Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 130935
AFDBOU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DENVER/BOULDER CO
335 AM MDT SUN APR 13 2014

.SHORT TERM...SOME MINOR CHANGES THIS MORNING BUT THE BIG PICTURE
LOOKS PRETTY GOOD. WEAK CIRCULATION OVER LINCOLN COUNTY HAS
ORGANIZED A SHOWER BAND FROM NEAR COLORADO SPRINGS TO JULESBURG
AND WE CONTINUE TO SEE A FEW THUNDERSTORMS EMBEDDED IN THIS BAND.
THE CONVERGENCE ALONG THIS LINE SHOULD MOVE EAST OF OUR AREA EARLY
THIS MORNING. FURTHER WEST MOISTENING CONTINUES AND WE ARE
STARTING TO SEE SHOWERS FILLING IN BETWEEN THE PLAINS BAND AND THE
LARGE PRECIP BAND ASSOCIATED WITH THE UPSTREAM TROUGH. THIS MAIN
AREA OF PRECIPITATION APPEARS TO BE MOVING ON SCHEDULE OR MAYBE
EVEN A LITTLE SLOWER THAN ANTICIPATED...HOWEVER LIGHTER
PRECIPITATION WILL LIKELY DEVELOP AHEAD OF IT OVER THE NEXT FEW
HOURS. MEANWHILE THE COOLING APPEARS TO BE COMING FASTER THAN IN
YESTERDAY AFTERNOONS FORECAST. SNOW LEVEL ALREADY DOWN BETWEEN 6
AND 7 THOUSAND FEET. MOS GUIDANCE LOOKED PRETTY GOOD WITH WHAT IS
GOING ON...WE MAY STAY RAIN AROUND DENVER UNTIL THE MAIN
PRECIPITATION ARRIVES AROUND MID MORNING...BUT THE CHANGEOVER MAY
OCCUR SOONER THAN THAT. WENT WITH A COMPROMISE BETWEEN THE SIMILAR
MOST TEMPERATURE TRENDS WHICH WOULD SUGGEST ALL SNOW ACROSS THE
PLAINS BY 9 AM WITH THE EXCEPTION OF THE EASTERN FRINGE.

NOT MUCH CHANGE TO THE QPF FORECAST EXCEPT TO ADD ANOTHER INCH OR
TWO OF SNOW FOR THE EARLIER CHANGEOVER THIS MORNING. SREF PACKAGE
SHOWS MEANS RANGING FROM 5 INCHES IN GREELEY TO 8 IN BOULDER...AND
A 25 PERCENT CHANCE OF A 10-12 INCH SNOW. MELTING THIS MORNING
WILL PROBABLY SUBTRACT A COUPLE INCHES...AND ROAD IMPACT MAY
CONTINUE TO BE LIMITED BY WARM SURFACES AT LEAST THROUGH THE DAY.

DECIDED TO GO AHEAD AND ADD THE ZONES FROM GREELEY TO LIMON INTO
THE ADVISORY AREA WITH THE POTENTIAL FOR A PERIOD OF HEAVY SNOW
TODAY AND THE WINDS COMING UP ENOUGH FOR SOME DRIFTING SNOW.
THE TIMING ALSO MEANS THAT THINGS COULD BE WORSE AROUND LIMON
WHERE MORE OF THE SNOW WILL BE AT COLDER TEMPERATURES THIS
EVENING.

.LONG TERM...THE UPPER LEVEL TROUGH WILL MOVE SE OF THE AREA ON MON WITH
DRIER AIR SPREADING ACROSS IN NW FLOW ALOFT. DESPITE PLENTY OF
SUN DURING THE DAY RATHER COLD TEMPS IN THE 700-850 MB LYR WILL
KEEP AFTN HIGHS IN THE 40S OVER MOST OF NERN CO. FOR MON NIGHT
INTO TUE THE FLOW ALOFT WILL BE WNW WITH ONLY SOME HIGHER LVL
MOISTURE MOVING ACROSS WHICH WILL PRODUCE CLOUDS BUT NO PCPN.
WINDS MAY INCREASE IN THE MTNS AND FOOTHILLS MON NIGHT INTO TUE
MORNING HOWEVER CROSS COMPONENT WINDS ARE ONLY IN THE 30-40 KT
RANGE SO WINDS SHOULD STAY BLO WARNING CRITERIA. AS FOR AFTN HIGHS
850-700 MB READINGS WILL RISE FM 10-12C WHICH SHOULD ALLOW FOR
TEMPS IN THE LOWER TO MID 60S OVER NERN CO.

