343 PM CDT
FOR THE REMAINDER OF THE AFTERNOON AND EVENING...THE MAIN CONCERN
WILL FOCUS ON THE AREA OF SHOWERS THAT FORMED ALONG THE MISSISSIPPI
RIVER. THE AREA OF SHOWERS HAS BEEN MAKING SOME SLOW EWD PROGRESS
AND EXPECT THAT SCT SHOWERS MAY MOVE INTO THE I-39 CORRIDOR DURG THE
EARLY EVENING HOURS. THE SHOWERS SHOULD CONTINUE EWD THROUGH THE
EVENING...BUT WILL LIKELY DISSIPATE AS THEY APPROACH THE FOX
VALLEY. WITH INCREASING LOW LEVEL MOISTURE OVER THE AREA UNDER
PERSISTENT SOUTHERLY FLOW...THE AREA HAS SEEN INCREASING LOW AND MID
CLOUD. HOWEVER...MUCH OF THIS CLOUDINESS IS DIURNAL IN NATURE AND
MUCH OF THE CLOUDINESS OVER THE ERN PORTIONS OF THE CWA SHOULD
DISSIPATE AT SUNSET. WITH THE INCREASING CLOUD COVER OVER THE WRN
PORTIONS OF THE CWA...EXPECT THAT AREA TO SEE LOWS ONLY DROP INTO
THE UPPER 50S...WHILE ERN PORTIONS OF THE CWA SHOULD RADIATE A
BIT...AND DROP INTO THE LOWER 50S...WITH THE EXCEPTION OF DOWNTOWN
CHICAGO...WHICH SHOULD REMAIN WARMER...ONLY DROPPING TO ARND 60
DEGREES.
FOR WEDNESDAY THROUGH FRIDAY...THE MAIN FORECAST CONCERN WILL BE
TIMING THE ONSET OF PCPN ASSOCIATED WITH AN APPROACHING UPPER TROUGH
AND ASSOCIATED SFC COLD FRONT...AS WELL AS...THE SPEED OF
PROGRESSION OF THE SYSTEM THROUGH THE AREA. THE LATEST MODEL
GUIDANCE IS RATHER CONSISTENT WITH RECENT RUNS WITH THE SYNOPTIC
SCALE PATTERN. THE ONLY REAL ADJUSTMENT TO THE FORECAST IS TO DELAY
THE PROGRESSION OF THE MAIN PCPN AREA ACROSS THE REGION. THE
ONGOING PCPN OVER THE WRN PORTIONS OF THE CWA IS ACTUALLY NOT PART
OF THE SYNOPTIC UPPER TROUGH AND COLD FRONT...BUT RATHER...IS
ASSOCIATED WITH A LOW LEVEL CONVERGENCE ZONE BETWEEN THE
TROUGH...CURRENTLY LOCATED OVER THE WRN PLAINS...AND A SFC LOW OVER
THE SERN CONUS. EVENTUALLY...BY TOMORROW MORNING...THE CONVERGENCE
ZONE WILL BE ABSORBED INTO THE SYNOPTIC TROUGH. EXPECT THAT
ORGANIZED PCPN WILL APPROACH THE I-39 CORRIDOR BY ARND NOON TOMORROW
AND SLOWLY PROGRESS EWD ACROSS THE CWA...LIKELY NOT REACHING ERN
IL/NWRN IN...INCLUDING THE CHICAGO METRO AREA UNTIL THE EVENING RUSH
HOURS. THERE WILL STILL BE A CHANCE FOR SOME ISOLD/EMBEDDED THUNDER
WITH THE SYSTEM...BUT EXPECT THAT ANY THUNDER SHOULD BE CONFINED TO
THE SFC FRONTAL ZONE. LOW LEVEL INSTABILITY IS RATHER MODEST...BUT
PERSISTENT WARM ADVECTION AND ISENTROPIC LIFT SHOULD BE CONDUCIVE TO
A LEAST SOME THUNDER. TEMPERATURES TOMORROW WILL REMAIN
UNSEASONABLY WARM...BUT WITH INCREASING CLOUD COVER AND EXPECTED
PCPN...HIGHS WEDNESDAY WILL BE LOWER THAN RECENT DAYS...TOPPING OUT
IN THE LOWER 70S. AS MODEST COLD ADVECTION SETS UP BEHIND THE
FRONT...TEMPERATURES WILL DROP OFF INTO THE MIDDLE 60S FOR
THURSDAY. THE COLD ADVECTION WILL INCREASE FOR THURSDAY NIGHT AND
FRIDAY...WITH LOWS BY FRIDAY MORNING DROPPING INTO THE MIDDLE TO
UPPER 40S. THE URBANIZED AREAS OF THE CHICAGO METRO AREA WILL
REMAIN A BIT WARMER...REMAINING IN THE 50S. THE COOLING TREND WILL
CONTINUE INTO FRIDAY AND FRIDAY NIGHT AS AN UPPER TROUGH MOVES
THROUGH THE GREAT LAKES REGION.
FOR THE LONG TERM FORECAST PERIOD...SATURDAY THROUGH TUESDAY...THERE
IS REASONABLY GOOD CONFIDENCE IN A WARMING TREND FOR THE WEEKEND AS
UPPER RIDGING BUILDS OVER THE WRN CONUS AND HEIGHTS RISE OVER THE
CNTRL CONUS AS THE UPPER TROUGH EJECTS OUT TO THE EAST.
