343 PM CDT
FOR THE REMAINDER OF THE AFTERNOON AND EVENING...MILD CONDITIONS
CONTINUE ACROSS NORTHERN ILLINOIS AND NORTHWEST INDIANA.
TEMPERATURES WILL CONTINUE TO INTO THE MIDDLE TO UPPER 70S ACROSS
THE NORTHERN PORTIONS OF THE CWA NEAR THE WISCONSIN BORDER...TO
AROUND 80 TO THE FAR SOUTH. A WEAK LAKE BREEZE HAS PUSHED INLAND
FROM DOWNTOWN CHICAGO TO NWRN LAKE COUNTY...ALLOWING THE LAKE FRONT
LOCATIONS NORTH OF CHICAGO TO REMAIN A LITTLE COOLER...WITH HIGHS
TOPPING OUT TODAY IN THE LOWER 70S. OVERNIGHT...EXPECT SKIES TO BE
MOSTLY CLEAR. AS SFC DEWPOINTS HAVE REBOUNDED INTO MIDDLE 50S
TODAY...EXPECT THAT OVERNIGHT LOWS WILL NOT BE QUITE AS LOW AS
RECENTLY...THIS TEMPERATURES ONLY DROPPING GENERALLY INTO THE MIDDLE
50S.
THE UPPER LEVEL PATTERN IS FINALLY SHOWING SOME SIGNS OF EASTWARD
PROGRESSION...SIGNALING A CHANGE IN THE WEATHER. THE PERSISTENT
UPPER LEVEL RIDGE IS BEGINNING TO MOVE EASTWARD AS AN UPPER LOW
RIDES NWD THROUGH THE NRN PLAINS AND INTO SCNTRL CANADA. CONDITIONS
ACROSS THE AREA SHOULD REMAIN PLEASANT FOR A COUPLE MORE DAYS AS THE
UPPER RIDGE SLOWLY BUILDS EWD AND HIGH AMPLITUDE...FULL-LATITUDE
TROUGHING DEVELOPS OVER THE CNTRL PLAINS. EXPECT LITTLE CHANGE IN
THE SENSIBLE WEATHER CONDITIONS FOR TUESDAY AS A RIDGE OF SFC HIGH
PRESSURE EXTENDS FROM SERN CANADA...THROUGH THE ERN GREAT LAKES...TO
THE MIDDLE MISSISSIPPI VALLEY. LOW LEVEL FLOW WILL REMAIN
SELY-SSELY THROUGH THE DAY...WITH FOR TUESDAY REMAINING VERY SIMILAR
TO RECENT DAYS...WITH ONLY PERHAPS SOME INCREASING MID AND HIGH
CLOUDINESS.
WEDNESDAY IS SHAPING UP TO BE CHANGE DAY AS A COLD FRONT ASSOCIATED
WITH THE APPROACHING...DEVELOPING TROUGH TRACKS THROUGH THE CNTRL
PLAINS. THERE ARE STILL SOME MODEL DISAGREEMENTS...ESPECIALLY WITH
THE TIMING OF THE FRONTAL PASSAGE. HAVE GENERALLY FOLLOWED THE
GFS/SREF SOLUTION WHICH HAS BEEN VERY CONSISTENT IN TIMING OF THE
FROPA WITH RECENT RUNS...ALTHOUGH OVERALL...THE TIMING DIFFERENCES
AMONG THE MODELS IS NOT VERY LARGE. GENERALLY...EXPECT THE FROPA TO
OCCUR IN THE LATE EVENING HOURS. HAVE NOT MADE MUCH CHANGE TO THE
ASSOCIATED PCPN FORECAST AND STILL EXPECT A PERIOD OF SHOWERS
WITH...WITH PCPN POSSIBLY MOVING INTO THE ROCKFORD AREA AS EARLY AS
LATE WEDNESDAY AFTERNOON. EXPECT THAT THE PCPN WILL NOT CLEAR THE
EASTERN PORTIONS OF THE CWA UNTIL LATE THURSDAY NIGHT OR FRIDAY
MORNING. STILL EXPECT THAT THERE MAY BE A CHANCE FOR SOME
ISOLD...EMBEDDED THUNDER WITH THE FRONT...BUT INSTABILITY IS
EXPECTED TO BE RATHER MODEST...SO HAVE TRIMMED BACK THE SLIGHT
CHANCE THUNDER AREAS IN THE GRIDS...AND HAVE CONFINED IT MORE
CLOSELY WITH THE FRONTAL BOUNDARY.
TEMPERATURES SHOULD DROP OFF SIGNIFICANTLY FOLLOWING THE FROPA WITH
850MB TEMPS DROPPING TO ARND 2C BY FRIDAY MORNING. BY
THURSDAY...HIGHS SHOULD BE IN THE MIDDLE 60S. AS THE COLD ADVECTION
REALLY KICKS IN OVERNIGHT THURSDAY AND FRIDAY...HIGHS BY FRIDAY
SHOULD BE MUCH MORE SEASONABLE...IN THE UPPER 50S TO LOWER 60S.
