343 AM CDT
MAIN FORECAST CONCERN THIS MORNING IS WITH EVOLUTION OF
PRECIPITATION ACROSS THE FORECAST AREA TODAY...AND ITS GRADUAL
DISSIPATION FROM THE NORTHWEST.
CLOSED UPPER LOW WAS LOCATED OVER SOUTHERN MISSOURI EARLY THIS
MORNING...WITH ITS OCCLUDED SURFACE LOW POISED TO CROSS THE
MISSISSIPPI JUST SOUTH OF KSTL. NEARLY STATIONARY COLD FRONT WHICH
SLIPPED INTO THE FORECAST AREA ON WEDNESDAY WAS ALONG THE SOUTHERN
BORDER OF THE CWA. FAIRLY IMPRESSIVE BAND OF PRECIP EXISTS WITHIN
ELEVATED FRONTAL ZONE ON THE COOL SIDE OF THE SURFACE BOUNDARY...
EXTENDING FROM WESTERN ILLINOIS NORTHEAST ACROSS SOUTHEAST WISCONSIN
AND INTO LOWER MICHIGAN AT 08Z. OVERALL RADAR TREND INDICATES
NARROWING AND SLIGHT WEAKENING OF THE REFLECTIVITY RETURNS OVER THE
PAST FEW HOURS...AND THIS TREND IS EXPECTED TO CONTINUE AS COUPLED
UPPER JET STRUCTURE BREAKS DOWN AND LOW LEVEL FRONTOGENESIS BEGINS
WEAKENS AS SYSTEM TO THE SOUTH BEGINS TO FILL. STRONGEST DEEP LAYER
ASCENT...NOTED IN LAYER Q-VECTOR CONVERGENCE AND OMEGA FIELDS...WILL
BE ACROSS THE FORECAST AREA THIS MORNING THEN WILL PASS OFF TO THE
EAST/SOUTHEAST OF THE CWA WITH THE UPPER TROUGH AXIS THROUGH EARLY
EVENING. GUIDANCE IN GENERALLY GOOD AGREEMENT WITH THESE TRENDS
TODAY...AND INDICATE RAIN SHOULD END ACROSS THE NORTHERN PARTS OF
THE CWA BY MIDDAY...AND ACROSS THE SOUTH/SOUTHEAST COUNTIES OF THE
CWA BY EARLY EVENING. RAINFALL...WHICH HAS EXCEEDED 0.75 INCHES OVER
PARTS OF NORTH CENTRAL ILLINOIS...SHOULD BECOME MORE FOCUSED ACROSS
THE SOUTHERN COUNTIES THIS MORNING...WITH SOME AREAS THERE PICKING
UP PERHAPS 0.25 TO 0.50 INCHES BEFORE RAIN ENDS. BLUSTERY NORTHEAST
WINDS GUSTING TO 35 MPH AT TIMES THROUGH MIDDAY WILL MAKE FOR A
RATHER RAW-FEELING DAY...WITH TEMPS STRUGGLING TO BREAK THE 50
DEGREE MARK IN MANY AREAS AND PREFER COOLER MAV GUIDANCE.
CLOSED LOW SLOWLY FILLS AND TRACKS OFF TO THE SOUTHEAST INTO THE
SOUTHERN APPALACHIANS TONIGHT...ALLOWING AMPLIFIED UPPER RIDGE TO
SPREAD ACROSS THE AREA AND SURFACE HIGH PRESSURE RIDGE TO MOVE INTO
NORTHWEST IL BY FRIDAY MORNING. CLEARING SKIES...DECREASING WINDS
AND COOL/LOW DEW POINT AIR SHOULD LEAD TO FAIRLY STRONG RADIATIONAL
COOLING CONDITIONS...ESPECIALLY ACROSS FAR NORTH CENTRAL IL WHICH
WILL BE CLOSER TO THE RIDGE AXIS COME MORNING. HAVE INCLUDED SOME
PATCHY FOG LATE TONIGHT THERE...WITH KRFD HAVING REPORTING 0.80
INCHES OF RAIN. FOR THE SAME REASONS HAVE GONE A LITTLE CLOSER TO
THE MUCH COLDER MAV GUIDANCE FOR NORTH CENTRAL IL TONIGHT.
SURFACE RIDGE DRIFTS ACROSS THE FORECAST AREA FRIDAY AND FRIDAY
EVENING. PLENTY OF SUNSHINE AND SLIGHT MODERATION OF TEMPS ALOFT
SHOULD HELP TO OFFSET OTHERWISE COOL EASTERLY LOW LEVEL FLOW...
