806 PM CDT
CLASSIC AUTUMN LOW PRESSURE SYSTEM CONTINUES TO IMPACT MUCH OF THE
GREAT LAKES REGION. FORECAST MODELS INITIALLY OVERCORRECTED WITH
THE SURFACE LOW RETROGRADING WEST NEAR FORT WAYNE IN. THE LATEST
GUIDANCE HAS CORRECTED EAST WITH THE SURFACE LOW SLIDING WEST
TOWARDS TOLEDO AND THEN LIFTING NORTH THURSDAY. IN TERMS OF
ANOMALY DATA...THE PAST SEVERAL CYCLES HAVE WEAKENED THE STRENGTH
OF THE 850MB U-WIND ANOMS FROM EARLIER FORECAST OF -5 SIGMA TO -3
SIGMA IN OUR CWFA. ISALLOBARIC PRES CHG CONTINUES TO BE FORECAST
OF AROUND 3 TO 4 MB/3HR CHANGE THROUGH THE OVERNIGHT PERIOD. BASED
ON THIS GUIDANCE...AND CURRENT OBSERVATIONS OF OCCASIONAL WIND
GUSTS ALONG THE IMMEDIATE LAKESHORE HAVE BEEN STEADILY COMING UP
INTO WARNING CRITERIA. EXPECT THIS WILL ONLY PERSIST THROUGH THE
OVERNIGHT PERIOD.
BASED ON THE AFOREMENTIONED CONDITIONS...AND EXPECTED FORECAST
THROUGH THE OVERNIGHT PERIOD NOT GOING TO MAKE CHANGES TO CURRENT
HEADLINES. WHILE THERE MAY BE PERIODS OF TIME WITH SUB WARNING
CRITERIA.
MADE SOME ADJUSTMENTS TO THE QPF FORECAST. OPTED TO BLEND IN THE
LATEST SREF QPF FORECAST FROM 00-06Z...WHICH RESULTED IN DROPPING
TOTALS IN THIS PERIOD DOWN TO ARND 0.3 TO 0.7 FROM WEST TO EAST
ACROSS THE CWFA.
BEACHLER
&&
.PREV DISCUSSION...
247 PM CDT
SHORT TERM...TONIGHT THROUGH SATURDAY
MAIN CONCERNS DURING THE SHORT TERM PERIOD CONTINUE TO CENTER
AROUND THE POTENT AUTUMN STORM SYSTEM CURRENTLY IMPACTING THE
REGION.
THE SURFACE LOW ACROSS WEST VIRGINA IS BEGINNING TO UNDERGO RAPID
INTENSIFICATION AS IT LIFTS NORTH NORTHWESTWARD INTO SOUTH OHIO.
WATER VAPOR IMAGERY THIS AFTERNOON SHOWS AN UPPER LEVEL JET
PUNCHING NORTHWARD ACROSS THE SOUTHEASTERN CONUS DOWN STREAM OF
THE THE UPPER LOW/TROUGH. LARGE SCALE ASCENT WITHIN THE LEFT EXIT
REGION OF THIS JET SHOULD LEAD TO RAPID DEEPENING OF THE SURFACE
LOW INTO THIS EVENING. WITH THE STRENGTHENING LOW...NORTHERLY
WINDS ARE STILL EXPECTED TO INCREASE TO ADVISORY CRITERIA LATER
THIS AFTERNOON AND EVENING...AND WARNING CRITERIA WINDS AT THE
LAKE FRONT. THEREFORE...I WILL KEEP THE CURRENT HEADLINES IN
PLACE.
THE OTHER CONCERN TONIGHT WILL BE WITH MODERATE TO HEAVY RAINFALL
POTENTIAL...ESPECIALLY ACROSS NORTHWESTERN INDIANA AND SOME OF MY
ADJACENT ILLINOIS COUNTIES. THE MODELS HAVE BEEN CONSISTENT IN
PRODUCING A RATHER IMPRESSIVE TROWAL EXTENDING ACROSS THESE
AREAS. THIS LOOKS TO DO TWO THINGS: FIRST IT SHOULD ENHANCE THE
LOWER LEVEL MESOSCALE FORCING AS A BAND OF MID LEVEL FRONTOGENESIS
DEVELOPS IN ASSOCIATION WITH THE TROWAL. THIS WILL HELP PRODUCE
BANDS OF MODERATE TO HEAVIER PRECIPITATION. SECONDLY...THE WARMER
MID LEVEL TEMPERATURES...TRANSPORTING WESTWARD WITHIN THE TROWAL
AIRSTREAM...WILL INCREASE THE WARM CLOUD DEPTH AND ALLOW HIGHER
PRECIPITABLE WATER AROUND AN INCH TO MOVE ACROSS THE AREA. ALL IN
ALL THIS LOOKS TO SET THE STAGE FOR A GOOD RAINFALL EVENT TONIGHT
ACROSS MY NORTHWEST INDIANA COUNTIES WESTWARD ACROSS PORTIONS OF
THE CHICAGO AREA. OVERALL...I WOULD EXPECT BETWEEN 1 TO AS MUCH AS
2 INCHES ACROSS THESE AREAS. HOWEVER FARTHER WEST AND
NORTH...AMOUNTS WILL BE MUCH LIGHTER...WITH ONLY A QUARTER TO A
HALF INCH POSSIBLE ACROSS NORTH CENTRAL ILLINOIS. THE WIND AND
RAIN WILL CONTINUE ON THURSDAY...BUT WILL ABATE DURING THE
AFTERNOON AS THE STORM SYSTEM LIFTS NORTHEAST ACROSS THE EASTERN
GREAT LAKES.
