000
FXUS65 KPUB 280315 AAA
AFDPUB
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE PUEBLO CO
815 PM MST MON DEC 27 2010
.UPDATE...
SOME UNCERTAINTIES REMAIN WITH THE UPCOMING MID WEEK STORM...WHICH
COULD IMPACT SNOW AMOUNTS AND TIMING OF HEAVIEST SNOWFALL. THE 00Z
NAM IS A BIT SLOWER IN DEVELOPING THE H5 LOW...AND PLACES THE
CENTER OVR SW UT ON FRI MORN RATHER THAN THE SE CO POSITION FOUND
IN THE 18Z NAM. THIS IS AN EVEN GREATER DEPARTURE FROM THE 18Z
GFS...WHICH HAS THE LOW IN NW KS AT THE SAME TIME. STILL LOOKS
HIGHLY PROBABLY THAT THE SAN JUANS WILL SEE SIGNIFICANT
ACCUMULATIONS FROM THIS SYSTEM WITH SUCH A STRONG SWRLY JET MOVING
INTO THE REGION ON WED. HOWEVER...SNOWFALL FOR THE NRN AND ERN
MTNS MAY BE IN JEOPARDY DEPENDING ON THE TRACK OF THE SYSTEM.
WILL LEAVE WATCH OUT FOR THE NRN RANGES INTACT FRO NOW...THOUGH
LATER SHIFTS MAY HAVE TO ADJUST TIMING OR EXPECTED AMOUNTS
SOMEWHAT. ROSE
&&
.PREV DISCUSSION... /ISSUED 238 PM MST MON DEC 27 2010/
SHORT TERM...
(TONIGHT AND TUESDAY)
NO SIGNIFICANT CONCERNS IN THE SHORT TERM. WED CAMS AT LEADVILLE,
MONARCH SKI AREA AND MONARCH PASS ARE NO LONGER SHOWING SNOW AND CAN
SEE A LITTLE BIT OF SUN AT TIMES. THUS WL LEAVE CHANCES FOR
ACCUMULATING PCPN OUT OF THE FORECAST FOR THESE AREAS THIS
EVENING...AND THE REST OF THE FORECAST AREA WL BE DRY AS WELL.
OTHERWISE HIGH CLOUDS ARE SPREADING ACRS THE ENTIRE FORECAST AREA.
AN UPR TROF...WITH ITS MAIN ENERGY OVR NEW MEXICO...WILL BE MOVING
EASTWARD TONIGHT...AND THE HIGHER CLOUDS ASSOCIATED WITH THIS SYSTEM
WILL CONTINUE COVERING THE FORECAST AREA THRU THE NIGHT AND INTO TUE
WHEN THEY WILL START TO DECREASE THRU THE DAY FROM WEST TO EAST.
TUE WL BE ANOTHER DAY WITH HIGH TEMPS A BIT ABOVE NORMAL.
LONG TERM...
(TUESDAY NIGHT THROUGH MONDAY)
MODELS IN DECENT AGREEMENT FOR THE MOST PART THROUGH FRIDAY
MORNING BEFORE BIG DIFFERENCES ARISE FOR THE WEEKEND. AS FOR THE
STORM SYSTEM THAT WILL IMPACT THE REGION MID TO LATE
WEEK...FOLLOWED A BLEND OF THE NAM STORM TRACK AND ECMWF TIMING
WHICH HAVE THE BEST SUPPORT FROM GEFS AND THE GFS ENSEMBLE. THE
GFS HAS REALLY CHANGED IN THE PAST 24 HOURS AND HAS BECOME THE
OUTLIER OF THE OPERATIONAL RUNS AND WILL DISREGARD IT FOR NOW. IT
SHOULD BE NOTED THAT VERY HIGH ENSEMBLE SPREADS AND RADICALLY
DIFFERENT OPERATIONAL SOLUTIONS BEYOND FRIDAY HAVE LEAD TO A VERY
LOW CONFIDENCE FORECAST FOR SATURDAY THROUGH MONDAY.
EXPECT QUIET CONDITIONS ACROSS COLORADO TUESDAY NIGHT AHEAD OF A
STRONG STORM SYSTEM DROPPING SOUTH ALONG THE WEST COAST. CLOUDS
ARE FORECAST TO SPREAD OVER THE STATE AHEAD OF THE STORM AS
PACIFIC MOISTURE BEGINS TO ADVECT ACROSS THE REGION. MODELS DIFFER
ON TIMING OF SNOW ONSET FOR THE CONTINENTAL DIVIDE HOWEVER EXPECT
LIGHT SNOW TO DEVELOP BY WEDNESDAY MORNING AND INCREASE RAPIDLY BY
WEDNESDAY AFTERNOON. SNOW ALONG THE CONTINENTAL DIVIDE WILL BECOME
MODERATE TO HEAVY WEDNESDAY AFTERNOON AND PERSIST THROUGH FRIDAY
MORNING AS THE MAIN STORM SYSTEM PASSES OVERHEAD. THE LATEST MODEL
CROSS SECTIONS OVER THE SOUTHERN SANGRE DE CRISTO RANGE HAVE
BACKED OFF ON THE DOWNSLOPE POTENTIAL FOR WEDNESDAY INTO THURSDAY
HOWEVER WINDS WILL LIKELY BE GUSTY ALONG THE RIDGE TOPS AND LEE
SLOPES WEDNESDAY AND WEDNESDAY NIGHT. A FEW GUSTS IN THE 40 TO 50
MPH RANGE ARE POSSIBLE OVER THE HIGHER ELEVATIONS WITH 30 TO 40
MPH POSSIBLE ALONG THE LEE SLOPES. HIGH TEMPERATURES ON WEDNESDAY
WILL REACH THE MID TO UPPER 50S FOR THE PLAINS WITH DECENT MIXING
ACROSS THE REGION.
