343 AM CST
EARLY THIS MORNING THE SURFACE LOW WAS BEING ANALYZED TO THE
NORTHEAST OF ST LOUIS AND CONTINUES TO LIFT NORTH/NORTHEAST. IR
IMAGERY SHOWS A NARROW CHANNEL OF DRIER AIR ACROSS THE WESTERN HALF
OF ILLINOIS WITH THE MOISTURE CONVEYOR BEGINNING TO PIVOT EAST
ACROSS EAST CENTRAL ILLINOIS AND INDIANA. STUBBORN FRONTAL BOUNDARY
REMAINS JUST TO THE SOUTH OF I-80 STRETCHING EAST THROUGH SOUTHERN
LOWER MICHIGAN. COLD FRONT WAS BEGINNING TO PUSH INTO EASTERN IOWA
AND NEARING THE MISSISSIPPI RIVER. UPSTREAM ACROSS IOWA MANY
OBSERVATION SITES HAVE CONTINUED TO REPORT PERIODS OF LIGHT SNOW
THROUGHOUT THE OVERNIGHT PERIOD.
REGIONAL RADAR RETURNS SHOW THE DEFORMATION ZONE STRETCHED FROM
CENTRAL IOWA NORTHEAST THROUGH SOUTHWEST WISCONSIN. TO THE EAST OF
THIS ZONE CONSIDERABLE LGT RAIN SHOWERS WERE FALLING ACROSS WEST
CENTRAL ILLINOIS...AND LIFTING NORTH.
CONSIDERABLE SHEAR REMAINS OVERHEAD WITH A POTENT LLVL JET AT
50-60KTS. DESPITE INCREASED LIMITING FACTORS...HAVE STRUGGLED TO
COMPLETELY REMOVE MENTION OF THUNDER. THE ONLY LOCATION THAT WE HAVE
THUNDER RUNNING IS FOR FAR SOUTHEAST CWFA AREAS AND ONLY UNTIL 15Z.
BY THIS TIME EXPECT THE FRONTAL BOUNDARY TO HAVE PUSHED EAST. DRY
SLOT ARRIVES LATE MORNING WITH WRAP AROUND MOISTURE PIVOTING EAST.
EXPECT A STEADY TAPERING TO ANY REMAINING MOISTURE...HOWEVER NOT
COMPLETELY DRY.
THERMAL TROUGH ALOFT STEADILY BUILDS IN FROM THE NORTHWEST...COUPLED
WITH STRONG COLD AIR ADVECTION AND TEMPS WILL STRUGGLE TO WARM AT
ALL TODAY. EXPECT MANY LOCATIONS TO REMAIN STEADY...PERHAPS RISE A
FEW DEGREES EARLY THIS MORNING. OTHERWISE MANY SITES WILL SEE
TEMPERATURES HOLD STEADY THEN BEGIN TO FALL BY MIDDAY INTO THE UPPER
30S TO LOWER 40S. THE FAR NORTHWEST PORTIONS OF THE CWFA TEMPS MAY
COOL EARLY ENOUGH TO ALLOW PRECIP TO BECOME MIXED OR COMPLETELY
CHANGE OVER FROM RAIN TO SNOW.
OVERNIGHT SKIES WILL REMAIN MOSTLY CLOUDY...POSSIBLY ALLOWING SOME
THINNING TO THE CLOUDS FURTHER WEST. THIS SHOULD LIMIT HOW COOL
TEMPS WILL BECOME. HAVE MAINTAINED OVERNIGHT LOWS IN THE UPPER 20S
TO LOWER 30S. EXPECT BREEZY CONDITIONS TO CONTINUE...CREATING
APPARENT TEMPS IN THE LOW/MID 20S OVERNIGHT.
THURSDAY THROUGH FRIDAY...
500MB TROUGH AXIS OVERHEAD THUR...SLOWLY PIVOTING EAST FRI. SFC VORT
CONTINUES TO LIFT NORTH ACROSS EASTERN ONTARIO/WESTERN QUEBEC WITH
BROAD ANTI-CYCLONIC FLOW ENCOMPASSING MUCH OF THE SOUTHWEST CONUS.