A SURFACE RIDGE OF HIGH PRESSURE WILL BUILD IN BEHIND THIS LOW ON
THURSDAY NIGHT AND FRIDAY. THIS COULD ALLOW FOR TEMPERATURES TO DROP
NEAR 30 ACROSS PORTIONS OF NORTH CENTRAL ILLINOIS. I ADDED A MENTION
OF FROST TO THE GRIDS FOR THURSDAY NIGHT AND FRIDAY NIGHT AS THIS
HIGH MOVES ACROSS THE AREA AND PRODUCES SOME COOL MORNING LOW
TEMPERATURES UNDER CLEAR SKIES.
KJB
LONG TERM...SAT NIGHT THROUGH WED
A COUPLE WAVES RIPPLE THROUGH NORTHWEST FLOW SAT NIGHT THROUGH
SUNDAY. THE STRONGEST APPEARS TO BE MOVING THROUGH THE GREAT LAKES
SUNDAY AFTERNOON. WITH LIMITED MOISTURE AND BEST DYNAMICS PASSING
NORTH...WILL JUST MAINTAIN LOW CHANCE POPS FOR SUNDAY INTO SUNDAY
EVENING. UPPER RIDGING...SW SURFACE FLOW...AND SUNSHINE SHOULD BOOST
TEMPS INTO 60S MONDAY...POSSIBLY PUSHING 70 DOWN TOWARDS PONTIAC AND
WATSEKA. MONDAY APPEARS TO BE THE BEST DAY OF THIS 7 DAY PACKAGE.
CLOUDS AND SHOWERS SHOULD OVERSPREAD THE AREA TUESDAY AND TUESDAY
NIGHT AS NEXT WAVE DIGS INTO THE PLAINS. GFS HAS BAROCLINIC ZONE
SETTING UP OVER NORTHERN IL WITH EAST-NORTHEAST SURFACE WINDS OVER
MUCH OF THE AREA. THIS WOULD RESULT IN COOLER TEMPS THAN WHAT
GUIDANCE IS PROJECTING. ECMWF STILL PLACES SURFACE LOW FURTHER NORTH
KEEPING NORTHERN IL IN SOUTHERLY FLOW TUESDAY. WILL HAVE TO KEEP AND
EYE ON THIS AND MAY NEED TO ADJUST TEMPERATURES DEPENDING ON MODEL
TRENDS.
ALLSOPP
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 00Z...
* CIG TRENDS...TO IFR POSSIBLE
* NORTHERLY WINDS WITH GUSTS AOA 35 KT LIKELY
* RAIN BECOMING HEAVIER WITH LOWER VISBYS OVERNIGHT
SHEA
//DISCUSSION...UPDATED 00Z...
CHALLENGING FORECAST CONTINUES WITH THE STRONG FALL SYSTEM THAT IS
UNDERWAY. BIGGEST CHANGES TO THE FORECAST HAVE BEEN TO PULL BACK
THE TIMING ON WHEN WE WILL DROP TO IFR CIGS. SECONDLY...GUIDANCE
HAS TRENDED TOWARDS MORE OF AN EASTERLY LOCATION FOR THE SURFACE
LOW TRACKING THROUGH THE OHIO VALLEY...INSTEAD OF OVER FORT WAYNE.
THE OVERALL GRADIENT IS NOT AS ROBUST AS ORIGINALLY ANTICIPATED
AND NOW ONLY EXPECT PEAK GUST TO BE AROUND 35 KT...THOUGH THERE
MAY BE A FEW HIGHER GUSTS...WOULD EXPECT THE MAJORITY TO REMAIN
IN THE 35 KT BALLPARK. THE HEAVIEST OF RAIN HAS ALSO BEEN SLOW
MOVING INTO THE REGION AND AGAIN SHIFTED BACK THE TIMING OF THE
MORE PERSISTENT AND HEAVIER RAINFALL. IT IS ANTICIPATED THAT WITH
THESE MORE STEADY RAINS THAT WILL SEE CONDITIONS FALL THROUGH MVFR
VIS AND POTENTIALLY INTO IFR CIGS. RAIN AND WIND TO CONTINUE
THROUGH THE AFTERNOON BEFORE THE SURFACE LOW PULLS
NORTHEAST...RELAXING THE GRADIENT OVERNIGHT AND ALLOWING DRY AIR
TO FILTER IN BY THURSDAY.
SHEA
//ORD AND MDW CONFIDENCE...UPDATED 00Z...
