1228 PM CDT
UPDATED GRIDS TO LOWER POPS OVER ALL BUT FAR SE COUNTIES FOR THIS
AFTERNOON. RADAR TRENDS...LATEST GUIDANCE AND PRESENCE OF DRY
AIRMASS SHOULD KEEP MOST OF THE AFTERNOON DRY.
AFTER EXAMINING 12Z GUIDANCE PLAN TO HOIST A HIGH WIND WATCH FOR
AREAS NEAR THE LAKE AND LAKESHORE FLOOD WATCH WITH THIS
AFTERNOON'S FORECAST. STILL FINE TUNING DETAILS MORE TO COME...
IZZI
//PREV DISCUSSION...
349 AM CDT
THE MAIN FORECAST CONCERN FOR THE MORNING UPDATE WILL FOCUS ON THE
DEVELOPING SYSTEM TO LIFT FROM THE SOUTH AND BRING AN EXTENDED
PERIOD OR WIDESPREAD RAIN TO NORTHERN ILLINOIS AND NORTHWEST INDIANA.
HOWEVER...BEFORE THE RAIN MOVES INTO THE AREA...THE REMAINDER OF THE
NIGHT AND THE EARLY MORNING HOURS WILL BE QUIET. THE MAIN ISSUE HAS
BEEN OVER NORTHERN ILLINOIS WHERE TEMPERATURES HAVE DROPPED INTO THE
UPPER 30S. THE LATEST SATELLITE IMAGERY INDICATES INCREASING CLOUD
COVER OVER THE AREA...SO DO NOT EXPECT TEMPERATURES TO DROP MUCH
LOWER THAN THE CURRENT VALUES. SO...THERE WILL STILL BE THE
POTENTIAL FOR SOME ISOLATED AREAS OF PATCHY FROST THIS MORNING.
FOR THE REST OF TODAY...THE FOCUS OF THE FORECAST WILL SHIFT TO THE
DEVELOPING PCPN SITUATION. AS THE DEEP UPPER LOW THAT HAS BEEN
SITTING OVER THE JAMES BAY AREA LIFTS OUT TO THE EAST THIS
MORNING...A DEEPENING SOUTHERN STREAM SHORTWAVE WILL LIFT FROM THE
LOWER MISSISSIPPI VALLEY AND INTO THE OHIO VALLEY. A STRENGTHENING
BAROCLINIC ZONE JUST NORTH AND WEST OF THE MAIN SFC LOW WILL SHIFT
OVER THE FAR SERN PORTIONS OF THE CWA BY LATE MORNING...SIGNALING
THE BEGINNING OF A WIDESPREAD PCPN EVENT FOR THE AREA. THE TREND OF
THE MODEL GUIDANCE HAS BEEN TO SHIFT THE TRACK OF THE SYSTEM A
LITTLE MORE TO THE WEST...SO HAVE BEEFED UP POPS AND PCPN AMOUNTS
OVER THE AREA. AS THE SYSTEM TRACKS NEWD...A NRN STREAM SHORTWAVE
DROPPING OUT OF THE NRN PLAINS WILL PHASE WITH THE SRN STREAM
LOW...HELPING CARVE OUT A FULL LATITUDE TROUGH OVER THE MISSISSIPPI
VALLEY. AS THIS OCCURS...THE ASSOCIATED PCPN SHIELD WILL SPREAD
FROM SOUTHEAST TO NORTHWEST ACROSS THE CWA...REACHING THE ROCKFORD
AREA BY THIS EVENING. A SERIES OF NRN STREAM SHORTWAVES WILL DROP
OUT OF CANADA...REINFORCING THE UPPER TROUGH AND EVENTUALLY A CLOSED
UPPER LOW WILL DEVELOP OVER THE LOWER OHIO VALLEY BY WEDNESDAY
AFTERNOON. A COMPLICATING FACTOR WITH THIS DEVELOPING SITUATION
WILL BE THE INTERACTION OF A TROPICAL SYSTEM LIFTING OUT OF THE ERN
GULF OF MEXICO. THE MODELS HAVE NOT BEEN VERY CONSISTENT ON THE
EVOLUTION AND INTERACTION OF THIS SYSTEM...WHICH WOULD ADD A BIT OF
UNCERTAINTY TO THE FORECAST.
THE LATEST GUIDANCE SUGGESTS THAT THE MID-LATITUDE AND
TROPICAL-SOURCED SYSTEMS SHOULD MERGE OVER THE UPPER OHIO VALLEY
WITH A DEEP SFC LOW DEVELOPING BY WEDNESDAY MORNING. AT THE SAME
TIME...STRONG HIGH PRESSURE WILL SETTLE OVER SOUTHCENTRAL CANADA.