HEIGHTS BEGIN TO RISE OVERHEAD THUR EVE...WHICH SHOULD AID IN
ADDITIONAL EROSION OF CLOUDS AND MOISTURE IN THE NEAR SFC
ENVIRONMENT. THE EXCEPTION WILL BE CLOSER TO LAKE MICHIGAN WHERE
LAKE STRATUS WILL PERSIST. IN ADDITION SOME MARGINAL MOISTURE IS
PROGGED TO SLIDE SOUTH FROM WISC AND PUSH OVER FAR NORTHEAST IL.
850MB THERMAL TROUGH AXIS BUILDS IN FROM THE NORTHWEST THUR AFTN AND
REMAINS THROUGH EARLY FRI...WITH TEMPS BETWEEN -6 AND -9 DEG C. BY
FRI AFTN THE TROUGH AXIS PIVOTS EAST WITH THE MID-LVL TROUGH.
LLVL MOISTURE IS MARGINAL THROUGH MUCH OF THUR...AND WITH AFTN HIGHS
STRUGGLING TO PUSH BEYOND 40 DEG IN MANY LOCATIONS SOME
PRECIPITATION MAY FALL AND WOULD POTENTIALLY FALL AS A MIX OF
RAIN/SNOW. IT IS CONCEIVABLE TO SEE A FEW LOCATIONS REMAIN IN THE
UPPER 30S GIVEN THE OVERNIGHT LOWS FROM THE PREVIOUS NIGHT IN THE
UPPER 20S. IN ADDITION CLOUD COVER WILL PLAY A ROLE IN TEMPS AS A
STRATUS LAYER IS EXPECTED TO LINGER THRU MUCH OF THE DAY BEFORE
EXITING TO THE EAST SOMETIME FRI.
WITH THE SFC RIDGE BUILDING IN FROM THE SOUTHWEST...ENOUGH DIFFLUENT
FLOW IN THE MID-LVLS SHOULD FINALLY BRING AN END TO THE PRECIP
ACROSS THE CWFA. THE EXCEPTION WOULD BE OVER LAKE MICHIGAN WHERE
ENOUGH OF A THERMAL GRADIENT CONTINUES TO SUPPORT LAKE STRATUS AND
PRECIP. TEMPS SHOULD BE COLD ENOUGH THAT THIS WOULD SUPPORT
RAIN/SNOW MIX.
SATURDAY THROUGH TUESDAY...
ENSEMBLES CONTINUE TO DEMONSTRATE MINIMAL SPREAD IN REGARDS TO THE
500MB TROUGH AXIS PIVOTING EAST LATE FRI/SAT...AS A PERIOD OF
SEMI-ZONAL FLOW ALONG THE NORTHERN PERIPHERY OF A LLVL RIDGE BUILDS
IN FROM THE WEST SAT. MEANWHILE UPSTREAM NEAR SOUTHERN
CALIFORNIA...AN ANOMALOUSLY STRONG 500MB TROUGH WILL BEGIN TO PUSH
EAST INTO THE SOUTHERN END OF THE SIERRA NEVADA MOUNTAINS SAT. ALONG
THE LEE-SIDE OF THIS POTENT TROUGH AXIS WAS A SECONDARY TROUGH
SLIDING SOUTHEAST FROM THE CANADIAN ROCKIES. THIS SHOULD AID IN A
SLIGHT AMPLIFICATION TO THE DOWNSTREAM WAVE OR SLIGHT RIDGING ACROSS
THE GREAT LAKES/OHIO VALLEY EARLY NEXT WEEK.
AS THE ANOMALOUSLY STRONG 500MB TROUGH PUSHES EAST ACROSS THE
SOUTHERN ROCKIES. TRADITIONALLY THIS PATTERN SUGGESTS A
STRENGTHENING OF THE LLVL JET FROM SW TO NE ACROSS THE PLAINS STATES
INTO THE WESTERN GREAT LAKES. THUS IT IS CONCEIVABLE TO SEE
INCREASED PRECIP CHANCES EARLY NEXT WEEK...WITH A GROWING POTENTIAL
FOR CONVECTION. A SUPPORTING MEMBER IS THAT CONFIDENCE IN A
STRENGTHENING 500MB RIDGE OVER THE SOUTHEAST CONUS APPEARS TO BE
DEVELOPING OR IS AT LEAST FAVORED AMONGST ENSEMBLE MEMBERS TUE/WED.
