Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 282211
AFDBOU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DENVER/BOULDER CO
411 PM MDT THU APR 28 2016

.SHORT TERM...(THIS EVENING THROUGH FRIDAY)
ISSUED AT 410 PM MDT THU APR 28 2016

CONFIDENCE IN THE FORECAST AND DETERMINISTIC MODELS LOW TO MODERATE
AT BEST LARGELY DUE TO THE UNCERTAINTY IN GUIDANCE TEMPERATURES...
SNOW ACCUMULATION DISTRIBUTION ON THE PLAINS AND PHASE CHANGE RATES.
THAT SAID...THE LARGE UPRIGHT UPPER TROUGH WITH ITS CLOSED LOW OVER
NORTH CENTRAL ARIZONA IS STILL FORECAST TO TRACK EAST ACROSS THE 4-
CORNERS REGION OVERNIGHT WITH THE 500MB SITTING OVER SWRN COLORADO
BY 12Z/FRIDAY ACCORDING TO A MODEL CONSENSUS. QG FIELDS SHOW A
STEADY INCREASE IN LARGE SCALE ASCENT AND INSTABILITY OVER THE
FORECAST AREA WITH AN INFLUX OF DEEP LAYER MOISTURE WITH SLY
DIVERGENT FLOW ALOFT. AT LOWER ELEVATIONS UPSLOPE GRADIENT ON THE
PLAINS WILL ALSO INCREASE OVERNIGHT...BUT MODELS NEVER REALLY
SHOW STRONG UPSLOPE INTO THE FRONT RANGE. FURTHERMORE PAST COUPLE
OF MODEL RUNS CONTINUE TO BACK OFF ON QPF AND SNOW ACCUM IN THE
MTNS AND FTHLS. EARLIER RUNS INDICATED 20-35 INCH STORM TOTAL AMTS
OVER THE EAST FACE OF THE FRONT RANGE. MODELS NOW SHOW OVERALL
SNOW TOTALS BY 00Z/SATURDAY UNDER 20 INCHES.

SHOULD SEE THE PRECIP SHIELD SPREADING NWRD ACRS THE FCST AREA
DURING THE NEXT SEVERAL HOURS...FIRST OVER THE HIGH COUNTRY. PRECIP
SHOULD BE ALL SNOW ABOVE 6500 FEET THROUGH EARLY THIS EVENING AND
RAIN/DRIZZLE...OR A RAIN/SNOW MIX ON THE PLAINS. ON THE PALMER
DIVIDE PRECIP IS EXPECTED TO START OUT AS A RAIN/SNOW MIX THIS
AFTERNOON AND CHANGE OVER TO SNOW BY EARLY TO MID-EVENING.

COMING UP WITH SNOW TOTALS AND PINNING DOWN WHERE THE RAIN/SNOW LINE
ARE COMMON CHALLENGES FOR SPRINGTIME STORMS. MODEL WETBULB ZERO
HEIGHTS AT THEIR HIGHEST THIS EVENING AND THEN GRADUALLY LOWER
THROUGH TOMORROW AFTERNOON WITH NLY FLOW ON THE BACK SIDE OF THE
EXITING TROUGH. IT/S NOT INCONCEIVABLE THAT FRONT RANGE MTNS AND
FTHLS COULD SEE A SIGNIFICANT FALL OFF IN SNOWFALL TOMORROW
AFTERNOON SHOULD NWLY/DOWNSLOPE FLOW SET UP. FOR NOW WILL HOLD ONTO
THE WINTER STORM WARNING FOR THESE AREAS UNTIL 06Z/SAT. WILL
ALSO HOLD ONTO THE WINTER WEATHER ADVISORY FOR THE PALMER DIVIDE
UNTIL 06Z/SATURDAY. WHILE 6-12 INCHES OF SNOW IS PREDICTED FOR
THIS ZONES...COULD SEE HALF OF IT MELT OFF DURING THE DAY FRIDAY.
SAME GOES FOR THE PLAINS. MUCH OF THE SNOW FALLING AT LOWER
ELEVATIONS SHOULD ALSO MELT AS IT FALLS WITH TEMPERATURES IN THE
MID30S FOR MUCH OF THE DAY AND DUE TO A HIGHER SUN ANGLE THIS TIME
OF YEAR. THE DENVER METRO AREA MAY END UP WITH A WINTER WEATHER
ADVISORY...NOT ONE WILL NOT BE ISSUED AT THIS TIME.

