338 PM CDT
MAIN FORECAST CONCERNS ARE WITH PRECIP TRENDS OVER THE NEXT 24
HOURS WITH A CONTINUED SLIGHT CHANCE FOR THUNDERSTORMS...AND WITH
SLIGHTLY COOLER TEMPS GOING INTO THE END OF THE WORK WEEK.
LATEST RADAR IMAGERY DEPICTING MAIN AREA OF PRECIP WHICH HAS
STAYED JUST TO THE WEST OF THE CWA FOR THE MOST OF THIS AFTERNOON
HAS FINALLY BEGUN TO WORK ITS WAY INTO PORTIONS OF THE WESTERN
CWA. AS AN UPPER LEVEL TROUGH OVER THE CENTRAL PLAINS AND
ATTENDANT SURFACE LOW SLOWLY PROGRESS TO THE EAST...FORCING FOR
ASCENT ALSO CONTINUES TO SLOWLY INCREASE...BUT WITH BEST FORCING
STILL REMAINING JUST OUTSIDE OF THE CWA. SLOW IS THE KEY WORD HERE
AS THIS MAIN AXIS OF PRECIPITATION HAS NOT WORKED ITS WAY EAST AS
MUCH TODAY AS WAS PREVIOUSLY FORECAST. SO HAD BROUGHT DOWN POPS
FOR THIS AFTERNOON ACROSS THE WESTERN HALF OF THE CWA...MAINLY
KEEPING CHANCE POPS FOR THE FAR WESTERN PORTION OF THE CWA. A FEW
LIGHTNING STRIKES HAVE BEEN REPORTED TODAY AS LATEST RUC ANALYSIS
CONTINUES TO INDICATE AN AXIS OF WEAK INSTABILITY EXTENDING FROM
CENTRAL WISCONSIN SOUTHWEST INTO NORTHEAST MISSOURI...WHERE
500-1000 J/KG OF MUCAPE CURRENTLY RESIDE. WITH THE MAIN AREA OF
PRECIPITATION AND CLOUD COVER STAYING JUST TO THE WEST OF THE
CWA...AREAS IN NORTHEAST ILLINOIS AND NORTHWEST INDIANA WERE ABLE
TO RISE QUITE NICELY TODAY WITH THE HELP OF SUNNY SKIES. TEMPS
ROSE TO THE UPPER 70S TODAY ACROSS MUCH OF THE CWA WITH EVEN SOME
AREAS OVER THE SOUTHERN FRINGE OF THE CWA GETTING FAIRLY CLOSE TO
THE 80 MARK.
WILL CONTINUE THE USE OF THE WORD SLOW AS WE TRANSITION INTO
TONIGHT...AS I THINK THAT THIS EASTERLY PROGRESSION OF THE MAIN
AXIS OF PRECIP WILL NOT QUITE PUSH ALL THE WAY EAST THROUGH THE
REMAINDER OF THE FORECAST AREA...WITH THE WEST AND SOUTHWEST HALF
OF THE CWA OBSERVING THE BEST CHANCE FOR PRECIP TONIGHT. DESPITE
THE AFOREMENTIONED LONGWAVE TROUGH AND SEVERAL WAVES OF ENERGY
ROUNDING THE BASE OF THIS TROUGH...I THINK SOME INITIAL DRIER
CONDITIONS WILL PLAY MORE OF A FACTOR TONIGHT AS AN EASTERLY
COMPONENT TO THE WIND FIELD WILL HELP KEEP THIS DRIER AIR IN
PLACE. THEN FORECAST SOUNDINGS AND TIME HEIGHTS INDICATING THE
ENTIRE COLUMN TO FINALLY SATURATE CLOSER TOWARDS THE EARLY
THURSDAY MORNING TIME FRAME FOR A GOOD PORTION OF THE CWA WITH ALL
AREAS IN NORTHEAST ILLINOIS TO FINALLY OBSERVE THIS PRECIP. THE
EXCEPTIONS WILL LIKELY BE AREAS IN NORTHWEST INDIANA WHERE THE
ONSET OF PRECIP WILL CONTINUE TO BE DELAYED. THE CURRENT
INSTABILITY AXIS IS FORECAST TO ALSO SHIFT EAST WITH TIME TONIGHT
INTO EARLY THURSDAY AS THIS TROUGH OF LOW PRESSURE SHIFTS
EAST...HELPING TO ALSO BRING IN SOME HIGHER DEWPOINT AIR WITH
CURRENT OBSERVATIONS SHOWING THAT UPPER 50 DEWPOINT AIR AS NOT
THAT FAR AWAY. THUS...ALL OF THIS WILL HELP WITH THE POSSIBILITY
OF THUNDER TO BE OBSERVED ACROSS THE CWA TONIGHT INTO EARLY
THURSDAY.
