Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 260524
AFDBOU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DENVER/BOULDER CO
1024 PM MST WED FEB 25 2015

.UPDATE...
ISSUED AT 1020 PM MST WED FEB 25 2015

NARROW BAND OF HEAVY SNOW AND STG NLY WINDS OF 20-30KTS PRODUCING
BLOWING SNOW AND NEAR ZERO VSBYS BLOWING THROUGH SRN AND WRN
PORTIONS OF THE DENVER METRO AREA. PRECIP AND WINDS ASSOCIATED
WITH A STG ARCTIC COLD FRONT ADVANCING SWRD AT 22-25 KTS. FRONT
SHOULD MOVE SOUTH OF THE FCST AREA BY 11 PM MST. SO WILL MOST OF
THE HVY SNOW AND STG WINDS. UPDATED FCST GRIDS OUT TO 4 HRS AND
SENT OUT A REVISED FORECAST. SHOULD SEE RAPID IMPROVEMENT ABOUT
AN HOUR AFTER FRONTAL PASSAGE.


UPDATE ISSUED AT 810 PM MST WED FEB 25 2015

SNOWFALL HAS DECREASED IN INTENSITY OVER THE URBAN DENVER AREA
FOR THE MOMENT. HOWEVER...NEXT STRONGER COLD FRONT IS POISED TO
MOVE THROUGH THE DENVER AREA AROUND 9 PM WITH SPEEDS OF 20 TO 35
MPH AND SNOWFALL ENHANCEMENT. RADAR SHOWING A RATHER NARROW BAND
OF MODERATE TO HEAVY SNOWFALL NOW OVER CENTRAL PORTIONS OF WELD
AND MORGAN COUNTIES. COULD SEE A QUICK INCH OF SNOW AS THIS BAND
MOVES SOUTHWARD THROUGH THE URBAN CORRIDOR AND ADJACENT PLAINS.
EXPECT SNOW ENHANCEMENT OVER THE REST OF THE DENVER AREA AND
POINTS SOUTH OVER THE PALMER DIVIDE BETWEEN 9 PM AND 11 PM BEFORE
DECREASING AGAIN TOWARDS MIDNIGHT. WILL LEAVE CURRENT HILITES IN
PLACE THOUGH MAYBE ABLE TO DEHOIST HILITES BEFORE 6 AM.

UPDATE ISSUED AT 604 PM MST WED FEB 25 2015

DECIDED TO UPGRADE THE ADVISORY TO A WARNING FOR ZONE 39 ACROSS
BOULDER AND WESTERN JEFFERSON COUNTIES. THERE CONTINUES TO BE
ENHANCEMENT OF THE SNOWFALL RIGHT ALONG THE FOOTHILLS AND WITH
ADDITIONAL SURGE EXPECTED TO MOVE IN FROM WYOMING LATER THIS
EVENING EXPECT CONTINUED MODERATE TO HEAVY SNOW THROUGH THIS
EVENING. INCREASED SNOW AMOUNTS TO 6-12 INCHES...ESPECIALLY
HIGHEST AMOUNTS RIGHT IN BOULDER AREA. NO OTHER CHANGES FOR NOW IN
HILITES.

FURTHER EAST...THERE HAS BEEN A DECREASING IN SNOWFALL INTENSITY
DURING PAST HOUR ESPECIALLY EAST OF I-25. STILL EXPECT CONTINUED
LIGHT TO MODERATE SNOW FOR MUCH OF THIS EVENING FOR CONTINUED
ADVISORIES.

UPDATE ISSUED AT 349 PM MST WED FEB 25 2015

MODERATE TO HEAVY SNOW NOW ENCOMPASSES MOST OF THE URBAN CORRIDOR
FROM LONGMONT SOUTH THROUGH BOULDER...DENVER AND CASTLE ROCK. THE
HEAVY SNOW HAS ALSO STRETCHED FURTHER EAST ACROSS SOUTHWEST WELD
COUNTY SO HAVE ADDED A WINTER ADVISORY FOR THOSE SECTIONS AS WELL.
DOES APPEAR TO BE A BACK EDGE OF THIS HEAVY SNOW ACROSS SOUTHERN
LARIMER COUNTY WITH DECREASING INTENSITIES NOTED FURTHER NORTH.
WILL STILL HAVE TO WATCH CLOSELY IF THE HEAVIER SNOW DOES STICK
AROUND LONGER THAN EXPECTED THEN THE ADVISORIES WOULD NEED TO BE
UPGRADED TO WARNINGS.

