910
FXUS63 KLSX 162305
AFDLSX
AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE SAINT LOUIS MO
505 PM CST MON DEC 16 2024
KEY MESSAGES
- THE NEXT CHANCE (UP TO 60-70%) FOR PRECIPITATION COMES TUESDAY NIGHT
INTO WEDNESDAY. PRECIPITATION IS EXPECTED TO BE RAIN.
- TEMPERATURES WILL GENERALLY TREND INCREASINGLY COLDER THROUGH
THIS WEEK INTO THE WEEKEND.
SHORT TERM
(THROUGH LATE TUESDAY NIGHT)
ISSUED AT 234 PM CST MON DEC 16 2024
WATER VAPOR IMAGERY SHOWS AN UPPER-LEVEL TROUGH SWINGING THROUGH THE
MIDDLE MISSISSIPPI VALLEY ASSOCIATED WITH A COLD FRONT THAT IS
EXITING THE CWA TO THE SOUTHEAST. THIS COLD FRONT PAIRED WITH DEEP
NORTHWESTERLY FLOW IS SCOURING MOISTURE FROM THE AREA, WITH MOST
LOCATIONS NOW SEEING CLEAR SKIES AFTER A DREARY START TO THE DAY.
THIS SIGNALS THE APPROACH OF THE POST-FRONTAL AIRMASS THAT WILL
BRING MOST LOCATIONS TONIGHT TO AROUND FREEZING. GIVEN THE POST-
FRONTAL HIGH PRESSURE MOVING DIRECTLY OVERHEAD TONIGHT, WINDS LIGHT
TO CALM, AND SKIES CLEAR, RADIATIVE COOLING WILL TAKE PLACE, AND
TEMPERATURES HAVE BEEN LOWERED SLIGHTLY FROM THE PREVIOUS FORECAST
AS SUCH.
THE OVERALL PATTERN WILL QUICKLY EVOLVE ON TUESDAY, AS FLOW ALOFT
BECOMES QUASI-ZONAL TO SOUTHWESTERLY AHEAD OF TROUGH AMPLIFYING OVER
THE PLAINS. THIS WILL PUSH THE SURFACE HIGH QUICKLY EASTWARD WITH
SOUTHERLY TO SOUTHEASTERLY FLOW RETURNING TO THE AREA TUESDAY
AFTERNOON. THE SURFACE REFLECTION ASSOCIATED WITH THE TROUGH WILL
MOVE THROUGH THE MIDDLE MISSISSIPPI VALLEY TUESDAY EVENING AND PUSH
A COLD FRONT THROUGH THE CWA. WARM AIR ADVECTION AHEAD OF THE LOW
WILL BRING MOISTURE INTO THE REGION THAT WILL YIELD SCATTERED LIGHT
RAIN OVER MUCH OF THE CWA. IT'S NOT UNTIL THE FRONT REACHES
SOUTHEASTERN MISSOURI AND SOUTHWESTERN ILLINOIS THAT FORCING ALOFT
DUE TO THE JET AND SHORTWAVE INCREASES, WITH WIDESPREAD RAIN THEN
EXPECTED ALONG THE FRONT. THIS LEADS TO THE BEST CHANCES (UP TO 60-
70%) OF RAIN BEING OVER FAR SOUTHEASTERN MISSOURI AND SOUTHWESTERN
ILLINOIS TUESDAY NIGHT/EARLY WEDNESDAY MORNING. A MINORITY OF
GUIDANCE SHOWS SATURATION THROUGH A PORTION OF THE DENDRITIC GROWTH
ZONE (DGZ) ACROSS NORTHEASTERN MISSOURI THAT MAY ALLOW FOR SNOW TO
REACH THE SURFACE AS COLDER AIR MOVES INTO THE CWA AND PRECIPITATION
WINDS DOWN. HOWEVER, WHAT MODEL SOUNDINGS THAT DO SHOW SNOW HAVE
WEAK LIFT IN THE DGZ, SUPPORTING LOW SNOW RATES, AND THE GROUND
STAYS ABOVE FREEZING. THEREFORE, SNOW HAS BEEN LEFT OUT OF THE
FORECAST FOR NOW, AND IF IT DOES OCCUR, IMPACTS WILL BE MINOR AT
WORST.
