788
FXUS63 KLSX 130345
AFDLSX
AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE SAINT LOUIS MO
1045 PM CDT TUE MAY 12 2026
KEY MESSAGES
- SCATTERED SHOWERS AND AN ISOLATED THUNDERSTORM ARE POSSIBLE AS A
COLD FRONT MOVES THROUGH THIS EVENING.
- AFTER A BRIEF COOL DOWN BEHIND THE FRONT, EVEN WARMER WEATHER
ARRIVES BY THIS WEEKEND.
SHORT TERM
(THROUGH LATE TONIGHT)
ISSUED AT 123 PM CDT TUE MAY 12 2026
WATER VAPOR IMAGERY REVEALS A SHORTWAVE DIVING OUT OF SOUTH-CENTRAL
CANADA INTO THE UPPER GREAT LAKES. IN RESPONSE, A SURFACE LOW HAS
MOVED INTO NORTHERN WISCONSIN, WITH A COLD FRONT TRAILING TO THE
SOUTHWEST THROUGH IOWA AND INTO KANSAS. THESE FEATURES WILL
CONTINUE TO DRIFT TO THE EAST/SOUTHEAST, PUSHING THE COLD FRONT
INTO THE MID-MISSISSIPPI VALLEY THIS EVENING. GUSTY WINDS AHEAD OF
THE FRONT, COUPLED WITH THE RECENTLY TILLED SOILS, DO RAISE SOME
CONCERNS ABOUT BLOWING DUST. FORTUNATELY TODAY'S WINDS/ANTECEDENT
CONDITIONS ARE NOTICEABLY LOWER/LESS CONDUCIVE THAN IN PREVIOUS
BLOWING DUST EVENTS, SO THE POTENTIAL FOR IMPACTFUL BLOWING DUST
APPEARS TO BE QUITE LOW (<15%).
AS THE FRONT MOVES THROUGH THE AREA THIS EVENING AND TONIGHT, THERE
IS A LOW CHANCE (<30%) THAT IT PROVIDES ENOUGH LIFT TO SQUEEZE OUT A
FEW SHOWERS OVER OUR AREA. HOWEVER, THE COMBINATION OF POOR MOISTURE
RETURN AND LOW LEVEL WARM AIR ADVECTION AHEAD OF THE FRONT WILL
SIGNIFICANTLY LIMIT AND CAP INSTABILITY. THEREFORE THUNDERSTORM
CHANCES ARE VERY LOW (<15%).
BSH
LONG TERM
(WEDNESDAY THROUGH NEXT TUESDAY)
ISSUED AT 123 PM CDT TUE MAY 12 2026
DEEP NORTH-NORTHWESTERLY FLOW BEHIND THE FRONT AND PARENT SHORTWAVE
WILL PERSIST THROUGH THE DAY ON WEDNESDAY BEFORE UPPER LEVEL RIDGING
AND SOUTHERLY LOW LEVEL FLOW TAKE HOLD ON THURSDAY. THIS WILL PUSH
TOMORROW'S TEMPERATURES 5-10 DEGREES COOLER THAN TODAY, WARMING JUST
A BIT ON THURSDAY AS SOUTHERLY WINDS INCREASE.
THE UPPER LEVEL PATTERN WILL BECOME MORE ZONAL BY THE END OF THE
WORKWEEK, GRADUALLY BECOMING SOUTHWESTERLY TOWARD THE END OF THE
WEEKEND AS A DEEP TROUGH MOVES OVER THE WESTERN CONUS. THIS WILL
RESULT IN PERSISTENT SOUTHWESTERLY LOW LEVEL FLOW OVER THE MID
MISSISSIPPI VALLEY THROUGH THE WEEKEND, WHICH WILL IN TURN ADVECT
WARMER TEMPERATURES AND DEEPER MOISTURE INTO THE REGION. THE
RETURN OF DEEPER MOISTURE WILL KEEP AT LEAST MODEST INSTABILITY
OVER THE REGION THROUGH THE PERIOD.
