908
FXUS65 KBOU 291758
AFDBOU
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DENVER/BOULDER CO
1058 AM MST WED JAN 29 2025
KEY MESSAGES
- QUIET TODAY.
- CONTINUED UNCERTAINTY WITH THE FORECAST TONIGHT INTO THURSDAY.
CHANCE FOR SNOW ACROSS THE METRO AND EASTERN PLAINS, BUT LITTLE
CONFIDENCE IN SNOWFALL TOTALS. BEST CHANCE OF ACCUMULATING SNOW
ACROSS THE PALMER DIVIDE INTO THE FAR EASTERN METRO.
- WARMER BUT BREEZY FRIDAY THROUGH THE WEEKEND. LOTS OF
UNCERTAINTY WITH THE MAGNITUDE OF A BACKDOOR COLD FRONT SUNDAY
NIGHT INTO EARLY NEXT WEEK.
UPDATE
ISSUED AT 1042 AM MST WED JAN 29 2025
MAIN PRIORITY THIS MORNING HAS BEEN TO PUSH OUT WINTER WEATHER
HIGHLIGHTS FOR THE PALMER DIVIDE AND PORTIONS OF THE PLAINS. THERE
IS STILL SOME FLIP-FLOPPING AND DIVERGENCE IN THE PLACEMENT OF THE
HEAVIEST BAND OF SNOW BETWEEN HI-RES AND GLOBAL MODEL SUITES,
HOWEVER THE FORMER ARE LESS BULLISH ON POTENTIAL FOR SIGNIFICANT
IMPACTS FOR MOST OF THE DENVER METRO (THE SOUTHEAST CORNER BEING
THE EXCEPTION). ON THE HIGH END, LOCALIZED ACCUMULATIONS OF 6-9"
ARE NOT OUT OF THE QUESTION WITHIN THE CORE OF THE BAND (MOST
LIKELY FROM THE PALMER DIVIDE NORTHEAST INTO THE I-70 CORRIDOR
EAST OF DENVER), BUT MOST LOCATIONS WITHIN THE POSTED ADVISORIES
SHOULD END UP WITH CLOSER TO 1-4".
WILL LIKELY NEED TO MAKE SOME ADJUSTMENTS TO CURRENT PRECIPITATION
FORECASTS WITH THIS UPCOMING PACKAGE TO SHIFT THE AXIS OF
HEAVIEST ACCUMULATIONS EASTWARD SLIGHTLY AND AWAY FROM THE
SOUTHERN FOOTHILLS.
SHORT TERM /THROUGH TONIGHT/
ISSUED AT 245 AM MST WED JAN 29 2025
WATER VAPOR SATELLITE SHOWS THE CENTER OF AN UPPER LEVEL LOW
SPINNING OVER CENTRAL ARIZONA THIS MORNING, AND THIS WILL BE THE
FEATURE TO WATCH OVER THE NEXT 24-36 HOURS AS IT STRENGTHENS AND
TURNS MORE EAST-NORTHEASTWARD TONIGHT INTO TOMORROW.
CLOUD COVER SHOULD GRADUALLY INCREASE TODAY, BUT OTHERWISE THE
WEATHER SHOULD REMAIN QUIET THROUGH THE DAYTIME HOURS.
TEMPERATURES SHOULD BE NEAR NORMAL WITH HIGHS IN THE 40S ACROSS
THE LOWER ELEVATIONS.
AS THE CLOSED LOW APPROACHES THIS EVENING INTO TONIGHT, THE LOW
LEVEL FLOW SHOULD STRENGTHEN OUT OF THE SOUTHEAST, WITH A FAIRLY
IMPRESSIVE MOISTURE PLUME ADVECTING INTO THE SOUTHEASTERN PORTION
OF THE CWA. THERE SHOULD BE AT LEAST SOME SCATTERED SNOW SHOWERS
DEVELOPING AFTER MIDNIGHT, MAINLY OVER THE PLAINS SOUTH OF I-70,
WITH RAIN MIXING IN CLOSER TO THE KS BORDER. AS YOU'LL READ BELOW,
GUIDANCE REMAINS SPLIT ON IF THIS MOISTURE WILL MAKE IT INTO THE
METRO. IF THE STRENGTHENING UPSLOPE FLOW IS ENOUGH TO OVERCOME THE
DRIER NORTH-NORTHWEST SURFACE FLOW, SNOW SHOWERS WILL LIKELY
DEVELOP A LITTLE BEFORE SUNRISE EARLY THURSDAY AM, WHICH WOULD
THEN CONTINUE THROUGH THE FIRST HALF OF THURSDAY.