WITH GUIDANCE TEMPS IN THE LOW-MID 50S LOOKING REASONABLE WITH
SHALLOW MIXING. WINDS THE SHIFT MORE SOUTHERLY FRIDAY NIGHT WITH
WARM ADVECTION RAMPING UP ABOVE THE BOUNDARY LAYER IN RESPONSE TO
LARGE SCALE TROUGH MOVING ACROSS THE WESTERN CONUS. AS HAS BEEN THE
CASE FOR MANY RUNS NOW...GUIDANCE CONTINUES TO LIFT A NEGATIVELY
TILTED MID LEVEL SHORT WAVE TROUGH OUT OF THE LARGE SCALE TROUGH AND
ACROSS THE PLAINS AND UPPER MIDWEST THROUGH THE WEEKEND. WHILE SOME
DIFFERENCES DO REMAIN AMONGST VARIOUS GUIDANCE WITH THE
SPEED/POSITION OF THE SURFACE LOW THROUGH EARLY SUNDAY...IT PASSES
WELL NORTHWEST OF THE WFO CHICAGO FORECAST AREA AND PRESENTS MAINLY
INCREASINGLY WINDY AND MILDER WEATHER. LOW LEVEL FLOW INITIALLY FROM
THE SOUTH-SOUTHEAST IS RATHER DRY PER TIME SECTIONS AND SOUNDINGS
FROM VARIOUS MODELS...AND ALL GUIDANCE IS DRY FOR THE CWA THROUGH
ABOUT 12Z SUNDAY. LONGER RANGE GFS/ECMWF RUNS WRAP OCCLUDED COLD
FRONT THROUGH THE AREA SUNDAY NIGHT...WITH THE POTENTIAL FOR SPOTTY
LIGHT PRECIP EVENTUALLY DEVELOPING IN THE NARROW LOW LEVEL MOISTURE
AXIS ALONG THE FRONT SUNDAY NIGHT ACROSS THE SOUTHEAST HALF OF THE
CWA.
STILL APPEARS THAT THE LOW LEVEL THERMAL RIDGE AXIS PASSES THROUGH
SATURDAY NIGHT...WITH THE WARM SECTOR OCCLUDING SUNDAY WITH THE
APPROACH OF THE SFC FRONT. HAVE MAINTAINED FORECAST TEMPS IN THE
GUIDANCE TEMPS IN THE UPPER 50S TO LOWER 60S LOOK OK FOR NOW GIVEN
THE LOW LEVEL THERMAL PROGS. SOUTH WINDS LOOK TO BECOME FAIRLY GUSTY
SUNDAY WITH DEEPER MIXING AHEAD OF THE SURFACE FRONT. GFS BUFFER
SOUNDINGS INDICATE 35-40 MPH GUSTS POSSIBLE.
FRONT THEN BECOMES NEARLY STATIONARY ACROSS OR JUST SOUTHEAST OF
THE CWA ON MONDAY AS IT BECOMES ALIGNED WITH THE MID/UPPER FLOW.
THIS WILL CONTINUE TO FOCUS A LOW CHANCE POP ACROSS THE SOUTHEAST
CWA MONDAY...BEFORE INCREASING AND SPREADING ACROSS THE ENTIRE
FORECAST AREA LATER MONDAY NIGHT INTO WEDNESDAY AS GUIDANCE BRINGS
ANOTHER UPPER TROUGH AND ITS ASSOCIATED SURFACE LOW ALONG THE FRONT
EARLY NEXT WEEK.
RATZER
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 12Z...
* LIGHT SHOWERS TO REMAIN AROUND THE TERMINALS...BEFORE
DIMINISHING THROUGH MID MORNING.
* LOW END MVFR CEILINGS WITH IFR STILL POSSIBLE THIS MORNING.
* STRONG NORTHEAST WINDS PERSISTING AND INCREASING THROUGH THE
MORNING...BEFORE STARTING A SLOW DOWNWARD TREND LATER THIS
AFTERNOON.
RODRIGUEZ
//DISCUSSION...UPDATED 12Z...