HOWEVER...THROUGH THE WEEKEND...THE 12Z GFS AND THE OLDER 00Z RUN OF
THE ECMWF HAD BEGUN TO SHOW SIGNIFICANT TIMING DIFFERENCES LATE IN
THE PERIOD. HOWEVER...THE OVERALL TREND THROUGH THE EXTENDED PERIOD
SHOULD BE FOR TEMPERATURES TO BE NEAR SEASONAL NORMAL LEVELS. THE
LONG RANGE GUIDANCE IS SUGGESTING SURGE OF SIGNIFICANTLY COLDER AIR
TO DROP OUT OF CANADA. BY THE MIDDLE OF NEXT WEEK...BOTH THE GFS
AND ECMWF ARE ADVERTISING 850MB TEMPERATURES IN THE -2C TO
-6C...WHICH WOULD SUGGEST HIGHS IN THE 40S AND LOWS IN THE 30S.
KREIN
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 06Z...
* PRECIP CHANCES WEDNESDAY
* LAKE BREEZE POTENTIAL IN THE AFTERNOON
SHEA
//DISCUSSION...UPDATED 06Z...
LIGHT SOUTHERLY WINDS AND VFR CONDITIONS ARE EXPECTED OVERNIGHT
FOR ALL OF THE EASTERN TERMINALS. ACROSS RFD THIS EVENING ARE THE
TAIL END OF SHOWERS THAT MOVED THROUGH EARLIER THIS EVENING. OF
CONCERN FOR RFD IS THE POTENTIAL FOR CIGS AND VIS TO TANK. WITH
THE LIGHT SHOWERS...BL MOISTURE HAS INCREASED AND IF SKIES CLEAR
OUT...WE WILL RADIATE OUT QUICKLY...AS IS SEEN AT FEP. WILL NEED
TO MONITOR FOR THOSE TRENDS...BUT AM LEANING IN THAT DIRECTION
INTO THE PREDAWN HOURS. WITH THE DRY CONDITIONS AND NO PRECIP
EAST...NO CONCERNS FOR ALL OTHER TERMINALS.
ANOTHER LAKE BREEZE IS EXPECTED THIS AFTERNOON...IN SIMILAR
FASHION TO PREVIOUS DAYS. SYNOPTIC FLOW WILL ALREADY BE OUT OF THE
SOUTH TO SOUTHEAST...AND WINDS WILL BEGIN TO PULL OUT OF THE 120
TO 130 RANGE WHEN IT PICKS UP/MOVES THROUGH. CONDITIONS ARE
EXPECTED TO DETERIORATE TOMORROW EVENING FOR ALL TERMINALS AS A
COLD FRONT BEGINS TO WORK THROUGH. CURRENT FORECAST PACKAGE IS
INTRODUCING VCSH INTO THE EVENING HOURS WITH SHOWERS OVERNIGHT.
TRENDS HAVE BEEN CONTINUALLY BRINGING THE FRONT THROUGH
SLOWER...AND MAY NEED TO TWEAK THE ONSET BY A FEW HOURS. STILL A
CONSISTENT SIGNAL THAT THE HEAVIEST OF SHOWERS /AND POTENTIALLY A
CLAP OF THUNDER/ WILL LIKELY OCCUR BEYOND 12Z ON THE 13TH. WITH
THE HEAVIEST OF ACTIVITY...EXPECT CIGS TO FALL WITH VISBY DOING
SIMILAR IN THE HEAVIEST OF SHOWERS. IFR CONDITIONS ARE
ANTICIPATED...WITH LIFR BEING A POSSIBILITY AS WELL.
SHEA
//ORD AND MDW CONFIDENCE...UPDATED 06Z...
* HIGH CONFIDENCE IN VFR CONDITIONS OVERNIGHT
* MEDIUM TO HIGH CONFIDENCE ON WIND FORECAST
* LOW CONFIDENCE ON PRECIP ONSET...HIGH ON INCREASING COVERAGE
SHEA
//OUTLOOK FOR ORD/MDW FOR 12Z THURSDAY-12Z TUESDAY...UPDATED 00Z...
* THURSDAY...SHOWERS AND ISOLATED THUNDERSTORMS. MVFR AND IFR
POSSIBLE.
* FRIDAY...SLIGHT CHANCE SHRA...OTHERWISE VFR.
* SATURDAY...VFR.
* SUNDAY AND MONDAY...SLIGHT CHANCE SHRA...OTHERWISE VFR.
BMD
&&
.MARINE...
152 PM CDT
THE MAIN CONCERN DURING THE PERIOD CONTINUES TO REVOLVE AROUND THE
STRONG AUTUMN STORM SYSTEM THAT IS EXPECTED TO PUSH ACROSS LAKE
MICHIGAN LATE THURSDAY INTO FRIDAY. LOW PRESSURE NOW TAKING SHAPE
ACROSS THE FRONT RANGE OF THE CANADIAN ROCKIES...WILL PUSH
SOUTHEASTWARD OVER NEXT FEW DAYS. THIS WILL MAINTAIN A SOUTH TO
SOUTHEASTERLY WIND ACROSS THE LAKE INTO THURSDAY. AS THE LOW MOVES
ACROSS THE LAKE INTO FRIDAY MORNING...THE SURFACE LOW IS EXPECTED TO
DEEPEN. THIS WILL LIKELY PRODUCE A HEALTHY PRESSURE GRADIENT ACROSS
THE WESTERN GREAT LAKES AS A SURFACE RIDGE OF HIGH PRESSURE BUILDS
IN ACROSS THE PLAINS BEHIND THIS SYSTEM. THEREFORE...A PERIOD OF
GALES APPEAR TO BE A GOOD BET ON FRIDAY AS THE SYSTEM INTENSIFIES
AND A MUCH COLD AIRMASS OVERRIDES THE LAKE.
KJB
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&
$$
