335 AM CDT
THE MAIN FORECAST CONCERNS WILL BE THE POTENTIAL FOR FROST ACROSS MY
WESTERN COUNTIES TONIGHT. AND A WIDESPREAD FREEZE FOR MY WESTERN AND
SOUTHERN COUNTIES SATURDAY NIGHT.
IT WILL CONTINUE TO BE A BREEZE DAY ACROSS THE AREA TODAY AS
COLDER AIR CONTINUES TO FILTER SOUTH ACROSS THE AREA. HOWEVER...IT
APPEARS THE WINDOW FOR ADVISORY CRITERIA WINDS HAS PASSED.
THEREFORE...I WILL END THE ADVISORY FOR ALL BUT LAKE AND PORTER
INDIANA. THESE AREAS WILL LIKELY CONTINUE TO EXPERIENCE LOW END
ADVISORY FORCE WINDS OFF THE LAKE THROUGH MID TO LATE MORNING...SO
I HAVE EXTENDED THE ADVISORY THROUGH 18 UTC FOR THESE TWO
NORTHWEST INDIANA COUNTIES.
PRECIPITATION WILL END FOR ALL BUT THE NORTHWEST INDIANA COUNTIES
AND THE ADJACENT ILLINOIS COUNTIES...WHERE LAKE EFFECT SHOWERS MAY
CONTINUE. THE COLD AIR MASS IS SETTING UP A FAVORABLE THERMODYNAMIC
ENVIRONMENT ACROSS LAKE MICHIGAN FOR LAKE EFFECT RAIN SHOWERS.
SURFACE TO 850 DELTA T'S WILL RUN BETWEEN 18 TO 20 DECREES
CELSIUS. THIS SHOULD RESULT IN LAKE INDUCED EL'S IN EXCESS OF
15,000 FT LATE TODAY AND THIS EVENING. OUR LOCAL WRF MODEL
INDICATES THAT THE WINDS ACROSS THE LAKE WILL VEER FROM THE
NORTHWEST TO THE NORTH LATER TODAY AS SURFACE HIGH PRESSURE ACROSS
THE PLAINS BUILDS EAST. THIS LOOKS TO SET UP GOOD BOUNDARY LAYER
CONVERGENCE ALONG THE NORTHWEST INDIANA COUNTIES INTO TONIGHT.
THIS WOULD LIKELY SHIFT ANY BAND OF LAKE EFFECT SHOWERS WESTWARD
ACROSS MY NORTHWEST INDIANA COUNTIES BY THIS EVENING. I SUSPECT THAT
THESE LAKE INDUCED SHOWERS MAY CONTINUE INTO SATURDAY
MORNING...AND COULD ALSO SHIFT BACK ACROSS PORTIONS OF
NORTHEASTERN ILLINOIS. HOWEVER...THE THERMODYNAMIC ENVIRONMENT
WILL QUICKLY BECOME LESS FAVORABLE FOR SHOWERS ON SATURDAY AS WARMER
MID LEVEL TEMPERATURES LOWER INVERSION HEIGHTS.
FARTHER WEST AWAY FROM THE LAKE...FROST WILL BE THE MAIN
CONCERN...ESPECIALLY SATURDAY NIGHT. ALTHOUGH THERE WILL LIKELY BE A
DECK OF STRATO CU THAT DEVELOPS ACROSS THE AREA THIS
AFTERNOON...SKIES SHOULD QUICKLY CLEAR ACROSS NORTH CENTRAL ILLINOIS
THIS EVENING. AT THE SAME TIME WINDS WILL BE ABATING AS THE SURFACE
HIGH BUILDS EAST ACROSS THE UPPER MISSISSIPPI RIVER VALLEY. THIS
SHOULD ALLOW MY NORTH CENTRAL ILLINOIS COUNTIES TO DROP INTO THE 30S
TONIGHT. THIS WOULD POTENTIALLY SET THE STAGE FOR AREAS OF FROST IN
THESE AREAS. HOWEVER...DUE TO UNCERTAINTIES ON HOW QUICKLY THE WINDS
WILL DIE OFF...I DECIDED TO HOLD OFF ON FROST HEADLINES FOR NOW.
