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 00Z...
* SOUTHWEST WINDS INCREASING WITH GUSTS NEAR 25 KTS SATURDAY.
RATZER
//DISCUSSION...UPDATED 00Z...
WARM FRONTAL TROUGH ALONG MISSISSIPPI RIVER WILL MOVE EAST ACROSS
THE TERMINALS WHILE BECOMING LESS WELL-DEFINED OVERNIGHT. EARLIER
SURFACE PRESSURE FALLS ACROSS CENTRAL/NORTHEAST ILLINOIS HAVE
WEAKENED...WHICH ALONG WITH NIGHTFALL AND RESULTING WEAKENING OF
MIXING IN LOW LEVELS HAS ALLOWED EARLIER GUSTS TO BECOME MUCH MORE
SPORADIC. SOUTH TO SOUTH-SOUTHEAST WINDS AROUND 10 KTS SHOULD
PREVAIL THIS EVENING...EVENTUALLY DECREASING AND BECOMING MORE
SOUTHWEST OVERNIGHT AS THE GRADIENT RELAXES. VFR CONDITIONS TO
CONTINUE WITH LITTLE IN THE WAY OF CLOUD COVER EXPECTED THROUGH
THE NIGHT.
SOUTH-SOUTHWEST WINDS WILL INCREASE DURING THE DAY SATURDAY AS
DEEP LOW PRESSURE DEVELOPS OVER THE NORTHERN PLAINS. WINDS WILL
LIKELY GUST TO 25 KTS OR SO BY EARLY AFTERNOON...THOUGH MIXING
MAY BE LIMITED SOMEWHAT BY THICKENING HIGH LEVEL CLOUD DECK.
PRESSURE GRADIENT REMAINS TIGHT SATURDAY NIGHT WITH GUIDANCE
INDICATING SUSTATINED WINDS OF 15 KTS OR MORE OVERNIGHT. QUESTION
WILL BE HOW QUICKLY GUSTS DIMINISH TOWARD SUNSET BENEATH SHALLOW
INVERSION LAYER. FORECAST SOUNDINGS INDICATE WINDS APPROXIMATELY
21050KT AT AROUND 1500 FEET AGL BY MID SATURDAY EVENING...THUS
LLWS MAY BE A CONCERN SATURDAY NIGHT IF SURFACE WINDS DECOUPLE
MORE THAN EXPECTED. OTHERWISE...VFR MID-LEVEL CIGS CONTINUE TO
GRADUALLY LOWER/THICKEN BUT REMAIN ABOVE FL150 THROUGH THIS TAF
PERIOD.
RATZER
//ORD AND MDW CONFIDENCE...UPDATED 00Z...
* HIGH CONFIDENCE ALL ELEMENTS...EXCEPT MEDIUM HIGH CONFIDENCE IN
GUST TRENDS BY SATURDAY EVENING.
RATZER
//OUTLOOK FOR ORD/MDW FOR 12Z SUNDAY-12Z FRIDAY...UPDATED 00Z...
SUNDAY...CHANCE SHRA AND MVFR CIGS EARLY. WINDY. SWLY GUSTS TO 35
KT IN THE AFTERNOON.
MONDAY...CHANCE SHRA. MVFR CIGS POSSIBLE.
TUESDAY THROUGH THURSDAY...VFR.
RATZER
&&
.MARINE...
357 PM CST
WIND GUSTS HAVE BEEN SLOW TO DEVELOP TODAY DUE TO LINGERING CLOUD
COVER THAT IS INHIBITING MIXING. WITH THE COMBINATION OF LITTLE
CLOUD COVER AND COLD AIR ABOVE THE WARM LAKE...STILL EXPECTING GUSTS
TO 30 KT OVER THE SOUTHERN HALF OF THE LAKE AND GALES UP TO 35 KT
OVER THE NORTHERN HALF OF THE LAKE. SOUTHWEST FLOW CONTINUES
TOMORROW WITH GUSTS UP TO 25 KT AND INCREASING CLOUDS THROUGH THE
DAY. A DEEPENING LOW PASSES NORTH OF THE GREAT LAKES ON SUNDAY
BRINGING STRONG PRESSURE RISES BEHIND THE LOW AND CAA BEHIND THE
FRONT...GALES UP TO 45 KT ARE EXPECTED ESPECIALLY OVER THE NORTHERN
HALF OF THE LAKE. MODELS HAVE INDICATED DEEP MIXING WITH GUSTS
RANGING BETWEEN 45 AND 64 KT ACROSS THE NORTHERN HALF OF THE LAKE.
DECIDED TO STAY BELOW STORM FORCE WIND SPEEDS FOR NOW DUE TO THE
UNCERTAINTY BETWEEN THE MODELS. THAT BEING SAID...IF MODELS
CONTINUE TO SHOW POSSIBILITIES OF STORM FORCE WINDS...THE GALE WATCH
MAY BE UPGRADED TO A STORM WATCH OR WARNING.
AFTER THE SUNDAY HIGH END GALES...WINDS WILL STAY ELEVATED OUT OF
THE SOUTHWEST MONDAY INTO EARLY TUESDAY...WITH MAXIMUM WINDS IN THE
20 TO 30 KT RANGE. THEN YET ANOTHER DEEP LOW WILL MOVE NORTH OF
THE LAKE ON TUESDAY...TIGHTENING THE PRESSURE GRADIENT AND STEADILY
RAMPING WEST-SOUTHWEST WINDS UP THROUGH THE AFTERNOON. LOW END GALES
ARE POSSIBLE BY THE LATE AFTERNOON...ESPECIALLY FOR THE SOUTH HALF.
AFTER COLD FRONT PASSAGE TUESDAY EVENING...WINDS WILL TURN
WEST-NORTHWEST AND COLD AIR PUSHING ACROSS THE LAKE WILL MAKE FOR AN
UNSTABLE SET-UP AND PROLONG POSSIBLE GALES ACROSS THE ENTIRE
LAKE THROUGH TUESDAY NIGHT. HIGH PRESSURE WILL APPROACH FROM THE MID
MISSISSIPPI VALLEY LATE TUESDAY NIGHT...CAUSING WINDS TO DIMINISH
SOMEWHAT FOR THE SOUTH HALF OF THE LAKE ON WEDNESDAY...BUT THE
NORTH HALF WILL MAINTAIN A STRONGER PRESSURE GRADIENT AND BE SLOWER
TO COME DOWN.
JEE/RC
&&
.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.
&&
$$
