962
FXUS63 KLSX 151151
AFDLSX
AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE SAINT LOUIS MO
551 AM CST SUN DEC 15 2024
KEY MESSAGES
- ANOTHER ROUND OF RAIN WITH A FEW THUNDERSTORMS IS EXPECTED
TONIGHT INTO MONDAY MORNING, MAINLY ALONG AND EAST OF I-44 AND
EAST OF I-55. A FEW THUNDERSTORMS ARE ALSO POSSIBLE ACROSS PARTS
OF SOUTHEAST MISSOURI AND SOUTHERN ILLINOIS.
- ANOTHER ROUND OF RAIN IS LIKELY TUESDAY NIGHT INTO EARLY
WEDNESDAY MORNING.
SHORT TERM
(THROUGH LATE MONDAY AFTERNOON)
ISSUED AT 424 AM CST SUN DEC 15 2024
VISIBILITIES HAVE IMPROVED ACROSS NORTHEAST MISSOURI AND WEST
CENTRAL ILLINOIS AS THE WIND HAS SHIFTED TO THE WEST AND
SOUTHWEST. WIDESPREAD VISIBILITIES AT OR BELOW 1/4 MILE LOOK
UNLIKELY FOR THE REST OF THE MORNING, THEREFORE THE DENSE FOG
ADVISORY WAS CANCELLED. LATEST SATELLITE IMAGERY SHOWS A MID-
UPPER LEVEL SHORT WAVE TROUGH MOVING NORTHEAST THROUGH ILLINOIS
INTO THE GREAT LAKES REGION. SHORT WAVE RIDGING WILL BUILD ACROSS
THE MID MISSISSIPPI VALLEY BEHIND IT TODAY. BROAD SCALE DESCENT
UNDER THE RIDGE SHOULD PRECLUDE ANY KIND OF WIDE- SPREAD PRECIP.
WITH THAT SAID, TODAY'S FORECAST SOUNDINGS SHOW A STRONG
SUBSIDENCE INVERSION UNDER THE RIDGE ALOFT WITH A MOIST LAYER
TRAPPED NEAR THE SURFACE. SOUNDINGS ALSO SHOW THERE MAY BE JUST
ENOUGH LIFT IN THE 0-1KM RANGE TO SQUEEZE OUT A LITTLE PATCHY
DRIZZLE THIS MORNING. THE INVERSION WILL LOCK THIS LOW LEVEL
MOISTURE IN OVER THE AREA THIS MORNING, WHICH WILL ALLOW THE LOW
STRATUS TO PERSIST. HOWEVER, GUIDANCE SUGGESTS THAT THE STRATUS
WILL BREAK UP OVER MOST OF THE AREA AS TEMPERATURES WARM THIS
AFTERNOON THROUGH INSOLATION AND LIGHT SOUTHERLY FLOW. THE
EXCEPTION WILL PROBABLY BE FAR NORTHEAST MISSOURI AND WEST CENTRAL
ILLINOIS WHERE TEMPERATURES WILL REMAIN COOLER THROUGH THE DAY.
THE NEXT UPSTREAM SHORT WAVE MOVES INTO THE GREAT PLAINS TONIGHT,
WITH THE SURFACE LOW DEVELOPING NEAR THE NORTH DAKOTA/MINNESOTA
BORDER WITH CANADA. THE TROUGH, WHILE NOT ESPECIALLY SHARP, DOES
EXTEND ALL THE WAY SOUTH THROUGH THE PLAINS INTO NORTHERN TEXAS. LOW
LEVEL SOUTHWEST FLOW AHEAD OF THE TROUGH WILL BRING ANOTHER SLUG OF
MOISTURE OUT OF THE SOUTHEAST PLAINS INTO THE MID-MISSISSIPPI
VALLEY. LOW LEVEL MOISTURE CONVERGENCE AND INCREASING SYNOPTIC-
SCALE LIFT AHEAD OF THE TROUGH WILL PRODUCE ANOTHER ROUND OF RAIN
BEGINNING LATE IN THE EVENING INTO THE OVERNIGHT HOURS TONIGHT. THE
GFS AND RAP BOTH SHOW AS MUCH AS 300-500 J/KG OF MUCAPE OVERNIGHT
ACROSS PARTS OF SOUTHERN MISSOURI AND ILLINOIS AHEAD OF THE TROUGH,
SO A FEW THUNDERSTORMS ARE CERTAINLY POSSIBLE. DEEP-LAYER SHEAR IS
IMPRESSIVE AT 50+KTS, HOWEVER THE INSTABILITY IS ALL ELEVATED, AND
MOST OF THE ELEVATED CAPE IS BELOW THE HAIL GROWTH ZONE. THEREFORE
SEVERE STORMS ARE NOT EXPECTED DESPITE THE STRONG SHEAR. THE COLD
FRONT ASSOCIATED WITH THE TROUGH WILL SWEEP THROUGH THE AREA ON
MONDAY, WITH ALL OF THE PRECIPITATION REMAINING AHEAD OF IT, MAINLY
ALONG AND EAST OF I-44 IN MISSOURI, AND I-55 IN ILLINOIS. WEAK
INSTABILITY REMAINS PRESENT AHEAD OF THE FRONT INTO MONDAY MORNING,
SO A FEW RUMBLES OF THUNDER WILL CONTINUE TO BE POSSIBLE. THE
CHANCE FOR RAIN ENDS WITH FROPA LATE MONDAY MORNING INTO THE EARLY
AFTERNOON AS THE UPPER TROUGH MOVES EAST OF THE REGION AND DRIER AIR
FILTERS IN BEHIND THE FRONT.
