454 PM CST
STRONGEST PRESSURE RISES ARE OVER NE IL RIGHT NOW...PLACING
STRONGEST WINDS NORTHEAST OF OUR AREA NOW. GIVEN ALL OBSERVATION
SITES ARE NOW WELL BELOW CRITERIA AND ONLY EXPECTED TO SUBSIDE
FURTHER HAVE ELECTED TO KILL THE NPW A BIT EARLY. WORKING TO
UPDATE GRIDS NOW AND WILL HAVE NEW GRIDS AND ZFP WILL BE OUT
SHORTLY.
IZZI
//PREV DISCUSSION...
330 PM CST
THE MAIN ISSUE THIS AFTERNOON HAS BEEN THE WINDS. STRONG
ISALLOBARIC PRESSURE RISES IN EXCESS OF 5MB/3HR AND GOOD COLD AIR
ADVECTION HAVE BEEN OCCURRING ACROSS PORTIONS OF NORTHERN ILLINOIS IN
THE WAKE OF THE SURFACE LOW. THIS HAS LEAD TO SOME PERIOD OF ADVISORY
CRITERIA WINDS ACROSS PORTIONS OF THE AREA THIS AFTERNOON. I EXPECT
THE WINDS TO ABATE LATE THIS AFTERNOON AND THIS EVENING FOLLOWING
THIS PRESSURE AND CAA SURGE.
IN ADDITION TO THE WINDS. A FEW AREAS ACROSS NORTH CENTRAL IL
EXPERIENCED THEIR FIRST SNOWFALL OF THE SEASON. THIS WAS ASSOCIATED
WITH AN AREA OF MID LEVEL FRONTOGENESIS WITHIN A WELL DEFINED
DEFORMATION ZONE ALONG THE NORTHWEST QUADRANT OF THE SURFACE LOW.
THE SNOW BAND WAS HEAVY ENOUGH TO RESULT IN SOME MINOR ACCUMULATIONS
AROUND 1 TO 3 TENTHS OF AN INCH ACROSS PORTIONS OF NORTH CENTRAL
ILLINOIS.
HOWEVER...THIS SYSTEM WILL QUICKLY LOSS IT GRIP ON THE AREA THIS
EVENING AS IT CONTINUES TO LIFT NORTHEASTWARD ACROSS THE UPPER GREAT
LAKES. THE NEXT SYSTEM OF INTEREST IS CURRENTLY EVIDENT IN THE WATER
VAPOR IMAGERY DIGGING SOUTH ACROSS SOUTHERN CANADA AND THE DAKOTAS.
THIS MID LEVEL DISTURBANCE IS FORECAST TO RAPIDLY DIG SOUTHWARD
ACROSS THE MID MISSISSIPPI RIVER VALLEY AND WESTERN GREAT LAKES ON
THURSDAY. THIS WILL HELP USHER IN EVEN COLDER AIR ACROSS THE REGION.
THIS COLDER AIR MASS SHOULD HELP STEEPEN THE LOW LEVEL LAPSE RATES
ACROSS THE AREA. THE COMBINATION THESE STEEPER LAPSE RATES AND THE
PRESENCE OF SOME WEAK LARGE SCALE FORCING FOR ASCENT WILL HELP SET
UP SOME SCATTERED LIGHT RAIN OR SNOW SHOWERS DURING THE DAY ON
THURSDAY ACROSS NORTHERN ILLINOIS AND NORTHWESTERN INDIANA. THERE
COULD ALSO BE SOME LAKE ENHANCEMENT TO THE SHOWERS...ESPECIALLY
ACROSS LOWER MICHIGAN SOUTHWARD INTO INDIANA.
A DECENT WARMING TREND LOOKS TO SET UP BY THE START OF THE WEEKEND
AS SOUTHWEST FLOW COMMENCES ACROSS THE AREA COMPLEMENTS OF A SURFACE
HIGH MOVING ACROSS THE SOUTHEASTERN CONUS. THIS COULD PUT
TEMPERATURES BACK INTO THE 50S TO NEAR 60 FOR SATURDAY AND SUNDAY.
FINALLY BY EARLY NEXT WEEK IT APPEARS THE WEATHER PATTERN ACROSS
NORTH AMERICA WILL REMAIN ACTIVE. UPPER LEVEL RIDGING ACROSS THE
PACIFIC REGION WILL SET UP A STRONG JET ACROSS THE NORTHEASTERN
PACIFIC. THIS WILL ENCOURAGE SEVERAL DISTURBANCES ACROSS THE
NORTHERN LATITUDES OF THE PACIFIC TO EJECT EASTWARD ATOP THIS
PACIFIC RIDGE AND THEN DIG SOUTHEASTWARD ACROSS THE WESTERN CONUS.
THIS LOOKS TO SET UP NEGATIVE HEIGHT ANOMALIES ACROSS MUCH OF THE
CENTRAL AND WESTERN CONUS BY EARLY NEXT WEEK. THIS WEATHER PATTERN
WOULD PLACE NORTHERN ILLINOIS INTO A SOUTHWEST FLOW PATTERN
ALOFT...POTENTIALLY SETTING THE STAGE FOR ANOTHER GOOD PRECIPITATION
EVENT. HOWEVER...ALTHOUGH THERE IS DECENT AGREEMENT AMONG THE
VARIOUS MODEL GUIDANCE WITH THE LARGER SCALE PATTERN...THERE ARE
STILL SOME DIFFERENCES APPARENT WITH THE SMALLER SCALE DETAILS IN
THE EXTENDED. THERE COULD BE A WET PERIOD EARLY NEXT WEEK AS A
SIGNIFICANT DISTURBANCE ACROSS THE SOUTHWESTERN CONUS EJECTS EASTWARD
ACROSS THE CENTRAL CONUS. BUT CONFIDENCE REMAINS ON THE LOW SIDE
REGARDING THE SPECIFICS OF TIMING OF BEST CHANCES OF RAIN EARLY NEXT
WEEK.
