1024 PM CDT
ONLY VERY MINOR SHORT TERM TWEAKS MADE TO GOING SET OF GRIDDED
FORECASTS SO LITTLE OR NO CHANGE IN DERIVED TEXT PRODUCTS.
LATEST IR SATELLITE SHOT ALONG WITH WSR-88D...TERMINAL DOPPLER
AND PROFILER MID LEVEL WINDS SHOW THE TROUGH AXIS ACROSS FAR SE
WI...NE IL...CENTRAL IL AND E CENTRAL MO. WHILE RADARS CONTINUE
TO PAINT ECHOES ALONG AND A BIT AHEAD OF THIS MID LEVEL TROUGH
VERY LITTLE RAIN IS REACHING THE SURFACE AS IT DRIES UP FALLING
FROM MID LEVEL CLOUDS INTO A VERY DRY LOW LEVEL AIR MASS.
AS THE SHORT WAVE TROUGH CONTINUES OFF TO THE E DURING THE
OVERNIGHT HOURS THE CLEARING THAT HAS ALREADY REACHED A
RFD-SQI-MQB LINE WILL CONTINUE TO SPREAD ACROSS THE ENTIRE AREA
ALLOWING STRONG RADIATIONAL COOLING CONDITIONS FOR THE EARLY
MORNING AND PREDAWN HOURS. THUS...FREEZE WARNING CONTINUES.
TRS
//PREV DISCUSSION...
320 PM CDT
MAIN CONCERN FOR THE NEAR TERM...THE REMAINDER OF THE AFTERNOON AND
TONIGHT...WILL FOCUS ON PCPN POTENTIAL THIS AFTERNOON/EARLY EVENING
AND TEMPERATURES OVERNIGHT. LATEST SATELLITE IMAGERY SHOWS SCT-BKN
CU DEVELOPMENT ASSOCIATED WITH DIURNAL WARMING AND AN UPPER TROUGH
CROSSING THE MISSISSIPPI RIVER INTO NWRN IL. CU DEVELOPMENT IS NOT
QUITE AS VIGOROUS AS YESTERDAY...SO WILL ONLY CARRY SLIGHT CHANCE
POPS THROUGH THE REMAINDER OF THE DAYLIGHT HOURS. LATEST RADAR
IMAGERY SHOWS SOME SPOTTY ECHOES OVER NWRN/NCNTRL IL...THOUGH THERE
ARE NO REPORTS OF PCPN IN THE METARS. GIVE THE VERY DRY AIR AT THE
SFC...WITH DEWPOINTS IN THE 20S...EXPECT THAT MUCH OR ALL OF THE
ECHO IS VIRGA. HOWEVER...AS THE MAIN COLD POOL ASSOCIATED WITH THE
TROUGH MOVES ACROSS THE CWA OVER THE NEXT 4-5 HRS...THERE WILL BE A
GREATER POTENTIAL FOR SOME OF THE PCPN TO ACTUALLY REACH THE
GROUND. ALSO...WITH VERY STEEP LAPSE RATES AND WITH VERY LOW
FREEZING LEVELS...UNDER 5KFT...SOME MORE GRAUPEL WITH THE HEAVIEST
SHOWERS WILL BE A POSSIBILITY. FOR THE REMAINDER OF THE NIGHT...THE
DIURNAL CLOUD COVER WILL DISSIPATE AND SKIES WILL BECOME MOSTLY
CLEAR. WITH STRONG RADIATIONAL COOLING...LIGHT WINDS AND LOW
DEWPOINTS...EXPECT TEMPERATURES TO DROP INTO THE UPPER 20S TO AROUND
30F FOR MUCH OF THE CWA AWAY FROM LAKE MICHIGAN AND HEAVILY
URBANIZED AREAS. SO...WILL ISSUE A FREEZE WARNING FOR ALL COUNTIES
EXCEPT COOK COUNTY. HAVE INCLUDED THE OTHER LAKEFRONT COUNTIES IN
THE WARNING SINCE A MAJORITY OF THE COUNTY AWAY FROM THE LAKE SHOULD
DROP BELOW FREEZING.
