917
FXUS63 KLSX 261151
AFDLSX
AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE SAINT LOUIS MO
551 AM CST TUE JAN 26 2021
SHORT TERM
(THROUGH LATE WEDNESDAY AFTERNOON)
ISSUED AT 410 AM CST TUE JAN 26 2021
HAVE CONTINUED THE WINTER WEATHER ADVISORY THROUGH 6 AM. RECENT
REPORTS OVER THE ADVISORY AREA INDICATE THAT PRECIPITATION THAT HAS
BEEN OCCURRING OVER THE PAST FEW HOURS HAS BEEN A MIX OF LIGHT
FREEZING DRIZZLE AND LIGHT SNOW WITH THE ONLY GLAZING ON ELEVATED
SURFACES. LATEST ASOS/AWOS OBS ARE NOW SHOWING MAINLY SNOW, SO
EXPECT THAT ICE THREAT IS LESSENING WITH TIME, SO DO NOT NEED TO
EXTEND THE ADVISORY PAST 6 AM.
LATEST WATER VAPOR IMAGERY IS SHOWING TWO UPPER WAVES, ONE CURRENTLY
OVER WESTERN IOWA THAT WILL MOVE QUICKLY NORTH OF THE AREA THIS
MORNING AND ANOTHER OVER SOUTHWEST CONUS. THE FIRST WILL BRING
ENOUGH ASCENT THROUGH THIS MORNING TO BRING A CHANCE OF LIGHT SNOW
OR LIGHT FREEZING RAIN THIS MORNING, BUT ANY AMOUNTS WILL BE LIGHT.
BY THIS AFTERNOON. THIS SYSTEM WILL LIFT NORTHEAST OF THE AREA
AND EXPECT DRY CONDITIONS UNTIL THE LATE EVENING AND OVERNIGHT
BEFORE ASCENT BEGINS TO INCREASE AHEAD THE NEXT TROUGH. WHILE THIS
SYSTEM WILL BE MOVING THROUGH THE AREA FAIRLY QUICKLY, THE
HREF/NAM/GFS ALL SHOW DECENT ASCENT, SO WENT WITH LIKELY/
CATEGORICAL POPS FOR SNOW LATE TONIGHT INTO WEDNESDAY MORNING WITH
ACCUMULATIONS OF 1/2-1". SNOW SHOULD MOVE OUT OF THE AREA BY LATE
WEDNESDAY AFTERNOON.
WE WILL STAY IN A COLD AIR ADVECTION PATTERN OVER THE NEXT 36 HOURS
UNDER CLOUD COVER. I DON'T NOT EXPECT MORE THAN A 5 DEGREE
RECOVERY TODAY, THOUGH LOWS WILL NOT DROP TOO MUCH TONIGHT WITH
THE CLOUDS. HIGHS TOMORROW WILL BE COLDER WITH THE CAA.
BRITT
LONG TERM
(WEDNESDAY NIGHT THROUGH MONDAY)
ISSUED AT 410 AM CST TUE JAN 26 2021
LATEST GUIDANCE FROM THE GFS AND ECMWF ENSEMBLES IS STILL SHOWING A
UPPER RIDGE BUILDING ACROSS THE MIDDLE OVER THE CONUS BY LATE IN THE
WEEK THAT WILL SET UP NORTHWEST FLOW OVER MISSOURI AND ILLINOIS.
THIS WILL BRING DRY WEATHER TO THE AREA FROM WEDNESDAY NIGHT INTO
FRIDAY NIGHT AS A LARGE SURFACE HIGH MOVES ACROSS THE REGION. THE
UPPER RIDGE WILL MOVE EAST ACROSS MIDWEST BY EARLY SATURDAY AT THE
SAME TIME THAT A TROUGH OVER THE WEST COAST WILL MOVE EAST INTO THE
PLAINS. BOTH ENSEMBLES AND DETERMINISTIC MODELS ARE SHOWING AN
ATTENDANT SURFACE LOW MOVING ACROSS MISSOURI AND ILLINOIS
SATURDAY INTO SUNDAY WITH STRONG MOISTURE TRANSPORT AHEAD OF IT.
THIS JUSTIFIES CATEGORICAL POPS SATURDAY INTO SATURDAY NIGHT GIVEN
THE IMPLIED ASCENT WITH THE NEGATIVELY TILTED TROUGH SEEN IN THE
DETERMINISTIC MODELS. THERE WILL INITIALLY BE A MIX OF RAIN AND
SNOW WITH THE ONSET OF PRECIPITATION ON SATURDAY MORNING, BUT
THEN MAINLY RAIN IS EXPECTED SATURDAY AFTERNOON INTO SATURDAY
NIGHT. THIS TROUGH WILL THEN LIFT OUT THE AREA BY LATE SUNDAY WITH
UPPER RIDGING BUILDING IN BEHIND IT, SO KEPT SUNDAY AND MONDAY
DRY.
TEMPERATURES WILL GRADUALLY WARM BACK ABOVE NORMAL AS THE SURFACE
HIGH MOVES THROUGH THE AREA AND THE SURFACE FLOW TURNS OUT OF THE
SOUTHWEST AND 850MB TEMPERATURES CLIMB FROM AROUND -5C ON THURSDAY
MORNING TO AROUND 0-5C ON FRIDAY AND SATURDAY. THIS IS REFLECTED
WELL BY THE ENSEMBLE GUIDANCE PLUMES.
BRITT
AVIATION
(FOR THE 12Z TAFS THROUGH 12Z WEDNESDAY MORNING)
ISSUED AT 529 AM CST TUE JAN 26 2021
LOW CLOUDS ARE EXPECTED THROUGH THE PERIOD, WITH IFR CEILINGS
THROUGH THE PERIOD AT BOTH KUIN AND KCOU WITH IFR/MVFR
VISIBILITIES MOST OF THE DAY IN FOG. KUIN WILL ALSO HAVE A CHANCE
OF SNOW AND FREEZING DRIZZLE THIS MORNING WITH MINOR
ACCUMULATIONS. THE ST. LOUIS METRO TERMINALS WILL ALSO HAVE IFR OR
LOW MVFR CEILINGS THROUGH THE PERIOD. ALL OF THE TERMINALS WILL
HAVE A CHANCE OF SNOW AFTER 06Z TONIGHT.
SPECIFICS FOR KSTL:
LIFR CONDITIONS ARE EXPECTED IN LOW CEILINGS AND FOG THROUGH MID
MORNING, WITH IFR CEILINGS EXPECTED THROUGH THIS EVENING. SNOW
WILL MOVE INTO THE TERMINAL LATE TONIGHT AND CONTINUE THROUGH
WEDNESDAY MORNING WITH MINOR ACCUMULATIONS.
BRITT
LSX WATCHES/WARNINGS/ADVISORIES
MO...WINTER WEATHER ADVISORY UNTIL 6 AM CST EARLY THIS MORNING FOR
KNOX MO-LEWIS MO-MARION MO-SHELBY MO.
IL...WINTER WEATHER ADVISORY UNTIL 6 AM CST EARLY THIS MORNING FOR
ADAMS IL-BROWN IL.
WFO LSX
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