044
FXUS63 KLOT 170314
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
914 PM CST SAT NOV 16 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.
- A COLDER AIR MASS WILL SETTLE IN LATE NEXT WEEK WITH MORNING
LOW TEMPERATURES AT OR BELOW FREEZING.
UPDATE
ISSUED AT 914 PM CST SAT NOV 16 2024
A BROAD SHORTWAVE TROUGH AND ITS ASSOCIATED SURFACE LOW CONTINUE
TO TRAVERSE ACROSS THE NORTHERN PLAINS THIS EVENING WITH THE
SYSTEMS OCCLUDING FRONTAL BOUNDARY STRETCHING FROM CENTRAL MN
SOUTHWESTWARD INTO IA AND EASTERN NE. AHEAD OF THE FRONT, A BAND
OF SHOWERS HAS DEVELOPED ON THE NOSE OF A PLUME OF ELEVATED
INSTABILITY AND CONTINUES TO TRACK EAST TOWARDS NORTHERN IL.
DESPITE THE ROBUST LOOK ON RADAR, RECENT SURFACE OBSERVATIONS
SHOW THAT THE MAJORITY OF THESE SHOWERS ARE NOT REACHING THE
GROUND. SINCE MOISTURE IN THE SUB-CLOUD LAYER IS NOT EXPECTED TO
IMPROVE MUCH OVERNIGHT, SUSPECT THAT SHOWERS WILL STRUGGLE TO BE
MUCH MORE THAN SPRINKLES AS THEY PASS OVERHEAD TONIGHT.
HOWEVER, MOSTLY TO COMPLETELY CLOUDY SKIES ARE EXPECTED TONIGHT
AS THE SHOWERS/SPRINKLES PASS. THUS TEMPERATURES ARE NOT
EXPECTED TO CHANGE MUCH FROM THEIR CURRENT READINGS WITH
OVERNIGHT LOWS IN THE LOW TO MID-40S (UPPER 40S IN CHICAGO)
FORECAST. WINDS ON THE OTHER HAND WILL REMAIN ELEVATED TONIGHT
WITH OCCASIONAL GUSTS IN THE 15-20 MPH RANGE OUT OF THE
SOUTH-SOUTHEAST.
AS FOR SUNDAY, THE SHOWERS/SPRINKLES TONIGHT WILL EXIT THE AREA
BY MID-MORNING LEAVING US WITH MOSTLY DRY CONDITIONS OTHERWISE.
THOUGH, CONFIDENCE IS INCREASING THAT ADDITIONAL SHOWERS MAY
DEVELOP SUNDAY AFTERNOON AS THE AFOREMENTIONED FRONT PIVOTS
THROUGH NORTHERN IL AND INTERACTS WITH A STRONG JET STREAK AND
ASSOCIATED VORT MAX. GIVEN THAT THE COVERAGE OF SHOWERS SUNDAY
AFTERNOON REMAINS LOWER CONFIDENCE DUE TO AVAILABLE MOISTURE,
HAVE DECIDED TO INTRODUCE ONLY SLIGHT CHANCE (AROUND 20%) POPS
TO THE FORECAST FOR NOW. IF THIS TREND CONTINUES WOULD NOT
BE SURPRISED IF HIGHER POPS ARE INTRODUCED BY INCOMING MIDNIGHT
SHIFT. REGARDLESS, TEMPERATURES ARE STILL EXPECTED TO BE ABOVE
NORMAL FOR MID-NOVEMBER WITH HIGHS AROUND 60 DEGREES.
YACK
DISCUSSION
ISSUED AT 154 PM CST SAT NOV 16 2024
THROUGH SUNDAY NIGHT:
A WEAKENING COLD FRONT WILL MOVE ACROSS THE AREA SUNDAY MORNING
AND THEN LIKELY STALL ACROSS CENTRAL IL AND CENTRAL IN SUNDAY
NIGHT. THE GRADIENT WILL SUPPORT SOUTHERLY WINDS GUSTING INTO
THE 25 MPH TO PERHAPS 30 MPH RANGE TONIGHT. WINDS WILL TURN
MORE SOUTHWESTERLY SUNDAY MORNING AND REMAIN GUSTY.
