330 AM CDT
SHOWERS LAST EVENING AND OVERNIGHT HAVE REMAINED MAINLY JUST
NORTH OF THE LOCAL FORECAST AREA...THOUGH A FEW HAD CLIPPED FAR
NORTH CENTRAL AND NORTHEAST IL AS WELL AS FAR NORTHERN IN. EARLY
THIS MORNING SHOWERS WERE MORE NUMEROUS OVER EAST CENTRAL
WI...ALONG/NEAR THE MN-IA BORDER AND FROM WEST CENTRAL IA BACK
ACROSS SOUTHERN SD. THE SHOWERS...ESPECIALLY THOSE MOVING INTO THE
WESTERN GREAT LAKES...ARE WELL AHEAD OF THE ACTUAL SHORT WAVE
TROUGH WHICH AT 07Z EXTENDED FROM OVER LAKE WINNIPEG SOUTHWEST TO
FAR EASTERN MT.
WHILE THE SHORT WAVE TROUGH AXIS WAS STILL WELL UPSTREAM THE WARM
AIR ADVECTION HAD SPREAD FAR OUT AHEAD OF THE TROUGH. PROFILER
AND 88D NETWORKS INDICATING 850HPA WEST-SOUTHWEST FLOW OF 25-35KT
OVER NORTHERN IL INCREASING TO 40-50KT OVER MO...KS AND AND
NORTHERN OK. THIS WARM AIR ADVECTION IS RESULTING IN SIGNIFICANT
ISENTROPIC LIFT OVER THE BAROCLINIC ZONE THAT IS PROGGED TO EXTEND
FROM IA ACROSS NORTHERN IL AND FAR NORTHERN IN AT 12Z.
WITH CONTINUED SIGNIFICANT UPWARD VERTICAL MOTION THIS MORNING
DUE TO THE WARM AIR ADVECTION EXPECT MID LEVELS TO CONTINUE TO
SATURATE OVER THE AREA WHILE A TONGUE OF UPPER 40-LOWER 50
SURFACE DEW POINTS CURRENTLY NOSING NORTHEAST ACROSS THE MID MO
VALLEY QUICKLY SPREADS ACROSS THE MID MS VALLEY INTO NORTHERN IL
HELPING MOISTEN THE LOWER LEVELS. STILL...ONLY EXPECT SOME LIGHT
RAINFALL ACCUMULATIONS DURING THE MORNING BEFORE THE WARM AIR
ADVECTION FORCING AND RESULTING RAIN SHIFTS EAST OVER THE MIDWEST
AND UPPER OH VALLEY BY MIDDAY AS THE SHORT WAVE TROUGH DROPS
ACROSS THE UPPER MIDWEST. WITH THE TROUGH AXIS MOVING ACROSS THE
LOCAL AREA REACHING LAKE MI BY 00Z MON ANTICIPATE CLEARING TO
GRADUALLY SPREAD WNW-ESE ACROSS THE AREA LATER AFTERNOON AND THIS
EVENING IN SUBSIDENCE FOLLOWING IN THE WAKE OF THE SHORT WAVE.
MODELS HAVE CONTINUED THEIR TREND WITH TAKING THE NEXT
SYSTEM...CURRENTLY OVER WA...THAT POTENTIALLY BROUGHT RAIN TO
SOUTHERN PORTIONS OF THE FORECAST AREA LATE MONDAY AND MONDAY
NIGHT ON AN EVEN MORE SOUTHERLY TRACK FR OM THE OZARKS
NORTHEASTWARD JUST SOUTH OF THE OH RIVER MONDAY NIGHT AND TUESDAY.
WITH THE CONTINUED PUSHING SOUTH WITH THIS SYSTEM BY EACH MODEL
RUN HAVE FOLLOWED SUIT AND HAVE REDUCED POPS DURING LATE MONDAY
AND MONDAY NIGHT TO SLIGHT CHANCE AND LOW END CHANCE PERCENTAGES
ACROSS THE FAR SOUTH COUNTIES OF THE FORECAST AREA.
