024
FXUS63 KLOT 150504
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
1104 PM CST THU NOV 14 2024
KEY MESSAGES
- LOW CHANCE (20%) OF SHOWERS SATURDAY NIGHT INTO SUNDAY.
- PERIODS OF RAIN EXPECTED MONDAY NIGHT.
- A COOLER WEATHER PATTERN, POTENTIALLY ACCOMPANIED BY PERIODIC
SHOWERS, MAY MATERIALIZE MID-LATE NEXT WEEK AND CONTINUE TOWARD
THE END OF THE MONTH.
UPDATE
ISSUED AT 819 PM CST THU NOV 14 2024
THE ONLY MINOR CHANGE FOR THE EVENING UPDATE WAS TO ADD A
MENTION OF PATCHY DRIZZLE TO THE GRIDS THIS EVENING. RECENT
PIREPS INDICATE CLOUD TOPS ARE AROUND 4 KFT, AND WITH BASES
NEAR 1 KFT, THIS 3 KFT-DEEP LAYER COMBINED WITH JUST A SMIDGE OF
ASCENT HAS BEEN ENOUGH TO SQUEEZE OUT SOME VERY LIGHT DRIZZLE.
BASED ON LATEST MODEL GUIDANCE, THE DEEPEST MOISTURE IS FORECAST
TO FOCUS ACROSS ROUGHLY THE NORTHEASTERN HALF OF THE CWA, AND
HAVE GENERALLY CONFINED THE DRIZZLE MENTION TO THESE LOCALES.
BASED ON UPSTREAM TRENDS, SOME VISIBILITY REDUCTIONS INTO THE
3-5 MILE RANGE CAN'T BE RULED OUT, BUT THIS GENERALLY LOOKS LIKE
A VERY LIGHT DRIZZLE SET UP. THANKFULLY, NO CONCERNS WITH FZDZ
THIS TIME AROUND. OTHERWISE, LOOKS LIKE WE'LL REMAIN GENERALLY
SOCKED IN WITH LOW CLOUD COVER TONIGHT, WITH ANY FOG POTENTIALLY
REMAINING WELL WEST OF THE REGION.
CARLAW
DISCUSSION
ISSUED AT 136 PM CST THU NOV 14 2024
THROUGH FRIDAY NIGHT:
WE'RE FIRMLY ENTRENCHED IN "STRATUS SEASON", A COMMON COOL SEASON
PATTERN WHEN RELATIVELY STAGNANT CONDITIONS MORE OR LESS KEEP
EXISTING LOW CLOUD DECKS LOCKED IN. AS OF EARLY AFTERNOON, WITH
SOME EXCEPTIONS, STRATUS EXTENDS BACK ALMOST TO THE IA/NE BORDER
AND THEN UP TO THE EASTERN DAKOTAS. WITH MINIMAL COLD AND DRY AIR
ADVECTION THROUGH TONIGHT AND THEN WARMING ALOFT ON FRIDAY SERVING
TO STRENGTHENING AN ALREADY STOUT LOWER LEVEL INVERSION, IT'S
TOUGH TO PINPOINT ANY TIMEFRAMES OF MEANINGFUL CLEARING.
SOME OF THE GLOBAL GUIDANCE SUGGESTS SOME EROSION IS POSSIBLE
FROM THE WEST FRIDAY AFTERNOON, WHILE HIGHER RESOLUTION GUIDANCE
(WHICH TYPICALLY HANDLES THESE PATTERNS BETTER) SUPPORTS A MOSTLY
CLOUDY FORECAST THROUGHOUT. CAN'T RULE OUT MECHANICAL MIXING AND
SUBTLE DRYING RESULTING IN HOLES IN THE STRATUS. HOWEVER, THE LOW
LEVEL FLOW SHIFTING FROM NORTHWESTERLY TO LIGHT SOUTHEASTERLY
LATER FRIDAY SHOULD CAUSE A BACK EDGE OF THE CLOUDS (IF IT
APPROACHES PARTS OF OUR WESTERN CWA), TO "SLOSH" BACK WEST-
NORTHWEST THROUGH FRIDAY NIGHT. WITH ALL THE ABOVE BEING SAID,
BUMPED UP SKY COVER TO OVERCAST TONIGHT AND MOSTLY CLOUDY THROUGH
FRIDAY NIGHT. THIS WILL ALSO LIMIT THE DIURNAL TEMPERATURE RANGE,
RESULTING IN MILDER LOWS (GENERALLY SOLIDLY ABOVE 40F) AND
SLIGHTLY COOLER HIGH TEMPS (LOWER-MID 50S) ON FRIDAY.
THERE ARE OTHERWISE NO WEATHER IMPACT CONCERNS OF NOTE. A
MARGINAL THERMODYNAMIC SETUP COULD RESULT IN SPOTTY NORTHWEST FLOW
DRIVEN LAKE EFFECT SHOWERS INTO PORTIONS OF PORTER COUNTY
TONIGHT.
