784
FXUS63 KLSX 211744
AFDLSX
AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE SAINT LOUIS MO
1144 AM CST TUE JAN 21 2025
KEY MESSAGES
- BITTERLY COLD ARCTIC AIR CURRENTLY RESIDES ACROSS THE REGION
WITH MINIMUM WIND CHILLS EARLY THIS MORNING RANGING FROM -10 TO
-30F FROM SOUTH TO NORTH.
- DANGEROUS WIND CHILL VALUES OF -10 TO -15F ARE FORECAST AGAIN
THIS EVENING INTO VERY EARLY WEDNESDAY MORNING ACROSS PARTS OF
SOUTH-CENTRAL ILLINOIS WHERE A NEW COLD WEATHER ADVISORY HAS
BEEN ISSUED.
- TEMPERATURES WILL MODERATE QUICKLY ON WEDNESDAY, WITH READINGS
CLOSER TO NORMAL THROUGH THE WEEKEND.
SHORT TERM
(THROUGH LATE WEDNESDAY AFTERNOON)
ISSUED AT 301 AM CST TUE JAN 21 2025
THE ARCTIC FRONT HAS RECENTLY CLEARED THE CWA AND CONTINUES TO PUSH
OFF TO THE SOUTHEAST. JUST BEHIND THE FRONT, SOME SCATTERED LIGHT
SNOW FLURRIES HAVE BEEN DENOTED. ANY FLURRY ACTIVITY ACROSS PORTIONS
OF SOUTHEAST MISSOURI AND SOUTHWEST ILLINOIS SHOULD ALSO MOVE OUT
OVER THE NEXT 2-3 HOURS.
TEMPERATURES THIS MORNING HAVE DROPPED BELOW ZERO FROM PARTS OF
CENTRAL MISSOURI THROUGH WEST-CENTRAL ILLINOIS WITH READINGS BELOW -
10F NOW JUST SOUTH OF THE MISSOURI-IOWA BORDER. NORTHWEST WINDS
HAVE LIGHTENED UP ON THE PERIPHERY OF A 1044 HPA HIGH OVER
NORTHEAST KANSAS. HOWEVER, ANY WINDS WITH THESE KIND OF
TEMPERATURES HAS A BIG IMPACT ON WIND CHILLS. WIND CHILL READINGS
AT 0800 UTC ARE WELL INTO ADVISORY CRITERIA FOR MOST OF THE AREA,
OTHER THAN PARTS OF SOUTHEAST MISSOURI AND SOUTHWEST ILLINOIS.
TEMPERATURES SHOULD CONTINUE TO DROP THE NEXT 3-4 HOURS, SO WE ARE
EXPECTING WIND CHILL VALUES WILL AS WELL. MINIMUM WIND CHILL
READINGS WILL LIKELY BE BETWEEN 5-7 AM, RANGING FROM -10 TO -30F
FROM SOUTH TO NORTH. HAVE UPGRADED OUR FAR NORTHERN COUNTIES TO A
WARNING GIVEN THE COLDER WIND CHILL VALUES OBSERVED, WITH NO
CHANGES ELSEWHERE.
WHILE THERE WILL BE PLENTY OF SUNSHINE TODAY, HIGHS WILL ONLY
REACH THE SINGLE DIGITS TO TEENS. THIS WILL BE THE COLDEST DAY OF
THE WINTER SEASON ACROSS THE REGION, WITH THE AFOREMENTIONED HIGHS
25-30 DEGREES BELOW NORMAL FOR THE DATE.
THE SURFACE RIDGE AXIS IS EXPECTED TO CONTINUE TO SLIDE EAST THROUGH
THE NIGHT, CROSSING INTO THE UPPER OHIO VALLEY BY LATE TONIGHT.
SOUTHERLY WINDS WILL INCREASE IN ITS WAKE, AND THIS COMBINED WITH
INCREASING CLOUDS WILL COMBINE TO YIELD RISING TEMPERATURES.
HOWEVER, TEMPERATURES SHOULD FALL THROUGH ABOUT 12-2 AM ACROSS
PARTS OF SOUTH-CENTRAL ILLINOIS DUE TO THE TIMING OF THE SURFACE
RIDGE. THIS MEANS ANOTHER ROUND OF DANGEROUS WIND CHILLS (-10 TO
-15F) ARE LIKELY FROM LATE EVENING THROUGH THE OVERNIGHT HOURS. AS
A RESULT, ISSUED ANOTHER COLD WEATHER ADVISORY FOR THIS AREA.