MODELS ALSO CONSISTENT IN THEIR RECENT TREND OF SHARPENING THE
UPPER TROUGH OVER THE REGION TUESDAY WITH A CLOSED UPPER LOW
FORMING BY TUESDAY AFTERNOON OR EVENING. WITH THE UPPER TROUGH
AXIS PROGGED ALONG/NEAR THE MS VALLEY AT 18Z TUE AND MOVING EAST
TO THE IN STATE LINE BY 00Z WED HAVE A SLIGHT CHANCE FOR SHOWERS
IN THE WESTERN COUNTIES...INCREASING TO CHANCE CATEGORY ACROSS
THE EAST DUE TO DEEP CYCLONIC FLOW...POTENTIAL FOR DIURNAL SHOWERS
AND DEVELOPMENT OF A LAKE EFFECT RAIN SHOWER SITUATION FOR THE IL
SHORES AND NORTHWEST IN BY THE END OF THE DAY.
A SMALL EASTERLY COMPONENT TO THE FLOW THROUGH THE LAKE EFFECT
CLOUD LEVEL WEDNESDAY EVENING PUT THE IL SHORE AREA...ESPECIALLY
CHICAGO AND THE SOUTH SIDE...AS WELL AND FAR NORTHWEST IN UNDER
THE GUN FOR LAKE EFFECT SHOWERS. DURING WEDNESDAY NIGHT THE CLOUD
BEARING LAYER WINDS BACK TO NEARLY UNIDIRECTIONAL OUT OF THE
NORTH SO EXPECT A MID LAKE BAND TO BE POINTED AT THE SOUTH END OF
THE LAKE WITH SHOWERS PUSHING INLAND SOUTH ACROSS THE KANKAKEE
RIVER.
BY THURSDAY MORNING THE THREAT OF LAKE EFFECT WILL HAVE SHIFTED
EAST OF THE FORECAST AREA AND DIMINISHED AS WINDS ARE TO BACK
FURTHER TO MORE NORTHWESTERLY AND MID LEVEL WARM IN RESPONSE TO
RISING HEIGHTS ALOFT AS THE UPPER LOW MOVES FURTHER AWAY OFF TO
THE NORTHEAST ACROSS NY AND THE UPPER ST. LAWRENCE VALLEY.
AFTER TEMPERATURES AROUND CLIMATOLOGICAL NORMALS TODAY THINGS TURN
COOLER FOR MID WEEK AS COOL AIR THAT HAS BEEN GRADUALLY SPREADING
SOUTH ACROSS MANITOBA AND ONTARIO MAKE FURTHER PROGRESS SOUTH
ACROSS THE UPPER MIDWEST AND UPPER GREAT LAKES TODAY AND TONIGHT
FOLLOWING THE PASSAGE OF THE SHORT WAVE THAT WILL BRING SHOWERS TO
THE AREA THIS MORNING. BY MIDDAY TUESDAY LOW AND MID LEVEL FLOW
VEERS TO OUT OF THE NORTH...ADVECTING THE COOL AIR EVEN DEEPER
ACROSS THE REGION. HIGHS TUESDAY THROUGH THURSDAY ARE ONLY
EXPECTED TO BE IN THE LOWER AND MID 50S WITH NIGHT TIME LOWS OUT
OF THE CHICAGO URBAN HEAT ISLAND DROPPING INTO THE MID AND UPPER
30S. THE END OF THE WEEK AND THE WEEKEND LOOK TO BE DRY WITH
MODERATING TEMPERATURES AS THE UPPER FLOW FLATTENS AND BECOMES
WEST-NORTHWEST. THIS WILL RESULT IN THE CANADIAN AIR MASS BEING
REPLACED BY A MILDER PACIFIC AIR MASS.
TRS
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 15Z...
* ENDING OF LIGHT RAIN BY MID-DAY.
* WEST-NORTHWEST WINDS INCREASING AND GUSTING ABOVE 20 KT THIS
AFTERNOON.
