380
FXUS63 KLSX 100723
AFDLSX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAINT LOUIS MO
223 AM CDT SUN MAY 10 2026
KEY MESSAGES
- TEMPERATURES ARE EXPECTED TO FLUCTUATE MOST OF THIS WORK WEEK
BEFORE A MORE PROLONGED PERIOD OF WELL-ABOVE NORMAL TEMPERATURES
POTENTIALLY BEGINS FRIDAY.
SHORT TERM
(THROUGH LATE TONIGHT)
ISSUED AT 223 AM CDT SUN MAY 10 2026
COOLER AIR CONTINUES TO FILTER INTO THE AREA FROM THE NORTHWEST
BEHIND LAST NIGHT'S COLD FRONT. MODERATE LOW-LEVEL COLD AIR
ADVECTION WILL CONTINUE ALL DAY TODAY AS 850-HPA TEMPERATURES DROP
CLOSER TO +5C. SCATTERED TO BROKEN MIDLEVEL CLOUDS WILL ALSO BE
AROUND MUCH OF THE DAY, WHICH ALSO SHOULD HELP KEEP TEMPERATURES
ON THE COOL SIDE. HIGHS ARE EXPECTED TO BE IN THE UPPER 60S TO
NEAR 70 DEGREES, OR ROUGHLY 5 DEGREES BELOW NORMAL FOR THE DATE.
SEASONABLY COOL CONDITIONS WILL CONTINUE TONIGHT IN THE VICINITY OF
A 1022+ HPA SURFACE RIDGE (>90TH PERCENTILE OF CLIMATOLOGY). LIGHT
WINDS ASSOCIATED WITH THE RIDGE, A MOSTLY CLEAR SKY, AND DEWPOINTS
NEAR THE 10TH PERCENTILE FOR THE DATE ARE EXPECTED TO COMBINE TO
YIELD VERY FAVORABLE CONDITIONS FOR RADIATIONAL COOLING OVERNIGHT.
LOWS ARE FORECAST TO DROP INTO THE LOW TO MID 40S ACROSS THE BI-
STATE AREA, OR 6-10 DEGREES BELOW NORMAL. A FEW LOCATIONS MAY EVEN
DROP INTO THE UPPER 30S SUCH AS FAVORED VALLEYS IN EASTERN MISSOURI.
GOSSELIN
LONG TERM
(MONDAY THROUGH SATURDAY)
ISSUED AT 223 AM CDT SUN MAY 10 2026
(MONDAY - TUESDAY NIGHT)
TEMPERATURES ON MONDAY SHOULD BE SLIGHTLY WARMER THAN THIS
AFTERNOON, MAINLY DUE TO PLENTY OF SUNSHINE. HIGHS ARE EXPECTED TO
BE BACK CLOSE TO NORMAL IN THE LOW TO MID 70S. A MORE PRONOUNCED
WARMING TREND WILL BEGIN MONDAY NIGHT INTO TUESDAY AS LOW-LEVEL
WINDS TURN OUT OF THE SOUTH/SOUTHWEST AROUND THE WESTERN PERIPHERY
OF THE DEPARTING SURFACE HIGH. STRONG LOW-LEVEL WARM AIR ADVECTION
PORTENDS TO A RETURN TO THE UPPER 70S TO LOW 80S FOR TUESDAY
AFTERNOON.
A COLD FRONT IS EXPECTED TO MOVE THROUGH THE REGION TUESDAY NIGHT.
THIS FRONT BRINGS A CHANCE (20-40%) OF SHOWERS AND THUNDERSTORMS TO
THE AREA, BUT NO WIDESPREAD OR SIGNIFICANT RAINFALL IS EXPECTED WITH
THIS SYSTEM. THE MID-MISSISSIPPI VALLEY IS LIKELY TO BE IN AN AREA
OF WEAKER SURFACE CONVERGENCE ALONG THE FRONT, WITH STRONGER
MID/UPPER LEVEL FORCING FOR ASCENT ALSO DISPLACED WELL TO THE
NORTHEAST ACROSS THE GREAT LAKES. PROBABILITIES FROM THE LREF FOR AT
LEAST A QUARTER INCH OF RAIN OVER A 24-HOUR PERIOD STAY AT OR BELOW
15% AREAWIDE.
(WEDNESDAY - THURSDAY NIGHT)
MODEL SPREAD HAS CONTINUED TO DECREASE WITH RESPECT TO TEMPERATURES
BEHIND TUESDAY NIGHT'S COLD FRONT. THE INTER-QUARTILE RANGE FOR 850-
HPA TEMPERATURES WEDNESDAY EVENING IS DOWN TO ABOUT 3C. YESTERDAY
THAT WAS CLOSER TO 5-6C. IT SEEMS MORE PROBABLE THAT OUR REGION IS
ON THE FAR WEST/SOUTHWEST PERIPHERY OF THE COOLER AIR MASS, WHICH
MEANS THE MOST LIKELY SCENARIO IS FOR TEMPERATURES TO BE NEAR
NORMAL, THOUGH THERE SHOULD BE A GRADIENT FROM EAST (COOLER) TO WEST
(WARMER) BOTH FOR WEDNESDAY AND THURSDAY'S HIGHS.