THERE WILL ALSO BE A LOW CHANCE OF SHOWERS AHEAD OF THE FRONT
OVERNIGHT INTO SUNDAY MORNING. WITH SOMEWHAT DRIER LOW LEVELS,
ABOVE THE STRATUS, ITS POSSIBLE THERE COULD BE QUITE A BIT OF
VIRGA AND SOME SPRINKLES. BUT A FEW SHOWERS REMAIN POSSIBLE AND
NO CHANGES TO SLIGHT CHANCE POPS. THERE IS SOME UNCERTAINTY FOR
TIMING/LOCATION WITH A CONTINUED CHANCE ACROSS NORTHERN IL
SUNDAY AFTERNOON. DESPITE THE LOW CHANCES, SOME FURTHER
REFINEMENT WITH THE POPS IS LIKELY WITH LATER FORECASTS.
SOME BREAKS IN THE CLOUDS HAVE DEVELOPED EARLY THIS AFTERNOON
ALONG WITH SLOW BUT STEADY CLEARING FROM THE SOUTHEAST ACROSS
WEST CENTRAL IN. SOME PARTIAL CLEARING IS POSSIBLE INTO THIS
EVENING BUT OVERALL TRENDS STILL SUPPORT MOSTLY CLOUDY TONIGHT
AND INTO SUNDAY. SHOULD ANY CLEARING REMAIN PREVAILING TONIGHT,
THAT MAY ALLOW TEMPS TO DROP BELOW THE CURRENT FORECAST LOWS
WHICH ARE IN THE LOWER/MID 40S. HIGHS ON SUNDAY MAY DEPEND ON
CLOUD TRENDS WITH MOST AREAS LIKELY REACHING THE UPPER 50S AND
POSSIBLY AROUND 60. WITH SOME CLEARING EXPECTED SUNDAY NIGHT,
ESPECIALLY ACROSS THE NORTH, LOWS MAY DROP IN THE 30S ACROSS THE
NORTHWEST CWA. CMS
MONDAY THROUGH SATURDAY:
A LONG WAVE UPPER LEVEL TROUGH WILL BE SITUATED OVER THE
PACIFIC NORTHWEST ON MONDAY AND MOVE EASTWARD THROUGH THE MIDDLE
OF THE WEEK. OUT AHEAD OF IT, THERE WILL BE A SHORTER,
NEGATIVELY TILTED WAVE OVER NORTHERN MEXICO THAT WILL MOVE
NORTHEASTWARD TOWARD MINNESOTA MONDAY INTO TUESDAY MORNING.
MODELS ARE SUGGESTING THAT THE LEADING SHORT WAVE WILL WEAKEN
AND PHASE WITH THE LONGER WAVE IN THE MIDDLE OF THE WEEK, BEFORE
THE LONGER WAVE TROUGH STRENGTHENS AND FORMS A CLOSED LOW OVER
THE NORTHERN PLAINS THAT WILL MOVE EASTWARD THROUGH THE END OF
THE WEEK.
ASSOCIATED WITH THESE WAVES, WILL BE TWO WEATHER SYSTEMS THAT
WILL IMPACT NORTHERN ILLINOIS AND NORTHWEST INDIANA. THE FIRST
ON MONDAY INTO TUESDAY MORNING. AS A SURFACE LOW MOVES
NORTHEASTWARD THROUGH THE GREAT PLAINS MONDAY, A WARM FRONT WILL
MOVE OVER THE AREA PROVIDING ENOUGH FORCING TO INDUCE SHOWERS
FROM SOUTH TO NORTH THROUGH THE AFTERNOON. THE LOW IS PROJECTED
TO SLOWLY OCCLUDE AND WEAKEN THROUGH THE NIGHT, BUT NOT BEFORE
PUSHING A SECONDARY FRONT ACROSS THE AREA PROVIDING WIDESPREAD
RAIN MONDAY EVENING AND INTO TUESDAY MORNING. WINDS WILL BECOME
BREEZY TO AROUND 25 MPH OUT OF THE EAST TO SOUTHEAST AS THIS
SYSTEM APPROACHES, PARTICULARLY IN THE EVENING TIME FRAME AS THE
LOW LEVEL JET RAMPS UP. RAIN WILL SLOWLY TAPER OFF FROM
SOUTHWEST TO NORTHEAST THROUGH THE MORNING ON TUESDAY.
