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000
FXUS65 KBOU 070322
AFDBOU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DENVER/BOULDER CO
822 PM MST THU MAR 6 2014

.UPDATE...UPPER LEVEL TROUGH OVER THE PACIFIC NORTHWEST WILL
CONTINUE TO TRACK EAST-SOUTHEAST AND MOVE OVER COLORADO TOMORROW.
SOUTHWEST FLOW AHEAD OF THE TROUGH HAS BROUGHT MID AND HIGH CLOUDS.
CLOUDS WILL LOWER TONIGHT AS THIS SYSTEM NEARS. RADAR SHOWING A FEW
LIGHT SHOWERS OVER WESTERN COLORADO. WILL KEEP POPS LOW OVER THE
MOUNTAINS THIS EVENING THEN RAMP THEM UP OVERNIGHT.

FOR FRIDAY...STILL ON TRACK FOR A COOL AND WET DAY. PRECIPITATION
TYPE WILL BE RAIN OR SNOW AND WILL DEPEND ON TEMPERATURES WHICH WILL
BE IN THE 30S. RIGHT NOW APPEARS MOST OF THE PRECIPITATION WILL FALL
AS RAIN ALONG THE FRONT RANGE BELOW 6000 FEET. THOUGH IT WILL ONLY
TAKE A DEGREE OR TWO OF EXTRA COOLING FOR THE RAIN TO CHANGE TO
SNOW. THIS MAY HAPPEN UNDER THE STRONGER SHOWERS. IF RAIN CHANGES TO
SNOW EARLY...DO NOT EXPECT MUCH IF ANY ACCUMULATION ON ROADWAYS
UNTIL SUNSET. GOOD CHANCE THE RAIN WILL CHANGE OVER TO SNOW DURING
THE EVENING HOURS AND COULD MAKE ROADS SLIPPERY FRIDAY EVENING. NO
MAJOR CHANGES TO THE FORECAST...JUST INCREASED POPS MORE FOR FRIDAY.

&&

.AVIATION...LIGHT SOUTHERLY TO VARIABLE WINDS WILL LINGER THROUGH AT
LEAST 06Z...THEN TURN WEST AND EVENTUALLY NORTHERLY BY 12Z. HIGH
CLOUDS WILL LOWER THROUGH THE NIGHT AND FRIDAY MORNING. CEILINGS
WILL FALL BELOW 6000 FEET BETWEEN 12 AND 15Z. PRECIPITATION IS
EXPECTED TO BE MOSTLY RAIN THROUGH 00Z...THOUGH A DEGREE OR TWO
COOLER THAN EXPECTED WILL CAUSE THE RAIN TO CHANGE TO SNOW. THIS MAY
OCCUR FROM TIME TO TIME UNDER THE STRONGER SHOWERS. VISIBILITY MAY
FALL AS LOW AS A QUARTER MILE UNDER THE SNOW. CEILINGS WILL ARE
EXPECTED TO BE 1000 TO 2000 FEET FRIDAY...POSSIBLY FALLING TO 500
FEET.

&&

.PREV DISCUSSION... /ISSUED 400 PM MST THU MAR 6 2014/

SHORT TERM...UPPER RIDGE AXIS CURRENTLY MOVING ACROSS EASTERN
COLORADO WITH FLOW ALOFT BECOMING A BIT MORE SOUTHWEST AHEAD OF AN
APPROACHING UPPER TROUGH. THOUGH MID AND HIGH LEVEL MOISTURE HAS
BEEN ON THE INCREASE...PRECIPITATION ACROSS MOUNTAINS SLOW TO
DEVELOP. SOME LOWER CLOUDS AND PERHAPS LIGHT SNOW OVER THE HIGHER
RIDGES OF ZONE 31. CLOUDS HAVE SLOWED THE WARMING ACROSS THE
PLAINS...AND LIMITED THE WINDS NEAR THE FOOTHILLS. STILL A BIT
GUSTY ACROSS THE HIGHER RIDGES AND PORTIONS OF THE FOOTHILLS.
MOISTURE WILL CONTINUE TO INCREASE AND GRADUALLY LOWER ACROSS THE
MOUNTAINS THROUGH THE EVENING AS THE UPPER TROUGH MOVES INTO THE
GREAT BASIN. QG VERTICAL VELOCITY PROGS INDICATE INCREASING MID
LEVEL ASCENT WITH FAIRLY DECENT LAPSE RATES. THUS SHOULD SEE SNOW
DEVELOPING AND BECOMING A BIT MORE WIDESPREAD THROUGH THE EVENING.
STILL...LATEST MODELS CONTINUE SHOW ANY ACCUMULATING SNOW AFTER
03Z AND CONFINED TO ZONE 31. LOCAL SNOW MODEL STILL SHOWING ABOUT
2 TO 5 INCHES FOR ZONE 31 AND ROUGHLY 1 TO 3 INCHES ALONG ZONES 33
AND 34 BY FRIDAY MORNING. TIMING OF THE MOUNTAIN SNOW ADVISORY
LOOKS REASONABLE...THOUGH MAY BE A FEW HOURS TOO QUICK FOR ZONE
33. BUT WITH THE SLIGHTLY UNSTABLE AIRMASS AND INCREASING
LIFT...WILL KEEP THE CURRENT TIMING GOING. ACROSS THE PLAINS...DRY
CONDITIONS TO PREVAIL...THOUGH THERE MAY BE A FEW SHOWERS ALONG
THE NORTHERN BORDER AFTER MIDNIGHT WITH INCREASING LIFT. ON
FRIDAY...UPPER TROUGH EXPECTED TO MOVE ACROSS THE STATE DURING THE
AFTERNOON. MODELS SIMILAR IN SHOWING AN OPEN TROUGH AS IT MOVES
ACROSS THE STATE. INCREASING LIFT AND OROGRAPHICS COMBINED WITH
DECENT LAPSE RATES SHOULD KEEP SNOW GOING ACROSS THE NORTHERN
MOUNTAINS...AND INCREASE THE SNOW OVER ZONE 34 DURING THE MORNING.
MODELS SIMILAR IN SYSTEM TO BE FAIRLY WARM...WITH QUITE A BIT OF
PACIFIC MOISTURE. SO SNOW TO LIQUID RATIOS SHOULD BE FAIRLY LOW.
SOME ACCUMULATION EXPECTED ALONG FOOTHILLS...ESPECIALLY DURING THE
AFTERNOON OVER THE SOUTHERN FOOTHILLS WHEN THE BEST DYNAMICS AND
UPSLOPE OCCUR. WILL HOIST A WINTER WEATHER ADVISORY FOR SNOW
BEGINNING AT 18Z. ACROSS PLAINS... MODELS SHOW FRONT MOVING INTO
THE AREA DURING THE MORNING...WITH UPSLOPE DEVELOPING BY 18Z. THE
LIFT AND UPSLOPE WILL HELP GENERATE PRECIPITATION...ESPECIALLY
DURING THE AFTERNOON. AT THIS TIME...EXPECTING MAINLY A MIX OF
RAIN AND SNOW DUE TO THE FAIRLY WARM TEMPERATURES. SOME
ACCUMULATION POSSIBLE ALONG THE HIGHER TERRAIN ALONG THE PALMER
DIVIDE AS WELL AS THE CHEYENNE RIDGE.

