Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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875
FXUS65 KBOU 281004
AFDBOU

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

.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 12Z TAFS THROUGH 12Z FRIDAY MORNING)
ISSUED AT 404 AM MDT THU APR 28 2016

WIDESPREAD STRATUS DECK ACROSS THE FRONT RANGE WITH STILL SOME
VERY LIGHT SNOW/FLURRIES MAINLY AROUND APA AND POINTS SOUTH.
FLURRIES WILL BE ENDING CLOSE TO DAYBREAK. EXPECT INCREASING
SHOWER ACTIVITY LATER THIS MORNING AND CONTINUE THROUGH THIS
AFTERNOON WITH LOWER CEILINGS. THE MORE WIDESPREAD RAIN WILL
DEVELOP THIS EVENING AND OVERNIGHT WHILE TEMPS WILL BE COLD ENOUGH
TO TURN MOST OF THE RAIN TO SNOW BY LATE EVENING OR CLOSE TO
MIDNIGHT. EXPECT SOME LIGHT SNOW ACCUMULATIONS OF 1-3 INCHES BY
FRIDAY AM BUT RUNWAY SURFACES MAINLY WET/SLUSHY.

&&

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

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

&&

$$

SHORT TERM...ENTREKIN
LONG TERM...COOPER
AVIATION...ENTREKIN



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