Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 301822
AFDBOU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DENVER/BOULDER CO
1122 AM MST FRI JAN 30 2015

.UPDATE...
ISSUED AT 1118 AM MST FRI JAN 30 2015

CLOUDS ARE THICKENING ACROSS THE PLAINS AND WILL PUT A DAMPER ON
WARMING THIS AFTERNOON...BUT THIS IS ALREADY ANTICIPATED AND
FORECAST TEMPERATURES LOOK ALRIGHT. SOME LIGHT SNOW JUST CREEPING
UP INTO THE CENTRAL MOUNTAINS...OTHERWISE FAIRLY HIGH CLOUD BASES.
I MADE SOME MINOR ADJUSTMENTS TO POPS FOR THIS AFTERNOON/EVENING
FOCUSING MORE ON THE SOUTHERN FRINGE OF OUR AREA WITH SLOWER
DEVELOPMENT IN THE NORTHERN MOUNTAINS THIS AFTERNOON. NO CHANGES
FOR LATER TONIGHT...DENVER AREA PROBABLY ON THE EDGE OF THE SNOW.

&&

.SHORT TERM...(TODAY THROUGH TONIGHT )
ISSUED AT 240 AM MST FRI JAN 30 2015

AN UPPER LEVEL LOW WILL REMAIN OVER THE SWRN US WITH SWLY FLOW
ALOFT. CONSIDERABLE MID LVL MOISTURE WILL ADVECT OVER THE AREA
THRU TONIGHT WITH SOME WK MID LVL ASCENT. HOWEVER OROGRAPHICS ARE
WK AT BEST AND LAPSE RATES ARE FAIRLY STABLE SO ANY SNOWFALL WILL
REMAIN ON THE LIGHT SIDE. AT LOWER ELEVATIONS MID AND HIGH LVL
CLOUD COVER WILL REMAIN IN PLACE AS A WK FNT MOVES INTO NERN CO BY
LATE AFTN. AT THIS TIME IT LOOKS LIKE IT WILL REMAIN DRY THRU THE
AFTN HOURS EXCEPT FOR A SLIGHT CHC OF SHOWERS IN THE FOOTHILLS.
WITH THICKER CLOUD COVER OVER NERN CO HIGHS MAY STAY IN THE MID TO
UPPER IN MOST AREAS.

FOR TONIGHT THERE ARE SOME DIFFERENCES BETWEEN THE NAM AND GFS WITH
REGARDS TO PCPN POTENTIAL IN AND NR THE FOOTHILLS.  ALTHOUGH THERE
IS SOME WK MID LVL ASCENT AND A DEFORMATION ZN...LAPSE RATES ARE
RATHER STABLE WITH ONLY WK UPSLOPE AT BEST.  MEANWHILE THE GFS SHOWS
AN AREA OF DRY AIR IN THE LOWER LVLS WHICH WOULD LIMIT PCPN
POTENTIAL OVERNIGHT WHILE AT THE SAME TIME THE NAM HAS IT SATURATED
UP TO 500 MB IN THE 06Z-12Z TIME PERIOD.  INHERITED HIGH POPS FOR
TONIGHT FM DENVER SOUTH TO THE PALMER AND IN THE SRN FOOTHILLS...
HOWEVER CONFIDENCE IS NOT OVERLY HIGH AT THIS POINT.  FOR NOW WILL
NOT YO-YO THE FCST AND KEEP THE HIGHEST POPS MAINLY ALONG AND NR THE
FOOTHILLS AND OVER THE PALMER.  SNOW ACCUMULATIONS WILL BE ON THE
LIGHT SIDE WITH UP TO A FEW INCHES IN THE FOOTHILLS AND AN INCH
OR LESS OVER DENVER.

.LONG TERM...(SATURDAY THROUGH THURSDAY)
ISSUED AT 310 AM MST FRI JAN 30 2015

DEEP MOISTURE PLUME WILL REMAIN ACROSS THE FORECAST AREA THROUGH
SATURDAY...BUT HOW MUCH OF THAT TRANSLATES INTO SNOWFALL IS STILL
IN QUESTION. THERE IS VERY LITTLE IN THE WAY OF OROGRAPHIC FORCING
DURING THE DAY...WITH ONLY FOCUSING MECHANISM EVIDENT BEING WEAK
MID LEVEL FRONTOGENESIS AND UPPER LEVEL DEFORMATION ZONE. THIS
SHOULD BE ENOUGH TO KEEP AT LEAST AN AREA OF LIGHT SNOW GOING
THROUGH THE DAY...BUT HARD TO SAY EXACTLY WHERE GIVEN THE
MULTITUDE OF MODEL SOLUTIONS. WHILE GFS...CANADIAN...ECMWF...AND
EVEN LATEST NAM ARE PRETTY DRY ACROSS THE PLAINS...THE PRESENCE OF
WEAK FORCING IN A MOIST ENVIRONMENT STILL GIVES PLENTY OF DOUBT
TO THE RESULTING WEATHER FORECAST. AT THIS POINT...SEE LITTLE
REASON TO SIGNIFICANTLY CHANGE THE FORECAST WITH THE ONGOING CHANCE
OF LIGHT SNOW IN THE FORECAST. EVEN IF WE SEE A FEW BANDS...IT
WILL BE HARD TO ACCUMULATE ANY SNOW ON THE PLAINS SATURDAY WITH
TEMPS RUNNING IN THE 35 TO 40 DEGREE RANGE MOST OF THE DAY.