FOR THE REMAINDER OF THE LONGER TERM FORECAST PERIOD...FOR SATURDAY
THROUGH MONDAY...CONDITIONS WILL MODERATE THROUGH THE WEEKEND AS
ANOTHER UPPER RIDGE BUILDING OVER THE WRN CONUS MOVES OUT OVER THE
PLAINS. RISING HEIGHTS OVER THE MIDWEST SHOULD ALLOW FOR GENERALLY
DRY WEATHER THROUGH THE WEEKEND AND TEMPERATURES REBOUNDING BACK
INTO MIDDLE 60S...TO LOWER 70S BY SUNDAY.
KREIN
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 02Z...
* WIND DIRECTION/DISSIPATING WEAK LAKE BREEZE THIS EVENING.
RATZER
//DISCUSSION...UPDATED 00Z...
DECREASING SOUTHERLY SURFACE WINDS HAVE FINALLY ALLOWED WEAK LAKE
BREEZE TO PUSH INLAND ACROSS LAKE AND NORTHEAST COOK COUNTIES IN
NORTHEAST ILLINOIS OVER THE PAST COUPLE OF HOURS...PUSHING THOUGH
KPWK AND SHIFTING WINDS TO THE EAST THOUGH AT LESS THAN 5 KTS.
RADAR REFLECTIVITY TRENDS FROM KLOT/TORD/TMKE HAVE SHOWN QUICK
LOSS OF DEFINITION IN THE LAKE BREEZE BOUNDARY HOWEVER...WHICH
SUGGESTS IT WILL LIKELY DISSIPATE RATHER QUICKLY WITH THE OVERALL
SURFACE WIND FIELD SETTLING INTO A LIGHT SOUTHEAST CONFIGURATION
THIS EVENING. GUIDANCE AND CURRENT SYNOPTIC PRESSURE FIELD
SUGGESTS THIS WILL LIKELY REMAIN IN PLACE OVERNIGHT...BEFORE
BECOMING A BIT MORE SOUTH AGAIN TUESDAY MORNING WITH RENEWED
MIXING AFTER SUNRISE. WIND DIRECTION FORECAST BECOMES A LITTLE
MORE QUESTIONABLE TUESDAY AFTERNOON/EVENING AS GRADIENT AGAIN
BECOMES RATHER WEAK. 18Z WRF MODEL FORECASTS SUGGEST A SHIFT MORE
TO THE EAST OR EAST-SOUTHEAST LATER IN THE AFTERNOON...THOUGH
THERE IS SOME DIFFERENCE IN VARIOUS GUIDANCE SOLUTIONS. WINDS
SHOULD REMAIN 10 KTS OR LESS THROUGH THE PERIOD HOWEVER.
OTHERWISE...VFR CONDITIONS EXPECTED THROUGH THE PERIOD. WEAK COLD
FRONT OR CONVERGENCE BOUNDARY DRIFTS EAST ACROSS THE MISSISSIPPI
VALLEY TUESDAY BRINGING THE POTENTIAL FOR SOME SHOWERS MAINLY TO
KRFD AREA DURING THE AFTERNOON. CONFIDENCE FAIRLY LOW HOWEVER...
AS PRECIPITATION WILL BE FIGHTING RELATIVELY WEAK FORCING AND DRY
LOW LEVELS. HAVE THUS INDICATED ONLY A PROB30 AT KRFD...AND KEPT
CHICAGO TERMINALS DRY AT THIS POINT. WHILE THERE IS SOME ELEVATED
INSTABILITY NOTED IN WRF FORECAST SOUNDINGS AT RFD IN THE
AFTERNOON...OVERALL THUNDER POTENTIAL LOOKS PRETTY MINIMAL AGAIN
WITH LESS THAN IMPRESSIVE FORCING/MOISTURE.
RATZER
//ORD AND MDW CONFIDENCE...UPDATED 02Z...
* MEDIUM-HIGH CONFIDENCE IN WIND FORECAST. HIGH CONFIDENCE ALL
OTHER ELEMENTS.
RATZER
//OUTLOOK FOR ORD/MDW FOR 12Z WEDNESDAY-12Z MONDAY...UPDATED 00Z...
WEDNESDAY AND THURSDAY...OCCASIONAL SHRA WITH MVFR OR EVEN BRIEF IFR
POSSIBLE ESPECIALLY WED NGT/THURS MORNING.
FRIDAY AND SATURDAY...SLGT CHC SHRA FRI...OTHERWISE VFR.
SUNDAY...SLGT CHC SHRA WITH MVFR CIGS.
RATZER
&&
.MARINE...
204 PM CDT
THE MAIN CONCERN DURING THE PERIOD WILL BE THE POTENTIAL FOR A
PERIOD OF LOW END GALES ON FRIDAY AND FRIDAY NIGHT. A POTENT AREA OF
LOW PRESSURE IS EXPECTED TO DROP SOUTHEAST ACROSS THE UPPER MISSISSIPPI
RIVER VALLEY AND ACROSS THE GREAT LAKES LATER THIS WEEK. THIS
SYSTEM LOOKS TO PRODUCE A PERIOD OF SIGNIFICANT WINDS ACROSS THE
LAKE AS MUCH COLDER AIR SPILLS ACROSS THE REGION.
KJB
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&
$$
