571
FXUS63 KLOT 171802
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
1202 PM CST SUN NOV 17 2024
KEY MESSAGES
- PERIODS OF RAIN ARE EXPECTED MONDAY THROUGH TUESDAY MORNING.
- ANOTHER SYSTEM WILL MOVE IN WEDNESDAY THROUGH THURSDAY WITH
ADDITIONAL CHANCES FOR PRECIPITATION, AND POSSIBLY THE FIRST
WET SNOWFLAKES OF THE SEASON.
- A COLDER AIR MASS WILL SETTLE IN LATE NEXT WEEK WITH MORNING
LOW TEMPERATURES AT OR BELOW FREEZING.
DISCUSSION
ISSUED AT 328 AM CST SUN NOV 17 2024
THROUGH MONDAY:
A MID-LEVEL WAVE THAT LIFTED JUST NORTH AND WEST OF THE AREA
LAST EVENING HAS LEFT A COINCIDENT NARROW AXIS OF MID TO UPPER-
LEVEL MOISTURE AND WEAK F-GEN ALIGNED ROUGHLY PARALLEL TO THE
I-55 CORRIDOR EARLY THIS MORNING. WITH CLOUD BASES AROUND 15KFT
AND A DEEP RESERVOIR OF DRY AIR BELOW THIS LAYER, PRECIP AT THE
SURFACE SHOULD BE LIMITED TO ONLY SOME SPARSE SPRINKLES THROUGH
THE MORNING.
A WEAK COLD FRONT CURRENTLY DRIFTING SOUTHEAST ACROSS CENTRAL
IOWA WILL BEGIN STALLING ACROSS THE FORECAST AREA THIS AFTERNOON
AND EVENING, ULTIMATELY SETTLING OVER OR JUST SOUTH OF THE FAR
SOUTHERN CWA LATER TONIGHT. ABOVE THIS FRONT, ANOTHER AXIS OF
MID-LEVEL F-GEN ALIGNING WITH MODEST MID-LEVEL MOISTURE MAY
AGAIN PRODUCE A CORRIDOR OF ISOLATED SHOWERS OR SPRINKLES AS IT
DRIFTS SOUTHEAST ACROSS THE AREA THROUGH THE AFTERNOON AND
EVENING. OVERALL, MUCH OF THE FORECAST AREA WILL REMAIN DRY
THROUGH THIS EVENING. TEMPS TODAY WILL RUN WELL ABOVE NORMAL
WITH HIGHS IN THE UPPER 50S TO AROUND 60F, WITH THE CHANCE FOR
TEMPS TO SLIGHTLY OVERPERFORM IF MID/UPPER-LEVEL CLOUD COVER
THINS BETWEEN THE TWO FEATURES NOTED ABOVE.
THE STALLED FRONT TO THE SOUTH WILL TRANSITION TO A NORTHWARD
DRIFTING WARM FRONT LATE TONIGHT IN RESPONSE TO A DEVELOPING LEE
CYCLONE OVER THE SOUTHERN HIGH PLAINS. A WEAKENING AXIS OF LOW-
LEVEL WAA AND ISENTROPIC ASCENT WILL SHIFT NORTHEASTWARD ACROSS
THE FORECAST AREA THROUGH THE DAY MONDAY AS DEEPER MOISTURE
ADVECTS INTO THE MID-MISSISSIPPI RIVER VALLEY. WHILE THE BEST
MOISTURE TRANSPORT MAY REMAIN WEST OF THE FORECAST AREA, A
CORRIDOR OF RAIN SHOULD AFFECT MOST LOCATIONS FOR A 3 TO 5 HOUR
PERIOD.
KLUBER
MONDAY NIGHT THROUGH SATURDAY:
FOCUS IN THIS PERIOD OF THE FORECAST CONTINUES TO BE ON TWO
PRECIPITATION-PRODUCING SYSTEMS, ONE MONDAY NIGHT INTO TUESDAY
AND THE OTHER WEDNESDAY THROUGH THURSDAY. AFTER ABOVE AVERAGE
WARMTH EARLY IN THE WEEK, A SHIFT TO COLDER AND MORE SEASONABLE
TEMPERATURES IS EXPECTED WITH THE MID-WEEK SYSTEM. THIS
TRANSITION MAY PRODUCE THE FIRST WET SNOWFLAKES OF THE SEASON
WEDNESDAY NIGHT INTO EARLY THURSDAY.
