033
FXUS63 KLOT 181127
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
627 AM CDT WED SEP 18 2019
SHORT TERM
203 AM CDT
THROUGH THURSDAY...
DRIER AIR JUST OFF THE SURFACE HAS LIMITED MUCH OTHER THAN SOME
PATCHY FOG EARLY THIS MORNING, AND WE'VE NOTED EVEN AHEAD OF THE
CIRRUS SOME DEWPOINT LOWERING WITH THE LIMITED TEMPERATURE FALLS.
NIGHTIME MICROPHYSICS SATELLITE IS PICKING UP A SLIGHTLY MORE
FOCUSED AREA OF FOG IN WI THAT EXTENDS INTO MCHENRY COUNTY,IL, SO
SOME BRIEF EXPANSION IS POSSIBLE.
THE UPPER RIDGE IS STILL IN PLACE OVERHEAD AS A STRONGER UPPER LOW
SPINS ACROSS THE NORTHERN PLAINS. SEVERAL WAVES ARE NOTED IN THE
SOUTHWEST FLOW, THE ONES CLOSER TO OUR REGION ONLY RESULTING IN
SOME CIRRUS, WITH A STRONGER WAVE AND MOISTURE TRANSPORT AXIS
DRIVING WHAT SHOULD BE INCREASED THUNDERSTORM ACTIVITY ACROSS THE
UPPER MIDWEST. EXPECT SOME WEAKENING OF THIS OVERNIGHT ACTIVITY
BEFORE STORMS ACROSS THIS CORRIDOR REFORM AHEAD OF AN ADVANCING
COLD FRONT. LOCALLY THIS WILL SLOWLY PUSH THE SURFACE HIGH
RESPONSIBLE FOR OUR PLEASANT WEATHER THE LAST FEW DAYS TO
EASTWARD. BUT FOR TODAY, EXPECT OCCASIONAL PASSING CIRRUS,
ESPECIALLY THIS MORNING. WE WILL STILL FEEL THE INFLUENCE OF THE
HIGH WITH DRY SOUTHEAST WINDS. INCREASING 925 MB TEMPS SHOULD
SUPPORT EVEN FURTHER WARMING TODAY, WITH 80S AGAIN COMMON INLAND,
AND MID 70S AT THE LAKE. COULD EVEN HAVE A LITTLE LAKE BREEZE.
THE MAIN MOISTURE AXIS WILL PUSH CLOSE TO THE MISSISSIPI VALLEY
OVERNIGHT. MODEL GUIDANCE FOR DAYS HAS SUGGESTED THE DEVELOPMENT
OF ANOTHER COMPLEX OF THUNDERSTORMS AS THE LOW LEVEL JET INCREASES
OVERNIGHT. DRY AIR AND SOME LINGERING SURFACE HIGH INFLUENCE
SHOULD LARGELY KEEP THIS ACTIVITY OFF TO OUR WEST TONIGHT. IN
SPITE OF THE INITIAL HIGHER CLOUD COVER, THURSDAY SHOULD BE
EQUALLY WARM IF NOT WARMER, AND COULD PUSH 80 EVEN AT THE LAKE
BEFORE ANY LAKE BREEZE INFLUENCE DEVELOPS. LOW TO MID 80S WILL
RULE INLAND AREAS, WARMEST SOUTHERN LOCALES.
KMD
LONG TERM
314 AM CDT
THURSDAY NIGHT THROUGH TUESDAY...
THURSDAY NIGHT AND FRIDAY: A RATHER PRONOUNCED MID-LEVEL RIDGE WILL
REMAIN ENTRENCHED ACROSS THE GREAT LAKES REGION DURING THIS PERIOD,
WITH CONTINUED UNSEASONABLY WARM CONDITIONS INTO FRIDAY, WHEN TEMPS
IN THE MID TO POTENTIALLY UPPER 80S RUN 10F+ ABOVE NORMAL.
WEAK DISTURBANCES WILL CONTINUE TO ROUND THE WESTERN EXTENT OF THIS
RIDGE OVER A MODERATELY UNSTABLE AIR MASS. CONVECTION OVER IOWA ON
THURSDAY AFTERNOON MAY SNEAK INTO THE NW CWA IN A DECAYING MODE AS
IT OUTRUNS MUCH BETTER INSTABILITY AND INTO A MORE CAPPED
ENVIRONMENT. DEPENDING ON HOW FAR EAST THIS CONVECTION REACHES, A FEW
STORMS MAY DEVELOP ON A RESULTANT OUTFLOW BOUNDARY OVER THE NW CWA
FRIDAY AS CAPPING WEAKENS FROM MINOR COOLING IN THE 925-850 HPA
LAYER. OVERALL, DRY WEATHER FOR MUCH OF THE AREA FOR A SIGNIFICANT
PORTION OF THIS TIME PERIOD CAN BE EXPECTED.
SATURDAY THROUGH SUNDAY: DEEP TROUGHING CURRENTLY OVER THE PACIFIC
NORTHWEST WILL QUICKLY ERODE THE RIDGE ACROSS THE GREAT LAKES THIS
WEEKEND. A COLD FRONT WELL REMOVED FROM ITS PARENT LOW OVER HUDSON
BAY WILL THEN APPROACH THE AREA ON SATURDAY, SLOWLY CROSSING THE CWA
ON SUNDAY. THIS OCCURS AS ABUNDANT MOISTURE ASSOCIATED NOW TROPICAL
DEPRESSION IMELDA IS ADVECTED INTO THE REGION AHEAD OF THE FRONT.
PWAT VALUES OF AROUND 1.8" WILL BE NEAR THE CLIMATOLOGICAL MAX FOR
THE THIRD WEEK OF SEPTEMBER. PUTTING ALL THIS TOGETHER, MULTIPLE
ROUNDS OF HEAVY SHOWERS AND/OR THUNDERSTORMS WILL BE POSSIBLE
SATURDAY NIGHT THROUGH SUNDAY, THOUGH ISOLATED TO SCATTERED ACTIVITY
MAY PRECEDE THE FRONT ON SATURDAY. WILL CONTINUE TO MONITOR THIS
PERIOD FOR A RENEWED FLOODING RISK.
BY EARLY NEXT WEEK, GUIDANCE DIVERGES WITH THE HANDLING OF A WESTERN
CONUS TROUGH, THOUGH IT LOOKS AS IF IT WILL BECOME CUTOFF BEFORE
REACHING THE GREAT PLAINS. MODEST MID-LEVEL RIDGING WOULD THEN BE
THE DOMINATE FEATURE ACROSS THE AREA, PRODUCING GENERALLY QUIET
CONDITIONS.
KLUBER
AVIATION
FOR THE 12Z TAFS...
VFR CONDITIONS WITH PASSING UPPER-LEVEL CLOUDS ARE EXPECTED
THROUGHOUT THE PERIOD. WIND DIRECTION WILL LIKELY SETTLE AROUND 170
THROUGH AT LEAST MID AFTERNOON AT ORD/MDW. HOWEVER, SOME TEMPORARY
VEERING TO 190 OR POSSIBLY 200 AT AROUND 10 KNOTS IS EXPECTED MID
MORNING INTO EARLY AFTERNOON AS STRONGER SSW WINDS AT 1-2 KFT ARE
MIXED DOWN TO THE SURFACE. A LAKE-INDUCED BACKING OF THE WINDS TO
SE/ESE SHOULD THEN OCCUR MID TO LATE AFTERNOON AT ORD/MDW.
KLUBER
LOT WATCHES/WARNINGS/ADVISORIES
IL...NONE.
IN...NONE.
LM...NONE.
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