LONG TERM /THURSDAY THROUGH TUESDAY/
ISSUED AT 245 AM MST WED JAN 29 2025
MAIN ISSUE FOR THU WILL BE SNOW POTENTIAL OVER PORTIONS OF NERN CO
AND THE PALMER DIVIDE DUE TO A CLOSED LOW OVER SERN CO. OVERALL,
THE SAME QUESTIONS CONTINUE TONIGHT AS WAS THE CASE LAST NIGHT. THE
00Z RUNS OF THE HIGHER RES MODELS HAVE A BAND OF HEAVIER SNOW
EXTENDING FROM THE PALMER DIVIDE ACROSS THE DENVER METRO AREA
NORTHEAST TOWARDS FORT MORGAN AND STERLING. MEANWHILE THE ECMWF,
GEM AND GFS HAVE A POTENTIAL BAND OF HEAVIER SNOW FURTHER EAST FROM
ERN PORTIONS OF THE PALMER DIVIDE TO FORT MORGAN TO STERLING.
OVERALL, THE MAIN DIFFERENCES BETWEEN THESE SOLUTIONS APPEARS TO
BE THE LOWER LEVEL FLOW. ANALYSIS OF 850-700 MB WINDS FROM THE
HIGH RES DATA HAS A NNE COMPONENT WHILE THE ECMWF, GEM AND GFS
HAVE A NORTHERLY COMPONENT ALONG THE I-25 CORRIDOR. ALTHOUGH I
CAN'T SAY WITH 100% CERTAINTY THE HI RES MODELS ARE WRONG, I WOULD
FAVOR A MORE EASTWARD PLACEMENT OF A POTENTIAL HEAVIER SNOW BAND
MORE IN LINE WITH THE ECWMF AND GFS OPERATIONAL SOLUTIONS.
MEANWHILE, ENSEMBLE DATA FROM THE ECMWF AND GFS ALSO PLACE THE
BEST CHANCE FOR HEAVIER SNOWFALL IN GENERAL AGREEMENT WITH THEIR
OPERATIONAL RUNS. AS A RESULT, HAVE KEPT THE HIGHER SNOW AMOUNTS
EAST AND SOUTHEAST OF THE DENVER METRO AREA.
IN ADDITION TO THE SNOW GUSTY NORTH WINDS WILL DEVELOP BY MID TO
LATE MORNING AND CONTINUE THRU THE AFTN. THUS THERE WILL BE AREAS
OF BLOWING SNOW AND POOR VISIBILITY AS WELL. WILL LIKELY NEED
ADVISORIES ACROSS THE PALMER DIVIDE AND POSSIBLY PORTIONS OF THE
PLAINS THRU EARLY TO MID AFTN.
BY EARLY THU EVENING THE UPPER LEVEL LOW WILL GRADUALLY MOVE
EASTWARD INTO THE CENTRAL PLAINS WITH SNOW ENDING OVER THE PLAINS BY
LATE AFTN.
LOOKING AHEAD TO FRI AND SAT THE FLOW ALOFT WILL BECOME ZONAL WITH
DOWNSLOPE FLOW. SOME MOISTURE EMBEDDED IN THE FLOW MAY AFFECT THE
NRN MTNS ON SAT WITH A CHC OF OROGRAPHIC SNOW SHOWERS. ACROSS THE
PLAINS IT WILL BE DRY WITH WARMER TEMPS AS READINGS WILL BE 10-15
DEGREES ABOVE NORMAL BY SAT AFTN.