CARNEY
LONG TERM
(MONDAY NIGHT THROUGH SATURDAY)
ISSUED AT 424 AM CST SUN DEC 15 2024
THE ACTIVE PATTERN CONTINUES THIS WEEK. DRY WEATHER WITH SOMEWHAT
COOLER TEMPERATURES WILL PREVAIL MONDAY NIGHT INTO TUESDAY. ANOTHER
SHORT WAVE WILL DIG INTO THE PLAINS AND UPPER MIDWEST TUESDAY NIGHT
WHICH WILL BRING ANOTHER ROUND OF PRECIPITATION INTO THE MID-
MISSISSIPPI VALLEY. ALTHOUGH THE LREF CLUSTER ANALYSIS IS SHOWING
SOME TIMING DIFFERENCES IN THE EOF PATTERNS, THE DETERMINISTIC GFS
AND ECMWF ARE IN GOOD AGREEMENT WITH THIS TROUGH AND ASSOCIATED
PRECIP. THE NBM LOADED IN LIKELY POPS FOR MOST OF THE FORECAST
AREA, AND GIVEN THAT 60-70 PERCENT OF THE ENSEMBLE MEMBERS ARE
SHOWING PRECIP TUESDAY NIGHT I THINK THOSE POPS ARE GOOD. ANOTHER
SHOT OF COOLER AND DRIER AIR WILL FOLLOW THE TROUGH FOR WEDNESDAY
AND PERSIST INTO THURSDAY. GUIDANCE IS ADVERTISING THAT A MUCH
DEEPER LONG WAVE TROUGH WILL DIG INTO THE OHIO VALLEY ON FRIDAY
WHICH WOULD DRIVE A COLD CANADIAN AIR MASS SOUTH THROUGH THE
MIDWEST. HOWEVER, CLUSTER ANALYSIS IS SHOWING A LOT OF UNCERTAINTY
ASSOCIATED WITH THIS TROUGH, SO CONFIDENCE IN THE FORECAST OUT
TOWARD THE END OF THE WEEK INTO THE WEEKEND IS LOW AT THIS TIME.
CARNEY
AVIATION
(FOR THE 12Z TAFS THROUGH 12Z MONDAY MORNING)
ISSUED AT 521 AM CST SUN DEC 15 2024
WIDESPREAD LOW CLOUDS WILL BRING IFR AND LOW MVFR CEILINGS THROUGH
THE MORNING HOURS WITH NO IMPROVEMENT TO VFR UNTIL 20-21Z. THERE
WILL ALSO BE SOME LOWERED VISIBILITIES IN FOG UNTIL 15Z AT COU AND
JEF. CEILINGS WILL DROP AGAIN TO MVFR/IFR AGAIN LATE THIS EVENING AND
OVERNIGHT WITH RAIN MOVING INTO THE ST. LOUIS METRO AREA TERMINALS
AFTER 06Z AND WITH LESSER CHANCES AT COU/JEF WARRANTING A PROB30
GROUP.
BRITT
LSX WATCHES/WARNINGS/ADVISORIES
MO...NONE.
IL...NONE.
WFO LSX
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