047
FXUS63 KLSX 240437
AFDLSX
AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE SAINT LOUIS MO
1037 PM CST THU JAN 23 2025
KEY MESSAGES
- COLD, BELOW NORMAL, TEMPERATURES WILL DOMINATE TONIGHT THROUGH
FRIDAY.
- A PATTERN CHANGE IS EXPECTED TO BRING AN OVERALL MILDER PATTERN
STARTING THIS WEEKEND INTO NEXT WEEK. WITH THE EXCEPTION OF
SUNDAY, TEMPERATURES WILL LARGELY BE ABOVE SEASONAL AVERAGES.
SHORT TERM
(THROUGH LATE FRIDAY NIGHT)
ISSUED AT 141 PM CST THU JAN 23 2025
THE LAST IN A SERIES OF SHORT-WAVE TROFS TRANSLATING THROUGH THE
MOBILE LONGWAVE TROF WILL MOVE THROUGH THE AREA LATER TONIGHT INTO
EARLY FRIDAY MORNING. IT WILL PROMPT THE ELONGATED SURFACE
HIGH/RIDGE CURRENTLY LOCATED IN THE HIGH PLAINS TO MOVE INTO THE
AREA, CENTERED THROUGH THE CWA AT 12Z FRIDAY. THE COMBO OF
CLEAR SKIES AND LIGHT WINDS ATTENDANT WITH THE SURFACE RIDGE
SHOULD YIELD DECENT RADIATIONAL COOLING WITH WELL-BELOW NORMAL
TEMPS (10-15+ BELOW NORMAL) AND MINS LARGELY IN THE SINGLE DIGITS.
IN THE WAKE OF THE FRIDAY MORNING SHORT-WAVE TROF PASSAGE, A
SIGNIFICANT PATTERN CHANGE IS STILL FORECAST TO ENSUE WITH LARGE
HEIGHT RISES ALOFT AS THE MID-UPPER FLOW FLATTENS ACROSS THE
MIDDLE MISSISSIPPI VALLEY AND A STRONG UPPER TROF DIGS ALONG THE
WEST COAST. LOW-LEVEL WAA SHOULD GET UNDERWAY RATHER QUICKLY
FRIDAY AS A RESULT WITH BACKING WINDS IN THE LOWEST FEW KM. WHILE
TEMPERATURES WILL MODIFY OVER THE CHILLY READINGS OF TODAY/TONIGHT,
THEY WILL STILL BE BELOW NORMAL. HOW MUCH WARMING IS ALWAYS THE
CHALLENGE IN THESE SET-UPS AND WE TYPICALLY UNDER FORECAST THIS
MODERATION. THERE WILL ALSO BE INCREASING HIGH CLOUDS TO CONTEND
WITH AS WE HEAD THROUGH THE AFTERNOON. IN LIGHT OF PAST PERFORMANCE
I HAVE NUDGED THE FORECAST UP A TAD TO VALUES WITHIN THE UPPER
QUARTILE OF THE NBM TEMPERATURE GUIDANCE.
GLASS
LONG TERM
(SATURDAY THROUGH NEXT THURSDAY)
ISSUED AT 141 PM CST THU JAN 23 2025
THE PATTERN CHANGE WILL CONTINUE TO EVOLVE OVER THE COMING
WEEKEND WITH A SPLIT FLOW FEATURING A DEEPENING CLOSED LOW/TROF ON
THE WEST COAST, QUASI-ZONAL FLOW THROUGH THE MID-MISSISSIPPI
VALLEY, AND A NEW LONGWAVE TROF OOZING SOUTHWARD OVER EASTERN
NOAM. INITIALLY WE WILL SEE CONTINUED LOW-LEVEL WAA ON SATURDAY
WITH SOUTHWEST-WESTERLY LOWER TROPOSPHERIC FLOW. THEN AS THE
EASTERN TROF BEGINS OOZING SOUTHWARD, THIS WILL SEND A COLD FRONT
THROUGH THE AREA LATE SATURDAY AFTERNOON-NIGHT. A GOOD DEAL OF
HIGH CLOUDINESS IS FORECAST ON SATURDAY WITHIN THE QUASI-ZONAL
FLOW AND THIS COULD HAMPER THE MAGNITUDE OF THE WARM-UP. HIGHS
STILL LOOK ABOVE NORMAL WITH MOST AREAS IN THE 40S, HOWEVER
THICKER CLOUDS AND A SLIGHTLY FASTER FROPA IN NE MO AND WC IL MAY
HOLD HIGHS IN THE UPPER 30S.