KJB
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 08Z...
* STRATOCUMULUS CEILING LOWERING TO HIGH END MVFR DURING THE DAY.
* W WINDS GUST 20-25KT DURING AFTERNOON.
* SCATTERED -SHSN MID MORNING THROUGH MID AFTERNOON.
TRS
//DISCUSSION...UPDATED 06Z...
AN UPPER LEVEL DISTURBANCE OVER MN WILL MOVE SOUTHEAST ACROSS THE
AREA THURSDAY MORNING INTO THURSDAY AFTERNOON. THE LEADING CLOUD
COVER WITH THIS WAVE IS GENERALLY VFR IN THE 3-5KFT RANGE AND
EXPECT IT TO ARRIVE PRIOR TO SUNRISE. EVENTUALLY EXPECT MVFR CIGS
TO MOVE ACROSS THE AREA BY MID/LATE THURSDAY MORNING. HOWEVER...
STILL SOME UNCERTAINTY AS TO HOW LONG THE MVFR CIGS WILL PERSIST
BUT FOR NOW...GIVEN CURRENT OBSERVATIONS WILL CONTINUE WITH MVFR
CIGS THROUGH MUCH OF THE DAY...BUT COULD BE IMPROVEMENT TO LOW VFR
BY MID AFTERNOON. PRECIP POTENTIAL APPEARS RATHER LIMITED IN TIME
AND OPTED TO INCLUDED JUST A VCSH FOR A 3-4 HR TIME PERIOD THOUGH
MAIN PRECIP TYPE APPEARS TO BE LIGHT SNOW.
WEST/SOUTHWEST WINDS HAVE DIMINISHED TO 10 KTS OR SO WITH A FEW
LOCATIONS REPORTING HIGHER GUSTS. AS CLOUDS COME BACK ACROSS THE
AREA OVERNIGHT...EXPECT GUSTS TO BECOME PREVAILING AGAIN IN THE
15-20KT RANGE BY MID MORNING AND THEN 20-25KTS BY LATE MORNING AND
THEN INTO THE AFTERNOON. WINDS SHOULD QUICKLY DIMINISH WITH SUNSET
THURSDAY WITH CLEARING SKIES OVERNIGHT AS THE UPPER WAVE MOVES
SOUTHEAST OF THE AREA. CMS
//ORD AND MDW CONFIDENCE...UPDATED 08Z...
* HIGH CONFIDENCE SKC TIL PREDAWN BCMG BKN-OVC STRATOCU.
* HIGH CONFIDENCE W WIND GUST 20-25KT MIDDAY AND AFTERNOON.
* MEDIUM CONFIDENCE CIGS LOWER INTO MVFR MID-LATE MORNING.
* MEDIUM CONFIDENCE -SHSN OCCURRING.
* MEDIUM CONFIDENCE ANY -SHSN WILL NOT BE OPERATIONALLY
SIGNIFICANT.
TRS
//OUTLOOK FOR ORD/MDW FOR 12Z FRIDAY-12Z WEDNESDAY...UPDATED 00Z...
FRIDAY...BREEZY. SOUTHWEST WINDS GUSTING 20+ KTS. VFR.
SATURDAY...VFR.
SUNDAY...WINDY. SOUTHWEST WINDS GUSTING 30+ KTS. VFR.
MONDAY...CHANCE OF RAIN. MVFR POSSIBLE.
TUESDAY...SLIGHT CHANCE OF RAIN. CMS
&&
.MARINE...
330 PM CST
A DEEPENING LOW PRESSURE SYSTEM THAT MOVED OVER THE LAKE TODAY WAS
LOCATED NEAR LUDINGTON THIS AFTERNOON AND WILL CONTINUE MOVING
NORTHEAST TOWARD JAMES BAY OVERNIGHT. WINDS IN THE WAKE OF THIS
LOW HAVE BEEN GUSTING TO 40 KTS OR MORE...ESPECIALLY AT THE HIGHER
PLATFORMS. EXTENDED THE EXISTING HEADLINES TO ACCOUNT FOR THESE
STRONGER GUSTS PERSISTING INTO THE EARLY MORNING PERIOD. ONE OR
TWO PLATFORMS ON THE MICHIGAN SIDE OF THE LAKE ALSO REPORTED GUSTS
INTO THE VERY LOW STORM FORCE CATEGORY...BUT SHIP OBSERVATIONS AND
LOWER PLATFORMS ARE TOPPING OUT AT THE GALE FORCE RANGE. WINDS
ACROSS THE LAKE VARY QUITE A BIT IN DIRECTION THIS AFTERNOON BUT
WILL BECOME UNIFORMLY WEST OVERNIGHT. WEST FLOW THEN PERSISTS INTO
FRIDAY MORNING BEFORE WINDS BACK SOUTH AHEAD OF A NEW LOW PRESSURE
SYSTEM APPROACHING LAKE SUPERIOR. SOUTH TO SOUTHWEST WINDS
CONTINUE THROUGH THE WEEKEND AS THE LOW PASSES NORTH OF THE LAKES.
LENNING
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
LMZ874-LMZ876-LMZ878 UNTIL 3 AM THURSDAY.
GALE WARNING...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
LMZ868 UNTIL 9 AM THURSDAY.
&&
$$