(FRIDAY - SATURDAY)
THERE IS A SIGNAL IN ENSEMBLE GUIDANCE FOR MORE CONSISTENTLY ABOVE
NORMAL TEMPERATURES BEGINNING NEXT FRIDAY INTO NEXT WEEKEND AS
MID/UPPER LEVEL RIDGING PUSHES EASTWARD OUT OF THE ROCKIES.
TEMPERATURES AT 850 HPA ARE ALSO EXPECTED TO CLIMB CLOSER TO +15C,
OR NEAR TO SLIGHTLY ABOVE THE 90TH PERCENTILE OF CLIMATOLOGY.
HOWEVER, EXACTLY HOW WARM IS STILL A QUESTION MARK EACH DAY. FOR
FRIDAY, THERE IS A SUBTLE MIDLEVEL SHORTWAVE MOVING SOMEWHERE ACROSS
THE MIDWEST. THIS FEATURE COULD CAUSE SOME SHOWERS AND
THUNDERSTORMS, OR AT THE VERY LEAST, CLOUD COVER. THE SPREAD IN THE
UPPER AIR PATTERN ACROSS THE EASTERN TWO-THIRDS OF THE CONUS THEN
INCREASES BY SATURDAY. WHILE TWO OF THE FOUR CLUSTERS OF THE 500-HPA
PATTERN (65% OF TOTAL LREF MEMBERSHIP) MAINTAIN MID/UPPER LEVEL
RIDGING ACROSS THE MID-MISSISSIPPI VALLEY, THE OTHER TWO CLUSTERS
(35% OF LREF MEMBERS) SHOW ANOTHER STRONG TROUGH MOVING ACROSS THE
GREAT LAKES. IN THE LATTER SCENARIO, A COLD FRONT WOULD MOVE THROUGH
OUR NECK OF THE WOODS AND LEAD TO COOLER TEMPERATURES FOR LATE
WEEKEND (ALONG WITH A HIGHER CHANCE OF SHOWERS/THUNDERSTORMS
ASSOCIATED WITH THE FRONTAL PASSAGE). IF MID/UPPER LEVEL RIDGING
MAINTAINS ITSELF, WARMER (AND LIKELY DRY) WEATHER WOULD PROBABLY
CONTINUE. AT THIS TIME, THERE IS HIGH CONFIDENCE IN HIGHS WELL ABOVE
80 DEGREES, BUT THE CHANCES OF REACHING 90+ APPEAR UNLIKELY AT THIS
TIME. PROBABILITIES FOR 90+ DEGREE HIGHS BOTH FRIDAY AND SATURDAY
ARE AT OR BELOW 15% BOTH DAYS ON THE LREF. AS ALLUDED TO BY THE
PREVIOUS FORECASTER, NBM PERCENTILES/PROBABILISTIC INFORMATION
APPEAR TOO WARM/AGGRESSIVE, LIKELY DUE TO LONG TERM (90 DAY) BIAS
CORRECTION.
GOSSELIN
AVIATION
(FOR THE 06Z TAFS THROUGH 06Z SUNDAY NIGHT)
ISSUED AT 958 PM CDT SAT MAY 9 2026
A SMALL POCKET OF SHOWERS ALONG WITH SCATTERED EMBEDDED
THUNDERSTORMS CONTINUES TO SLIDE EAST-SOUTHEASTWARD, PUSHING ACROSS
EAST-CENTRAL MO INTO WESTERN IL. WITHIN THE NEXT 1-2 HOURS, THIS
ACTIVITY WILL IMPACT THE ST. LOUIS METRO TERMINALS WITH IMPACTS
LIKELY (50%) AT KSTL WITHIN THE HOUR AND POSSIBLE (30%) AT KSUS AND
KCPS. OBSERVATIONS HAVE REVEALED THIS COMPLEX OF SHOWERS AND
THUNDERSTORMS HAS CONSISTENTLY BEEN PRODUCING WIND GUSTS IN THE 30-
35KT RANGE ALONG WITH BRIEF MVFR VISIBILITIES WITHIN THE HEAVIEST
POCKETS OF RAIN. THIS ACTIVITY WILL MOVE OUT OF THE AREA BY 06Z WITH
LINGERING SHOWERS POSSIBLE ALONG THE I-70 CORRIDOR UNTIL 08Z. LIGHT
NORTHERLY SURFACE WINDS WILL PREVAIL TONIGHT LASTING THROUGH SUNDAY
WITH LIGHT AND VARIABLE WINDS RETURNING AFTER SUNSET TOMORROW
EVENING.
PEINE
LSX WATCHES/WARNINGS/ADVISORIES
MO...NONE.
IL...NONE.
WFO LSX
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