TEMPERATURES ARE EXPECTED TO REACH INTO THE LOW 60S IN THE
AFTERNOON, WITH DRIER CONDITIONS ON TUESDAY AHEAD OF THE NEXT
SYSTEM.
THERE HAS BEEN FAIRLY GOOD AGREEMENT AMONG MODELS ON THE RAIN
CHANCES FOR MONDAY/TUESDAY. HOWEVER, THAT CANNOT BE SAID ABOUT
THE SECOND SYSTEM LIKELY IMPACTING THE REGION BETWEEN WEDNESDAY
AND THURSDAY. MODELS HAVE STRUGGLED TO AGREE ON TIMING AND
LOCATION AS THIS SYSTEM MOVES EAST. IT RESULTS IN IMPACTING
CONFIDENCE IN THE FORECAST, ESPECIALLY WITH THE COLDER AIRMASS
MOVING IN BEHIND IT WHICH COULD INFLUENCE THE TYPE OF
PRECIPITATION.
AS THE UPPER LEVEL LONG WAVE MOVES EAST, A STRONG JET STREAK
WILL MOVE OVER THE MIDWEST AS A NEW SURFACE LOW DEVELOPS WEST OF
THE MISSISSIPPI RIVER. AS THE LOW MOVES TO THE NORTHEAST,
MODELS HAVE BEEN SUGGESTING IT WILL PINWHEEL AROUND WEDNESDAY
INTO THURSDAY BEFORE FINALLY DEPARTING TO THE EAST INTO FRIDAY.
THE LATEST GFS HAS THE LOW FORMING OVER CENTRAL OHIO AND
SPINNING OVER BUFFALO, WHILE THE EURO HAS IT FORMING OVER
INDIANA AND ENCIRCLING AROUND DETROIT WITH A DEEPER MINIMUM
PRESSURE. THE CONTINUED SIGNAL OF A SYSTEM MOVING THROUGH MID
WEEK KEEPS THE CHANCES FOR PRECIPITATION IN THE FORECAST;
HOWEVER, THE LACK OF AGREEMENT IN MODELS LOWERS CONFIDENCE IN
THE DETAILS OF WHAT IS AND WILL BE A COMPLEX SYSTEM.
TEMPERATURES ON WEDNESDAY SHOULD BE WARM ENOUGH TO SUPPORT
MAINLY RAIN FOR ANY SHOWERS THAT WOULD DEVELOP. DESPITE SURFACE
TEMPERATURES STAYING ABOVE 32F, 850 MB TEMPERATURES ON THE BACK
SIDE OF THE WAVE ARE EXPECTED TO PLUMMET BELOW FREEZING LEADING
TO THE POTENTIAL FOR THE FIRST SNOWFLAKES OF THE SEASON MIXED IN
WITH THE RAIN. BETTER CHANCES FOR SNOW WOULD LEAN TOWARD THE
MORE WESTERN SOLUTION OF THE EURO, AS OPPOSED TO THE GFS
SOLUTION BEING FARTHER TO THE EAST. FOR NOW, THE FORECAST
MAINTAINED JUST A SLIGHT CHANCE (15 PERCENT) FOR WET SNOW TO BE
MIXED IN FOR AREAS MAINLY SOUTH OF I-88 AND AWAY FROM LAKE
MICHIGAN, UNTIL MODELS (HOPEFULLY) COME INTO BETTER AGREEMENT.
THE OTHER IMPACT TO THE UNCERTAINTY ON THE STRENGTH AND
LOCATION OF THE LOW WILL BE TO THE WIND FORECAST. WINDS ARE
EXPECTED TO INCREASE ON THE BACKSIDE OF THE LOW AS IT MOVES
EAST OF THE REGION. WHILE THE FORECAST DEPICTS STRONGER WINDS
DEVELOPING, THERE COULD BE THE POTENTIAL TO INCREASE GUSTS
HIGHER DEPENDING ON IF CONFIDENCE INCREASES ON THE PLACEMENT OF
THE LOW.
