321 PM CDT
MAIN CONCERN FOR THE NEXT FEW DAYS WILL FOCUS ON LAKE EFFECT RAIN
SHOWERS DEVELOPING TONIGHT AND THEN TRANSITIONING TO TEMPERATURES
FOR THE NEXT FEW DAYS.
FOR THE REMAINDER OF THE AFTERNOON AND TONIGHT...THE STRONG COLD
FRONT HAS CLEARED CWA AND IS APPROACHING THE OHIO VALLEY. A MUCH
COOLER AIRMASS HAS OVERSPREAD OVER THE REGION AS PREVAILING
NORTHERLY WINDS SET UP OVER THE MIDWEST AND GREAT LAKES REGIONS.
SOME LIGHT RAIN MAY LINGER OVER THE FAR SOUTHERN COUNTIES THROUGH
THE EVENING...PERHAPS BEING ENHANCED BY A STRONG JET STREAM DIRECTLY
OVERHEAD.
OVERNIGHT TONIGHT AND INTO TOMORROW...THE MAIN PCPN CONCERN WILL
FOCUS ON LAKE EFFECT RAINSHOWERS OVER FAR NERN IL/NWRN INDIANA. HAVE
MADE LITTLE CHANGE TO THE GOING FORECAST IN THIS RESPECT AS THE
LATEST MODEL RUNS REMAIN RELATIVELY CONSISTENT WITH A NORTHERLY
FETCH OF COOLER AIR TO PERSIST THROUGH LATE THURSDAY AFTERNOON. AS
LAKE WATER TEMPS REMAIN RELATIVELY WARM COMPARED SFC TEMPS...AND SFC
TO 850MB DELTA-T OF 14-15C...THE LOW LEVEL ENVIRONMENT WILL BE
CONDUCIVE TO LAKE EFFECT PCPN. WILL ALSO MAINTAIN THE SLIGHT CHANCE
FOR THUNDER OVER FAR SRN LAKE MICHIGAN...ESPECIALLY FOR
THURSDAY...WHEN THE THE COOLEST AIR ALOFT...ASSOCIATED WITH A
PASSING UPPER TROUGH...WILL BE OVER LAKE MICHIGAN. WHILE THE ACTUAL
CHANCES FOR THUNDER WILL BE LOW...THE STEEP LAPSE RATES WILL AT
LEAST BE CONDUCIVE TO OCCASIONAL LOCALLY HEAVIER SHOWERS MIXING WITH
SOME GRAUPEL.
BY THURSDAY NIGHT...THE UPPER TROUGH WILL PASS TO THE EAST AND LOW
LEVEL FLOW WILL BEGIN TO BACK MORE WESTERLY...SHIFTING THE FOCUS OF
ANY REMAINING LAKE EFFECT SHOWERS OVER LOWER MICHIGAN AND NRN
INDIANA. NWRN PORTER COUNTY SHOULD BE THE ONLY PORTION OF THE LOCAL
CWA WHICH MAY SEE SOME PCPN LINGERING INTO THURSDAY EVENING.
THE FORECAST ELEMENT OF CONCERN WILL SHIFT TO TEMPERATURES...
ESPECIALLY FOR FRIDAY MORNING AND SATURDAY MORNING. MUCH OF THE
LINGERING LOW LEVEL CLOUD COVER SHOULD FINALLY CLEAR OUT THURSDAY
NIGHT AND INTO THE WEEKEND. THIS WILL ALLOW TEMPERATURES TO RADIATE
INTO THE LOWER 30S FOR MIN TEMPS FRIDAY MORNING AND SATURDAY
MORNING. DO NOT ANTICIPATE ANY SGFNT CHANCES FOR PCPN THROUGH
SATURDAY AS THE MAIN TRACK OF SHORT WAVE ENERGY WILL BE THROUGH THE
UPPER GREAT LAKES.
THE NEXT CHANCE FOR ANY PCPN WILL NOT COME UNTIL SUNDAY. THE LONGER
TERM MODELS ARE ADVERTISING A STRONG SHORT WAVE TO DROP OUT OF
CANADA AND INTO THE UPPER MISSISSIPPI VALLEY. THE LATEST 12Z RUNS OF
THE GFS AND ECMWF ARE RELATIVELY CONSISTENT WITH THE TIMING OF THE
SYSTEM...THOUGH THE GFS IS TRENDING QUITE A BIT DEEPER.
