044
FXUS65 KBOU 061133
AFDBOU
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DENVER/BOULDER CO
433 AM MST TUE JAN 6 2026
KEY MESSAGES
- GUSTY WINDS CONTINUE TODAY, ALONG WITH ELEVATED TO CRITICAL FIRE
WEATHER CONDITIONS... ESPECIALLY ACROSS BOULDER AND JEFFERSON
COUNTIES.
- LOWER ELEVATIONS WILL REMAIN DRY AND MILD THROUGH WEDNESDAY.
- STILL EXPECTING COLDER, UNSETTLED WEATHER RETURNING FOR THURSDAY
AND FRIDAY. CHANCES OF MEASURABLE SNOW INCREASING TO 60-70% FOR
I-25 URBAN CORRIDOR.
UPDATE
ISSUED AT 226 AM MST TUE JAN 6 2026
AS EXPECTED, THERE'S BEEN A FAIRLY IMPRESSIVE MOUNTAIN WAVE SETUP
THAT DEVELOPED AROUND MIDNIGHT HERE. MOST OF THE GUSTY WINDS HAVE
BEEN CONFINED TO THE LOWER ELEVATIONS OF BOULDER/JEFFERSON
COUNTIES, WHERE THERE'S BEEN A HANDFUL OF GUSTS BETWEEN 60-70 MPH.
MEANWHILE, THERE'S BEEN A FEW BURSTS OF HEAVY SNOW ACROSS THE
MOUNTAINS OVERNIGHT, BUT SNOW SHOULD BE QUICKLY WRAPPING UP HERE
WITHIN THE NEXT COUPLE OF HOURS.
UNSURPRISINGLY, NBM WINDS IN THE SHORT TERM PERIOD HAVE NOT EVEN
COME CLOSE TO CAPTURING THE DETAILS ACROSS THE FRONT RANGE/I-25
CORRIDOR... WHILE A COUPLE MESOSCALE (HRRR/RRFS/RGEM) AND
STATISTICAL (GRIDDED LAMP) CONTINUE TO BE REMARKABLY GOOD WITH
BOTH THE EASTWARD EXTENT AND MAGNITUDE OF THE WINDS HERE. THE MAIN
UPDATE WITH THE OVERNIGHT FORECAST PACKAGE WAS TO MAKE
SUBSTANTIAL HAND EDITS TO THE GRIDS THROUGH THIS AFTERNOON...
CLOSELY FOLLOWING A BLEND OF THE AFOREMENTIONED GUIDANCE. IN
GENERAL, 40-60 MPH GUSTS APPEAR LIKELY TO CONTINUE THROUGH AT
LEAST AROUND MIDDAY FOR PLACES NEAR THE BASE OF THE FOOTHILLS FROM
ROUGHLY GOLDEN TO LYONS, WITH WEAKER WINDS FURTHER EAST. WITH
THOSE CHANGES TO THE WIND FORECAST ALSO COME SOME CHANGES TO THE
EXISTING FIRE WX HIGHLIGHTS... BUT MORE ON THAT IN THE FIRE
SECTION BELOW.
BEYOND TODAY, LITTLE CHANGE WAS NEEDED TO THE EXISTING FORECAST.
WEDNESDAY STILL LOOKS MILD AND DRY, BUT CERTAINLY LESS WINDY
ACROSS THE CWA. DETERMINISTIC GUIDANCE CONTINUES TO WOBBLE BACK
AND FORTH BETWEEN WETTER AND DRIER SOLUTIONS FOR THURSDAY/FRIDAY'S
SYSTEM, BUT IN GENERAL ENSEMBLE MEAN QPF HAS EITHER REMAINED
STEADY OR SLOWLY INCREASED IN THE PAST 12-24 HOURS. POPS IN THAT
PERIOD CONTINUE TO NUDGE UPWARD, BUT EVEN NOW THE MOST LIKELY
SCENARIO IS FOR ONLY LIGHT SNOW (AND MUCH COOLER TEMPERATURES)
OVER MOST OF THE PLAINS.
