050
FXUS65 KBOU 070858
AFDBOU
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DENVER/BOULDER CO
258 AM MDT WED MAY 7 2025
KEY MESSAGES
- SPRING STORM SLOWLY WINDING DOWN, BUT STILL A FAIRLY ACTIVE
WEATHER DAY TODAY WITH ADDITIONAL SNOW SHOWERS IN THE FOOTHILLS
AND MOUNTAINS, AND RAIN/THUNDERSTORMS ON 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.
UPDATE
ISSUED AT 258 AM MDT WED MAY 7 2025
NUMEROUS SHOWERS CONTINUE ROTATING WESTWARD AROUND THE UPPER LOW,
IN LINE WITH A DECENT 20 KT UPSLOPE COMPONENT. THAT UPSLOPE
SLOWLY WEAKENS THIS MORNING AS THE UPPER LOW ELONGATES EVEN
FURTHER ACROSS THE CENTRAL/SOUTHERN PLAINS INTO MISSOURI AND
ILLINOIS. THAT WILL LIKELY BRING A TEMPORARY DECREASE IN SHOWER
INTENSITY AND COVERAGE, AND ALLOW THE MOUNTAIN/FOOTHILL SNOW EVENT
TO WIND DOWN. WE THINK THE HEAVIEST SHOULD BE OVER AROUND 6-7 AM,
BUT WILL MONITOR THE LATEST TRENDS AND ROAD CONDITIONS (MAINLY
SLUSH DURING THE HEAVIEST SHOWERS AND OVER THE HIGHEST PASSES)
BEFORE ALLOWING THE WINTER HIGHLIGHTS TO EXPIRE ON TIME AT 6 AM.
FOR LATER THIS MORNING AND AFTERNOON, THE ATMOSPHERIC PROFILES
ARE STILL QUITE MOIST AND NEUTRAL (TEMPERATURE PROFILES RIGHT UP
THE MOIST ADIABAT), SO ANY SORT OF DAYTIME HEATING WILL SUPPORT A
QUICK REDEVELOPMENT OF CONVECTIVE SHOWERS AND EVEN SCATTERED
THUNDERSTORMS WITH MLCAPE NEAR 200 J/KG. ADDITIONAL PRECIPITATION
IS LIKELY TO REACH 0.20 TO 0.40 INCH ON AVERAGE OVER MOST OF THE
AREA, ALTHOUGH ONCE AGAIN THE FAR EASTERN PLAINS AND AREAS WEST OF
THE FRONT RANGE ARE SHAPING UP TO SEE LESSER AMOUNTS. DESPITE THE
RELATIVELY COOL TEMPERATURES, THESE WILL BE FAIRLY EFFICIENT RAIN
PRODUCERS WITH WARM CLOUD DEPTH NEAR 2500-3000 FT - NOT BAD FOR
EARLY MAY. THUS, ANY OF THE HEAVIER SHOWERS WILL BE CAPABLE OF
PRODUCING A QUICK QUARTER INCH OF RAIN IN LESS THAN AN HOUR, AND
LOCALLY HIGHER ADDITIONAL AMOUNTS THAN AFOREMENTIONED.
THOSE CONVECTIVE SHOWERS AND STORMS WILL WIND DOWN THIS EVENING AS
WE SLOWLY STABILIZE. THE LOSS OF UPSLOPE WILL ALSO MEAN DRYING
CONDITIONS WITH GRADUAL CLEARING OVERNIGHT. THERE SHOULD BE ENOUGH
RESIDUAL MOISTURE TO PREVENT A FROST IN THE LOWER ELEVATIONS
OUTSIDE OF A COUPLE OF OUR COLDEST SPOTS. THAT MOISTURE COULD LEAD
TO SOME PATCHY FOG IN A COUPLE VALLEYS, BUT NO WIDESPREAD FOG
THREAT EXPECTED WITH LIGHT DOWNSLOPE WINDS DEVELOPING.
PREVIOUS DISCUSSIONS / THROUGH TUESDAY/
UPDATE ISSUED AT 920 PM MDT TUE MAY 6 2025
WE HAD A TEMPORARY REPRIEVE AS A PATCH OF DRY AIR ROTATED AROUND
THE LOW ACROSS THE FRONT RANGE OVER THE LAST SEVERAL HOURS. THIS
IS PASSING NOW, AND THE MAIN PRECIPITATION BAND IS LIFTING NORTH.
