227
FXUS63 KLOT 171946
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
146 PM CST SUN NOV 17 2024
KEY MESSAGES
- AREAS OF FOG ARE POSSIBLE OVERNIGHT, GENERALLY WEST OF THE
CHICAGO METRO.
- PERIODS OF RAIN ARE EXPECTED MONDAY THROUGH TUESDAY MORNING
ALONG WITH A SLIGHT CHANCE OF THUNDERSTORMS MONDAY NIGHT.
- 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 146 PM CST SUN NOV 17 2024
THROUGH MONDAY NIGHT:
A WEAK COLD FRONTAL BOUNDARY WILL SAG INTO THE AREA TONIGHT AND
LIKELY BECOME THE FOCUS FOR SOME FOG DEVELOPMENT GENERALLY WEST
OF THE METRO AREA AND NORTH OF I-80. CONFIDENCE REMAINS LOW FOR
HOW WIDESPREAD THE FOG MAY BECOME AS WELL AS HOW LOW
VISIBILITIES MAY DROP BUT WITH LIGHT WINDS AND AT LEAST PARTIAL
CLEARING ACROSS THE NORTH, THE SET-UP FOR FOG LOOKS DECENT GIVEN
THE FRONTAL BOUNDARY LOCATION. TRENDS WILL NEED TO BE MONITORED
INTO TONIGHT FOR REFINEMENT.
THERE MAY ALSO BE A FEW SHOWERS OR SPRINKLES THIS AFTERNOON INTO
THIS EVENING. MOST AREAS WILL PROBABLY REMAIN DRY BUT HAVE
CONTINUED LOW CHANCE POPS FOR THIS POTENTIAL WHICH MAY GET INTO
THE I-80 CORRIDOR BY EARLY EVENING AND THEN PRECIP CHANCES
APPEAR TO END FOR THE REST OF TONIGHT. LOW TEMPS ARE BIT TRICKY
TONIGHT, POSSIBLY DROPPING INTO THE MID 30S ACROSS THE NORTHWEST
CWA TO MID TO POSSIBLY UPPER 40S ACROSS THE SOUTHERN CWA WITH
EXPECTED CLOUD COVER REMAINING IN THESE AREAS.
AS LOW PRESSURE LIFTS NORTH ACROSS THE CENTRAL PLAINS MONDAY, AN
AREA OF LIGHT RAIN OR SHOWERS IS EXPECTED TO MOVE ACROSS THE
LOCAL AREA AHEAD OF A WARM FRONT. STILL SOME UNCERTAINTY FOR THE
EASTERN EXTENT OF THIS PRECIP, NORTHWEST IN COULD REMAIN FAIRLY
DRY, BUT PRECIP IS EXPECTED TO LIFT NORTH THROUGH CENTRAL IL IN
THE MID MORNING AND THEN ACROSS NORTHERN IL DURING THE EARLY/MID
AFTERNOON. OVERALL, THIS PRECIPITATION LOOKS TO BE FAIRLY LIGHT,
MAYBE A FEW TENTHS OF AN INCH ACROSS THE WESTERN CWA. THERE WILL
LIKELY BE A BREAK IN THE PRECIP, PERHAPS RATHER SHORT IN
DURATION, IN THE LATE AFTERNOON, BEFORE ANOTHER ROUND OF SHOWERS
MOVES ACROSS THE AREA MONDAY NIGHT. MODELS SHOW A NARROW AXIS
OF PRECIPITABLE WATER VALUES IN THE 1.5 INCH RANGE MOVING ACROSS
THE AREA MONDAY EVENING AS SURFACE DEWPOINTS CLIMB INTO THE MID
TO UPPER 50S. WITH SOME WEAK INSTABILITY, BOTH ISOLATED
THUNDERSTORMS AND LOCALIZED HEAVY RAIN WILL BE POSSIBLE MONDAY
EVENING AND HAVE ADDED SLIGHT CHANCE THUNDER WITH THIS FORECAST.
SCATTERED SHOWERS WILL LIKELY CONTINUE INTO THE PREDAWN HOURS
EARLY TUESDAY MORNING.
WINDS WILL TURN SOUTHEASTERLY MONDAY MORNING AND SLOWLY INCREASE
THROUGH THE DAY WITH GUSTS INTO THE 25-30 MPH RANGE POSSIBLE BY
EARLY MONDAY EVENING. WHILE THERE REMAINS UNCERTAINTY FOR HOW
STRONG THE WINDS WILL BECOME MONDAY NIGHT, BOTH THE GRADIENT AND
THE LOW LEVEL WINDS WOULD SUGGEST WIND GUSTS INTO THE 35 MPH
RANGE WILL BE POSSIBLE, PERHAPS A FEW HIGHER GUSTS AT TIMES.
