511
FXUS65 KBOU 190607
AFDBOU
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DENVER/BOULDER CO
1207 AM MDT SAT OCT 19 2024
KEY MESSAGES
- LIGHT PRECIPITATION IS POSSIBLE FROM THIS EVENING INTO SATURDAY
MORNING, WITH SNOW IN THE HIGHER MOUNTAINS AND RAIN BELOW 9,000
FT. THE HIGHEST SNOW AMOUNTS THROUGH SUNDAY WILL BE ALONG AND
SOUTH OF I-70, ESPECIALLY THE MOSQUITO RANGE.
- RAIN AND SNOW CHANCES DECREASE ON SATURDAY (20-40%) MAINLY ALONG
AND SOUTH OF I-70, WITH THE BEST CHANCES OF MEASURABLE
PRECIPITATION REMAINING SOUTH OF I-70.
- SCATTERED TO LIKELY PRECIPITATION IS EXPECTED SUNDAY AFTERNOON
INTO MONDAY MORNING, WITH THE SNOW LEVEL AROUND 9,500 TO 10,000
FEET.
- TRAVEL MAY BE IMPACTED ACROSS THE HIGHEST MOUNTAIN PASSES
TONIGHT THROUGH SATURDAY MORNING, MAINLY FROM I-70 SOUTH ABOVE
10,000 FT AND AGAIN SUNDAY NIGHT FOR ALL OUR MOUNTAINS.
- DRY AND WARMER FOR ALL THE FORECAST AREA MONDAY AFTERNOON
THROUGH FRIDAY.
UPDATE
ISSUED AT 845 PM MDT FRI OCT 18 2024
THE FIRST MAIN AREA OF RAIN HAS MOVED PAST DENVER ONTO THE
NORTHEAST PLAINS. SCATTERED SHOWERS ARE OCCURRING BEHIND IT,
ENHANCED BY MOIST LOW LEVELS WITH WEAK UPSLOPE WINDS INTO THE
DENVER AREA, AND SOME WEAK INSTABILITY OVER THE CENTRAL MOUNTAINS
ALONG WITH UPSLOPE INTO PARK COUNTY. ANOTHER ENHANCED AREA OF
SHOWERS AND THUNDERSTORMS IS MOVING INTO COLORADO PAST TRINIDAD
AND LA JUNTA. MOST OF THIS WILL PASS EAST OF DENVER, BUT IT WILL
GIVE ANOTHER GOOD ROUND OF SHOWERS TO THE PLAINS FURTHER EAST
LATER TONIGHT. ELSEWHERE THE SCATTERED SHOWERS WILL CONTINUE, WITH
DRIER AIR OVER NORTHERN BORDER AREAS.
IT LOOKS LIKE THERE'S BEEN A COUPLE INCHES OF WET SNOW, WITH SWES
OF 0.2 TO 0.4, ALONG THE NORTHERN EDGE OF PARK COUNTY, WITH
LIGHTER AMOUNTS ELSEWHERE. WITH THE CURRENT PATTERN CONTINUING
OVER NIGHT, THERE MAY BE SIMILAR ADDITIONAL AMOUNTS THROUGH THE
REST OF THE NIGHT.
ONLY MINOR FORECAST CHANGES AT THIS TIME FOR SHOWER LOCATION AND
TIMING.
SHORT TERM /THROUGH SATURDAY/
ISSUED AT 111 PM MDT FRI OCT 18 2024
GOES-16 WATER VAPOR SHOWS THE CUT OFF LOW HAS SLOWED
SIGNIFICANTLY, BUT UNFORTUNATELY FOR OUR AREA IF YOU WANT A
DECENT PRECIPITATION EVENT, IT CONTINUES TO MOVE DUE SOUTH, MOVING
INTO CENTRAL ARIZONA WHICH CONTINUES THE TREND OF MOVING SLOWER
AND FURTHER SOUTH. THE RESULT IS THAT PRECIPITATION CHANCES ARE
DECREASING THIS WEEKEND, AS ARE PRECIPITATION FORECAST AMOUNTS.
THIS IS ESPECIALLY TRUE OF THE NORTHERN 1/4 OF COLORADO (SAY
NORTH OF US-34) BECAUSE THE QG LIFT AND INSTABILITY WILL BE TOO
FAR SOUTH. STARTING AT THE JET LEVEL, THE JET STREAK ROTATING
AROUND THE TROUGH IS TOO FAR SOUTH TO PROVIDE MUCH LIFT, THOUGH
SATURDAY AFTERNOON THERE IS PRETTY GOOD DIFFLUENCE OVER OUR AREA.
