320
FXUS65 KBOU 071135
AFDBOU
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DENVER/BOULDER CO
435 AM MST WED JAN 7 2026
KEY MESSAGES
- LESS WIND AND STILL UNSEASONABLY MILD WEDNESDAY.
- TRENDS CONTINUE TO SHOW INCREASING CHANCES OF MEASURABLE SNOW
FOR MOST OF THE AREA (MINUS THE NORTHEAST PLAINS) THURSDAY -
FRIDAY. PROBABILITY NOW UP TO 70-80% FOR AT LEAST AN INCH OR TWO
OF SNOW FOR MOST OF THE I-25 CORRIDOR SOUTH OF LOVELAND. SEVERAL
INCHES OF SNOW LIKELY (>60% CHANCE) OVER THE MOUNTAINS,
FOOTHILLS, AND PALMER DIVIDE.
- DESPITE GOOD CONFIDENCE IN ACCUMULATING SNOW, POTENTIAL HIGHER
END SOLUTIONS ACROSS THE FRONT RANGE AND DENVER METRO APPEAR TO
BE DIMINISHING.
- MUCH COLDER BY LATE THURSDAY AND FRIDAY.
- MODERATING TEMPERATURES THIS WEEKEND, WITH DRY WEATHER
PREVAILING THROUGH EARLY NEXT WEEK.
UPDATE
ISSUED AT 232 AM MST WED JAN 7 2026
IT WOULDN'T BE A FRONT RANGE WINTER STORM WITHOUT A SIGNIFICANT
MODEL SPREAD WITHIN 48 HOURS. DESPITE REASONABLY SIMILAR
EVOLUTION OF THE MAIN SYNOPTIC SCALE FEATURES, THERE'S ONCE AGAIN
RATHER LOW CONFIDENCE IN OUR DETERMINISTIC (I.E., "OFFICIAL")
GRIDS TONIGHT. WHY IS THAT? LET'S DIVE IN.
THERE ARE TWO MAIN SHORTWAVES THAT PLAY A ROLE IN THE STORM HERE.
THE PRIMARY/LEAD WAVE SHOULD REACH NORTHERN BAJA CALIFORNIA LATER
TODAY, WHILE THE SECONDARY WAVE SHOULD BE NEAR THE PACIFIC
NORTHWEST COAST AROUND THE SAME TIME. THESE TWO SHORTWAVES
INTERACT JUST ENOUGH TO EJECT THE LEAD WAVE OUT INTO THE CENTRAL
GREAT PLAINS BY MIDDAY THURSDAY. FAIRLY IMPRESSIVE CYCLOGENESIS -
WITH A 996MB LOW TRACKING FROM CENTRAL KS INTO CENTRAL IA BY
THURSDAY EVENING - IS EXPECTED TO HELP REINFORCE A SURFACE COLD
FRONT AND NORTHERLY SURFACE FLOW IN NORTHEASTERN COLORADO. TRENDS
WITH BOTH THE SFC AND 700MB LOW FAVOR FOR A STRONGER/FURTHER
NORTH TRACK WITH THIS INITIAL LOW... AND SEVERAL MODELS HAVE A
LESS FAVORABLE NNW (OR EVEN NW) LOW-LEVEL FLOW THAT WOULD LIMIT
THE AMOUNT OF UPSLOPE ACROSS OUR FORECAST AREA. SEVERAL MODELS
HAVE LITTLE OR NO QPF DURING THE DAY THURSDAY AS A RESULT OF SOME
OF THESE CHANGES (ALONG WITH SOME HIGHLY QUESTIONABLE BOUNDARY
LAYER MOISTURE PROFILES), THOUGH A FEW MODELS (GFS/NAM AND BOTH
THE ARW/FV3 WRFS) STILL MANAGE TO PRODUCE A GOOD WINDOW OF
UPSLOPE SNOW DURING THE DAY. WITH STEEP LAPSE RATES ALOFT, THERE
MAY BE SOME CONVECTIVE SNOW SHOWERS EITHER WAY WHERE CONVERGENCE
IS MAXIMIZED (LIKELY SOMEWHERE OVER THE FRONT RANGE FOOTHILLS),
BUT ACCUMULATION WILL BE HEAVILY DEPENDENT ON HOW THE FIRST WAVE
BEHAVES.
THE SECOND PART OF THE STORM COMES THURSDAY NIGHT INTO FRIDAY, AS
THE TRAILING WAVE DIVES INTO THE FOUR CORNERS REGION, WHICH THEN
DRIFTS EAST-SOUTHEASTWARD INTO NEW MEXICO AND GRADUALLY SHEARS
OUT. A SECONDARY MID-LEVEL LOW IS EXPECTED TO DEVELOP IN NORTHERN
NEW MEXICO, LEADING TO A SECOND WINDOW OF POTENTIALLY DEEPER
UPSLOPE. ONCE AGAIN, A LOT OF THE OVERNIGHT MODELS FOUND IT TOO
DIFFICULT TO "THREAD THE NEEDLE" AND INSTEAD KEEP A LOT OF THE
SFC-700MB FLOW EITHER DUE N OR NNW... WITH A FEW MODELS STILL
DEVELOPING ENOUGH OF AN EASTERLY COMPONENT FOR WIDESPREAD SNOWFALL
OVER THE DENVER METRO. BY FRIDAY ANY UPSLOPE SHOULD QUICKLY
DIMINISH WITH DRIER AIR ALSO LIKELY SPREADING INTO THE REGION.
