Gale Warning 38, NWS Chicago, IL

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
319 AM CDT SAT OCT 25 2008

.DISCUSSION...

332 PM CDT

MAIN FORECAST CONCERNS ARE PRECIP/THUNDER POTENTIAL TONIGHT AND
COLDER AND VERY WINDY CONDITIONS SUNDAY/SUNDAY NIGHT WHICH MAY
ULTIMATELY REQUIRE WIND HEADLINES FOR ADVSRY OR WARNING.

SHORT TERM FOCUS FOR PRECIP CONTINUES TO BE VORT MAX ASSOCIATED
WITH CLOSED OFF MID LEVEL LOW OVER NORTHERN MO/IA THIS AFTERNOON.
BAND OF PRECIP FROM WESTERN IL INTO EASTERN IA AHEAD OF THIS
FEATURE EXPECTED TO SPREAD INTO AREA THIS EVENING. HAVE MAINTAINED
CATEGORICAL POPS OVERNIGHT AS VORT ASSOCIATED WITH THIS
CIRCULATION TRANSLATES EASTWARD ACROSS FORECAST AREA AS WAVE
FINALLY BEGINS TO ACCELERATE. FORECAST SOUNDINGS FROM 12Z RUNS
OF BOTH NAM AND GFS INDICATE WEAK INSTABILITY LATE THIS
AFTERNOON/THIS EVENING WITH 100-300 J/KG ML CAPE NOTED AS WELL AS
6.5-7 DEG/KM MID LEVEL LAPSE RATES SPREADING ACROSS ESPECIALLY
WESTERN PORTIONS OF FORECAST AREA...AND IN FACT A FEW LIGHTNING
STRIKES NOW DETECTED IN CONVECTIVE SHOWERS FROM PEORIA NORTH
TOWARD STERLING. BASED ON THIS WILL ADD MENTION OF ISOLATED
THUNDER THROUGH EARLY EVENING ACROSS AREAS MAINLY WEST OF CHICAGO.

VORT AND UPPER TROUGH AXIS THEN MOVE EAST SATURDAY MORNING.
DOWNWARD VERTICAL MOTION AS INDICATED BY OMEGA/Q VECTOR DIVERGENCE
FIELDS INDICATE SUBSIDENCE BY AFTERNOON...IN RESPONSE TO
FAIRLY STRONG HEIGHT RISES BEHIND DEPARTING WAVE. WHILE CLOUDS AND
A FEW SHOWERS MAY LINGER DURING THE MORNING...EXPECT SOME
SCATTERING OF CLOUDS DURING AFTERNOON THOUGH FORECAST SOUNDINGS
DEPICT SOME MOISTURE TRAPPED BENEATH DEVELOPING SUBSIDENCE
INVERSION AND ELEVATED WAA WHICH DEVELOPS FROM WEST LATER IN DAY.

150+ KNOT UPPER JET THEN BEGINS TO DIG ACROSS CENTRAL NOAM
SATURDAY NIGHT INDUCING LARGE SCALE AMPLIFICATION OF UPPER TROUGH
ACROSS EASTERN CONUS. FLOW INITIALLY ZONAL...WITH LITTLE MOIST
RETURN ON WESTERLY LOW LEVEL WINDS. BECOMING BREEZY OVERNIGHT
WITH WEST/SOUTHWEST WINDS 10-20 MPH. BEST DPVA REMAINS NORTH OF
CWA ALONG NORTHERN PERIPHERY OF JET AXIS...THUS VRY MINOR PCPN
THREAT. TEMPS LIKELY NOT FALLING OFF TOO MUCH GIVEN WIND/LLVL WAA.

STRONG SFC COLD FRONT PLOWS INTO CWA SUN MRNG. VRY DRY LLVL AMS
BEHIND FRONT...SFC DWPTS IN TEENS POST FROPA INDICATED ACROSS NWRN
IL BY AFTN. FCST SOUNDINGS CONTINUE TO INDICATE VERY STEEP LLVL
LAPSE RATES TO 850-700 HPA WITH POTENTIAL WIND ADVSRY/WRNG
CONDITIONS DEVELOPING WITH WNW GUSTS 40-50 PER 12Z NAM/GFS BUFKIT
SNDGS. STEADY/FALLING TEMPS ESPECIALLY NCNTRL IL WHERE FROPA
OCCURS EARLIEST IN THE DAY.

