259 PM CDT
LOW PRESSURE SYSTEM WHICH IS TO MOVE ACROSS THE REGION TUESDAY AND
TUESDAY NIGHT IS THE MAIN FORECAST FOCUS TODAY.
IN THE NEAR TERM...A BEAUTIFUL LATE OCTOBER AFTERNOON IS IN PROGRESS
AS HIGH PRESSURE MOVES THROUGH THE LOWER MISSISSIPPI AND OHIO
VALLEYS. STRONG SURFACE PRESSURE FALLS ARE ALREADY DEVELOPING ACROSS
THE CENTRAL PLAINS HOWEVER...IN RESPONSE TO UPPER TROUGH MOVING
ACROSS THE WESTERN CONUS. LOW PRESSURE WILL MOVE TO EASTERN NEBRASKA
OVERNIGHT...WITH STRONG WARM ADVECTION DEVELOPING ACROSS THE MIDWEST
THANKS TO 50+ KNOT LOW LEVEL JET INDUCED BY THIS DEVELOPING STORM
SYSTEM. MID AND HIGH CLOUD COVER IS ALREADY ON THE INCREASE WEST OF
THE MISSISSIPPI RIVER...AND THIS WILL SPREAD TO THE EAST/NORTHEAST
TONIGHT AS LOW LEVEL SOUTHERLY FLOW INCREASES. LOW LEVELS ARE
INITIALLY FAIRLY DRY ACROSS THE IMMEDIATE AREA...AND MODEL FORECASTS
CONTINUE TO SHOW CONTINUITY WITH PAST SEVERAL RUNS IN FOCUSING
DEEPER SATURATION AND PRECIPITATION POTENTIAL FROM THE IA/MN BORDER
REGION EAST INTO WI LATER TONIGHT ALONG ELEVATED WARM FRONTAL ZONE
WHICH DEVELOPS AND STRENGTHENS ACROSS THESE AREAS. WHILE MAIN FOCUS
IS EXPECTED TO BE NORTH OF THE IL/WI BORDER...ISENTROPIC FORECASTS
OF CONDENSATION PRESSURE DEFICITS ON THE 300-305 KELVIN SURFACES
SHOW A VERY SHARP GRADIENT BETWEEN DRIER AIR TO THE SOUTH AND
SATURATING AIR TO THE NORTH ALONG THE IL BORDER. THUS WILL BE
CARRYING SOME LOW CHANCE POPS ALONG THE BORDER AFTER MIDNIGHT
TONIGHT. INCREASING SOUTH FLOW AND LOW LEVEL WARM ADVECTION WILL
LIKELY RESULT IN TEMPERATURES BECOMING STEADY OR EVEN RISING A FEW
DEGREES ACROSS THE WESTERN PARTS OF THE CWA OVERNIGHT.
GUIDANCE HAS SETTLED ON A SOLUTION OF BRINGING THE SURFACE LOW EAST
ALONG THE IL/WI BORDER OR JUST SOUTH OF IT TUESDAY AND TUESDAY
NIGHT...MODULATED BY STRONG LOW LEVEL WARM ADVECTION AND BROAD AREA
OF UPPER LEVEL DIVERGENCE ASSOCIATED WITH RIGHT ENTRANCE REGION OF
STRONG UPPER JET OVER THE NORTHERN LAKES/ONTARIO. MAIN FOCUS FOR
PRECIP APPEARS TO REMAIN NORTH OF WARM FRONT ALONG ELEVATED
BAROCLINIC ZONE ON THE NOSE OF THE LOW LEVEL JET FROM WISCONSIN EAST
INTO MICHIGAN DURING THE DAY...THOUGH WILL LIKELY INCREASE ACROSS
THE KLOT CWA IN THE AFTERNOON AS THE LOW MOVES INTO THE AREA FROM
THE WEST. FORECAST SOUNDINGS INDICATE WARM SECTOR IS FAIRLY CAPPED
WITH STRONG MID-LEVEL WARM ADVECTION INVERSION. WARM LAYER ERODES
LATER IN THE DAY AND EVENING AS HEIGHT FALLS BECOME MORE IMPRESSIVE
ACROSS THE REGION IN RESPONSE TO SHORT WAVE TRACKING ACROSS THE
UPPER MIDWEST TUESDAY NIGHT. THEREFORE WILL MAINTAIN ONLY LOW CHANCE
POPS ALONG THE IL/WI BORDER THROUGH THE MORNING...INCREASING POPS
DURING THE AFTERNOON AND EVENING HOURS. FORECAST SOUNDINGS DO DEPICT
PERHAPS 200 J/KG SOME SKINNY MLCAPE DEVELOPING AS LOW LEVEL MOISTURE
INCREASES ALONG THE FRONT LATE IN THE DAY. TUESDAY WILL LIKELY BE
THE LAST 70+ DEGREE DAY FOR SOME TIME. TEMPS A LITTLE TRICKY GIVEN
PROXIMITY OF LOW AND FRONTAL ZONE...THOUGH WARM SECTOR TEMPS IN THE
MID-UPPER 70S LOOK DOABLE IF CLOUD COVER DOESNT GET TOO THICK OR
PRECIP COOLS THINGS DOWN. SOUTHERN/SOUTHEASTERN PARTS OF THE FA HAVE
THE BEST SHOT AT THESE UNSEASONABLY MILD TEMPS...WHILE THE FAR
NORTHWEST PARTS OF THE CWA WILL BE MORE PRONE TO CLOUDS AND PERHAPS
PRECIP. WINDY CONDITIONS WILL PREVAIL AHEAD OF THE LOW AS
WELL...WITH GUSTS AROUND 30 MPH FROM THE LATE MORNING INTO THE
EARLY/MID AFTERNOON HOURS.
