805 PM CDT
NO LARGE SCALE CHANGES NEEDED TO GOING FORECASTS FOR TONIGHT.
SHORT TERM ADJUSTMENTS FOR CONTINUED W TO E CLEARING OF
STRATOCUMULUS WITH BACK EDGE MOVING OVER THE LAKE SHORE BETWEEN
9 AND 930 PM CDT. ALSO ADJUSTED TEMPERATURES FOR REST OF THE
EVENING AS CLEAR SKIES AND DRY CALM AIR WITH THE SURFACE RIDGE
SITTING RIGHT OVER THE LOCAL FORECAST AREA ALLOWED TEMPERATURES
TO NOSEDIVE INTO THE 30S AFTER SUNSET W AND S PORTIONS OF AREA.
TRS
//PREV DISCUSSION...
301 PM CDT
VISIBLE SATELLITE IMAGERY CONTINUES TO SHOW CONSIDERABLE CLOUDS
ACROSS NORTHERN ILLINOIS STRETCHING NORTH THROUGH WISCONSIN. FURTHER
UPSTREAM ACROSS IOWA/MINNESOTA DIFLUENT FLOW ALOFT HAS ALLOWED DRY
AIR TO ENTRAIN INTO THE NEAR SFC ENVIRONMENT...AND ERODE MOST OF THE
CLOUDS WITH FULL SUNSHINE. LLVL ANTI-CYCLONIC FLOW REMAINS CENTERED
OVER THE TENNESSEE VALLEY AND BEGINNING TO DRIFT EAST AS THE MID-LVL
TROUGH AXIS PIVOTS EAST AS WELL.
OVERNIGHT INTO TUE AS TROUGH AXIS DEPARTS THE REGION...SEMI-ZONAL
FLOW SETS UP AT 500MB. DOWNSTREAM RIDGE WILL SLOW DOWN AND BECOME
POSITIONED OVER THE MID-ATLANTIC/NEW ENGLAND REGIONS THROUGH WED.
ACROSS THE UPPER MIDWEST GUIDANCE CONTINUES TO INDICATE A FRONTAL
BOUNDARY WILL SAG SOUTH. THE CHALLENGE HAS CONTINUED TO BE ON THE
FORWARD SPEED AND PRECIP TIMING WITH THIS BOUNDARY.
TEMPERATURES OVERNIGHT WITH DEPARTING CLOUDS WILL STEADILY RADIATE
INTO THE 30S AWAY FROM LAKE MICHIGAN...POSSIBLY TOUCHING THE
FREEZING POINT. CLOSER TO LAKE MICHIGAN TEMPERATURES WILL HOVER IN
THE UPPER 30S TO ARND 40 DEG.
TUESDAY WILL BE MUCH WARMER WITH A SOUTHERLY FLOW DEVELOPING IN THE
LLVLS. 850MB THERMAL RIDGE OF 6 TO 8 DEG C WILL ADVECT OVERHEAD AND
WITH MINIMAL SOLAR SHIELDING WILL PROVIDE AN OPPORTUNITY FOR SFC
TEMPS TO WARM INTO THE 60S.
WEDNESDAY...
GUIDANCE CONTINUES TO DEMONSTRATE NOISE AMONGST OPERATIONAL MODELS.
LATEST NAM/GFS ARE SHOWING SOME MODEL CORRECTIONS ARE TAKING PLACE
WITH A SLIGHTLY FASTER REGIME IN BRINGING THE FRONTAL BOUNDARY
ACROSS THE REGION EARLIER IN THE DAY WED. CONFIDENCE REMAINS HIGH
THAT PRECIP WILL REMAIN WEST OF THE CWFA THROUGH MOST OF WED...WITH
A STEADY MOISTURE ADVECTION INTO THE REGION BY WED EVENING. THIS
COUPLED WITH A THERMAL RIDGE ALOFT REMAINING IN PLACE TO PROVIDE SFC
TEMPS IN THE MID 60S. SOME LOCATIONS ALONG AND SOUTH OF LA SALLE TO
KANKAKEE COUNTY LINE COULD PUSH THE UPPER 60S.
THURSDAY...