ON SUN, THE FLOW ALOFT WILL REMAIN ZONAL. THERE ARE DIFFERENCES
BETWEEN THE ECMWF AND GFS AS TO HOW MUCH MOISTURE WILL BE EMBEDDED
IN THE FLOW. THE ECMWF HAS FAR LESS MOISTURE THAN THE GFS. AT THIS
POINT NOT SURE WHICH SOLUTION IS THE BEST SO WILL JUST KEEP IN A CHC
OF SNOW SHOWERS IN THE NRN MTNS. ACROSS THE PLAINS, IT WILL BE DRY
WITH HIGHS REMAINING ABOVE NORMAL. FURTHERMORE, THERE WILL BE
PERIODS OF GUSTY WINDS BOTH SAT AND SUN OVER THE HIGHER TERRAIN AS
WELL.
FOR MON AND TUE THE FLOW ALOFT WILL BECOME MORE WSW. THERE ARE
MAJOR DIFFERENCES BETWEEN THE ECMWF AND THE GFS WITH THE HANDLING OF
A SHALLOW COLD AIRMASS WHICH MAY AFFECT THE PLAINS ON MON. THE ECMWF
KEEPS THE SHALLOW COLD AIR TO THE NORTH AND NORTHEAST WHILE THE GFS
HAS IT MOVING ACROSS THE PLAINS INTO THE I-25 CORRIDOR. THIS
DIFFERENCE IS REFLECTED IN TEMP GUIDANCE AS THE GFS HAS HIGHS IN THE
30'S AROUND DENVER WHILE THE ECMWF HAS READINGS IN THE UPPER 60S DUE
TO DOWNSLOPE WARMING. BY TUE, THE ECMWF HAS SOME OF THE SHALLOW
COLD AIR AFFECTING NERN CO WHILE THE GFS HAS THE COLDER AIRMASS
STILL ENTRENCHED ACROSS THE PLAINS INTO THE I-25 CORRIDOR. BLENDED
SOLUTIONS HAVE KEPT IN WARMER SOLUTIONS FOR MON AND TUE WHICH
COULD BE WAY OFF IF THE SHALLOW COLD AIRMASS DOES MOVE INTO THE
AREA.
AVIATION /18Z TAFS THROUGH 18Z THURSDAY/
ISSUED AT 1042 AM MST WED JAN 29 2025
ALL TERMINALS WILL BE VFR THROUGH AT LEAST 03Z THU. EXPECT CIGS TO
DEVELOP 04-05Z FOR THE DENVER AREA WITH BASES 040-060, LOWERING
CLOSER TO 020-030 AFTER 09Z WHEN THE PROBABILITY OF SNOW SHOWERS
WILL INCREASE. BOTH KDEN AND KAPA SHOULD REMAIN VERY CLOSE TO THE
WESTERN EDGE OF THE BAND OF HEAVIER SNOW THROUGH THU AM,
RESULTING IN VERY HIGH UNCERTAINTY IN ACCUMULATIONS AND SEVERITY
OF VIS/CIG RESTRICTIONS. WILL CONTINUE TO MESSAGE LOW POTENTIAL
FOR PERIOD OF HEAVIER SN, MAINLY 11-17Z. LOW CIGS AND SNOW WILL
CLEAR RAPIDLY ~17-19Z FROM WEST TO EAST, WITH BREEZY N/NW
DEVELOPING AROUND THAT TIME. GUSTS WILL LIKELY REACH/EXCEED 25 KTS
AT KDEN THU PM.
BOU WATCHES/WARNINGS/ADVISORIES
WINTER WEATHER ADVISORY FROM 5 AM TO 2 PM MST THURSDAY FOR
COZ041-044-045-049.
WINTER WEATHER ADVISORY FROM 11 PM THIS EVENING TO NOON MST
THURSDAY FOR COZ046-047.
UPDATE...RODRIGUEZ
SHORT TERM...HIRIS
LONG TERM...RPK
AVIATION...RODRIGUEZ
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