VORT DIGS SE ACROSS AREA SUN EVE...THOUGH WITH SFC DWPTS IN TEENS
AND CLOUD BASES 7-8 KFT. FEEL THAT PCPN WILL HAVE A HARD TIME
DVLPG DRY LLVLS. WITH LOW SFC WET BULB...STRONG EVAPORATIVE
COOLING COULD RESULT IN THERMAL PROFILE SUPPORTIVE OF SNOW BY LATE
SUNDAY AFTERNOON...THOUGH GIVEN LACK OF STRONG PRECIP/EVAPORATIVE
COOLING WOULD THINK ANYTHING THAT WOULD FALL WOULD REMAIN VIRGA OR
LIQUID. HAVE DECIDED TO DOWNPLAY ANY SPRINKLE/FLURRY MENTION AT
THIS TIME. PASSAGE OF VORT/Q DIV AND LACK OF DPVA SUGGEST LITTLE
VERTICAL MOTION SUPPORT FOR PCPN OVRNGT AND SNDGS INDICATE
SUBSIDENCE INERSION DVLPG BY MORNING.

LITTLE CHANGE TO THINKING IN EXTENDED AS UPPER TROUGH CONTINUES TO
BE PROGRESSIVE AND MOVES SLOWLY AWAY TO THE EAST THROUGH MID WEEK.
THUS AFTER A COUPLE OF DAYS WITH HIGHS IN THE LOW/MID 40S...AND
OVERNIGHT LOWS IN THE UPPER 20S/LOW 30S...SHOULD SEE MODERATION IN
TEMPS BY MID/END OF WEEK. STILL MAY HAVE FROST/FREEZE CONSIDERATIONS
SUNDAY NIGHT THRUOGH EARLY WEDNESDAY...THOUGH WILL ADDRESS THOSE
AS THEY ENTER NEAR TERM.

RATZER

&&

.AVIATION...

06Z TAFS...MAIN AREA OF RAIN LIFTING NORTHEAST AWAY FROM THE TAFS
EARLY THIS MORNING. STILL SOME LINGERING LIGHT SHOWERS/SPRINKLES
ACROSS PARTS OF NORTHERN IL. NOT SURE THESE WILL AMOUNT TO MUCH
BUT DECIDED TO CARRY A VCSH FOR A FEW HRS BUT THE BULK OF THE RAIN
IS OVER. CIGS ALL OVER THE PLACE ACROSS THE AREA BUT OBSERVATIONS
AND GUIDANCE TEND TO SUPPORT GENERALLY MVFR CIGS THRU MID MORNING
THEN CIGS LIFTING TO VFR BY LATE MORNING AND REMAINING VFR FOR THE
REMAINDER OF THE PERIOD. DRIER AIR SLOWLY ADVECTING ACROSS THE
AREA THIS MORNING AND NOT EXPECTING MUCH...IF ANY VIS RESTRICTION
FROM LIGHT FOG.

ONLY OTHER CONCERN THIS PERIOD WILL BE THE WINDS. WSW WINDS 10KTS
WILL CONTINUE THRU SUNRISE THEN BEGIN TO INCREASE TO 10-20KTS WITH
GUSTS TO 25KTS BY EARLY AFTERNOON. GUSTS MAY RELAX A LITTLE WITH
SUNSET BUT STILL BREEZY THRU THE END OF THE PERIOD. DIRECTION
LOOKS PRETTY STEADY...GENERALLY WSW PERHAPS TURNING MORE SOUTHWEST
THIS EVENING. CMS

&&

.MARINE...

319 AM...MAIN CONCERN REMAINS POWERFUL COLD FRONT TO MOVE ACROSS
THE WESTERN LAKES EARLY SUNDAY MORNING. AS DEEP LOW PRESSURE MOVES
ACROSS NORTHERN ONTARIO LATER TODAY AND TONIGHT...THE GRADIENT
WILL CONTINUE TO TIGHTEN...ALLOWING SOUTHWESTERLY WINDS TO
INCREASE TO 30KTS. WINDS MAY REACH GALE FORCE PRIOR TO THE ARRIVAL
OF THE COLD FRONT. VERY COLD AIR ALOFT SEEN ON MODEL SOUNDINGS
WILL MIX TO THE SFC OF THE LAKE...BRINGING DOWN WIND GUSTS 45-50
KNOTS. STRONGEST PUSH OF COLD AIR/STRONG WINDS APPEARS TO BE
ACROSS THE SOUTHERN HALF OF LAKE MICHIGAN. WIND SPEEDS/GUSTS ARE
ON THE THRESHOLD OF STORM FORCE WHICH IS 48KTS. GIVEN THE EXTENT
OF COLD AIR...IN ADDITION TO ALREADY STRONG FLOW PRIOR TO
FROPA...HAVE DECIDED TO GO WITH A STORM WARNING FOR THE SOUTHERN
HALF OF LAKE MICHIGAN...INCLUDING THE IL/IN NEARSHORE WATERS. THE
LENGTH OF TIME OF THE STORM FORCE WINDS WILL BE RATHER SHORT...
PERHAPS ONLY 6 TO 9 HRS. HAVE HOISTED THE STORM WARNING FROM 10Z
SUNDAY THRU 00Z MONDAY. EVENTUALLY...ONCE WINDS DIMINISH THE STORM
WARNING WILL NEED TO BE REPLACED BY A GALE WARNING. TO AVOID
CONFUSION WITH HEADLINES...NO RAMPING DOWN WITH A GALE WARNING
UNTIL THE STORM WARNING IS DONE.

