845 PM CST
SHARP UPPER TROUGH AND COMPACT...BUT FAIRLY VIGOROUS...CLOSED
UPPER LOW OVER SE KS EARLY THIS EVENING IS PROGGED TO BECOME
INCREASINGLY NEGATIVELY TILTED AS IT DEEPENS AND LIFTS NORTHEAST
OVER THE NEXT 24-36 HOURS. WIDE VARIETY OF INCLEMENT WEATHER
LIKELY TO AFFECT THE REGION THE NEXT 24 HOURS AS THIS OCCURS.
A 1008MB SURFACE LOW OVER SW MO IS LIKELY TO BEGIN DEEPENING
FAIRLY QUICKLY AS IT LIFTS NORTHEAST INTO NORTHERN ILLINOIS BY
WEDNESDAY MORNING...THEN CONTINUING TO STRENGTHEN AS IT MOVES
QUICKLY INTO SOUTHERN ONTARIO TOMORROW NIGHT. FRONTAL BOUNDARY
STRETCHING FROM THIS LOW ACROSS OUR SOUTHERN MOST COUNTIES IS
LIKELY TO BEGIN RETURNING NORTHWARD AS A WARM FRONT OVERNIGHT AS
SFC LOW TRACKS NORTHEAST. DRIZZLE AND AREAS OF RAIN NORTH OF THE
FRONT LIKELY TO CONTINUE WITH STRATUS POSSIBLY BUILDING DOWN TO
FOG OVERNIGHT...THOUGH EXPECT WINDS TO GENERALLY REMAIN STRONG
ENOUGH TO PREVENT WIDESPREAD DENSE FOG. AS WARM FRONT LIFTS NORTH
TEMPERATURES LIKELY TO RISE WELL INTO THE 50S IF NOT LOWER 60S
ENDING THE FOG THREAT.
RELATIVE LULL IN THE RAIN OVER MISSOURI AT THIS TIME IS EXPECTED
TO FILL IN OVERNIGHT AS VERY STRONG SYNOPTIC SCALE ASCENT OCCURS.
HAVE MAINTAINED THE VERY HIGH POPS OVERNIGHT WITH THE EXPECTATION
OF WIDESPREAD RAIN DEVELOPING...WITH SOME POTENTIAL FOR SOME
MODERATE TO HEAVY RAINFALL TOTALS.
THE SOUTHEAST 1/3 TO 1/2 OF THE CWA SHOULD MAKE IT INTO THE WARM
SECTOR WITH WEAK SURFACE BASED INSTABILITY DEVELOPING LATE TONIGHT
INTO WEDNESDAY MORNING IN ADVANCE OF THE APPROACHING STRONG COLD
FRONT. THERE WILL BE A NARROW WINDOW OF OPPORTUNITY WED MORNING
FOR SFC BASED THUNDERSTORM DEVELOPMENT...MAINLY EAST OF I-55...AND
WHILE INSTABILITY WILL BE VERY WEAK...EXTREME WIND SHEAR AND THE
VERY IMPRESSIVE DEEPENING OF THE SYSTEM DOES SUGGEST THAT
THUNDERSTORM POTENTIAL WILL NEED TO BE MONITORED TOMORROW MORNING.
AS SURFACE LOW PASSES...VERY STRONG WEST TO NORTHWEST WINDS WILL
USHER IN MUCH COLDER AIR MASS. THERE DOES APPEAR TO BE A SEVERAL
HOUR WINDOW OF OPPORTUNITY FOR RAIN TO CHANGE TO WET SNOW OVER OUR
NW CWA AS COLD AIR ARRIVES JUST PRIOR TO THE MORE SIGNIFICANT
PRECIP ASSOCIATED WITH THE DEFORMATION ZONE ENDS. SURFACE TEMPS
WILL LIKELY BE WARM ENOUGH TO PREVENT ANY SIGNIFICANT ACCUMS...BUT
SNOW COULD FALL HEAVILY ENOUGH FOR SHORT PERIOD OF TIME TO WHITEN
THE GROUND IN SPOTS. SOME POTENTIAL FOR SOME LIGHT SNOW SHOWERS OR
FLURRIES FARTHER EAST ACROSS THE CWA IN THE STRONG COLD AIR
ADVECTION REGIME...BUT CHANCES FOR DO APPEAR TO DIMINISH WITH
EASTWARD EXTENT.