DISCUSSION /THROUGH MONDAY/
ISSUED AT 244 PM MST MON JAN 5 2026
BREEZY CONDITIONS HAVE SPREAD EAST ACROSS MOST OF THE PLAINS THIS
AFTERNOON, ALONG WITH ELEVATED TO NEAR CRITICAL FIRE WEATHER
CONDITIONS DUE TO CONTINUED DRYNESS AND LOW HUMIDITY. MEANWHILE,
IN THE MOUNTAINS WE'VE SEEN AN INCREASE IN CONVECTIVE SHOWERS,
SOME LOCALLY HEAVY PRODUCING SLICK AND HAZARDOUS WINTER TRAVEL.
THOSE SHOWERS WILL CONTINUE WELL INTO THIS EVENING, AND AS
TEMPERATURES DROP MORE IMPACTS WILL BE FOUND ON THE LOWER MOUNTAIN
SLOPES AND DOWN INTO THE MOUNTAIN VALLEYS. WE'LL MAINTAIN THE
WINTER WEATHER ADVISORY FOR ZONE 31 THROUGH THE NIGHT, WHILE
LESSER AMOUNTS OF SNOW (2-4" ADDITIONAL) CAN BE EXPECTED IN THE
FRONT RANGE MOUNTAINS INTO SUMMIT COUNTY. THE CONVECTIVE NATURE
AND PROXIMITY OF THE UPPER LEVEL JET MEANS A FEW SPOTS COULD GET
MORE. ALSO, IT WON'T BE IMPOSSIBLE TO SEE A BRIEF SHOWER OR TWO
SPILL ALL THE WAY ONTO THE NEARBY ADJACENT PLAINS DUE TO THE
INSTABILITY AND STRONG FLOW ALOFT. WE'VE ADDED A LOW POP FOR
LOCATIONS WEST OF I-25 EARLY THIS EVENING, BUT IT WOULDN'T BE
ANYTHING MORE THAN A BRIEF RAIN/GRAUPEL SHOWER. THE AIRMASS WILL
BE SUBSIDENT THROUGH THE NIGHT, AND WE'LL SEE A DRYING TREND WHICH
MEANS A DECREASE IN MOUNTAIN SNOWFALL OVERNIGHT. BY LATE TONIGHT
OR EARLY TUESDAY MORNING, WE DON'T EXPECT ANYTHING MORE THAN
LINGERING SCATTERED LIGHT SHOWERS.
THE CONTINUED SUBSIDENCE ALONG WITH MODEST GRADIENT AND WEAK
MOUNTAIN WAVE ENHANCEMENT DOES PROMOTE A CONTINUATION OF
BREEZY/WINDY CONDITIONS IN/NEAR THE FRONT RANGE OVERNIGHT. THOSE
WINDS WILL BE SPREADING EAST AGAIN THROUGH THE DAY TUESDAY WITH
FURTHER MIXING, ALTHOUGH GUIDANCE REMAINS MIXED ON EXACTLY HOW
STRONG AND HOW FAR EAST THEY MAKE IT. AT THIS TIME, IT APPEARS THE
STRONGEST WINDS WILL BE MAINLY FOCUSED TO AREAS WEST OF I-25 AND
ESPECIALLY BOULDER/NORTHERN JEFFERSON COUNTIES. WITH ADDITIONAL
DRYING BUT STILL MILD TEMPERATURES, WE'LL SEE AT LEAST ELEVATED IF
NOT CRITICAL FIRE WEATHER CONDITIONS ONCE AGAIN. WE WON'T BE
ISSUING ANY HIGHLIGHTS AT THIS TIME, HOWEVER, AS IT APPEARS THOSE
CONDITIONS WOULD BE RATHER LIMITED IN AREAL COVERAGE TO WHERE THE
STRONGEST WINDS AND LOWEST HUMIDITY OVERLAP. THAT WOULD BE MAINLY
EASTERN BOULDER AND NORTHEAST JEFFERSON COUNTY.
WEDNESDAY CONTINUES TO FEATURE SOMEWHAT CALMER WEATHER IN BETWEEN
WEATHER SYSTEMS AND FLAT RIDGING OVERHEAD. HOWEVER, IT WILL STILL
BE BREEZY AT TIMES ESPECIALLY IN/NEAR THE MOUNTAINS AND FOOTHILLS.
