403
FXUS65 KBOU 062125
AFDBOU
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DENVER/BOULDER CO
325 PM MDT TUE MAY 6 2025
KEY MESSAGES
- SPRING STORM CONTINUES TONIGHT INTO TOMORROW. SIGNIFICANT
MOUNTAIN SNOW ACCUMULATIONS, WITH SOME SNOW FALLING AS LOW AS
6,000 TO 6500 FEET.
- RAIN AND SNOW SHOWERS TAPER OFF GRADUALLY WEDNESDAY. A COUPLE OF
THUNDERSTORMS ALSO POSSIBLE OVER THE PLAINS.
- WARMER WEATHER MOVES INTO THE FORECAST AREA ON THURSDAY AND
CONTINUES INTO THE WEEKEND. STILL A FEW LATE DAY SHOWERS AND
STORMS MOST DAYS.
SHORT TERM /THROUGH WEDNESDAY/
ISSUED AT 223 PM MDT TUE MAY 6 2025
TODAY'S WATER VAPOR SATELLITE SHOWS ONE OF THE MORE FASCINATING
UPPER LEVEL PATTERNS ACROSS THE CONUS. A WELL DEFINED UPPER LEVEL
LOW CONTINUES TO SPIN OVER CENTRAL NEW MEXICO THIS AFTERNOON, WITH
A SECONDARY UPPER LOW DIVING INTO SOUTH/CENTRAL NEVADA.
MEANWHILE, A THIRD UPPER LOW CONTINUES TO SPIN OVER THE EASTERN
GREAT LAKES. I'M NOT SURE I CAN REMEMBER A SPRING PATTERN QUITE
LIKE THIS.
AT THE SURFACE, THE WEATHER ACROSS COLORADO IS ALSO EQUALLY
INTERESTING. AN EXPANSIVE PRECIPITATION SHIELD REMAINS ANCHORED
ACROSS THE EASTERN HALF OF THE STATE... WHICH IS UNSURPRISING
GIVEN THE KFTG/KPUX VAD PROFILES (ALONG WITH VARIOUS ACARS/MODEL
SOUNDINGS) CONTINUE TO SHOW AN EXTREMELY DEEP EASTERLY UPSLOPE
REGIME. WHILE THE HEAVIEST PRECIPITATION TODAY HAS GENERALLY FELL
SOUTH OF THE PALMER DIVIDE, THERE HAS BEEN RESPECTABLE SNOWFALL
TOTALS ALREADY OUT OF THE HIGHER TERRAIN (MORE ON THAT IN A
SECOND), ALONG WITH PLENTY OF RAINFALL ACROSS THE I-25 CORRIDOR.
RAINFALL REPORTS FROM RELIABLE MESONET STATIONS ACROSS THE DENVER
METRO HAVE GENERALLY REPORTED 0.4-0.8", WITH OVER AN INCH IN
SPOTS ACROSS THE LOWER FOOTHILLS. SOME CONVECTIVE ELEMENTS HAVE
ALSO EMERGED ON RADAR OVER THE PAST HOUR OR TWO WITH CLOSER TO 250
J/KG OF MUCAPE EAST OF I-25.
ACROSS THE HIGHER ELEVATIONS, SNOW HAS BEEN A LITTLE MORE
IMPRESSIVE, EXCEPT FOR SOUTH PARK WHERE PRECIPITATION HAS
STRUGGLED TO MAKE IT (BLOCKED BY THE TERRAIN IN TELLER COUNTY).
WHILE REPORTS HAVE BEEN SPARSE, WE HAVE RECEIVED RELIABLE REPORTS
OF 5-6" ACROSS BOULDER/GILPIN/NORTHWEST JEFFERSON COUNTIES.
WEBCAMS ALSO CONFIRM THAT SNOW LEVELS DROPPED FAR QUICKER THAN
GUIDANCE (PARTICULARLY NBM) THIS AFTERNOON, LIKELY DUE TO THE
DIABATIC COOLING EFFECTS DURING THE HEAVIER PRECIPITATION EARLIER.
IT'S DIFFICULT TO SAY HOW WELL SNOW WILL STICK BELOW 7,000-7,500
FEET, BUT WE DID GET SNOW MENTIONS IN ACROSS MOST OF THE
FOOTHILLS AND HIGHER PORTIONS OF THE PALMER DIVIDE OVERNIGHT
TONIGHT. IMPACTS ARE FAR FROM CERTAIN, BUT THE CURRENT
WARNINGS/ADVISORIES SEEM TO TELL THE STORY WELL ENOUGH.
WHILE THE ABOVE PARAGRAPHS ARE A FAIRLY GOOD SUMMARY OF TODAY'S
WEATHER, I UNFORTUNATELY CANNOT OFFER AS GOOD OF A FORECAST FOR
TONIGHT INTO TOMORROW. COMPOSITE REFLECTIVITY OVER THE REGION
SHOWS THAT MORE CONSISTENT PRECIPITATION IS DRIFTING WEST-
NORTHWESTWARD INTO OUR CWA, AS THE PRIMARY RAINFALL BAND WITH THIS
UPPER LOW GRADUALLY LIFTS NORTH. THIS SHOULD GET WIDESPREAD
PRECIPITATION BACK INTO THE FORECAST AREA OVER THE NEXT COUPLE OF
HOURS, WITH PERHAPS ANOTHER BURST OR TWO OF HEAVIER SNOW ACROSS
THE FRONT RANGE/FOOTHILLS. GUIDANCE CONTINUES TO BE OF LITTLE
HELP, WITH POOR MODEL-TO-MODEL/RUN-TO-RUN CONSISTENCY TODAY. AT
THIS POINT MOST OF THE FORECAST OVERNIGHT IS BASED ON MY
EXTRAPOLATION OF THE CURRENT RADAR AND GENERAL PATTERN
RECOGNITION, RATHER THAN ANY PARTICULAR DETERMINISTIC/ENSEMBLE
SOLUTION.
