812 PM CDT
SURFACE LOW PRESSURE HAS PUSHED NORTHEAST INTO FAR NORTHEAST LAKE
HURON...AND WILL CONTINUE TO WEAKEN AND LIFT NORTHEAST AWAY FROM
THE GREAT LAKES REGION THROUGH THE OVERNIGHT PERIOD. IR IMAGERY
THIS EVENING CONTINUES TO SHOW SOME MID/HIGH LEVEL CLOUDS ROTATING
AROUND THE WESTERN PERIPHERY OF THE DEPARTING TROUGH...WITH CLEAR
SKIES ENCOMPASSING IOWA/MINNESOTA/WESTERN WISCONSIN. GUIDANCE
CONTINUES TO SUGGEST THAT THE CLEAR SKIES OVER WESTERN WISCONSIN
WILL EVENTUALLY ARRIVE OVER WESTERN PORTIONS OF ILLINOIS...HOWEVER
IT MAY TAKE UNTIL 2 TO 3 AM BEFORE THIS OCCURS. AS A RESULT
TEMPERATURES WILL REMAIN SLIGHTLY WARMER THAN NEIGHBORS TO THE
WEST/NORTH. PRECIPITATION ACROSS OUR FAR EASTERN CWFA HAS ERODED
OR PUSHED EAST...AND HAVE OPTED TO REMOVE MENTION OF PRECIP
THROUGH THE REMAINDER OF THE OVERNIGHT FOR THOSE COUNTIES.
FROST FORMATION STILL LOOKS TO BE A GOOD BET...WITH WINDS
DECOUPLING OVER MANY INLAND LOCATIONS AS SFC RIDGING STEADILY
BUILDS IN FROM THE WEST. THE WILDCARD IS THAT IT APPEARS THE MEAT
OF THE SURFACE RIDGE DOES NOT PUSH OVER OUR CWFA...WHICH COULD
RESULT IN 3 TO 5 KT OF WIND THROUGH THE REMAINDER OF THE OVERNIGHT
PERIOD. THIS COULD INHIBIT FROST FORMATION. AT THIS TIME
CONFIDENCE IS NOT HIGH ENOUGH TO REMOVE THE HEADLINE...SO WILL
LEAVE ALL IN PLACE AS IS. TEMPERATURES FALLING INTO THE
LOWER/MIDDLE 30S STILL LOOKS FAVORABLE.
BEACHLER
&&
.PREV DISCUSSION...
302 PM CDT
LATE THIS AFTERNOON THROUGH SAT NIGHT...
THE UPPER LOW CENTER OF CIRCULATION WAS OVER LAKE ERIE AT MIDDAY AND
LIFTING TO THE NNE. SHORT RANGE MODEL OUTPUT HAS A GOOD HANDLE ON
THIS MOVEMENT AND CONTINUE TO LIFT THE UPPER LOW NNE-NE TO CENTRAL
QUEBEC BY 12Z FRI. WITH THE SYSTEM MOVING OFF TO THE NNE AND NE THE
REST OF TODAY AND THROUGH THE NIGHT THE BACK EDGE OF THE RAIN THAT
HAS BEEN SLOWLY ERODING/BREAKING UP OVER EASTERN WI AND NE IL AS
DRIER MID LEVEL AIR PER 12Z RAOBS...700HPA DEW POINT DEPRESSION OF
7C AT KMPX AND 12C AT KINL...GETS ENTRAINED INTO THE WEST SECTOR OF
THE GREAT LAKES SYSTEM.
THIS TREND WILL CONTINUE THE REST OF THE DAY AND BY THIS EVENING THE
WEST EDGE OF ANY SIGNIFICANT THREAT OF RAIN WILL HAVE SHIFTED OUT
OVER LAKE MI. ONLY EXCEPTION WILL BE PORTER COUNTY OF FAR NW IN
WHERE FORECAST THERMAL PROFILE STILL SUPPORTIVE OF LAKE EFFECT RAIN
BUT CLOUD BEARING LAYER FLOW FROM THE NNW-NW KEEPS MOST OF THE
REMAINING LAKE EFFECT MORE TOWARD N CENTRAL IN AND SW LOWER MI.
WITH THE WEAKENING OF THE LOW LEVEL PRESSURE GRADIENT CONTINUING
THIS AFTERNOON WINDS WILL CORRESPONDINGLY GRADUALLY DIMINISH
THOUGH REMAIN BREEZY.
MODELS SHOW THE SHORT WAVE TROUGH OVER GRB AT MIDDAY DROPPING S-SSE
AND CROSSING SE WI...NW IL AND NW IN OVERNIGHT. WHILE CONTINUED
DRYING OF LOWER AND MID WILL BE OCCURRING...THE SHORT WAVE TROUGH
WILL BRING SOME HIGH CLOUDINESS ACROSS THE LOCAL FORECAST AREA. HIGH
CLOUDS WILL CLEAR DURING OVERNIGHT BEFORE SUNRISE ALLOWING FOR
RADIATIONAL COOLING THUS THREAT OF FROST FOR EARLY MORNING FRI
REMAINS ACROSS THE WESTERN PORTIONS OF THE FORECAST AREA WHERE
COLDER TEMPERATURES AND LIGHTER WINDS WILL BE.