STUBBORN FRONTAL BOUNDARY ARRIVES EARLY THUR AND SLOWLY PUSHES
THROUGH THE CWFA TONIGHT. 850MB THERMAL TROUGH OF -2 TO 0 DEG C
ARRIVES OVERHEAD AS SFC ANTI-CYCLONIC FLOW BUILDS IN FROM THE
CENTRAL PLAINS INTO THE WESTERN GREAT LAKES. THIS SHOULD BRING AN
END TO THE PRECIP BY THUR EVENING...WITH DRY AIR TO CLOSE OUT THE
WEEK. TEMPERATURES THUR WILL STRUGGLE TO WARM BEYOND THE UPPER 40S
TO LOWER 50S.
FRIDAY THROUGH SUNDAY...
ENSEMBLES HAVE MAINTAINED SOME LEVEL OF CONSISTENCY WITH RESPECT TO
MINIMAL SPREAD IN THE 500MB WAVE PATTERN AS A RIDGE PUSHES EAST
ACROSS THE GREAT LAKES REGION FRI/SAT. THIS SHOULD KEEP DRY AIR IN
PLACE THROUGH AT LEAST FRI...WITH JUST SLIGHT CHANCE OF PRECIP FOR
SAT AFTN AS OPERATIONAL MODELS CONTINUE TO ADVERTISE A POTENT
SHORTWAVE DEVELOPING OVER THE SOUTHERN PLAINS AND RAPIDLY
STRENGTHENING AND LIFTING NORTHEAST. THE TREND HAS BEEN FOR A
FURTHER NORTHWEST PATH OF THIS SYSTEM...WHICH MAY END UP PREVENTING
PRECIP FROM ARRIVING SAT AFTN AND PUSHING IT INTO SUN. THIS SCENARIO
IS GROWING IN CONFIDENCE AS THE DOWNSTREAM RIDGE MAY BE SLIGHTLY
STRONGER THAN OPERATIONAL SOLUTIONS ARE ANTICIPATING. TEMPERATURES
THROUGH THE EXTENDED PERIODS ARE EXPECTED TO BE MAINLY IN THE
50S...POSSIBLY REACHING 60 DEG ON SAT. OVERNIGHT LOWS WILL MAINLY BE
IN THE 30S TO A FEW NIGHTS IN THE LOWER 40S.
BEACHLER
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 04Z...
* GUSTY SOUTHERLY WINDS TUESDAY. CMS
//DISCUSSION...UPDATED 04Z...
WITH MAINLY CLEAR SKIES AND LIGHT/CALM WINDS...TEMPS HAVE QUICKLY
DROPPED DOWN TO THE DEWPOINTS WITH VISIBILITIES STARTING TO DROP
DOWN INTO THE 6-8SM RANGE. STILL NOT ANTICIPATING ANY WIDESPREAD
FOG PROBLEMS...BUT HAVE INCLUDED PREVAILING LIGHT FOG AT RFD/DPA.
WITH THE POSSIBILITY OF MVFR VIS AT TIMES...LIKELY FROM SHALLOW
GROUND FOG. CMS
PREVIOUS 00Z DISCUSSION...
SOUTHERN END OF A LARGE AREA OF 3-4KFT CIGS STEADILY MOVING EAST
ACROSS NORTHERN IL EARLY THIS EVENING. A FEW LOCATIONS...MAINLY IN
WI REPORTING HIGH MVFR CIGS. EXPECT THE BACK EDGE OF THIS DECK OF
CLOUDS TO BE EAST OF ORD/MDW BY 02Z OR SO...THOUGH COULD STILL BE
A FEW HRS OF FEW/SCT CLOUDS AND WILL NEED TO MONITOR TRENDS WITH
THE EVENING UPDATES. OTHERWISE ONLY HIGH/MID CLOUDS EXPECTED FOR
THE REMAINDER OF THE PERIOD. COULD BE SOME PATCHY FOG AROUND
OVERNIGHT THROUGH SUNRISE BUT DOESN/T APPEAR AS FAVORABLE AS IT
WAS THIS MORNING AND NOT PLANNING ANY MENTION AT THIS TIME.