THE SURFACE HIGH WILL BUILD EAST SOUTHEASTWARD ACROSS NORTHERN
ILLINOIS ON SATURDAY AND SATURDAY NIGHT. TEMPERATURES WILL LIKELY
REMAIN IN THE MID 50S IN MOST AREAS ON SATURDAY...AND WITH THE
SURFACE HIGH OVERHEAD SATURDAY NIGHT...THE POTENTIAL IS THERE FOR A
WIDESPREAD FREEZE FOR PORTIONS OF NORTH CENTRAL ILLINOIS AND THE
WESTERN SUBURBS OF CHICAGO. A FREEZE WATCH MAY BE NEEDED IN THE
FUTURE DURING THIS PERIOD.
AN UPPER LEVEL RIDGE WILL BUILD EASTWARD ON SUNDAY...SETTING UP WARM
WESTERLY SURFACE FLOW. IT APPEARS A NICE PERIOD OF WARM AND DRY
WEATHER IS SETTING UP FOR THE FIRST WEEK OF OCTOBER. TEMPERATURES
WILL LIKELY BE IN THE 70S AS SOON AS MONDAY.
KJB
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 16Z...
* NORTHWEST WIND GUSTS INCREASING TO 25-30 KT EARLY THIS AFTERNOON.
* SCT-BKN SKIES AROUND 3500 FT THROUGH THE AFTERNOON WITH BASES
RISING TOWARDS 4000 FT.
MDB
//DISCUSSION...UPDATED 16Z...
WIND GUSTS STARTING TO COME UP SLIGHTLY AND EXPECT THAT HEATING
WILL ALLOW THEM TO INCREASE TO 25-30 KT FOR THE AFTERNOON FOR THE
CHI ARE TERMINALS. CURRENT BAND OF STRATOCU JUST INLAND OF LAKE
MICHIGAN HAS BEEN SHOWING MORE BREAKS LAST HALF HOUR OR SO LIKELY
RESULTING IN SCATTERED COVERAGE SOON. LARGER AREA OF STRATOCU IS
MOVING SOUTHWARD FROM W WHICH WILL RESULT IN BROKEN CLOUD COVERAGE
FOR THE AFTERNOON THOUGH SCATTERED PERIODS MAY OCCUR AS WELL.
EXPECT BASES TO REMAIN LOW END VFR IN THE 3500-4500 FT RANGE.
FROM 12Z...
NW GUSTY WINDS BEHIND THE COLD FRONT CONTINUE TODAY...WITH GUSTS
UP TO 30 KT FOR MOST OF THE DAY TODAY. THE WINDS WILL SLOWLY
DIMINISH TODAY AS HIGH PRESSURE MOVES IN AND THE PRESSURE GRADIENT
RELAXES. WINDS WILL ALSO BECOME MORE NORTHERLY. EXPECTING
PRIMARILY VFR CIGS THIS MORNING WITH LOW END MVFR CIGS FOR THE
TERMINALS CLOSER TO LAKE MICHIGAN...WERE LINGERING SHOWERS AND AN
EXITING CLOUD DECK REMAIN. GYY WILL HAVE MVFR CIGS FOR MOST OF
THE DAY TODAY AS LAKE EFFECT SHOWERS AND CLOUDS ARE ADVECTED
INLAND. THIS AFTERNOON VFR CU WILL DEVELOP ACROSS THE REGION AS
THE SURFACE WARMS.
