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 22Z...
* WIND DIRECTION AND SPEED REMAINDER OF THE AFTERNOON AND EVENING.
* IFR CIGS AND VSBYS WITH OCNL PERIODS OF LIFR POSSIBLE.
KREIN
//DISCUSSION...UPDATED 18Z...
A BIG MESS FOR AVIATION CONTINUES INTO THE AFTERNOON. CURRENT
OBSERVATIONS AROUND THE NEIGHBORHOOD VARY FROM VFR TO LIFR. IN
TERMS OF FLIGHT CATEGORIES FOR ORD/MDW TODAY...IFR WOULD APPEAR TO
BE THE MOST LIKELY TREND...THOUGH NOT SURE IF THIS WILL BE DUE
TO CIGS OR VSBYS OR BOTH. PERIODS OF MVFR ARE ALSO LIKELY.
THE HEAVIER RAIN WILL BE TAPERING OFF EARLY THIS AFTERNOON BEFORE
PICKING BACK UP SOMETIME THIS EVENING ALONG THE FRONTAL ZONE THAT
REMAINS DRAPED OVER THE AREA. THE MAIN AREA OF LOW PRESSURE IS
APPROACHING FROM NORTHEAST OKLAHOMA...MOVING ALONG THIS
FRONT...AND WILL CROSS DIRECTLY OVERHEAD AROUND SUNRISE TOMORROW
MORNING. AFTER THE LOW PASSES...RAINS AGAIN TAPER OFF BUT GUSTY
WEST WINDS WILL DEVELOP TOMORROW AFTERNOON.
LENNING
//ORD AND MDW CONFIDENCE...UPDATED 22Z...
* MEDIUM CONFIDENCE IN WIND DIRECTION...GENERALLY FROM 360 TO 030
UNTIL 01Z THEN BECMG 030 TO 060 AFTER 01Z.
* MEDIUM CONFIDENCE IN WIND SPEED...GENERALLY AROUND 10 KTS
ALTHOUGH THERE ARE SOME HIGHER GUSTS JUST NORTH OF THE AREA
FARTHER AWAY FROM THE FRONT.
* LOW CONFIDENCE IN EXACT CIGS AND VSBYS THRU THE REMAINDER OF THE
AFTERNOON...BUT MEDIUM TO HIGH CONFIDENCE OF IFR AND
OCCASIONAL LIFR.
* LOW CONFIDENCE IN PRECIP TRENDS TONIGHT AND TOMORROW.
KREIN
//OUTLOOK FOR ORD/MDW FOR 00Z THURSDAY-12Z TUESDAY...UPDATED 12Z...
WED NIGHT...VFR. WX NIL.
THU...VFR. WX NIL.
FRI...VFR. WX NIL.
SAT...VFR. WX NIL.
SUN...VFR. SLGT CHC -SHRA.
MON...VFR. CHC -SHRA.
TRS
&&
.MARINE...
320 AM CST
A BIT OF A TRICKY FORECAST TODAY...SPECIFICALLY REGARDING WINDS.
WINDS HAVE BEGUN TO PICK UP SOME THIS MORNING AS LOW PRESSURE
DEEPENS OVER THE OZARKS AND A WARM FRONT LIFTS NORTH ACROSS INDIANA
AND ILLINOIS. TO THE NORTH OF THE FRONT...EXPECT WINDS TO INCREASE
OUT OF THE NORTHEAST...INTO THE 20 TO 25 KT RANGE FOR SOUTHERN
PORTIONS OF LAKE MICHIGAN. A SMALL CRAFT ADVISORY HAS ALREADY BEEN
ISSUED FOR THE ILLINOIS NEARSHORE WATERS. TRICKY PART WILL BE WIND
TRENDS THIS AFTERNOON INTO THE EVENING AS THE FRONTAL TROUGH MOVES
NORTH OVER THE LAKE. WINDS WITHIN THIS ZONE WILL DROP OFF QUITE A
BIT...LIKELY INTO THE 10 TO 15 KT RANGE...AND WAVES WILL LIKEWISE
DROP BELOW CRITERIA FOR SMALL CRAFT ADVISORY. IT APPEARS THERE COULD
BE AROUND A SHORT WINDOW WHERE WE WILL BE BELOW CRITERIA...BUT WITH
UNCERTAINTY IN TIMING HOW MUCH WINDS WILL DIMINISH...WILL NOT MAKE
CHANGES TO HEADLINE AT THIS TIME. BY LATE TONIGHT...WINDS WILL ONCE
AGAIN INCREASE AS THE BOUNDARY LIFTS NORTH...WITH STRONG SOUTH TO
SOUTH-SOUTHWEST WINDS EXPECTED. THE LOW WILL CONTINUE TO DEEPEN AS
IT LIFTS INTO THE NORTHERN HALF OF THE LAKE BY WEDNESDAY AFTERNOON.
GALE FORCE WINDS ARE EXPECTED TO BEGIN WEDNESDAY AFTERNOON FOR THE
SOUTH HALF OF THE LAKE...AND AS A TRAILING COLD FRONT SWINGS ACROSS
THE LAKE WEDNESDAY EVENING...EXPECT GALES TO OCCUR ACROSS THE LAKE.
GALES SHOULD LET UP BY THURSDAY MORNING...BUT EXPECT BREEZY
CONDITIONS TO PERSIST ACROSS THE LAKE AS A MODEST PRESSURE GRADIENT
REMAINS IN PLACE THROUGH THE REMAINDER OF THE WEEK AND INTO THE
WEEKEND. BMD
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
LMZ868...3 AM WEDNESDAY TO 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 NORTHERLY IS UNTIL 10 PM WEDNESDAY.
SMALL CRAFT ADVISORY...LMZ742-LMZ743-LMZ744...10 PM TUESDAY TO
10 PM WEDNESDAY.
SMALL CRAFT ADVISORY...LMZ745...10 PM TUESDAY TO 4 AM THURSDAY.
&&
$$