ON SUNDAY WE SHOULD BE UNDER THE INFLUENCE OF INCREASING NORTHWEST
FLOW ALOFT AND A WEAK WEST-EAST ELONGATED POST-FRONTAL SURFACE HIGH
RESULTING IN A BRIEF RETURN OF COOLER TEMPERATURES. BY MONDAY THIS
WEAKENING SURFACE HIGH IS TO OUR SOUTH AND WE GET BACK INTO WEST-
SOUTHWEST LOW-LEVEL FLOW AND WAA ON THE POLEWARD SIDE OF THE HIGH.
THIS SHOULD ALLOW FOR A RETURN OF ABOVE NORMAL TEMPERATURES. THE NBM
MAX TEMPERATURE GUIDANCE FOR MONDAY HAS A SMALL INTERQUARTILE RANGE
(IQR) WHICH IS DISTRIBUTED ENTIRELY ABOVE NORMAL, SUPPORTING HIGHS
IN THE 40S.
CONTINUED EQUATORWARD DEEPENING OF THE EASTERN NOAM LONGWAVE TROF
WILL RESULT IN NORTHWEST FLOW ACROSS THE REGION THROUGH MIDWEEK,
HOWEVER THERE ARE MODEL/ENSEMBLE DIFFERENCES ON THE STRENGTH OF THE
TROFING, MAGNITUDE OF OUR HEIGHTS ALOFT, AND PRESENCE OF WEAK
TRANSIENT SURFACE TROFS OR FRONTS THAT COULD ALTER THE TEMPERATURE
ADVECTION BOTH TUESDAY AND WEDNESDAY. THE NBM TEMPERATURE
GUIDANCE CURRENTLY SUPPORTS ABOVE NORMAL TEMPERATURES WITH THE IQR
REMAINING ABOVE NORMAL, HOWEVER THE SPREAD BETWEEN THE 25-75TH
PERCENTILE GROWS TO 10+ DEGREES.
DRY WEATHER IS EXPECTED FOR THE WEEKEND UNTIL ABOUT MIDWEEK.
SOMETIME IN THE LATE WEDNESDAY-LATE THURSDAY TIME FRAME WE MIGHT
SEE THE CHANCE OF PRECIPITATION RETURN ATTENDANT WITH THE
EVENTUAL PROGRESSION OF THE WESTERN U.S. UPPER LOW/TROF INTO THE
NATION'S MIDSECTION.
GLASS
AVIATION
(FOR THE 06Z TAFS THROUGH 06Z FRIDAY NIGHT)
ISSUED AT 1035 PM CST THU JAN 23 2025
VFR CONDITIONS WILL PREVAIL THROUGH THE TAF PERIOD. LIGHT AND
VARIABLE WINDS WILL INCREASE FROM THE SOUTHWEST LATE FRIDAY
MORNING AND REMAIN STEADILY AROUND 10 KTS THROUGH THE REST OF THE
PERIOD. LLWS MAY BE A CONCERN FRIDAY NIGHT, ESPECIALLY IN MID-
MISSOURI THROUGH WEST-CENTRAL ILLINOIS WHERE A NOCTURNAL ~45 KT LLJ
IS FORECAST TO STRENGTHEN. HOWEVER, CONFIDENCE IN IMPACTS IS TOO
LOW TO INCLUDE IN THE TAFS DURING THIS PACKAGE.
JAJA
LSX WATCHES/WARNINGS/ADVISORIES
MO...NONE.
IL...NONE.
WFO LSX
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