358 AM CDT
MAIN FORECAST CONCERNS ARE WITH PRECIP CHANCES TODAY AS WELL AS
INTO THE END OF THE WEEKEND...WITH A POSSIBLE BRIEF WARM UP EARLY
NEXT WEEK.
LATEST SATELLITE IMAGERY SHOWING A LARGE AREA OF HIGH LEVEL CIRRUS
MOVING ACROSS PORTIONS OF NORTHERN ILLINOIS AND NORTHWEST INDIANA
EARLY THIS MORNING...WITH SOME MID/LOW LEVEL CLOUD COVER MOVING
EAST ACROSS THE LAKE. ALTHOUGH...THIS HIGH LEVEL CIRRUS IS RATHER
THIN AND STILL RESULTING IN MOSTLY CLEAR CONDITIONS. WITH THESE
CLEAR SKIES AND CALM CONDITIONS...TEMPERATURES HAVE BEEN ABLE TO
FALL INTO TO THE LOW AND MID 30S THIS MORNING WITH WARMER TEMPS
NEAR THE LAKE. WITH THESE FALLING TEMPS...HAD INCLUDED THE
REMAINDER OF THE CWA IN THE FROST ADVISORY THIS MORNING WITH THE
EXCEPTION OF COOK COUNTY. THERE ALSO REMAINS SOME ISOLATED AREAS
OF FOG THIS MORNING...WITH VISIBILITIES HOLDING AROUND 2-4SM AND
EVEN SOME BRIEF PERIODS OF VIS AROUND 1-3SM. THIS IS MOST LIKELY
DUE IN PART TO SOME AREAS WHICH RECEIVED SOME SHOWERS/MOISTURE
YESTERDAY EVENING. DONT EXPECT TOO MUCH EXPANSION OF THIS
FOG...MAINLY REMAINING ISOLATED. ALTHOUGH...WITHIN THESE
AREAS...LOWER VISIBILITY COULD BE OBSERVED.
LATEST SATELLITE IMAGERY SHOWING THE NEXT WAVE TO BRING OUR AREA
SOME SHOWERS UP ACROSS THE NORTHERN PLAINS...WITH ASSOCIATED CLOUD
COVER AND LIGHT SHOWERS ALSO PRESENT. THIS MID LEVEL WAVE AND
SURFACE TROUGH AXIS WILL DIG SOUTH THROUGH THE MIDWEST TODAY AND
REACH THE CWA LATER THIS AFTERNOON. NOT ONLY WILL FORCING BE ON
THE INCREASE...BUT MUCH COLDER AIR ALOFT WILL SHIFT SOUTHWARD.
THIS WILL RESULT IN STEEP LOW AND MID LEVEL LAPSE RATES. THESE TWO
FEATURES COINCIDING WITH ONE ANOTHER WILL ENABLE SHOWERS TO
DEVELOP WITH THE WESTERN PORTION OF THE CWA OBSERVING THE BETTER
CHANCES THIS AFTERNOON. THEN THIS TROUGH AXIS WILL SHIFT EAST WITH
FORCING EXPANDING EAST ACROSS THE REMAINDER OF THE CWA WITH THE
OVERALL BEST CHANCES FOR THE CWA TO OBSERVE SHOWERS COMING IN THE
LATE AFTERNOON AND EARLY EVENING. THERMAL PROFILES OVER THE LAKE
DURING THIS TIME FRAME WILL NOT ONLY BE FAVORABLE FOR SHOWERS BUT
EVEN THE POSSIBILITY FOR THUNDER AS VERY LOW AND MID LEVEL LAPSE
RATES WILL BE IN PLACE AS THE COLDEST AIR ALOFT MOVES OVERHEAD.