NOW, ADDRESSING OUR NEXT SHOT OF SNOW FOR THE LOWER ELEVATIONS...
MODELS HAVE TRENDED TO SOMEWHAT SNOWIER SOLUTIONS FOR THURSDAY
INTO EARLY FRIDAY. THERE'S A LITTLE BETTER AGREEMENT IN THE
ENSEMBLE DATA SHOWING A TROUGH DROPPING ACROSS THE NORTHERN
ROCKIES AND GREAT BASIN THURSDAY, AND THEN MOVING EAST/SOUTHEAST
ACROSS THE AREA BY EARLY FRIDAY. HOWEVER, WPC CLUSTER ANALYSIS
SHOWS A VARIETY OF FASTER/MORE PROGRESSIVE SYSTEMS, AND A
DIGGIER SOLUTION LIKE THE LATEST OPERATIONAL EC. WHAT WAS IN OUR
FAVOR IS THAT THE EC ENSEMBLE SYSTEM HAS NEARLY ALL MEMBERS
PRODUCING SNOW DOWN INTO DENVER AND THE MAJORITY OF THE I-25
CORRIDOR. MEAN SNOWFALL AMOUNTS HAVE INCREASED FROM 24 HOURS AGO,
AND REMAINED STEADY WITH THE LAST 12Z RUN AVERAGING ABOUT 0.25"
LIQUID EQUIVALENT FOR DENVER, AND A RELATIVELY NARROW RANGE OF
GUIDANCE FROM BOTTOM TO TOP. VERY FEW RUNS HAD GREATER THAN 5" OF
SNOW, SO OVERALL THIS STILL LOOKS LIKE A LIGHT SNOW EVENT. WITH
BETTER AGREEMENT IN AT LEAST SOME LIGHT PRECIPITATION, WE'VE
INCREASED OUR SNOW CHANCES WITH THIS FORECAST CYCLE. TEMPERATURES
WILL BE TURNING COLDER DURING THE DAY ON THURSDAY WITH COLD
ADVECTION AND SNOW DEVELOPMENT. THEREFORE, AS LONG AS IT SNOW INTO
THURSDAY NIGHT WE WOULD EXPECT SOME TRAVEL IMPACTS THAT COULD
LAST INTO EARLY FRIDAY MORNING.
AFTER THAT SYSTEM, WE'LL FALL INTO NORTHWEST FLOW AND POTENTIAL
FOR A COUPLE BACKDOOR COLD FRONTS INTO THE WEEKEND. THESE ARE VERY
DIFFICULT TO TIME BUT OVERALL IT APPEARS DRY WEATHER WILL PREVAIL
WITH A GRADUAL MODERATION IN TEMPERATURES ON AVERAGE. A BLOCKING
RIDGE IS EXPECTED TO DEVELOP OVER THE WESTERN U.S. NEXT WEEK. THIS
MEANS A CONTINUATION OF MOSTLY DRY WEATHER AND RELATIVELY MILD
TEMPERATURES, AS LONG AS THE RIDGE AXIS/EASTERN U.S. TROUGH
DON'T RETROGRADE FURTHER THAN CURRENT GUIDANCE.
AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/
ISSUED AT 428 AM MST TUE JAN 6 2026
VFR CONDITIONS WILL PREVAIL THROUGH THE TAF PERIOD. CONFIDENCE IN
THE WIND FORECAST IS CONSIDERABLY LOWER THAN NORMAL FOR TODAY. THE
EDGE OF A FAIRLY STEADY-STATE MOUNTAIN WAVE CONTINUES TO SIT RIGHT
NEAR BJC THIS MORNING. WHILE GUIDANCE GENERALLY PULLS THE WINDS A
LITTLE FURTHER WEST THIS MORNING, IT'S LIKELY BJC BOUNCES BETWEEN
A LIGHT VARIABLE/EAST WIND AND 40-50KT GUSTS OUT OF THE WEST
THROUGH AROUND 15Z OR SO. DEN AND APA HAVE BATTLED BETWEEN
DRAINAGE FLOW AND THE OCCASIONAL LIGHT EASTERLY OR SLIGHTLY
STRONGER WESTERLY WIND THIS MORNING AND ARE EXPECTED TO DO THAT
THROUGH MOST OF THE MORNING HOURS.
