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 09Z...
* SCT -SHRA AND LOWER END VFR CIGS THROUGH MID DAY SUNDAY.
KREIN
//DISCUSSION...UPDATED 06Z...
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 DAYBREAK. FOLLOWING
THE PASSAGE OF THE SFC RIDGE...ANOTHER MID LEVEL IMPULSE WILL
TRACK OVER THE TERMINAL AREA BRING ANOTHER CHANCE FOR SCT -SHRA.
AS LOW LEVELS ARE STILL VERY DRY...ANY PCPN WILL BE SCT AND
LIGHT...LIKELY NOT OBSTRUCTING VIS OR EVEN WETTING RUNWAYS...AND
CIGS SHOULD NOT DROP BELOW 6KFT. BY ARND 18Z...THE MID LEVEL
IMPULSE WILL MOVE OFF TO THE EAST...ALLOWING FOR LOW CLOUD COVER
TO SCATTER OUT...WHILE SFC WINDS 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 09Z...
* MEDIUM CONFIDENCE IN PRECIP FORECAST THRU SUNDAY MORNING.
* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.
KREIN
//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...
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...1 PM SUNDAY TO 3 PM
MONDAY.
GALE WARNING...LMZ366-LMZ565-LMZ567-LMZ669-LMZ671-LMZ868-LMZ870-
LMZ872...1 PM SUNDAY TO 9 AM MONDAY.
&&
$$
