952 PM CDT
NO CHANGES OF SUBSTANCE NEEDED TO GOING FORECAST...ONLY MINOR
TWEAKS TO GRIDDED ELEMENTS TO AGREE WITH NEAR TERM TRENDS.
TRS
//PREV DISCUSSION...
308 PM CDT
FOR THE REMAINDER OF THE AFTERNOON AND OVERNIGHT...CONDITIONS WILL BE
QUIET ACROSS NORTHERN ILLINOIS AND NORTHWESTERN INDIANA. THE
PRIMARY CONCERN WILL BE OVERNIGHT TEMPERATURES. BY SUNSET...THE
SCATTERED STRATOCU WILL DISSIPATE AND SKIES WILL BECOME MOSTLY
CLEAR. WITH A VERY DRY AIRMASS IN PLACE...RADIATIONAL COOLING WILL
ALLOW TEMPERATURES TO DROP OFF QUICKLY AFTER SUNSET.
HOWEVER...WINDS WILL NOT BE AS CALM OVERNIGHT TONIGHT...AND IN
FACT...INCREASING SOUTHERLY FLOW AND CLOUD COVER WILL DEVELOP IN
ADVANCE OF THE SFC TROUGH/COLD FRONT MOVING THROUGH THE NRN PLAINS.
SO...DO NOT EXPECT TEMPERATURES TO DROP BELOW FREEZING...AND ONLY
EXPECT FROST OVER THE EASTERN PORTIONS OF THE CWA...AWAY FROM THE
LAKE. A FROST ADVISORY WILL BE ISSUED.
FOR TOMORROW...THE FORECAST CONCERNS WILL SHIFT TO THE NEXT
UPSTREAM SYSTEM CURRENTLY MOVING OUT OVER THE NRN PLAINS. THE
GUIDANCE IS IN GOOD OVERALL AGREEMENT ON TRACKING THIS SYSTEM
RAPIDLY EASTWARD. CHANCES FOR PCPN WILL QUICKLY INCREASE THROUGH
THE MORNING HOURS...SPREADING EASTWARD THROUGH THE DAY. WHILE THE
SYSTEM APPEARS TO BE QUITE ENERGETIC ALOFT...SFC MOISTURE IN ADVANCE
OF THE SYSTEM WILL BE MODERATE WITH LITTLE OPPORTUNITY FOR A RETURN
FLOW FROM THE GULF. WITH SFC DEWPOINTS SLOWLY INCREASING THROUGH
THE DAY FROM THE LOWER 30S TO AROUND 40...PCPN WILL START OUT VERY
LIGHT AND ONLY BECOME MEASURABLE AND MORE WIDESPREAD BY THE LATE
AFTERNOON. QUICK FLOW ALOFT WILL PUSH THE SYSTEM QUICKLY OFF TO THE
EAST...WITH PCPN EXITING THE NWRN INDIANA COUNTIES BY EARLY MONDAY
MORNING.
THE REMAINDER OF THE SHORT TERM...MONDAY THROUGH TUESDAY NIGHT
SHOULD THEN BE DRY. TEMPERATURES THOUGH THIS PERIOD SHOULD REMAIN
NEAR SEASONAL NORMAL LEVELS THROUGH MONDAY WITH HIGHS IN THE LOWER
TO MIDDLE 50S AND LOWS IN THE MIDDLE TO UPPER 30S. BY TUESDAY...AS
WARM ADVECTION INCREASES AHEAD OF THE NEXT UPSTREAM SYSTEM...
TEMPERATURES SHOULD REACH INTO THE UPPER 50S TO LOWER 60S.