ELMORE
LONG TERM
(WEDNESDAY THROUGH NEXT MONDAY)
ISSUED AT 234 PM CST MON DEC 16 2024
AT THE START OF THE EXTENDED FORECAST PERIOD, GUIDANCE CONSENSUS IS
THAT THE AXIS OF AN UPPER-LEVEL TROUGH WILL BE SWINGING THROUGH THE
MIDDLE MISSISSIPPI VALLEY. AT THE SURFACE, POST-FRONTAL AIR WILL BE
SPILLING INTO THE CWA, PUSHING TUESDAY NIGHT'S COLD FRONT FURTHER
SOUTH. ENSEMBLE GUIDANCE IS TIGHTLY CLUSTERING AROUND CLIMATOLOGICAL
NORMALS FOR TEMPERATURES ON WEDNESDAY (UPPER 30S TO UPPER 40S). AS
FOR THURSDAY, CONFIDENCE DECREASES IN TEMPERATURES, AS GUIDANCE
DEPICTS A CLIPPER DIVING THROUGH THE UPPER-MIDWEST, BUT DIFFERS ON
ITS PHASING. THEREFORE, THIS PRODUCES VARIABILITY IN HOW QUICKLY
THE POST-FRONTAL HIGH PRESSURE FROM WEDNESDAY DEPARTS THE AREA AND
SOUTHERLY FLOW RETURNS AHEAD OF A FROPA. AS A RESULT, SPREAD WITHIN
THE INTERQUARTILE RANGE OF ENSEMBLE GUIDANCE RANGES FROM MID 30S ON
THE COOLER END TO MID 40S ON THE WARMER END. THE CURRENT FORECAST
LEANS TOWARD WARMER GUIDANCE, AS THAT'S WHERE A MAJORITY OF GUIDANCE
FALLS. ENSEMBLE PROBABILITIES TOP OUT AT 25% FOR MEASURABLE
PRECIPITATION (0.01") IN OUR FAR WEST-CENTRAL ILLINOIS COUNTIES WITH
THIS CLIPPER, LEADING TO HIGH CONFIDENCE IN A CONTINUING THE
MOSTLY DRY FORECAST.
NORTHWESTERLY FLOW REMAINS ALOFT THROUGH THE END OF THE WEEK INTO
THE WEEKEND PER DETERMINISTIC MODEL AND ENSEMBLE CLUSTERS, KEEPING
TEMPERATURES AT OR JUST BELOW SEASONAL NORMALS AND CONDITIONS DRY.
UPPER-LEVEL RIDGING BEGINS TO BUILD INTO THE REGION EARLY NEXT WEEK -
POSSIBLY AS EARLY AS SUNDAY, WITH TEMPERATURES GRADUALLY WARMING
PER ENSEMBLE MEANS.
ELMORE
AVIATION
(FOR THE 00Z TAFS THROUGH 00Z TUESDAY EVENING)
ISSUED AT 502 PM CST MON DEC 16 2024
DRY, VFR CONDITIONS WILL PERSIST THROUGH THE TAF PERIOD. GUSTY
WEST WINDS WILL WEAKEN THIS EVENING, TURNING OUT OF THE SOUTH
TOMORROW WITH THE NORTHWARD ADVANCE OF A WARM FRONT. A WEAK SYSTEM
WILL PASS THROUGH THE REGION LATE IN THE FORECAST PERIOD, WHICH
WOULD DRAW CIGS DOWN AGAIN AT ALL TAF SITES EXCEPT FOR KUIN AND
THREATEN LIGHT RAIN IN THE ST. LOUIS METROPOLITAN AREA. THESE
IMPACTS ARE FORECAST OUTSIDE OF THE CURRENT PERIOD, BUT EXACTLY
HOW LOW CIGS GET IS STILL UNCERTAIN.
MRB
LSX WATCHES/WARNINGS/ADVISORIES
MO...NONE.
IL...NONE.
WFO LSX
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page