LONG TERM...A PROGRESSIVE UPPER FLOW PATTERN IS EXPECTED TO
CONTINUE THROUGH THE FORECAST PERIOD WITH COLORADO ALTERNATING
BETWEEN PERIODS OF UPPER RIDGING AND PASSING TROUGHS EMBEDDED IN A
MEAN NORTHWESTERLY FLOW REGIME. THE FIRST TROUGH WILL BE MOVING
OUT OF THE AREA SATURDAY MORNING WITH SOME LINGERING SNOW SHOWER
ACTIVITY IN THE MOUNTAINS COMING TO AN END THROUGH THE DAY.
TEMPERATURES ON SATURDAY WILL REMAIN COOL AS WARM ADVECTION FROM
THE APPROACHING UPPER RIDGE WILL BE JUST GETTING STARTED. SUNDAY
AND MONDAY WILL SEE THE MOST WARMING WITH TEMPERATURES CLIMBING
SOME 10 TO 15 DEGREES ABOVE NORMAL. GFS MOS GUIDANCE HAS HAD A
RECENT TRACK RECORD OF BEING TOO AGGRESSIVE WITH WARMING TRENDS
LATELY...SO I FAVORED THE ECMWF MOS GUIDANCE FOR TEMPERATURES ON
SUNDAY AND MONDAY.

THE NEXT UPPER TROUGH IS FORECAST TO MOVE THROUGH ON TUESDAY AND
WEDNESDAY. IT MAY HAVE MANY SIMILARITIES TO THE SYSTEM THAT WE
WILL EXPERIENCE OVER THE NEXT 36 HOURS...BUT AT THIS TIME THE
MODELS ARE SHOWING THE TROUGH TO HAVE A LITTLE BIT COOLER THERMAL
STRUCTURE. WILL HAVE TO WATCH LATER MODEL RUNS TO GAIN A SENSE OF
THE STRENGTH OF THE SYSTEM AS IT MOVES OVER US. EACH OF THE MODELS
ARE IN AGREEMENT IN KEEPING THE FEATURE AS AN OPEN TROUGH RATHER
THAN A CLOSED LOW. BEYOND WEDNESDAY...IT LOOKS LIKE ANOTHER WARM-
UP AS WESTERN U.S. RIDGING RE-BUILDS OVER THE STATE.

AVIATION...WINDS FAIRLY LIGHT AT KDEN AND KAPA DUE TO LESS MIXING
AND CLOUD COVER. STILL FAIRLY GUSTY AT KBJC. SOUTHWEST WINDS TO
PREVAIL AT KDEN AND KAPA WHILE REMAINING WESTERLY AT KBJC THROUGH
THE EVENING...THEN SHIFT TO THE NORTHWEST AFTER MIDNIGHT AS THE
WEATHER SYSTEM APPROACHES THE AREA. MID AND HIGH LEVEL MOISTURE TO
CONTINUE TO INCREASE...WITH CEILINGS REMAINING ABOVE 12000 FEET
OVERNIGHT. AFTER 12Z...CEILINGS TO GRADUALLY LOWER AS LOW LEVEL
MOISTURE INCREASES...WITH CEILINGS AROUND 5000 FEET AGL DEVELOPING
BY 15Z. RAIN AND SNOW SHOWERS TO DEVELOP BY 18Z WITH MVFR
CONDITIONS PREVAILING AS WINDS SHIFT TO THE NORTHEAST. AT THIS
TIME...SNOW ACCUMULATIONS BY FRIDAY EVENING SHOULD BE LESS THAN AN
INCH.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY FROM 11 AM FRIDAY TO 5 AM MST SATURDAY
FOR COZ036.

WINTER WEATHER ADVISORY FROM 6 AM FRIDAY TO 5 AM MST SATURDAY
FOR COZ034.

WINTER WEATHER ADVISORY UNTIL MIDNIGHT MST FRIDAY NIGHT FOR
COZ031-033.

&&

$$

SHORT TERM...D-L
LONG TERM....DANKERS
UPDATE/AVIATION...MEIER