479
FXUS65 KBOU 250250
AFDBOU
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DENVER/BOULDER CO
750 PM MST FRI JAN 24 2025
KEY MESSAGES
- SNOW BECOMING WIDESPREAD ALONG AND NORTH OF I-70 TONIGHT, MAINLY
LIGHT BUT WITH SOME TRAVEL IMPACTS MOUNTAINS AND EAST TO I-25
CORRIDOR.
- DRY WEATHER EXPECTED EARLY NEXT WEEK WITH MODERATING TEMPERATURES.
- STILL WATCHING THE POTENTIAL RETURN OF SNOW (20-30% CHANCE)
TOWARD THE MIDDLE OF NEXT WEEK. CONFIDENCE REMAINS LOW.
UPDATE
ISSUED AT 739 PM MST FRI JAN 24 2025
LIFT ASSOCIATED WITH A JET STREAK AND A LITTLE OVERRUNNING OF THE
WEAK FRONTAL BOUNDARY OVER NORTHEASTERN COLORADO OVERPERFORMED
EARLY THIS EVENING AND THERE IS LIGHT SNOW ACROSS MUCH OF
NORTHEASTERN COLORADO. MOUNTAIN AREAS ALONG AND NORTH OF I-70 HAVE
ALSO DEVELOPED WIDESPREAD LIGHT SNOW. AT LOWER ELEVATIONS IT'S NOT
MUCH YET, AND THERE WILL LIKELY BE A DECREASE BEHIND THE EXITING
JET STREAK BEFORE LIFT FROM THE NEXT JET STREAK INCREASES LATER
TONIGHT AND THEN DEEPER WARM ADVECTION/DEFORMATION RELATED LIFT
BRINGS A FURTHER INCREASE IN SNOW BY SATURDAY MORNING. MAIN CHANGE
TO THE FORECAST AT THIS HOUR WAS ADJUSTMENTS FOR THE CURRENT SNOW,
BUT POPS HAVE BEEN INCREASED OVERALL WITH A LITTLE NUDGE UPWARD IN
AMOUNTS. WE'LL NEED TO WATCH FORT COLLINS FOR A POTENTIAL ADVISORY
DEPENDING ON HOW MUCH JET RELATED LIFT THERE IS AND HOW SLOWLY THE
WHOLE PATTERN LIFTS NORTHWARD LATER SATURDAY. THE JET FORCING AND
LOW LEVEL WINDS GOING MORE SOUTHEASTERLY COULD FAVOR ACCUMULATING
SNOW CONTINUING MUCH LONGER UP THERE.
SHORT TERM /THROUGH SATURDAY/
ISSUED AT 224 PM MST FRI JAN 24 2025
IN NEWS THAT SHOCKS ABSOLUTELY NO ONE, OUR INCOMING SYSTEM IS TRYING
TO KICK THINGS OFF SLIGHTLY AHEAD OF SCHEDULE, WITH SNOW SHOWERS
ALREADY HUGGING THE HIGHER ELEVATIONS ALONG THE CONTINENTAL DIVIDE,
AND EVEN SOME HIGH-BASED SHOWERS ATTEMPTING TO FORM IN OUR NORTHEAST
PLAINS, WITH HEALTHY MID AND UPPER-LEVEL WATER VAPOR EVIDENT ON
SATELLITE.
AS WE FAST-FORWARD INTO THIS EVENING AND OVERNIGHT, A 100-120 KT JET
TO OUR NORTHEAST WILL BOOST LIFT UNDER ITS RIGHT ENTRANCE REGION,
WITH MODERATE FRONTOGENESIS DEVELOPING ACROSS OUR NORTHERN TIER OF
COUNTIES. THIS WILL LEAD TO A STEADY INCREASE IN SNOW SHOWER
COVERAGE IN THE NORTHERN MOUNTAINS/FOOTHILLS, AND IN THE VICINITY OF
THE CHEYENNE RIDGE TO START.