SNOW WILL SLOWLY SPREAD EAST INTO THE EASTERN MOUNTAINS WEDNESDAY
NIGHT AS THE MAIN STORM SYSTEM TRACKS INTO THE FOUR CORNERS
REGION AND EJECTS INTO THE NORTHERN PLAINS ON FRIDAY. EXPECT ONE
LAST WARM DAY ACROSS THE PLAINS ON THURSDAY BEFORE A STRONG ARCTIC
COLD FRONT DROPS SOUTH ACROSS COLORADO THURSDAY EVENING. MODELS
AGAIN DIFFER ON TIMING WITH THE PREFERRED LATER FRONTAL PASSAGE OF
THE NAM...ECMWF AND PREVIOUS RUNS OF THE GFS. ALL HAVE THE FRONT
DROPPING ACROSS THE PLAINS AFTER 00Z AND INTO NEW MEXICO IN THE
06Z TO 09Z TIME FRAME. IT SHOULD BE NOTED THAT THE CURRENT GFS IS
MUCH FASTER WITH THE FRONT ALREADY ACROSS THE PLAINS BY 18Z
THURSDAY MORNING. WITH THE EXPECTED LATER FRONTAL
ARRIVAL...AFTERNOON TEMPERATURES ARE EXPECTED TO RISE INTO THE
LOWER TO MID 50S FOR THE PLAINS. IF THE FRONT COMES THROUGH
EARLIER AS THE LATEST COUPLE OF GFS RUNS SUGGEST...AFTERNOON HIGHS
WOULD STRUGGLE TO MAKE IT OUT OF THE 30S OR 40S FOR THE PLAINS.
ONE THING IS FOR CERTAIN...ONCE THE FRONT COMES THROUGH
TEMPERATURES WILL PLUMMET QUICKLY!
MODELS ALSO DIFFERING ON THE PROBABILITY OF PRECIPITATION FOR THE
PLAINS THURSDAY NIGHT INTO FRIDAY. THE OUTLIER GFS DEVELOPS A 12
HOUR PERIOD OF LIGHT TO MODERATE SNOWFALL FOR THE PLAINS WHILE THE
ECMWF WITH ITS MORE NORTHERLY TRACK KEEPS ALMOST ALL PRECIPITATION
CONFINED TO THE PALMER DIVIDE AND NORTHEAST COLORADO LEAVING DRY
CONDITIONS ACROSS THE PLAINS. AS MENTIONED...THE PREFERRED TRACKS
IS FURTHER SOUTH THAN THE ECMWF AND THEREFORE HAVE KEPT SLIGHT
CHANCE TO CHANCE POPS FOR THE PLAINS BEHIND THE COLD FRONT AND
PERSISTING INTO FRIDAY. CURRENTLY THINK SNOWFALL ACROSS THE PLAINS
WILL BE LIGHT WITH ONLY AN INCH OR TWO OF ACCUMULATIONS EXPECTED.
HOWEVER FOR THE MOUNTAINS...SIGNIFICANT ACCUMULATIONS ARE
POSSIBLE WITH 1 TO 3 FEET POSSIBLE ABOVE 10 KFT. UP TO A FOOT OF
SNOW IS POSSIBLE BELOW 10 KFT. WINTER STORM WATCHES HAVE BEEN
RAISED FOR THE CONTINENTAL DIVIDE FROM WEDNESDAY AFTERNOON THROUGH
FRIDAY MORNING WITH HEAVY SNOW AND GUSTY WINDS CREATING HAZARDOUS
CONDITIONS. AFTERNOON HIGHS ON THURSDAY CONTINUE TO COME IN COLDER
WITH EACH MODEL RUN. LOWERED TEMPERATURES INTO THE LOWER 20S FOR
THE PLAINS WHICH IS STILL AROUND 10 DEGREES ABOVE THE LATEST
GUIDANCE. WOULD NOT BE SURPRISED TO SEE HIGHS ONLY IN THE LOWER
TEENS FOR THE PLAINS GIVEN THE EXTREMELY COLD AIR IN PLACE ACROSS
CANADA AND THE NORTHERN CONUS. LOWS THURSDAY NIGHT ARE EXPECTED TO
DROP TO NEAR THE ZERO DEGREE MARK FOR THE PLAINS...WITH -15 TO -20
FOR THE HIGH MOUNTAIN VALLEYS.
BEYOND FRIDAY MODELS DIVERGE WITH MORE SUPPORT FOR THE ECMWF
HOWEVER HIGH ENSEMBLE SPREAD GIVES LOW CONFIDENCE IN ANY SOLUTION.
EXPECT SNOW TO DECREASE ACROSS THE REGION FRIDAY AFTERNOON AND
EVENING WITH LIGHT SNOW PERSISTING ALONG THE CONTINENTAL DIVIDE.
MOST ENSEMBLE MEMBERS AND THE ECMWF KEEP NORTHERLY FLOW ACROSS
COLORADO THROUGH THE WEEKEND. THIS WILL KEEP THE AREA COLD WITH
HIGHS GRADUALLY WARMING INTO THE 30S BY MONDAY WITH OVERNIGHT LOWS
IN THE SINGLE DIGITS FOR MOST LOCATIONS. PRECIPITATION CHANCES DO
LOOK MINIMAL WITH LIGHT SNOW POSSIBLE FOR THE CONTINENTAL DIVIDE
THROUGH MONDAY. 88
AVIATION...
VFR EXPECTED AT ALL TAF SITES.
&&
.PUB WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WATCH FROM WEDNESDAY MORNING THROUGH LATE THURSDAY
NIGHT FOR COZ058-060-066-068.
&&
$$
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