FINALLY...WINDS COULD GET QUITE STRONG FOR A TIME TOMORROW AS LOW
CONTINUES TO DEEPEN RATHER QUICKLY AS IT DEPARTS. STRONG PRESSURE
RISES AND COLD AIR ADVECTION SHOULD HELP DEEPEN THE BOUNDARY LAYER
AIR ENOUGH TO ALLOW FOR WIND GUSTS AROUND IF NOT A BIT OVER 40
MPH IN SPOTS LATE MORNING INTO THE AFTERNOON.
NO WHOLESALE CHANGES MADE TO GOING GRIDS...THOUGH DID SHARPEN UP
THE TEMP GRADIENT ALONG THE FRONT TONIGHT INTO WED MORNING. IN
ADDITION...BUMPED UP TEMPS AND HIGHS IN THE WARM SECTOR OVER ABOUT
THE SE HALF OF THE CWA WED MORNING BEFORE SHARPENING UP THE DROP
IN TEMPERATURES IN THE AFTERNOON.
UPDATED GRIDS HAVE BEEN SENT...WILL BE FRESHENING UP TEXT PRODUCTS
SHORTLY.
IZZI
//PREV DISCUSSION...
300 PM CST
ANOTHER ROUND OF RAIN WILL ARRIVE THIS EVENING AND CONTINUE INTO THE
OVERNIGHT HOURS WITH MUCH COLDER AIR ARRIVING WEDNESDAY. EARLY
AFTERNOON WATER VAPOR IMAGERY SHOWS THE CLOSED UPPER LOW WHICH HAS
BEEN TRACKING EASTWARD FROM THE FOUR CORNERS NOW STARTING TO LIFT
NORTHEASTWARD INTO SOUTHERN KANSAS. SURFACE LOW PRESSURE CONTINUES
TO DEEPEN ACROSS EASTERN OKLAHOMA AS IT LIFTS NORTHEASTWARD ALONG AN
INVERTED TROUGH/FRONTAL BOUNDARY WHICH EXTENDS FROM THE LOW
NORTHEASTWARD ACROSS THE SOUTHERN CHICAGO METRO AND INTO FAR
SOUTHWEST LOWER MICHIGAN. AREAS OF LIGHT RAIN AND DRIZZLE CONTINUE
ACROSS THE AREA WITH MORE WIDESPREAD RAIN ON THE WAY.
TONIGHT...THE SURFACE LOW WILL MOVE NORTHEASTWARD TONIGHT AS THE
UPPER TROUGH EJECTS NORTHEASTWARD. EXPECT THAT THE SURFACE TROUGH
AXIS WILL MOVE LITTLE DURING THE EVENING BUT THEN WILL PROBABLY
SHIFT SLIGHTLY WESTWARD TOWARD DAYBREAK AS THE LOW MOVES INTO THE
AREA. MODELS HAVE CONTINUED TO SHIFT EASTWARD WITH THE TRACK OF THE
LOW WITH OBSERVED DATA AND POSITION OF THE TROUGH SUPPORTING A TRACK
IN THE CHICAGO-GARY VICINITY WEDNESDAY MORNING. A SURGE OF MID LEVEL
WARM ADVECTION WILL ARRIVE THIS EVENING AHEAD OF THE UPPER TROUGH
BRINGING A PERIOD OF STRONG FRONTOGENETICAL FORCING ACROSS THE AREA
LEADING TO ANOTHER ROUND OF WIDESPREAD RAIN. HEAVIEST RAINS WILL
FALL ACROSS THE NORTHWESTERN THIRD TO HALF OF THE AREA OR GENERALLY
WEST OF INTERSTATE 57...WHERE ANOTHER 1-1.5 INCHES OF RAIN...WITH
ISOLATED HIGHER AMOUNTS...COULD FALL. WILL CONTINUE WITH MENTION
OF THUNDER AS LOW LEVEL JET INCREASES NEAR 50 KT AND ELEVATED
INSTABILITY INCREASES FROM THE SOUTHWEST...PRIMARILY ALONG AND
EAST OF A WAUKEGAN TO LASALLE LINE. TEMP TRENDS WILL BE TOUGH
THROUGH THE NIGHT. STEADY OR RISING TEMPS WILL PROBABLY BE WHAT
PLAYS OUT WITH SOUTHEAST AREAS REMAINING STEADY AND CENTRAL AND
NORTHWEST AREAS POSSIBLY WARMING A FEW DEGREES...AS THE BOUNDARY
SHIFTS SLIGHTLY NORTHWEST AND MID LEVEL WARM ADVECTION SPREADS
OVERHEAD.