DEEP, SUB-990 HPA SURFACE LOW PRESSURE IS PROGGED TO BE LIFTING
NORTH-NORTHEAST FROM THE CENTRAL PLAINS INTO THE UPPER MIDWEST
MONDAY NIGHT, IN ASSOCIATION WITH A POTENT NEGATIVE-TILT SHORT
WAVE. STRONG FORCING FOR ASCENT ASSOCIATED WITH THIS WAVE, AND A
NORTHEAST MOVING OCCLUDING FRONTAL SYSTEM WILL SPREAD RAIN
ACROSS THE AREA MONDAY NIGHT INTO EARLY TUESDAY. AS THE SYSTEM
OCCLUDES, A MID-LEVEL DRY SLOT WILL MOVE IN ALOFT WHICH WILL
RESULT IN RAIN TAPERING TO SCATTERED SHOWERS FROM SOUTHWEST TO
NORTHEAST TUESDAY MORNING. VARIOUS MODEL ENSEMBLES DEPICT TOTAL
RAINFALL AMOUNTS FROM A QUARTER TO A HALF INCH IN OUR EASTERN
COUNTIES TO UPWARDS OF THREE QUARTERS OF AN INCH FARTHER TO THE
WEST. CAN'T RULE OUT SOME LINGERING DRIZZLE OR SPOTTY SHOWERS
ESPECIALLY ACROSS FAR NORTHEAST IL AND NORTHWEST IN INTO TUESDAY
AFTERNOON, THOUGH MOST AREAS WILL LIKELY BE DRY FROM LATER IN
THE MORNING THROUGH TUESDAY NIGHT. MILD AND BREEZY CONDITIONS
ARE EXPECTED, WITH DAYTIME HIGHS IN THE 55-60 DEGREE RANGE AND
SOUTHWEST WINDS GUSTING NEAR 25 MPH.
FARTHER UPSTREAM TO OUR WEST, GUIDANCE CONTINUES TO INDICATE
ANOTHER STRONG JET STREAK AND ASSOCIATED SHORT WAVE WHICH WILL
STRENGTHEN ACROSS THE SOUTH-CENTRAL PLAINS TUESDAY, COMBINING
EFFORTS WITH THE AFOREMENTIONED UPPER MIDWEST WAVE TO DEVELOP A
DEEP CLOSED LOW OVER THE UPPER MIDWEST TUESDAY NIGHT. VARIOUS
MODELS CONTINUE TO SHOW DIFFERENCES IN THE DETAILS AT THIS
DISTANCE, NOT SURPRISING GIVEN THE RELATIVELY COMPLEX EVOLUTION
OF THE UPPER LOW. THE EPS AND CMC ENSEMBLES SEEM TO BE IN DECENT
AGREEMENT HOWEVER, WHILE THE GEFS IS WEAKER AND FARTHER NORTH
WITH THE UPPER LOW. IN THE EPS/CMCE SCENARIO, NEW SURFACE LOW
PRESSURE DEVELOPS ALONG THE OLD OCCLUDED FRONTAL TROUGH TO OUR
NORTHEAST ACROSS THE GREAT LAKES WEDNESDAY, DEEPENING AND
THEN LINGERING IN THE LAKE MICHIGAN/LOWER MICHIGAN VICINITY
THROUGH THURSDAY AS THE UPPER LOW TRACKS ACROSS THE REGION. AS
THIS OCCURS, LOW-LEVEL COLD ADVECTION RAMPS UP FROM THE WEST
INTO THE MIDWEST/OHIO VALLEY WEDNESDAY, WHILE PRECIPITATION
REDEVELOPS BENEATH THE UPPER LOW TRACK. THIS STARTS THE LONG-
ANTICIPATED COOL DOWN IN TEMPERATURES WHICH WILL PERSIST
THROUGH THE WEEKEND.
PERIODS OF RAIN/SHOWERS WHICH DEVELOP ACROSS THE AREA WEDNESDAY
MAY BECOME MIXED WITH WET SNOW ACROSS MUCH OF THE AREA
WEDNESDAY NIGHT INTO EARLY THURSDAY, AS THE COLUMN COOLS BENEATH
THE UPPER LOW (EPS/CMCE 850 HPA TEMPS DIP AS LOW AS -8C
OVERNIGHT) AND SURFACE TEMPERATURES COOL INTO THE LOW-MID 30S.
