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 12Z...
* WIND SHIFT TO THE NORTHWEST/NORTH THIS MORNING.
* PRECIPITATION CHANCES TUESDAY NIGHT.
* FLIGHT CATEGORY DROPPING TO MVFR AND POSSIBLY IFR TUESDAY NIGHT.
* TIMING/MAGNITUDE OF WIND GUSTS TUESDAY NIGHT. BMD
//DISCUSSION...UPDATED 12Z...
A WEAK SURFACE TROUGH IS DROPPING SOUTH ACROSS THE REGION THIS
MORNING...CAUSING WINDS TO SHIFT FROM WESTERLY AHEAD TO
NORTHWESTERLY AND EVENTUALLY NORTHERLY BEHIND. OTHER THAN THE
WIND SHIFT...NO IMPACTS ARE EXPECTED WITH THE TROUGH WITH VFR
CONDITIONS EXPECTED THROUGH MOST OF THE DAY TODAY. MEANWHILE...TO
THE SOUTH...AN AREA OF LOW PRESSURE IS EXPECTED TO LIFT NORTHWARD
INTO OHIO BY THIS EVENING. TO THE NORTHWEST OF THE LOW...MODELS
INDICATE A STRONG BAND OF FRONTOGENESIS DEVELOPING WITH MODERATE
PRECIPITATION OCCURRING AND CIGS DROPPING TO MVFR AND POSSIBLY IFR
OVERNIGHT. IN ADDITION...SOME MODELS ARE HINTING AT THE
POSSIBILITY OF LAKE EFFECT SHOWERS DEVELOPING WITH FAVORABLE
TRAJECTORIES TO IMPACT THE CHICAGO AREA TERMINALS. AS THE LOW
DEEPENS THIS EVENING...WINDS ARE EXPECTED TO INCREASE...WITH GUSTS
AROUND 20 KTS OR SO BEGINNING LATE TONIGHT...AND INCREASING TO
SPEEDS IN EXCESS OF 30 KTS BY MID MORNING WEDNESDAY. BMD
//ORD AND MDW CONFIDENCE...UPDATED 12Z...
* HIGH CONFIDENCE IN VFR CONDITIONS THROUGH THIS EVENING.
* LOW TO MEDIUM CONFIDENCE IN PRECIP TIMING/COVERAGE.
* MEDIUM CONFIDENCE IN CONDS DROPPING TO AT LEAST MVFR...LOW
CONFIDENCE IN IFR TUESDAY OVERNIGHT.
* MEDIUM TO HIGH CONFIDENCE IN WIND GUSTS IN EXCESS OF 30 KTS
BEGINNING WEDNESDAY MORNING. BMD
//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...
259 AM CDT
STORM FORCE WINDS NOW EXPECTED OVER MUCH OF LAKE MICHIGAN
WEDNESDAY AFTERNOON INTO THURSDAY. LOW PRESSURE OVER THE GULF OF
MEXICO WILL LIFT NORTH LATER TODAY AND TONIGHT AS IT DEEPENS. MODELS
CONTINUE TO TRACK THIS LOW FURTHER WEST WITH IT CENTERED ACROSS
NORTHWEST OHIO/SOUTHEAST LOWER MICHIGAN BY LATE WEDNESDAY NIGHT...
WHILE A RIDGE OF HIGH PRESSURE EXTENDS FROM ONTARIO SOUTH INTO THE
PLAINS. THE GRADIENT IS EXPECTED TO RAPIDLY TIGHTEN FROM LATE
TONIGHT THROUGH WEDNESDAY EVENING. WINDS SHOULD QUICKLY REACH GALE
FORCE AROUND OR SHORTLY AFTER DAYBREAK WEDNESDAY AND THEN REACH
STORM FORCE BY LATE WEDNESDAY AFTERNOON. STORM FORCE WINDS EXPECTED
TO CONTINUE THROUGH MIDDAY THURSDAY...UNTIL THE LOW BEGINS TO WEAKEN
AND LIFTS FURTHER NORTHEAST. CONTINUED HIGH END GALES ACROSS THE
NORTHERN THIRD OR SO OF LAKE MICHIGAN BUT STORM FORCE GUSTS ARE
STILL POSSIBLE THERE. CMS
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WATCH...LMZ080-LMZ567-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-
LMZ741-LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ868-
LMZ870-LMZ872-LMZ874-LMZ876-LMZ878...5 AM WEDNESDAY TO 4 PM
WEDNESDAY.
STORM WATCH...LMZ080-LMZ567-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-
LMZ741-LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ868-
LMZ870-LMZ872-LMZ874-LMZ876-LMZ878...4 PM WEDNESDAY TO 3 PM
THURSDAY.
GALE WATCH...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565...10 AM
WEDNESDAY TO 10 PM THURSDAY.
&&
$$
