845 PM CDT
LAST LITTLE SHOWER CONTINUES TO FADE OUT ACROSS NORTHERN LAKE
COUNTY INDIANA AT THIS HOUR WITH A FEW LINGERING SHOWERS ACROSS
SOUTHERN WISCONSIN AND OUT OVER THE LAKE TO THE NORTH AND EAST. CLOUD
COVER HAS DIMINISHED ACROSS A GOOD CHUNK OF THE NORTHERN AND
WESTERN CWA WITH HIGH CIRRUS STILL LINGERING ACROSS THE FAR
SOUTHERN CWA FROM PONTIAC TO RENSSELAER. ANOTHER AREA OF CIRRUS IS
RACING EASTWARD ACROSS CENTRAL AND WESTERN IOWA AND WILL BE
OVERHEAD BY LATE EVENING. THIS WILL LIKELY BRING A PERIOD OF
STEADIER TEMPS EARLY TONIGHT BUT EXPECT THE CLOUDS TO MOVE OFF TO
THE EAST BY EARLY MORNING AS IT THINS. THEREFORE SHOULD SEE A DROP
OFF IN TEMPS PRIOR TO DAYBREAK. HAVE TWEAKED HOURLY TEMP TRENDS TO
ACCOUNT FOR THIS AS WELL AS ERRATIC TEMPS CURRENTLY IN PLACE
THANKS TO THE EARLIER SHOWER ACTIVITY. WILL MAINTAIN THE FROST
ADVISORY BUT LOWER TEMPS IN THE TYPICALLY COOL ROCHELLE TO AURORA
CORRIDOR BY A FEW DEGREES.
MDB
//PREV DISCUSSION...
327 PM CDT
MAIN CONCERN FOR THE REMAINDER OF THE AFTERNOON AND INTO THE
EVENING WILL FOCUS OF THE SCATTERED SHOWERS THAT DEVELOPED THIS
AFTERNOON. AFTER SKIES CLEARED OUT EARLIER TODAY...SUNSHINE AND
COLD AIR ALOFT GENERATED VERY STEEP LAPSE RATES...QUICKLY
TRIGGERING SCATTERED SHOWERS OVER NRN IL. GIVEN THE STRONG
INSTABILITY AND COLD AIR ALOFT...OCCASIONAL GRAUPEL WILL BE
POSSIBLE WITH THE STRONGER SHOWERS. SHOWERS SHOULD DISSIPATE
AROUND SUNSET.
AFTER SUNSET...AS SKIES CLEAR OUT AND SFC HIGH PRESSURE BUILDS
ACROSS THE CWA...WINDS WILL QUICKLY BECOME LIGHT AND VARIABLE.
WITH A DRY AIR MASS IN PLACE...AND DEW POINTS IN THE LOW
30S...TEMPERATURES ACROSS MUCH OF THE AREA WILL ALSO DROP INTO
THE LOWER 30S. THUS...FROST IS LIKELY TONIGHT FOR MUCH OF THE
CWA. IMMEDIATE LAKEFRONT AND LOCATIONS AWAY FROM HEAVILY
URBANIZED AREAS WILL BE MOST PRONE TO FROST.
BEGINNING TOMORROW...THE REGION WILL BE IMPACTED BY A SERIES OF
NORTHERN STREAM SHORTWAVES WHICH WILL BRING PERIODS SHOWERS TO AT
LEAST PORTIONS OF THE CWA OVER THE NEXT SEVERAL DAYS.
THE FIRST IN THE SERIES OF THESE SYSTEMS WILL TRACK ACROSS
SOUTHERN CANADA...DRAGGING A WEAK COLD FRONT ACROSS THE AREA
FRIDAY AFTERNOON AND EVENING. WITH THE STRONGEST FORCING LIKELY
TO BE WELL TO THE NORTH...THE NORTHERN TIER COUNTIES WILL BE MOST
SUSCEPTIBLE TO ANY PCPN. BY FRIDAY NIGHT...THE FOCUS OF PCPN WILL
TRANSITION TO LAKE EFFECT RAIN SHOWERS FOR LAKE AND PORTER
COUNTIES IN NWRN INDIANA AND OVER LAKE MICHIGAN. AS THE COLDEST
AIR ASSOCIATED AN UPPER TROUGH MOVES ACROSS THE LAKE FRIDAY
NIGHT...THERE WILL ONCE AGAIN BE A SLIGHT CHANCE FOR SOME THUNDER
TO ACCOMPANY THE HEAVIER LAKE EFFECT SHOWERS. BY SATURDAY
MORNING...THE UPPER TROUGH WILL SHIFT OFF TO THE EAST AS A RIDGE
BUILDS ACROSS THE MISSISSIPPI VALLEY AND INTO THE UPPER MIDWEST.
