035
FXUS63 KLSX 282357
AFDLSX
AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE SAINT LOUIS MO
557 PM CST TUE JAN 28 2025
KEY MESSAGES
- MILD TEMPERATURES IN THE MID 40S TO MID 50S WILL CONTINUE
THROUGH THE END OF THE WEEK.
- RAIN WILL OVERSPREAD THE AREA THURSDAY MORNING AND CONTINUE
THROUGH FRIDAY. THE HIGHEST AMOUNTS OF RAIN ARE EXPECTED ACROSS
SOUTHEAST MISSOURI AND SOUTHWEST ILLINOIS. TOTAL RAINFALL OF AN
INCH OR MORE IS LIKELY IN THESE AREAS.
SHORT TERM
(THROUGH LATE WEDNESDAY NIGHT)
ISSUED AT 219 PM CST TUE JAN 28 2025
A BROAD UPPER LEVEL LONG WAVE TROUGH REMAINS OVER EASTERN NORTH
AMERICA TODAY. WATER VAPOR IMAGERY IS SHOWING A SHORT WAVE OVER
SOUTH CENTRAL CANADA EMBEDDED IN THE FLOW AROUND THE LONG WAVE. THIS
SHORT WAVE WILL DIVE SOUTHEAST ACROSS THE GREAT LAKES THROUGH
WEDNESDAY MORNING. A RIDGE OF HIGH PRESSURE LIES TO OUR SOUTH ALONG
THE GULF COAST, AND THE PRESSURE GRADIENT BETWEEN THE HIGH TO OUR
SOUTH AND THE SURFACE REFLECTION OF THE SHORT WAVE TO OUR NORTH IS
PRODUCING WARM WESTERLY FLOW. THE WARM DRY PATTERN WILL CONTINUE
THROUGH WEDNESDAY, ALTHOUGH WINDS WILL BECOME LIGHT AND VARIABLE BY
EARLY WEDNESDAY MORNING AS THE RIDGE AXIS SHIFTS FROM A EAST-WEST
ORIENTATION ALONG THE GULF COAST TO A MORE NORTH-SOUTH ORIENTATION
ALONG THE MISSISSIPPI VALLEY. TEMPERATURES WILL CONTINUE ABOVE
NORMAL WITH HIGHS IN THE UPPER 40S TO MID 50S AND LOWS IN THE LOW TO
MID 30S.
CARNEY
LONG TERM
(THURSDAY THROUGH NEXT TUESDAY)
ISSUED AT 219 PM CST TUE JAN 28 2025
THE LARGE CUT OFF UPPER LOW WHICH IS CURRENTLY SPINNING OVER THE
DESERT SOUTHWEST WILL BE CREEPING EASTWARD OVER THE NEXT DAY AND
HALF, AND SHOULD BE CENTERED OVER EASTERN COLORADO OR WESTERN KANSAS
BY 12Z WEDNESDAY MORNING. MEANWHILE, THE SURFACE RIDGE WILL ALSO BE
DRIFTING EAST WHICH TURNS LOW LEVEL FLOW ALONG THE GULF BACK TO A
SOUTHERLY DIRECTION, OPENING IT UP FOR MOISTURE TRANSPORT. THE LOW
LEVEL CYCLOGENESIS OVER THE PLAINS PRODUCES A STRONG LOW LEVEL JET
WHICH DRAWS THIS MOISTURE UP INTO THE MID MISSISSIPPI VALLEY BY
THURSDAY MORNING. DETERMINISTIC GUIDANCE SHOWS MODERATE TO STRONG
MOISTURE CONVERGENCE ON THE NOSE OF THIS LOW LEVEL JET, WHICH GETS
AS STRONG AS 50-60KTS. DETERMINISTIC GUIDANCE BRINGS PRECIPITABLE
WATER VALUES UP TO 1-1.25 INCHES ACROSS MOST OF THE FORECAST AREA,
AND THIS JIVES WELL WITH BOTH GEFS AND ENS MEAN VALUES. THIS IS UP
AROUND THE 99TH PERCENTILE OF NORMAL CLIMATE P-WAT VALUES FOR THIS
TIME OF YEAR. WPC QPF FOR THURSDAY THROUGH FRIDAY RANGES FROM 0.50
TO ALMOST 2 INCHES FROM NORTH TO SOUTH ACROSS THE AREA. THIS LOOKS
REASONABLE GIVEN THE FORCING AND AVAILABLE MOISTURE, AND IS ALSO
SOMEWHERE IN BETWEEN THE LREF MEAN AND 75TH PERCENTILE QPF. LUCKILY,
TEMPERATURES SHOULD BE WELL ABOVE FREEZING IN THE 40S+ FOR THURSDAY
AND FRIDAY, SO NO FREEZING/FROZEN PRECIPITATION IS EXPECTED.
