TO BE ON HOLD UNTIL AFTER WEDNESDAY. THE CANADIAN MODEL
AND THE ECMWF SHOW A WEAK SURGE OF COLD AIR COMING INTO THE STATE
TUESDAY NIGHT WHICH WILL KEEP WEDNESDAY TEMPERATURES BELOW THE
FREEZING MARK WHILE THE GFS DOES NOT HAVE THE COOL SURGE AND THUS
ALLOWS TEMPERATURES TO CLIMB ON WEDNESDAY. ALL MODELS SHOW
TEMPERATURES MAKING IT BACK TO SEASONAL NORMALS ON THURSDAY AND
FRIDAY.

IN THE MOUNTAINS...THE WEAK OROGRAPHIC SNOW SHOWERS WILL CONTINUE
INTO MONDAY...BUT WILL THEN TAPER OFF. THE REST OF THE WEEK WILL
BE DRY AS UPPER LEVEL RIDGING PASSES OVER THE STATE...STABILIZING
THE AIRMASS.

&&

.AVIATION...THERE IS SOME LOW LEVEL MOISTURE AND A VERY WEAK
DENVER CYCLONIC CONVERGENCE ZONE IN PLACE...SO CANT RULE OUT
DEVELOPMENT OF A STRATUS DECK AND A FEW FLURRIES THIS MORNING.
OTHERWISE VFR CONDITIONS WILL PREVAIL TIL 20Z-22Z WITH A MID
LEVEL CLOUD DECK DEVELOPING AROUND 9000 FT AGL. BEST CHANCE FOR
ANY SNOW IN THE FRONT RANGE AIRPORTS IS FROM AROUND 22Z TIL 07Z
WHEN BEST LIFT OCCURS. HIGHEST PROBABILITY IS FOR JUST A DUSTING
OF LIGHT SNOW WITH LOWER CHANCE OF 0.5 TO 1.0 INCH. SHOULD ALSO
SEE IFR/MVFR CEILINGS DEVELOP FOR THAT PERIOD AND PERSIST INTO
SUNDAY.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...BARJENBRUCH
LONG TERM....DANKERS
AVIATION...BARJENBRUCH