RATZER
//DISCUSSION...UPDATED 15Z...
BAND OF MAINLY VFR MID-LEVEL CLOUDS AND LIGHT RAIN REMAINS ACROSS
FAR NORTHERN IL/NORTHWEST IND AT 15Z...IN ASSOCIATION WITH A
MID-LEVEL DISTURBANCE AND ELEVATED FRONTAL ZONE. TIMING OF
TRAILING EDGE OF LIGHT PRECIP WOULD MOVE RAIN LARGELY SOUTH/EAST
OF TERMINALS BY NOON...AND LATEST MODEL GUIDANCE IN GENERAL
AGREEMENT AS DRIER LOW AND MID LEVEL AIR MOVES IN FROM THE
NORTHWEST DURING THE AFTERNOON. THIS SHOULD ALLOW EROSION OF VFR
CLOUDS FROM THE NORTHWEST.
SURFACE TROUGH/WEAK COLD FRONT MOVING ACROSS CHICAGO TERMINALS AT
THIS TIME...WITH LIGHT AND VARIABLE WINDS BECOMING WEST-NORTHWEST
BEHIND THE TROUGH. GRADIENT WILL TIGHTEN THIS AFTERNOON AS THE
FRONTAL TROUGH MOVES OFF TO THE EAST...AND FORECAST SOUNDINGS
DEPICT DEEP MIXED LAYER DEVELOPING TO AROUND 800 MB/5500 FT. THIS
SUGGESTS STRONGER WIND GUSTS MAY DEVELOP...UP TO 25 KTS OR SO
DURING THE MID/LATE AFTERNOON HOURS.
RATZER
PREVIOUS DISCUSSION FROM 12Z...
BKN-OVC VFR DECK AT 8KFT-10KFT WILL REMAIN OVER THE TERMINALS
THROUGH ARND NOON SUNDAY. A WEAK SFC RIDGE MOVING THROUGH NRN IL
WILL ALLOW WINDS TO BECOME LGT/VRBL THROUGH ARND 14Z. FOLLOWING
THE PASSAGE OF THE SFC RIDGE...ANOTHER MID LEVEL IMPULSE WILL
TRACK OVER THE TERMINAL AREA BRING ANOTHER CHANCE FOR -RA. THE
AREA OF RAIN IS MOVING VERY QUICKLY AND SHOULD BE INVOF THE
TERMINALS BY ISSUANCE TIME. AS LOW LEVELS ARE STILL RATHER
DRY...ANY PCPN WILL BE PATCHY AND LIGHT...LIKELY NOT OBSTRUCTING
VIS. SOME SMALL AREAS OF MODERATE RAIN HAVE BEEN REPORTED OVER
NERN IOWA AND NWRN IL...AND NOW ANTICIPATE THAT THERE MAY BE BRIEF
PERIODS OF WETTING RAIN AT THE TERMINALS. HOWEVER...STILL DO NOT
EXPECT CIGS TO DROP BELOW 5-6KFT. BY ARND 14Z-15Z...THE MID LEVEL
IMPULSE WILL QUICKLY MOVE OFF TO THE EAST...ALLOWING FOR LOW
CLOUD COVER TO SCATTER OUT...WHILE SFC WINDS TO BECOME NWLY TO WLY
AND INCREASE TO 10-15KT...WITH OCNL GUSTS TO 20KT. GUSTINESS WILL
SUBSIDE AT SUNSET AND THE REMAINDER OF THE PERIOD SHOULD BE QUIET.
KREIN
//ORD AND MDW CONFIDENCE...UPDATED 15Z...
* HIGH CONFIDENCE ALL ELEMENTS THROUGH THIS EVENING.
RATZER
//OUTLOOK FOR ORD/MDW FOR 12Z MONDAY-12Z SATURDAY...UPDATED 00Z...
MONDAY...VFR.
TUESDAY...CHC SHRA. MVFR CIGS POSSIBLE.
WEDNESDAY THROUGH FRIDAY...VFR.