WINDS MAY MAY DIMINISH SOME OVERNIGHT/EARLY TUESDAY MORNING AS
THEY BEGIN TO TURN MORE SOUTHERLY. ALSO FOR MONDAY NIGHT, TEMPS
ARE LIKELY TO STAY FAIRLY MILD, LIKELY IN THE 50S. CMS
TUESDAY THROUGH SUNDAY:
LINGERING SHOWERS ARE POSSIBLE THROUGH TUESDAY MORNING,
PARTICULARLY CLOSER TO THE LAKE. HOWEVER, MUCH OF THE AREA IS
EXPECTED TO HAVE DRIER CONDITIONS AS THE LOW IS PROJECTED TO
CONTINUE ITS TRACK AWAY TO THE NORTHEAST. SOUTH TO SOUTHEAST
WINDS WILL GRADUALLY VEER TO THE SOUTHWEST BEHIND THE FRONT AND
STAY BREEZY THROUGH THE MORNING, BEFORE DIMINISHING IN THE
AFTERNOON.
AN UPPER LEVEL LONG WAVE TROUGH OVER THE NORTHERN PLAINS IS
EXPECTED TO DIG SOUTHEASTWARD AND DEEPEN WEDNESDAY THROUGH
THURSDAY. AS IT DOES, A SURFACE LOW WILL DEVELOP NEAR THE
CENTRAL GREAT LAKES, PIVOTING AROUND SLIGHTLY BEFORE MOVING OVER
NEW ENGLAND LATE IN THE WEEK. THE CANADIAN AND EURO MODELS HAVE
SLOWLY STARTED TO SHOW BETTER AGREEMENT WITH THE SURFACE LOW
FORMATION, WHILE THE GEFS REMAINS FARTHER NORTH AND EAST OF THE
AREA, LIMITING CONFIDENCE AT THIS TIME. THERE STILL REMAINS
QUESTIONS HOW EXACTLY THE UPPER LEVEL WAVE WILL PHASE WITH THE
PREVIOUS SHORT WAVE AS IT MOVES EAST.
NEVERTHELESS, AS THE 500 MB WAVE MOVES OVER THE REGION ON
WEDNESDAY, IT IS PROJECTED TO HAVE A STRONG JET STREAK
ASSOCIATED WITH IT, WHOSE LEFT EXIT REGION SHOULD PASS OVER THE
AREA TO PROVIDE ADDITIONAL SYNOPTIC LIFT. WITH TEMPERATURES
STILL ABOVE FREEZING WEDNESDAY MORNING, THE FIRST CHANCES FOR
PRECIPITATION ARE EXPECTED TO BE IN FORM OF RAIN. HOWEVER, WITH
BETTER COLD AIR ADVECTION ON THE BACK SIDE OF THE TROUGH, IT IS
LIKELY THAT BY WEDNESDAY NIGHT INTO THURSDAY MORNING 850 MB
TEMPERATURES ARE AT OR BELOW -5C AND A 20 TO 30 PERCENT CHANCE
FOR 850 MB TEMPS DOWN TO -10C. PERIODS OF RAIN/SHOWERS MAY
BECOME MIXED WITH WET SNOW ACROSS MUCH OF THE AREA WEDNESDAY
NIGHT INTO EARLY THURSDAY. AS THE UPPER LOW MOVES EAST OF THE
AREA THURSDAY, LINGERING PRECIP SHOULD SHIFT BACK TO ALL-LIQUID.
STRONG WINDS ARE EXPECTED OUT OF THE WEST ON WEDNESDAY BEFORE
BECOMING NORTHWESTERLY ON THURSDAY, INCREASING AS THE THE
SURFACE LOW DEEPENS SETTING UP FOR A BREEZIER COUPLE OF DAYS.
THERE IS LOWER CONFIDENCE IN THE MAXIMUM WIND SPEED DURING THIS
TIME FRAME GIVEN THE UNCERTAINTY AROUND THE LOCATION AND DEPTH
OF THE PRESSURE SYSTEM.
AS THIS SYSTEM SLOWLY EXITS THE REGION FROM LATE THURSDAY INTO
FRIDAY, PREVAILING NORTHWESTERLY FLOW WILL ALLOW LINGERING
SHOWERS AROUND LAKE MICHIGAN. TEMPERATURES WILL REMAIN CHILLY
WITH MORNING LOWS AT OR BELOW FREEZING THROUGH THE WEEKEND WITH
HIGH TEMPERATURES ONLY REACHING THE LOW 40S.
DK
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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