882
FXUS65 KBOU 180610
AFDBOU
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DENVER/BOULDER CO
1210 AM MDT FRI APR 18 2025
KEY MESSAGES
- PERIOD OF HEAVIER BANDED SNOWFALL POSSIBLE LATE TONIGHT THROUGH
MID MORNING ON FRIDAY ACROSS PORTIONS OF THE I-25 CORRIDOR FROM
DENVER TO FORT COLLINS. THIS MAY AFFECT THE MORNING COMMUTE IN
SOME AREAS. CONFIDENCE LEVEL IS AT 50%.
- MODERATE SNOW TONIGHT THROUGH SAT AM WILL CREATE HAZARDOUS
MOUNTAIN AND FOOTHILL TRAVEL. ADDITIONAL ACCUMULATIONS FOR THE
URBAN CORRIDOR FRIDAY AFTERNOON AND EVENING, WITH MINOR TRAVEL
IMPACTS FRIDAY EVENING.
- COLDER FRIDAY INTO SATURDAY, WITH STEADY WARMING SUNDAY INTO
NEXT WEEK.
UPDATE
ISSUED AT 823 PM MDT THU APR 17 2025
AM GETTING SOME WHAT CONCERNED THAT A BAND OF HEAVIER SNOW MAY
AFFECT PORTIONS OF THE I-25 CORRIDOR LATE TONIGHT THRU MID MORNING
FRI. BEST WINDOW APPEARS TO FROM 09Z-15Z WHICH WOULD BE JUST IN
TIME TO AFFECT THE MORNING COMMUTE. ALTHOUGH ROAD TEMPERATURES ARE
RATHER WARM CURRENTLY, TEMPERATURES WILL DROP INTO THE MID TO
UPPER 20S BY 12Z. THIS COMBINED WITH POTENTIAL FOR HEAVIER SNOW
COULD LEAD TO SOME IMPACTS FOR THE MORNING RUSH HOUR.
OVERALL, CROSS-SECTIONS SHOW FAVORABLE INSTABILITY COMBINED WITH
THE POSITION OF UPPER LEVEL JET, MAY LEAD TO A PERIOD OF BANDED
HEAVIER SNOWFALL AS DESCRIBED ABOVE. NOT EXACTLY SURE WHERE ALL OF
THIS MAY SET UP AND CONFIDENCE, ALTHOUGH INCREASING, IS STILL
AROUND 50 PERCENT. IF I HAD TO GUESS, THE HEAVIEST SNOW WOULD
PROBABLY STAY MAINLY ALONG AND WEST OF I-25 FROM DENVER TO FORT
COLLINS.
SINCE CONFIDENCE IS ONLY AROUND 50 PERCENT, WILL HOLD OFF ON ISSUING
AN ADVISORY FOR LATE TONIGHT THRU FRI MORNING BUT OVERNIGHT SHIFT
MAY HAVE TO CONSIDER ONE.
SHORT TERM /THROUGH FRIDAY/
ISSUED AT 236 PM MDT THU APR 17 2025
IT'S A BATTLE OF AIRMASSES TODAY AS THE SOUTHERN HALF OF OUR
FORECAST AREA REMAINS UNDER DRY DOWNSLOPE FLOW, SUSTAINING CRITICAL
FIRE WEATHER CONDITIONS ROUGHLY ALONG AND SOUTH OF I-70 THROUGH LATE
AFTERNOON OR EARLY EVENING. MEANWHILE, THE NORTHERN PLAINS REMAIN
COOLER AFTER THE PASSAGE OF A FIRST, WEAKER FRONTAL BOUNDARY AND
PREVAILING NORTHEASTERLY FLOW. MOISTURE ALONG THE LEADING EDGE OF
THE APPROACHING UPPER-LEVEL TROUGH WILL STEADILY INCREASE THROUGH
THE DAY, AND HAS BEEN PRODUCING A FEW SHOWERS IN OUR NORTHERN
MOUNTAINS.