IZZI
&&
.MARINE...UPDATED 1100 AM CDT DISCUSSION
FOR THE ILLINOIS AND INDIANA NEAR SHORES...ISSUED A SMALL CRAFT
ADVISORY STARTING 400 PM THIS AFTERNOON. ONCE CLOUDS CLEAR THIS
AFTERNOON...COINCIDENT WITH GOOD PUSH OF COOL AIR
ALOFT...DEEP MIXING AND STEEPENING LOW LEVEL LAPSE RATES WILL
ALLOW WESTERLY WINDS TO RAMP UP QUICKLY THIS AFTERNOON...WITH
GUSTS TO AROUND 25 KT. WINDS HAZARDOUS TO SMALL CRAFT WILL
CONTINUE FOR THE ENTIRE NEAR SHORE THROUGH MID AFTERNOON
MONDAY...BUT THIS TIMING MAY BE REFINED. WESTERLY WINDS WILL BUILD
WAVES TO SMALL CRAFT CRITERIA OFF OF EASTERN LAKE AND PORTER
COUNTY INDIANA...AND THEY WILL BE SLOW TO SUBSIDE. WITH ABOVE
THOUGHTS IN MIND...SMALL CRAFT ADVISORY FROM WINTHROP HARBOR TO
GARY INDIANA CURRENTLY RUNS THROUGH 400 PM CDT MONDAY...WHILE
SMALL CRAFT ADVISORY FROM GARY TO MICHIGAN CITY INDIANA CURRENTLY
RUNS THROUGH 400 AM CDT TUESDAY. AGAIN...IT IS POSSIBLE THESE END
TIMES WILL CHANGE A BIT WITH SUBSEQUENT UPDATES.
RC
FROM 320 AM CDT
DEEP LOW PRESSURE WILL MEANDER AROUND THE JAMES BAY AREA OF ONTARIO
THROUGH MONDAY NIGHT WHILE SLOWLY. COMBINED WITH HIGH PRESSURE OVER
THE NORTHERN PLAINS...A STRONG WESTERLY GRADIENT WILL BE MAINTAINED
ACROSS LAKE MICHIGAN. THE STRONGEST GRADIENT WILL BE OVER THE
NORTHERN TWO THIRDS OF THE LAKE AND A REINFORCING PUSH OF COOLER AIR
WRAPPING AROUND THE LOW WILL CAUSE AN INCREASE IN WIND SPEEDS OVER
THE LAKE. WITH THE STRONGEST GRADIENT OVER THE NORTHERN PORTIONS OF
THE LAKE...GALES WILL LIKELY AGAIN FROM THIS AFTERNOON THROUGH
MONDAY AFTERNOON. THE FAR SOUTHERN PORTIONS OF THE LAKE SHOULD BE
SPARED FROM THE GALE FORCE WINDS AS THE PRESSURE GRADIENT WILL BE
WEAKER...BUT WINDS SHOULD STILL REACH AROUND 30 KT TONIGHT. THE LOW
WILL FINALLY WEAKEN AND RAPIDLY LIFT OUT ACROSS QUEBEC ON TUESDAY.
STRONG HIGH PRESSURE WILL BUILD OUT OF THE CANADIAN PRAIRIES AND
NORTHERN PLAINS MID-WEEK...WHICH WILL HELP MAINTAIN BRISK NORTHERLY
WINDS ACROSS LAKE MICHIGAN THROUGH THE END OF THE FORECAST PERIOD.
KREIN
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ261-LMZ362-LMZ364-LMZ563 UNTIL 3 PM MONDAY.
GALE WARNING...LMZ366-LMZ565-LMZ567-LMZ669-LMZ671-LMZ868-LMZ870-
LMZ872 UNTIL 9 AM MONDAY.
SMALL CRAFT ADVISORY...LMZ744-LMZ745...4 PM SUNDAY TO 4 AM
TUESDAY.
SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743...4 PM SUNDAY
TO 4 PM MONDAY.
&&
$$
