396
FXUS63 KLSX 152322
AFDLSX
AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE SAINT LOUIS MO
522 PM CST WED JAN 15 2025
KEY MESSAGES
- A BRIEF WARMING TREND WILL CONTINUE THROUGH FRIDAY BEFORE MUCH
COLDER AIR SETTLES INTO THE REGION EARLY NEXT WEEK.
- LIGHT RAIN IS EXPECTED (70-80%) FOR MUCH OF THE AREA FRIDAY
EVENING INTO SATURDAY MORNING. BRIEF, LIGHT SNOW MAY OCCUR ON
THE BACKSIDE OF THE SYSTEM, BUT NO ACCUMULATIONS ARE EXPECTED.
SHORT TERM
(THROUGH LATE THURSDAY NIGHT)
ISSUED AT 244 PM CST WED JAN 15 2025
THE SURFACE HIGH PRESSURE OVERHEAD THIS MORNING, THAT ALLOWED
TEMPERATURES TO DIP BELOW ZERO IN PORTIONS OF ILLINOIS, HAS SLID OFF
TO THE EAST. THIS HAS RESULTED IN LIGHT SOUTHERLY WINDS THAT HAVE
HELPED THE AREA TO WARM UP NICELY FROM THIS MORNINGS COLD LOW
TEMPERATURES.
AT 500MB, AN AMPLIFIED RIDGE IS LOCATED OVER THE WESTERN CONUS, WITH
A TROUGH OVER THE FAR NORTHEASTERN CONUS, PLACING US UNDER
NORTHWESTERLY FLOW ALOFT. WITHIN THIS FLOW REGIME, A SHORTWAVE
DISTURBANCE/CLIPPER IS DROPPING SOUTHEAST INTO THE GREAT LAKES
REGION. THE CLIPPER WILL BRING GUSTY SOUTHWEST WINDS (20KTS)
ACCOMPANIED BY INCREASING MID-HIGH LEVEL CLOUDS OVERNIGHT. THE
ENTIRE AREA WILL REMAIN DRY TONIGHT WITH THE GREATEST MID-LEVEL
FORCING AND MOISTURE FAR OFF TO THE NORTHEAST OVER THE GREAT LAKES.
WITH GUSTY SOUTHWESTERLY WINDS IN PLACE TONIGHT, TEMPERATURES ARE
EXPECTED TO BEGIN WARMING SLIGHTLY AFTER MIDNIGHT, REACHING THE MID-
UPPER 20S NORTH OF I-70 AND LOW 30S SOUTH OF I-70 BY MORNING. WITH
PLENTY OF SOLAR INSOLATION EXPECTED TOMORROW, ESPECIALLY FOR
LOCATIONS WEST OF THE MISSISSIPPI RIVER, TEMPERATURES WILL WARM INTO
THE MID 30S FOR OUR NORTHERN COUNTIES WHILE SOUTHERN PORTIONS OF THE
AREA WILL REACH THE MID-UPPER 40S BY THE AFTERNOON. THEREFORE,
TOMORROW WILL BE AN EFFICIENT DAY FOR SNOW MELT FOR AREAS WITH SNOW
PACK, ESPECIALLY FOR LOCATIONS THAT REMAIN CLOUD FREE THE ENTIRE DAY.