HOWEVER, THE BULK OF OUR INITIAL ROUND OF MOISTURE WON'T ARRIVE
UNTIL LATER THIS EVENING AND OVERNIGHT, FOLLOWING THE MORE ROBUST
FRONT THAT WILL PUSH NORTH TO SOUTH LATE AFTERNOON INTO EARLY
EVENING. GUSTS TO AROUND 45 MPH CAN BE EXPECTED WITH THE FRONTAL
BOUNDARY, TAPERING OFF TO A LINGERING BREEZE AFTER ONE OR TWO HOURS.
THERE'S MARGINAL INSTABILITY WITH THE FRONT, AS EVIDENCED BY THE
SHALLOW CONVECTION AND ISOLATED LIGHTNING CURRENTLY OBSERVED
UPSTREAM, SO WE'RE MAINTAINING A CHANCE OF THUNDER IN THE FORECAST
FOR LATER TODAY.
EAST OF THE MOUNTAINS, IT WILL TAKE SOME TIME FOR MOISTURE TO DEEPEN
SUFFICIENTLY FOR MORE PERSISTENT PRECIPITATION TO DEVELOP, WITH THIS
HOLDING OFF UNTIL LATE EVENING AS BANDED PRECIPITATION EXPANDS
EASTWARD. A BRIEF WINTRY MIX WILL PRECEDE THE TRANSITION TO SNOW
(EXPECTED GENERALLY AFTER MIDNIGHT), AND EVEN SOME PATCHY AND BRIEF
FREEZING DRIZZLE CAN'T BE RULED OUT, MAINLY EAST OF I-25 ON THE
FRONT END OF THE PRECIPITATION. SNOW WILL THEN INCREASE IN COVERAGE
STEADILY THROUGH SUNRISE FRIDAY, WITH THE HEAVIER ACCUMULATIONS
FAVORING AREAS NORTH OF I-70 (MOUNTAINS) AND I-76 (PLAINS). SNOWFALL
INTENSITY WILL REMAIN ON THE LIGHTER SIDE DURING THE FIRST HALF OF
THIS SYSTEM. BY THE AFTERNOON, LOW-LEVEL FLOW WILL TURN MORE
EASTERLY OVER THE FOOTHILLS AND URBAN CORRIDOR, AND SOUTHERLY FOR
PARK COUNTY, BOOSTING THE UPSLOPE COMPONENT. WITH A MODEST INCREASE
IN LAPSE RATES TO BOOT, MODERATE SNOWFALL WILL FILL IN ACROSS THE
FOOTHILLS, MOUNTAINS AND SOUTH PARK, AS WELL AS ADJACENT LOWER
ELEVATIONS. DAYTIME SNOW ACCUMULATIONS FOR THE PLAINS AND URBAN
CORRIDOR WILL LARGELY STAY CONFINED TO COLDER SURFACES LIKE GRASS,
WITH PRIMARILY WET OR OCCASIONALLY SLUSHY ROADS, ALTHOUGH
TEMPERATURES SHOULD BE COLD ENOUGH BY FRIDAY EVENING TO SUPPORT MORE
WIDESPREAD (ALBEIT LARGELY MINOR) ACCUMULATIONS ON ROADS. AS IS
TYPICAL FOR APRIL STORMS, THE SNOW WILL BE ON THE WETTER/HEAVIER
SIDE, AND COULD LEAD TO DAMAGE TO VEGETATION, WITH TRAVEL IMPACTS
GENERALLY CONFINED TO THE FOOTHILLS AND HIGHER MOUNTAIN/VALLEY
ELEVATIONS.
LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/
ISSUED AT 236 PM MDT THU APR 17 2025
FRIDAY NIGHT, A POSITIVELY TILTED UPPER LEVEL TROUGH WILL STRETCH
FROM ONTARIO CANADA INTO THE SOUTHWESTERN STATES. THIS TROUGH WILL
BE SPLIT WITH THE STRONGEST PIECE OF ENERGY OVER NORTHERN
ARIZONA/SOUTHERN UTAH. MOIST UPSLOPE FLOW EAST OF THE MOUNTAINS
COMBINED WITH QG LIFT, ASSOCIATED WITH AN UPPER LEVEL SHORTWAVE,
SHOULD RESULT IN CONTINUED SNOW ACROSS MUCH OF THE FORECAST AREA
THROUGH SATURDAY MORNING. THE SNOW SHOULD BE LIGHT ACROSS THE PLAINS
WITH LITTLE IMPACT ANTICIPATED. THE MOUNTAINS AND FOOTHILLS COULD
SEE PERIODS OF MODERATE SNOW WITH ADDITIONAL ACCUMULATION EXPECTED
WHICH COULD IMPACT TRAVEL. THEREFORE, THE WINTER WEATHER ADVISORY
WHICH IS IN EFFECT FOR THESE AREAS STILL LOOKS ON TRACK AND ADDED
THE NORTHERN SLOPES OF THE PALMER DIVIDE FOR LATE FRI PM THROUGH
SAT AM. THE SNOW SHOULD WIND DOWN SATURDAY AFTERNOON WITH A
COUPLE INCHES OF ADDITIONAL ACCUMULATION POSSIBLE ACROSS THE HIGH
COUNTRY.
WARMER AND DRIER WEATHER IS EXPECTED ON SUNDAY AS UPPER LEVEL HIGH
PRESSURE BUILDS OVER THE ROCKY MOUNTAIN REGION. HOWEVER, THERE MAY
BE ENOUGH LINGERING MID LEVEL MOISTURE COMBINED WITH OROGRAPHIC LIFT
TO PRODUCE SCATTERED SNOW SHOWERS OVER THE MOUNTAINS.
EARLY NEXT WEEK, A ZONAL FLOW ALOFT WILL SET UP OVER THE STATE WHICH
SHOULD LEAD TO MILD AND DRY CONDITIONS ACROSS THE REGION. THE
EXCEPTION MAY BE A FEW LIGHT RAIN AND SNOW SHOWERS POSSIBLE ACROSS
THE HIGH COUNTRY.
BY MID WEEK, THE UPPER FLOW TURNS SOUTHWESTERLY IN RESPONSE TO UPPER
LEVEL TROUGHING OVER THE WESTERN STATES. MILD TEMPERATURES ARE
EXPECTED TO CONTINUE WITH HIGHS TEMPERATURES ON THE PLAINS CLIMBING
INTO THE UPPER 60S AND LOWER 70S. THERE MAY BE ENOUGH MID LEVEL
MOISTURE, COMBINED WITH SOME INSTABILITY, TO PRODUCE ISOLATED TO
SCATTERED AFTERNOON SHOWERS AND STORMS ACROSS THE FORECAST AREA.
AVIATION /06Z TAFS THROUGH 06Z SATURDAY/
ISSUED AT 1208 AM MDT FRI APR 18 2025
WE ARE IN THE THRALLS OF THIS LATEST STORM. CONDITIONS AT DIA
SHOULD REMAIN FAIRLY STEADY STATE FOR SEVERAL HOURS WITH NORTH
AND NORTHEASTERLY UPSLOPE FLOW, A PRETTY LOW STRATUS CLOUD DECK
AND LIGHT SNOW. WILL KEEP CEILINGS IN THE BKN-OVC005-015 RANGE.
WILL GET THE VISIBILITIES INTO THE 1-4SM -SN BR RANGE AFTER 08Z OR
09Z AND KEEP THEM THAT WAY FOR SEVERAL HOURS.
BOU WATCHES/WARNINGS/ADVISORIES
WINTER WEATHER ADVISORY UNTIL 6 AM MDT SATURDAY FOR COZ031-033-
034.
WINTER WEATHER ADVISORY FROM 4 AM EARLY THIS MORNING TO 6 AM MDT
SATURDAY FOR COZ035-036.
WINTER WEATHER ADVISORY FROM 9 AM THIS MORNING TO 6 AM MDT
SATURDAY FOR COZ037.
WINTER WEATHER ADVISORY FROM 3 PM THIS AFTERNOON TO NOON MDT
SATURDAY FOR COZ041.
UPDATE...RPK
SHORT TERM...099
LONG TERM...099
AVIATION...RJK
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