554
FXUS63 KLSX 172039
AFDLSX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAINT LOUIS MO
239 PM CST FRI JAN 17 2025
KEY MESSAGES
- TEMPERATURES WILL LIKELY DROP THROUGH MOST OF THE DAY SATURDAY WITH
AFTERNOON HIGHS ONLY REACHING THE 20S - 30S. BY SUNDAY,
WIDESPREAD HIGHS IN THE TEENS ARE FORECAST WITH WIND CHILLS
BELOW ZERO FOR MOST OF THE REGION. THIS BITTER COLD WILL REMAIN
IN PLACE UNTIL MID-WEEK.
- A COLD FRONT WILL BRING WIDESPREAD RAIN TO THE AREA THIS
EVENING, WITH THE HIGHEST CHANCE FOR RAIN (80-100%) BEING IN
SOUTHEAST MISSOURI AND SOUTHWEST ILLINOIS. A FEW BRIEF
SNOWFLAKES ARE POSSIBLE ON THE BACK EDGE OF THE RAIN, BUT NO
ACCUMULATION IS EXPECTED.
SHORT TERM
(THROUGH LATE SATURDAY NIGHT)
ISSUED AT 222 PM CST FRI JAN 17 2025
WATER VAPOR ANALYSIS SHOWS A LONGWAVE TROUGH DIGGING INTO THE
NORTHERN PLAINS FROM CENTRAL CANADA. ITS ASSOCIATED COLD FRONT
CURRENTLY EXTENDS FROM THE GREAT LAKES INTO WYOMING, AND IT
CONTINUES TO PUSH SOUTHEAST AS ITS PARENT TROUGH DEEPENS. THIS COLD
FRONT WILL PASS THROUGH OUR AREA BETWEEN THIS EVENING AND SATURDAY
MORNING, PUTTING A QUICK END TO THE WARMTH WE EXPERIENCED YESTERDAY
AND TODAY. AS DRY, ARCTIC AIR RUSHES IN BEHIND THE COLD FRONT,
TEMPERATURES WILL QUICKLY PLUMMET. OVERALL HIGH TEMPERATURES ON
SATURDAY WILL OCCUR NEAR MIDNIGHT (30S AND 40S), WITH TEMPERATURES
DECREASING THROUGH THE MORNING AND RISING SLIGHTLY IN THE AFTERNOON.
AFTERNOON TEMPERATURES ARE ONLY EXPECTED TO REACH THE 20S AND 30S.
THIS IS 20 TO 30 DEGREES COLDER THAN TODAY'S HIGH TEMPERATURES, AND
ELEVATED WINDS WILL MAKE IT FEEL 10+ DEGREES COLDER THAN THAT.
JUST AHEAD OF THE FRONT, WIDESPREAD LIGHT RAIN IS EXPECTED TO BEGIN
THIS EVENING AS A SHORTWAVE ENTERS THE OHIO RIVER VALLEY AND
PROVIDES LIFT TO THE REGION. CONFIDENCE IS VERY HIGH IN RAIN BEING
THE DOMINANT PRECIPITATION TYPE, AS TEMPERATURES WILL BE WELL ABOVE
FREEZING FOR THE BULK OF THE EVENT. THERE IS A POSSIBILITY OF A
BRIEF CHANGEOVER TO SNOW BEHIND THE FRONT, BUT WITH WARM GROUND
TEMPERATURES AND RAPIDLY DRYING MID-LEVELS, NO ACCUMULATION IS
EXPECTED. THE RAIN AND COLD FRONT WILL EXIT THE AREA EARLY SUNDAY
MORNING, LEAVING US WITH BITTER COLD AND DRY WEATHER TO LOOK FORWARD
TO FOR THE EARLY HALF OF NEXT WEEK.
JAJA
LONG TERM
(SUNDAY THROUGH NEXT FRIDAY)
ISSUED AT 222 PM CST FRI JAN 17 2025
ALTHOUGH SATURDAY'S STARK TEMPERATURE DROP WILL BE A SHOCK TO THE
SYSTEM, WE'LL BE WISHING FOR A RETURN TO THOSE TEMPERATURES BY
SUNDAY MORNING. THE ARCTIC POST-FRONTAL AIRMASS WILL CAUSE MORNING
LOWS TO DIP INTO THE SINGLE DIGITS FOR MUCH OF THE NORTHERN HALF OF
THE CWA, WITH THE SOUTHERN HALF FORECAST TO FALL INTO THE LOW TEENS.
