536
FXUS63 KLOT 180524
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
1124 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.
UPDATE
ISSUED AT 914 PM CST SUN NOV 17 2024
OVERALL THE PREVAILING FORECAST REMAINS ON TRACK THROUGH MONDAY
WITH VERY LITTLE CHANGES MADE THIS EVENING.
THE EARLIER BAND OF SHOWERS/SPRINKLES CONTINUES TO DISSIPATE AS
THE UPPER-LEVEL SHORTWAVE AND ASSOCIATED JET STREAK OVER
NORTHERN IL PIVOTS INTO LOWER MI. THUS, EXPECT PRECIPITATION TO
CONCLUDE WITHIN THE NEXT HOUR. HOWEVER, A WEAK FRONTAL BOUNDARY
IS BEGINNING TO STALL ACROSS THE AREA WHICH WILL SERVE AS THE
BREEDING GROUND FOR FOG TONIGHT INTO EARLY MONDAY MORNING. WHILE
THE GREATEST FOG POTENTIAL CONTINUES TO BE FOR AREAS IN FAR
NORTHERN AND NORTHWESTERN IL, THERE IS A GROWING CONCERN THAT
SOME PATCHY FOG COULD DEVELOP AS FAR SOUTH AS I-80 IF SUFFICIENT
CLEARING OF THE CLOUDS CAN OCCUR. THAT SAID, HAVE EXPANDED THE
PATCHY FOG MENTION TO INCLUDE AREAS ALONG AND NORTH OF I-80 TO
ACCOUNT FOR THIS POTENTIAL. IN TERMS OF VISIBILITY, GUIDANCE HAS
STARTED TO BACK OFF ON THE COVERAGE OF DENSE FOG TONIGHT DUE TO
AN ADDED UNCERTAINTY WITH A STRATUS DECK LIFTING OUT OF
NORTHEAST MO. THOUGH, THERE REMAINS A GOOD SIGNAL (40- 50%
CHANCE) FOR WIDESPREAD 4 TO 6 MILE VISIBILITIES WITH LOCALIZED
POCKETS OF VISIBILITIES UNDER 2 MILES PARTICULARLY IN NORTHWEST
IL. SINCE THE FORECAST VISIBILITIES ARE STILL ABOVE THE
THRESHOLD FOR A DENSE FOG ADVISORY WILL PLAN TO HOLD OFF ON A
HEADLINE FOR NOW, BUT WILL KEEP A CLOSE EYE ON TRENDS.
ASIDE FROM THE FOG, TEMPERATURES TONIGHT WILL VARY FROM NORTH
TO SOUTH DUE TO THE STALLED FRONT. THAT SAID, AREAS IN FAR
NORTHERN IL CAN EXPECT OVERNIGHT LOWS IN THE MID TO UPPER 30S
WHILE THE REST OF THE AREA SEES READINGS IN THE MID-40S. HEADING
INTO MONDAY, THE FOG WILL ERODE BY MID-MORNING AS WINDS BEGIN
TO INCREASE AHEAD OF OUR NEXT STORM SYSTEM. WHILE THE STRONGEST
WINDS SHOULD HOLD OFF UNTIL MONDAY EVENING, SOUTHEASTERLY GUSTS
OF 20-25 MPH ARE EXPECTED FOR MONDAY AFTERNOON. FURTHERMORE,
RAIN CHANCES WILL ALSO BE INCREASING THROUGH THE DAY AS THE
SYSTEMS WARM ADVECTION WING PIVOTS THROUGH. DESPITE THE RAIN AND
ASSOCIATED CLOUD COVER, TEMPERATURES STILL LOOK TO WARM INTO
THE MID TO UPPER 50S MONDAY AFTERNOON.
YACK
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 /06Z TAFS THROUGH 12Z TUESDAY/
ISSUED AT 1124 PM CST SUN NOV 17 2024
THE MAIN AVIATION WEATHER CONCERNS ARE:
- BR/FG DEVELOPMENT TONIGHT. GREATEST CONCERN NEAR RFD AND DPA.
- MVFR CIGS RE-DEVELOP LATE TONIGHT INTO MONDAY MORNING. FIRST
BATCH OF RAIN ARRIVES MIDDAY INTO MONDAY AFTERNOON.
- SECOND BATCH OF RAIN, PERHAPS WITH SOME EMBEDDED TS, ARRIVES
LATE MONDAY EVENING AND EARLY OVERNIGHT.
- TRANSITION TO SHOWERS/DRIZZLE AND LOW CLOUDS MONDAY NIGHT INTO
TUESDAY MORNING.
CLOUDS WILL CONTINUE TO ERODE FROM NORTH TO SOUTH LATE THIS
EVENING. LIGHT WINDS AND LOW-LEVEL MOISTURE WILL SET THE STAGE
FOR QUICK BR/FG DEVELOPMENT TONIGHT. THE MAIN FLY IN THE
OINTMENT IS THE BATCH OF EXPANSIVE HIGH-MVFR TO VFR STRATUS
SOUTH OF I-80 WHICH SHOULD VERY SLOWLY MEANDER NORTHWARD. IF
THIS EXPANDS MORE QUICKLY THAN EXPECTED, THEN THE FOG THREAT
WILL DIMINISH. THAT SAID, SATELLITE AND OBSERVATION TRENDS
SUGGEST VSBYS ARE TANKING QUICKLY AS CLOUDS CLEAR. THE WORST
CONDITIONS ARE CURRENTLY EXPECTED NEAR RFD, WHERE LIFR
CONDITIONS HAVE BEEN TEMPOD TONIGHT. A MORE DIFFICULT FORECAST
AT THE CHICAGO-AREA TERMINALS WHERE THE AFOREMENTIONED STRATUS
DECK WILL BE VERY CLOSE. FOR NOW, HAVE MADE MINIMAL CHANGES TO
THE PREVIOUS FORECAST, EXCEPT TO LOWER VSBYS A BIT AT DPA.
VSBYS WILL IMPROVE THROUGH MONDAY MORNING AS SOUTHEASTERLY WINDS
INCREASE. MVFR CIGS WILL RE-DEVELOP AREA-WIDE. A BATCH OF
SHOWERS WILL DEVELOP THROUGH ABOUT MIDDAY INTO THE LATE
AFTERNOON, WITH A BRIEF PERIOD OF IFR VSBYS POSSIBLE.
PRECIPITATION SHOULD THEN TREND MORE SPOTTY FOR A PERIOD BEFORE
A SECOND BATCH OF RAIN ARRIVES LATE MONDAY EVENING. EMBEDDED TS
WILL BE POSSIBLE AT THE LEADING EDGE OF THIS WAVE OF
PRECIPITATION, ALTHOUGH CONFIDENCE IN THIS REMAINS A BIT TOO LOW
FOR A MENTION IN THE TAFS. EVENTUALLY, PRECIP WILL TREND TOWARDS
DRIZZLE INTO EARLY TUESDAY MORNING.
LIGHT AND VARIABLE WINDS TONIGHT WILL BECOME SOUTHEASTERLY
THROUGH MONDAY MORNING. THEY WILL THEN INCREASE STEADILY THROUGH
LATE MONDAY AFTERNOON AND EVENING, WITH GUSTS TOWARDS 30 KNOTS
POSSIBLE MONDAY NIGHT. WITH THE EXPECTED SURFACE GUSTS, HAVE
LEFT OUT A MENTION OF LLWS AT ALL THE TERMINALS AT THIS TIME.
CARLAW
LOT WATCHES/WARNINGS/ADVISORIES
IL...NONE.
IN...NONE.
LM...NONE.
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