LOW PASSES TO THE EAST AND FRONT SETTLES SOUTHEAST INTO DOWNSTATE IL
AND IND LATER TUESDAY NIGHT AND WEDNESDAY...TAKING PRECIP CHANCES
OFF TO THE SOUTHEAST WITH IT. HOWEVER...LONG WAVE POSITIVE TILT
UPPER TROUGH CONTINUES TO SLOWLY DRIFT SOUTHEAST ACROSS THE AREA
INTO THURSDAY...KEEPING SOME THREAT OF PRECIP ALONG AND NORTH OF THE
LOW-LEVEL BAROCLINIC ZONE. SOUTHERN COUNTIES OF KLOT CWA ARE MOST AT
RISK OF SEEING SOME ADDITIONAL RAIN DURING THIS PERIOD...THOUGH IT
DOES APPEAR THAT AS LARGE SCALE VERTICAL MOTION MAXIMIZES WITH
SHARPENING UPPER TROUGH WEDNESDAY AFTERNOON/EVENING THAT RAIN COULD
EXTEND FARTHER NORTH ACROSS THE FORECAST AREA. ONE THING FOR SURE IS
THAT MUCH COOLER TEMPERATURES WILL BE THE RULE...AS MAX TEMPS
STRUGGLE TO GET MUCH PAST 50 OR THE LOWER 50S WEDNESDAY AND THURSDAY
BEHIND THE FRONT. HIGH PRESSURE EVENTUALLY BUILDS IN FROM THE WEST
THURSDAY NIGHT IN SUBSIDENCE BEHIND UPPER TROUGH.
IN THE EXTENDED RANGE...ECMWF/GFS BASED GUIDANCE BOTH DIG ANOTHER
QUICK MOVING SHORT WAVE ACROSS THE UPPER MIDWEST/WESTERN LAKES
FRIDAY AND FRIDAY NIGHT THAT MAY PRODUCE SOME LIGHT RAIN MAINLY
NORTH OF THE CWA. SFC HIGH PRESSURE THEN MOVES ACROSS SATURDAY
BEFORE WINDS TURN BACK TO THE SOUTH SUNDAY/MONDAY.
RATZER
&&
.FIRE WEATHER...
315 AM CDT
TUESDAY AFTERNOON WILL NEED TO BE MONITORED FOR POTENTIAL INCREASED
FIRE DANGER AS UNSEASONABLY WARM CONDITIONS AND STRONG WINDS ARE
EXPECTED. ONE OF THE BIGGER WILD CARDS IS WITH RESPECT TO HOW MUCH
CLOUDINESS THERE WILL BE...SHOULD CLOUDS END UP BEING LESS PROMINENT
THEN SUNSHINE WOULD LIKELY RESULT IN BETTER MIXING. THIS WOULD
LIKELY RESULT IN WARMER TEMPERATURES...LOWER DEWPOINTS/RH...AND
STRONGER WIND GUSTS. AT THIS POINT THE POTENTIAL FOR RED FLAG
CRITERIA BEING MET APPEARS LOW...BUT IT WOULDNT BE TOO GREAT OF A
STRETCH FOR THERE TO BE WIND GUSTS OVER 30 MPH AND RH VALUES
DROPPING TO 30-35 PERCENT. THE GREATEST POTENTIAL FOR CONDITIONS TO
BECOME MORE PROBLEMATIC FOR FIRE WEATHER WILL BE OVER NORTHWEST
INDIANA AND SOUTH OF INTERSTATE 80 IN ILLINOIS. FARTHER NORTH AND
WEST CLOUD COVER AND SLIGHTLY HIGHER RH SHOULD LESSEN THE FIRE
WEATHER DANGER SOMEWHAT.
IZZI
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 22Z...
* GUSTY SOUTHERLY WINDS TUESDAY
* EARLY MORNING LLWS
* CHANCES FOR SHRA/TSRA TUESDAY LATE AFTERNOON
BEACHLER
//DISCUSSION...UPDATED 18Z...
