256 PM CDT
ABUNDANT MID/HIGH LVL CLOUDS CONTINUE TO BLANKET THE WESTERN GREAT
LAKES THIS AFTERNOON. PRECIPITATION HAS REMAINED LIGHT AND SCATTERED
ACROSS NORTHERN IL...EVENTUALLY WORKING INTO NORTHWEST IN LATER THIS
AFTERNOON AND EVENING. PRESSURE GRADIENT REMAINS TIGHT AS WELL WITH
OCCASIONAL GUSTS BETWEEN 20 AND 30 MPH...HOWEVER ACROSS EASTERN IOWA
THE GRADIENT WAS BEGINNING TO WEAKEN. THUS EXPECT THE WINDS TO
DECOUPLE LATER THIS EVENING. DRY AIR WAS ALSO BEGINNING TO PUSH
ACROSS THE IA/IL STATELINE AS THE MID-LVL TROUGH AXIS ARRIVES.
FRONTAL PASSAGE CONTINUES TO BE PROGGED FOR THIS EVENING AND WILL
ALLOW SOUTHWEST WINDS TO BECOME WESTERLY THROUGH THE OVERNIGHT
PERIOD. TROUGH AXIS WILL QUICKLY PUSH OVERHEAD WITH DIFFLUENT FLOW
AIDING IN CLOUD EROSION EARLY MONDAY. SFC ANTI-CYCLONIC FLOW SHOULD
REMAIN TO THE SOUTH OF THE CWFA...WHICH WILL ALLOW A LIGHT WIND FROM
THE WEST TO PERSIST THROUGH THE DAY MONDAY AS WELL. TEMPS OVERNIGHT
ARE EXPECTED TO HOVER IN THE 40S...THEN DEPENDING ON WHEN CLOUDS
BEGIN TO BREAK UP EARLY MONDAY...TEMPS FALL INTO THE 30S EXCEPT
AROUND 40 CLOSER TO LAKE MICHIGAN. ENOUGH WIND SHOULD INHIBIT ANY
FROST FORMATION...SO WILL NOT MENTION THIS IN THE FORECAST FOR
TONIGHT.
THEN FOR MONDAY WITH PARTLY CLOUDY SKIES DEVELOPING AND AN 850MB
THERMAL TROUGH OF 0 TO -2 DEG C LINGERING...HIGHS WILL ONLY WARM
INTO THE LOWER 50S. POSSIBLY MID 50S ALONG THE SOUTHERN TIER OF THE
CWFA.
MONDAY NIGHT THROUGH TUESDAY...
TROUGH AXIS STEADILY DEPARTS TO THE EAST AS MID-LVL HEIGHTS CONTINUE
TO RISE. THIS WILL CONTINUE TO PROVIDE DIFFLUENT FLOW ALOFT AND KEEP
DRY AIR IN PLACE THROUGH TUESDAY. IT APPEARS POSSIBLY THAT OVERNIGHT
LOWS MON NGT INTO EARLY TUE COULD YET AGAIN APPROACH THE FREEZING
POINT FOR MANY LOCATIONS AWAY FROM LAKE MICHIGAN. TEMPS ALOFT ARE
MARGINALLY WARMER THAN THE PREVIOUS NIGHT...SO IT WILL BE POSSIBLE A
DECENT LOW LEVEL INVERSION WILL SETUP. THIS MAY ALLOW PATCHY GROUND
FOG TO DEVELOP WITH LIGHT WINDS. FOR TUESDAY A STEADY WARMING TREND
WILL BE IN FULL SWING...AS SFC TEMPS MAY CLIMB INTO THE 60S POSSIBLY
MID 60S FOR LOCATIONS SOUTH OF A LA SALLE COUNTY TO KANKAKEE COUNTY
LINE.
WEDNESDAY...
ANTI-CYCLONIC FLOW REMAINS IN CONTROL FOR MUCH OF WED. LATEST
GUIDANCE HAS BACKED OFF ON ARRIVAL OF MOISTURE. THUS IT APPEARS FOR
MUCH OF WED THE DAY WILL REMAIN DRY. SOUTHWEST WINDS AHEAD OF THIS
NEXT FRONTAL BOUNDARY AND TEMPS COULD EASILY STAY AROUND 60 TO THE
LOWER 60S FOR MUCH OF THE AREA. GUIDANCE HAS CONTINUED TO BACK OFF
ON MOISTURE ARRIVAL UNTIL WED EVENING...WHEN SHORTWAVE FINALLY
BEGINS TO ARRIVE FROM THE NORTHWEST. HAVE PUSHED PRECIP ARRIVAL BACK
UNTIL CLOSER TO 00Z THUR.
