257
FXUS63 KLOT 242332
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
632 PM CDT THU SEP 24 2020
SHORT TERM
155 PM CDT
THROUGH FRIDAY NIGHT...
AN UPPER LEVEL TROUGH ACROSS NE IA INTO SOUTHERN WI WILL CONTINUE TO
DAMPEN AS IT MOVES ACROSS NORTHERN IL AND NORTHWEST IN THIS EVENING
AND OVERNIGHT. A NARROW BAND OF SPRINKLES/BRIEF SHOWERS EXTENDS
SOUTH FROM WI INTO IL AND COULD GRAZE AREAS ALONG AND WEST OF
I-39. OTHERWISE, WITH THIS FEATURE WEAKENING EXPECT MAINLY AN
INCREASE IN CLOUDS.
OUR MILD WEATHER WILL CONTINUE INTO FRIDAY WITH BREEZY SOUTH-
SOUTHWESTERLY WINDS AND MOSTLY CLEAR SKIES (WITH THE EXCEPTION OF
THE PERSISTING ELEVATED WILDFIRE SMOKE) EXPECTED. HIGH
TEMPERATURES WILL BE SLIGHTLY WARMER THAN THURSDAY'S HIGHS THANKS
TO LOW LEVEL WARM ADVECTION IN SOUTHWESTERLY WINDS UNDER THE
STRENGTHENING UPPER RIDGE. WITH READINGS IN THE MID TO UPPER 70S
TODAY, EXPECT HIGHS AROUND 80 OR SO IN MOST LOCATIONS. THE UPPER
JET WILL REMAIN FOCUSED TO OUR NORTH FRIDAY NIGHT KEEPING MILD
CONDITIONS IN PLACE THROUGH THE NIGHT AND SETTING THE STAGE FOR A
WARM SATURDAY.
KMD
LONG TERM
241 PM CDT
SATURDAY THROUGH THURSDAY...
THE PERIOD STARTS WITH A SUMMER-LIKE, BUT BREEZY, FEEL ON
SATURDAY, BUT A ROBUST PATTERN CHANGE IS EXPECTED INTO NEXT WEEK,
AND THIS WILL CERTAINLY MAKE FOR MORE OCTOBER-LIKE WEATHER ACROSS
THE AREA.
ON SATURDAY AN UPPER LEVEL IMPULSE IS EXPECTED TO SHIFT EASTWARD
ACROSS THE DAKOTAS AS THE EXIT REGION OF AN UPPER LEVEL JET NOSES
INTO THE UPPER MIDWEST. THE LOWER-LEVEL MASS RESPONSE TO THIS WILL
RESULT IN STRENGTHENING SOUTH-SOUTHWESTERLY FLOW ACROSS THE
MIDWEST AND INTO THE GREAT LAKES DURING THE DAY. THIS WILL IN
RETURN SET UP SOME STRONG WARM AIR ADVECTION ACROSS THE AREA, WITH
A THERMAL RIDGE FEATURING 850 (925) MB TEMPERATURES IN THE LOW
(MID) 20S CELCIUS SHIFTING OVERHEAD SATURDAY AFTERNOON. THIS AIR
MASS SHOULD BE WARM ENOUGH TO SUPPORT MID TO POSSIBLY EVEN SOME
UPPER 80 DEGREE HIGH TEMPERATURES SATURDAY AFTERNOON. SURFACE
WINDS ALSO LOOK TO BE GUSTY UP TO AROUND 35 MPH OUT OF THE
SOUTHWEST.
A SURFACE COLD FRONT IS EXPECTED TO SHIFT INTO NORTHERN IL ON
SUNDAY MORNING, BEFORE SETTLING OVER CENTRAL IL AND IN IN THE
AFTERNOON. TEMPERATURES IN THE WAKE OF THE FRONT WILL BE COOLER,
ESPECIALLY OVER FAR NORTHERN IL WHERE READINGS WILL LIKELY BE IN
THE LOWER TO MIDDLE 70S. AT THIS TIME THE FRONT LOOKS TO MOVE
THROUGH PRECIPITATION FREE DURING THE MORNING SUNDAY. HOWEVER, IT
APPEARS OUR CHANCES FOR SOME RAIN SHOWERS WILL INCREASE A BIT
LATER SUNDAY INTO SUNDAY EVENING AS A ROBUST UPPER TROUGH DIGS
OVER THE AREA AND INTERACTS WITH THE LOWER-LEVEL BAROCLINIC ZONE
OVERHEAD. THESE SHOWERS MAY CONTINUE INTO MONDAY AS WELL AS
ANOTHER SURFACE LOW TRIES TO DEVELOP JUST TO OUR SOUTHEAST IN THE
VICINITY OF THE SURFACE BOUNDARY. CONFIDENCE IS A BIT LOW,
HOWEVER, WITH THE EXTENT OF RAIN SHOWERS OVER OUR AREA ON MONDAY,
AS THERE ARE SOME QUESTIONS AS TO HOW THIS POTENTIAL SURFACE LOW
MAY EVOLVE. ONE THING THAT IS OF HIGHER CONFIDENCE IS THE MUCH
COOLER CONDITIONS ON MONDAY, WITH HIGHS IN THE 60S AREAWIDE.
FOLLOWING MONDAY IT APPEARS THAT THE AREA COULD BE IN FOR A PERIOD
OF EVEN COOLER WEATHER FOR THE MIDDLE TO END OF THE WEEK. THIS AS
THE LARGE SCALE UPPER-LEVEL PATTERN BECOMES AMPLIFIED ACROSS
NORTH AMERICA. THIS PATTERN LOOKS TO FEATURE A MEAN TROUGH OVER
MUCH OF THE UPPER MIDWEST AND GREAT LAKES REGIONS AND A DOMINATE
UPPER RIDGE OVER WESTERN NORTH AMERICA. IN ADDITION TO THE MUCH
BELOW NORMAL TEMPERATURES NEXT WEEK, WE COULD ALSO EXPERIENCE SOME
PERIODS OF SHOWERS ASSOCIATED WITH SMALLER SCALE DISTURBANCES
SHIFTING OVERHEAD IN THE CYCLONIC FLOW ALOFT. THE DETAILS OF THESE
DISTURBANCES AND ANY ASSOCIATED RAIN ARE UNCLEAR AT THIS TIME.
FOR THIS REASON, I DID NOT STRAY FROM THE NATIONAL BLEND GUIDANCE,
WHICH GIVES LOWER CHANCE POPS THROUGH MUCH OF THE PERIOD.
KJB
AVIATION
FOR THE 00Z TAFS...
VFR CONDITIONS ARE EXPECTED THROUGH THE TAF PERIOD. MID TO HIGH
LEVEL CLOUDS WILL LINGER THROUGH THE EVENING HOURS BEFORE
GRADUALLY CLEARING OUT OVERNIGHT. SOUTH TO SOUTHWESTERLY WINDS
WILL CONTINUE OVERNIGHT AND THROUGH THE DAY TOMORROW, WITH
OCCASIONAL GUSTS TO 18 TO 20 KT POSSIBLE BY LATE MORNING.
PETR
LOT WATCHES/WARNINGS/ADVISORIES
IL...NONE.
IN...NONE.
LM...NONE.
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