BETWEEN A 1030MB HIGH TO OUR NORTHWEST AND A 991MB LOW TO OUR
SOUTHEAST...A VERY STRONG NELY-NLY PRESSURE GRADIENT WILL SET
UP...WITH THE STRONGEST GRADIENT FOCUSED OVER LAKE MICHIGAN AND
IL/SERN WI/NWRN INDIANA. WINDS WILL INCREASE RAPIDLY THROUGH THE
DAY WEDNESDAY. IN ADDITIONS TO THE STORM-FORCE WINDS EXPECTED TO
DEVELOP OVER LAKE MICHIGAN ON WEDNESDAY...WIND GUSTS WILL APPROACH
35MPH OVER THE CWA. THE WIND FORECAST WILL REQUIRE CLOSE
EXAMINATION FOR THE NEXT MODEL RUNS SINCE WIND SPEEDS WILL BE
APPROACHING WIND ADVISORY CRITERIA. WILL HOLD OFF ON ISSUING A WIND
ADVISORY AT THIS POINT...BUT IF THE 12Z RUNS AND THE OBSERVED SFC
PATTERN INDICATES GREATER STRENGTHENING OF THE PRESSURE GRADIENT OVER
THE AREA...A WIND ADVISORY MAY BE REQUIRED FOR WEDNESDAY AFTERNOON
THROUGH THURSDAY AFTERNOON.
THE OTHER CONCERN WILL BE FOR RAINFALL AMOUNTS. SINCE THIS SYSTEM
WILL BE VERY DYNAMIC BOTH AT THE SFC AND ALOFT...RELATIVELY HEAVY
RAINFALL AMOUNTS ARE LIKELY. HAVE GENERALLY BUMPED UP POPS AND QPF
OVER THE AREA OVER PREVIOUS FORECASTS. WITH THE ADDED INFLUENCE OF
THE SYSTEM LIFTING OUT OF THE ERN GLFMEX...THE ERN PORTIONS OF THE
CWA SHOULD SEE THE HEAVIEST PCPN AMOUNTS. THE LATEST FORECAST
UPDATE WILL CARRY STORM TOTAL QPF RANGING FROM AROUND A QUARTER INCH
OF RAIN OVER THE I-39 CORRIDOR TO ABOUT 1 INCH OVER CHICAGO AND THE
I-57 CORRIDOR. THE HEAVIEST AMOUNTS SHOULD BE OVER THE NWRN INDIANA
COUNTIES...WHERE STORM TOTAL QPF SHOULD APPROACH 1.5 INCHES. SINCE
THE AREA HAS NOT RECEIVED MUCH RAIN RECENTLY...AREA RIVERS SHOULD
HAVE ADEQUATE CAPACITY TO HANDLE THE RAINFALL...BUT THE WRN PORTIONS
OF THE KANKAKEE RIVE WILL NEED TO BE CLOSELY MONITORED FOR
SIGNIFICANT RISES.
FOR THE LONGER TERM FORECAST PERIOD...THE SYSTEM SHOULD FINALLY
BEGIN TO QUICKLY LIFT OUT TO THE NORTHEAST BY THURSDAY NIGHT AND ALL
PCPN SHOULD FINALLY COME TO AN END OVERNIGHT THURSDAY NIGHT. BY
FRIDAY MORNING...A MUCH COOLER AIRMASS WILL SETTLE OVER THE REGION
AND TEMPERATURES WILL ONCE AGAIN BECOME A CONCERN. THE LATEST
EXTENDED GUIDANCE SUGGESTS THAT TEMPERATURES SHOULD DROP INTO THE
LOWER 30S WEST OF THE FOX VALLEY...WHILE THE REMAINDER OF THE
AREA...AWAY FROM THE LAKE FRONT AND THE HIGHLY URBANIZED AREAS OF
THE CHICAGO METRO AREA SHOULD SEE TEMPERATURES DROP INTO THE MIDDLE
TO UPPER 30S. THIS WOULD MEAN WIDESPREAD FROST FOR THE AREA...AND
TEMPERATURES TO OR JUST BELOW FREEZING. SO...THE GENERAL TREND FOR
THE EXTENDED FORECAST PERIOD...FROM FRIDAY THROUGH MONDAY...SHOULD
SEE TEMPERATURES START OUT AT BELOW NORMAL LEVELS AND MODERATE
THROUGH THE WEEKEND. THE PCPN FORECAST IS A LITTLE MORE UNCERTAIN
DUE TO DIFFERENCES IN HOW THE MODELS HANDLE THE FINER SCALE
DETAILS. SO...WILL CARRY A DRY FORECAST THROUGH THE LATTER PORTIONS
OF THE WEEK AND THE WEEKEND.