THE WIND CHILL WILL BE BITTERLY COLD AS MOST OF THE REGION WILL FALL
BELOW THE ZERO MARK. CONDITIONS WILL BARELY IMPROVE DURING THE DAY
AS ELEVATED WINDS PERSIST. AFTERNOON HIGHS ARE FORECAST TO RANGE
FROM 10 TO 20 DEGREES WITH SIMILAR WIND CHILLS TO THAT MORNING. THIS
GENERAL FORECAST HOLDS TRUE FOR MONDAY, TUESDAY, AND WEDNESDAY
MORNING AS WELL. TUESDAY IS EXPECTED TO BE THE COLDEST DAY OF THE
WEEK. SURFACE HIGH PRESSURE WILL BE PASSING THAT DAY, THOUGH TIMING
IS STILL UNCERTAIN. MOST DETERMINISTIC GUIDANCE SHOWS THE HIGH
PASSING OUR CWA DURING THE AFTERNOON. IF ITS CENTER PASSES EARLIER,
SAY DURING THE EARLY MORNING, RADIATIONAL COOLING WILL LIKELY PLAY A
LARGER ROLE IN HOW MUCH WE COOL THAT NIGHT. THIS IS RELEVANT BECAUSE
OUR FORECAST WIND CHILLS ON TUESDAY MORNING ARE ALREADY PUSHING COLD
WEATHER ADVISORY CRITERIA. IF RADIATIONAL COOLING PROVES MORE
EFFICIENT THAN FORECAST, IT MAY PUSH THOSE WIND CHILLS INTO ADVISORY
TERRITORY. IT'S SOMETHING THAT WILL CONTINUE TO BE WATCHED OVER THE
COMING DAYS.
CONFIDENCE IS STILL HIGH IN A MID-WEEK WARM UP, THOUGH THERE'S STILL
A WIDE SPREAD IN THE 25TH - 75TH NBM PERCENTILE RANGE. THIS LIKELY
REPRESENTS HIGH CONFIDENCE IN A WARM-UP, BUT LESSER CONFIDENCE IN
WHEN THE WARM AIR WILL ACTUALLY GET HERE. AN EARLIER ARRIVAL WOULD
MAKE FOR A WARMER WEDNESDAY, WHEREAS A LATER ARRIVAL WOULD MAKE FOR
A COOLER ONE. REGARDLESS OF IF THE HIGH IS 30 OR 40 DEGREES AT KSTL,
IT WILL BE A SIGNIFICANT WARM-UP FROM THE COLD THAT WILL PLAGUE THE
EARLY WEEK.
SUNDAY THROUGH LATE WEEK IS FORECAST TO BE LARGELY DRY AS LOW-LEVEL
HIGH PRESSURE BLOCKS MOISTURE FROM THE REGION. THERE IS A POTENTIAL
FOR FLURRIES LATE SATURDAY NIGHT INTO EARLY SUNDAY MORNING IN
SOUTHEAST MISSOURI AND SOUTHWEST ILLINOIS, BUT THESE WILL BE
UNIMPACTFUL. OUR NEXT BEST CHANCE AT SEEING PRECIPITATION WILL BE
WEDNESDAY INTO THURSDAY AHEAD OF ANOTHER COLD FRONT. THIS COLD FRONT
LOOKS PRETTY UNIMPACTFUL, ESPECIALLY COMPARED TO THE ONE MOVING
THROUGH TONIGHT. OVER 75% OF LREF MEMBERS KEEP THE REGION DRY DURING
THAT TIME FRAME. THIS ALSO ACCOUNTS FOR DIFFERENCES IN TIMING AND
TRACK OF THE SYSTEM, BUT AS OF NOW OUR FORECAST REMAINS DRY. IF
PRECIPITATION DOES OCCUR, TEMPERATURES NEAR THE FREEZING MARK MAKE
IT DIFFICULT TO PIN DOWN THE DOMINANT PRECIPITATION TYPE THIS FAR
OUT. THE FRONT WILL NOT HAVE A SURGE OF COLD AIR BEHIND IT, SO
TEMPERATURES ARE EXPECTED TO REMAIN STEADY BEHIND ITS PASSAGE.
JAJA
AVIATION
(FOR THE 18Z TAFS THROUGH 18Z SATURDAY AFTERNOON)
ISSUED AT 1121 AM CST FRI JAN 17 2025
A COLD FRONT WILL ARRIVE IN NORTHEAST MISSOURI THIS EVENING,
PASSING SOUTHEAST THROUGH THE CWA AND EXITING AROUND SUNRISE
SATURDAY. AHEAD OF THE FRONT, WIDESPREAD LIGHT RAIN AND MVFR TO
IFR CEILINGS ARE EXPECTED. THE LIGHT RAIN IS EXPECTED TO PRODUCE
REDUCED VISIBILITIES THIS EVENING AS WELL. BEHIND THE FRONT, WINDS
WILL BECOME GUSTY AND QUICKLY SHIFT TO NORTHWESTERLY. REDUCED
CEILINGS WILL QUICKLY IMPROVE TO VFR BEHIND THE FRONT, AND VFR
CONDITIONS WILL PREVAIL FOR THE REST OF THE DAY ON SATURDAY.
JAJA
LSX WATCHES/WARNINGS/ADVISORIES
MO...NONE.
IL...NONE.
WFO LSX
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