THE 700 MB TROUGH MEANDERS ACROSS ARIZONA, BUT STAYS TOO FAR SOUTH
TO GENERATE ANY EAST UPSLOPE FLOW FOR THE FRONT RANGE INTO
SUNDAY, AND THE COLD AIR ALOFT LIKEWISE STAYS OVER ARIZONA THROUGH
SATURDAY. THE NET RESULT IS SNOW LEVELS REMAIN REALLY HIGH FOR
MID TO LATE OCTOBER, GOING FROM 10 KFT CURRENTLY DOWN TO MAYBE
8,500 FT BY SUNRISE SATURDAY, THEN IF YOU CAN BELIEVE IT WARM
ADVECTION PICKS UP SATURDAY WITH SOUTHERLY FLOW AROUND THE TROUGH
AND THE SNOW LEVEL GOES BACK UP TO 9500-10000 FT MSL. GIVEN THE
LACK OF LIFT FROM THE TROUGH, OR UPSLOPE (SOUTHERLY FLOW ALOFT IS
POOR FOR PRETTY MUCH OUR ENTIRE AREA), THE MAIN FORCING IS
CONVECTIVE. HREF ENSEMBLE MEAN CAPE IS WELL OVER 500 J/KG, NOT TOO
SHABBY FOR THE COOL SEASON, AND MAXIMIZED ALONG AND EAST OF THE
PALMER DIVIDE, WITH ANOTHER ZONE OF INSTABILITY LOCATED ACROSS
PARK COUNTY. WE'VE INCLUDED THUNDER IN THE GRIDS FOR LATER THIS
AFTERNOON AND INTO EARLY SATURDAY, AND THE BEST PRECIPITATION
RATES WILL BE WITH THIS INITIAL ROUND OF CONVECTION. THE PLACES
MOST LIKELY TO SEE A DECENT SNOW IS ALONG AND SOUTH OF I-70 ABOVE
10,000 FT, ESPECIALLY THE MOSQUITO RANGE WHERE 6-10" COULD FALL
ABOVE 11,000 FT. HOOSIER/FREMONT PASSES AND THE I-70 TUNNELS MIGHT
HAVE SLICK SPOTS TONIGHT AND INTO EARLY SATURDAY, BUT OVERALL
IMPACTS AND AMOUNTS DON'T LOOK ENOUGH TO ISSUE AN ADVISORY. ALSO,
IF THE CONVECTIVE PRECIP DOESN'T PAN OUT THAT MUCH, THEN TOTAL
SNOW/RAIN AMOUNTS WILL BE MUCH LESS THAT CURRENTLY FORECAST
BECAUSE TOTALS OVERALL REALLY DEPEND ON THIS FIRST BATCH OF
CONVECTIVE PRECIP.
ALONG AND NORTH OF I-70, AND FOR THE I-25 CORRIDOR FROM CASTLE
ROCK TO WYOMING, RAINFALL AMOUNTS LOOK TO BE LIGHT GIVEN LESS
INSTABILITY AND NO EAST UPSLOPE FLOW. EVEN ISENTROPIC UPGLIDE
NORTH OF THE SURFACE COLD FRONT IS NOT IMPRESSIVE ANYMORE. EXPECT
A FEW HUNDREDTHS NORTH OF US-34, AND A TENTH OR TWO SOUTH TO THE
PALMER DIVIDE. THERE LOOKS TO BE ANOTHER ROUND OF LIGHT PRECIP
MOVING INTO OUR AREA FROM THE SOUTH AFTER SUNRISE SATURDAY
ASSOCIATED WITH THE CUT OFF LOW'S DEFORMATION ZONE, BUT MOST OF
THE PRECIPITATION SHOULD REMAIN ALONG AND SOUTH OF I-70 SATURDAY
MORNING. AS SOME COLD AIR MOVES OVERHEAD TOMORROW, WEAK CONVECTIVE
RAIN/SNOW SHOWERS ARE POSSIBLE MAINLY FOR THE SOUTHERN HALF OF
OUR AREA, BUT OVERALL CHANCES ARE 20-40%, AND SNOW LEVELS WILL BE
9500-10000 FT DURING THE AFTERNOON. LIGHT ACCUMULATION IS
EXPECTED FROM THE PRECIPITATION THAT DEVELOPS SATURDAY EVENING.
SLICK SPOTS ARE POSSIBLE ON THE HIGHER MOUNTAIN PASSES ALONG AND
SOUTH OF I-70 AFTER SUNSET.
IN TERMS OF TEMPERATURES, IT WILL BE CLOUDY OR MOSTLY CLOUDY FOR
ALL BUT NORTH AND MIDDLE PARKS TOMORROW, AND WITH COLD AIR ALOFT
MOVING OVERHEAD DURING THE DAY, WARMING WILL BE KEPT IN CHECK.
EXPECT MOSTLY 50S FOR HIGHS ACROSS THE PLAINS AND I-25 CORRIDOR,
LOW 40S FOR SOUTH PARK AND THE SOUTHERN FOOTHILLS. THE WARMEST
LOCATION ON SATURDAY BELIEVE IT OR NOT COULD BE MIDDLE PARK WITH
TEMPERATURES IN THE LOW 60S WITH SOME SUNSHINE.
LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/
ISSUED AT 233 PM MDT FRI OCT 18 2024
MODELS HAVE THE UPPER CLOSED LOW OVER CENTRAL ARIZONA AT 00Z
SATURDAY AFTERNOON LATE, WHICH IS FURTHER SOUTH THAN YESTERDAY'S
RUNS INDICATED. IT PUSHES NORTHEASTWARD INTO THE FOUR CORNERS BY 00Z
LATE SUNDAY AFTERNOON, THEN TO THE NORTHEASTERN CORNER OF COLORADO
BY AROUND 18Z MONDAY. THIS IS SLOWER THAN YESTERDAY'S MODEL RUNS
INDICATED. THE UPPER LOW DOESN'T WEAKEN AS MUCH ON THE CURRENT
MODEL RUNS AS IT DID ON YESTERDAY'S. THE QG OMEGA FIELDS HAVE
SYNOPTIC SCALE ASCENT FOR THE CWA BY SUNDAY MORNING CONTINUING INTO
MONDAY MORNING, BUT IT IS WEAK. SUBSIDENCE IS FAIRLY STRONG BEHIND
THE CLOSED LOW, MONDAY AFTERNOON TO MID EVENING.
THE UPPER LOW HAS NO COLD AIR WITH AS IT IS CUT OFF FROM THE MAIN
FLOW WELL NORTH OF US IN CANADA. THERE IS FAIRLY DECENT SOUTHERLY
LOW LEVEL WINDS OVER THE PLAINS ON SUNDAY INTO SUNDAY NIGHT WITH
DOWNSLOPING WINDS TO KICK IN AFTER THE UPPER LOW MOVES EAST BY
MONDAY AFTERNOON INTO THE EVENING.
FOR MOISTURE, IT IS SPARSE SATURDAY NIGHT INTO SUNDAY MORNING, BUT
INCREASES AS THE UPPER LOW MOVES ACROSS THE CWA LATER IN THE DAY AND
OVERNIGHT. THE BEST QPF FOR THE MOUNTAINS WILL BE SUNDAY
AFTERNOON AND SUNDAY NIGHT WITH A TAD LINGERING INTO MONDAY
MORNING. OVER THE PLAINS, THERE WILL BE A BRIEF PERIOD, OF JUST A
CHANCE OF RAIN, LATER SUNDAY NIGHT INTO MONDAY MORNING. OVERALL,
THE UPPER LOW WILL NOT BRING A SIGNIFICANT PRECIPITATION EVENT TO
OUR FORECAST AREA. THERE IS A BIT OF CAPE FOR THE CWA ON SUNDAY
AS THE UPPER LOW MOVES ACROSS SO WILL LEAVE THE MENTION OF
ISOLATED THUNDER IN WITH THE SCATTERED AND LIKELY POPS.
FOR SNOWFALL IN THE MOUNTAINS, THERE WILL BE SOME ACCUMULATIONS,
MAINLY ALONG THE DIVIDE ABOVE 10,000 FEET FROM SUNDAY AFTERNOON
INTO MONDAY MORNING.
FOR TEMPERATURES, THE COOLEST DAY WILL BE SATURDAY. SUNDAY'S HIGHS
WILL BE 2.0 TO 5.0 C WARMER THAN SATURDAY'S. MONDAY'S HIGHS LOOK
SIMILAR TO SUNDAY'S HIGHS.
FOR THE LATER DAYS, TUESDAY THROUGH FRIDAY, MODELS KEEP UPPER
RIDGING OVER THE CWA ALL FOUR DAYS, WITH ABOVE NORMAL TEMPERATURES
AND NO POPS. AFTERNOON HIGHS SHOULD BE IN THE UPPER 60S TO UPPER
70S OVER THE PLAINS ALL FOUR DAYS WITH THE COOL DAY BEING WEDNESDAY.
AVIATION /06Z TAFS THROUGH 06Z SUNDAY/
ISSUED AT 1147 PM MDT FRI OCT 18 2024
PERIODS OF IFR AND MVFR ARE POSSIBLE THROUGH 10Z FOR KAPA AND
KBJC DUE TO FOG. CLOUD DECKS REMAIN LOW NEAR 6-9 THOUSAND FEET.
THERE COULD BE PERIOD OF BREAKS IMPROVING TO VFR CONDITIONS. BY
SATURDAY MORNING, CONDITIONS SHOULD IMPROVE TO VFR BY 17-19Z.
SOUTHERLY WINDS WILL INCREASE AS THE SYSTEM PUSHES EASTWARD.
EXPECT WIND GUSTS UP TO 20-25KTS THROUGH SATURDAY EVENING.
BOU WATCHES/WARNINGS/ADVISORIES
NONE.
UPDATE...GIMMESTAD
SHORT TERM...SCHLATTER
LONG TERM....RJK
AVIATION...AD
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