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 00Z...
* MVFR CIGS TIL 02-03Z.
* LAKE EFFECT SHRA DEVELOPING LATE TONIGHT.
TRS
//DISCUSSION...UPDATED 00Z...
MVFR CEILINGS CONTINUE TO SLOWLY IMPROVE TO VFR AS DRIER LOW
LEVEL AIR ADVECTS IN ON N FLOW. EXPECT THIS TREND TO CONTINUE
WITH KORD AND KMDW GOING VFR 02-03Z.
POS TILT MID LEVEL SHORT WAVE TROF CURRENTLY CROSSING NRN IL PER
SATELLITE...PROFILERS AND VAD WINDS. RADARS ECHOES OVER N CENTRAL
AND NE IL BUT FEEL IS ALL OR MOST ALL EVAPORATING BEFORE REACHING
SFC. CHI TERMINALS MAY SEE A FEW SPRINKLES OVER THE NEXT COUPLE
HRS BUT WILL NOT BE NEAR ENOUGH TO WET SURFACES.
WITH PASSAGE OF THIS MID LEVEL TROF LOW-MID LEVEL FLOW VEERS AND
COLD AIR ADVECTION BEGINS. FORECAST THERMAL PROFILES SHOW SUPPORT
FOR LAKE EFFECT SHRA DEVELOPING THIS EVE AND SPREAD S DOWN THE
LAKE OVERNITE. WITH ERLY COMPONENT TO THE CLOUD-BEARING WINDS LAKE
EFFECT SHOULD BE MORE TOWARD WRN SIDE OF THE LAKE BUT DO NOT
EXPECT TO REACH AS FAR W AS KMDW THO KGYY LIKELY TO SEE SHRA.
MAIN SHORT WAVE TROF RUNS FM SE MANITOBA SWWRD TO THE SRN RCKYS.
TROUGH AXIS PROGGED TO MOVE E OVER THE LOCAL AREA MID-LATE THU
MORNING. LOW LEVEL WINDS PROGGED TO BACK TO NNW-NW DURG THE
MORNING SO ANY LAKE EFFECT SHOULD SHIFT TO ERN SIDE OF LAKE.
STEEP LOW AND MID LEVEL LAPSE RATES MIDDAY THU SUPPORTIVE OF
STRATOCU CIGS DESPITE SFC DEW POINTS ONLY IN LOWE-MID 30S F.
WINDS NOT ANTICIPATED TO BE MUCH OF A PROBLEM WITH N-NW AOB 10KT
THRU THE FCST PD.
TRS
//ORD AND MDW CONFIDENCE...UPDATED 00Z...
* HIGH IN MVFR CIGS BECOMING VFR BY MID EVE.
* HIGH IN WINDS THRU NIGHT AND ON THU.
* HIGH IN LAKE EFFECT SHRA ARRIVING OVER FAR SW LAKE MI OVERNITE.
* MODERATE IN LAKE EFFECT SHRA REMAINS JUST TO E OF KMDW.
TRS
//OUTLOOK FOR ORD/MDW FOR 12Z FRIDAY-12Z WEDNESDAY...UPDATED 00Z...
FRIDAY...VFR. SLIGHT CHANCE -SHRA.
SATURDAY...VFR. WX NIL.
SUNDAY...VFR. SLIGHT CHANCE -SHRA.
MONDAY...VFR. WX NIL.
TUESDAY...VFR. WX NIL.
TRS
&&
.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.
&&
$$