BY SATURDAY NIGHT...MODELS HAVE BECOME MORE CONSISTENT SHOWING A
COLD FRONT PUSHING ACROSS THE PLAINS DURING THE EVENING. THIS
LOOKS GOOD CONSIDERING THE SHORT WAVE MOVING QUICKLY SOUTHEAST
ACROSS THE NORTHERN PLAINS STATES. THE LOW LEVELS DESTABILIZE
CONSIDERABLY WITH FRONTAL PASSAGE SO EXPECT A FEW CONVECTIVE SNOW
SHOWERS TO DEVELOP. NAM CROSS SECTIONS SHOW SOME POTENTIAL
INSTABILITY AS WELL SO WILL HAVE TO MONITOR FOR BRIEFLY HEAVIER
SNOW SHOWERS AND POSSIBLE ACCUMULATIONS. MOST OF THAT POTENTIAL
WOULD SHIFT TOWARD THE WESTERN DENVER SUBURBS...FOOTHILLS...AND
PALMER DIVIDE AREA GIVEN THE EXPECTED WIND FIELD.

A FEW OF THESE SHOWERS MAY LINGER INTO THE EARLY MORNING HOURS
SUNDAY ALTHOUGH SHOULD SEE SOME SUNSHINE RETURN DURING THE DAY
WITH AT LEAST SOME DRYING THROUGH THE COLUMN. TEMPERATURES HOWEVER
WILL BE COLDER BEHIND SATURDAY EVENINGS STRONGER COLD FRONT.

BY MONDAY...ATTENTION WILL TURN TOWARD HIGH WIND POTENTIAL WITH
40-50 KNOT CROSS MOUNTAIN FLOW AND INCREASING PRESSURE GRADIENT.
INCREASED WIND FORECAST FOR THIS TIME FRAME. THERE SHOULD ALSO BE
A GOOD CHANCE OF OROGRAPHIC SNOWFALL IN THE HIGH COUNTRY AS A
PACIFIC MOISTURE PLUME MOVES ACROSS THE CENTRAL ROCKIES.
HOWEVER...LAPSE RATES MAY BE TOO STABLE FOR A SIGNIFICANT
SNOWFALL.

THE MOUNTAINS WILL CONTINUE TO SEE A CHANCE OF SNOW CONTINUING
THROUGH MID WEEK AS FAST WEST/NORTHWEST FLOW REMAINS IN PLACE.
THIS FLOW PATTERN WOULD ALSO SUPPORT EMBEDDED SHORT WAVES AND
POTENTIAL COLD FRONTAL SURGES ACROSS THE PLAINS. AT THIS
TIME...MAIN THREAT FOR THAT WOULD BE TUESDAY NIGHT OR WEDNESDAY
WITH COLDER TEMPERATURES AND A CHANCE OF SHOWERS DEVELOPING IN THE
LOWER ELEVATIONS. CONSIDERABLE UNCERTAINTY WITH GFS ENSEMBLE AND
ECMWF DATA HERE...BUT GIVEN THE PATTERN IN PLACE WILL HAVE SOME
CHANCE OF PRECIPITATION AND COLDER TEMPERATURES FOR WEDNESDAY.
BY THURSDAY OR FRIDAY COULD SEE A RETURN TO DOWNSLOPE FLOW AND
WARMER TEMPS.

&&

.AVIATION...(FOR THE TAFS THROUGH 00Z SATURDAY LATE AFTERNOON)
ISSUED AT 1118 AM MST FRI JAN 30 2015

VFR WITH LIGHT WINDS THIS AFTERNOON. CEILINGS WILL LOWER THIS
EVENING...INSTRUMENT APPROACHES TO KDEN MAY BE NEEDED AFTER 03Z.
AREAS OF MVFR CEILINGS IN LIGHT SNOW WILL DEVELOP BY 06Z WITH
LOCALIZED IFR. CONDITIONS ARE EXPECTED TO IMPROVE SATURDAY MORNING
WITH SNOW OUT OF THE AREA AND VFR CONDITIONS BY 16Z. ANY SNOW
ACCUMULATION IS EXPECTED TO BE LESS THAN AN INCH.

&&

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

$$

UPDATE...GIMMESTAD
SHORT TERM...RPK
LONG TERM...BARJENBRUCH
AVIATION...GIMMESTAD


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