YOU MAY BE THINKING, "WELL THAT'S A LOT OF WORDS, BUT WHAT DOES IT
ACTUALLY MEAN FOR SNOWFALL AMOUNTS AT MY HOUSE?" GREAT QUESTION!
OUR ACTUAL FORECAST SNOWFALL TOTALS HAVE NOT CHANGED SIGNIFICANTLY
SINCE YESTERDAY AFTERNOON, DESPITE A RATHER SIGNIFICANT UPWARD
TREND IN QPF FROM THE NBM. OUR DETERMINISTIC SNOWFALL LIES CLOSER
TO THE LEFT TAIL OF THE PROBABILISTIC DISTRIBUTION, AND YET I
STILL FEEL THAT WE MAY BE TOO BULLISH ON SNOWFALL TOTALS,
ESPECIALLY FOR THE FOOTHILLS/I-25 CORRIDOR NORTH OF I-70. THIS IS
A CLEAR CASE WHERE THE PROBABILITY DISTRIBUTION FUNCTION IS
HEAVILY RIGHT-SKEWED. IN OTHER WORDS, THE MOST LIKELY FORECAST
SCENARIO FOR A PLACE LIKE DENVER IS GENERALLY AROUND 2-3" (~60%
CHANCE), BUT THERE WOULD BE POTENTIAL (~10%) FOR >6" IF
EVERYTHING CAN MANAGE TO COME TOGETHER. THAT WOULD BE A SIMILAR
STORY FOR PLACES IN THE FOOTHILLS AND PALMER DIVIDE, EXCEPT THE
"FLOOR" AND "CEILING" TO THE FORECAST ARE BOTH A LITTLE HIGHER.
WITH ALL THAT SAID... I DECIDED TO HOLD OFF ON ANY HIGHLIGHTS. WE
WERE CLOSE TO PULLING THE TRIGGER ON MOUNTAIN WINTER WEATHER
ADVISORIES AND A WINTER STORM WATCH FOR THE PALMER DIVIDE AND
SOUTHERN FOOTHILLS. INSTEAD, WE WILL LET THE DAY SHIFT EVALUATE
THE 12Z MODEL CYCLE AND GO FROM THERE.
BEYOND THIS UPCOMING STORM, THE FORECAST PATTERN SUPPORTS A
GRADUAL WARMING TREND ALONG WITH QUIETER/DRIER WEATHER FROM THIS
WEEKEND INTO NEXT WEEK.
DISCUSSION /THROUGH TUESDAY/
ISSUED AT 235 PM MST TUE JAN 6 2026
RADAR INDICATES THE MOUNTAIN WAVE THAT BROUGHT SIGNIFICANT WINDS
TO AREAS IN AND ADJACENT TO THE FOOTHILLS LAST NIGHT AND THIS
MORNING IS RETREATING BACK UP THE FRONT RANGE. MEANWHILE, GUSTY
WINDS HAVE SPREAD ACROSS A GOOD CHUNK OF THE PLAINS DUE TO DAYTIME
HEATING AND MIXING. THOSE WILL BE DECREASING WITH SUNSET OR
SHORTLY BEFORE, BRINGING AN END TO OUR FIRE WEATHER THREAT.
ON WEDNESDAY, WE'LL BE UNDER THE INFLUENCE OF FLAT RIDGING ALOFT.
THIS WILL MEAN WEAKER GRADIENTS AND LIGHTER WINDS FOR A WELCOME
CHANGE. TEMPERATURES SHOULD BE ABLE TO REACH LEVELS SIMILAR TO
TODAY, WITH UPPER 50S/NEAR 60F DEGREE READINGS ACROSS THE PLAINS
AND I-25 ONCE MORE.