FOR THE LONGER TERM...WEDNESDAY THROUGH SATURDAY...THE FORECAST
UNCERTAINTY REMAINS FOR THE WEDNESDAY THROUGH THURSDAY NIGHT
PERIOD. THE GFS AND ECMWF THIS ARE ADVERTISING DIFFERENT TYPES OF
SOLUTIONS IN HOW THEY HANDLE THE SHORT WAVE ENERGY INTERACTION
BETWEEN THE SOUTHERN AND NORTHERN STREAMS. THE GFS STILL WANTS TO
MAINTAIN A SLOWER...MORE PHASED SOLUTION WHICH EMPHASIZES THE
NORTHERN STREAM SHORTWAVE. THE ECMWF STILL WANTS TO EMPHASIZE THE
SOUTHERN STREAM WAVE...DEVELOPING A CLOSED UPPER LOW OVER MISSOURI
BY WEDNESDAY NIGHT. SO...WILL KEEP A FAIRLY CONSERVATIVE FORECAST
WITH HIGH CHANCE POPS FOR WEDNESDAY THROUGH THURSDAY...AND WAIT A
LITTLE LONGER FOR A BETTER GUIDANCE CONSENSUS BEFORE INCREASING POPS
HIGHER THAN CHANCE LEVELS. FEEL FAIRLY CONFIDENT THAT THERE WILL BE
MEASURABLE PCPN DURING THIS PERIOD...IT IS THE TIMING THAT IS MAINLY
IN QUESTION. BY THE END OF THE WEEK...CONDITIONS WILL SETTLE DOWN
AS THE NEXT UPPER RIDGE MOVES OVER THE MIDWEST.
KREIN
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 06Z...
* LIGHT AND VARIABLE WINDS TURNING SOUTH/SOUTHEAST OVERNIGHT THEN
BECOMING GUSTY TO AROUND 25 KT MID/LATE MORNING.
* SHOWER CHANCES INCREASING THIS AFTERNOON.
* LOWERING VFR CIGS THIS AFTERNOON.
RATZER
//DISCUSSION...UPDATED 06Z...
VERY LITTLE CHANGE TO PREVIOUS FORECAST THINKING...WITH NEW 00Z
GUIDANCE VERY SIMILAR TO EARLIER RUNS.
WEAK HIGH PRESSURE WILL MOVE OFF TO THE EAST OF THE TERMINALS
EARLY THIS MORNING AS LOW PRESSURE DEVELOPS INTO THE UPPER
MISSISSIPPI VALLEY. LIGHT VARIABLE WINDS WILL BECOME SOUTHEAST IN
RESPONSE TO THE SURFACE PRESSURE FALLS...AND WILL GRADUALLY
INCREASE AND BECOME GUSTY DURING THE MORNING AS THE PRESSURE
GRADIENT TIGHTENS AHEAD OF THE LOW. GUSTS TO 25 KNOTS ARE LIKELY
BY MID-DAY. THE GRADIENT WILL THEN WEAKEN BY LATE AFTERNOON...AS
THE LOW MOVES INTO WISCONSIN AND BEGINS TO FILL. THIS WILL ALLOW
WINDS TO DIMINISH AND SHIFT SOUTHWEST.
MID AND HIGH CLOUD VFR CEILINGS WILL DEVELOP EARLY THIS MORNING
AND WILL ONLY GRADUALLY LOWER THIS MORNING. DRY AIR IN THE LOW
LEVELS WILL TAKE SOME TIME TO SATURATE...WITH RAIN CHANCES
INCREASING DURING THE AFTERNOON HOURS. CIGS WILL LIKELY LOWER INTO
LOW END VFR DURING SHOWERS THIS AFTERNOON...AND THOUGH SOME PATCHY
MVFR CIGS ARE POSSIBLE VFR CONDITIONS SHOULD GENERALLY PREVAIL.
LOWER CLOUDS SHOULD SCATTER OUT DURING THE EVENING AS THE LOW
LEVEL FLOW BECOMES SOUTHWEST BEHIND THE COLD FRONT TRAILING THE
LOW.
RATZER
//ORD AND MDW CONFIDENCE...UPDATED 06Z...
