326 PM CDT
MAIN CONCERNS FOR AFTERNOON FORECAST PACKAGE REVOLVE AROUND
OVERNIGHT LOW TEMPERATURES AND WIDESPREAD FROST LATE TONIGHT INTO
SUNDAY MORNING...BUT OTHERWISE WE WILL BE ENTERING A RATHER TRANQUIL
PERIOD OF WEATHER WITH FEW CONCERNS.
A RIDGE OF HIGH PRESSURE EXTENDS FROM LAKE SUPERIOR SOUTHWEST
TOWARDS THE MID MISSISSIPPI VALLEY THIS AFTERNOON WITH LIGHT
NORTHEASTERLY FLOW IN PLACE OVER MUCH OF THE CWA. THE EXCEPTION IS
ALONG THE LAKE SHORE WHERE GUSTY NNE WINDS CONTINUE TO MOVE OFF THE
LAKE...BUT THESE WINDS WILL CONTINUE TO DIMINISH THROUGH THE EVENING
AS THE PRESSURE GRADIENT SLACKENS. NOT TOO MUCH CLOUD COVER TO SPEAK
OF AWAY FROM THE LAKE. SOME FLAT CU WILL DISSIPATE WITH LOSS OF
DAYTIME HEATING...AND LAKE GENERATED CLOUDS WILL BECOME LESS
FAVORABLE OVERNIGHT AS H85 TEMPS WARM WITH APPROACHING THERMAL RIDGE
ALLOWING INVERSION HEIGHTS TO DECREASE BELOW LAKE LCL HEIGHTS
OVERNIGHT PER NAM BUFR SOUNDINGS.
AFTER MIDNIGHT TONIGHT...THE SURFACE RIDGE AXIS WILL SHIFT EASTWARD
TO THE WESTERN PORTIONS OF THE CWA. THIS WILL SET UP FAVORABLE
CONDITIONS FOR RADIATIONAL COOLING WITH WINDS GOING CALM GENERALLY
WEST OF THE I-355/I-290 CORRIDOR AND SKIES MOSTLY CLEAR. OPTED TO
CONTINUE FORECAST FOR TEMPERATURES BELOW ALL GUIDANCE ACROSS OUR
WEST...AND TOWARDS LOWER END OF THE SPECTRUM FOR THE REMAINDER OF
THE CWA. WITH TEMPERATURES EXPECTED TO FALL INTO THE LOW TO MID 30S
FOR MUCH OF THE CWA...HOISTED A FROST ADVISORY FOR THE ENTIRE
CWA...EXCEPT FOR COUNTIES ALONG THE LAKE. AM A LITTLE UNCERTAIN ON
HOW TO HANDLE LAKE COUNTY ILLINOIS AND PORTIONS OF FAR N/NW COOK
COUNTY. WOULD EXPECT TO SEE LAND BREEZE DEVELOP OVERNIGHT WHICH MAY
ALLOW TEMPERATURES TO DROP A LITTLE FURTHER THAN EXPECTED...BUT FOR
NOW ONLY INCLUDED PATCHY FROST FOR THESE AREAS...AND WILL MONITOR
SHORT TERM TRENDS FOR POTENTIAL UPDATES. FOR THE REMAINDER OF COOK
COUNTY...AS WELL AS LAKE AND PORTER COUNTIES IN INDIANA...NORTHERLY
FLOW OFF THE LAKE SHOULD PROP UP TEMPERATURES ALONG THE
SHORE...AS SHOULD URBAN HEAT ISLAND EFFECTS WHICH WILL KEEP
TEMPERATURES IN THE MID 40S NEAR DOWNTOWN CHICAGO.
BEYOND SUNDAY MORNING...UPPER RIDGE IS EXPECTED TO BUILD ACROSS THE
REGION AND PRETTY MUCH STAY IN PLACE THROUGH THE WEEK. H85 TEMPS
RISE FROM THE LOW SINGLE DIGITS TODAY INTO THE MID TEENS BY MONDAY.
SURFACE TEMPS MONDAY WILL REBOUND INTO THE UPPER 60S AND LOW
70S...AND WILL CONTINUE A SLOW WARMING TREND THROUGH THURSDAY WHEN
TEMPERATURES TOP OUT IN THE MID TO UPPER 70S. MODELS ARE IN DECENT
AGREEMENT THROUGH THE END OF THE WEEK...LENDING TO HIGH CONFIDENCE
IN THE PLEASANT FORECAST THROUGH THE WEEK. GLOBAL ENSEMBLE MEMBERS
AS WELL AS OPERATIONAL GFS/ECMWF SOLUTIONS BEGIN TO DIVERGE FRIDAY
INTO THE WEEKEND ON HOW FAR EAST TO PROGRESS THE UPPER RIDGE. THE
GFS HAS ACTUALLY TRENDED TOWARDS THE ECMWF WHICH IS ON THE SLOWER
END OF THE SPECTRUM...WHICH KEEPS FAIR WEATHER IN THE AREA AT
LEAST LATE INTO THE WEEKEND. GFS ENSEMBLE MEAN HOWEVER INDICATES
POTENTIAL FOR A COLD FRONT TO COME THROUGH THE REGION ON SATURDAY.