HOWEVER...THE STRENGTH DIFFERENCES WILL LIKELY HAVE LITTLE IMPACT ON
THE SENSIBLE WEATHER FORECAST. SINCE THE MAIN FORCING FROM THE
SYSTEM SHOULD BE OVER WISCONSIN AND NORTHERN LAKE MICHIGAN...WILL
ONLY CARRY SLIGHT CHANCE POPS FOR SUNDAY AT THIS TIME. FOR
TEMPERATURES...EXPECT HIGHS TO BE RELATIVELY CONSISTENT THROUGH
SATURDAY WITH HIGHS IN THE LOWER TO MIDDLE 50S. THERE SHOULD BE A
GRADUAL WARMING TREND SETTING UP BY EARLY NEXT WEEK. WITH THE UPPER
TROUGH MOVING OFF TO THE EAST...AN UPPER RIDGE IS EXPECTED TO BUILD
OVER THE UPPER MISSISSIPPI VALLEY AND INTO THE MIDWEST. SO...BY
EARLY NEXT WEEK...TEMPERATURES MAY REBOUND BACK INTO THE UPPER 50S
TO LOWER 60S.
KREIN
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 20Z...
* MVFR CIGS
* -DZ POTENTIAL
SHEA
//DISCUSSION...UPDATED 18Z...
CIG TRENDS CONTINUE TO BE EVER SO SLOW TO CRACK THE 015
MARK...OTHERWISE THE MVFR LOW CLOUD SCENARIO WITH THE COLD AIR
ADVECTION REGIME CONTINUES. CIGS WILL IMPROVE MORE THROUGH THE
EVENING AND LIKELY BECOME VFR FOR SOME TIME THIS EVENING. POCKETS OF
LIGHT DRIZZLE ARE AROUND THE TERMINALS...BUT WILL LIKELY NOT CAUSE
ANY PROBLEMS THROUGH THE EVENING HOURS. CHANCES FOR SHOWERS
INCREASE AGAIN TOMORROW IN THE FORM OF LAKE EFFECT SHOWERS. FLOW
TO LIKELY BE TRANSITIONING TO 330-340 BY THE EARLY MORNING HOURS
AND NOT EXPECTING ORD TO BE IMPACTED ANYMORE AT THIS TIME AS FLOW
WILL KEEP IT TO THE EAST. MDW MAY BE CLIPPED WHILE GYY SHOULD BE HIT
BY SOME LAKE EFFECT SHOWERS.
SHEA
//ORD AND MDW CONFIDENCE...UPDATED 18Z...
* HIGH CONFIDENCE OF CIGS IMPROVING...SLOWLY
* MEDIUM TO HIGH CONFIDENCE ON TIMING OF IMPROVEMENT BEYOND 015
OVER THE NEXT HOUR OR SO...LOW ON TIMING TO VFR
* HIGH CONFIDENCE ON CONTINUED NORTH WINDS TODAY
* LOW CONFIDENCE IN -DZ IMPACTING ACROSS THE TERMINALS
SHEA
//OUTLOOK FOR ORD/MDW FOR 00Z FRIDAY-12Z WEDNESDAY...UPDATED 12Z...
THURSDAY NIGHT...CHANCE OF SHRA...OTHERWISE VFR.
FRIDAY...VFR WITH A CHANCE OF SHOWERS OVERNIGHT.
SATURDAY...VFR.
SUNDAY...VFR TO MVFR.
MONDAY...VFR.
TUESDAY...VFR.
LENNING
&&
.MARINE...
250 PM...AN AREA OF ELONGATED LOW PRESSURE EXTENDS FROM NEW YORK
SOUTHWEST INTO NORTHERN OHIO AND WILL CONTINUE MOVING EAST TONIGHT
AND OFF THE ATLANTIC COAST THURSDAY. A LARGE AREA OF HIGH PRESSURE
WILL MOVE SOUTHEAST ACROSS THE PLAINS TONIGHT THROUGH FRIDAY
MORNING AS WEAK LOW PRESSURE MOVES SOUTHEAST ACROSS ONTARIO FRIDAY
AND THEN ACROSS LAKE MICHIGAN FRIDAY NIGHT. THE PATTERN REMAINS
ACTIVE INTO NEXT WEEK AS A WEAK RIDGE OF HIGH PRESSURE MOVES
ACROSS THE LAKE SATURDAY AND THEN ANOTHER WEAK LOW MOVES SOUTHEAST
ACROSS THE LAKE SUNDAY NIGHT. CMS
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
UNTIL 3 AM THURSDAY.
&&
$$