THIS COUPLED WITH THE TROUGH CARVED THROUGH THE ROCKIES...SHOULD AID
IN A STRENGTHENING LLVL JET AND DECENT RETURN MOISTURE INTO THE
SOUTHERN PLAINS.
THE CAVEAT TO THIS SCENARIO IS THAT THE 850MB THERMAL TROUGH IS
RATHER FLAT...WITH THE EXCEPTION OF A WEAK RIDGE OVER THE OHIO
VALLEY MON/TUE. TEMPS WILL MAINLY RETURN TO SEASONAL CONDS IN THE
EXTENDED PERIODS...WITH PERHAPS A PERIOD OR TWO OF SLIGHTLY ABOVE
NORMAL CONDS.
BEACHLER
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 16Z...
* MVFR CEILINGS MOVING INTO ORD AND MDW AGAIN BY 17Z.
* GUSTY SOUTHWEST WINDS SHIFTING TO WEST EARLY THIS AFTERNOON.
PAW
//DISCUSSION...UPDATED 12Z...
UPPER TROUGH HAS BECOME NEGATIVELY TILTED AS IT MOVED OVER THO MO
RIVER VALLEY OVERNIGHT. AN UPPER LOW OVER NORTHERN MO IS LIFTING
FROM THE BASE OF THE TROUGH WHILE A WEAK SHORT WAVE IS DROPPING SE
ACROSS THE CENTRAL PLAINS TOWARD THE BASE OF THE UPPER TROUGH.
THE UPPER LOW IS PROGGED TO TRACK ACROSS NW AND N CENTRAL IL THIS
MORNING AND SE WI EARLY THIS AFTERNOON WHILE THE ASSOCIATED
SURFACE LOW...CURRENTLY ABOUT 30SM NW OF PIA...IS PROGGED TO TRACK
ACROSS THE FAR EASTERN PORTION OF THE WI STATE LINE THIS MORNING
BEFORE CONTINUING OUT OVER LAKE MI EARLY THIS AFTERNOON. THIS
TRACK LOOKS REASONABLE AS THAT WOULD BE ALONG AXIS OF SURFACE
PRESSURE FALLS.
THE SURFACE BOUNDARY THAT HAS BEEN SOUTH OF THE TERMINALS FOR A
FEW DAYS IS JUST S OF THE TERMINALS...ALONG A IGQ-C09-C75 LINE...
AND MAKING PROGRESS FURTHER NORTHWARD INTO FAR NE IL. WITH THE
SURFACE LOW TO MOVE NORTHEASTWARD JUST TO THE W AND N OF ORD THIS
WILL BRIEFLY PUT THE TERMINALS IN THE WARM SECTOR OF THE STORM
EARLY THIS MORNING BEFORE THE LOW SWEEPS ITS STRONG COLD FRONT
ACROSS THE AREA LATER THIS MORNING. THIS SHOULD RESULT IN LIFR
CEILINGS TO LIFT TO MVFR. WITH THE WARM LOW LEVEL AND COOLING
UPPER LEVELS AS THE UPPER TROUGH APPROACH THE LOCAL AREA IS
RESULTING IN A POCKET OF INSTABILITY OVER NE IL AND AN OCCASIONAL
ISOLATED LIGHTNING STRIKE OR TWO IS DETECTED.
WITH THE SYSTEM LIFTING NNE THE RAIN IN ITS NE-NW QUADRANTS WILL
CONTINUE TO LIFT INTO WI WHILE SHOWERS OVER CENTRAL IL WILL BE
LIMITED IN DEPTH AS A DRY SLOT IS RAPIDLY CHARGING NNE ACROSS
CENTRAL AND NORTHERN IL.