KEPT FORECAST DRY THOUGH FRIDAY...BUT INTRODUCED SLIGHT CHANCE
POPS FOR SATURDAY.
BMD
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 06Z...
* NO SIGNIFICANT CONCERNS THROUGH THE CURRENT TAF.
BEACHLER
//DISCUSSION...UPDATED 06Z...
LARGE AREA OF HIGH PRESSURE CONTINUES TO BUILD IN FROM THE
NORTHWEST. PRESSURE GRADIENT REMAINS MINIMAL AT THE SFC...HOWEVER
VERTICAL WIND PROFILES INDICATE THAT ARND 2-3KFT AGL WINDS
CONTINUE TO BE GUSTY AROUND 20-30KT FROM THE NORTH/NORTHEAST.
EXPECT THIS TO SLACKEN SLIGHTLY OVERNIGHT...HOWEVER THE SPEED
SHEAR WILL REMAIN WITHIN THE LOWEST 4KFT AGL OF THE ATMOSPHERE.
OTHERWISE VFR CONDS WILL PREVAIL WITH MINIMAL SKY COVER. HI-RES
GUIDANCE CONTINUES TO SUGGEST A SLIGHT BEND NORTHEAST IN THE WIND
FIELD MIDDAY FOR FAR NORTHEAST ILLINOIS AND NORTHWEST INDIANA
AIRFIELDS...HOWEVER VELOCITY REMAINS LESS THAN 12KT. BUT THIS
FEATURE WILL NEED TO BE MONITORED CLOSELY.
BEACHLER
//ORD AND MDW CONFIDENCE...UPDATED 06Z...
* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS.
BEACHLER
//OUTLOOK FOR ORD/MDW FOR 12Z MONDAY-12Z SATURDAY...UPDATED 00Z...
MONDAY THROUGH FRIDAY...VFR.
RATZER
&&
.MARINE...
257 AM CDT
BROAD AREA OF HIGH PRESSURE WILL REMAIN A MAIN INFLUENCE IN THE
WEATHER FOR TODAY...AND CONTINUE THROUGH THE NEXT SEVERAL DAYS.
OBSERVATIONS EARLY THIS MORNING ACROSS THE LAKE HAVE VARIED
BETWEEN 5 TO 10 KT ACROSS THE NORTHERN TIER...TO SLIGHTLY HIGHER
ALONG THE SOUTHERN THIRD OF THE LAKE AT 10 TO 20 KT. WIND
DIRECTIONS HAVE REMAINED FAIRLY CONSISTENT FROM THE NORTH EARLY
THIS MORNING...AND GUIDANCE CONTINUES TO SUGGEST THIS WILL PERSIST
THROUGH THE NEXT 24 HOURS. WITH THE CONTINUED NORTH WIND...AND
OPTIMAL FETCH...WAVES REMAIN ELEVATED ALONG THE SOUTHERN THIRD OF
THE LAKE INTO THE ILLINOIS/NORTHWEST NEARSHORE WATERS. WAVE
HEIGHTS CONTINUE TO STEADILY SUBSIDE AT THE SOUTHERN BUOY...AND AS
OF 3 AM CDT WAVES OF JUST OVER 3 FT WERE BEING REPORTED. THIS
WOULD SUGGEST THAT WAVE IN THE NEARSHORE WATERS WOULD REMAIN IN
THE 3 TO 6 FT RANGE. THUS HAVE MAINTAINED THE SMALL CRAFT HEADLINE
FOR THE ILLINOIS/NORTHWEST INDIANA NEARSHORE WATERS THIS MORNING.
HOWEVER FEEL THAT BY MIDDAY WAVES SHOULD BE JUST UNDER THE
THRESHOLD FOR SMALL CRAFT CONDITIONS AND THE HEADLINE WILL BE
ALLOWED TO EXPIRE.
WINDS WILL REMAIN FROM THE NORTH THROUGH TONIGHT BETWEEN 10 AND 15
KT...THEN SLACKEN FURTHER AS HIGH PRESSURE REMAINS OVERHEAD. BY
THE MIDDLE OF THE WEEK THE SURFACE HIGH PRESSURE SLIDES EAST AND
ALLOWS WINDS TO TURN SOUTHERLY...HOWEVER A DRY AND BENIGN WEATHER
PATTERN WILL PREVAIL THROUGH AT LEAST THE MIDDLE OF THE WEEK AND
POSSIBLY THROUGH THE END OF THE UPCOMING WEEK.
BEACHLER
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...FROST ADVISORY...ILZ003-ILZ004-ILZ005-ILZ008-ILZ010-ILZ011-
ILZ012-ILZ013-ILZ019-ILZ020-ILZ021-ILZ022-ILZ023-ILZ032-
ILZ033-ILZ039 UNTIL 8 AM SUNDAY.
IN...FROST ADVISORY...INZ010-INZ011-INZ019 UNTIL 8 AM SUNDAY.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
UNTIL 10 AM SUNDAY.
&&
$$