A SURFACE RIDGE BUILDS INTO THE AREA WITH ITS AXIS PASSING OVERHEAD
THURSDAY EVENING AND TO THE EAST OF US BY THURSDAY NIGHT, PLACING
THE REGION UNDER WEAK LOW-LEVEL SOUTHERLY FLOW. THE WARMER SOUTHERLY
WINDS COUPLED WITH THE EXISTING SNOW PACK COULD LEAD TO THE
FORMATION OF ADVECTION FOG AS THE WARMER MOIST AIR MOVES OVER THE
COLDER SNOW PACK. OUR CONFIDENCE IN THE COVERAGE AND MAGNITUDE OF
FOG REMAINS LOW AT THIS TIME MAINLY DUE TO THE UNCERTAINTY IN
REGARDS TO THE AMOUNT OF SNOW MELT THAT WILL OCCUR BEFORE
TOMORROW NIGHT. WITH OVERNIGHT LOW TEMPERATURES THURSDAY NIGHT
EXPECTED TO BE BELOW FREEZING, IN THE MID-UPPER 20S ACROSS THE
CWA, THERE REMAINS THE POTENTIAL FOR LIGHT FROST FORMATION, THAT
COULD LEAD TO A FEW SLICK SPOTS ON FRIDAY MORNING.
PEINE
LONG TERM
(FRIDAY THROUGH NEXT WEDNESDAY)
ISSUED AT 244 PM CST WED JAN 15 2025
FRIDAY WILL BE THE WARMEST DAY OF THE WEEK BY FAR AS DEEP WARM AIR
ADVECTION TAKES HOLD OF OUR SENSIBLE WEATHER. SOUTHWEST WINDS ON THE
BACKSIDE OF A LOW TO MID-LEVEL RIDGE WILL ENHANCE ONGOING WARM AIR
ADVECTION, ALLOWING THE REGION TO WARM TO ABOVE AVERAGE (AVERAGE
BEING NEAR 40 DEGREES) FOR THE FIRST TIME IN WHAT MAY FEEL LIKE TOO
LONG FOR SOME. HIGHS ON FRIDAY ARE FORECAST TO REACH THE 40S
AREAWIDE, WITH PORTIONS OF CENTRAL AND SOUTHEAST MISSOURI
POTENTIALLY SEEING LOW-50S. CONFIDENCE WAVERS IN THIS, HOWEVER, DUE
TO INCREASING CLOUD COVER THROUGH THE DAY. IF CLOUDS ARRIVE EARLIER,
THEY MAY CAP TEMPERATURES BEFORE ANY LOCATION IS ABLE TO SEE 50
DEGREES. REGARDLESS OF THE EXACT HIGH TEMPERATURE, WE'RE LIKELY TO
SEE A NOTABLE CHANGE IN THE AMOUNT OF LINGERING SNOW AND ICE ON
FRIDAY.
THE AFOREMENTIONED CLOUD COVER WILL ENTER THE CWA AHEAD OF A
SHORTWAVE NEARING THE OHIO VALLEY FROM THE SOUTHWEST. AS IT DOES, IT
WILL MEET A COLD FRONT INCOMING FROM THE NORTHWEST. THE FORCING
ASSOCIATED WITH THE FRONT, ABUNDANT LOW TO MID-LEVEL MOISTURE, AND
LIFT FROM THE SHORTWAVE WILL CULMINATE IN A WIDESPREAD PRECIPITATION
EVENT FOR FRIDAY EVENING INTO SATURDAY MORNING. THE PRECIPITATION
TYPE IS STILL EXPECTED TO BE MAJORITY RAIN AHEAD OF THE COLD FRONT.
THE MAGNITUDE OF THE WARMTH AHEAD OF THE COLD FRONT WILL ENSURE THIS
HOLDS TRUE. THE ONLY UNCERTAINTY LIES IN ANY PRECIPITATION LINGERING
BEHIND THE COLD FRONT. AS MENTIONED IN PREVIOUS DISCUSSIONS, THE
CHANCE FOR IMPACTFUL WINTRY PRECIPITATION BEHIND THE FRONT IS VERY
LOW. DESPITE COLD AIR MOVING IN, MID-LEVEL ASCENT DIMINISHES QUICKLY
ON THE BACKSIDE OF THE FRONT, AND THE AIR DRIES VERY QUICKLY.
SOUNDING DATA SHOWS THAT THERE IS A SHORT WINDOW FOR SNOW AS THE
COLUMN DE-SATURATES ALMOST IMMEDIATELY AFTER THE FRONTAL PASSAGE.