WEDNESDAY...THE SURFACE LOW WILL BE PASSING RIGHT OVERHEAD WEDNESDAY
MORNING AS THE UPPER CIRCULATION MOVES FROM NEAR THE QUAD CITIES TO
SOUTHERN WISCONSIN. A WELL PRONOUNCED DRY SLOT WILL WRAP NORTHWARD
AHEAD OF THE UPPER LOW WITH RAIN QUICKLY DIMINISHING IN COVERAGE
BETWEEN APPROX 12 AND 15Z...THOUGH IT MAY NOT COMPLETELY DRY UP. THE
ATTENDANT COLD FRONT WILL CROSS THE AREA WEDNESDAY MORNING TURNING
WINDS WESTERLY AND USHERING IN MUCH COLDER AIR. THERE IS SOME
OPPORTUNITY FOR INSTABILITY TO POOL AHEAD OF THE FRONT WITH THE
POSSIBILITY OF ENHANCED CONVECTION ALONG THE FRONT AND ON THE EDGE
OF THE UPPER LEVEL DRY SLOT DURING THE MORNING. AS A RESULT...WILL CONTINUE
CHANCE THUNDER FOR THE INDIANA COUNTIES FOR A SHORT TIME AFTER 12Z
WITH A MINIMAL POTENTIAL FOR SOME STRONG WINDS TO MIX TO THE
SURFACE. H85 TEMPS WILL FALL FROM A PEAK OF +8-10 C OVERNIGHT TO
AROUND -4 C BY WEDNESDAY EVENING. PRECIP- WISE...WITH THE UPPER
LOW PASSING JUST TO THE NORTHWEST DEFORMATION ZONE WILL BE FOCUSED
TO THE NORTH OF THE AREA BUT THE SOUTHERN END OF IT DOES LOOK TO
CROSS THE NORTHWESTERN/NORTHERN CWA. THIS RAISES CONCERNS FOR
PRECIP CHANCES CONTINUING DURING THE LATE MORNING INTO THE
AFTERNOON... PRIMARILY NORTH OF INTERSTATE 80 AND ESPECIALLY NORTH
OF INTERSTATE 88. THE COLD ADVECTION BRINGS ABOUT CONCERNS FOR
MIXED RAIN AND SNOW AND PROBABLY AT LEAST SOME LOW CHANCE THAT ALL
SNOW COULD FALL BACK TOWARDS THE ROCKFORD AREA IF THE FORCING IS
STRONG ENOUGH. WILL GO AHEAD AND INCLUDE CHANCES FOR RAIN AND SNOW
SHOWERS FOR THESE AREAS...WITH A PERIOD OF ALL SNOW FAR WEST
DURING THE AFTERNOON BUT PRECIP MAY BE WINDING DOWN BY THAT TIME.
HIGH TEMPS WILL LIKELY OCCUR AROUND DAYBREAK BEFORE FALLING OFF
THROUGH THE AFTERNOON WITH MANY AREAS PROBABLY SEEING MID/UPPER
30S TO AROUND 40 BY LATE AFTERNOON/EARLY EVENING.
