047
FXUS63 KLSX 292034
AFDLSX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAINT LOUIS MO
234 PM CST WED JAN 29 2025
KEY MESSAGES
- RAIN WILL OVERSPREAD THE AREA FROM THE SOUTHWEST LATE TONIGHT
INTO THURSDAY MORNING. A FEW THUNDERSTORMS ARE POSSIBLE AS WELL.
WHILE MOST OF THE RAIN IS EXPECTED THURSDAY INTO THURSDAY
EVENING, THE CHANCE FOR RAIN WILL CONTINUE UNTIL FRIDAY
AFTERNOON.
- THE HEAVIEST RAINFALL OF BETWEEN 1 AND 2 INCHES IS EXPECTED
ACROSS SOUTHEAST MISSOURI.
- MILD AND DRY WEATHER RETURNS FOR THE WEEKEND.
SHORT TERM
(THROUGH LATE THURSDAY NIGHT)
ISSUED AT 216 PM CST WED JAN 29 2025
A LARGE CUT OFF UPPER LOW CURRENTLY CENTERED SOUTH OF THE FOUR
CORNERS REGION ALONG THE ARIZONA/NEW MEXICO BORDER WILL DRIFT INTO
THE SOUTHERN PLAINS NEAR THE OKLAHOMA PANHANDLE BY 12Z THURSDAY
MORNING. 850MB FLOW TURNS TO THE SOUTHWEST AS THE LOW LEVEL TROUGH
STRENGTHENS OVER THE PLAINS LATE TONIGHT AND TRANSPORTS DEEP GULF
MOISTURE UP INTO THE MID MISSISSIPPI VALLEY BY EARLY TOMORROW
MORNING. GUIDANCE CONTINUES TO SHOW MODERATE TO STRONG MOISTURE
CONVERGENCE ON THE NOSE OF A 50+ KT LOW LEVEL JET THURSDAY WITH
PRECIPITABLE WATER VALUES WELL OVER CLIMATOLOGY AT 1-1.5 INCHES.
THIS WILL PRODUCE WIDESPREAD RAINFALL ON THURSDAY, WITH THE AXIS OF
HEAVIEST RAIN ACROSS SOUTHEAST MISSOURI WHERE 1.5-2 INCHES IS
POSSIBLE. THERE WILL LIKELY BE A BREAK IN THE STEADIER RAIN BEHIND
THE SURFACE COLD FRONT ON THURSDAY NIGHT AS THE LOW LEVEL SYSTEM
WRAPS DRIER AIR IN FROM THE PLAINS, HOWEVER THERE WILL CONTINUE TO
BE A CHANCE FOR INTERMITTENT RAIN UNTIL THE UPPER LEVEL LOW MOVES
EAST OF THE MISSISSIPPI RIVER FRIDAY AFTERNOON.
THE AXIS OF HEAVIEST RAIN HAS MOVED FARTHER SOUTH THAN IN PREVIOUS
FORECASTS, AND THE 2+ INCH PLUS AREA IS NOW OUT OF OUR FORECAST AREA
ACROSS FAR SOUTHEAST MISSOURI. I HAVE THEREFORE DECIDED TO HOLD OFF
ISSUING ANY FLOOD WATCHES DUE TO THE DOWNWARD TREND IN QPF. GUIDANCE
IS SHOWING UP TO 200-500 J/KG MUCAPE AT TIMES AT LEAST UNTIL THE
WARM ADVECTION WING OF THE SYSTEM MOVES EAST OF THE AREA THURSDAY
NIGHT, SO A SLIGHT CHANCE FOR THUNDERSTORMS REMAINS IN THE FORECAST.
WHILE THERE WILL BE PLENTY OF SHEAR FOR ANY STORMS TO WORK WITH,
GUIDANCE IS SHOWING LITTLE IF ANY SBCAPE, AND WHEN THERE IS SURFACE
INSTABILITY IT'S CAPPED, SO SEVERE STORMS ARE NOT EXPECTED AT THIS
TIME. TEMPERATURES THROUGH FRIDAY SHOULD CONTINUE TO BE MILD WITH
HIGHS MAINLY IN THE MID 40S TO LOW 50S. LOWS TONIGHT SHOULD DROP TO
AROUND FREEZING MAINLY NORTH OF I-70 IN MISSOURI AND I-64 IN
ILLINOIS; HOWEVER IT'S LIKELY TEMPERATURES WILL BEGIN RISING
SLIGHTLY BEFORE SUNRISE. THIS SHOULD RULE OUT ANY CHANCE FOR
FREEZING RAIN. CLOUDS AND SOUTHWEST FLOW KEEP TEMPERATURES IN THE
40S THURSDAY NIGHT/FRIDAY MORNING.