AS THE UPPER LOW AND COLD POOL MOVE OFF TO THE EAST OF THE AREA
THURSDAY, LINGERING PRECIP SHOULD SHIFT BACK TO ALL-LIQUID.
SHOWERS MAY LINGER ACROSS MAINLY THE EASTERN PARTS OF THE
FORECAST AREA AND LAKE MICHIGAN INTO FRIDAY, AROUND THE TRAILING
PERIPHERY OF THE SLOWLY DEPARTING DISTURBANCE. BLUSTERY AND
COLDER WEATHER WILL LINGER INTO THE WEEKEND HOWEVER, WITH DAILY
HIGHS IN THE LOW-MID 40S AND OVERNIGHT LOWS IN THE 20S AND LOW
30S IN MOST SPOTS - ACTUALLY ABOUT AVERAGE FOR LATE NOVEMBER.
RATZER
AVIATION /18Z TAFS THROUGH 00Z TUESDAY/
ISSUED AT 1200 PM CST SUN NOV 17 2024
THE MAIN AVIATION WEATHER CONCERNS FOR THE 18Z TAF PERIOD
INCLUDE:
* MVFR CIGS MONDAY MORNING POSSIBLY DROPPING TO IFR DURING THE
DAY
* WIDESPREAD SHOWERS MONDAY AFTERNOON WITH ASSOCIATED VSBY
REDUCTIONS
* FOG POSSIBLE TONIGHT ACROSS ALL SITES. AT RFD, FOG EXPECTED
TONIGHT WITH IFR/LIFR VSBYS POSSIBLE
SW WINDS WILL CONTINUE TO MOVE AT 10 TO, AT TIMES, NEAR 20 KT
THROUGH THE REMAINDER OF THIS AFTERNOON BEFORE GOING LIGHT AND
VARIABLE FOR THIS EVENING AND TONIGHT. EXPECT SE WINDS NEAR 10
KT DURING THE DAY TOMORROW.
THERE HAS BEEN A GROWING SIGNAL FOR FOG TO DEVELOP AT THE
TERMINALS TONIGHT INTO EARLY TOMORROW, ESPECIALLY AT RFD WHERE
DENSE FOG MAY TAKE HOLD. MOST RECENT MODEL GUIDANCE SUGGESTS A
SEVERAL HOUR PERIOD OF AT LEAST IFR VSBYS AT RFD, ALTHOUGH LIFR
CERTAINLY APPEARS TO BE IN THE CARDS. DIDN'T THINK THE
CONFIDENCE WAS QUITE THERE YET TO INCLUDE A FORMAL FOG MENTION
IN THE CHICAGOLAND TAFS, ALTHOUGH ONE WILL LIKELY NEED TO BE
ADDED IN A LATER ISSUANCE IF THIS TREND CONTINUES.
MVFR CIGS ARE EXPECTED TO MOVE OVER THE TERMINALS MONDAY
MORNING. TIMING IS SOMEWHAT UNCERTAIN ON THE ONSET OF MVFR.
MOST MODELS ARE CLUSTERING AROUND THE MID-LATE MORNING
TIMEFRAME, BUT THERE IS A SIGNAL FOR EARLIER IN THE MORNING.
EARLY IN THE AFTERNOON, SHOWERS WILL OVERSPREAD THE AREA FROM
THE SOUTH AND CONTINUE THROUGH THE AFTERNOON. CIGS WILL BE QUICK
TO DROP FURTHER FOLLOWING THE ONSET OF RAIN, AT LEAST TO LOW-
END MVFR BUT IT'S LOOKING LIKE WE'RE HEADED FOR IFR OR EVEN A
PERIOD OF LIFR CIGS DURING THE AFTERNOON TOMORROW. IFR TO LIFR
VSBYS WILL ALSO BE VERY POSSIBLE WITH THE RAIN. SUCH CONDITIONS
WILL TAKE US THROUGH THE CURRENT 30-HR TAF PERIOD.
DOOM
LOT WATCHES/WARNINGS/ADVISORIES
IL...NONE.
IN...NONE.
LM...NONE.
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