971
FXUS65 KBOU 181924
AFDBOU
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DENVER/BOULDER CO
124 PM MDT MON MAY 18 2026
KEY MESSAGES
- RAIN AND MOUNTAIN/FOOTHILL SNOW WILL GRADUALLY DECREASE THROUGH
THIS EVENING. A FEW WET SNOWFLAKES MAY STILL MIX IN FOR THE
I-25 CORRIDOR.
- NEAR FREEZING TEMPERATURES AND FROST/FREEZE HIGHLIGHTS FOR MOST
OF THE PLAINS, BUT SOME UNCERTAINTY AS TO HOW COLD WITH MORE
LINGERING CLOUD COVER.
- STILL UNSETTLED TUESDAY THROUGH THURSDAY WITH SCATTERED TO
NUMEROUS SHOWERS AND A FEW STORMS, MOST NUMEROUS IN/NEAR THE
FRONT RANGE.
- WARMING AND DRYING TREND FOR THE WEEKEND.
DISCUSSION /THROUGH MONDAY/
ISSUED AT 123 PM MDT MON MAY 18 2026
SATELLITE SHOWS THE UPPER LEVEL TROUGH EJECTING EAST/NORTHEAST
ACROSS THE FORECAST AREA THIS AFTERNOON, WITH AN ENHANCED BAND OF
PRECIPITATION AND EVEN A COUPLE THUNDERSTORMS MOVING EAST ACROSS
THE FORECAST AREA. THE PRECIPITATION WILL WEAKEN AS IT MOVES ONTO
THE EASTERN PLAINS AS THE UPPER LEVEL TROUGH CONTINUES TO SHEAR
AND WEAKEN, AND UPPER LEVEL SUPPORT IS REPLACED BY WEAK
SUBSIDENCE. AFTER THE TROUGH PASSAGE, WE STILL HAVE SOME
WEAK UPSLOPE TO WORK WITH SO WE'LL DELAY THE DISSIPATION OF
SHOWERS IN/NEAR THE FRONT RANGE OVERNIGHT. IN FACT, A FEW LIGHT
SHOWERS COULD LINGER WELL PAST MIDNIGHT, WITH THE LAST OF THEM
DISSIPATING IN/NEAR THE SOUTHERN FOOTHILLS TOWARD DAYBREAK
TUESDAY. ALL EXISTING WINTER STORM WARNINGS AND ADVISORIES WILL
REMAIN IN TACT THROUGH 9 PM, BUT ANY TRAVEL IMPACTS SHOULD BE
WANING AS PRECIPITATION RATES DECREASE. STILL CAN'T RULE OUT A FEW
SNOWFLAKES MIXING IN WITH THE SNOW DOWN TOWARD THE I-25 URBAN
CORRIDOR DURING HEAVIEST CONVECTIVE SHOWERS THIS AFTERNOON AND
THEN THIS EVENING AS TEMPERATURES ALOFT COOL SLIGHTLY.
WITH REGARD TO THE POTENTIAL FREEZE ACROSS THE PLAINS TONIGHT. THE
LATEST TRENDS ARE FOR MORE CLOUDS AND HIGHER LOW LEVEL MOISTURE,
MAKING IT MORE DIFFICULT FOR TEMPERATURES TO DROP. WE THINK MOST
OF THE DENVER/BOULDER METRO AREA WILL STAY JUST ABOVE FREEZING DUE
TO MOSTLY CLOUDY SKIES PERSISTING THROUGH THE NIGHT, WHILE THE
PLAINS NORTH AND EAST OF DENVER COULD SEE AREAS OF FROST WITH
PARTIAL CLEARING BUT STILL SOME LIGHT NORTHERLY WINDS. THE PALMER
DIVIDE SHOULD STILL END UP COLDER SO WENT WITH A FREEZE WARNING
THERE, BUT EVEN THEN ONLY THE HIGHER ELEVATIONS ABOVE 6500 FEET
WOULD BE MOST PRONE TO SUB FREEZING TEMPERATURES.
