Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 281608
AFDBOU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DENVER/BOULDER CO
1008 AM MDT THU APR 28 2016

.UPDATE...
ISSUED AT 1005 AM MDT THU APR 28 2016

SNOW BAND PASSING OVER SRN/CNTRL PORTIONS OF THE CWA ATTM WAS
QUICKLY LIFTING NORTH ACCORDING TO RADAR AND SFC OBS. ALREADY
SEEING SRN EDGE OF THIS LIGHT TO MODERATE PRECIP REACHING SRN
DOUGLAS AND SWRN ELBERT COUNTIES. AT ITS PRESENT FORWARD
SPEED...SHOULD SEE FIRST WAVE OF PRECIP ON THE PLAINS MOVING OUT
OF THE DENVER METRO AREA IN THE NEXT 2 HOURS OR SO...AND
EVENTUALLY THROUGH THE NRN TIER OF THE CWA BY EARLY AFTERNOON.
AS NOTED IN EARLIER FCST DISCUSSION...SHOULD SEE A DROP OFF IN
PRECIP ON THE PLAINS MID TO LATE AFTERNOON AND MESOSCALE MODELS
ARE INDICATING...AND THEN A QUICK REGENERATION IN PRECIP INITIALLY
ALONGTHE FRONT RANGE FOOTHILLS AND PALMER DIVIDE EARLY THIS
EVENING. SNOW AT THE MOMENT IS EXPECTED TO CHANGE OVER TO A MIX OF
RAIN AND SNOW OR ALL SNOW ON THE PLAINS THIS AFTERNOON WITH
WARMING TEMPS. AS FOR THE HIGH COUNTRY....SHOWERY PRECIP EXPECTED
THROUGH THE DAY WITH RAIN AND SNOW IN THE MTN VALLEYS AND SNOW AT
HIGHER ELEVATIONS. IT MAY BECOME A MIX OF SNOW/RAIN AT ELEVATIONS
BELOW 9500 FT WITH WARM AIR ADVECTION  AHEAD OF THE UPPER TROUGH.
NOTE ADJUSTMENTS TO NEARLY ALL FCST FIELDS DURING 1ST PERIOD.



&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 400 AM MDT THU APR 28 2016

WATER VAPOR IMAGERY SHOWING THE BROAD UPPER LOW ACROSS SOUTHERN
CALIFORNIA AND WEST CENTRAL ARIZONA THIS MORNING. AHEAD OF THE
MAIN LOW... THERE IS AN INITIAL PIECE OF ENERGY THAT HAS MOVED
INTO WESTERN COLORADO WITH INCREASING MOISTURE AND SHOWERS.
EXPECT A GRADUAL INCREASE IN SHOWER ACTIVITY BY LATER THIS
MORNING AS MOST OF THE SHORT RANGE MODELS SHOWING SHOWERS
INCREASING IN THE 15Z- 18Z TIME RANGE OVER THE FRONT RANGE
FOOTHILLS AND URBAN CORRIDOR. TEMPERATURES WILL WARM ENOUGH THAT
MUCH OF THE PRECIP WILL BE IN THE FORM OF RAIN ON THE PLAINS AND A
MIX OF RAIN AND SNOW IN THE FOOTHILLS.

THE MAIN UPPER LOW WILL MOVE TO NEAR THE 4 CORNERS REGION BY THIS
EVENING WITH MODERATE QG ASCENT AHEAD OF THE LOW AND DEEPENING
UPSLOPE FLOW. PRECIP WILL BECOME WIDESPREAD OVER THE ENTIRE AREA
OVERNIGHT WHILE SHOULD SEE ENOUGH COLD AIR TO SEE RAIN MIXING AND
CHANGING TO SNOW BY MIDNIGHT OVER THE URBAN CORRIDOR AND OVERNIGHT
ACROSS THE PLAINS. THERE ARE SOME DIFFERENCES IN THE TEMPERATURE
STRUCTURE OF THE MODELS AS THE NAM IS SHOWING A SLIGHTLY COLDER
AIRMASS THAN THE GFS.

WILL UPGRADE THE CURRENT WINTER STORM WATCHES TO WINTER STORM
WARNINGS FOR THE MOUNTAINS AND FOOTHILLS WHILE ADDING A WINTER
STORM WATCH TO ZONE 41 ACROSS THE PALMER DIVIDE. STILL ENOUGH
UNCERTAINTY ON HOW MUCH SNOW WILL ACTUALLY FALL OVER THE PALMER
DIVIDE GIVEN THE COLDER TEMPERATURES AND HIGHER ELEVATIONS. STILL
ENOUGH POTENTIAL TO HAVE A WATCH THERE.

