756 PM CDT
FIRST WAVE OF SHOWERS CONTINUES TO SLOWLY WEAKEN AS IT ATTEMPTS
TO MOVE EASTWARD INTO SLIGHTLY DRIER/MORE STABLE AIRMASS. NEXT
WAVE OF SHOWERS/EMBEDDED THUNDER NEARING THE MS RIVER SHOULD MAKE
SLOW BUT STEADY PROGRESS EAST OVERNIGHT. MODELS CONTINUE TO
SUGGEST WEAK...ALBEIT SUFFICIENT...INSTABILITY TO MAINTAIN AT
LEAST A SLIGHT CHANCE OF THUNDER IN THE GRIDS OVER OUR WESTERN CWA
OVERNIGHT.
MAIN CHANGE TO GOING FORECAST WAS TO BUMP UP LOW TEMPS 1 TO 2
CATEGORIES OVER GOING FORECAST. EXTENSIVE CLOUD COVER AND
INCREASING DEWPOINTS SHOULD LARGELY PUT THE KIBOSH ON TEMPS
FALLING...SO LOWS MOST AREAS SHOULD HOLD IN THE UPPER 50S/LOWER
60S.
UPDATED GRIDS/ZFP ARE OUT.
IZZI
//PREV DISCUSSION...
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 06Z...
* SCATTERED SHOWER ACTIVITY MOVING IN OVER THE NEXT FEW HOURS WITH
MORE WIDESPREAD RAIN EXPECTED TO ARRIVE TOWARD DAYBREAK.
* RAIN CONTINUING INTO THE AFTERNOON BEFORE ENDING DURING THE LATE
AFTERNOON OR EARLY EVENING.
* SOUTHEAST WINDS TURNING EAST OR NORTHEAST TOWARD DAYBREAK WITH
VARIABLE WINDS POSSIBLE LATE MORNING AS LOW PRESSURE MOVES
OVERHEAD OR JUST TO THE SOUTH. WINDS THEN TURN NORTHWEST AND
INCREASE SOMETIME MID OR LATE AFTERNOON AS A COLD FRONT PASSES.
* PERIODIC MVFR CIGS BECOMING MORE PERSISTENT AS RAIN SHOWERS
BECOME MORE WIDESPREAD...POTENTIAL FOR IFR AFTER DAYBREAK
THROUGH THE AFTERNOON.
* LOW CHANCE FOR EMBEDDED THUNDERSTORMS.
MDB
//DISCUSSION...UPDATED 06Z...
LOW PRESSURE CONTINUES TO BETTER ORGANIZE ACROSS EASTERN IOWA AND
WESTERN ILLINOIS WHILE MOVING SLOWLY EASTWARD. BANDS OF SHOWERS
CONTINUE TO MOVE NORTHWARD ACROSS NORTH CENTRAL ILLINOIS AND ARE
NOW MOVING INTO THE CHICAGO METRO AREA. CIGS ARE A MIX OF MVFR/VFR
WITH SOME IFR IN SPOTS. THE LOW WILL INTENSIFY THROUGH THURSDAY
MORNING AS IT TRACKS EASTWARD. AS THIS OCCURS RAIN SHOULD BECOME
MORE WIDESPREAD ACROSS THE TERMINALS WITH EMBEDDED THUNDER
POSSIBLE. CEILINGS WILL LIKELY REMAIN RATHER VARIABLE FOR THE REST
OF THE NIGHT BUT EXPECT THAT MORE SOLID MVFR AND AREAS OF IFR WILL
DEVELOP AS THE RAIN BECOMES MORE WIDESPREAD TOWARD DAYBREAK.
VISIBILITY WILL ALSO VARY WITH PRIMARILY MVFR IN RAIN BUT IFR
PERIODS WILL BE POSSIBLE UNDER HEAVIER EMBEDDED AREAS.
THUNDERSTORMS MAY ALSO BE EMBEDDED BUT CONFIDENCE IN HOW NUMEROUS
THEY WILL BE OR WHEN EXACTLY THEY MAY AFFECT A GIVEN TERMINAL IS
LOW...THE COULD OCCUR AT JUST ABOUT ANY TIME BETWEEN NOW AND
THURSDAY AFTERNOON.
THE PASSAGE OF THE LOW WILL CAUSE HAVOC WITH THE WIND FORECAST AS
IT WILL BE PASSING OVER OR CLOSE TO EACH OF THE TERMINALS.
FORECAST GUIDANCE IS MIXED ON WHETHER IT MOVES JUST TO THE SOUTH
OR RIGHT OVERHEAD INTO THURSDAY AFTERNOON. SOUTHEASTERLY WINDS
WILL TURN MORE EASTERLY THEN PROBABLY END UP LIGHT AND VARIABLE
DURING THE MORNING AS THE LOW MOVES ACROSS. RFD WILL BE THE
EXCEPTION AS THEY SHOULD TURN NORTH OR NORTHWESTERLY MORE QUICKLY
THIS MORNING. ONCE THE LOW AND AN ASSOCIATED COLD FRONT PASS
DURING THE AFTERNOON WINDS WILL SHIFT TO THE WEST-NORTHWEST OR
NORTHWEST AND INCREASE IN SPEED. RAIN SHOWERS WILL COME TO AN END
AS THE FRONT PASSES FROM WEST TO EAST DURING THE LATE AFTERNOON OR
EARLY EVENING WITH CEILINGS AND VISIBILITY ALSO IMPROVING INTO
EARLY EVENING. WILL NEED TO WATCH THE TIMING OF THIS AS THIS
SYSTEM HAS BEEN A SLOW ONE SO IMPROVEMENT MAY NEED TO BE SLOWED
SLIGHTLY WITH LATER ISSUANCES.
MDB
//ORD AND MDW CONFIDENCE...UPDATED 06Z...
* HIGH CONFIDENCE IN SHOWER ACTIVITY BECOMING MORE WIDESPREAD RAIN
BY DAYBREAK AND CONTINUING INTO THURSDAY AFTERNOON.
* HIGH CONFIDENCE IN MVFR CIGS OCCURRING BUT MEDIUM CONFIDENCE ON
TIMING/DURATION.
* LOW CONFIDENCE IN IFR FORECAST...THOUGH WOULD BE MOSTLY LIKELY
FROM MID MORNING INTO EARLY AFTERNOON.
* LOW CONFIDENCE THAT THUNDERSTORMS WILL OCCUR AND WHEN EXACTLY
THEY MIGHT...COULD BE ANYTIME FROM DAYBREAK INTO MID AFTERNOON.
MDB
//OUTLOOK FOR ORD/MDW FOR 12Z FRIDAY-12Z WEDNESDAY...UPDATED 00Z...
FRIDAY...SHOWERS...MVFR...AND POSSIBLE IFR IN THE MORNING. STRONG
NW WINDS BEHIND THE COLD FRONT.
SATURDAY...VFR.
SUNDAY THROUGH TUESDAY...SLIGHT CHANCE OF SHOWERS...OTHERWISE VFR.
JEE
&&
.MARINE...
243 PM CDT
A LOW PRESSURE 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.
&&
$$