FOR THE REMAINDER OF THE SHORT TERM FORECAST PERIOD...SATURDAY
THROUGH MONDAY...TEMPERATURES WILL BE ON THE INCREASE FOR BOTH MINS
AND MAXS. FOR THE WEEKEND...HIGH TEMPS WILL BE IN THE LOWER TO
MIDDLE 50S AND BY MONDAY...HIGHS SHOULD BE IN THE MIDDLE TO UPPER
50S. OVERNIGHT LOWS SHOULD...SIMILARLY...MODERATE AND DO NOT
ANTICIPATE MORE THAN JUST SOME PATCHY FROST FOR THE EARLY MORNING
HOURS. SATURDAY SHOULD BE MOSTLY SUNNY AND DRY AS UPPER LEVEL AND
SFC RIDGING BUILDS ACROSS THE AREA. THE NEXT CHANCE FOR SOME PCPN
WILL COME ON SUNDAY AS THE NEXT UPSTREAM SYSTEM DROPS OUT OF THE NRN
PLAINS AND ACROSS THE MIDWEST. THE MODELS ARE TRENDING A LITTLE
STRONGER WITH THIS SYSTEM WITH A VERTICALLY STACKED CLOSED LOW
DEVELOPING AS THE SYSTEM MOVES OVER ERN IOWA SUNDAY AFTERNOON. THE
PROGRESSION OF THE SYSTEM WILL THEN SLOW DOWN OVERNIGHT MONDAY AS
THE DEEPENING SFC LOW OFF THE NEW ENGLAND COAST EFFECTIVELY BLOCKS
PROGRESSION OF SYSTEMS TO THE WEST. SO...ANTICIPATE THAT PCPN MAY
LINGER OVER THE ERN PORTIONS OF THE CWA INTO MONDAY MORNING.
FOR THE LONGER TERM...FOR TUESDAY THROUGH FRIDAY...FORECAST
UNCERTAINTY INCREASES WITH TIME THROUGH THE PERIOD. THE GUIDANCE IS
RELATIVELY CONSISTENT IN KEEPING THE AREA DRY INTO TUESDAY NIGHT...
BUT CONFIDENCE IN THE FORECAST DECREASES BY WEDNESDAY AS THE MODELS
BEGIN TO DIFFER SIGNIFICANTLY...ESPECIALLY IN HOW THEY HANDLE THE
SOUTHERN STREAM ENERGY LIFTING OUT OF THE SOUTHERN ROCKIES AND INTO
THE SRN PLAINS. THE ECMWF WANTS TO CLOSE OFF A SRN STREAM SHORTWAVE
INTO A CLOSED LOW...WHILE MAINTAINING STREAM SEPARATION WITH A NRN
STREAM SHORTWAVE. THE GFS IS INDICATING A MORE PHASED
SOLUTION...BUT DOES SOMEWHAT EMPHASIZE THE NRN STREAM SHORTWAVE.
SO...WHILE EITHER SOLUTION WOULD POINT TO PCPN FOR THE AREA AT SOME
POINT FOR WEDNESDAY THROUGH FRIDAY...HAVE GONE WITH MORE GENERALIZED
CHANCE POPS RATHER THAN JUMP ON ONE SOLUTION OR THE OTHER AND WAIT A
FEW MORE CYCLES BEFORE COMMITTING TO HIGHER POPS.
KREIN
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 06Z...
* ENDING OF SHOWERS AND WIND SHIFT FROM SOUTH TO WEST-NORTHWEST
DURING PRE-DAWN HOURS.
RATZER
//DISCUSSION...UPDATED 06Z...
WEAK SURFACE TROUGH/COOL FRONT WAS MOVING SLOWLY ACROSS NORTHERN
ILLINOIS EARLY THIS MORNING...AND SHOULD MOVE THROUGH KRFD SHORTLY
AND ACROSS CHICAGO AREA TERMINALS 09-10Z. TRAILING EDGE OF
SCATTERED SHOWERS AHEAD OF THIS FRONT WERE ALREADY MOVING THROUGH
KORD/KMDW AND SHOULD BE PAST KGYY AFTER 07Z OR SO. SOUTH-SOUTHWEST
WINDS LESS THAN 10 KTS AHEAD OF THE FRONT WILL SHIFT TO THE WEST
WITH FROPA. GOES IR SATELLITE IMAGERY DEPICTS FAIRLY QUICK
TRANSITION TO CLEAR SKIES BEHIND THE FRONT. WHILE SOME PATCHY
GROUND FOG NOT COMPLETELY OUT OF THE QUESTION AS SKIES CLEAR OVER
MOIST GROUND IN LIGHT GRADIENT...AIR IS FAIRLY DRY JUST ABOVE THE
SURFACE AND DRIER AIR WILL FILTER IN BEHIND THE FRONT OVERNIGHT.