THURSDAY INTO FRIDAY...WITH THE UPPER LOW LIFTING TO THE NORTHEAST
OF THE AREA A LARGER SCALE TROUGH WILL TAKE SHAPE AS A SHORTWAVE
MOVES SOUTHEASTWARD FROM THE CANADIAN PRAIRIES. THE UPPER TROUGH
AXIS WILL SWING ACROSS THE AREA THURSDAY MORNING LIKELY BRINGING AN
INCREASE IN CLOUD COVER AND POSSIBLY SOME SCATTERED PRECIPITATION.
EXPECT THAT PRECIP TYPE WOULD BE SNOW THOUGH THE LOWEST LEVELS OF
THE ATMOSPHERE DO WARM FOR A TIME AHEAD OF THE LOW BUT COOLING THEN
LOOKS TO TAKE OVER AS PRECIP ARRIVES. WILL NEED TO WATCH FOR A
POSSIBLE MIX IF WARMING LASTS LONGER THAN CURRENTLY EXPECTED. WILL
INCLUDE SLIGHT/LOW CHANCES FOR THIS THREAT BUT IT WOULD LIKELY ONLY
BE FOR A SHORT PERIOD. HIGHS THURSDAY WILL ONLY BE IN THE LOWER 40S.
A SURFACE RIDGE QUICKLY CRESTS THE AREA THURSDAY NIGHT AS AN ALBERTA
CLIPPER DROPS SOUTHEASTWARD IN THE NORTHWESTERLY UPPER FLOW. BASED
ON THE CURRENT TRACK NORTHEAST OF THE AREA THE MAIN SENSIBLE WEATHER
IMPACT WOULD BE MILDER TEMPS IN THE UPPER 40S TO AROUND 50 WITH POP
CHANCES REMAINING JUST TO THE NORTHEAST.
MDB
FRIDAY NIGHT THROUGH TUESDAY...
THE MAIN FORECAST CONCERNS DURING THE EXTENDED PERIOD WILL BE
PRECIPITATION CHANCES AND TIMING EARLY NEXT WEEK. THE MODELS AND
ENSEMBLES ARE IN DECENT AGREEMENT IN FORECASTING THE LARGE SCALE
AMPLIFICATION OF AN UPPER TROUGH ACROSS WESTERN AND CENTRAL NORTH
AMERICA BY EARLY NEXT WEEK. HOWEVER...THERE ARE SIGNIFICANT
DISAGREEMENTS WITH THE TIMING OF THE SMALLER SCALE DISTURBANCES
WHICH WILL TRANSITION THROUGH THE LARGER SCALE FLOW PATTERN.
THE MOST NOTEWORTHY DIFFERENCE IS THE FORECASTED BEHAVIOR OF THE
UPPER LOW OFF SHORE OF THE SOUTHWESTERN CONUS. THIS WILL LIKELY BE
THE MAJOR WILD CARD FOR THE SENSIBLE WEATHER ACROSS NORTHERN
ILLINOIS AND NORTHWESTERN INDIANA EARLY NEXT WEEK...WITH THE
POTENTIAL FOR ANOTHER DECENT RAINFALL EVENT AS THIS UPPER LOW EJECTS
ACROSS THE SOUTHERN ROCKIES AND AROUND THE BASE OF THE LARGER SCALE
TROUGH EARLY NEXT WEEK.
THE 12 UTC ECMWF IS QUICKER WITH THIS PROCESS AND BRINGS RAINFALL TO
THE AREA AS EARLY AS SUNDAY AS A FRONTAL ZONE SETS UP ACROSS
NORTHERN ILLINOIS. THIS SCENARIO COULD BRING US ANOTHER
PRECIPITATION EVENT SIMILAR TO TODAY AND TONIGHT BY MONDAY.