&&

.SHORT TERM...(THIS AFTERNOON THROUGH THURSDAY)
ISSUED AT 1023 AM MST WED FEB 25 2015

A MOIST NORTHWESTERLY FLOW ALOFT WILL REMAIN OVER THE REGION
THROUGH THURSDAY. A COLD FRONT RACED INTO THE FRONT RANGE MUCH
EARLIER THAN EXPECT THE SNOW SHOWERS INCREASING IN COVERAGE AND
INTENSITY ALONG THE FRONT RANGE. AS A RESULT...WE STARTED TO THE
HIGHLIGHTS A LITTLE SOONER. THE BEST COMBINATION OF UPSLOPE/INSTBY
WILL BE THE REST OF THIS AFTN INTO EARLY EVENING...03-04Z. RUC
SOUNDINGS THIS AFTN HAD CAPES OF 200-300 J/KG. SOME ADDITIONAL
ENHANCEMENT UPSTREAM OVER WYOMING AND SOME OF THIS WILL BE MOVING
INTO NORTHEASTERN COLORADO THROUGH THIS EVENING.  WEAK MID AND
UPPER QG ASCENT IS PROGGED TO OCCUR AROUND THE SAME TIME AS THE
SYSTEM PASSES OVERHEAD. WL KEEP THE HIGHLIGHTS AS IS FOR NOW. THE
HRRR DOES NOT KEEP HEAVY SNOW AROUND VERY LONG...HIGHER AMOUNTS
MAY BE MORE LOCALIZED IN ZONES 39>41 SO WL KEEP THE WINTER WEATHER
ADVISORY THERE. AS FOR THURSDAY...SPATIAL CROSS-SECTIONS KEEP A
FAIRLY PERSISTENT LAYER OF LOW LEVEL WEAK UPSLOPE ALONG THE FRONT
RANGE SO SOME LIGHT SNOW MAY PERSIST ON AND OFF THROUGH THE DAY.
IN THE MOUNTAINS LIGHT SNOW THERE AS WELL. SINCE THE HEAVIER SNOW
IS EXPECTED TO OCCUR THROUGH THE EVENING...WL NOT EXTEND THE
HIGHLIGHTS ANY FURTHER THAN 6 AM MST THURSDAY.

.LONG TERM...(THURSDAY NIGHT THROUGH TUESDAY)
ISSUED AT 1023 AM MST WED FEB 25 2015

...VERY ACTIVE PATTERN WITH CONTINUED SNOW FOR THE LONG RANGE
FORECAST...

FOR THURSDAY NIGHT INTO FRIDAY UPPER LEVEL FLOW CONTINUES TO BE
STRONG OUT OF THE NW. UPSLOPE FLOW ALONG THE FOOTHILLS BEGINS TO
BREAK DOWN EARLY FRIDAY AS DOWNSLOPING TAKES OVER AND HELPS TO
CLEAR OUT PRECIPITATION BY FRIDAY AFTERNOON FOR AREAS CLOSER TO
THE FOOTHILLS AND URBAN CORRIDOR. THE MOUNTAINS HOWEVER WILL
MAINTAIN DECENT MOISTURE SO LIGHT SNOW WILL REMAIN POSSIBLE
THROUGH FRIDAY. WITH THE COLD AIR USHERED IN BY THE PASSING FRONT
MID WEEK HIGH TEMPERATURES ON FRIDAY WILL BE IN THE MID TEENS TO
LOWER 20S WITH LOW TEMPS OVERNIGHT IN THE SINGLE DIGITS.

THE UPPER LEVEL PATTERN CHANGES AS ANOTHER TROUGH OVER THE
NORTHWEST ON FRIDAY AFTERNOON DROPS SOUTH BRINGING FLOW MORE
WESTERLY. THIS IS ACCOMPANIED BY A DEEP SURFACE LOW PRESSURE
SYSTEM CENTERED OVER THE GREAT BASIN THAT WILL HELP TO CYCLE IN
MOISTURE FROM THE SOUTHWEST WITH ITS CONTINUED CYCLONIC FLOW
PATTERN. WITH INCREASED MOISTURE ALONG WITH LIGHT UPSLOPE WILL
MAINTAIN A SLIGHT CHANCE OF SNOW FOR THE PLAINS ON SATURDAY BUT
CHANCES WILL INCREASE INTO SUNDAY AS THE SURFACE LOW MOVES INTO
SW CO BRINGING INCREASED UPSLOPE TO THE FOOTHILLS AND PALMER
DIVIDE AREA.

