1159 AM CDT
PRELIMINARY DISCUSSION FOR LATE THIS AFTERNOON THROUGH SUN NIGHT...
UPPER LOW OVER QUEBEC AT MIDDAY WILL CONTINUE TO MOVE NE AND ACROSS
LABRADOR TONIGHT. AS IT DOES THE UPPER TROUGH TRAILING SW ACROSS THE
CENTRAL GREAT LAKES WILL CONTINUE OFF TO THE E WHILE AN UPSTREAM
SHORT WAVE MOVES FROM SOUTHERN MANITOBA AND THE NORTHERN PLAINS
EASTWARD...REACHING WESTERN QUEBEC AND THE UPPER MIDWEST BY 12Z SAT.
THIS SYSTEM WILL BE MOISTURE STARVED WITH ONLY AN INCREASE IN HIGH
AND SOME MID LEVEL CLOUDINESS OCCURRING OVERNIGHT WHICH WILL LIMIT
PROSPECTS OF FROST TO THE SE QUARTER OF THE FORECAST AREA AS CLOUDS
ARE NOT EXPECTED TO ARRIVE THERE TIL THE PREDAWN HOURS.
THIS SHORT WAVE PUSHES A WEAK COLD FRONT ACROSS THE NORTHERN AND
WESTERN PORTIONS OF THE LOCAL AREA DURING SAT AFTERNOON AND NIGHT
BUT WITH MINIMAL SHALLOW COLD AIR ADVECTION. THIS ALONG WITH THE
TIMING OF THE FRONT NOT UNTIL AFTERNOON AT THE EARLIEST TEMPERATURES
FOR SAT SHOULD BE ABLE TO REACH THE LOWER AND MID 60S.
WARM AIR ADVECTION TO BE OCCURRING FROM THE CENTRAL PLAINS TO THE
UPPER MIDWEST AND MS VALLEY SAT NIGHT INTO SUN AHEAD OF THE STRONGER
SHORT WAVE...CURRENTLY JUST REACHING SE AK AND THE B.C. COAST AT
MIDDAY...AS IT MOVES ACROSS S CENTRAL CANADA AND THE NORTHERN
PLAINS. WITH 850HPA TEMPS AVERAGING AROUND 7C DURING SUN AFTERNOON
SO THE MID AND UPPER 60S FROM MOS LOOK ON TRACK. THE SHORT WAVE
TROUGH CONTINUES E OVER THE WESTERN GREAT LAKES SUN EVENING
DRAGGING ANOTHER COLD FRONT...THIS ONE A BIT STRONGER...E ACROSS
THE FORECAST AREA BY MON MORNING. MOISTURE REMAINS LIMITED AND
WITH STRONGER DYNAMICS INCLUDING LEFT EXIT REGION OF UPPER JET
MOVING OVER MN AND WI HAVE ONLY SLIGHT CHANCE POPS SUN AFTERNOON
AND EVE. WITH THIS SYSTEM.
TRS
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 18Z...
* NO SIGNIFICANT CONCERNS.
RATZER
//DISCUSSION...UPDATED 18Z...
VFR CONDITIONS EXPECTED TO PERSIST THROUGH SATURDAY. SURFACE HIGH
PRESSURE RIDGE AXIS WILL MOVE EAST ACROSS TERMINALS THIS AFTERNOON
AND EARLY THIS EVENING...ALLOWING GRADUAL SHIFT FROM LIGHT
NORTHWEST TO LIGHT SOUTHWEST WINDS. WEAKENING TROUGH/COLD FRONT
MOVES INTO THE MISSISSIPPI VALLEY ON SATURDAY...MAINTAINING
SOUTHWEST FLOW AHEAD OF IT ACROSS THE TERMINALS. DRY LOW AND MID
LEVELS SHOULD PRECLUDE MUCH IN THE WAY OF CLOUDS EXCEPT FOR SOME
PATCHY HIGH CIRRUS LATER TONIGHT AND SATURDAY.
RATZER
//ORD AND MDW CONFIDENCE...UPDATED 18Z...
* HIGH CONFIDENCE ALL ELEMENTS.
RATZER
//OUTLOOK FOR ORD/MDW FOR 00Z SUNDAY-12Z FRIDAY...UPDATED 12Z...
SATURDAY NIGHT...VFR.
SUNDAY...CHC SHRA.
MONDAY...VFR.
TUESDAY...CHC SHRA AND SLT CHC TSRA.
WEDNESDAY...SLT CHC SHRA.
THURSDAY...SLT CHC SHRA.
BMD
&&
.MARINE...
321 AM...LOW PRESSURE OVER QUEBEC WILL CONTINUE TO SLOWLY WEAKEN
AS IT LIFTS NORTHEAST TODAY AND TONIGHT. A RIDGE OF HIGH PRESSURE
EXTENDING FROM WESTERN ONTARIO SOUTH INTO THE PLAINS...WILL MOVE
SOUTHEAST ACROSS THE WESTERN LAKES THIS AFTERNOON INTO THIS
EVENING. THUS THE GRADIENT WILL CONTINUE TO SLOWLY WEAKEN THROUGH
THE DAY...THOUGH SOME GUSTS TO 30 KT ARE STILL POSSIBLE ACROSS FAR
NORTHERN LAKE MICHIGAN EARLY THIS MORNING. A WEAK TROUGH OF LOW
PRESSURE WILL MOVE ACROSS THE WESTERN LAKES SATURDAY AND THEN IS
EXPECTED TO DISSIPATE AS LOW PRESSURE MOVES ACROSS MANITOBA
SATURDAY NIGHT AND THEN ACROSS ONTARIO SUNDAY AND SUNDAY NIGHT.
APPEARS THE GRADIENT WILL TIGHTEN ENOUGH FOR WINDS TO INCREASE
BACK INTO THE 15-25 KT RANGE SUNDAY/SUNDAY NIGHT AHEAD OF A COLD
FRONT THAT WILL TURN WINDS WESTERLY BY MONDAY MORNING. CMS
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...FROST ADVISORY...ILZ022-ILZ023-ILZ033-ILZ039...4 AM SATURDAY TO
8 AM SATURDAY.
IN...FROST ADVISORY...INZ001-INZ002-INZ010-INZ011-INZ019...4 AM
SATURDAY TO 8 AM SATURDAY.
LM...SMALL CRAFT ADVISORY...NEARSHORE GARY TO MICHIGAN CITY IN UNTIL 4 PM FRIDAY.
&&
$$