I EXPECT TO SEE AT LEAST A FEW IMPULSES RIPPLE THROUGH THE
ZONAL/SOUTHWESTERLY UPPER LEVEL FLOW FROM THE END OF THE WORKWEEK
THROUGH THE WEEKEND, WHICH COUPLED WITH THE LINGERING INSTABILITY,
SHOULD RESULT IN SOME SHOWERS AND THUNDERSTORMS. UNFORTUNATELY, IT
IS DIFFICULT TO CONFIDENTLY PIN DOWN THE DETAILS OF THESE
IMPULSES AND RESULTANT STORM CHANCES, SO OUR FORECAST CURRENTLY
FEATURES PERSISTENT, LOW PRECIP CHANCES ALL WEEKEND. I EXPECT
THERE WILL ACTUALLY BE PLENTY OF DRY TIME THIS WEEKEND, AND WE
SHOULD BE ABLE TO FOCUS THIS FORECAST AS WE GET CLOSER TO THE
WEEKEND.
AS FAR AS TEMPERATURES ARE CONCERNED, THE NBM REMAINS STUCK ON THE
VERY HIGH END OF FORECAST GUIDANCE AND APPEARS UNLIKELY TO BE
CORRECT. EVEN IF WE ASSUME THE 90TH PERCENTILE OF 850MB TEMPERATURES
FROM THE GEFS/ENS/GEPS AND FULL MIXING TO THE SURFACE, I STILL ONLY
EXPECT HIGHS IN THE LOW 90S. THERE IS NO STRONG EVIDENCE TO
SUPPORT THAT WE'LL BE NEAR THE 90TH PERCENTILE, AND FULL MIXING
APPEARS UNLIKELY GIVEN THE ABOVE RAIN/CLOUD CHANCES THROUGH THE
WEEKEND.
THE UPPER TROUGH WILL PUSH TOWARD THE CENTRAL CONUS EARLY NEXT WEEK
AND WILL LEAD TO MORE FOCUSED SHOWER AND THUNDERSTORM POTENTIAL. THE
TROUGH WILL ALSO LEAD TO GREATER DEEP LAYER SHEAR THAN WHAT WE'RE
EXPECTING THIS WEEKEND, SO THIS WILL REPRESENT THE BEST CHANCE FOR
SEVERE STORMS OVER THE NEXT WEEK. HOWEVER THE DETAILS REMAIN MURKY
AT THIS FORECAST RANGE, LEADING TO LOW FORECAST CONFIDENCE AT THIS
TIME.
BSH
AVIATION
(FOR THE 06Z TAFS THROUGH 06Z WEDNESDAY NIGHT)
ISSUED AT 1041 PM CDT TUE MAY 12 2026
A NARROW SWATH THAT CONTAINS A FEW SCATTERED POCKETS OF RAIN
SHOWERS CONTINUES TO SLIDE SOUTHEASTWARD ALONG AND AHEAD OF AN
APPROACHING COLD FRONT. CURRENTLY, THIS ACTIVITY STRETCHES FROM
CENTRAL IL SOUTHWESTWARD INTO EAST-CENTRAL MO WITH THE GREATEST
COVERAGE OF SHOWERS OFF TO THE EAST ACROSS IL. A LOW CHANCE
(10-20%) FOR A BRIEF SHOWER REMAINS AT THE ST. LOUIS METRO
TERMINALS UNTIL AROUND 06Z. THE COLD FRONT HAS PASSED KUIN WITHIN
THE LAST HOUR AND WILL BE NEARING KCOU/KJEF AND THE ST. LOUIS
METRO TERMINALS WITHIN THE NEXT FEW HOURS. LIGHT SOUTHWESTERLY
WINDS AHEAD OF THE FRONT REMAIN LIGHT WHILE VEERING
NORTHWESTERLY BEHIND THE FRONT FOR THE REMAINDER OF THE NIGHT.
NORTHWESTERLY WINDS STRENGTHEN BY LATE WEDNESDAY MORNING, GUSTING
TO 20-25KTS (STRONGEST ACROSS NORTHEAST MO/WEST- CENTRAL IL). A
SURFACE HIGH SLIDES SOUTH INTO THE AREA TOMORROW EVENING, LEADING
TO LIGHT AND VARIABLE WINDS WEDNESDAY NIGHT.
PEINE
LSX WATCHES/WARNINGS/ADVISORIES
MO...NONE.
IL...NONE.
WFO LSX
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