THEN WITH THIS UPPER LEVEL TROUGH SHIFTING EAST...THIS
PRECIP/CLOUD COVER WILL ALSO SLOWLY SHIFT EAST. AS CLEAR SKIES
SLOWLY WORK BACK IN FROM THE WEST...TEMPS COULD FALL ONCE AGAIN
WITH SIMILAR CONDITIONS/TEMPS POSSIBLE TONIGHT. A BRIEF PERIOD OF
RIDGING ON SATURDAY WILL RESULT IN FAIR CONDITIONS BUT THIS WILL
BE ONGOING AS THE NEXT SYSTEM APPROACHES FROM THE WEST. ANOTHER
TROUGH WILL DIG SOUTHEAST OUT OF THE NORTHERN PLAINS SATURDAY
NIGHT INTO SUNDAY WITH SURFACE REFLECTION PUSHING THROUGH DURING
THE DAY SUNDAY. SHOWERS WILL DEVELOP OUT AHEAD OF THIS
SYSTEM...WITH MODELS IN FAIR AGREEMENT OF THE EVOLUTION OF THIS
SYSTEM. WITH THE BEST CHANCES ACROSS THE NORTHERN CWA...HAVE
RAISED POPS ON SUNDAY. THEN CLEARING ON MONDAY WITH A WARMING
TREND EXPECTED THAT DAY INTO TUESDAY WITH MAX TEMPS POSSIBLY
REACHING THE LOWER 60S.
RODRIGUEZ
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 16Z...
* WINDS STEADILY INCREASE FROM THE SW. OCCASIONAL GUSTS TO 16KT
BTWN 17-23Z.
* PSBL SHRA DEVELOPING AFT 00Z.
BEACHLER
//DISCUSSION...UPDATED 12Z...
IR IMAGERY SHOWING MID/HIGH BASED CLOUDS FLOATING EAST ACROSS
NORTHERN IL/NORTHWEST IN. MIXED LAYER IS EXPECTED TO RISE TO
AROUND 9000FT AGL...WHICH SHOULD FILTER TO THE SFC WINDS AROUND
20KT. EXPECT THIS WILL RESULT IN GUSTS BETWEEN 15 TO 17KT...SO
HAVE INCLUDED THIS IN THE LATEST TAF PACKAGE. THE OTHER CHANGE WAS
TO PUSH BACK THE PROB30 GROUP MENTION OF PRECIP UNTIL AFT 02Z. IT
APPEARS THE UPPER LEVEL LOW PRESSURE SYSTEM WILL NOT ARRIVE UNTIL
CLOSER TO 00Z...WHICH WILL DELAY THE ARRIVAL OF PRECIPITATION.
PREV DISCUSSION...12Z...
WEAK SURFACE HIGH PRESSURE IS DRIFTING OFF TO THE SOUTH OF THE
TERMINALS EARLY THIS MORNING...AND WILL ALLOW CALM/VARIABLE WINDS
TO BECOME LIGHT SOUTHWEST THIS MORNING.
LOW PRESSURE TROUGH OVER THE UPPER MIDWEST WILL SLIDE SOUTHEAST
TOWARD THE FORECAST AREA LATER TODAY...AND WILL PRESENT A THREAT
OF SHOWERS TOWARD EVENING AS COLD AIR ALOFT AGAIN RESULTS IN
FAIRLY DEEP LAYER OF STEEP LAPSE RATES/INSTABILITY. MODEL GUIDANCE
IN OVERALL AGREEMENT THAT SHOWERS WILL OCCUR NEARBY...THOUGH
RELATIVELY DRY LOW LEVEL AIR DOES REDUCE CONFIDENCE WITH RESPECT
TO COVERAGE. THIS ALSO SUPPORTS PREVAILING VFR CONDITIONS THROUGH
THE PERIOD...OUTSIDE OF ANY PATCHY FOG EARLY THIS MORNING.
PASSAGE OF THE SURFACE TROUGH LATE THIS EVENING WILL SHIFT WINDS
FROM SOUTHWEST TO LIGHT WEST OVERNIGHT.
