Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 201145
AFDBOU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DENVER/BOULDER CO
445 AM MST SAT DEC 20 2014

.SHORT TERM...(TODAY THROUGH TONIGHT )
ISSUED AT 445 AM MST SAT DEC 20 2014

MOISTURE SPREADING IN FROM THE WEST THIS MORNING. THERE WILL BE A
GAP IN THE HIGH CLOUDS OVER THE FRONT RANGE IN THE LATE AFTERNOON
OR EARLY EVENING...WHILE THE LOWER LEVEL MOISTURE UPSTREAM OF THE
MOUNTAINS SHOULD HOLD SOLIDLY. THIS APPEARS TO BE REACHING INTO
THE MOUNTAINS NEAR THE WYOMING BORDER NOW...WHILE THE INTERSTATE
70 CORRIDOR MAY BE ON THE EDGE OF IT MUCH OF THE DAY. NOT MUCH
LIFT AND NOT A LOT OF WIND TO FORCE OROGRAPHIC SNOW EITHER...BUT
THERE WILL BE AREAS OF LIGHT SNOW THAT SHOULD INCREASE WITH TIME.
MAIN CHANGE FOR TODAY WAS TO INCREASE CLOUDS A BIT OVERALL AND
INCREASE POPS IN THE MOUNTAINS...BUT FOR SMALL AMOUNTS OF SNOW.
ALSO RAISED TEMPS A BIT TONIGHT DUE TO CLOUD COVER.

.LONG TERM...(SUNDAY THROUGH FRIDAY)
ISSUED AT 445 AM MST SAT DEC 20 2014

MODELS HAVE INCREASING NORTH-NORTHWESTERLY FLOW ALOFT ON SUNDAY.
THE GFS BRINGS A BIT OF JET MAXIMUM INTO COLORADO BY LATE
AFTERNOON INTO THE EVENING SUNDAY. THE NAM AND ECMWF DO NOT. BY
MONDAY AFTERNOON AT 00Z...ALL THE MODELS HAVE A 160 KNOT NORTH-
NORTHWESTERLY JET MAXIMUM OVER THE WESTERN BORDER OF COLORADO. IT
STAYS OVER WESTERN COLORADO MONDAY NIGHT. THERE IS MOSTLY DOWNWARD
SYNOPTIC SCALE ENERGY FOR THE CWA ON THE QG VERTICAL VELOCITY
FIELDS SUNDAY THROUGH MONDAY NIGHT. THE BOUNDARY LAYER WINDS ARE
ALL WESTERLY OR SOUTHWESTERLY DOWNSLOPING ON SUNDAY AND SUNDAY
EVENING. A COLD FRONT MOVES THROUGH BETWEEN 09-12Z MONDAY
MORNING...THEN NORTHWESTERLY WINDS ARE PROGGED FOR THE CWA. THESE
NORTHWESTERLY WINDS CONTINUE MONDAY NIGHT. THERE IS NO HINT AT ANY
UPSLOPE FOR THE PLAINS. THERE WAS A TAD OF OF ON YESTERDAY`S 00Z
RUNS. FOR MOISTURE...IT IS PRETTY DEEP FOR THE MOUNTAINS ON SUNDAY
CONTINUING THROUGH MONDAY EVENING. IT DECREASES SOMEWHAT AFTER
MIDNIGHT. THE QPF FIELDS SHOW FAIR PRECIPITATION AMOUNTS OVER THE
MOUNTAINS ON SUNDAY. THEY INCREASE SUNDAY NIGHT THROUGH MONDAY
AFTERNOON. THERE IS STILL SOME INDICATED IN THE MOUNTAINS MONDAY
NIGHT. FOR THE PLAINS...THESE GRIDS SHOW SMALL AMOUNTS IN SOME
AREAS SUNDAY NIGHT THROUGH MONDAY...BEST AMOUNTS OVER THE EASTERN
PLAINS...BUT NOTHING GREAT. FOR MOUNTAIN POPS AND SNOWFALL...AFTER
THE COLD AIR ADVECTION MOVES IN LATE MONDAY MORNING INTO MONDAY
NIGHT...LAPSE RATES IN THE MOUNTAINS BECOME FAVORABLE AS DO THE 700
MB TEMPERATURES FOR GOOD SNOW PRODUCTION. THERE IS FAVORABLE WIND
SPEEDS AND DIRECTIONS FOR OROGRAPHIC ENHANCEMENT AS WELL. WILL GO
WITH "LIKELY" POPS IN THE MOUNTAINS SUNDAY...THEN "WIDESPREAD"
SUNDAY NIGHT INTO MONDAY EVENING. WILL LEAVE THE WATCH GOING FOR
NOW...BUT WITH THE DECENT COLD AIR ADVECTION ON MONDAY...SNOW
AMOUNTS COULD BE GREAT ENOUGH IN THE HIGH MOUNTAINS FOR A WARNING
SUNDAY NIGHT INTO MONDAY NIGHT. FOR THE PLAINS...WILL GO WITH
10-40%S FOR NOW SUNDAY NIGHT THROUGH MONDAY...WITH BEST CHANCES
OVER THE EAST. THERE IS NO UPSLOPE...BUT A LONGMONT ANTICYCLONE IS
POSSIBLE. FOR TEMPERATURES...SUNDAY`S HIGHS ARE 1-4 C WARMER THAN
TODAY`S. MONDAY`S HIGHS COOL OFF 6-9 C FROM SUNDAY`S. FOR THE
LATER DAYS...TUESDAY THROUGH FRIDAY...MODELS HAVE STRONG NEAR DUE
NORTHERLY FLOW ALOFT TUESDAY THROUGH MID DAY WEDNESDAY. THERE IS A
JET MAXIMUM OVER THE CWA MUCH OF THE TIME WITH 100-120 KNOT
SPEEDS. WEAK UPPER RIDGING MOVES OVER LATER WEDNESDAY INTO
WEDNESDAY EVENING. THE FLOW ALOFT WEAKENS AND IS WEST-
NORTHWESTERLY THEN. THE ECMWF AND GFS NOW DIFFER CONSIDERABLY ON
THURSDAY WITH THE ECMWF SHOWING AN UPPER TROUGH. THE GFS HAS A
VERY WEAK ONE AT BEST. THE TROUGH IS STILL SLOWLY MOVING THROUGH
ON FRIDAY ACCORDING TO THE ECMWF...THE GFS HAS WEST-NORTHWESTERLY
FLOW ALOFT. WILL GO SOME MINOR POPS OVER THE PLAINS FOR THURSDAY
WITH A COMPROMISE IN MIND AND PAST MODEL RUNS AS WELL.

&&

.AVIATION...(FOR THE TAFS THROUGH 12Z SUNDAY MORNING)
ISSUED AT 445 AM MST SAT DEC 20 2014

VFR THROUGH TONIGHT. SOME UNCERTAINTY ABOUT WIND DIRECTION THIS
AFTERNOON...WINDS SHOULD SHIFT TO SOME KIND OF EASTERLY DIRECTION
AT KDEN/KAPA...MAY STAY LIGHT WEST AT KBJC...SHIFT TO EAST OR JUST
BE VARIABLE BUT SPEEDS WILL BE LIGHT. BACK TO DRAINAGE WINDS IN
THE EVENING.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WATCH FROM SUNDAY AFTERNOON THROUGH MONDAY EVENING
FOR COZ030>034.

&&

$$

SHORT TERM...GIMMESTAD
LONG TERM...RJK
AVIATION...GIMMESTAD


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