THIS IS WHERE LOWS IN THE SINGLE DIGITS ARE EXPECTED. FURTHER
WEST/NORTHWEST, THE SOUTHERLY WINDS WILL BEGIN EARLIER, PREVENTING
MUCH IN THE WAY OF A TEMPERATURE DROP THIS EVENING. LOWS IN THE
MID TEENS ARE FORECAST ACROSS CENTRAL MISSOURI.
THE WARMUP IS FULLY UNDERWAY ON WEDNESDAY AS THE ENTIRE MID-
MISSISSIPPI VALLEY UNDERGOES SIGNIFICANT LOW-LEVEL WARM AIR
ADVECTION. THE ARCTIC AIR MASS WILL BE A THING OF THE PAST AS
TEMPERATURES WARM INTO THE UPPER 20S TO MID 30S. YES, THOSE VALUES
ARE STILL SEVERAL DEGREES BELOW NORMAL, BUT 20-25 DEGREES WARMER
THAN THIS AFTERNOON.
GOSSELIN
LONG TERM
(WEDNESDAY NIGHT THROUGH MONDAY)
ISSUED AT 301 AM CST TUE JAN 21 2025
(WEDNESDAY NIGHT - FRIDAY)
THE CONCERN FOR WEDNESDAY NIGHT REMAINS ON THE POTENTIAL FOR LIGHT
SNOW IN NORTHEAST MISSOURI AND WEST-CENTRAL ILLINOIS. DETERMINISTIC
GUIDANCE CONTINUES TO SHOW LIGHT QPF IN THE PRESENCE OF A COLD
FRONT. ALOFT, A MIDLEVEL SHORTWAVE PASSES THROUGH THE MID-
MISSISSIPPI VALLEY WITH SOME ENHANCED DIVERGENCE BENEATH THE LEFT-
EXIT REGION OF A JET STREAK ALOFT. THE LATEST LREF NOW SHOWS A
50-70% PROBABILITY FOR MEASURABLE SNOWFALL IN OUR FAR NORTHERN CWA.
RAISED POPS TO HIGH CHANCE IN THESE LOCATIONS. THE BEST SIGNAL ON
THE LREF (PROBABILITIES NEAR 90%) IS ACROSS EASTERN IOWA INTO
NORTHERN ILLINOIS. ANY SLIGHT SHIFT NORTHWARD COULD SHIFT THIS
AREA OF LIGHT SNOW OUT OF THE AREA ENTIRELY. THEREFORE, WAS NOT
CONFIDENT ENOUGH TO ADD LIKELY POPS AT THIS TIME.
SNOW AMOUNTS WOULD BE VERY LIGHT, RANGING FROM A DUSTING TO AS MUCH
AS A HALF OF AN INCH. PROBABILITIES FOR 1" OR MORE OF SNOW ARE
BASICALLY NIL ON THE LREF.
THERE HAVE BEEN A COUPLE OF NOTABLE CHANGES IN ENSEMBLE GUIDANCE FOR
THE END OF THE WEEK COMPARED TO LAST NIGHT. FOR ONE, THE SECONDARY
MIDLEVEL SHORTWAVE IS A BIT FURTHER SOUTH AND LESS ORGANIZED FOR
THURSDAY NIGHT/FRIDAY. AS A RESULT, THE CHANCES FOR ANY LIGHT
SNOW ACCUMULATIONS HAVE LESSENED. PROBABILITIES FOR MEASURABLE
SNOWFALL ON THE LREF HAVE DROPPED BELOW 10%. LAST NIGHT, THERE
WAS A BETTER SIGNAL, WITH 20-30% CHANCES FOR LIGHT SNOWFALL
ACCUMULATIONS. GIVEN CYCLONIC FLOW ALOFT, SOME FLURRIES MAY STILL
BE POSSIBLE HOWEVER. THE OTHER CHANGE IS THAT TEMPERATURES LOOK
COLDER TO END THE WEEK, WITH MEAN 850-HPA TEMPERATURES ON THE
EPS/GEFS CLOSER TO -10C. HIGHS THURSDAY/FRIDAY ARE LIKELY TO BE
IN THE 20S/30S, SOME 5 DEGREES ON AVERAGE COLDER THAN THE PREVIOUS
FORECAST. FRIDAY MORNING SHOULD BE THE COLDEST MORNING WITH THE
SURFACE RIDGE SLIDING ACROSS MISSOURI. LOWS IN THE SINGLE DIGITS
TO TEENS ARE FORECAST.