BY AROUND 2 OR 3AM, EASTERLY UPSLOPE WINDS OF AROUND 10 KTS LOOK TO
DEEPEN TO JUST SHY OF THE 700MB LEVEL FOR THE URBAN CORRIDOR, BY
WHICH TIME SNOW SHOULD BEGIN TO FILL IN. NEARING SUNRISE, FORECAST
SOUNDINGS INDICATE THE DGZ WILL EXPAND TO A DEPTH OF ABOUT 6,000-
7,000 FT FEET, AND THIS SHOULD CONTRIBUTE TO HEALTHY SNOW RATIOS
NEAR OR UPWARDS OF ~18:1 IN COMBINATION WITH SOME WEAK QG ASCENT AND
RATHER PROLONGED JET-INDUCED LIFT. THUS, WE STILL EXPECT THE BULK OF
OUR I-25 CORRIDOR AND FOOTHILL ACCUMULATIONS TO OCCUR FROM EARLY
SATURDAY MORNING (A FEW HOURS PRIOR TO SUNRISE) THROUGH EARLY
AFTERNOON. SNOWFALL INTENSITY WILL TAPER OFF CONSIDERABLY FOR ALL
AREAS LATER IN THE AFTERNOON AS DRIER AIR BEGINS TO INTRUDE AT MID-
LEVELS AND WE SEE A GRADUAL WEAKENING IN THE UPSLOPE FLOW.
THE SPATIAL PATTERN OF ACCUMULATIONS MAKES FOR TRICKY HEADLINE
DETERMINATIONS IN SEVERAL AREAS, NAMELY FOR URBAN CORRIDOR ZONES AND
THE I-70 MOUNTAIN CORRIDOR WHERE WE EXPECT STEEP GRADIENTS IN
SNOWFALL. AT THIS POINT, WE HAVE ENOUGH CONFIDENCE IN A MAJORITY OF
ZONE 039 (EASTERN BOULDER COUNTY, NORTHERN JEFFERSON COUNTY) MEETING
ADVISORY CRITERIA TO INCLUDE IN OUR HIGHLIGHTS, WITH 3-7" LIKELY FOR
MOST. AMOUNTS WILL TAPER OFF CONSIDERABLY CLOSER TO I-25, INCLUDING
THE DENVER METRO (1-3" RANGE EXPECTED). SIMILARLY, WE EXPECT GREATER
IMPACTS ROUGHLY NORTH OF THE EISENHOWER TUNNEL, BUT MUCH MORE MINOR
ACCUMULATIONS INTO SUMMIT COUNTY. STILL, TRAVELERS VENTURING INTO
THE MOUNTAINS ALONG I-70 SHOULD EXPECT LOCALLY DIFFICULT ROAD
CONDITIONS. LASTLY, ADVISORIES HAVE ALSO BEEN EXPANDED INTO NORTH
AND MIDDLE PARKS WHERE FAVORED AREAS SHOULD EXCEED 5".
WHILE NOT AS FEROCIOUS AS WITH THE RECENT ARCTIC SYSTEM,
TEMPERATURES WILL STILL BE QUITE COLD REGION-WIDE, WITH HIGH
TEMPERATURES ON SATURDAY THAT WILL REMAIN IN THE UPPER TEENS TO LOW
20'S BOTH FOR THE LOWER ELEVATIONS AND MOST MOUNTAIN COMMUNITIES.
LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/
ISSUED AT 224 PM MST FRI JAN 24 2025
LINGERING LIGHT SNOW AND FLURRIES WILL TAPER OFF AND COME TO AN END
IN MOST AREAS OVERNIGHT AS WE LOSE ALL OF OUR FORCING MECHANISMS
(UPSLOPE FLOW, F-GEN, RIGHT REAR ENTRANCE REGION OF JET, AND WEAK
QG). THE LAST PLACE THAT WILL SEE THE SNOW END WILL BE IN THE
MOUNTAINS, AND THAT MAY LINGER UNTIL EARLY SUNDAY MORNING WITH
OROGRAPHICS STILL PLAYING A ROLE THERE. EVENTUALLY, DRIER AIR AND
SUBSIDENCE WILL WIN OUT, WITH SOME SUNSHINE RETURNING DURING THE DAY
AMIDST LINGERING FLURRIES. TEMPERATURES WILL STILL BE WELL BELOW
NORMAL, WITH EVEN PLAINS LOCATIONS STRUGGLING TO GET OUT OF THE 20S.