AS WE GET CLOSER TO 18Z, WINDS SHOULD START TO MIX DOWN INTO THE
WESTERLY FLOW ALOFT. GUIDANCE IS IN A LITTLE BETTER AGREEMENT
GETTING WNW SURFACE WINDS TO ALL OF THE TERMINALS THIS AFTERNOON,
WITH STRONGER SPEEDS LIKELY AT BJC. WE MAY BE SLOW TO TURN BACK TO
DRAINAGE, BUT EVENTUALLY DRAINAGE SHOULD WIN OUT THIS EVENING AND
PERSIST INTO THE FIRST HALF OF WEDNESDAY.
FIRE WEATHER
ISSUED AT 226 AM MST TUE JAN 6 2026
GUIDANCE CONTINUES TO ADVERTISE A CHALLENGING FIRE WEATHER
FORECAST TODAY. WIND GUSTS HAVE DEVELOPED AS ADVERTISED OVERNIGHT,
MAINLY ACROSS THE LOWER FOOTHILLS INTO THE EASTERN PORTIONS OF
BOULDER AND JEFFERSON COUNTIES. WINDS SHOULD BE PRETTY PERSISTENT
THROUGH THE FIRST HALF OF THE DAY, WITH MORE UNCERTAINTY THIS
AFTERNOON AS THE MOUNTAIN WAVE WEAKENS/RETREATS INTO THE HIGHER
ELEVATIONS AND MIXING STARTS TO DEEPEN. RECENT TRENDS DO SUGGEST
THAT GUSTY WINDS (POTENTIALLY 40-50 MPH) WILL PERSIST INTO THE
EARLY AFTERNOON HOURS ACROSS THE LOWER ELEVATIONS OF BOULDER
COUNTY. THAT TREND, COMBINED WITH THE STRONGER (50-60 MPH) GUSTS
THIS MORNING HAS LED TO THE ISSUANCE OF THE RED FLAG WARNING FOR
FZ239, BEGINNING AT 8AM. WHILE THAT MAY BE A TOUCH EARLIER THAN
NEEDED, THE STRONGER WINDS IN THE AM COMBINED WITH QUICKLY
DROPPING RH WAS ENOUGH TO ADJUST THE TIMING... RATHER THAN TRYING
TO GET CUTE WITH THE START OF CRITICAL RH TODAY.
WE ALSO EXPANDED THE RFW INTO THE SOUTHERN FOOTHILLS ZONE (FZ216).
I'M NOT QUITE SOLD ON THE OVERLAP OF STRONGEST WINDS AND LOWEST
RH, BUT RECENT EVENTS IN THE PAST FEW WEEKS HAVE SUGGESTED THAT
GUIDANCE IS NOT NEARLY WINDY ENOUGH AND OFTEN TOO MOIST IN SOME OF
THE TYPICAL WIND PRONE SPOTS IN THAT ZONE (CHEESMAN, BAILEY RAWS
SITES FOR EXAMPLE). OVERNIGHT HUMIDITY RECOVERY HAS BEEN FAIR TO
GOOD THERE (GENERALLY 50-70%), I EXPECT A QUICK DRYING TREND AS
MIXING DEVELOPS LATER THIS MORNING INTO THE AFTERNOON HOURS.
THANKFULLY, THIS LOOKS TO BE THE LAST WINDY DAY BEFORE A COOLER,
MORE UNSETTLED PATTERN DEVELOPS LATER THIS WEEK.
BOU WATCHES/WARNINGS/ADVISORIES
WINTER WEATHER ADVISORY UNTIL 5 AM MST EARLY THIS MORNING FOR
COZ031.
RED FLAG WARNING FROM 8 AM THIS MORNING TO 5 PM MST THIS
AFTERNOON FOR COZ216-239.
UPDATE...HIRIS
DISCUSSION...20
AVIATION...HIRIS
FIRE WEATHER...HIRIS
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