* MEDIUM CONFIDENCE ON CIGS LOWERING
** LOW ON TIMING
* HIGH CONFIDENCE ON WIND DIRECTIONS
** MEDIUM TO HIGH WITH 35 KT GUSTS THIS EVENING...AND A FEW
OCCNLY HIGHER
* MEDIUM CONFIDENCE IN VIS TRENDS...HIGH IN DEGRADATION IN +RA
* MEDIUM CONFIDENCE ON PRECIP TRENDS
SHEA
//OUTLOOK FOR ORD/MDW FOR 12Z FRIDAY-12Z WEDNESDAY...UPDATED 00Z...
* FRIDAY AND SATURDAY...VFR
* SUNDAY...SLIGHT CHANCE OF SHRA
* MONDAY...VFR
* TUESDAY...CHANCE OF SHRA
SHEA
&&
.MARINE...
300 PM CDT
STORM FORCE WINDS TO DEVELOP LATE THIS AFTERNOON AND EVENING...
LOW PRESSURE CENTERED OVER WESTERN WEST VIRGINA THIS AFTERNOON WILL
BEGIN TO MORE RAPIDLY INTENSIFY INTO THE EVENING AS IT MOVES TOWARD
WESTERN LAKE ERIE. SO FAR THE LOW HAS BEEN SLOW TO MOVE WHICH HAS
RESULTED IN A SLOWER EXPANSION OF STRONGER WINDS ACROSS CENTRAL AND
NORTHERN LAKE MICHIGAN SO FAR TODAY. SOUTHERN SECTIONS CONTINUE TO
SEE GALES WHICH BEGAN EARLIER THIS MORNING AND WILL LIKELY SEE AN
INCREASE TO STORM FORCE LATE THIS AFTERNOON AS THE LOW BEGINS TO
SPEED UP AND STRENGTHEN. SPEEDS NOW REACHING GALE FORCE ACROSS THE
NORTH AFTER A SLOW INCREASE THROUGH EARLY AFTERNOON. WITH THE LOW
STARTING TO STRENGTHEN AND SPEED ITS NORTHWARD PROGRESS EXPECT THAT
WINDS WILL RAPIDLY INCREASE THROUGH THE REST OF THE AFTERNOON AND
EARLY EVENING. STORM FORCE GUSTS MAY TAKE UNTIL 00Z OR SO TO
MATERIALIZE BUT WILL KEEP THE STORM WARNING START TIME AS-IS GIVEN
THE POTENTIAL FOR A RAPID INCREASE OVER THE NEXT 3-4 HRS. AM
THINKING THAT PEAK WINDS WILL OCCUR THIS EVENING AND EARLY TONIGHT
WHEN THE PRESSURE GRADIENT IS STRONGEST WITH GUSTS TO 60 KT A
POSSIBILITY SOUTH. DIRECTION WILL BE NORTH TO NORTHEAST WITH A SHIFT
TO THE NORTH THURSDAY MORNING. THE LOW WILL SLOW DOWN AND TRACK
SLIGHTLY WESTWARD INTO NORTHWEST OHIO THURSDAY MORNING. STORM FORCE
WINDS WILL CONTINUE INTO THE MORNING THEN DIMINISH TO GALES INTO THE
AFTERNOON AS THE LOW WEAKENS AND MOVES NORTHEAST INTO SOUTHERN
ONTARIO. HIGH PRESSURE WILL APPROACH THE MISSISSIPPI RIVER VALLEY
THURSDAY NIGHT AND FRIDAY WHICH WILL ALLOW WINDS TO DIMINISH BELOW
GALES SOMETIME THURSDAY EVENING. HIGH PRESSURE WILL CROSS THE LAKE
INTO SATURDAY KEEPING LIGHT WINDS IN PLACE WITH A WEST TO SOUTHWEST
DIRECTION. A WEAK FRONT MAY CROSS THE LAKE LATER SUNDAY BRINGING A
MODEST INCREASE IN SPEEDS WITH A STRONGER SYSTEM POSSIBLE TOWARD THE
MIDDLE OF NEXT WEEK.
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...HIGH WIND WARNING...ILZ006-ILZ014 UNTIL 10 AM THURSDAY.
LAKESHORE FLOOD WARNING...ILZ006-ILZ014 UNTIL 4 PM THURSDAY.
WIND ADVISORY...ILZ005-ILZ012-ILZ013-ILZ020-ILZ021-ILZ022-ILZ023-
ILZ032-ILZ033-ILZ039 UNTIL 10 AM THURSDAY.
IN...HIGH WIND WARNING...INZ001-INZ002 UNTIL 10 AM THURSDAY.
LAKESHORE FLOOD WARNING...INZ001-INZ002 UNTIL 9 PM THURSDAY.
WIND ADVISORY...INZ010-INZ011-INZ019 UNTIL 10 AM THURSDAY.
LM...STORM WARNING...LMZ080-LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-
LMZ567-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-LMZ742-
LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ868-LMZ870-LMZ872-
LMZ874-LMZ876-LMZ878 UNTIL 3 PM THURSDAY.
&&
$$
