323 AM CDT
WARMER TEMPERATURES ARE THE NEAR TERM FOCUS AS BROAD UPPER RIDGE
SHIFTS EAST ACROSS THE GREAT LAKES TODAY...WHILE NORTHERN STREAM
SHORT WAVE TRAVERSES ONTARIO. SURFACE LOW ASSOCIATED WITH THIS WAVE
TRAILS A SLOW MOVING COLD FRONT FROM NORTHERN WISCONSIN INTO CENTRAL
IOWA BY THIS EVENING...WITH WFO LOT FORECAST AREA IN BREEZY WARM
SECTOR DURING THE DAY. OTHER THAN A LITTLE PATCHY THIN
CIRRUS...SHOULD BE RELATIVELY CLOUD-FREE...WITH TEMPS SURGING INTO
THE 60S. COMPARING LOW LEVEL MODEL THERMAL PROGS AND UPSTREAM TEMPS
ACROSS THE MID-MISSOURI VALLEY YESTERDAY...HAVE GONE A COUPLE
DEGREES ABOVE GUIDANCE FOR HIGHS AS FORECAST SOUNDINGS AND 00Z
UPSTREAM RAOBS INDICATE FAIRLY SHALLOW MIXED LAYER TO AROUND 950 MB
TODAY. SOUTH WINDS AT 15-20 KTS AT 950 MB SHOULD PREVENT LAKE
BREEZE...SO 6-9 DEGREE ABOVE NORMAL WARMTH WILL BE EXPERIENCED RIGHT
UP TO THE LAKE SHORE.
FORECAST CONCERNS THEN SHIFT TO RAIN POTENTIAL WEDNESDAY AND
THURSDAY. COLD FRONT MOVES SOUTHEAST INTO FAR NORTHERN ILLINOIS
WEDNESDAY MORNING...WITH THERMAL GRADIENT TIGHTENING ACROSS THE AREA
DURING THE AFTERNOON IN RESPONSE TO SURFACE LOW DEVELOPMENT OVER THE
LOWER MISSOURI VALLEY AS SOUTHERN STREAM SHORT WAVE CLOSES OFF OVER
SOUTHERN PORTION OF TROUGH. RESULTING LOW LEVEL FRONTOGENESIS OVER
THE NORTHWEST HALF OF THE CWA AND INCREASING LARGE SCALE ASCENT WITH
APPROACHING TROUGH WILL INCREASE RAIN POTENTIAL ALONG/BEHIND FRONT.
AS SYSTEM CONTINUES TO CLOSE OFF OVER MISSOURI AND SOUTHERN ILLINOIS
WEDNESDAY NIGHT INTO THURSDAY AND FRONTAL ZONE SHIFTS SOUTHEAST
ACROSS THE FORECAST AREA...RAIN CHANCES WILL INCREASE ACROSS THE
REMAINDER OF THE CWA. HIGHEST POPS WILL BE WEDNESDAY NIGHT AND EARLY
THURSDAY...BEFORE UPPER/SFC LOWS DRIFT EAST THROUGH THE OHIO VALLEY
AS FLOW OTHERWISE REMAINS PROGRESSIVE. EARLIER DIFFERENCES WITH
POSITION OF THE SFC LOW BY THURSDAY MORNING APPEAR TO BE DIMINISHING
WITH 00Z RUNS...WITH 00Z GFS/ECMWF AND GEFS ENSEMBLE CLUSTERING
SUGGESTING LOW NEAR KSTL BY 12Z. OF CURIOUS NOTE...THE NAM REALLY
COOLS THE COLUMN ACROSS THE FAR NORTHWEST CWA LATE WEDNESDAY NIGHT
WHICH WOULD SUGGEST POTENTIAL FOR WET SNOW TO MIX IN WITH RAIN AS
FAR SOUTHEAST AS KRFD...BUT MAINLY NORTH AND WEST OF THE CWA. GIVEN
STRONGER FORCING TO THE SOUTH WITH THE MAIN VORT AND UPPER LOW...
