330 PM CST
THE MAIN ISSUES DURING THE FORECAST PERIOD WILL BE WINDS ON SUNDAY
AND PRECIPITATION AMOUNTS MONDAY AND MONDAY NIGHT.
THE MODELS AND ENSEMBLES STILL INDICATE SOME UNCERTAINTY WITH THE
THE EVOLUTION OF THE UPPER LOW OFF THE CALIFORNIA COAST. HOWEVER...THE
MODELS ARE BEGINNING TO AGREE THAT A MAJORITY OF THE ENERGY
ASSOCIATED WITH THIS SYSTEM WILL REMAIN SOUTH OF NORTHERN ILLINOIS.
THE LATEST OBJECTIVE SURFACE ANALYSIS PLACES A WARM FRONT WEST AND
SOUTH OF MY CWA THIS AFTERNOON. THIS FRONT WILL PUSH ACROSS NORTHERN
ILLINOIS THIS EVENING...SETTING UP A DECENT WARMING TREND ON
SATURDAY. SOUTHWESTERLY WINDS DURING THE DAY ON SATURDAY WILL ALLOW
TEMPERATURES TO WARM INTO THE 50S AREA WIDE.
THE MAIN ATTENTION THIS AFTERNOON IS FOCUSED ON SUNDAY AS A
COMPLEX NORTHERN STREAM SHORT WAVE...EMANATING FROM THE
NORTHEASTERN PACIFIC...IS EXPECTED TO PUSH ACROSS THE UPPER
MISSISSIPPI RIVER VALLEY. THIS POTENT SHORT WAVE WILL DRIVE A
STRONG SURFACE LOW ACROSS THE FAR NORTHERN STATES AND SOUTHERN
CANADA. SOUTH TO SOUTHWESTERLY WINDS AHEAD OF THIS LOW LOOK TO
INCREASE ACROSS MUCH OF THE GREAT LAKES REGION AS THIS SUB 985 MB
LOW PUSHES EASTWARD INTO WESTERN ONTARIO. IN FACT IT APPEARS THAT
A WIND ADVISORY MAY BE NEEDED FOR SUNDAY AS STRONG ISALLOBARIC
PRESSURE RISES LOOK TO COUPLE WITH DECENT COLD AIR ADVECTION
BEHIND THE SURFACE COLD FRONT SUNDAY AFTERNOON AND EVENING. MODEL
GUIDANCE ALSO SUGGESTS THAT MEAN BOUNDARY LAYER WINDS COULD EXCEED
40 KT SUNDAY AFTERNOON...AND WITH STRONG SYNOPTIC SCALE DECENT
EXPECTED IN THE WAKE OF THE UPPER LEVEL SHORT WAVE IT WOULD NOT BE
HARD TO GET 40+ KT GUSTS TO THE SURFACE. I WILL HIGHLIGHT THIS
THREAT IN THE HWO FOR NOW AS IT IS WAY TO EARLY FOR A WIND
ADVISORY.
THE OTHER CONCERN WILL BE THE THREAT FOR RAINFALL EARLY NEXT WEEK AS
ADDITIONAL NORTHERN STREAM ENERGY DIGS SOUTHEASTWARD THROUGH THE
LARGER SCALE TROUGH. THIS APPEARS TO BE SETTING UP SOME RAINFALL
FOR PORTIONS OF THE AREA ON MONDAY. HOWEVER...THE HEAVIEST RAINFALL
NOW APPEARS THAT IT WILL FALL FARTHER SOUTH ACROSS CENTRAL AND
SOUTHERN INDIANA MONDAY NIGHT INTO TUESDAY AS THE MAIN SOUTHERN
STREAM ENERGY EJECTS EASTWARD ACROSS THE LOWER MISSISSIPPI VALLEY.
FOLLOWING THIS SYSTEM...THE LARGE SCALE TROUGH WILL SHIFT EASTWARD
AND SET UP A QUASI ZONAL FLOW PATTERN ACROSS THE CONUS FOR THE
MIDDLE PART OF NEXT WEEK. OVERALL THIS WILL LEAD TO A COOL BUT DRY
WEATHER PATTERN FOR A FEW DAYS NEXT WEEK. HOWEVER...IT APPEARS THAT
THE WEATHER PATTERN MAY BECOME ACTIVE AGAIN BY THE LATER PART OF
NEXT WEEK AS POSITIVE HEIGHT ANOMALIES BUILD ACROSS THE NORTHERN
PACIFIC AND DRIVE A STRONG TROUGH FROM ALASKA SOUTHEASTWARD ACROSS
WESTERN NORTH AMERICA. THIS FLOW PATTERN LOOKS TO SET UP POSITIVE
HEIGHT ANOMALIES ACROSS THE SOUTHEASTERN CONUS AND HENCE SOUTHWEST
FLOW ALOFT ACROSS THE CENTRAL PORTION OF THE COUNTY. THIS
ATMOSPHERIC FLOW PATTERN MAY RESULT IN A WARM AND WETTER WEATHER
PATTERN INTO NEXT WEEKEND.
KJB
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 20Z...
* DURATION OF CURRENT 15 TO 20 KT SOUTHERLY WIND GUSTS.
* SOUTHERLY WIND GUSTS ON SATURDAY.
//DISCUSSION...UPDATED 18Z...
