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 08Z...
* GUSTY WINDS THROUGH THURSDAY EVENING.
* MVFR CIGS THROUGH THURSDAY EVENING...AND ANY POTENTIAL FOR IFR.
* PRECIP END TIME. BMD
//DISCUSSION...UPDATED 06Z...
LOW PRESSURE OVER NORTHERN OHIO WILL MAINTAIN ITS STRENGTH THROUGH
THE OVERNIGHT PERIOD BEFORE BEGINNING TO LIFT NORTHEAST AWAY FROM
THE REGION LATE THURSDAY MORNING. WITH PRESSURE FALLS OVER THE AREA
TERMINALS PEAKING...WINDS SHOULD GRADUALLY TREND DOWN THROUGH THE
FORECAST PERIOD. OUT THE GATE HOWEVER...STILL EXPECT WINDS GUSTING
TO AROUND 30 KTS...AND UP TO 35 KTS AT TIMES OVERNIGHT AND BY
THURSDAY AFTERNOON...STILL EXPECT WINDS WELL INTO THE 20 KT RANGE.
FARTHER WEST AT KRFD...WINDS WILL BE SLIGHTLY WEAKER. CIGS HAVE NOT
BEEN AS LOW AS ORIGINALLY FORECAST...PARTLY DUE TO WINDS KEEPING
THINGS SOMEWHAT MIXED...BUT STILL EXPECT A GRADUAL DOWNWARD TREND
OVERNIGHT. CONDITIONS SHOULD STAY ABOVE IFR FOR THE MOST PART...BUT
CONFIDENCE IS NOT HIGH...AND MET GUIDANCE...WHICH AS HAS BEEN TOO
LOW ANYHOW...SUGGESTS IFR MAY STILL BE POSSIBLE. WILL HOLD OFF ON
THAT FOR NOW...BUT WILL MONITOR TRENDS CLOSELY. AS THE LOW LIFTS
NORTHEAST LATER THURSDAY NIGHT...CYCLONIC FLOW WILL EVENTUALLY EXIT
THE AREA BRINGING AN END OF LOW CIGS ACROSS THE AREA. BMD
//ORD AND MDW CONFIDENCE...UPDATED 08Z...
* MEDIUM CONFIDENCE IN WIND SPEED...HIGH CONFIDENCE IN DIRECTION.
* MEDIUM CONFIDENCE IN CIGS DROPPING OVERNIGHT...BUT STAYING MVFR.
LOW CONFIDENCE IN IFR.
* LOW TO MEDIUM CONFIDENCE IN PRECIP END TIME. BMD
//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...
258 AM CDT
STRONG LOW PRESSURE NOW CENTERED NEAR TOLEDO IS NOT EXPECTED TO
MOVE MUCH FURTHER WEST AS IT BEGINS TO WEAKEN AND ELONGATE
NORTHEAST INTO SOUTHWEST QUEBEC BY THIS EVENING. BUT THE GRADIENT
DID TIGHTEN ENOUGH FOR STORM FORCE GUSTS ACROSS MUCH OF SOUTHERN
LAKE MICHIGAN. EVEN THOUGH THE LOW WILL BE WEAKENING...SLOWLY...
THE GRADIENT WILL STILL REMAIN QUITE STRONG THIS MORNING. THUS
WILL LET THE STORM WARNING CONTINUE. WINDS SLOWLY DIMINISH THROUGH
GALE FORCE THIS AFTERNOON INTO TONIGHT...SO ONCE THE STORM FORCE
WINDS ARE DONE...A GALE WARNING WILL BE NEEDED. WINDS SHOULD RELAX
BELOW GALE FORCE BY LATE THIS EVENING OR EARLY FRIDAY MORNING...
AND THEN CONTINUE TO STEADILY WEAKEN AS A RIDGE OF HIGH PRESSURE
MOVES ACROSS THE WESTERN LAKES FRIDAY AFTERNOON/EVENING. ANOTHER
AREA OF LOW PRESSURE IS EXPECTED TO MOVE ACROSS SOUTHERN CANADA
SATURDAY NIGHT INTO SUNDAY WHICH MAY INCREASE SOUTHWESTERLY FLOW
DURING THAT TIME. CMS
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...HIGH WIND WARNING...ILZ006-ILZ014 UNTIL 10 AM THURSDAY.
LAKESHORE FLOOD WARNING...ILZ006-ILZ014 UNTIL 4 PM THURSDAY.
FROST ADVISORY...ILZ003-ILZ004-ILZ005-ILZ008-ILZ010-ILZ011-
ILZ012-ILZ019-ILZ020-ILZ021-ILZ032...1 AM FRIDAY TO 9 AM
FRIDAY.
IN...HIGH WIND WARNING...INZ001-INZ002 UNTIL 10 AM THURSDAY.
LAKESHORE FLOOD WARNING...INZ001-INZ002 UNTIL 9 PM 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.
&&
$$