.LONG TERM...(FRIDAY NIGHT THROUGH THURSDAY)
ISSUED AT 410 PM MDT THU APR 28 2016

UPPER LOW WILL MOVE SLOWLY EASTWARD FRIDAY NIGHT AND SATURDAY WITH
A GRADUAL DECREASE IN ITS IMPACT. WRAPAROUND PRECIPITATION COMING
BACK INTO COLORADO...MODELS VARY IN HOW FAR SOUTH PRECIPITATION
COMES...AND IT WILL BE FIGHTING MODEST LOW LEVEL NORTHERLY FLOW
COMING DOWN THE CHEYENNE RIDGE. MORE SOUTHERLY SOLUTIONS HOLD ON
TO STEADY LIGHT PRECIPITATION AS FAR SOUTH AS INTERSTATE 70 INTO
SATURDAY MORNING...WHILE MORE NORTHERLY SOLUTIONS HOLD THIS OVER
THE CHEYENNE RIDGE WITH ONLY SPOTTY PRECIP FURTHER SOUTH BY THAT
TIME. THERE IS STILL WEAK FORCING AND PLENTY OF MOISTURE
AROUND...BUT AT SOME POINT THERE WILL BE ENOUGH DRYING TO STOP THE
STEADY LIGHT RAIN/SNOW. HOWEVER...ALSO STILL SOME LOW LEVEL
INSTABILITY SO THERE SHOULD STILL BE SOME SPOTTY LIGHT SHOWERS.
LITTLE CHANGE TO THE TEMPERATURES...STILL PROBABLY COLD ENOUGH FOR
SNOW AROUND DENVER BUT WARM ENOUGH FOR LIMITED IMPACT.

FOR SATURDAY NIGHT AND SUNDAY WE ARE BETWEEN THE LOW TO OUR EAST
AND A NEW LOW MOVING ACROSS THE SOUTHWEST. INITIALLY THERE IS NOT
MUCH GOING ON BUT STILL A MOIST ENVIRONMENT WITH SOME LOW POPS
STILL IN ORDER. BY SUNDAY AFTERNOON THERE SHOULD BE SOME WEAK LIFT
MOVING IN FROM THE SOUTHWEST. IT SHOULD BE FAIRLY WEAK BUT WORKING
ON A FAVORABLE ENVIRONMENT...STILL PLENTY OF MOISTURE AROUND AND
ONLY WEAK STABILITY. BUMPED UP POPS A LITTLE BIT FOR SUNDAY-MONDAY
TIME PERIOD BUT NOT EXPECTING THIS TO BE A SIGNIFICANT
PRECIPITATION EVENT. TEMPERATURES SHOULD BE THE SAME OR PROBABLY A
LITTLE WARMER.

WARMING TREND COMES TOWARD THE END OF THE WEEK...STILL A LITTLE
MOISTURE/INSTABILITY AROUND FOR SOME LOW POPS...MAINLY LIGHT
DIURNAL SHOWERS OVER THE MOUNTAINS. MODEL BLEND FORECAST IS FINE
FOR THIS TIME.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z FRIDAY EVENING)
ISSUED AT 410 PM MDT THU APR 28 2016

ILS CIGS AND LATER THIS EVENING ILS VISIBILITIES WITH SNOWFALL
AND FOG. SNOWFALL LIGHT TO MODERATE OVERNIGHT...WITH THE HEAVIER
SNOWFALL RATES AFTER MIDNIGHT. COULD SEE 1-3 INCHES OF SNOW
ACCUMULATION MAINLY ON GRASSY SURFACES BY MORNING. ON FRIDAY...
PERIOD OF LIGHT TO MODERATE SNOW IN THE MORNING WITH N-NELY WINDS
OF 5-15 KTS...THEN LIGHTER SNOWFALL OR A MIX OF LIGHT RAIN AND
SNOW IN THE AFTERNOON WITH THIS STORM SYSTEM MOVING AWAY FROM THE
FRONT RANGE.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY UNTIL MIDNIGHT MDT FRIDAY NIGHT FOR
COZ041.

WINTER STORM WARNING UNTIL MIDNIGHT MDT FRIDAY NIGHT FOR
COZ033>037.

&&

$$

SHORT TERM...BAKER
LONG TERM...GIMMESTAD
AVIATION...BAKER


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