HOWEVER...THE 12 UTC GFS IS SLOWER WITH THE PROGRESSION OF THE
SOUTHWESTERN CONUS ENERGY. NOT TO SURPRISING...THE ENSEMBLES
INDICATE TREMENDOUS SPREAD AMONGST THE MEMBERS WITH REGARDS TO THE
EXACT BEHAVIOR OF THE SOUTHWESTERN CONUS UPPER LOW. BECAUSE OF THE
UNCERTAINTY...NO MAJOR CHANGES WERE MADE TO THE FORECAST DURING THIS
PERIOD.
KJB
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 08Z...
* WIND DIRECTION THIS A.M. AS WARM FRONT MOVES TO MDW AND ORD
AREA 14-15Z.
* WIND SPEED AND GUSTS THIS AFTERNOON FOLLOWING COLD FRONT
PASSAGE.
* IFR CIGS TIL MID MORNING LIFTING TO MVFR WITH WARM FRONT
PASSAGE.
* -RA TO PREVAIL INTO LATE MORNING.
TRS
//DISCUSSION...UPDATED 00Z...
MESSY CONDITIONS TO CONTINUE THROUGH THE EVENING AND OVERNIGHT.
A QUASI-STATIONARY FRONT REMAINS JUST SOUTH OF THE TERMINALS...
THROUGH NRN INDIANA TO CNTRL MISSOURI. THE MAIN CONCERN FOR THE
EVENING AND OVERNIGHT WILL FOCUS ON HOW SFC WAVES RIPPLE ALONG THE
FRONT AND WHETHER OR NOT THE FRONT WILL PUSH NORTH AT SOME POINT
OVERNIGHT OR EARLY TOMORROW MORNING. THE FORECAST MODELS ARE NOT
MUCH HELP AS SOME SOLUTIONS SUGGEST THAT THE FRONT WILL PUSH NORTH
OF THE ORD/MDW/GYY TERMINALS DURG THE EARLY MORNING HOURS...WHILE
OTHER SOLUTIONS KEEP THE FRONT TO THE SOUTH. THE FRONTAL POSITION
WILL HAVE A MAJOR IMPACT ON THE CIG/VIS/WX CONDITIONS AT THE
TERMINALS. WHILE THE FRONT IS TO THE SOUTH...CONDITIONS WILL
REMAIN FAIRLY CONSISTENT WITH THE CURRENT CONDITIONS WITH CIGS
ARND 5-6 HUNDRED FEET...WITH THE EXCEPTION OF RFD WHICH IS A
LITTLE FARTHER BACK IN COOLER/DRIER AIR AND CIGS SHOULD REMAIN
ARND 1000FT. MORE PERSISTENT RAIN HAS MOVED BACK OVER THE ERN
TERMINALS AND SHOULD CONTINUE THROUGH THE NIGHT.
FOR THE EARLY MORNING HOURS...WILL NOT MAKE TOO MUCH CHANGE AT
THIS TIME...ANTICIPATING THAT THE FRONT MAY PUSH NORTH OF THE
ORD/MDW/DPA/GYY TERMINALS DURG THE PRE-DAWN HOURS. THIS WOULD
ALLOW WINDS TO VEER FROM NELY TO SOUTHERLY FOR A FEW HOURS...AND
PUT THIS AREA INTO WARM SECTOR AIR. THIS WILL BE THE PERIOD OF
TIME WHERE CIGS/VIS WILL HAVE THE GREATEST OPPORTUNITY TO IMPROVE
TO VFR...BUT AS WINDS VEER THROUGH EASTERLY...THEY COULD DROP TO
LIFR...THEN IMPROVE TO VFR AS WINDS BECOME SOUTHERLY.
HOWEVER...THIS WOULD ALSO BE THE PERIOD OF TIME WHEN THERE WILL BE
SOME POTENTIAL FOR TS INVOF THE TERMINALS. GIVEN THE UNCERTAINTY
AT THIS POINT...WILL KEEP ANY MENTION OF TS OUT OF THE TAFS.