.LONG TERM...(FRIDAY THROUGH WEDNESDAY)
ISSUED AT 313 AM MDT THU APR 28 2016

THE MDLS REMAIN CONSISTENT IN THE TIMING AND TRACK OF THE NEXT
STORM SYSTEM THROUGH SATURDAY. IT IS STILL PROGGED TO BE NEAR THE
FOUR CORNERS REGION FRIDAY MORNING THEN IS EXPECTED TO MOVE ACROSS
THE STATE THROUGH FRIDAY NIGHT AND INTO SOUTH CENTRAL NEBRASKA BY
SATURDAY. THE MDLS SHOW MODERATE QG ASCENT THROUGH FRIDAY EVENING
THEN IT WEAKENS AS THE SYSTEM SHIFTS FURTHER EAST. NAM12 FORECAST
SOUNDINGS AND SPATIAL CROSS SECTIONS SHOW MOIST ADIABATIC LAPSE
RATES WITH A FAIRLY DEEP ESELY UPSLOPE COMPONENT THROUGH THE DAY
ON FRIDAY. AS THE TROUGH SHIFTS TO THE EAST FRIDAY NIGHT INTO
SATURDAY THE FLOW ALOFT TRANSITIONS TO NWLY. OVERALL QPF FOR MOST
OF THE MDLS IS AROUND 1-1.5 INCHES WITH THE GFS THE OUTLIER WITH
TWICE THOSE AMOUNT. WILL SIDE WITH THE CONSENSUS VS THE GFS AS IT
STILL SHOWS SNOWFALL OF 20-30 INCHES ACROSS THE NORTHEAST
PLAINS...WHICH SEEMS TOO HIGH FOR THIS TIME OF YEAR EVEN IF IT
WERE TO GET COLD ENOUGH.  THE AIRMASS DOES APPEAR COLD ENOUGH FOR
SNOW WITH THE BEST WINDOW FOR ACCUMULATING SNOWFALL FRIDAY MORNING
AND FRIDAY EVENING...WHEN TEMPERATURES ARE AROUND FREEZING. DO NOT
EXPECT THE SNOWFALL TO ACCUMULATE AS MUCH IN THE AFTERNOON AS
TEMPERATURES CLIMB INTO THE MID 30S. NO HIGHLIGHTS FOR THE URBAN
CORRIDOR AT THIS TIME...BUT A WINTER WEATHER ADVISORY MAY BE
NECESSARY FOR FRIDAY/FRIDAY NIGHT. STILL LOTS OF QUESTIONS
REGARDING THE POSSIBLE SNOW AMOUNTS FOR THE PLAINS...BUT MIXED
PCPN WOULD LOWER SNOWFALL NUMBERS SIGNIFICANTLY. OVER THE
WEEKEND...STILL UNSETTLED WITH COLORADO CAUGHT BETWEEN THE EXITING
TROUGH OVER NEBRASKA WITH ANOTHER TROUGH MOVING INTO NORTHWEST
ARIZONA. WEAK DEFORMATION AREA OVER COLORADO SATURDAY NIGHT INTO
SUNDAY...WITH AT LEAST THE NAM12 SHOWING FAVORABLE NELY UPSLOPE IN
THE LOWER LEVELS. AS A RESULT THE POTENTIAL FOR SOME LIGHT SNOW
POSSIBLE IN AND NEAR THE FOOTHILLS/PALMER DIVIDE SATURDAY
NIGHT/SUNDAY MORNING. THE NEXT SYSTEM IS PROGGED TO LIFT FOR NORTH
THAN EAST SUNDAY INTO MONDAY BUT A MOIST SOUTHWESTERLY FLOW MAY
STILL BRING SOME LIGHT SNOW TO THE REGION INTO EARLY NEXT WEEK.
SHOULD SEE SOME IMPROVEMENT TUESDAY INTO WEDNESDAY AS A RIDGE
BUILDS OVER THE ROCKY MOUNTAIN REGION...WITH DRIER AND WARMER
WEATHER BY THE MIDDLE OF NEXT WEEK.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z FRIDAY AFTERNOON)
ISSUED AT 1005 AM MDT THU APR 28 2016

LIGHT TO MODERATE SNOW BAND ASSOCIATED WITH A SHORTWAVE TROUGH
LIFTING NORTH ACRS THE METRO AREA AT PRESENT TIME...SHOULD SHIFT
NORTH OF THE METRO AREA BY AROUND MIDDAY. UNTIL THEN SNOW AND FOG
WILL PRODUCE ILS CIGS AND VSBYS AT DENVER AREA AIRPORTS. POSSIBLE
AIRPORTS COULD PICK UP A QUICK INCH OF SLUSHY SNOW...MAINLY ON
GRASSY SURFACES. AFTER 18Z...SHOULD SEE IMPROVING CIGS AND VSBYS
WITH PARTIAL CLEARING IN THE WAKE OF THE DISTURBANCE. PRECIP MAY
SWITCH BACK TO RAIN OR A MIX OF RAIN/SNOW IN THE AFTERNOON. DO NOT
SEE ANY ADDITIONAL SNOW ACCUMULATION IN THE AFTERNOON.

TONIGHT/S FORECAST NO CHANGE. PARENT STORM SYSTEM WILL BEGIN
IMPACTING THE METRO AREA IN THE EVENING WITH A RETURN TO ILS
CONDITIONS AT ALL AIRPORTS BY MID TO LATE EVENING WITH A MOIST
EAST-NORTHEAST UPSLOPE FLOW.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WATCH FROM 6 PM MDT THIS EVENING THROUGH FRIDAY
EVENING FOR COZ041.

WINTER STORM WARNING FROM 6 PM THIS EVENING TO MIDNIGHT MDT
FRIDAY NIGHT FOR COZ033>037.

&&

$$

UPDATE...BAKER
SHORT TERM...ENTREKIN
LONG TERM...COOPER
AVIATION...BAKER



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