LESS FAVORABLE CONDITIONS THIS MORNING AS SHOWERS AND LOW CEILINGS
REMAIN ACROSS THE TERMINALS. THE SYSTEM PARTIALLY RESPONSIBLE FOR
THESE CONDITIONS WILL SLOWLY WORKS ITS WAY EAST TODAY WITH
CONDITIONS SLOWLY IMPROVING THROUGHOUT THE DAY. BEFORE THIS
OCCURS...LOW END MVFR CEILINGS CURRENTLY BEING REPORTED ALL ACROSS
THE REGION WILL CONTINUE THROUGH MOST OF THE MORNING. IFR CEILINGS
HAVE BEEN REPORTED ACROSS PORTIONS OF NORTHEAST ILLINOIS AND
NORTHWEST INDIANA OVERNIGHT...WITH SCATTERED IFR AREAS PERSISTING
THIS MORNING. AS A MOIST BOUNDARY LAYER REMAINS WITH RESIDUAL
FORCING LINGERING...STILL THINK IT MIGHT BE POSSIBLE FOR A BRIEF
PERIOD OF IFR CONDITIONS THIS MORNING BEFORE THE OVERALL UPWARD
TREND OCCURS LATER THIS MORNING. LATEST RADAR IMAGERY SHOWS AN
AREA PRECIPITATION FROM SOUTHERN WISCONSIN SOUTHWEST TO WEST
CENTRAL ILLINOIS. THIS WILL LIKELY REMAIN IN AND AROUND THE
TERMINALS...BUT WITH PRECIP TO SLOWLY DIMINISH AS FORCING IS LOST.
WITH THE WHOLE SYSTEM SLOWLY SHIFTING EAST THROUGHOUT THE
DAY...MVFR CONDITIONS WILL BE REPLACED WITH LINGERING MID LEVEL
CLOUD COVER BEFORE SKIES SCATTER OUT THIS AFTERNOON. THEN CLEAR
SKIES TO REMAIN OVERHEAD THROUGH THE REST OF THE FORECAST PERIOD.
STRONG NORTHEAST WINDS WILL CONTINUE TODAY...WITH A CONTINUED
INCREASE IN SPEEDS THROUGH MID DAY. ALTHOUGH WINDS SHOULD BE
SLOWLY DIMINISHING LATER THIS AFTERNOON...A NORTHEAST DIRECTION
WILL BE MAINTAINED INTO THE EVENING.
RODRIGUEZ
//ORD AND MDW CONFIDENCE...UPDATED 12Z...
* HIGH CONFIDENCE WITH OVERALL TRENDS OF SHOWERS THROUGH MID
MORNING.
* HIGH CONFIDENCE WITH CEILING TRENDS THIS MORNING.
* HIGH CONFIDENCE WITH WIND SPEED AND DIRECTION.
RODRIGUEZ
//OUTLOOK FOR ORD/MDW FOR 00Z SATURDAY-12Z THURSDAY...UPDATED 12Z...
FRIDAY NIGHT...VFR.
SATURDAY...VFR.
SUNDAY...SLIGHT CHANCE OF SHRA LATE...OTHERWISE VFR.
MONDAY...SLIGHT CHANCE OF SHRA...OTHERWISE VFR.
TUESDAY...SHRA LIKELY...OTHERWISE VFR.
WEDNESDAY...CHANCE OF SHRA...OTHERWISE VFR.
RODRIGUEZ
&&
.MARINE...
313 AM CDT
SURFACE LOW ACROSS SOUTHERN MISSOURI WILL CONTINUE TO DEEPEN THIS
MORNING AND SHIFT TO THE EAST...ACROSS SOUTHERN ILLINOIS. THE
OCCASIONAL GALE FORCE WINDS ACROSS THE SOUTHERN LAKE WILL CONTINUE
THROUGH THE EARLY MORNING HOURS...OR POTENTIALLY INTO THE LATE
MORNING. WINDS WILL THEN BEGIN TO ABATE...BUT STILL REMAIN IN THE
15 TO 25 KT RANGE THROUGH THE OVERNIGHT HOURS AS THE SURFACE LOW
WEAKENS AND MOVES SOUTHEAST BEFORE HIGH PRESSURE BUILDS IN THROUGH THE
END OF THE WEEK. BY THE WEEKEND...THE HIGH PRESSURE WILL MOVE EAST
AND A DEVELOPING LOW ACROSS THE CENTRAL PLAINS WILL TIGHTEN THE
GRADIENT AS IT LIFTS NORTH INTO CANADA. THIS WILL BRING THE
CHANCES FOR SOUTHERLY GALES SATURDAY NIGHT AND INTO SUNDAY.
SHEA
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ080-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-LMZ742-
LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ872-LMZ874-LMZ876-
LMZ878 UNTIL 9 AM THURSDAY.
&&
$$