ELSEWHERE HOISTED A GALE WARNING FOR THE NORTH HALF AND CONTINUED
THAT THRU LATE MORNING MONDAY. GALES SHOULD BE DIMINISHING BY
MIDDAY MONDAY. BUT WINDS TO 30KTS WILL BE SLOW TO DIMINISH MONDAY
NIGHT INTO TUESDAY MORNING. FOR THE NEARSHORE WATERS...SOUTHWEST
FLOW CONTINUES TO INCREASE TODAY SO HAVE MOVED UP THE START TIME
OF THE GOING SMALL CRAFT ADVISORY TO LATE THIS MORNING AND
CONTINUED THAT UNTIL THE STORM WARNING KICKS IN. CMS

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...WIND ADVISORY...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-ILZ010-ILZ011-
     ILZ012-ILZ013-ILZ014-ILZ019-ILZ020-ILZ021-ILZ022-ILZ023-
     ILZ032-ILZ033-ILZ039...7 AM SUNDAY TO 7 PM SUNDAY.

IN...WIND ADVISORY...INZ001-INZ002-INZ010-INZ011-INZ019...7 AM SUNDAY
     TO 7 PM SUNDAY.

LM...STORM WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878...5 AM SUNDAY TO 7 PM SUNDAY.

     GALE WARNING...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
     LMZ868...3 AM SUNDAY TO 10 AM MONDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...11 AM SATURDAY TO 5 AM SUNDAY.

&&

HAZARDOUS WEATHER OUTLOOK...UPDATED
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
655 PM CDT FRI OCT 24 2008

ILZ003>006-008-010>014-019>023-032-033-039-INZ001-002-010-011-019-
252145-
WINNEBAGO-BOONE-MCHENRY-LAKE ILLINOIS-OGLE-LEE-DE KALB-KANE-
DUPAGE-COOK-LA SALLE-KENDALL-GRUNDY-WILL-KANKAKEE-LIVINGSTON-
IROQUOIS-FORD-LAKE INDIANA-PORTER-NEWTON-JASPER-BENTON-
655 PM CDT FRI OCT 24 2008 /755 PM EDT FRI OCT 24 2008/

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF NORTH CENTRAL
ILLINOIS...NORTHEAST ILLINOIS AND NORTHWEST INDIANA.

.DAY ONE...TONIGHT.

ISOLATED THUNDERSTORMS ARE POSSIBLE EARLY THIS EVENING.

.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY.

STRONG WEST WINDS ARE EXPECTED TO DEVELOP ON SUNDAY AS COLD AIR
SWEEPS ACROSS THE MIDWEST. WINDS ARE EXPECTED TO GUST TO AROUND
40 MPH BY SUNDAY AFTERNOON...AND CONTINUE INTO SUNDAY NIGHT.

ALSO...TEMPERATURES ARE FORECAST TO DROP BELOW FREEZING SUNDAY
NIGHT...AND AGAIN MONDAY NIGHT WHEN A HARD FREEZE IS POSSIBLE
AWAY FROM THE CITY OF CHICAGO.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION WILL NOT BE NECESSARY THROUGH TONIGHT.

&&

COMPLETE FORECAST INFORMATION IS AVAILABLE ON THE NWS CHICAGO
WEBPAGE: WEATHER.GOV/CHICAGO

LMZ740>745-252145-
WINTHROP HARBOR TO WILMETTE HARBOR-
WILMETTE HARBOR TO NORTHERLY ISLAND-
NORTHERLY ISLAND TO CALUMET HARBOR-CALUMET HARBOR TO GARY-
GARY TO BURNS HARBOR-BURNS HARBOR TO MICHIGAN CITY-
655 PM CDT FRI OCT 24 2008

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF THE ILLINOIS
NEARSHORE WATERS OF LAKE MICHIGAN AND THE INDIANA NEARSHORE
WATERS OF LAKE MICHIGAN.