* HIGH CONFIDENCE IN LIGHT AND VARIABLE WINDS TURNING SOUTHERLY BY
SUNRISE AND GUSTS INCREASING TO AROUND 25 KT MID/LATE MORNING.
* MEDIUM-HIGH CONFIDENCE IN SHRA AFFECTING THE TERMINALS SUNDAY
AFTERNOON/EARLY EVENING.
* MEDIUM CONFIDENCE THAT CEILINGS WILL LOWER TO LOW END VFR SUNDAY
AFTERNOON.
RATZER
//OUTLOOK FOR ORD/MDW FOR 12Z MONDAY-12Z SATURDAY...UPDATED 00Z...
MONDAY...MVFR CIGS POSSIBLE IN THE MORNING...OTHERWISE VFR.
TUESDAY...VFR.
WEDNESDAY...CHANCE SHRA...MAINLY VFR.
THURSDAY...CHANCE SHRA...MVFR CIGS POSSIBLE.
FRIDAY...VFR.
MDB
&&
.MARINE...
245 PM CDT
RIDGE OF HIGH PRESSURE REMAINS OVERHEAD THIS EVENING...HOWEVER
THIS WILL STEADILY DRIFT EAST. A TROUGH OF LOW PRESSURE CONTINUES
TO DEVELOP ACROSS THE UPPER MISSISSIPPI VALLEY AND IS EXPECTED TO
SLIDE SOUTHEAST AND APPROACH THE WESTERN GREAT LAKES REGION
SUNDAY. PRIOR TO THIS THE WINDS ARE EXPECTED TO TURN SOUTHWESTERLY
TO SOUTHERLY AND INCREASE. THE PRESSURE GRADIENT FOR SEVERAL MODEL
RUNS HAS CONTINUED TO INDICATE GALE CRITERIA IS LIKELY FOR THE
OPEN WATERS...WITH GALES TO 35 KT. A FEW SOLUTIONS INDICATED THAT
WINDS MAY PUSH TO 40KT...HOWEVER FEEL THAT THE MAJORITY OF WINDS
WILL BE IN THE 35KT RANGE FROM THE SOUTH. FOR THE NEARSHORE WATERS
WINDS WILL ALSO BECOME ELEVATED...AND GUIDANCE CONTINUES TO
INDICATE WINDS BETWEEN 15 AND 25 KT TO AT TIMES APPROACHING 30KT
OR JUST UNDER GALE CRITERIA. FOR NOW HAVE GONE WITH A SMALL CRAFT
ADVISORY FOR THE ENTIRE NEARSHORE WATERS OF ILLINOIS/NORTHWEST
INDIANA THROUGH SUNDAY EARLY EVENING.
PRESSURE GRADIENT BEGINS TO RELAX LATE SUNDAY AFTERNOON AND WILL
EVENTUALLY ALLOW WINDS TO GO BELOW GALE CRITERIA. NONETHELESS
WAVES WILL REMAIN ELEVATED FROM THE DURATION OF SOUTHERLY WINDS
THROUGH SUNDAY EVENING...AND POSSIBLY INTO MONDAY MORNING. THEN
WINDS AND WAVES RELAX THROUGH MIDWEEK.
BEACHLER
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...FROST ADVISORY...ILZ004-ILZ005-ILZ011-ILZ012-ILZ013-ILZ020-
ILZ021-ILZ022-ILZ023-ILZ033 UNTIL 8 AM SUNDAY.
IN...FROST ADVISORY...INZ001-INZ002-INZ010-INZ011-INZ019 UNTIL 8 AM
SUNDAY.
LM...GALE WARNING...LMZ080-LMZ567-LMZ669-LMZ671-LMZ673-LMZ675-LMZ777-
LMZ779-LMZ868-LMZ870-LMZ872-LMZ874-LMZ876-LMZ878...7 AM
SUNDAY TO 9 PM SUNDAY.
SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
LMZ745...7 AM SUNDAY TO 10 PM SUNDAY.
&&
$$