A BAND OF LAKE EFFECT PRECIP WILL BEGIN TO DEVELOP THIS AFTERNOON
AND SLOWLY MOVE WESTWARD AS THE WINDS SHIFT FROM N TO NW OVER THE
LAKE TONIGHT. GYY WILL BE MOST AFFECTED BY THE PRECIP AND LOW VFR
CLOUD DECK...BUT INCLUDED VCSH AND SCT030 FOR ORD AND MDW AS THE
SHOWERS AND CLOUDS WILL LIKELY MOVE INLAND ON THE ILLINOIS SIDE OF
THE LAKE AS WELL. ALTHOUGH ATTM...NOT ENTIRELY POSITIVE THAT THE
SHOWERS WILL MAKE IT TO THE ORD AND MDW TERMINALS. ALSO DECIDED TO
PUT VCSH IN FOR ORD AND MDW TO ACCOUNT FOR SHOWERS OVER THE
LAKE...WHICH WOULD IMPACT WEST FLOW APPROACHES. FOR THE TERMINALS
WEST OF ORD...EXPECTING CLEAR SKIES AND DRY CONDITIONS TO PREVAIL
OVERNIGHT AND INTO SATURDAY MORNING.
JEE
//ORD AND MDW CONFIDENCE...UPDATED 16Z...
* HIGH CONFIDENCE IN WIND FORECAST.
* HIGH CONFIDENCE IN CEILING TRENDS THROUGH THE AFTERNOON.
MDB
//OUTLOOK FOR ORD/MDW FOR 00Z SUNDAY-12Z FRIDAY...UPDATED 14Z...
SATURDAY NIGHT THROUGH THURSDAY...VFR.
MDB
&&
.MARINE...
424 AM CDT
MAIN ISSUES THIS FORECAST PERIOD CONTINUE TO BE WITH THE CURRENT
AREA OF LOW PRESSURE NOW SHIFTING EAST OF THE LAKE...BUT WITH A
VERY TIGHT PRESSURE GRADIENT AS WELL AS MUCH STRONGER FLOW ALOFT
OVER HEAD. THIS COINCIDING WITH A COLDER AIR MASS FILTERING IN
FROM THE NORTH HAS PROVIDED STORM FORCE WINDS ALL ALONG THE LAKE
WITH MANY OBSERVATION SITES REPORTING STORM FORCE WINDS TO 50-55KT
SINCE LAST EVENING. ALTHOUGH WINDS WILL CONTINUE TO SLOWLY COME
DOWN THIS MORNING...DO EXPECT STORM FORCE WINDS TO PERSIST THROUGH
MID DAY. CURRENT STORM FORCE WARNING AND END TIME DOES APPEAR ON
TRACK WITH NO REAL CHANGE TO THE WARNING AT THIS TIME. LATEST
GUIDANCE IS INDICATING THAT WINDS WILL BE COMING DOWN CLOSER TO
THE END TIME...MID MORNING...BUT WILL LEAVE AS IS FOR NOW AND LET
LATER FORECASTS CANCEL EARLY IF NEED BE.
DESPITE THESE WINDS COMING DOWN...GALE FORCE WINDS WILL CONTINUE
THROUGH MUCH OF THE DAY AS THIS TIGHT PRESSURE GRADIENT/STRONG FLOW
ALOFT WILL REMAIN. EXPECT GALE FORCE WINDS TO PERSIST INTO TONIGHT
BEFORE COMING DOWN AS A RIDGE OF HIGH PRESSURE APPROACHING FROM THE
WEST SLOWLY STARTS TO SHIFT OVERHEAD.
RODRIGUEZ
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...LAKESHORE FLOOD WARNING...INZ002 UNTIL 4 PM FRIDAY.
WIND ADVISORY...INZ001-INZ002 UNTIL 1 PM FRIDAY.
LM...STORM WARNING...LMZ080-LMZ567-LMZ669-LMZ671-LMZ673-LMZ675-LMZ744-
LMZ745-LMZ777-LMZ779-LMZ868-LMZ870-LMZ872-LMZ874-LMZ876-
LMZ878 UNTIL 1 PM FRIDAY.
GALE WARNING...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565 UNTIL 1
AM SATURDAY.
GALE WARNING...NEARSHORE WINTHROP TO WILMETTE HARBORS UNTIL 4 PM FRIDAY.
GALE WARNING...LMZ741-LMZ742-LMZ743 UNTIL 10 PM FRIDAY.
&&
$$