THERE'S STILL A VERY SHALLOW LAYER OF WESTERLY WINDS, BUT THE DEEP
FLOW ABOVE THAT IS ROTATING A BIT MORE ENE NOW. OVERNIGHT THE
DEEPER FLOW WILL BECOME MORE NORTHEAST, WITH THE LOW LEVEL FLOW
LIKELY BECOMING MORE NORTHERLY TOWARDS MORNING. PRECIPITATION
TRENDS SHOULD BE MAINLY DEPENDENT ON THE LARGER SCALE QG FORCING
AS THAT BAND LIFTS NORTH OVER THE NEXT FEW HOURS BEFORE STARTING
TO SHIFT EAST AND DIMINISH. WE SHOULD SEE A RESURGENCE OF RAIN IN
DENVER THAT'S STARTING TO HAPPEN NOW, AND MORE MODERATE TO HEAVY
SNOW IN THE FOOTHILLS UP TO BOULDER COUNTY. NOT SURE HOW MUCH THIS
WILL ALL PUSH NORTH INTO WELD AND LARIMER COUNTIES, BUT THERE WILL
BE SOME NORTHWARD PUSH. WHATEVER IS HAPPENING THERE WILL LIKELY BE
SHRUNK BY THE USUAL DEVELOPING NORTHERLY LOW LEVEL WINDS AROUND
SUNRISE.
WE'RE DROPPING THE WINTER WEATHER ADVISORY FOR SOUTH PARK AS THERE
JUST HASN'T BEEN THAT MUCH SNOW IN THE VALLEY. THE EASTERLY FLOW
HIT THE MOUNTAINS UP TO KENOSHA PASS, BUT THE MOISTURE/LIFT AT
HIGHER LEVELS THAT MADE IT PAST THOSE MOUNTAINS WASN'T THAT
STRONG. ANOTHER INCH OR TWO WILL FALL THERE, BUT IMPACTS LOOK
MINIMAL SO FAR. ELSEWHERE ROAD CONDITIONS STILL APPEAR TO BE TIED
TO THE SNOWFALL RATE, WITH WET ROADS OUTSIDE OF THE HEAVY SNOW
AREAS.
*****
ISSUED AT 223 PM MDT TUE MAY 6 2025
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.
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 /06Z TAFS THROUGH 06Z THURSDAY/
ISSUED AT 1145 PM MDT TUE MAY 6 2025
OCCASIONAL RAIN SHOWERS WILL CONTINUE THROUGH MUCH OF WEDNESDAY,
BUT FORECASTING CEILINGS AND TO SOME EXTENT VISIBILITY WILL
REMAIN THE LARGEST CONCERNS. WE'RE STARTING WITH CEILINGS MOSTLY
JUST ABOVE MVFR, BUT WITH ADDITIONAL SHOWERS AND ESPECIALLY A
SLIGHT TURN IN WINDS TO THE NNW THROUGH 09Z, WE EXPECT LOWER
CEILINGS TO REFORM WITH IFR/MVFR CONDITIONS DEVELOPING AND
BECOMING WIDESPREAD THROUGH 15Z. THERE IS SOME THREAT OF FOG BUT
WITH THE PRESENT STRATUS DECK WE THINK MOST VISIBILITY
RESTRICTION WILL BE DUE TO LIGHT RAIN, OCCASIONALLY REDUCING IT TO
4-5SM. CEILINGS SHOULD START TO LIFT WITH DIURNAL HEATING
15Z-18Z, BUT STILL REMAIN MVFR. THERE WILL ALSO BE A GREATER THAN
50% CHANCE OF THUNDERSTORMS DUE TO THE MOIST BUT SLIGHTLY UNSTABLE
AIRMASS ON WEDNESDAY, AND MLCAPE NEAR 200 J/KG AND VIRTUALLY NO
CAP AS SOON AS WE START TO WARM. THUS, WE'LL HAVE TEMPO -TSRA IN
THE 19Z-23Z PERIOD, BUT COULD START AS EARLY AS 18Z OR SO.
OVERALL, LIGHT NORTH TO NORTHWEST WINDS SHOULD PERSIST THROUGH
ABOUT 03Z, THEN LIGHT DRAINAGE WINDS, LESS SHOWERS, AND GRADUALLY
RISING CEILINGS EXPECTED BY 03Z-05Z THURSDAY.
BOU WATCHES/WARNINGS/ADVISORIES
WINTER STORM WARNING UNTIL 6 AM MDT EARLY THIS MORNING FOR
COZ033-034.
WINTER WEATHER ADVISORY UNTIL 6 AM MDT EARLY THIS MORNING FOR
COZ035-036.
UPDATE...BARJENBRUCH
SHORT TERM...HIRIS
LONG TERM...HIRIS
AVIATION...BARJENBRUCH
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