ERGO, ANY SNOW THAT FALLS EARLY SATURDAY MORNING IS EXPECTED TO
BE BRIEF AND LIGHT. ACCUMULATIONS ARE NOT EXPECTED DUE TO THE
GROUND STILL BEING WARM FROM THE PREVIOUS DAYS.
THE MOST IMPACTFUL PERIOD OF THE NEXT SEVEN DAYS WILL BEGIN SUNDAY
MORNING AS WIND CHILLS TUMBLE BENEATH THE ZERO MARK FOR MOST OF THE
NORTHERN HALF OF THE CWA. THIS IS OUR FORECAST FOR EACH SUBSEQUENT
MORNING THROUGH WEDNESDAY, WITH TUESDAY MORNING POTENTIALLY BEING
THE COLDEST. AT THE TIME OF WRITING, NO LOCATION MEETS THE CRITERIA
FOR A COLD WEATHER ADVISORY, BUT PORTIONS OF NORTHEAST MISSOURI AND
WEST-CENTRAL ILLINOIS COME CLOSE. DESPITE THE LACK OF ADVISORY
CRITERIA TEMPERATURES, IT'S IMPORTANT TO NOTE THAT THE COLDEST
LOCATIONS MAY NOT EXPERIENCE WIND CHILLS ABOVE ZERO AT ANY TIME FROM
SUNDAY MORNING THROUGH WEDNESDAY. THE LACK OF A HEADLINE SHOULD NOT
UNDERMINE THE SERIOUSNESS OF PROLONGED COLD WEATHER, ESPECIALLY FOR
INDIVIDUALS WITHOUT THE MEANS TO WARM THEMSELVES IN SUCH CONDITIONS.
OVERALL, THE MAGNITUDE AND LONGEVITY OF THE COLD WILL DEPEND ON THE
STRENGTH, TRACK, AND SPEED OF SURFACE HIGH PRESSURE BUILDING INTO
THE REGION EARLY NEXT WEEK. A STRONGER, SLOWER HIGH THAT TRACKS
DIRECTLY THROUGH OUR CWA WILL RESULT IN COLDER TEMPERATURES FOR A
LONGER PERIOD AND VICE VERSA. THERE IS REASONABLE CONFIDENCE IN A
WARM-UP BEGINNING IN THE MIDDLE OF THE WEEK, AS REFLECTED BY THE NBM
INTERQUARTILE RANGE. THE 75TH PERCENTILE HIGH TEMPERATURE OF 27
DEGREES ON TUESDAY IS LESS THAN WEDNESDAY'S 25TH PERCENTILE HIGH
TEMPERATURE OF 30 DEGREES. ALTHOUGH WEDNESDAY DOES HAVE A 9 DEGREE
TEMPERATURE SPREAD, IT'LL LIKELY STILL BE A WARMER DAY THAN TUESDAY
WILL BE. JUST HOW MUCH IT WILL WARM IS STILL UNCERTAIN.
JAJA
AVIATION
(FOR THE 00Z TAFS THROUGH 00Z THURSDAY EVENING)
ISSUED AT 520 PM CST WED JAN 15 2025
SOUTHERLY WINDS BECOME SOUTHWESTERLY TONIGHT AND STRENGTHEN AS A
COLD FRONT APPROACHES. SOME INCREASING CLOUDS ARE LIKELY THROUGH
THE NIGHT BUT SHOULD REMAIN WELL WITHIN VFR RANGE. WINDS SHIFT TO
WESTERLY ON THURSDAY AND WEAKEN AS THE PRESSURE GRADIENT RELAXES
WITH THE APPROACH OF THE HIGH PRESSURE AXIS FROM THE WEST.
KIMBLE
LSX WATCHES/WARNINGS/ADVISORIES
MO...NONE.
IL...NONE.
WFO LSX
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