EVEN COOLER AIR WILL OVERSPREAD THE AREA BY SATURDAY MORNING.
TEMPERATURES ARE EXPECTED TO DROP INTO THE UPPER 20S TO LOWER 30S
ACROSS ALL OF THE CWA...WITH THE EXCEPTION OF THE IMMEDIATE LAKE
FRONT AND DOWNTOWN CHICAGO. LOCATIONS WEST OF THE FOX VALLEY AND
NORTH OF I-80 MAY SEE TEMPERATURES DROP INTO THE UPPER 30S...SO A
FREEZE WARNING MAY BE REQUIRED FOR THE NORTHWESTERN PORTIONS OF
THE CWA. THE REMAINDER OF SATURDAY AND INTO SATURDAY NIGHT SHOULD
BE QUIET. THE NEXT UPSTREAM SYSTEM SHOULD MOVE ACROSS THE UPPER
MISSISSIPPI VALLEY BY SUNDAY MORNING. THE TRACK OF THIS SYSTEM
SHOULD BE MORE SOUTHERLY THAN THE PREVIOUS...WITH THE MAIN SFC LOW
TRACKING ALONG THE WISCONSIN BORDER. THUS SHOWERS SHOULD BE MORE
WIDESPREAD WITH GRAUPEL LIKELY AGAIN SUNDAY AND SUNDAY NIGHT.
MONDAY SHOULD BE QUIET...BUT ANOTHER SYSTEM IS BEING ADVERTISED
BY THE LONGER RANGE MODELS FOR THE MIDDLE OF NEXT WEEK. WHILE THE
MODELS ARE IN RELATIVELY GOOD AGREEMENT ON TRACK...TIMING AND
STRENGTH OF THE FIRST TWO SYSTEMS...THE GFS AND ECMWF ARE ABOUT
12-18 HOURS OUT OF PHASE AND THE ECMWF HAS MUCH HIGHER AMPLITUDE
TO THE UPPER TROUGH. IN THE ABSENCE OF A GOOD MODEL
CONSENSUS...WILL ONLY CARRY CHANCE POPS. WHILE THERE CERTAINLY
SHOULD BE MORE PCPN FOR MIDWEEK...THE TIMING IS HIGHLY
QUESTIONABLE.
KREIN
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 04Z...
POTENTIAL FOR MIFG AND/OR BCFG DURING PREDAWN.
TRS
//DISCUSSION...UPDATED 02Z...
WITH THE MODERATE SHOWER THAT PASSED OVER KORD AND KMDW 1830-1930
LOCAL WETTING GROUND AFTER SUNSET AND WEAK SFC PRES GRADIENT SO
LITTLE IF ANY WIND...MAY SEE SOME MIFG OR BCFG AFTER THE CS OVER
SRN WI...SE MN...AND IA CLEARS OUT OF LOCAL AREAS 08-09Z AND GOOD
RADIATIONAL COOLING OF BOUNDARY LAYER SETS IN.
PREVIOUS DISCUSSION...00Z...
COLD POOL ALOFT ALLOWED VFR CU CIGS AND SCT SHRA TO DEVELOP WITH
HEATING TODAY OVR THE UPR MIDWEST S TO THE MID MS VALLEY. WITH
SUNSET SATELLITE SHOWED BOTH DECREASING CLOUDS AND SHRA ACTIVITY.
THIS TREND TO CONT THIS EVE AS A MINOR SHORT WAVE TROF EXTENDING
FM SRN LK MI SWWRD TO NE MO MOVE E OF THE LOCAL AREA OVR NEXT FEW
HRS.
