146
FXUS63 KEAX 172332
AFDEAX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE KANSAS CITY/PLEASANT HILL MO
632 PM CDT SAT APR 17 2021
DISCUSSION
ISSUED AT 259 PM CDT SAT APR 17 2021
KEY MESSAGES...
1. LATE APRIL COLD SPELL, TEMPERATURES AT OR JUST BELOW FREEZING
TUESDAY MORNING, HIGHS IN THE LOWER 40S F. WEDNESDAY MORNING
LOWS IN THE UPPER 20S F, HIGHS NEAR 50 F.
2. SNOW POSSIBLE LATE MONDAY/EARLY TUESDAY THROUGH THE MORNING.
ACCUMULATIONS ON GRASSY AND ELEVATED SURFACES IS LOOKING
LIKELY. UPWARDS OF A HALF INCH TO 1.5 INCHES ACROSS PORTIONS
OF WESTERN MISSOURI AND ADJACENT EASTERN KANSAS. SOME SLUSHY
ROADS IN NORTHERN MISSOURI CANNOT BE RULED OUT.
DETAILED DISCUSSION...
THROUGH THIS AFTERNOON, SOME ADDITIONAL SCATTERED SHOWERS AND
ISOLATED THUNDER ARE POSSIBLE ACROSS THE REGION THROUGH THE
EVENING. THE INFLUENCE FROM THE SECONDARY SHORT WAVE, STEEP LAPSE
RATES, AND WEAK INSTABILITY WILL PROMOTE SOME ISOLATED THUNDER,
BUT NO SEVERE STORMS ARE EXPECTED. THIS SHORT WAVE WILL PROVIDE
ANOTHER CHANCE FOR RAIN SUNDAY, PRIMARILY ACROSS CENTRAL MISSOURI.
MONDAY REMAINS TO BE RATHER QUIET, SO WE'LL CONTINUE TO FOCUS ON
THE WINTER EVENT MONDAY NIGHT/TUESDAY. ASSOCIATED WITH A DEEPENING
HUDSON BAY LOW, A BROAD COLD FRONT WILL STRETCH FROM THE GREAT
LAKES ACROSS THE NORTHERN PLAINS. OVERALL TRENDS FROM LONG/MID
RANGE GUIDANCE HAVE BEEN RATHER CONSISTENT DAY TO DAY. THE GFS
REMAINS MORE BULLISH, WHICH IT TENDS TO DO IN THESE POSITIVELY
TILTED TROUGH SCENARIOS. AGREE WITH DISCUSSIONS FROM WPC ON
LEANING TOWARD THE ECMWF AND LATEST NAM, WHICH IS A STEP SLOWER
THAN THE GFS. BE CAREFUL NOT TO LOCK INTO THE MODEL QPF, WHICH IS
TYPICALLY OVERDONE BY A FEW TENTHS TO A QUARTER OF AN INCH WITH
THESE LATE SEASON SYSTEMS. THIS WILL HAVE A SIGNIFICANT INFLUENCE
ON SNOW- LIQUID- RATIOS (SLRS) AND THEREFORE SNOW AMOUNTS. I DON'T
WANT TO RE-HASH JARED'S EXCELLENT DISCUSSION FROM THIS MORNING.
WHAT HE WROTE STILL APPLIES, WITH A VERY COLD AIRMASS RESULTING IN
THERMAL PROFILES COOLING CONSIDERABLY AND AMPLE MOISTURE THROUGH
THE DENDRITIC GROWTH ZONE (DGZ) EASILY SUPPORTING ICE CRYSTALS.