KREIN
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 18Z...
* PRECIPITATION CHANCES AND COVERAGE TONIGHT AND ON WEDNESDAY.
* CIG TRENDS TONIGHT AND ON WEDNESDAY.
* TIMING/MAGNITUDE OF STRONG NORTHERLY WIND GUSTS TONIGHT AND
WEDNESDAY.
KJB
//DISCUSSION...UPDATED 18Z...
A STORM SYSTEM ACROSS THE CENTRAL AND LOWER MISSISSIPPI RIVER VALLEY
WILL QUICKLY STRENGTHEN TONIGHT INTO WEDNESDAY AS IT LIFTS NORTH
ACROSS THE OHIO VALLEY. THIS SYSTEM WILL PRODUCE SEVERAL MAJOR
WEATHER IMPACTS ACROSS THE TERMINALS BY EARLY WEDNESDAY MORNING.
THESE CONCERNS INCLUDE: WINDS...CIG AND VIS TRENDS AND TIMING OF
RAINFALL.
STRONG NORTH TO NORTHEAST WINDS WILL QUICKLY DEVELOP DURING THE
EARLY MORNING HOURS AS THE DEEPENING SURFACE LOW PRODUCES A STRONG
PRESSURE GRADIENT ACROSS THE AREA. THE WINDS WILL CONTINUE TO
INCREASE DURING THE DAY AS THE LOW LIFTS NORTHWARD. I EXPECTED
NORTHERLY WINDS AROUND 25 KT WITH GUSTS FROM 35 TO 40 KT DURING
THE AFTERNOON.
CIGS SHOULD FALL INTO THE MVFR CATEGORY TONIGHT. HOWEVER...IFR
CONDITIONS ARE POSSIBLE AS EARLY AS LATE WEDNESDAY AFTERNOON...BUT
MORE LIKELY BY WEDNESDAY EVENING. RAINFALL SHOULD BEGIN TO DEVELOP
ACROSS NORTHEASTERN ILLINOIS LATE TONIGHT AS THE FLOW INCREASES OFF
THE LAKE. IT MAY BE MORE SHOWERY IN NATURE DUE TO SOME LAKE
ENHANCEMENT. HOWEVER...MORE WIDESPREAD RAIN WILL ARRIVE DURING THE
DAY ON WEDNESDAY. IT APPEARS THAT THE BEST CHANCES FOR HEAVY
RAINFALL WILL NOT BE UNTIL LATE WEDNESDAY AFTERNOON AND WEDNESDAY
NIGHT. THIS IS THE TIMING IN WHICH STRONG MID LEVEL FORCING FOR
ASCENT INCREASES IN RESPONSE TO A DEVELOPING TROWAL. BECAUSE OF
THIS...I SCALED BACK ON THE LOWER VISIBILITIES IN RAIN THAT WERE
PREVIOUSLY ADVERTISED EARLY WEDNESDAY MORNING. ANY PROLONGED MVFR OR
LOWER VIS IN RAIN LOOKS TO OCCUR AFTER 20 UTC TOMORROW AFTERNOON.
KJB
//ORD AND MDW CONFIDENCE...UPDATED 18Z...
* LOW TO MEDIUM CONFIDENCE IN PRECIP TIMING/COVERAGE TONIGHT.
* MEDIUM CONFIDENCE IN CIGS DROPPING TO MVFR OVERNIGHT.
* LOW CONFIDENCE ON IFR CIGS ON WEDNESDAY.
* HIGH CONFIDENCE IN WIND GUSTS IN EXCESS OF 30 KT BEGINNING
WEDNESDAY MORNING.
KJB
//OUTLOOK FOR ORD/MDW FOR 00Z THURSDAY-12Z TUESDAY...UPDATED 12Z...
WEDNESDAY NIGHT...SHOWERS LIKELY...IFR POSSIBLE. STRONG WINDS.
THURSDAY...CHANCE OF SHOWERS...IFR POSSIBLE.
FRIDAY THROUGH MONDAY...VFR.
BMD
&&
.MARINE...
252 PM CDT
...NORTH TO NORTHEAST GALES DEVELOPING WEDNESDAY MORNING...
INCREASING TO STORM FORCE ACROSS MUCH OF LAKE MICHIGAN LATER
WEDNESDAY AFTERNOON AND EVENING...