.DAY ONE...TONIGHT.

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY.

STRONG WEST WINDS...POSSIBLY TO GALE FORCE...ARE FORECAST TO
DEVELOP EARLY SUNDAY MORNING AND CONTINUE THROUGH MONDAY. THIS
SHOULD BE PRECEDED BY A SMALL CRAFT ADVISORY STARTING SATURDAY
AFTERNOON.

&&

COMPLETE FORECAST INFORMATION IS AVAILABLE ON THE NWS CHICAGO
WEBPAGE: WEATHER.GOV/CHICAGO

LMZ080-261-362-364-366-563-565-567-669-671-673-675-777-779-868-
870-872-874-876-878-252145-
LAKE MICHIGAN FROM MICHIGAN CITY IN TO ST. JOSEPH MI 5 NM
OFFSHORE TO MID LAKE-
LAKE MICHIGAN FROM SEUL CHOIX POINT TO ROCK ISLAND PASSAGE 5 NM
OFFSHORE TO MID LAKE-
LAKE MICHIGAN SOUTH OF A LINE FROM SEUL CHOIX POINT TO THE
MACKINAC BRIDGE AND NORTH OF A LINE FROM CHARLEVOIX MI TO SOUTH
FOX ISLAND 5 NM OFFSHORE-
LAKE MICHIGAN FROM CHARLEVOIX TO POINT BETSIE MI 5 NM OFFSHORE TO
MID LAKE-
LAKE MICHIGAN FROM POINT BETSIE TO MANISTEE MI 5 NM OFFSHORE TO
MID LAKE-
LAKE MICHIGAN FROM ROCK ISLAND PASSAGE TO STURGEON BAY WI-
LAKE MICHIGAN FROM STURGEON BAY TO TWO RIVERS WI 5 NM OFFSHORE TO
MID LAKE-
LAKE MICHIGAN FROM TOW RIVERS TO SHEBOYGAN WI 5 NM OFFSHORE TO
MID LAKE-
LAKE MICHIGAN FROM SHEBOYGAN TO PORT WASHINGTON WI 5 NM OFFSHORE
TO MID LAKE-
LAKE MICHIGAN FROM PORT WASHINGTON TO NORTH POINT LIGHT WI 5 NM
OFFSHORE TO MID LAKE-
LAKE MICHIGAN FROM NORTH POINT LIGHT TO WIND POINT WI 5 NM
OFFSHORE TO MID LAKE-
LAKE MICHIGAN FROM WIND POINT WI TO WINTHROP HARBOR IL 5 NM
OFFSHORE TO MID LAKE-
LAKE MICHIGAN FROM WINTHROP HARBOR TO WILMETTE HARBOR IL 5 NM
OFFSHORE TO MID LAKE-
LAKE MICHIGAN FROM WILMETTE HARBOR IL TO MICHIGAN CITY IN 5 NM
OFFSHORE TO MID LAKE-
LAKE MICHIGAN FROM PENTWATER TO MANISTEE MI 5 NM OFFSHORE TO MID
LAKE-
LAKE MICHIGAN FROM WHITEHALL TO PENTWATER MI 5 NM OFFSHORE TO MID
LAKE-
LAKE MICHIGAN FROM GRAND HAVEN TO WHITEHALL MI 5 NM OFFSHORE TO
MID LAKE-
LAKE MICHIGAN FROM HOLLAND TO GRAND HAVEN MI 5 NM OFFSHORE TO MID
LAKE-
LAKE MICHIGAN FROM SOUTH HAVEN TO HOLLAND MI 5 NM OFFSHORE TO MID
LAKE-
LAKE MICHIGAN FROM ST. JOSEPH TO SOUTH HAVEN MI 5 NM OFFSHORE TO
MID LAKE-
655 PM CDT FRI OCT 24 2008

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF THE OPEN WATERS
OF LAKE MICHIGAN.

.DAY ONE...TONIGHT.

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY.

GALE FORCE WEST WINDS OF 45 KNOTS ARE EXPECTED TO DEVELOP BY
EARLY SUNDAY...AND CONTINUE INTO MONDAY AFTERNOON...THUS A GALE
WATCH HAS BEEN ISSUED FOR SUNDAY THROUGH MONDAY AFTERNOON.

&&

COMPLETE FORECAST INFORMATION IS AVAILABLE ON THE NWS CHICAGO
WEBPAGE: WEATHER.GOV/CHICAGO

RLB