THE UPPER LOW SHOULD BEGIN TO SHEAR OUT AND WEAKEN BY WEDNESDAY,
WITH GRADUALLY DECREASING UPSLOPE FLOW. AS TEMPERATURES BEGIN TO
WARM BACK UP INTO THE 50S OR PERHAPS LOW 60S, MODEST INSTABILITY
WILL ALLOW FOR WIDELY SCATTERED SHOWERS AND A FEW THUNDERSTORMS,
THOUGH CONFIDENCE FOR ANY GIVEN LOCATION/TIME IS FAIRLY LOW.
LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/
ISSUED AT 223 PM MDT TUE MAY 6 2025
ANY REMAINING PRECIPITATION SHOULD QUICKLY DIMINISH WEDNESDAY
EVENING AS THE UPPER LOW CONTINUES TO WEAKEN AND DRIFT EASTWARD.
THURSDAY WILL START A TREND TOWARDS WARMER AND GENERALLY DRY
WEATHER ACROSS THE FORECAST AREA, AS A LARGE RIDGE BUILDS ACROSS
THE INTERMOUNTAIN WEST. TEMPERATURES BY THURSDAY AFTERNOON SHOULD
BE CLOSE TO NORMAL VALUES FOR THIS TIME OF YEAR - UPPER 60S TO LOW
70S - WITH ISOLATED TO SCATTERED CONVECTION ACROSS THE HIGHER
ELEVATIONS.
THERE MAY BE A LITTLE MORE COVERAGE TO THE CONVECTION OVER THE
HIGHER ELEVATIONS ON FRIDAY AS WARMER TEMPERATURES LEAD TO A
LITTLE MORE INSTABILITY, ALONG WITH THE NEAR/ABOVE NORMAL MOISTURE
TRAPPED UNDERNEATH THE BUILDING RIDGE.
WARMER WEATHER IS LIKELY THIS WEEKEND INTO EARLY NEXT WEEK AS THE
MID-LEVEL RIDGE CONTINUES TO STRENGTHEN AND THE THERMAL RIDGE AXIS
SHIFTS CLOSER TO THE CWA. HIGHS SHOULD REACH THE MID/UPPER 70S BY
SATURDAY AND THE 80S BY SUNDAY. ADDITIONAL WARMING IS LIKELY INTO
NEXT WEEK, WITH MID 80S POSSIBLE BY MONDAY OR TUESDAY. WITH THE
LOW-LEVEL MOISTURE REMAINING TRAPPED, AT LEAST ISOLATED/SCATTERED
SHOWERS ARE FORECAST EACH AFTERNOON. THE PATTERN TURNS TO A BROAD
SOUTHWESTERLY FLOW ALOFT EVENTUALLY BUT WE'LL SORT THOSE DETAILS
OUT LATER.
AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/
ISSUED AT 1225 PM MDT TUE MAY 6 2025
DIFFICULT FORECAST THROUGH THE TAF PERIOD. STEADIER RAIN HAS
ALREADY PUSHED WEST OF DEN/APA, BUT SCATTERED SHOWERS ARE LIKELY
TO CONTINUE FOR THE NEXT SEVERAL HOURS. A GRADUAL INCREASE IN
COVERAGE IS ALSO LIKELY LATER THIS AFTERNOON AND EVENING, ALONG
WITH A SLIGHT CHANCE OF A THUNDERSTORM. CEILINGS WILL LIKELY
BOUNCE BETWEEN IFR TO AS HIGH AS VFR/ILS AT TIMES THROUGH MOST OF
TODAY, WITH EASTERLY WINDS DIMINISHING.
FORECAST CERTAINTY DOESN'T INCREASE TONIGHT INTO WEDNESDAY.
SURFACE WINDS WILL CONTINUE TO DIMINISH, BUT MID-LEVEL UPSLOPE
WILL ALLOW FOR AT LEAST SCATTERED SHOWERS TO CONTINUE INTO
WEDNESDAY MORNING. CEILINGS ARE LIKELY TO LOWER OVERNIGHT, WITH
SOME FOG/MIST ALSO POSSIBLE TOWARDS 12Z WEDNESDAY. CEILINGS WILL
AGAIN SLOWLY RISE TOMORROW AFTERNOON, WITH ADDITIONAL SCATTERED
SHRA/TS POSSIBLE BY LATE MORNING OR EARLY AFTERNOON.
BOU WATCHES/WARNINGS/ADVISORIES
WINTER STORM WARNING UNTIL 6 AM MDT WEDNESDAY FOR COZ033-034.
WINTER WEATHER ADVISORY UNTIL 6 AM MDT WEDNESDAY FOR COZ035>037.
SHORT TERM...HIRIS
LONG TERM...HIRIS
AVIATION...HIRIS
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