CARNEY
LONG TERM
(FRIDAY THROUGH NEXT WEDNESDAY)
ISSUED AT 216 PM CST WED JAN 29 2025
THE FORECAST FOR THE WEEKEND REMAINS DRY AND MILD IN ZONAL FLOW AT
500MB. LOW LEVEL SOUTH-SOUTHWEST FLOW WILL PRODUCE SOLID WARM
ADVECTION AND FORECAST SOUNDINGS INDICATE LIMITED CLOUD COVER SO
THERE SHOULD BE DECENT INSOLATION. THERE IS SOME DISAGREEMENT IN
HIGH TEMPERATURES ON SATURDAY BETWEEN VARIOUS DETERMINISTIC VS
ENSEMBLE GUIDANCE SOURCES. FOR INSTANCE, THE LREF MEAN IS 6-8
DEGREES COOLER AT ANY GIVEN POINT THAN WHAT MOST DETERMINISTIC
GUIDANCE SOURCES ARE SHOWING. I BELIEVE THESE DIFFERENCES ARE BEING
CAUSED BY POSITIONAL DIFFERENCES IN A 10-12 DEGREE TEMPERATURE
GRADIENT FROM SOUTHWEST TO NORTHEAST ACROSS THE AREA. THIS GRADIENT
IS DUE TO A COOL HIGH PRESSURE SYSTEM MOVING ACROSS THE GREAT LAKES.
NORTH/NORTHEASTERN PORTIONS OF THE AREA WILL BE ON THE PERIPHERY OF
THIS HIGH WITH EASTERLY OR NORTHEASTERLY FLOW FOR PART OF SATURDAY
WHICH WILL YIELD HIGHS IN THE MID 40S, WHILE CENTRAL MISSOURI SHOULD
BE SOLIDLY IN WARM SOUTHERLY FLOW WITH HIGHS IN THE MID 50S. THIS
RANGE OF TEMPERATURES LOOKS REASONABLE GIVEN THE SYNOPTIC SET UP,
THOUGH MY CONFIDENCE IN THE HIGH TEMPERATURE AT ANY GIVEN POINT IS
MODERATE AT BEST AND WILL BE DEPENDENT ON HOW FAR SOUTH THE
PERIPHERY OF THE HIGH TRACKS. TEMPERATURES ON SUNDAY SHOULD BE THE
WARMEST OF THE NEXT 7 DAYS WITH THE ENTIRE AREA IN SOUTH-SOUTHWEST
FLOW. THE NBM IS FORECASTING HIGHS IN THE UPPER 50S TO MID 60S
WHICH IS WITHIN THE LREF INTERQUARTILE.
THE UPPER LEVEL PATTERN BECOMES SOMEWHAT MORE AMPLIFIED MONDAY INTO
TUESDAY, PRIMARILY ACROSS THE NORTHERN U.S./SOUTHERN CANADA. THE
INITIAL SHORT WAVE MOVES ALONG THE U.S./CANADA BORDER MONDAY, AND THE
SURFACE REFLECTION PUSHES A STRONG COLD FRONT SOUTH INTO THE MID
MISSISSIPPI VALLEY. WHILE THE WAVE DOES AMPLIFY THE PATTERN
SLIGHTLY, THE TROUGH OVER EASTERN NORTH AMERICA DOESN'T GET NEARLY
AS DEEP AS IT HAS RECENTLY. THEREFORE THE ARCTIC HIGH BEHIND THE
COLD FRONT ONLY GRAZES US HERE IN THE MID MISSISSIPPI VALLEY,
ALTHOUGH TEMPERATURES WILL COOL OFF SIGNIFICANTLY. THERE IS SOME
QUESTION ABOUT HOW FAR SOUTH THE COLD FRONT WILL MOVE BEFORE
STALLING, WITH THE GFS PUSHING IT ALL THE WAY TO THE GULF, BUT THE
ECMWF STALLS THE FRONT VERY NEAR THE I-70 CORRIDOR. HOW FAR SOUTH
THE FRONT MOVES WILL OBVIOUSLY HAVE A HUGE IMPACT ON TEMPERATURES
NEXT WEEK. THE LREF MAX TEMPERATURE INTERQUARTILE RANGE FOR MONDAY
AND TUESDAY IS 13 DEGREES, AND WEDNESDAY RANGE IS 22 DEGREES.
NEEDLESS TO SAY THE TEMPERATURE FORECAST FOR NEXT WEEK IS VERY LOW
CONFIDENCE AT THIS TIME. ADDITIONALLY, THERE IS A CHANCE FOR SOME
PRECIP WEDNESDAY, IF TEMPERATURES END UP TOWARD THE LOWER END OF
WHAT THE ENSEMBLE IS PREDICTING (IN THE 30S) THE PRECIPITATION
COULD BE FROZEN OR FREEZING.
CARNEY
AVIATION
(FOR THE 18Z TAFS THROUGH 18Z THURSDAY AFTERNOON)
ISSUED AT 1142 AM CST WED JAN 29 2025
VFR FLIGHT CONDITIONS AND LIGHT WINDS WILL PREVAIL ACROSS THE AREA
INTO THE OVERNIGHT HOURS TONIGHT. EXPECT RAIN TO OVERSPREAD THE
AREA FROM SOUTHWEST TO NORTHEAST AFTER 10-12Z. LOW MVFR/IFR
CEILINGS AND VISIBILITIES WILL ACCOMPANY THE RAIN, AND PREVAIL FOR
THE REMAINDER OF THE PERIOD.
CARNEY
LSX WATCHES/WARNINGS/ADVISORIES
MO...NONE.
IL...NONE.
WFO LSX
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