524
FXUS63 KLOT 211134
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
634 AM CDT SUN OCT 21 2018
SHORT TERM
212 AM CDT
TODAY AND TONIGHT...
QUIET WEATHER RETURNS TO THE REGION TODAY, IN THE WAKE OF
SATURDAY'S GUSTY COLD FRONT. TEMPERATURES WILL REMAIN BELOW
NORMAL, DESPITE PLENTIFUL SUNSHINE.
SURFACE HIGH PRESSURE CENTERED OVER THE MID-MISSISSIPPI VALLEY
EARLY THIS MORNING WILL SPREAD SOUTHEAST ACROSS THE OHIO AND
TENNESSEE RIVER VALLEYS BY EVENING. LIGHT WINDS WILL BACK
SOUTHWEST AS THE RIDGE MOVES AWAY FROM THE REGION, WITH A MODEST
INCREASE IN SPEEDS AS THE GRADIENT TIGHTENS. IT WILL BECOME MORE
BREEZY DURING THE AFTERNOON, ESPECIALLY ACROSS THE NORTHWEST HALF
OF THE CWA, AS GUSTS DEVELOP AND INCREASE TO AROUND 20 MPH BEFORE
DIMINISHING WITH SUNSET. OTHER THAN A LITTLE CIRRUS CLIPPING THE
AREA IN ASSOCIATION WITH AN UPPER LEVEL JET STREAK TO OUR NORTH,
SKIES WILL BE SUNNY TODAY. THIS, COMBINED WITH A DEEPENING OF THE
MIXED LAYER, SHOULD SUPPORT TEMPS REBOUNDING TO NEAR THE 50 DEGREE
MARK IN MANY AREAS, THOUGH THE DEEPEST MIXING LOOKS TO COME LATE
IN THE DAY.
AN AREA OF LOW PRESSURE WILL TRACK FROM THE CANADIAN PRAIRIES TO
NORTH OF THE GREAT LAKES TONIGHT AND MONDAY, AND WILL TRAIL A COLD
FRONT ACROSS THE UPPER MIDWEST OVERNIGHT. SURFACE WINDS WILL
REMAIN SOUTHWESTERLY IN ADVANCE OF THE FRONT TONIGHT, HELPING TO
KEEP TEMPS UP IN THE LOW-MID 30S TONIGHT.
RATZER
LONG TERM
212 AM CDT
MONDAY THROUGH SATURDAY...
DRY WEATHER WILL PERSIST THROUGH MID-WEEK, WHILE TEMPERATURES
CONTINUE TO AVERAGE COOLER THAN NORMAL THROUGH MOST OF THE PERIOD.
PRECIPITATION LOOKS TO BE NON-EXISTENT UNTIL FRIDAY/SATURDAY.
FAIRLY STRONG SHORT WAVE AND ITS ASSOCIATED SURFACE LOW PROPAGATE
THROUGH NORTHWEST FLOW ACROSS ONTARIO AND THE GREAT LAKES REGION
MONDAY, TRAILING A COLD FRONT ACROSS THE FORECAST AREA DURING THE
DAY. DRY LOW AND MID LEVELS AS INDICATED BY NAM/GFS SOUNDINGS
INDICATE A DRY COLD FROPA, AND ONLY A PERIOD OF PATCHY HIGH CLOUDS
ARE EXPECTED. SOUTHWEST WINDS AHEAD OF THE FRONT IN THE WARM
SECTOR WILL SUPPORT A MODEST WARM-UP, DEPICTED BY PROGGED 925 MB
TEMPERATURES OF +7/+8 C SUPPORTIVE OF UPPER 50S/LOWER 60S SURFACE
TEMPS. COLD FRONT SETTLES ACROSS THE SOUTH/SOUTHEAST COUNTIES OF
THE FORECAST AREA MONDAY EVENING.
SURFACE HIGH PRESSURE EXPANDS SOUTHEASTWARD FROM CENTRAL CANADA
AND THE NORTHERN PLAINS ON TUESDAY, AS THE LARGER SCALE UPPER
TROUGH OVER THE EASTERN CONUS SHIFTS EASTWARD. UPPER RIDGING
DEVELOPS ALOFT, ALLOWING THE SURFACE HIGH TO LINGER ACROSS THE
AREA THROUGH THE MID-WEEK PERIOD, BEFORE EVENTUALLY DRIFTING OFF
TO THE EAST BY THURSDAY. DRY AND COOLER THAN AVERAGE WEATHER, BUT
WITH GENERALLY CLEAR SKIES, WILL BE THE RULE TUESDAY AND
WEDNESDAY.
EVENTUALLY, THE CUT-OFF LOW CURRENTLY ALONG THE SOUTHERN
CALIFORNIA COAST IS PROGGED TO LIFT SLOWLY OUT ACROSS THE PLAINS
AND INTO THE MIDWEST TOWARD THE REGION LATE IN THE WEEK. MODEL
PRECIP OUTPUT IS HIT AND MISS INITIALLY AS THE APPROACHING WAVE
WORKS AGAINST DEEP DRY AIR MASS ACROSS THE MIDWEST, WITH THE GULF
BLOCKED BY SPRAWLING SURFACE HIGH PRESSURE. LIGHT RAIN POTENTIAL
DOES LOOK TO EVENTUALLY INCREASE BY THE END OF THE PERIOD HOWEVER,
AS THE HIGH MOVES OFF TO THE EAST AND SOME DEGREE OF LOW LEVEL
MOISTURE RETURN DEVELOPS INTO THE LOWER-MIDDLE MISSISSIPPI VALLEY.
RATZER
AVIATION
FOR THE 12Z TAFS...
634 AM...ONLY FORECAST CONCERN THIS PERIOD REMAINS THE WINDS.
LIGHT WESTERLY WINDS WILL TURN SOUTHWESTERLY THIS MORNING AND
INCREASE IN SPEEDS TO 10-15KTS BY EARLY AFTERNOON. SOME GUSTS TO
20KTS WILL BE POSSIBLE THIS AFTERNOON INTO SUNSET. THERE REMAINS
UNCERTAINTY REGARDING HOW STRONG THE LOW LEVEL WINDS WILL BECOME
THIS EVENING AND WHETHER LOW LEVEL WIND SHEAR WILL MATERIALIZE BUT
MAINTAINED MENTION WITH THIS FORECAST. THESE LOW LEVEL WINDS DO
APPEAR TO DIMINISH TOWARD SUNRISE MONDAY MORNING. CMS
LOT WATCHES/WARNINGS/ADVISORIES
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...WINTHROP HARBOR TO GARY IN UNTIL 10 AM
SUNDAY.
SMALL CRAFT ADVISORY...GARY TO MICHIGAN CITY IN UNTIL 1 PM SUNDAY.
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