PREFER WARMER LOOK OF GFS/ECMWF/GEM SOLUTIONS AT THIS POINT AND WILL
NOT MENTION THE S-WORD IN THE FORECAST. RAIN SHOULD DIMINISH FROM
NORTHWEST TO SOUTHEAST THURSDAY AFTERNOON AND EVENING...AS LOW
SCOOTS OFF TO THE EAST. WHILE NOT EXCESSIVE...TOTAL RAIN AMOUNTS MAY
RANGE BETWEEN A HALF INCH AND AN INCH OR SO.
TEMPS WILL BE A LITTLE TRICKY WEDNESDAY WITH FRONT PUSHING INTO THE
NORTHWEST PORTION OF THE CWA. HAVE LEANED FROM A BLEND OF MAV/MET
GUIDANCE NORTHWEST WHERE MORE CLOUDS AND HIGH PRECIP POTENTIAL WILL
BE TO A WARMER MET SOLUTION FAR SOUTHEAST. SIDED WITH A BLENDED
GUIDANCE WHICH UNDERCUTS MAV/MEX MOS BY A DEGREE OR TWO THURSDAY
GIVEN RAIN AND CLOUD COVER.
QUIET WEATHER RETURNS BY FRIDAY AS SURFACE HIGH PRESSURE SPREADS
ACROSS THE GREAT LAKES IN THE WAKE OF THE LOW...AND IN RESPONSE TO
RIDGING ALOFT IN WHAT REMAINS A HIGHLY AMPLIFIED JET PATTERN. LONGER
RANGE GUIDANCE REMAINS IN VERY GOOD AGREEMENT IN DIGGING SHORT WAVE
TROUGH BECOMING NEGATIVELY TILTED AND LIFTING OUT ACROSS THE UPPER
MIDWEST SATURDAY. OVERALL TREND IN GUIDANCE HAS BEEN TO SLOW THE
PROGRESSION OF THIS SYSTEM SOMEWHAT...WITH NEW 00Z ECMWF SLOWER
STILL THAN THE GFS. SYSTEM LOOKS FAIRLY DRY FOR OUR AREA...WITH MAIN
LOW-PROBABILITY PRECIP CHANCE COMING WITH THE PASSAGE OF THE
OCCLUDED COLD FRONT SATURDAY NIGHT INTO SUNDAY. WHILE WARM SECTOR
BECOMES PINCHED OFF...TEMPS NEAR 60 NOT TOO SHABBY A WEEK INTO
NOVEMBER. ONLY MODESTLY COOLER PACIFIC AIR BEHIND SYSTEM INTO MONDAY
WITH NEXT CHANCE OF RAIN LOOKING TO ARRIVE MONDAY NIGHT.
RATZER
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 20Z...
* WINDS GUSTING UP TO 20 KT THIS AFTERNOON.
* 40 TO 45 KT FLOW AT 1 TO 2 KFT LATE TONIGHT.
* CIGS DECREASING WEDNESDAY AFTERNOON AHEAD OF APPROACHING FRONTAL
SYSTEM...BUT AT LEAST REMAINING VFR THROUGH CURRENT TAF PERIOD.
BMD/MTF
//DISCUSSION...UPDATED 18Z...
A WARM FRONT WILL LIFT NORTH ACROSS THE REGION TODAY...WITH WINDS
VEERING FROM SSE TO SSW EARLY THIS AFTERNOON. MIXING WILL ALLOW
GUSTS TO AROUND 20 KTS...BEFORE CUTTING OFF AROUND SUNSET THIS
EVENING. DRY LOW AND MID LEVELS WILL KEEP SKIES MOSTLY SUNNY
TODAY...EXCEPT FOR SOME PATCHY CIRRUS. OVERNIGHT...DECOUPLING WILL
ALLOW WINDS TO DIMINISH AT THE SURFACE...BUT JUST ABOVE SURFACE
INVERSION...WINDS QUICKLY INCREASE TO AROUND 40 TO 45 KT. NOT
CONFIDENT ENOUGH THAT WINDS MAY BE INCREASE SHARPLY ENOUGH TO MEET
LLWS CRITERIA...BUT MAY CAUSE BUMPY RIDES OVER THE LOWER COUPLE
THOUSAND FEET.