THE LOW EXITS THE REGION BY LATE FRIDAY AFTERNOON/EARLY EVENING
BRINGING PRECIP TO AN END. ZONAL FLOW ALOFT DOMINATES THE WEEKEND
WEATHER PATTERN WHICH WILL HELP CONTINUE OUR LATE JANUARY THAW.
MEDIUM RANGE GUIDANCE SHOWS 850MB TEMPERATURES REACHING UP TO 4-8C
SATURDAY, AND THE ECMWF PUSHES IT UP TO 12-14C ON SUNDAY. HOWEVER,
THE GFS SHOWS A FAST-MOVING SHORT WAVE TROUGH MOVING ACROSS THE
MISSISSIPPI VALLEY SATURDAY NIGHT, WHICH PRODUCES A WEAK SURFACE LOW
THAT DRAGS A COLD FRONT SOUTH THROUGH THE FORECAST AREA ON SUNDAY.
THE EC ALSO SHOWS THE SHORTWAVE, BUT LITTLE IF ANY SURFACE
REFLECTION AND NO COLD FRONT UNTIL AT LEAST NEXT TUESDAY. OBVIOUSLY
THESE DIFFERENCES WILL HAVE A LARGE IMPACT ON TEMPERATURES FOR THIS
PERIOD. INDEED, THE LREF INTERQUARTILE HIGH TEMPERATURE RANGE AT
LAMBERT ON MONDAY IS 13 DEGREES, AND ON TUESDAY IT'S 10 DEGREES.
LOOKING DEEPER, MOST OF THE ENSEMBLE MEMBERS ARE LATCHING ON TO
COLDER TEMPERATURES FOR MONDAY AND TUESDAY, SO THE COLDER FORECAST
OF THE NBM IS REASONABLE. HOWEVER, MY CONFIDENCE IN THE ACTUAL
VALUES IN THE FORECAST IS LOW AT THIS TIME.
CARNEY
AVIATION
(FOR THE 00Z TAFS THROUGH 00Z WEDNESDAY EVENING)
ISSUED AT 549 PM CST TUE JAN 28 2025
VFR CONDITIONS ARE EXPECTED THROUGHOUT THE 00Z TAF PERIOD. THE
PRIMARY CONCERN IS THE POTENTIAL FOR 3 TO 6 HOURS OF LOW LEVEL
WIND SHEAR AT THE START OF THE PERIOD, DUE TO STRENGTHENING WEST
TO NORTHWEST WINDS JUST ABOVE THE SURFACE. WINDS WILL INCREASE
SHARPLY WITH HEIGHT, REACHING NEARLY 50 KNOTS BETWEEN 1500 AND
2000 FEET ABOVE GROUND LEVEL. MEANWHILE, THERE MAY ALSO BE A
SLIGHT DIRECTIONAL SHIFT BETWEEN WESTERLY SURFACE WINDS AND
NORTHWESTERLY WINDS ALOFT. THE MAGNITUDE OF THIS LLWS WILL DEPEND
LARGELY WHETHER SURFACE WINDS DECOUPLE AND WEAKEN, WHICH WOULD
INCREASE THE WIND SHEAR. THIS WILL LIKELY VARY BY LOCATION AND
FLUCTUATE, BUT IT HAS BEEN INCLUDED IN ALL LOCAL TAF SITES.
WIND SHEAR IS LIKELY TO DIMINISH BETWEEN 06-08Z, AND SURFACE WINDS
WILL CONTINUE TO WEAKEN TO NEARLY CALM AND VARIABLE BY LATE
TOMORROW MORNING.
BRC
LSX WATCHES/WARNINGS/ADVISORIES
MO...NONE.
IL...NONE.
WFO LSX
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