WITH THE COLD FRONTAL PASSAGE EXPECT WINDS TO VEER TO OUT OF THE
SW AND START INCREASING IN SPEED BUT THINK IT WILL BE A FEW HOURS
BEYOND...AFTER THE UPPER TROUGH AXIS PASSES OVERHEAD...BEFORE
THEY VEER FURTHER TO OUT OF THE W AND GUST TO 35KT AS STRONG COLA
AIR ADVECTION SETS IN AND A STRONG PRESSURE RISE CENTER MOVES
OVER CENTRAL AN NORTHERN IL.
WRAP AROUND MOISTURE WITH SNOW FALLING ACROSS EASTERN IA UNDER THE
DEFORMATION ZONE WILL CLIP NW AND FAR N CENTRAL IL BUT LIFT OFF
INTO WI BEFORE REACHING NE IL.
TRS
//ORD AND MDW CONFIDENCE...UPDATED 16Z...
* HIGH CONFIDENCE IN CEILING AND WIND TREND...MEDIUM CONFIDENCE IN
TIMING.
PAW
//OUTLOOK FOR ORD/MDW FOR 00Z FRIDAY-12Z WEDNESDAY...UPDATED 12Z...
THU NIGHT...
FRI...VFR...WX NIL.
SAT...VFR...WX NIL.
SUN...VFR...SLGT CHANCE -SHRA
MON...CHANCE -SHRA
TUE...VFR...WX NIL.
TRS
&&
.MARINE...
307 AM CST
AN AREA OF LOW PRESSURE OVER MISSOURI THIS MORNING IS EXPECTED TO
DEEPEN IN RESPONSE TO A POTENT UPPER LEVEL SYSTEM AND WILL QUICKLY
MOVE NORTHEAST...REACHING NORTHERN LAKE MICHIGAN BY THIS EVENING.
STRONG PRESSURE FALLS AHEAD...AND PRESSURE RISES BEHIND THE
LOW...IN ADDITION TO AN INCREASINGLY TIGHT PRESSURE GRADIENT WILL
LEAD TO GALE FORCE WINDS ACROSS LAKE MICHIGAN.
THIS MORNING...A NARROW BAND OF LIGHT WINDS ASSOCIATED WITH A WARM
FRONT AHEAD OF THE LOW WILL SLOWLY MOVE NORTH ACROSS THE LAKE.
NORTHEASTERLY WINDS WILL INCREASE TO GALE FORCE THIS MORNING TO THE
NORTH OF THE FRONT...WHILE SOUTHERLY WINDS RAMP UP TO THE SOUTH OF
THE FRONT. WITHIN THE FRONTAL BAND...WINDS WILL BE LIGHTER AND MORE
VARIABLE. AS THE LOW BEGINS TO MOVE EAST OF THE LAKE LATER THIS
AFTERNOON...A TRAILING COLD FRONT AND COLD ADVECTION BEHIND THE LOW
WILL FURTHER ALLOW WINDS TO INCREASE...WITH WINDS EXPECTED TO TOP
OUT AROUND 40 KT OUT OF THE WEST TO NORTHWEST ACROSS THE ENTIRE
LAKE. AS THE TEMPERATURES ALOFT CONTINUE TO COOL...EXPECT TO SEE
PRECIPITATION CHANGE OVER TO SNOW LATER THIS EVENING. WINDS WILL
DROP BELOW GALE FORCE EARLY ON THURSDAY...BUT EXPECT BRISK WESTERLY
FLOW TO CONTINUE THROUGH THE REMAINDER OF THE WEEK AND INTO THE
WEEKEND AS AN ACTIVE PATTERN BRINGS A PAIR ACROSS THE NORTHERN
PLAINS AND CANADA. BMD
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ777-LMZ779-
LMZ870-LMZ872-LMZ874-LMZ876-LMZ878 UNTIL 9 PM WEDNESDAY.
GALE WARNING...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
LMZ868 UNTIL 3 AM THURSDAY.
SMALL CRAFT ADVISORY...NEARSHORE WINTHROP HARBOR TO BURNS HARBOR UNTIL
10 PM WEDNESDAY.
SMALL CRAFT ADVISORY...NEARSHORE BURNS HARBOR TO MICHIGAN CITY IN UNTIL 4 AM THURSDAY.
&&
$$