LOW PRESSURE LOCATED NORTH OF MN WILL CONTINUE TO MOVE EAST INTO
TONIGHT AND HAVE A WIDE INFLUENCE ACROSS THE GREAT LAKES
REGION...WITH WINDS INCREASING THIS AFTERNOON FROM THE SOUTH
ACROSS THE TAF SITES. SPORADIC GUSTS OVER 20 KTS SEEM PROBABLE FOR
IL TAF SITES BY MID TO LATE AFTERNOON. THESE GUSTS SHOULD DROP OFF
QUICKLY DURING THE EARLY EVENING. A VFR AND GENERALLY QUIET NIGHT
IS EXPECTED AT AIRPORTS...WITH FLOW ALOFT ONLY AROUND 30 TO 35 KTS
IN THE 1K TO 2K FT LAYER. THE PRESSURE GRADIENT WILL REMAIN TIGHT
INTO SATURDAY...WITH SOUTH SOUTHWEST WINDS AGAIN BECOMING GUSTY
DURING THE AFTERNOON. THESE SHOULD BE SLIGHTLY HIGHER THAN
TODAY...WITH A BETTER LIKELIHOOD OF SEEING AFTERNOON GUSTS IN
EXCESS OF 20 KTS.
//ORD AND MDW CONFIDENCE...UPDATED 20Z...
* HIGH CONFIDENCE THAT WIND GUSTS WILL REMAIN BELOW 25 KTS...AND
MEDIUM CONFIDENCE THAT GUSTS WILL SUBSIDE 00Z-01Z.
* MEDIUM CONFIDENCE IN SOUTHWEST GUSTS TO NEAR 25 KTS ON SATURDAY
AFTERNOON.
//OUTLOOK FOR ORD/MDW FOR 00Z SUNDAY-12Z FRIDAY...UPDATED 12Z...
SATURDAY NIGHT...VFR. SLY WINDS INCREASING THROUGH THE NIGHT.
SUNDAY...CHANCE SHRA. CHANCE MVFR EARLY. WINDY. SWLY GUSTS TO
30KT IN THE AFTERNOON.
MONDAY...CHANCE SHRA AND MVFR CIGS.
TUESDAY...VFR. WX NIL.
WEDNESDAY...VFR. WX NIL.
THURSDAY...VFR. SLIGHT CHANCE SHRA LATE.
MTF
&&
.MARINE...
237 AM CST
AN ACTIVE PATTERN IS EXPECTED THROUGH THE WEEKEND INTO NEXT WEEK. A
RIDGE OF HIGH PRESSURE WILL MOVE ACROSS THE LAKE TODAY...ALLOWING A
BRIEF RESPITE FROM THE STRONGER WINDS...BUT THIS QUICK MOVING RIDGE
WILL BE CLOSELY TRAILED BY A RELATIVELY WEAK AREA OF LOW PRESSURE
TONIGHT WHICH WILL ALLOW WINDS TO PICK BACK UP TO AROUND 30 KT
ACROSS THE SOUTHERN PORTIONS OF THE LAKE...WHILE A BRIEF PERIOD OF
GALES ARE EXPECTED ACROSS THE NORTH. WILL UPGRADE THE GALE WATCH
TO A WARNING FOR LATE THIS AFTERNOON AND EVENING. ANOTHER WEAK
RIDGE WILL ALLOW WINDS TO DROP BACK BELOW GALES ON SATURDAY...
MEANWHILE ANOTHER STRONGER AREA OF LOW PRESSURE BEGINS TO DEEPEN
OVER THE CANADIAN PRAIRIES. WHILE THIS LOW IS EXPECTED TO STAY
NORTH OF THE GREAT LAKES...A COLD FRONT SWEEPING ACROSS THE LAKE
WILL USHER IN COLDER AIR AND DEEP MIXING. MODELS SUGGEST 50 TO 60
KT WINDS IN THE LOWEST FEW THOUSAND FEET JUST AHEAD OF THE FRONT.
SOME OF THIS MIXING DOWN TO THE LAKE SURFACE WILL RESULT IN GALE
FORCE WINDS. THESE WINDS WILL INCREASE FURTHER FOR A SHORT PERIOD
BEHIND THE FRONT AS LOW LEVEL LAPSE RATES STEEPEN. THERE IS A GOOD
INDICATION THAT SOME OF THESE WINDS COULD BE HIGHER END GALES
OF 45 KT. WINDS SHOULD DROP BACK BELOW GALE FORCE LATE SUNDAY
NIGHT...BUT BRISK WINDS ARE EXPECTED THROUGH MIDWEEK //ESPECIALLY
FARTHER NORTH// AS AN ACTIVE PATTERN PERSISTS. BMD
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
LMZ868 UNTIL MIDNIGHT SATURDAY.
GALE WATCH...LMZ080-LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-
LMZ567-LMZ669-LMZ671-LMZ673-LMZ675-LMZ777-LMZ779-LMZ868-
LMZ870-LMZ872-LMZ874-LMZ876-LMZ878...6 AM SUNDAY TO
MIDNIGHT MONDAY.
SMALL CRAFT ADVISORY...NEARSHORE WATERS
UNTIL 3 AM SATURDAY.
GALE WATCH...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745...9 AM
SUNDAY TO 9 PM SUNDAY.
&&
$$