THURSDAY DOES NOT APPEAR TO BE THE BEST DAY AS I HAVE SLOWED THE
PROGRESSION OF THIS PRECIP AXIS FOR THURSDAY KEEPING THE HIGHEST
POPS ALMOST OVERHEAD. THIS DUE IN PART TO THE SLOW NATURE OF THE
LONG WAVE TROUGH...AND WITH A SHARP SHORT WAVE TROUGH TO PUSH EAST
ON THE BACKSIDE OF IT. ALTHOUGH INSTABILITY WILL BE ON THE
DECREASE THROUGHOUT THE DAY...DO FEEL THERE WILL REMAIN A SLIGHT
CHANCE FOR THUNDER FOR MOST OF THE DAY AND HAVE THE GRIDS TO
REFLECT THIS. WITH THIS PRECIP AND CLOUD SHIELD AS WELL A COOLER
AIR MASS MOVING IN...TEMPS WILL BE COOLER WITH HIGH TEMPS ONLY
FORECAST TO RISE INTO THE LOW AND MID 60S.
AS THIS UPPER LEVEL TROUGH WILL CONTINUE TO BE SLOW TO
EXIT...CYCLONIC FLOW WILL REMAIN IN PLACE WITH GUIDANCE INDICATING
ANOTHER WAVE WILL SHIFT EAST ACROSS THE REGION ON FRIDAY. THIS
COINCIDING WITH STEEPENING LAPSE RATES WILL PROVIDE THE SETUP FOR
CLOUD COVER TO REMAIN AS WELL AS CHANCES FOR RAIN SHOWERS. HAVE
OPTED TO LEAVE THE MENTION OF LIGHT SHOWERS ACROSS THE CWA ON
FRIDAY...BUT FEEL THAT ANYTHING THAT DOES FALL SHOULD BE BRIEF AND
LIGHT IN NATURE.
RODRIGUEZ
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 22Z...
* LINE OF SHRA AND ISOLATED TS TO THE WEST OF THE TERMINALS...NOT
EXPECTED TO REACH THE TERMINALS.
* ANOTHER ROUND OF PRECIP ARRIVES BY 10Z...BUT TIMING OF ONSET IS UNCERTAIN.
* MVFR AND LOWER CIGS LATE TONIGHT AND THURSDAY.
JEE
//DISCUSSION...UPDATED 18Z...
LOW PRESSURE ACROSS IOWA IS EXPECTED TO SLOWLY MOVE EASTWARD ACROSS
NORTHERN ILLINOIS THROUGH THE PERIOD. SHOWERS AND THUNDERSTORMS WILL
REMAIN WEST OF THE TERMINALS THROUGH THE AFTERNOON...WITH ONLY A
SMALL CHANCE OF AN ISOLATED SHOWER REACHING KRFD.
TONIGHT THINGS GO DOWN HILL...ESPECIALLY AFTER MIDNIGHT. IT APPEARS
THE SHOWERS WILL BE SLOW TO PROGRESS EASTWARD DURING THE EVENING.