ALL EYES ARE LOOKING TO THURSDAY, AS THE NEXT STORM SYSTEM ARRIVES
USHERING IN COLDER TEMPERATURES AND A RARE BUT MEANINGFUL CHANCE
OF ACCUMULATING SNOW. CLUSTER ANALYSIS SHOWED ABOUT TWO THIRDS OF
THE TOTAL RUNS (MAINLY EPS MEMBERS) SHOWING A DEEPER MID LEVEL
TROUGH MOVING TOWARD THE FOUR CORNERS BY THURSDAY NIGHT, WHILE
ABOUT A THIRD WERE STILL MORE PROGRESSIVE AND WEAKER. WITH THIS
TYPE OF PATTERN EVOLVING WE WOULD FAVOR THE DEEPER SOLUTION. THAT
WOULD GIVE US A LITTLE BETTER UPSLOPE COMPONENT AND THUS A HIGHER
PROBABILITY OF MORE MEANINGFUL PRECIPITATION. THAT SAID, THAT
TRACK ALSO KEEPS THE BEST LIFT AND MOISTURE TO OUR SOUTH, AND
CROSS SECTIONS SHOW SOME DRY INTRUSIONS FROM THE NORTH. AS A
RESULT, THE HIGHEST PROBABILITIES FOR SEVERAL INCHES OF SNOW WOULD
STAY OVER THE MOUNTAINS, FOOTHILLS, AND PALMER DIVIDE. DENVER
WOULD ESSENTIALLY BE IN THE MIDDLE, WITH MOST LIKELY A 1-4"
FORECAST ACROSS METRO - FAVORING THE SOUTH/WEST SIDES. IT SHOULD
BE NOTED THERE ARE A COUPLE GEFS OUTLIERS WITH MORE SIGNIFICANT
TOTALS IN EXCESS OF 6" FOR DENVER, BUT THE PROBABILITY OF THAT IS
VERY SMALL, AS IN LESS THAN 10%. IN FACT, ONLY 4 OF THE 51 EPS
MEMBERS PRODUCED ANYTHING MORE THAN 4" FOR DENVER. AT LEAST ALMOST
ALL MEMBERS HAVE LIGHT MEASURABLE SNOW. CHANCES OF SNOW GREATER
THAN AN INCH GRADUALLY DECREASE TO THE NORTHEAST OF DENVER ACROSS
THE PLAINS, LARGELY BECAUSE OF WEAKER LIFT AND POTENTIAL FOR DRY
AIR INTRUSION.
THERE COULD BE A LITTLE RAIN/SNOW MIX TO START THURSDAY, BUT WITH
COLD ADVECTION THAT WILL CHANGE OVER TO ALL SNOW WITH TRAVEL
IMPACTS LIKELY BY EVENING. DEPENDING ON SNOW RATES, THIS COULD
IMPACT THE THURSDAY EVENING COMMUTE IN DENVER AND THE
FOOTHILLS/MOUNTAINS. SNOW GRADUALLY DECREASES NORTH TO SOUTH
THURSDAY NIGHT INTO EARLY FRIDAY MORNING AS THE STORM SYSTEM PULLS
INTO KANSAS, BUT IT LOOKS LIKE FRIDAY MORNING'S COMMUTE WOULD
STILL BE IMPACTED DUE TO THE COLDER TEMPERATURES AND SNOW COVERED
ROADS. HIGHS ON FRIDAY WILL LIKELY ONLY RECOVER TO NEAR THE
FREEZING MARK, BUT WITH THE INCREASE IN SOLAR INSOLATION TRAVEL
CONDITIONS WOULD BE MUCH IMPROVED FOR THE LATE MORNING AND
AFTERNOON.
SATURDAY WILL FEATURE NORTHWEST FLOW AND POTENTIAL FOR A WEAK
TRAILING DISTURBANCE. TEMPERATURES WILL ONLY MODERATE TO NEAR
SEASONAL NORMALS, BUT THAT'LL STILL FEEL COLD COMPARED TO OUR
RECENT WARMTH. FURTHER MODERATION TO ABOVE NORMAL TEMPERATURES IS
EXPECTED BY SUNDAY INTO EARLY NEXT WEEK. HOWEVER, DESPITE RIDGING
ALOFT AND MAINLY DRY CONDITIONS, WE'LL STILL BE PRONE TO BACKDOOR
COLD FRONTS ACROSS THE PLAINS AND THUS BRIEF COOLDOWNS.
AVIATION /12Z TAFS THROUGH 12Z THURSDAY/
ISSUED AT 420 AM MST WED JAN 7 2026
VFR CONDITIONS ARE EXPECTED THROUGH THIS EVENING, WITH
DETERIORATING CONDITIONS BY THURSDAY MORNING. DRAINAGE WINDS
SHOULD EVENTUALLY TURN TO THE EAST OR NORTHEAST BY THE AFTERNOON
HOURS WITH LIGHT SPEEDS. MUCH LOWER CONFIDENCE WIND/CEILING
FORECAST OVERNIGHT TONIGHT, AS A POORLY DEFINED COLD FRONT WORKS
INTO THE REGION. THERE SHOULD BE STEADIER NORTH OR NORTHEAST WINDS
DEVELOPING AFTER 06Z TONIGHT, WITH CEILINGS ALSO LOWERING. SOME
GUIDANCE TRIES TO BRING MVFR/IFR CIGS TO THE TERMINALS PRIOR TO
12Z, WHILE SOME DRIER SOLUTIONS MAINTAIN VFR (BUT LIKELY STILL
ILS) CONDITIONS THROUGH THE TAF PERIOD. THURSDAY MORNING ALSO
COULD SEE THE DEVELOPMENT OF SOME SHSN WITH HIGHER PROBABILITIES
OF MVFR/IFR VISBY AND CIGS BETWEEN 12-18Z THURSDAY MORNING.
BOU WATCHES/WARNINGS/ADVISORIES
NONE.
UPDATE...HIRIS
DISCUSSION...20
AVIATION...HIRIS
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