FOR SUNDAY THE UPPER LEVEL JET MOVES NORTH INTO NE CO INCREASING
CHANCE FOR SOME CONVECTION OR BANDING SNOW. THIS COMBINED WITH
DECENT QG ASCENT THROUGH THE WEEKEND ALONG WITH SURFACE HIGH
PRESSURE OVER THE EASTERN PLAINS WITH AID IN THAT DEVELOPMENT AS
WELL. BY LATE SUNDAY THE UPPER LEVEL TROUGH WILL SINK INTO THE
DESERT SOUTHWEST PLACING CO IN THE DEFORMATION ZONE DOWNSTREAM OF
THE MAIN BRANCH OF CIRCULATION. THIS WILL MAINLY IMPACT THE
SOUTHERN PORTIONS OF THE STATE BUT WILL MAINTAIN LIGHT SNOW FOR
OUR REGION IN THIS PATTERN. TEMPERATURES FOR SAT AND SUN WILL
REMAIN BELOW NORMAL STAYING IN THE LOWER TO MID 20S FOR HIGHS AND
SINGLE DIGITS FOR OVERNIGHT TEMPERATURES.

SNOWFALL AMOUNTS AT ANY PARTICULAR PERIOD WILL NOT BE
HEAVY...HOWEVER LIGHT SNOW OVER A LONGER PERIOD OF TIME WILL
ACCUMULATE UNDER COOLER TEMPERATURES.

FOR THE BEGINNING OF NEXT WEEK THE MODELS BEGIN TO DIVERGE ON THE
PLACEMENT AND MOVEMENT OF THE UPPER LEVEL LOW PRESSURE SYSTEM OVER
THE GREAT BASIN. WITH BOTH MODELS MOISTURE AND COOLER TEMPERATURES
WILL REMAIN WITH LIGHT SNOW POSSIBLE THROUGH THE EXTENDED PERIOD.
TEMPERATURES WILL START TO IMPROVE TUESDAY INTO WEDNESDAY WITH
ABOVE FREEZING BEING A POSSIBILITY.

&&

.AVIATION...(FOR THE TAFS THROUGH 06Z THURSDAY EVENING)
ISSUED AT 1020 PM MST WED FEB 25 2015

DIA AND BJC SHOULD SEE SUBSTANTIAL IMPROVEMENT IN CIGS AND VSBYS
IN THE NEXT 30 MINS OR SO AS THE ARCTIC COLD FRONT AND ITS BAND
OF HVY SNOW AND STG GUSTY WINDS CONTINUES TO MOVE SOUTH AWAY FROM
THESE AIRPORTS. WHEREAS APA ON THE SOUTH SIDE OF THE DENVER METRO
AREA SHOULD EXPERIENCE HVY SNOW AND NEAR WHITEOUT CONDITIONS FOR
AT LEAST ANOTHER 30-45 MINS WITH THE FRONT MOVING THROUGH THE
AREA AT THE MOMENT. ONE-TWO INCH PER HOUR SNOWFALL RATES POSSIBLE
WITHIN THIS SNOW BAND AND GUSTS OF 20-30KTS. BY MIDNIGHT SHOULD
SEE SNOWFALL DIMINISHING ACRS NERN COLORADO AS COLDER AND DRIER
AIR SPILLS DOWN FORM WYOMING. ANY ADDITIONAL SNOW ACCUMULATION ON
THE PLAINS AFTER 07Z SHOULD BE UNDER 2 INCHES. IN THE HIGH
COUNTRY...NOT NOT HAPPENING UP THERE BASED ON RADAR AND SFC OBS.
LIGHT SNOW HAS BEEN CONFINED TO THE HIGHER PEAKS AND RIDGES WHILE
THE MTN VALLEYS IN JACKSON AND GRAND COUNTIES HAVE SEEN LITTLE
SNOW THIS HIGH PLAINS UPSLOPE SNOW EVENT. ALTHOUGH SOUTH PARK HAS
SEEN ITS SHARE OF SNOW PAST SEVERAL HOURS...PROBABLY IN THE 2-6
INCH RANGE BASED ON THE 3-STAR SNOW OBS AT ST. GEORGE THE PAST FEW
HOURS.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY UNTIL 6 AM MST THURSDAY FOR COZ033-034-
040-041-043.

WINTER STORM WARNING UNTIL 6 AM MST THURSDAY FOR COZ035-036-039.

&&

$$

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



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