LOW PRESSURE IS BEGINNING TO TAKE SHAPE ACROSS THE SOUTHEASTERN U.S.
AS AN UPPER TROUGH INTENSIFIES AND DIGS INTO THE MISSISSIPPI RIVER
VALLEY. LOW PRESSURE WILL CONSOLIDATE AND INTENSIFY AND MOVE
NORTH ACROSS THE TENNESSEE AND OHIO VALLEYS INTO WEDNESDAY
AFTERNOON. NORTH-NORTHWEST WINDS ACROSS THE LAKE THIS AFTERNOON
WILL TURN NORTH THEN NORTHEASTERLY THIS EVENING AND STEADILY
INCREASE IN SPEED. EXPECT THAT WINDS WILL REACH GALE FORCE
SOMETIME AROUND DAYBREAK ACROSS MUCH OF THE LAKE...ESPECIALLY
SOUTH. THE LOW WILL FURTHER STRENGTHEN TO AROUND 29.6 INCHES AND
APPROACH FT. WAYNE WEDNESDAY EVENING. AS THIS OCCURS...WINDS WILL
FURTHER STRENGTHEN TO STORM FORCE AROUND 50 KT ACROSS THE CENTRAL
AND SOUTHERN PORTIONS OF LAKE MICHIGAN...STARTING LATER WEDNESDAY
AFTERNOON. NORTHERN SECTIONS WILL INCREASE TO HIGH END GALES AND AM
STILL WATCHING POTENTIAL FOR STORM FORCE GUSTS TO 50 KT.
UNCERTAINTY STILL SURROUNDS THIS SO WILL MOVE AHEAD WITH A GALE
WARNING BUT AN UPGRADE MAY BE NEEDED FOR WEDNESDAY EVENING/NIGHT.
ALSO WATCHING FOR GUST POTENTIAL IN THE 55-60 KT RANGE SOUTH...BUT
WITH THE AIRMASS OVER THE LAKE NOT BEING TERRIBLY COLD RELATIVE TO
THE LAKE WATER MIXING MAY BE LIMITED. DESPITE THIS FEEL THAT 50 KT
WILL BE ACHIEVED GIVEN WINDS INCREASING TO AROUND 50 KT IN THE
FIRST FEW HUNDRED FEET ABOVE LAKE LEVEL...IT MAY BE DIFFICULT TO
SEE GUSTS HIGHER THAN THAT HOWEVER. WILL CONTINUE TO MONITOR. PEAK
GUSTS ARE EXPECTED WEDNESDAY EVENING AND NIGHT.
THE LOW WILL BEGIN TO WEAKEN AND TURN NORTHEAST THURSDAY ALLOWING
WINDS TO EASE THROUGH THE DAY THOUGH GALE FORCE IS EXPECTED
THROUGH THE AFTERNOON. HIGH PRESSURE WILL THEN ARRIVE FRIDAY AND FRIDAY
NIGHT RESULTING IN MUCH QUIETER CONDITIONS. A WEAK FRONT MAY CROSS
THE LAKE SOMETIME SUNDAY WITH A STRONGER SYSTEM AFFECTING THE AREA
EARLY NEXT WEEK.
MDB
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...LAKESHORE FLOOD WARNING...ILZ006-ILZ014...3 PM WEDNESDAY TO 4 PM
THURSDAY.
HIGH WIND WATCH...ILZ006-ILZ014...3 PM WEDNESDAY TO 10 AM
THURSDAY.
IN...HIGH WIND WATCH...INZ001-INZ002...3 PM WEDNESDAY TO 10 AM
THURSDAY.
LAKESHORE FLOOD WARNING...INZ001-INZ002...3 PM WEDNESDAY TO 9 PM
THURSDAY.
LM...GALE WARNING...LMZ080-LMZ567-LMZ669-LMZ671-LMZ673-LMZ675-LMZ777-
LMZ779-LMZ868-LMZ870-LMZ872-LMZ874-LMZ876-LMZ878...5 AM
WEDNESDAY TO 3 PM WEDNESDAY.
STORM WARNING...LMZ080-LMZ567-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-
LMZ741-LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ868-
LMZ870-LMZ872-LMZ874-LMZ876-LMZ878...3 PM WEDNESDAY TO 3 PM
THURSDAY.
GALE WARNING...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565...10 AM
WEDNESDAY TO 10 PM THURSDAY.
GALE WARNING...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745...1 AM
WEDNESDAY TO 3 PM WEDNESDAY.
&&
$$