A LARGE RIDGE OF HIGH PRESSURE JUST TO THE EAST WILL CONTINUE TO
SLOWLY DRIFT EAST TONIGHT. WEST/SOUTHWEST WINDS UNDER 10KTS SHOULD
TURN MORE SOUTHERLY THROUGH THE NIGHT WITH SPEEDS 5KTS OR LESS. BY
MORNING...A LARGE TROUGH OF LOW PRESSURE OVER THE PLAINS WILL BE
SLOWLY SHIFTING EAST...TIGHTENING THE GRADIENT BETWEEN THE
DEPARTING RIDGE. AS THE LOW LEVELS BEGIN TO MIX IN THE MID/LATE
MORNING HRS...EXPECT GUSTS IN THE 20KT RANGE FOR MOST OF THE
AFTERNOON...DIMINISHING SOME WITH SUNSET TUESDAY. CMS
//ORD AND MDW CONFIDENCE...UPDATED 04Z...
* MEDIUM CONFIDENCE REGARDING WIND SPEEDS/GUSTS TUESDAY. CMS
//OUTLOOK FOR ORD/MDW FOR 12Z WEDNESDAY-12Z MONDAY...UPDATED 00Z...
WEDNESDAY...COLD FRONT/WIND SHIFT TO THE NORTH LATE AFTERNOON/EARLY
EVENING. SHOWERS DEVELOPING LATE AFTERNOON/EARLY EVENING. MVFR CIGS
DEVELOPING IN THE EVENING.
THURSDAY...MVFR CIGS/SHOWERS IN THE MORNING...VFR IN THE AFTERNOON.
FRIDAY...VFR.
SATURDAY AND SUNDAY...SLIGHT CHANCE OF SHOWERS.
&&
.MARINE...
221 PM CDT
SOUTHERLY WINDS WILL BE ON THE INCREASE TONIGHT INTO TUESDAY AS AN
AREA OF LOW PRESSURE MOVES ACROSS SOUTHERN CANADA. THIS LOW WILL
PUSH A COLD FRONT FROM THE NORTHERN PLAINS ACROSS THE UPPER
MISSISSIPPI VALLEY BY TUESDAY. THIS COLD FRONT WILL CONTINUE
EASTWARD ACROSS LAKE MICHIGAN LATE WEDNESDAY AND WEDNESDAY NIGHT. AT
THE SAME TIME...AN AREA OF LOW PRESSURE IS FORECAST TO DEVELOP ALONG
THIS FRONT ACROSS THE SOUTHERN PLAINS. THIS LOW WILL THEN TRACK
EASTWARD ACROSS MISSOURI AND ILLINOIS WEDNESDAY NIGHT AND THURSDAY.
IT APPEARS THAT THE COMBINATION OF THE COLD AIR MOVING OVER THE LAKE
BEHIND THE FRONT...COMBINED WITH A STRENGTHENING PRESSURE GRADIENT
ASSOCIATED WITH THE DEVELOPING SURFACE LOW...WILL PRODUCE A
PERIOD OF STRONG NORTH TO NORTHEASTERLY WINDS ACROSS LAKE MICHIGAN
WEDNESDAY INTO THURSDAY. SOME GALE FORCE WINDS ARE POSSIBLE DURING
THIS PERIOD...ESPECIALLY OVER THE SOUTH HALF OF THE LAKE.
HOWEVER...DUE TO ABOVE AVERAGE UNCERTAINTY ON THE EXACT TIMING AND
TRACK OF THE SURFACE LOW...I AM NOT CONFIDENT ENOUGH TO INCLUDE
WINDS OF THIS MAGNITUDE AT THIS TIME.
FOLLOWING THIS STORM...A SURFACE HIGH WILL BUILD IN ACROSS THE GREAT
LAKES ON THURSDAY NIGHT AND FRIDAY. THIS WILL PRODUCE A PERIOD OF
LIGHTER WINDS BEFORE SOUTHERLY WINDS INCREASE AGAIN INTO NEXT
WEEKEND AHEAD OF A POTENT STORM SYSTEM EXPECTED DEVELOP ACROSS THE
CENTRAL ROCKIES BEFORE LIFTING NORTH NORTHEAST WARD ACROSS THE UPPER
MISSISSIPPI VALLEY.
KJB
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
LMZ745...10 AM TUESDAY TO 10 PM TUESDAY.
&&
$$