CHANCES FOR PRECIPITATION DIMINISH AFTER THURSDAY AS THE SYSTEM
EVENTUALLY MOVES TO THE EAST OF THE AREA. THE EXCEPTION WAS TO
KEEP SLIGHT CHANCE TO CHANCE POPS (15 TO 35 PERCENT) AROUND LAKE
MICHIGAN DUE TO THE PREVAILING NORTHWEST FLOW THAT COULD
POTENTIALLY LEAD TO SOME LAKE EFFECT PRECIP INTO THE WEEKEND.
TEMPERATURES ARE EXPECTED TO DROP IN THE WAKE OF THIS SYSTEM
WITH HIGH TEMPERATURES THURSDAY THROUGH SATURDAY IN THE 40S WITH
OVERNIGHT LOWS FRIDAY AND SATURDAY MORNING AT OR BELOW
BREEZING.
DK
AVIATION /00Z TAFS THROUGH 06Z SUNDAY/
ISSUED AT 518 PM CST SAT NOV 16 2024
THE MAIN AVIATION WEATHER HIGHLIGHTS ARE:
* WIND TRENDS THIS EVENING--SSE WINDS BECOMING SW
* REDUCED POTENTIAL FOR MVFR CIGS TONIGHT INTO SUNDAY.
* BRIEF WINDOWS FOR PRECIPITATION: LATE THIS EVENING AND
OVERNIGHT AND AGAIN LATE SUNDAY AFTERNOON AND EVENING.
CHANCES TOO LOW FOR A MENTION IN THE TAFS AT THIS TIME.
EARLIER EXPANSIVE STRATUS CONTINUES TO STEADILY ERODE ACROSS THE
REGION. WHILE SOME SPOTTY MVFR CIGS WILL LIKELY REMAIN IN THE
AREA, THE TREND IN GUIDANCE AND OBSERVATIONS HAS BEEN STRONGLY
TOWARDS VFR CONDITIONS TONIGHT, AND HAVE MOVED THE TAFS IN THAT
DIRECTION THROUGH SUNDAY. WILL ADDRESS ANY SPOTTY MVFR CIGS THAT
MAY RE-DEVELOP TACTICALLY WITH TEMPO GROUPS AS NEEDED. SURFACE
WINDS WILL VEER SOUTHERLY AND EVENTUALLY SOUTHWESTERLY LATE THIS
EVENING.
AN INITIAL BATCH OF SHOWERS ACROSS CENTRAL IOWA WILL CONTINUE
PRESSING NORTHEAST TONIGHT. AS THE ASSOCIATED DISTURBANCE PIVOTS
OVERHEAD, A FEW SPRINKLES/SHOWERS CAN'T BE RULED OUT, BUT
CHANCES REMAIN TOO LOW TO WARRANT INCLUSION IN THE TAFS. HAVE
NOTED A FEW LIGHTNING STRIKES ACROSS CENTRAL IOWA, AND WILL ALSO
CONTINUE TO MONITOR THIS ACTIVITY AS IT TRACKS TOWARDS RFD.
FOR SUNDAY, BREEZY SW WINDS WILL PREVAIL WITH WHAT LOOKS TO BE
LARGELY VFR CONDITIONS. AN ADDITIONAL WINDOW FOR SHOWERS IS
EVIDENT LATE IN THE AFTERNOON INTO THE EVENING. IF TRENDS
CONTINUE, CONSIDERATION FOR PROB30S AND/OR TEMPO GROUPS FOR
SHOWERS WILL BE GIVEN IN FUTURE TAF ISSUANCES.
CARLAW
LOT WATCHES/WARNINGS/ADVISORIES
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY UNTIL 3 AM CST SUNDAY FOR WINTHROP HARBOR
TO NORTHERLY IS. IL.
VISIT US AT WEATHER.GOV/CHICAGO
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