THE MAIN CONCERN FOR TOMORROW WILL SHIFT BACK TO WIND SPEEDS. WHEN
THE MAIN UPPER TROUGH AND SFC SYSTEM FINALLY PUSH EAST OF THE
AREA...STRONG COLD ADVECTION WILL SET UP AS WINDS CONTINUE TO VEER
WESTERLY AND INCREASE. EXPECT THAT WINDS SHOULD GUST TO 25 KT BY
LATE MORNING AND APPROACH 30KT IN THE AFTERNOON.
KREIN
//ORD AND MDW CONFIDENCE...UPDATED 06Z...
* LOW CONFIDENCE IN WIND DIRECTION THROUGH LATE MORNING.
* MEDIUM CONFIDENCE IN GUSTY WINDS FM SW-W THIS AFTERNOON.
* MEDIUM IN CIGS REMAINING IFR TIL PREDAWN THEN MVFR FROM MID-
MORNING ON.
TRS
//OUTLOOK FOR ORD/MDW FOR 12Z THURSDAY-12Z WEDNESDAY...UPDATED 00Z...
THU...SLIGHT CHANCE -SHSN AND MVFR CIGS EARLY. OTRW...VFR.
FRI...VFR. WX NIL.
SAT...VFR. WX NIL.
SUN...CHANCE SHRA. CHANCE MVFR CIGS EARLY. OTRW...VFR.
MON...VFR. CHC SHRA.
KREIN
&&
.MARINE...
403 PM CST
GUSTY WINDS HAVE BEEN REPORTED ACROSS THE SOUTHERN HALF OF THE
LAKE TODAY AS A FAIRLY TIGHT PRESSURE GRADIENT HAS ESTABLISHED
ITSELF IN THIS AREA...WHILE QUIETER CONDITIONS HAVE BEEN REPORTED
OVER THE NORTHERN HALF DUE TO A RIDGE OF HIGH PRESSURE. THE TROUGH
OF LOW PRESSURE RESPONSIBLE FOR THIS TIGHTER GRADIENT WILL TRACK
FROM THE MID MISSISSIPPI VALLEY TONIGHT AND REACH SOUTHERN LAKE
MICHIGAN...AS THIS HIGH SHIFTS NORTH. WITH THIS OCCURRING...EXPECT
WINDS AND WAVES TO BE ON THE INCREASE ALL ACROSS THE LAKE TONIGHT
INTO WEDNESDAY WITH EVEN SOME VARIABILITY IN WIND DIRECTION
POSSIBLE. THIS VARIABILITY IS DUE TO A LINGERING BOUNDARY THAT
THIS AREA OF LOW PRESSURE WILL BE RIDING ALONG TONIGHT. EXPECT
WINDS TO REALLY RAMP UP LATE TONIGHT ACROSS THE NORTHERN HALF WITH
GALES EXPECTED...THEN EXPECT THE SOUTHERN HALF TO INCREASE LATER
WEDNESDAY MORNING. AS THIS LOW CONTINUES INTO MICHIGAN ON
WEDNESDAY...ALL WINDS ACROSS THE LAKE WILL BE MORE WESTERLY WITH
GALES CONTINUING INTO WEDNESDAY EVENING. THEN AS THE PRESSURE
GRADIENT WEAKENS WITH A DEPARTING LOW...GALES WILL BE DIMINISHING
FIRST ACROSS THE SOUTHERN HALF...BUT THEN LATER WEDNESDAY NIGHT
FOR THE NORTHERN HALF. AS A FAIRLY PROGRESSIVE WEATHER PATTERN IS
FORECAST THROUGH THE END OF THE WORK WEEK...HIGHER WINDS AND WAVES
ARE POSSIBLE ONCE AGAIN LATER THIS WEEK.
RODRIGUEZ
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
LMZ868 UNTIL 3 AM THURSDAY.
GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ777-LMZ779-
LMZ870-LMZ872-LMZ874-LMZ876-LMZ878...9 AM WEDNESDAY TO 9 PM
WEDNESDAY.
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.
&&
$$