WEAK SURFACE RIDGING CONTINUES TO MOVE ACROSS SOUTHERN AND CENTRAL
ILLINOIS...AND WINDS ACROSS ALL TERMINALS HAVE BECOME WESTERLY
THROUGH THE AFTERNOON HOURS. THERE MAY BE THE OCCNL GUST INTO THE
LOWER TO MIDDLE TEENS THROUGH THE EARLY EVENING...BUT THE MAJORITY
OF THE TIME WILL BE SEE WITHOUT GUSTS. WINDS WILL TURN SOUTHERLY
AS THE RIDGE MOVES EAST OVERNIGHT. A SURFACE LOW IS FORECAST TO
DEVELOP ACROSS WESTERN NEBRASKA LATER THIS AFTERNOON...AND SLIDE
EAST ACROSS THE REGION INTO TOMORROW. AS THIS HAPPENS...AN
ELEVATED WARM FRONT WILL LIFT NORTH ACROSS THE TERMINALS...AND A
VERY STRONG LOWER LEVEL JET WILL PUNCH ACROSS THE TERMINALS IN THE
MORNING HOURS. FROM ROUGHLY THE 10-11Z TIME FRAME THROUGH ROUGHLY
15-16Z...50 TO 55 KT WINDS AT OR AROUND 2 KFT WILL REMAIN ALOFT.
DUE TO THIS...WILL KEEP THE MENTION OF LLWS THROUGH 15Z...WHEN
MIXING IS EXPECTED TO INCREASE AND TRANSPORT SOME OF THE HIGHER
MOMENTUM AIR DOWN...ALLOWING GUSTS INTO THE 25 KT RANGE. THE
OVERALL TRACK OF THE SURFACE LOW WILL PLAY A CRITICAL ROLL INTO
THE OVERALL TIMING OF PRECIPITATION...AND HOW MUCH THUNDER IS
EXPECTED. FOR NOW...EXPECTING THE CHANCES FOR SHOWERS WITH
EMBEDDED THUNDER TO INCREASE IN LIKELIHOOD BEYOND 21Z
TOMORROW...WITH THE BEST CHANCES AS THE LOW PASSES OVERHEAD AND
THE COLD FRONT SLIPS BY...WHICH IS LATER THAN THE PRESENT TAFOR.
CIGS SHOULD REMAIN VFR THROUGH THE PERIOD AND ARE NOT EXPECTED TO
FALL TO LIKELY IFR LEVELS UNTIL THE COLD AIR ADVECTION REGIME
TAKES OVER LATE TUESDAY NIGHT AND INTO WEDNESDAY MORNING.
SHEA
//ORD AND MDW CONFIDENCE...UPDATED 22Z...
* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS THROUGH THE EVENING
* MEDIUM CONFIDENCE IN LLWS FORECAST/INTENSITY
BEACHLER
//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...
TUESDAY NIGHT...STRONG/GUSTY WESTERLY WINDS SHIFTING NORTH. MVFR
CIGS POSSIBLE LATE. CHANCE OF SHRA. CHANCE OF TSRA.
WEDNESDAY...MVFR/IFR POSSIBLE EARLY. CHANCE OF SHRA.
THURSDAY AND FRIDAY...SLIGHT CHANCE OF SHRA.
SATURDAY AND SUNDAY...VFR.
JEE
&&
.MARINE...
229 PM CDT
A COLD FRONT MOVED THROUGH THE REGION LAST NIGHT LEAVING
NORTHWEST FLOW IN ITS WAKE...BUT THIS FRONT WILL LIFT BACK NORTH
OVERNIGHT WITH WINDS COMING BACK AROUND TO THE SOUTHWEST AS HIGH
PRESSURE PUSHES EAST ACROSS THE CENTRAL PLAINS. THE PRESSURE
GRADIENT WILL TIGHTEN AHEAD OF THE LOW ON TUESDAY WITH WINDS
INCREASING INTO THE 20 TO 25 KT RANGE...WITH OCCASIONAL GUSTS
AROUND 30 KT...ACROSS SOUTHERN LAKE MICHIGAN. THIS MAY PROMPT A
SMALL CRAFT ADVISORY FOR SOME OF THE INDIANA AND ILLINOIS
NEARSHORE WATERS. WINDS WILL BEGIN TO DIMINISH BY LATE TUESDAY
EVENING AS THE LOW TRACKS ACROSS SOUTHERN LAKE MICHIGAN. WINDS
WILL RETURN TO NORTHERLY BEHIND THE LOW AND ONCE AGAIN INCREASE TO
AROUND 25 KT THROUGH WEDNESDAY EVENING UNTIL HIGH PRESSURE BEGINS
TO BUILD ACROSS THE LAKE FROM THE NORTH ALLOWING WINDS TO
DIMINISH.
BMD
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&
$$