SUNSET MONDAY, EARLY PRECIPITATION WILL BEGIN AS RAIN, BUT EXPECT
A RATHER QUICK CHANGE OVER TO SNOW IN NORTHWEST MISSOURI AS THE
FRONT PUSHES IN AFTER MIDNIGHT. FARTHER SOUTH, THE CHANGE OVER
WILL BE GRADUAL, THROUGH THE PRE-DAWN HOURS, WITH RAIN/SNOW MIX
FINALLY CHANGING OVER TO SNOW JUST BEFORE SUNRISE. WITH ALL OF
THIS SAID, YOU HAVE TO KEEP BOUNDARY LAYER/SURFACE TEMPERATURES IN
MIND. WE CAN EASILY GET ACCUMULATING SNOW ON GRASSY AND ELEVATED
SURFACES WITH TEMPS IN THE MID-30S F. SNOW RATES AND HOW QUICKLY
AND/IF WE GET TO 32 F AT THE SURFACE WILL DICTATE IF ROADS BEGIN
TO TAKE ON SNOW. THERE ARE A LOT OF VARIABLES AT PLAY HERE FOR
WHAT TYPE OF IMPACTS WE COULD SEE. WITH THAT SAID, +0 C WET BULB
TEMPS ARE BASICALLY AT THE SURFACE/BOUNDARY LAYER, WITH THE
THERMAL PROFILE WELL BELOW FREEZING. WITH FORECAST SOUNDINGS
ACROSS NORTHWESTERN AND NORTHERN MISSOURI AND AS FAR SOUTH AS THE
MISSOURI RIVER AND THE KC METRO WITH SIMILAR PROFILES THROUGH
TUESDAY MORNING. IT WILL BE VERY EASY FOR SNOW EVEN WITH
TEMPERATURES UP TO 35 AND A MIX OF RAIN AND SNOW UP TO 40 F. WITH
SLRS OF 7-9 TO 1 AND TOTAL QPF OF A TENTH TO A HALF INCH, THERE'S
POTENTIAL FOR HALF INCH TO 1.5 INCHES OF SNOW ACROSS THE AREA. IF
THE NARROW BAND OF STOUT 700 TO 850MB FRONTOGENESIS COMES THROUGH
AT THE CLIP GUIDANCE IS GIVING US NOW, THERE COULD BE ONE TO TWO
HOUR POCKETS IN THERE WITH SNOWFALL RATES HIGH ENOUGH FOR SOME
SLUSH TO ACCUMULATE ON ROADWAYS ACROSS NORTHERN MISSOURI AND
ADJACENT NORTHEAST KANSAS. I WILL NOT BE SURPRISED TO SEE
ACCUMULATING SNOW ON GRASSY AND ELEVATED SURFACES ACROSS PORTIONS
OF THE THE REGION, AND THE CURRENT FORECAST IS FOR UPWARDS OF A
HALF TO AN INCH IN KC METRO. EXPECT PRECIP TO END QUICKLY THROUGH
TUESDAY EVENING, WITH ANY LINGERING PRECIP AS RAIN, MOST LIKELY AS
SURFACE TEMPERATURES REACH THE LOWER 40S EVENTUALLY.
TO WRAP THIS UP, THESE LATE SEASON WINTER EVENTS ARE A BEAR TO
FORECAST. ONE CANNOT RELY ON DIRECT MODEL SNOW OUTPUT (HONESTLY,
NO ONE SHOULD EVER DO THIS.). THIS IS NOT A WOUND UP FEBRUARY
LOW, BUT IT'S STOUT AND CARRYING ENOUGH QPF AND COLD AIR TO EASILY
RESULT IN SNOWFALL ACROSS A MAJORITY OF THE REGION. THE THERMAL
PROFILE MATTERS GREATLY AND SURFACE TEMPERATURES AND SNOW RATES
HAVE A LARGE SAY IN ACCUMULATING SNOW. THIS FORECAST WILL BE
REFINED SEVERAL TIMES BETWEEN NOW AN MONDAY NIGHT. SO BUCKLE UP,
IT'S GOING TO BE A JOURNEY.
FOR THE REMAINDER OF THE WEEK, WEDNESDAY WILL BE RATHER QUIET,
STILL COOL, BUT KICK OFF A WARMING TREND. THURSDAY WILL WARM UP,
AHEAD OF THE NEXT UPPER SYSTEM, A DEEPENING TROUGH OVER THE
SOUTHWEST, WITH LARGE SCALE ASCENT AHEAD, BRINING RAINFALL TO
CLOSE OUT THE WORK WEEK.
AVIATION
(FOR THE 00Z TAFS THROUGH 00Z SUNDAY EVENING)
ISSUED AT 623 PM CDT SAT APR 17 2021
RAIN SHOWERS WILL CONTINUE TO MOVE THROUGH THE TERMINALS EARLY IN
THE PREVAILING PERIOD WITH THE POSSIBILITY OF VISIBILITY DROPPING
DOWN TO MVFR BRIEFLY IF A RAIN SHOWERS MOVES OVER THE TERMINAL.
SHOWERS SHOULD QUICKLY DIMINISH NEAR TO JUST AFTER SUNSET WITH
LOSS OF DAYTIME HEATING BUT SCT TO BKN CLOUD DECK LOOKS TO LINGER
OVERNIGHT BEFORE CU FIELD REDEVELOPS TOMORROW WITH THE RETURN OF
DIURNAL HEATING. WINDS WILL REMAIN OUT OF THE NORTH TO NORTHWEST
AT ABOUT 5 TO 10 KTS.
EAX WATCHES/WARNINGS/ADVISORIES
KS...NONE.
MO...NONE.
DISCUSSION...KURTZ
AVIATION...PIETRYCHAP
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