THURSDAY THROUGH SATURDAY...
MARGINAL SPREAD AMONGST ENSEMBLES FOR THE START OF THE EXTENDED
PERIOD...WITH RESPECT TO THE HIGH AMPLITUDE RIDGE PROGGED ACROSS THE
INTERIOR WEST. ACROSS THE MID-SECTION OF THE COUNTRY A FRONTAL
BOUNDARY IS POISED TO SLUGGISHLY PUSH EAST...AS A RESULT GUIDANCE
HAS SHOWN CONSIDERABLE NOISE OR LOW CONFIDENCE ON HOW TO RESOLVE
THIS FEATURE. ENSEMBLES CONTINUE TO FAVOR AMONGST MANY MEMBERS A
GRADUAL PROGRESSION OF THE BOUNDARY TO THE EAST AS THE RIDGE BUILDS
IN FRI. IT APPEARS OPERATIONAL SOLUTIONS HAVE BEEN TOO AGGRESSIVE
WITH PUSHING THE SFC RIDGE EAST LATE IN THE WEEK...AND CONTINUE TO
HINT AT A POTENT SHORT WAVE DEVELOPING ACROSS THE SOUTHERN PLAINS
FRI/SAT.
THIS LATE WEEK INTO NEXT WEEKEND SYSTEM REMAINS A FOCAL POINT
AMONGST MANY OPERATIONAL SOLUTIONS...HOWEVER ENSEMBLES HAVE BEEN
SUGGESTING MUCH OF THE OHIO VALLEY/EXTENDING WEST INTO THE MISSOURI
VALLEY WOULD REMAIN UNDER THE INFLUENCE OF ANTI-CYCLONIC FLOW IN THE
MID-LVLS. THIS WOULD FAVOR A DEFLECTION OF THIS SYSTEM TO THE
NORTHWEST ACROSS THE UPPER MIDWEST. SEVERAL DAYS STAND BETWEEN NOW
AND NEXT WEEKEND...HOWEVER THIS SYSTEM WILL CONTINUE TO BE
MONITORED. BEHIND THIS SYSTEM IT APPEARS A STRONG THERMAL TROUGH IS
DEVELOPING AND EXPECTED TO ARRIVE ACROSS THE GREAT LAKES REGION
SOMETIME OVER THE UPCOMING WEEKEND. THIS MAY LIMIT AFTN MAX TEMPS
FOR THE SECOND HALF OF THE WEEKEND IN THE 40S. LOW CONFIDENCE AT
THIS POINT ON TIMING AND INTENSITY. TEMPERATURES IN THE EXTENDED
APPEAR TO HOVER IN THE 50S...POSSIBLY APPROACHING 60 DEGREES SAT.
BEACHLER
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 21Z...
* SOUTHWEST WINDS GUSTING TO AROUND 25 KT NEXT 1 TO 3 HRS.
* INTERMITTENT RAIN UNTIL 23-00Z...WITH HEAVIEST RAIN OCCURRING NOW.
* CIGS AROUND 3500 FT WITH POTENTIAL FOR BRIEF PERIODS OF CIGS
2800-3200 FT.
MDB
//DISCUSSION...UPDATED 21Z...
BAND OF RAIN CONTINUES TO LIFT NORTHEASTWARD AND SHOULD BE CLEAR
OF THE CHICAGO AREA TERMINALS BY AROUND 00Z AND OVER THE NEXT 1-2
HRS AT RFD. WIND GUSTS STARTING TO BECOME MORE SPORADIC WITH
PRESSURE GRADIENT STARTING TO LOOSEN UP BUT GUSTS TO AROUND 25 KT
STILL POSSIBLE WITH THE SHOWERS. CIGS HAVE GENERALLY FALLEN TO
LOWER END VFR BUT PATCHY MVFR 2500-3000 FT MAY OCCUR.
FROM 18Z UPDATE...