HOWEVER...AFTER 08 UTC A LEAD MID LEVEL DISTURBANCE...NOW ACROSS
SOUTHWESTERN MISSOURI...WILL LIFT NORTHWARD ACROSS ILLINOIS AND
ALLOW SHOWERS TO DEVELOP FARTHER NORTH AND EAST ACROSS THE AREA.
BUFFER MODEL SOUNDINGS INDICATE RAPIDLY MOISTENING PROFILES DURING
THE EARLY MORNING HOURS...WHICH LOOKS TO SUPPORT A PERIOD OF DECENT
RAINFALL ACROSS THE AREA THROUGH AT LEAST EARLY TOMORROW MORNING.
THEREFORE...I WOULD NOT BE SURPRISED TO SEE MVFR VIS IN SHRA DURING
THIS PERIOD.
I THINK THERE MAY BE A BREAK IN THE RAIN DURING THE LATE MORNING
HOURS AS THE INITIAL WAVE CLEARS THE AREA. HOWEVER...I EXPECT
ADDITIONAL SHOWERS TO DEVELOP ON THE BACK SIDE OF THE SURFACE LOW AS
A SECOND MID LEVEL DISTURBANCE MOVES ACROSS THE AREA IN THE AFTERNOON.
ASIDE FROM PRECIPITATION CHANCES...THE OTHER MAJOR CONCERN ARE CIGS.
CIGS WILL LIKELY DROP INTO THE LOWER MVFR RANGE BY THURSDAY MORNING.
I AM NOT EXPECTING MUCH IF ANY IMPROVEMENT IN THE CIGS DURING THE
DAY. SO LOW END MVFR WITH SOME PERIODS OF IFR CIGS ARE EXPECTED
DURING THE DAY ON THURSDAY.
KJB
//ORD AND MDW CONFIDENCE...UPDATED 22Z...
* MEDIUM CONFIDENCE IN TIMING OF PRECIP ONSET TONIGHT...HIGH
CONFIDENCE IN INCREASING COVERAGE.
* MEDIUM CONFIDENCE IN CIG FORECAST.
* HIGH CONFIDENCE IN WIND FORECAST.
JEE
//OUTLOOK FOR ORD/MDW FOR 00Z FRIDAY-12Z WEDNESDAY...UPDATED 12Z...
* THURSDAY NIGHT AND FRIDAY...SHOWERS. MVFR AND IFR POSSIBLE.
* SATURDAY...VFR
* SUNDAY THROUGH TUESDAY...SLIGHT CHANCE OF SHOWERS...OTHERWISE
VFR
SHEA
&&
.MARINE...
243 PM CDT
A LOW PRESSSURE COMPLEX EXTENDING FROM FAR SOUTHERN MANITOBA TO
THE LOWER MO RIVER VALLEY WILL STRENGTHEN AS IT MOVES EAST TO
WESTERN ONTARIO...WI AND IL OVERNIGHT. THE LOW WILL CONTINUE TO
DEEPEN AS IT MOVES E ACROSS LAKE MICHIGAN THU AND THU EVE.
A STRONG NW FLOW OF MUCH COOLER AIR FROM NORTHER CANADA WILL BE
USHERED SOUTHEASTWARD ACROSS THE UPPER GREAT LAKES IN THE WAKE OF
THE LOW. DUE TO THE STRENGTH OF THE LOW AND THE COLD AIR ADVECTION
NW GALES OF AROUND 35 KT ARE A GOOD BET FOR FRI INTO SAT.
TRS
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WATCH...LMZ080-LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-
LMZ567-LMZ669-LMZ671-LMZ673-LMZ675-LMZ777-LMZ779-LMZ868-
LMZ870-LMZ872-LMZ874-LMZ876-LMZ878...9 AM FRIDAY TO NOON
SATURDAY.
&&
$$