RATZER
//ORD AND MDW CONFIDENCE...UPDATED 16Z...
* HIGH CONFIDENCE IN ALL ELEMENTS THROUGH 00Z.
* LOW CONFIDENCE ON PRECIP TIMING AND COVERAGE.
BEACHLER
//OUTLOOK FOR ORD/MDW FOR 00Z SUNDAY-12Z FRIDAY...UPDATED 12Z...
SATURDAY NIGHT...VFR.
SUNDAY...CHANCE OF SHOWERS. LOCAL MVFR CIGS POSSIBLE.
MONDAY...MVFR POSSIBLE EARLY...THEN VFR.
TUESDAY...VFR.
WEDNESDAY...CHC SHRA. MVFR POSSIBLE.
THURSDAY...VFR.
RATZER
&&
.MARINE...
155 AM CDT
SEVERAL UPPER LEVEL DISTURBANCES/CLIPPER SYSTEMS SHOULD AFFECT THE
WEATHER OVER LAKE MICHIGAN FOR THE NEXT FEW DAYS. EACH DISTURBANCE
LOOKS TO PROVIDE AN INCREASE IN THE WINDS AND GOOD CHANCES FOR LAKE
EFFECT/LAKE ENHANCED SHOWERS AND EVEN SOME THUNDERSTORMS.
THE FIRST CLIPPER SYSTEM WILL RACE SOUTHEASTWARD ACROSS THE LAKE
LATER TODAY AND TONIGHT. THE ASSOCIATED SURFACE TROUGH OF LOW
PRESSURE SHOULD INDUCE AN INCREASE IN THE SOUTH TO SOUTHWESTERLY
WINDS LATER THIS AFTERNOON AND DURING THE EVENING. THIS SHOULD
PROVIDE A WINDOW OF 15 TO 25 KT WINDS INTO THIS EVENING BEFORE THE
WINDS ABATE. THE OTHER CONCERN WITH THIS SYSTEM WILL BE THE THREAT OF
SOME THUNDERSTORMS AND WATERSPOUTS TONIGHT. VERY COLD TEMPERATURES
ALOFT ASSOCIATED WITH THE UPPER LEVEL DISTURBANCE SHOULD PROVIDE A
FAVORABLE THERMODYNAMIC SETUP FOR THUNDERSTORMS AND WATERSPOUTS. THE
WATERSPOUT THREAT WILL LIKELY BE THE HIGHEST DURING THE LATER
EVENING AND OVERNIGHT HOURS AS THE SURFACE TROUGH PROVIDES A GOOD
SURFACE CONVERGENCE ZONE. THIS THREAT WILL DIMINISH ON SATURDAY
MORNING.
THERE WILL BE A BRIEF QUIET PERIOD DURING THE DAY ON SATURDAY AS A
SURFACE RIDGE OF HIGH PRESSURE BUILDS IN ACROSS THE LAKE.
HOWEVER...ANOTHER CLIPPER SYSTEM LOOKS TO AFFECT LAKE MICHIGAN ON
SUNDAY AND SUNDAY NIGHT. THIS SYSTEM APPEARS TO BE THE STRONGEST OF
THE TWO...AND THEREFORE THE SOUTHERLY WINDS THAT IT INDUCES ON
SUNDAY COULD APPROACH LOW END GALE FORCE. WILL STAY CONSERVATIVE AND
CAP THE WINDS AT 32 KT AT THIS TIME. AT THE LEAST...THIS LOOKS TO
PRODUCE A GOOD CHANCE OF SMALL CRAFT CONDITIONS FOR THE NEAR SHORE
WATERS ON SUNDAY.
NEXT WEEK IT APPEARS THAT THE WEATHER PATTERN WILL REMAIN ACTIVE
ACROSS THE CENTRAL CONUS. HOWEVER...AT THIS TIME THE STRENGTH OF THE
STORM SYSTEMS REMAIN IN QUESTION.
KJB
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&
$$