UPSTREAM IS A MID LVL SHORT WAVE IS DROPPING QUICKLY SEWRD OVER
NW IA...NE...NW KS WITH AN UPR LVL TROF OVER ERN PORTIONS OF MT
AND WY. NRN PORTION OF BAROCLINIC LEAF WITH CNTRL PLAINS SHORT WAVE
TO BRUSH ACROSS THE LOCAL AREA OVERNIGHT AS THE SHORT WAVE CONTS
SEWRD.
AS UPR LVL SHORT WAVE TROF MOVES TO OVR THE UPPER MS AND MID MO
RIVER VALLEYS DURG FRI MORNING EXPECT TO SEE AN INCREASE IN
STRATOCU AS FLOW BACKING TO SW AND INCREASING ADVECTS IN MOISTURE
CURRENTLY OVR MO...AR...OK. ALSO EXPECT TO SEE MID LVL CLOUDS INC
DURG THE AFTERNOON AS H5 TROF MOVS OVR SRN WI...NW IL...NE MO.
POTENTIAL FOR SOME -SHRA LATE IN THE AFTERNOON WITH UPPER TROF
JUST UPSTREAM BUT QPF PROGS AND MOS POP NUMBERS DOWNPLAYING
THREAT SO HAVE LEFT OUT OF THIS SET OF TAFORS AS LOW CONFIDENCE
AND IF DOES OCCUR WOULD BE LATE IN FCST PD.
TRS
//ORD AND MDW CONFIDENCE...UPDATED 04Z...
* HIGH IN NIL OR LGT-VRB WINDS THRU THE OVERNIGHT AND EARLY AM.
* MODERATE IN NO WDSPRD OBSTRUCTIONS TO VSBY PREDAWN-EARLY AM.
TRS
//OUTLOOK FOR ORD/MDW FOR 12Z SAT-12Z THU...UPDATED 00Z...
SAT...VFR. WX NIL.
SUN...PREVAILING VFR...CHC SHRA WITH LCL MVFR
MON...VFR. WX NIL.
TUE...VFR. WX NIL.
WED...VFR...SLGT CHC -SHRA.
TRS
&&
.MARINE...
254 PM CDT
RIDGE OF HIGH PRESSURE WILL BUILD INTO THE WESTERN GREAT LAKES
REGION THIS EVENING AND CONTINUE OVERNIGHT...GRADUALLY DRIFTING
EAST. AS THE RIDGE DRIFTS EAST EARLY FRIDAY MORNING...WINDS WILL
TURN SOUTHWESTERLY OVER LAKE MICHIGAN. A DEVELOPING LOW PRESSURE
SYSTEM WILL THEN SLIDE EAST/SOUTHEAST ACROSS THE NORTHERN PLAINS AND
ARRIVE ACROSS THE WESTERN GREAT LAKES REGION FRIDAY NIGHT/SATURDAY.
SOUTHWEST WINDS AHEAD OF THIS FRONTAL BOUNDARY AND LOW PRESSURE
SYSTEM WILL INCREASE TO 15 TO 25 KT...THEN DECREASE SATURDAY
AFTERNOON. THEN YET ANOTHER STRONGER LOW PRESSURE SYSTEM IS POISED
TO ARRIVE ACROSS THE GREAT LAKES REGION SUNDAY...AND BRING INCREASED
WINDS TO POSSIBLY 30KT FOR MANY PORTIONS OF THE LAKE SUNDAY. THIS
MAY CREATE SMALL CRAFT CONDITIONS FOR THE NEARSHORE WATERS OF
ILLINOIS/INDIANA SUNDAY FROM INCREASED WINDS.
BEACHLER
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...FROST ADVISORY...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-ILZ010-
ILZ011-ILZ012-ILZ019-ILZ020-ILZ021-ILZ023-ILZ032-ILZ033-
ILZ039 UNTIL 7 AM FRIDAY.
IN...FROST ADVISORY...INZ010-INZ011-INZ019 UNTIL 7 AM FRIDAY.
LM...NONE.
&&
$$