WITH THE UPPER LOW CONTINUING TO MOVE EVEN FARTHER AWAY FRI RIDGING
BUILDS FROM THE MID MO AND UPPER MS VALLEYS OVER THE UPPER MIDWEST
AND WESTERN GREAT LAKES. THIS WILL RESULT IN CLEAR SKIES AND A BIT
OF MODERATION IN TEMPERATURES FRI.
A SHORT WAVE IS PROGGED TO MOVE ESE FROM TO NORTHERN PLAINS TO THE
UPPER MIDWEST FRI NIGHT AND SAT. THIS SYSTEM WILL BE MOISTURE
STARVED WITH ONLY AN INCREASE IN HIGH AND SOME MID LEVEL CLOUDINESS.
THE SHORT WAVE DOES EVENTUALLY PUSH A COLD FRONT ACROSS INTO THE
LOCAL AREA SAT NIGHT WITH MODERATELY STRONG LOW LEVEL WARM AIR
ADVECTION OCCURRING AHEAD OF THE FRONT DURING SAT AS THE FLOW BACKS
TO SOUTHWESTERLY AHEAD OF THE APPROACHING SHORT WAVE TROUGH AND
ASSOCIATED COLD FRONT. THIS WARMING COMBINED WITH MAINLY SUNNY SKIES
AT LEAST FOR THE FIRST HALF OF THE DAY SHOULD ALLOW AFTERNOON
TEMPERATURES TO REACH FROM THE UPPER 50S TO THE MID 60S ACROSS THE
AREA ON SAT.
SUN THROUGH THU...
A STRONGER SHORT WAVE...LOCATED AROUND 45N 150W...WILL MOVE IN OFF
THE THE N PACIFIC INTO WESTERN CANADA AND ACROSS THE CANADIAN
ROCKIES BEFORE TURNING AND REACHING THE UPPER MIDWEST BY 12Z SUN.
THIS SYSTEM IS PROGGED TO HAVE MORE MOISTURE AVAILABLE BUT WITH THE
SURFACE LOW MOVING FROM SOUTHERN MANITOBA INTO WESTERN ONTARIO AND
THE STRONGER DYNAMICS N OF THE LOCAL FORECAST AREA ONLY HAVE SLIGHT
CHANCE TO LOW END CHANCE POPS FOR SHOWERS SUN AND SUN EVENING.
WHILE THIS SHORT WAVE WILL PUSH ANOTHER WEAK COLD FRONT THROUGH THE
LOCAL AREA LATER SUN AFTERNOON AND SUN EVENING WARM AIR ADVECTION IS
ALREADY UNDERWAY NOT TOO FAR UPSTREAM AS A BROAD UPPER RIDGE MOVES E
FROM THE ROCKIES OUT OVER THE HIGH PLAINS SUN NIGHT...AND CONTINUING
TO OVER THE UPPER AND MID MO VALLEY AND THE OZARKS BY MON EVENING.
THE 850HPA +10C ISOTHERM ADVANCES NE TO OVER NE IA...AND NW AND
CENTRAL IL BY THEN SO LOWER 60S NE TO MID 60S SW ACROSS THE FORECAST
AREA PER GUIDANCE LOOKS GOOD IF NOT A DEGREE OR TWO TOO LOW.
AN UPPER LOW THAT IS S OF THE ALEUTIAN PENINSULA AT PRESENT IS
PROGGED TO BECOME AN OPEN WAVE AS IT MOVES OVER SE AK AND THE B.C.
COAST MON...CROSS THE NORTHERN ROCKIES MON NIGHT AND BECOMING
POSITIVELY TILTED AS IT REACHES THE NORTHERN PLAINS AND CENTRAL
ROCKIES DURING TUE. POSITIONING OF THE SURFACE LOW ASSOCIATED WITH
THIS SYSTEM VARIES SOMEWHAT BETWEEN THE MODELS...CERTAINLY NOT
UNEXPECTED AT THAT TIME RANGE...BUT CONSENSUS OF MODELS AND
ENSEMBLE MEMBERS HAS IT TRACKING FROM CENTRAL IA AT 12Z TUE ENE
ACROSS EXTREME NW IL AND SE WI BEFORE THE END OF THE DAY.
THIS WILL HAVE THE LOCAL FORECAST AREA IN THE WARM SECTOR MON NIGHT
AND TUE INTO TUE NIGHT. OVERRUNNING PRECIPITATION SHIELD IS EXPECTED
TO BE OVER SOUTHERN WI WITH SHOWERS FARTHER S ACROSS NORTHERN IL AND
NW IN. YET ANOTHER COLD FRONT WILL BE DRAGGED ACROSS THE AREA TUE
NIGHT AND WED MORNING AS THE SURFACE LOW CONTINUES THROUGH THE
CENTRAL TO THE LOWER GREAT LAKES. THIS WILL DROP HIGHS ON WED TO A
FEW DEG F BELOW NORMALS.
TRS
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 00Z...
* VFR -DZ/-RA OVER THE NEXT FEW HOURS
SHEA
//DISCUSSION...UPDATED 00Z...