FOR WED INTO WED NIGHT ANOTHER UPPER LEVEL TROUGH WILL MOVE ACROSS
THE AREA.  THE GFS AND GEM ARE STRONGER WITH THIS FEATURE VS THE
ECMWF WHICH IS WEAKER.  THE GFS SHOWS DECENT MID LVL QG ASCENT
AFFECTING NRN CO FM WED INTO WED NIGHT WHILE THE ECMWF IS SOMEWHAT
WEAKER.  MEANWHILE THE GFS HAS A STG CDFNT MOVING INTO NERN CO ON
WED WITH UPSLOPE FLOW THROUGH WED NIGHT WHILE THE ECMWF HAS A WEAKER
FNT AND LESS UPSLOPE.  DESPITE THEIR DIFFERENCES BOTH MODELS END UP
PRODUCING A GOOD CHC OF PCPN WED AFTN INTO NIGHT ALTHOUGH THE GFS
SOLUTION WOULD LEAD TO HEAVIER AMOUNTS WITH THE POTENTIAL FOR
SIGNIFICAT SNOW AGAIN IN THE MTNS AND FOOTHILLS.  IN ADDITION IF THE
COLDER GFS SOLUTION PANS OUT THEN PCPN AT LOWER ELEVATIONS WOULD
FALL MOSTLY AS SNOW.  SINCE THIS SYSTEM IS STILL 4 DAYS OUT WILL
INCREASE POPS SLIGHTLY FOR WED INTO WED NIGHT BUT KEEP PCPN MOSTLY
AS RAIN THRU WED AFTN ACROSS NERN CO.

BY THU THE UPPER LEVEL SHOULD MOVE EAST OF THE AREA ALTHOUGH
DEPENDING ON THE TIMING THERE STILL COULD BE SOME LINGERING SNOW IN
THE MORNING HOURS OVER THE HIGHER TERRAIN AND PORTIONS OF THE
PLAINS.  ONCE AGAIN THERE ARE SIGNIFICANT DIFFERENCES IN TEMPS
BETWEEN THE ECMWF AND GFS AS THE GFS HAS HIGHS IN THE 40S OVER NERN
CO WHILE THE ECMWF RISES THEM INTO THE 50S.  FOR NOW WILL KEEP HIGHS
MAINLY IN THE 40S.  FOR FRI A FLAT UPPER LEVEL RIDGE WILL BE OVER
THE AREA WITH DRY CONDITIONS AND WARMER TEMPS AS HIGHS OVER NERN CO
SHOULD RISE BACK TO NORMAL LEVELS.


&&

.AVIATION...MVFR CONDITIONS IN SNOW SHOULD BECOME WIDESPREAD IN
THE DENVER AREA BY 14Z WITH AREAS OF IFR. FROM 18Z TO 04Z IFR/LIFR
CONDITIONS WILL PREVAIL. CEILINGS OF 2 HUNDRED FEET WITH
VISIBILITIES OF 1/2 MILE OR LOWER ARE LIKELY AT TIMES. CONDITIONS
ARE EXPECTED TO IMPROVE SIGNIFICANTLY BETWEEN 04Z AND 08Z THOUGH
HIGHER CEILINGS WILL STILL REQUIRE INSTRUMENT APPROACHES TO KDEN.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WARNING FROM 6 AM THIS MORNING TO MIDNIGHT MDT
TONIGHT FOR COZ035-036-041.

WINTER STORM WARNING UNTIL MIDNIGHT MDT TONIGHT FOR COZ031-033-
034.

WINTER WEATHER ADVISORY FROM 6 AM THIS MORNING TO MIDNIGHT MDT
TONIGHT FOR COZ030-032-037>040-043-045.

WINTER WEATHER ADVISORY FROM 9 AM THIS MORNING TO MIDNIGHT MDT
TONIGHT FOR COZ046-047.

&&

$$

SHORT TERM...GIMMESTAD
LONG TERM....RPK
AVIATION...GIMMESTAD


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