CASTRO
SATURDAY THROUGH THURSDAY:
A DISSIPATING COLD FRONT IS EXPECTED TO BE MOVING ACROSS THE
AREA SATURDAY AFTERNOON INTO SATURDAY NIGHT. THIS MAY ALLOW FOR
SOME SHOWERS, PARTICULARLY SATURDAY NIGHT THOUGH ISOLATED
SHOWERS MAY PERSIST INTO SUNDAY. LOW CHANCE POPS SEEM FINE FOR
NOW WITH LOW COVERAGE IF ANYTHING DEVELOPS.
THE NEXT STORM SYSTEM WILL DEVELOP IN THE SOUTHERN PLAINS SUNDAY
INTO SUNDAY NIGHT AND LIFT NORTH TO NEAR IA BY TUESDAY MORNING.
A WARM FRONT WILL LIFT NORTH ACROSS THE LOCAL AREA BRINGING
PERIODS OF RAIN MONDAY NIGHT WHICH IF CURRENT TIMING HOLDS, MAY
BE TRANSITIONING TO SHOWERS OR ENDING BY DAYBREAK TUESDAY
MORNING. AFTER HIGH TEMPS IN THE 50S ON MONDAY, TEMPS MAY HOLD
STEADY OR AFTER AN EVENING DIP SLOWLY RISE BACK INTO THE LOWER
TO MID 50S MONDAY NIGHT. HIGH TEMPS ON TUESDAY COULD BE IN THE
MORNING WITH STEADY OR SLOWLY FALLING TEMPS IN THE AFTERNOON,
DEPENDING ON HOW FAST AND TO WHAT EXTENT COOLER AIR SPREADS
INTO THE AREA DURING THE DAY. SOUTHWEST WINDS MAY ALSO BECOME
RATHER GUSTY TUESDAY, PERHAPS INTO THE 30 MPH RANGE.
WHILE A COOLER PATTERN CHANGE IS STILL SUPPORTED BY THE
ENSEMBLES LATER NEXT WEEK, AFTER TUESDAY, THERE IS STILL SOME
UNCERTAINTY AS TO WHEN AND TO WHAT EXTENT THIS CHANGE OCCURS. AS
WELL AS TO HOW LONG IT MAY PERSIST BEFORE TEMPERATURES BEGIN TO
MODERATE. IF A LARGE UPPER LOW WERE TO PERSIST OVER THE AREA FOR
SEVERAL DAYS, THE MAIN STORY MIGHT BE THE CLOUDY/SHOWERY WEATHER
RATHER THAN HOW COLD THE TEMPS ARE. BUT THIS TIME PERIOD IS
STILL A WEEK AWAY AND ITS TOO EARLY FOR DETAILS. GIVEN THE
WARMER BLENDED GUIDANCE, ALL FORECAST PRECIP TYPES REMAIN LIQUID
THROUGH THE END OF THE PERIOD. CMS
AVIATION /06Z TAFS THROUGH 12Z SATURDAY/
ISSUED AT 1104 PM CST THU NOV 14 2024
FORECAST CONCERNS FOR THE TERMINALS...
- PERIODS OF DRIZZLE POSSIBLE THROUGH 08-09Z
- MVFR CEILINGS TO PREVAIL THROUGH FRIDAY NIGHT
A FEW BANDS OF DRIZZLE HAVE DEVELOPED WITHIN THE LAST COUPLE OF
HOURS ACROSS SOUTHERN WI AND NORTHEAST IL IN THE WAKE OF AN
UPPER TROUGH. WHILE MOISTURE DEPTHS CONTINUE TO BE MARGINAL,
DRIZZLE DOES LOOK TO LINGER THROUGH AT 08Z TO 09Z TONIGHT AT THE
CHICAGO AREA TERMINALS AS SOME LAKE INDUCED INSTABILITY
PERSISTS. SO FAR THE DRIZZLE HAS NOT GENERATED ANY NOTABLE
VISIBILITY CHANGES AND THAT IS EXPECTED TO REMAIN THE CASE, BUT
ISOLATED POCKETS OF 3-5 SM MAY OCCUR AT TIMES. FURTHERMORE,
POCKETS OF IFR CEILINGS HAVE BEEN OBSERVED IN WI WHICH ARE
EXPECTED TO REMAIN POSSIBLE WITH THE DRIZZLE THIS EVENING.
THOUGH CONFIDENCE ON LONGEVITY OF IFR REMAINS LOW SO HAVE
DECIDED TO HANDLE WITH A SCT MENTION FOR NOW.
OTHERWISE, EXPECT THE MVFR CEILINGS TO PREVAIL THROUGH FRIDAY
NIGHT AS THE LOW-LEVEL MOISTURE BECOMES TRAPPED BENEATH THE
BUILDING SURFACE HIGH. HOWEVER, SOME POCKETS OF SUNSHINE MAY
POKE THROUGH THE CLOUDS FRIDAY AFTERNOON. WINDS WILL REMAIN
LIGHT THROUGH THE PERIOD, BUT DIRECTIONS WILL BECOME MORE EAST-
SOUTHEASTERLY FRIDAY NIGHT UNDER THE HIGH.
YACK
LOT WATCHES/WARNINGS/ADVISORIES
IL...NONE.
IN...NONE.
LM...NONE.
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