QUIET NIGHT ON THE HEELS OF THE LOW PRESSURE SYSTEM PULLING OUT
OF THE OHIO VALLEY OVERNIGHT. LIGHT SHOWERS NOTED ON RADAR WILL
QUICKLY PULL OUT OVER THE NEXT HOUR OR SO. SKIES WILL BEGIN TO
CLEAR OUT OVERNIGHT FROM WEST TO EAST AS RIDGING AND DRY AIR
FILTERS IN. OTHERWISE LIGHT NORTHWEST TO WEST FLOW WILL CONTINUE
THROUGH TOMORROW WITH SOME VFR CU DEVELOPING IN THE AFTERNOON
HOURS.
SHEA
//ORD AND MDW CONFIDENCE...UPDATED 00Z...
* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS
SHEA
//OUTLOOK FOR ORD/MDW FOR 12Z SATURDAY-12Z THURSDAY...UPDATED 00Z...
* SATURDAY...VFR
* SUNDAY...CHANCE SHRA
* MONDAY...VFR
* TUESDAY AND WEDNESDAY...CHANCE SHRA
SHEA
&&
.MARINE...
155 PM CDT
WINDS WILL CONTINUE TO GRADUALLY DIMINISH ACROSS LAKE MICHIGAN
THROUGH TONIGHT...AS DEEP LOW PRESSURE LIFTS TO THE NORTHEAST ALONG
THE EAST SHORE OF LAKE HURON AND INTO EASTERN ONTARIO.
EARLY AFTERNOON OBSERVATIONS AROUND THE LAKE INDICATE WINDS HAVE
EASED INTO THE 35-40 KT RANGE FOR THE MOST PART...THOUGH STILL A FEW
GUSTS INTO THE MID 40S AROUND SOUTH HAVEN MICHIGAN. BASED ON THIS...
AND THE EXPECTED TREND OF GRADUALLY DIMINISHING WINDS...WILL GO
AHEAD AND LET THE STORM WARNING END FOR THE OPEN WATERS AND INDIANA
NEAR SHORE ZONES...REPLACING THESE HEADLINES WITH A GALE WARNING
WHICH WILL CONTINUE THROUGH 06Z/1 AM CDT. WINDS MAY FALL BELOW GALE
A BIT EARLIER...BUT PREFER TO HAVE TO CANCEL EARLY RATHER THAN
EXTEND GALE HEADLINES LATER THIS EVENING. WINDS WILL CONTINUE TO
SLACKEN ON FRIDAY...AS THE LOW PULLS AWAY AND FILLS AND WEAK HIGH
PRESSURE RIDGING MOVES INTO THE WESTERN LAKES.
FOR THE ILLINOIS NEARSHORE AREAS...WILL MAINTAIN GALE WARNING
THROUGH 00Z/7 PM CDT WHICH WILL THEN ALLOW DOWNGRADE TO A SMALL
CRAFT ADVISORY AT THAT TIME.
LATER IN THE FORECAST PERIOD...A COUPLE OF TRANSIENT LOW PRESSURE
SYSTEMS WILL AFFECT THE REGION. ONE WEAKER LOW IS EXPECTED TO PASS
ACROSS THE NORTHERN LAKES ON SUNDAY...AND IS PROGGED TO DEEPEN
SLIGHTLY AS IT MOVES OFF TO THE EAST MONDAY. THIS WILL LIKELY
PRODUCE A RELATIVELY SHORT PERIOD OF GUSTY WEST WINDS AROUND 25 KTS.
A SECOND LOW PRESSURE SYSTEM IS EXPECTED TO DEVELOP LATE TUESDAY AND
WEDNESDAY ACROSS REGION. MODEL FORECASTS EXHIBIT QUITE A BIT OF
SPREAD IN LOCATION/STRENGTH AT THIS TIME...SO HAVE STAYED WITH
BLENDED GUIDANCE SOLUTION WHICH MAY ULTIMATELY END UP BEING TOO LOW
WITH WIND SPEEDS. THIS WILL BE MONITORED FOR MORE DETAIL AS FURTHER
MODEL RUNS GET A BETTER HANDLE ON THIS SYSTEM FOR THE MIDDLE OF NEXT
WEEK.
RATZER
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...FROST ADVISORY...ILZ003-ILZ004-ILZ005-ILZ008-ILZ010-ILZ011-
ILZ012-ILZ019-ILZ020-ILZ021-ILZ032...1 AM FRIDAY TO 9 AM
FRIDAY.
IN...LAKESHORE FLOOD WARNING...INZ001-INZ002 UNTIL 9 PM THURSDAY.
LM...GALE WARNING...LMZ080-LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-
LMZ567-LMZ669-LMZ671-LMZ673-LMZ675-LMZ744-LMZ745-LMZ777-
LMZ779-LMZ868-LMZ870-LMZ872-LMZ874-LMZ876-LMZ878 UNTIL 1 AM
FRIDAY.
SMALL CRAFT ADVISORY...NEARSHORE WINTHROP HARBOR TO GARY IN UNTIL 1 PM
FRIDAY.
&&
$$