ON WEDNESDAY...CLOUD COVER WILL INCREASE IN COVERAGE AS TAIL END OF
A COLD FRONT SWINGS THROUGH THE AREA. MODELS INDICATE SOME
PRECIPITATION ALONG WITH THE SURFACE TROUGH...BUT BETTER SIGNAL IS
ALONG AREA OF FRONTOGENESIS/DEFORMATION ZONE BEHIND THE FRONT. WITH
DRY ANTECEDENT CONDITIONS...EXPECT MODELS TO STRUGGLE WITH PRECIP
ONSET TIME...AND HAVE LEANED TOWARDS SLOWER GUIDANCE...WHICH KEEPS
PRECIP JUST BEYOND THE LATEST 30-HR TAF FOR ORD...AND 24-HR TAF FOR
RFD. CLOUDS WILL LOWER THROUGH THE AFTERNOON THOUGH...AND EXPECT
CIGS TO DROP BELOW 050 WEDNESDAY AFTERNOON...WITH ONSET OF
PRECIPITATION HOLDING OFF UNTIL THE EVENING. BMD
//ORD AND MDW CONFIDENCE...UPDATED 20Z...
* HIGH CONFIDENCE IN WIND DIRECTION AND VFR CONDITIONS THROUGH
THIS EVENING.
* LOW CONFIDENCE IN LLWS CONDS OVERNIGHT.
* MEDIUM CONFIDENCE IN TIMING OF LOWERING CIG TRENDS WEDNESDAY.
BMD/MTF
//OUTLOOK FOR ORD/MDW FOR 00Z THURSDAY-12Z TUESDAY...UPDATED 12Z...
WEDNESDAY NIGHT...SHRA. MVFR WITH POSSIBLE IFR CEILINGS.
THURSDAY...CHANCE OF SHRA. MVFR CEILINGS BECOMING VFR.
FRIDAY...VFR.
SATURDAY...SLIGHT CHANCE OF SHRA LATE...OTHERWISE VFR.
SUNDAY...SLIGHT CHANCE OF SHRA...OTHERWISE VFR.
MONDAY...VFR.
RODRIGUEZ
&&
.MARINE...
207 PM CDT
SOUTHERLY WINDS WILL REMAIN IN THE 20 TO 30 KT RANGE TONIGHT
INTO WEDNESDAY AHEAD OF AN APPROACHING COLD FRONT FROM THE UPPER
MISSISSIPPI VALLEY. THIS COLD FRONT WILL PUSH ACROSS FAR NORTHERN
LAKE MICHIGAN BY EARLY WEDNESDAY MORNING. THE COLD FRONT SHOULD
CLEAR THE ENTIRE LAKE BY WEDNESDAY EVENING. NORTH TO NORTHEASTERLY
WINDS WILL BE THE MAIN STORY BEHIND THIS FRONT AS THEY INCREASE
WEDNESDAY NIGHT. A SURFACE RIDGE OF HIGH PRESSURE EXTENDING FROM
THE PLAINS NORTHWARD ACROSS THE UPPER MIDWEST WILL BUILD IN ACROSS
THE NORTHERN PORTIONS OF THE LAKE WEDNESDAY NIGHT AND THURSDAY. AT
THE SAME TIME...A POTENT AREA OF LOW PRESSURE WILL MOVE ACROSS THE
MID MISSISSIPPI VALLEY EARLY THURSDAY. THE PRESSURE GRADIENT
ASSOCIATED WITH THESE TWO PRESSURE SYSTEMS APPEARS TO PRODUCE THE
STRONGEST WINDS...NEAR GALE FORCE...ACROSS THE SOUTHERN HALF OF THE
LAKE WEDNESDAY NIGHT INTO THURSDAY. THE SURFACE HIGH WILL FINALLY
BUILD ACROSS THE LAKE THURSDAY NIGHT INTO FRIDAY...PRODUCING A PERIOD
OF LIGHTER WINDS. HOWEVER...WINDS LOOK TO INCREASE OUT OF THE SOUTH
FRIDAY NIGHT INTO THE WEEKEND AS ANOTHER STRONG STORM SYSTEM
DEVELOPS ACROSS THE CENTRAL ROCKIES AND LIFTS NORTH NORTHEAST WARD
ACROSS THE UPPER MISSISSIPPI VALLEY BY THE END OF THE WEEKEND.
KJB
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
UNTIL 7 PM TUESDAY.
&&
$$