VFR CONDITIONS ARE EXPECTED TO CONTINUE THROUGH THE REMAINDER OF
THE TAF PERIOD.
SURFACE HIGH PRESSURE RIDGE SPREADS ACROSS TERMINALS LATE
SATURDAY AFTERNOON AND EVENING...WITH WEST-NORTHWEST WINDS AROUND
10 KT DURING THE DAY DECREASING AND BACKING TO THE SOUTH AGAIN IN
THE EVENING. MID/HIGH CLOUDS WILL INCREASE LATE SATURDAY NIGHT AS
NEXT SYSTEM APPROACHES.
RATZER
//ORD AND MDW CONFIDENCE...UPDATED 06Z...
* HIGH CONFIDENCE ALL ELEMENTS.
RATZER
//OUTLOOK FOR ORD/MDW FOR 12Z SUNDAY-12Z FRIDAY...UPDATED 00Z...
SUNDAY...CHANCE OF SHOWERS WITH MVFR CIGS POSSIBLE.
MONDAY...MVFR POSSIBLE EARLY...THEN VFR.
TUESDAY...VFR.
WEDNESDAY...CHANCE SHRA WITH MVFR POSSIBLE.
THURSDAY...MVFR POSSIBLE EARLY.
MDB
&&
.MARINE...
323 AM CDT
THE MAIN MARINE FORECAST CONCERN THIS MORNING IS WITH SOUTH GALES
DEVELOPING ON THE SOUTH HALF OF LAKE MICHIGAN SUNDAY MORNING AS
LOW PRESSURE DROPS SOUTHEAST ACROSS THE UPPER MIDWEST. MODELS ARE
IN GOOD AGREEMENT IN SOUTH WINDS STRENGTHENING RAPIDLY AS THE
GRADIENT TIGHTENS AHEAD OF THE LOW...WITH FORECAST SOUNDINGS
DEPICTING WINDS INCREASING ABOVE 30 KTS WITHIN THE MIXED LAYER BY
MID MORNING. THE LOW WILL THEN BEGIN TO FILL BY EVENING AS IT
DRIFTS EAST...WITH GALES DROPPING OFF FAIRLY QUICKLY LATE IN THE
DAY. BASED ON THIS HAVE HOISTED A GALE WARNING FOR THE OPEN WATERS
OF SOUTHERN LAKE MICHIGAN FOR SUNDAY.
FOR THE ILLINOIS AND INDIANA NEARSHORE WATERS...WINDS WILL LIKELY
GUST TO 30 KTS FOR A TIME SUNDAY. WILL HAVE A SMALL CRAFT ADVISORY
FROM EARLY SUNDAY MORNING THROUGH EARLY SUNDAY EVENING.
THE LOW WILL CONTINUE TO FILL AS IT DRIFTS EAST ACROSS THE LAKE
LATER SUNDAY NIGHT AND MONDAY. DEEPER LOW PRESSURE WILL MOVE
ACROSS CENTRAL CANADA EARLY NEXT WEEK...SETTING UP A PERIOD OF
SOUTHWEST FLOW ACROSS THE WESTERN LAKES REGION.
RATZER
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...FREEZE WARNING...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-ILZ010-
ILZ011-ILZ012-ILZ013-ILZ019-ILZ020-ILZ021-ILZ022-ILZ023-
ILZ032-ILZ033-ILZ039 UNTIL 9 AM SATURDAY.
IN...FREEZE WARNING...INZ001-INZ002-INZ010-INZ011-INZ019 UNTIL 9 AM
SATURDAY.
LM...GALE WARNING...LMZ080-LMZ567-LMZ669-LMZ671-LMZ673-LMZ675-LMZ777-
LMZ779-LMZ868-LMZ870-LMZ872-LMZ874-LMZ876-LMZ878...7 AM
SUNDAY TO 7 PM SUNDAY.
&&
$$