MAIN CONCERN FOR THE REMAINDER OF THE AFTERNOON AND INTO THE EARLY
EVENING WILL FOCUS ON WINDS. AS THE SFC LOW CONTINUES TO MOVE EWD
INTO SERN MINNESOTA...SURFACE PRESSURE FALLS ON THE ORDER OF
3MB/3HRS ARE NOW CENTERED OVER NRN IL/SRN WI. SOUTH WINDS ACROSS
THE AREA ARE GUSTING TO 25KT...AND WITH SOME FILTERED SUNSHINE
OVER NERN IL/NWRN IN/SRN LAKE MICHIGAN...THERE WILL STILL BE THE
POTENTIAL FOR GUSTS APPROACHING 30KT THIS AFTERNOON. AS THE SFC
LOW WEAKENS AND LIFTS TO THE NORTHEAST TONIGHT...WINDS WILL
DECREASE AND VEER SOUTHWESTERLY TO WESTERLY BY TOMORROW.
THE ONE SIGNIFICANT CHANGE TO THE GOING FORECAST IS TO BACK OFF ON
PCPN POTENTIAL AT THE TERMINALS. THE LATEST RADAR IMAGERY SHOWS A
SPLIT IN THE PCPN PATTERN OVER NRN IL...WITH AREAS OF RAIN MORE
CONCENTRATED IN WISCONSIN AND CENTRAL IL...SOUTH OF THE TERMINALS.
THE LOW LEVELS HAVE BEEN VERY SLOW TO MOISTEN AND SFC DEWPOINTS
ARE STILL IN THE LOW 30S. SO...HAVE BACKED OFF PCPN MENTION TO
VCSH. THERE IS STILL A CHANCE OF SOME SPRINKLES OR LIGHT SHOWERS
ACROSS THE AREA...BUT NOW FEEL THAT THE CHANCES FOR WETTING RAIN
AT THE TERMINALS IS SMALL.
KREIN
//ORD AND MDW CONFIDENCE...UPDATED 21Z...
* HIGH CONFIDENCE IN WINDS GUSTING TO AROUND 25 KT NEXT 1 TO 3
HOURS BUT THESE MAY BECOME LESS FREQUENT WITH TIME.
* HIGH CONFIDENCE IN INTERMITTENT RAIN CONTINUING UNTIL 23 OR 00Z
WITH HEAVIEST RAIN OCCURRING UNTIL ABOUT 22Z.
* MEDIUM-HIGH CONFIDENCE IN LOWEST PREVAILING CIGS AROUND 3500 FT
AND MEDIUM CONFIDENCE THAT ANY LOWER CIGS 2800-3200 WOULD BE
SHORT LIVED.
MDB
//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...
MONDAY NIGHT...VFR.
TUESDAY...VFR.
WEDNESDAY...CHC SHRA...MAINLY VFR. CHANCE MVFR CIGS OVERNIGHT.
THURSDAY...CHC SHRA...MVFR CIGS POSSIBLE.
FRIDAY...VFR.
SATURDAY...CHC SHRA.
KREIN
&&
.MARINE...
256 AM CDT
SOUTH-SOUTHEAST GALES ARE EXPECTED THROUGH EARLY EVENING OVER THE
CENTRAL AND SOUTHERN PORTIONS OF LAKE MICHIGAN.
LOW PRESSURE OVER THE UPPER MISSISSIPPI VALLEY COMBINED WITH HIGH
PRESSURE OVER THE MID ATLANTIC REGION HAS RESULTED IN A STRONG
SURFACE PRESSURE GRADIENT ACROSS LAKE MICHIGAN TODAY WINDS
QUICKLY INCREASED TO GALE FORCE EARLIER TODAY AND GALES TO 35 KT
RANGE WILL LIKELY PERSIST INTO THE EARLY EVENING HOURS. THE LOW
WILL THEN WEAKEN...ALLOWING WINDS TO GRADUALLY DIMINISH OVERNIGHT.
A WEAK COLD FRONT ASSOCIATED WITH THE WEAKENING LOW WILL SWEEP
ACROSS LAKE MICHIGAN OVERNIGHT SETTING UP A PERIOD OF GENERALLY
SOUTHWESTERLY WINDS INTO WEDNESDAY MORNING. ANOTHER...STRONGER
COLD FRONT IS EXPECTED TO PUSH ACROSS THE LAKE WEDNESDAY AFTERNOON
AS STRONG HIGH PRESSURE BUILDS OVER THE SOUTHERN PLAINS AND THE
UPPER MISSISSIPPI VALLEY.
KREIN
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ080-LMZ567-LMZ669-LMZ671-LMZ673-LMZ675-LMZ777-
LMZ779-LMZ868-LMZ870-LMZ872-LMZ874-LMZ876-LMZ878 UNTIL 9 PM
SUNDAY.
SMALL CRAFT ADVISORY...NEARSHORE WATERS
UNTIL 10 PM SUNDAY.
&&
$$