(FRIDAY NIGHT - MONDAY)
THE LATEST WPC CLUSTERS OF THE 500-HPA HEIGHT PATTERN REMAIN IN GOOD
AGREEMENT THAT ANOMALOUS TROUGHING WILL GET CARVED OUT IN THE DESERT
SOUTHWEST/BAJA CALIFORNIA REGION. FURTHER EAST, ZONAL FLOW WILL BE
IN PLACE ACROSS THE MIDSECTION OF THE COUNTRY. WE ARE STILL LOOKING
AT A COLD FRONTAL PASSAGE SOMETIME LATE SATURDAY/SATURDAY NIGHT.
THERE REMAINS A LOW POSSIBILITY THAT SOME ENERGY MAY GET EJECTED OUT
OF THE DESERT SOUTHWEST AND INTERACT WITH THIS FRONTAL BOUNDARY LATE
THIS WEEKEND TO PRODUCE SOME LIGHT RAIN/SNOW. THIS SIGNAL IS WEAK
HOWEVER AND IS ALMOST ENTIRELY CONFINED TO THE GFS/GEFS.
PROBABILITIES FOR MEASURABLE PRECIPITATION ON THE EPS/CMCE ARE LESS
THAN 10%. COMPARE THAT TO THE GEFS, WHICH SHOWS 50-80% CHANCES FOR
EAST CENTRAL AND SOUTHEAST MISSOURI AS WELL AS SOUTHWEST
ILLINOIS. GIVEN THAT THE GEFS IS ON ITS OWN, THIS IS NOT THE MOST
LIKELY SCENARIO. MAINTAINED SOME SLIGHT CHANCE/LOW CHANCE POPS,
MAINLY IN SOUTHEAST MISSOURI AND SOUTHWEST ILLINOIS WITH THIS
FORECAST PACKAGE. HOWEVER, MY GUESS IS THAT THESE POPS WILL LESSEN
AND MAY EVEN DISAPPEAR OVER THE NEXT 48 HOURS. TYPICALLY, WHEN
ONE ENSEMBLE SUITE IS SO DIFFERENT THAN THE OTHER TWO, IT IS MOST
OFTEN NOT CORRECT.
TEMPERATURE WISE, THERE IS MORE CONFIDENCE THROUGH THE WEEKEND
INTO EARLY NEXT WEEK. A SHARP WARMUP IS EXPECTED ON SATURDAY
AHEAD OF THE COLD FRONT, WITH HIGHS LIKELY IN THE 40S AREAWIDE.
SOME LOCATIONS MAY EVEN HIT THE 50 DEGREE MARK. SPREAD ON THE NBM
IS LOW FOR SATURDAY, WITH ONLY A 3-6 DEGREE INTER-QUARTILE RANGE.
BEHIND THE FRONT, A RETURN TO BELOW NORMAL TEMPERATURES IS
EXPECTED WITH HIGHS IN THE 30S.
GOSSELIN
AVIATION
(FOR THE 18Z TAFS THROUGH 18Z WEDNESDAY AFTERNOON)
ISSUED AT 1143 AM CST TUE JAN 21 2025
DRY AND VFR FLIGHT CONDITIONS WILL PREVAIL THROUGH THE TAF PERIOD AT
ALL TERMINALS WITH DEPARTING LOW-VFR STRATOCUMULUS IN THE VICINITY
OF ST. LOUIS METRO TERMINALS THIS AFTERNOON AND WAVES OF UPPER AND
MID-LEVEL CLOUDS OVERNIGHT INTO WEDNESDAY. WEST-NORTHWESTERLY WINDS
WILL BECOME SOUTHERLY TONIGHT UPON PASSAGE OF A SURFACE PRESSURE
RIDGE, OCCASIONALLY GUSTING 17 TO 22 KT BY WEDNESDAY MORNING.
PFAHLER
LSX WATCHES/WARNINGS/ADVISORIES
MO...EXTREME COLD WARNING UNTIL NOON CST TODAY FOR KNOX MO-LEWIS MO-
MARION MO-SHELBY MO.
IL...EXTREME COLD WARNING UNTIL NOON CST TODAY FOR ADAMS IL-BROWN IL.
WFO LSX
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