ON TUESDAY, THE AIRMASS WILL BE MORE STABLE BUT THERE'S STILL
ENOUGH MOISTURE AND SHALLOW INSTABILITY FOR LATE DAY
SHOWER/ISOLATED STORM DEVELOPMENT IN/NEAR THE HIGHER TERRAIN. THAT
SHOWER DEVELOPMENT AND COVERAGE WILL ALSO BE SUPPORTED BY WEAK QG
FORCING. TEMPERATURES WILL REMAIN WELL BELOW NORMAL, WITH HIGHS
ONLY IN THE 50S OVER MOST OF THE PLAINS.
WEDNESDAY SHOULD SEE AN UPTICK IN CONVECTIVE SHOWER/STORM COVERAGE
IN THE AFTERNOON AS LAPSE RATES ALOFT BECOME MOIST ADIABATIC, AND
WE CONTINUE TO SEE WEAK FORCING AS THE MEAN UPPER LEVEL TROUGH
AXIS HOLDS OFF TO OUR WEST. TEMPERATURES WILL ONLY MODERATE A FEW
DEGREES, AND STILL BE 10-15 DEGREES BELOW NORMAL.
THE TREND FOR THURSDAY HAS BEEN TOWARD MORE ACTIVE AND STRONGER
CONVECTIVE DEVELOPMENT. THE MAIN REASON BEHIND THIS IS A STRONGER
AND DEEPER UPPER LEVEL TROUGH DROPPING SOUTHEAST ACROSS THE
ROCKIES. THAT WILL SUPPORT STEEPER LAPSE RATES, AND COMBINED WITH
MODERATE LOW LEVEL MOISTURE MEANS INCREASING INSTABILITY. MLCAPE
FROM VARIOUS MORE RELIABLE PROGS INDICATE 500-1000 J/KG ACROSS
MOST OF THE PLAINS AND I-25 CORRIDOR, SO THERE WILL BE POTENTIAL
FOR A COUPLE SEVERE STORMS.
AS LONG AS THIS TROUGH PASSES BY THURSDAY NIGHT (AND THE SLOWER
PASSAGE HAS CONTINUED IN THE LATEST ENSEMBLE MEANS), FRIDAY
SHOULD FINALLY TREND DRIER. TEMPERATURES WILL THEN START A WARMING
TREND FOR THIS WEEKEND WITH MORE ZONAL FLOW ADVERTISED IN THE
ENSEMBLES, SO EVENTUALLY WE SHOULD RETURN TO NEAR OR ABOVE NORMAL
TEMPERATURES.
AVIATION /18Z TAFS THROUGH 18Z TUESDAY/
ISSUED AT 1159 AM MDT MON MAY 18 2026
MODEL CROSS SECTIONS INDICATE THAT THE CEILING SHOULD BE AT OR
BELOW BKN-OVC015 AT DIA THE REST OF THE TODAY AND ALL OF TONIGHT.
WILL LEAVE A PROB30 IN FOR TSRA THIS AFTERNOON FOR 3 OR 4 HOURS
BASED ON THE INSTABILITY AVAILABLE. VISIBLITIES SHOULD RANGE FROM
1SM-5SM, LOWER WITH THE BETTER RAIN SHOWERS THROUGH AROUND 00Z
THIS AFTERNOON. WILL GET VISIBILITIES TO P6SM AFTER THAT. THERE
COULD BE PATCHY FOG DEVELOPING AFTER 06Z TONIGHT, BUT THERE IS
ENOUGH UNCERTAINTY AT THIS TIME SO I WILL IT OUT FOR NOW.
BOU WATCHES/WARNINGS/ADVISORIES
WINTER WEATHER ADVISORY UNTIL 9 PM MDT THIS EVENING FOR COZ030-
031-034-035.
FROST ADVISORY FROM MIDNIGHT TONIGHT TO 8 AM MDT TUESDAY FOR
COZ038-042>051.
FREEZE WARNING FROM MIDNIGHT TONIGHT TO 8 AM MDT TUESDAY FOR
COZ041.
DISCUSSION...20
AVIATION...66
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