FOR SUNDAY NIGHT THROUGH MONDAY, WE'LL STAY UNDERNEATH A COL, OR
SEPARATION OF FLOW BETWEEN THE SPLITTING UPPER LEVEL LOW DROPPING
DOWN THE CALIFORNIA COASTLINE AND THE POLAR JET DRIVING SOUTHEAST
THROUGH CENTRAL CANADA. THIS WOULD BRING DRY CONDITIONS, LIGHT
WINDS, AND TEMPERATURES RETURNING CLOSER TO NORMAL. IT APPEARS
SIMILAR CONDITIONS WILL PERSIST INTO TUESDAY AND POSSIBLY THROUGH
WEDNESDAY WITH THE UPPER LOW DRIFTING AIMLESSLY THROUGH THE DESERT
SOUTHWEST.
EVENTUALLY, THIS UPPER LOW WILL NEED TO BE WATCHED AS THERE ARE MORE
SIGNS IT WILL BE TAPPING INTO GULF MOISTURE AND INTENSIFYING.
THE MAIN QUESTION SURROUNDS THE TRACK OF THIS SYSTEM LATER NEXT
WEEK, AS IT HAS POTENTIAL TO PRODUCE SOME HEALTHY SNOWFALL AMOUNTS
(>6 INCHES) IN THE NORTHERN COLD SECTOR. THIS IS SHOWN NICELY IN
THE VARIOUS ENSEMBLE OUTPUTS; ABOUT 15% SHOW A MORE SIGNIFICANT
SNOW PUSHING AS FAR NORTH AS DENVER, 20-30% CHANCE TOWARD LIMON,
BUT THE MAJORITY STILL KEEP IT FARTHER SOUTH AND IMPACTING THE
SOUTHERN HIGH PLAINS INTO KANSAS. WE'LL BE KEEPING ON EYE ON THIS
ONE, BUT IT'LL PROBABLY BE A COUPLE MORE DAYS TO GET A BETTER
HANDLE ON THE TRACK - LIKELY TOWARD SUNDAY OR SUNDAY NIGHT WHEN WE
FIND OUT HOW FAR SOUTH THE UPPER LOW DROPS ALONG THE CALIFORNIA
COAST.
AVIATION /00Z TAFS THROUGH 00Z SUNDAY/
ISSUED AT 739 PM MST FRI JAN 24 2025
LOWER CEILINGS WILL DEVELOP IN THE DENVER AREA WITH LIGHT SNOW
DEVELOPING BETWEEN 05Z AND 08Z. MVFR CONDITIONS WITH AREAS OF IFR
CAN BE EXPECTED FROM THAT TIME THROUGH AT LEAST 21Z SATURDAY, AND
INSTRUMENT APPROACHES TO KDEN WILL BE NEEDED INTO SATURDAY
EVENING. ACCUMULATIONS OF 1 TO 3 INCHES OF SNOW ARE EXPECTED AT
KDEN/KAPA AND 3 TO 6 INCHES AT KBJC.
BOU WATCHES/WARNINGS/ADVISORIES
WINTER WEATHER ADVISORY UNTIL MIDNIGHT MST SATURDAY NIGHT FOR
COZ030-032-035.
WINTER WEATHER ADVISORY UNTIL 5 AM MST SUNDAY FOR COZ031-033.
WINTER WEATHER ADVISORY FROM 1 AM SATURDAY TO MIDNIGHT MST
SATURDAY NIGHT FOR COZ039.
UPDATE...GIMMESTAD
SHORT TERM...RODRIGUEZ
LONG TERM...BARJENBRUCH
AVIATION...GIMMESTAD
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