Heat in Illinois, July 30, 2012

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1230 PM CDT MON JUL 30 2012

.DISCUSSION...
410 AM CDT

EVENING RAOB ANALYSIS AND CURRENT GOES WATER VAPOR IMAGERY DEPICT
UPPER RIDGE CENTERED WAS OVER THE SOUTHERN PLAINS OVERNIGHT...WHILE
A SERIES OF MID-LEVEL SHORT WAVE TROUGHS WAS NOTED FROM THE FAR
UPPER MIDWEST SOUTHEAST THROUGH THE GREAT LAKES REGION. ONE OF THESE
WAS NOTED OVER WI/IL/IA PER REGIONAL VAD WIND PROFILE PLOTS...WITH A
STRONGER DISTURBANCE NOTED IN VAPOR IMAGERY OVER MN/CANADIAN BORDER
REGION. AREA OF LIGHT/ISOLATED SHOWERS FROM MID-LEVEL CLOUD DECK
OVER THE REGION APPEARS TO BE ASSOCIATED WITH INITIAL SHORT WAVE...
AND NEAR TERM GUIDANCE DEPICTS WEAK BUT PERSISTENT ISENTROPIC
UPGLIDE ALONG THE 305-310K SURFACES ALONG WITH RELATIVELY SMALL
CONDENSATION PRESSURE DEFICITS COINCIDENT WITH MID CLOUDS/LIGHT
PRECIP. MODEL FORECASTS DEPICT THIS WEAKENING BEYOND EARLY-MID
MORNING HOURS...WITH WEAK DOWNGLIDE DEVELOPING ALONG WITH DRYING AND
STRENGTHENING Q-VECTOR DIVERGENCE. THIS SUPPORTS A TREND OF
DECREASING PRECIP POTENTIAL AND CLOUD COVER FROM MID-MORNING INTO
THE AFTERNOON HOURS ACROSS THE FORECAST AREA. SURFACE LOW PRESSURE
ASSOCIATED WITH MORE AMPLIFIED MN/CANADIAN CURRENTLY OVER WESTERN
ONTARIO IS PROGGED TO MOVE NORTH OF LAKE SUPERIOR THROUGH THIS
EVENING AS THE MID-LEVEL WAVE DIGS SOUTHEAST ACROSS THE
NORTHERN/WESTERN LAKES. WEAK COLD FRONT WHICH CURRENTLY TRAILS
THROUGH MN AND THE EASTERN DAKOTAS IS SIMILARLY PROGGED TO SETTLE
SOUTHEAST ACROSS WI AND FAR NWRN IL THIS EVENING...WITH POOLING OF
HIGHER THETA-E LOW LEVEL AIR ALONG/AHEAD OF THE BOUNDARY. FORECAST
SOUNDINGS FROM VARIOUS WRF RUNS DEPICT AS MUCH AS 1500 J/KG MLCAPE
ACROSS FAR NORTHERN IL TOWARD EVENING AHEAD OF THE FRONT...WHICH
ALONG WITH LOW LEVEL CONVERGENCE AND HEIGHT FALLS ASSOCIATED WITH
DIGGING SHORT WAVE POINT TO SOME POTENTIAL FOR CONVECTION INTO AT
LEAST THE NORTHERN PARTS OF THE CWA THIS EVENING. EXPLICIT
CONVECTION MODEL RUNS (WRF-NMM...SPC WRF) SUPPORT THIS WITH
SCATTERED DEVELOPMENT ALONG/AHEAD OF THE FRONT. MID-LEVEL JET STREAK
ALONG SOUTHERN PERIPHERY OF UPPER TROUGH WILL RESULT IN INCREASING
DEEP SHEAR INTO TONIGHT ALOFT...FURTHER SUPPORTING THE CASE FOR
SCATTERED THUNDERSTORM DEVELOPMENT/ORGANIZATION. SPC HAS INCLUDED A
GOOD CHUNK OF EASTERN WI AND THE WI/IL BORDER REGION IN THE DAY 1
SLGT RISK. WITH ALL OF THIS IN MIND HAVE ADDED CHANCE THUNDER POPS
PARTICULARLY ACROSS THE NORTHERN CWA THIS EVENING...DECREASING TO
SLGT CHANCE OVERNIGHT AS THE FRONT PUSHES SOUTH. TEMPERATURE
GUIDANCE IS SHOWING QUITE A SPREAD FOR THIS AFTERNOON...WITH WRF/MET
GUIDANCE NOTABLY WARMER THAN THE GFS/MAV NUMBERS. INITIAL THOUGHT IS
THAT WRF-NAM LOW LEVEL THERMAL PROGS ARE A BIT OVERDONE...SO HAVE
UTILIZED A BLEND OF TEMP GUIDANCE IN THE UPPER 80S/AROUND 90 FOR THE
MOST PART.

TAIL OF SHORT WAVE TROUGH EXITS THE REGION TUESDAY MORNING...WITH
HEIGHT RISES AND SUBSIDENCE DEVELOPING DURING THE LATE MORNING AND
AFTERNOON HOURS. SURFACE HIGH PRESSURE BUILDS SOUTHEAST  ACROSS THE
AREA IN RESPONSE THROUGH WEDNESDAY MORNING. TEMPS NOT EXCEPTIONALLY
COOLER BEHIND THE FRONT TUESDAY...THOUGH NORTH-NORTHEAST WINDS WILL
ALLOW FOR LAKE BREEZE ENHANCEMENT WHICH WILL KEEP TEMPS ALONG THE
LAKE A LITTLE COOLER THAN FARTHER INLAND TUESDAY. SURFACE HIGH
CONTINUES TO DRIFT SOUTHEAST ACROSS THE REGION WEDNESDAY.

ANOTHER SHORT WAVE IS PROGGED THROUGH FAST WNW FLOW ACROSS THE UPPER
MIDWEST/NRN LAKES WED NGT. SFC LOW MOVES NEAR LAKE SUPERIOR BY 12Z
THURSDAY. COLD FRONT WITH THIS SYSTEM APPEARS TO STALL/WASH OUT OVER
WI OR NORTHERN IL THURSDAY NIGHT. MANY GUIDANCE SOLUTIONS INDICATE
ANOTHER EMBEDDED SHORT WAVE AND SURFACE REFLECTION FARTHER SOUTHWEST
ALONG THE FRONT IN KS/MO...AND SPREAD WARM ADVECTION PRECIP ACROSS
THE AREA IN SOME FORM THURSDAY-FRIDAY. LOW CONFIDENCE IN DETAILS OF
THIS SCENARIO...BUT HAVE MAINTAINED SOME SLGT CHANCE POPS DURING
THAT PERIOD.

GUIDANCE IS THEN FAIRLY CONSISTENT WITH A FAIRLY DEEP SHORT WAVE
ACROSS THE UPPER MIDWEST INTO WESTERN ONTARIO SATURDAY...
WITH SOUTH-SOUTHWEST WAA FLOW IN ADVANCE OF THIS FEATURE. COLD FRONT
WITH THIS SYSTEM COMES THROUGH LATE SATURDAY AFTN/EVENING...WITH
PERHAPS THE BEST CHANCE OF RAIN DURING THE FORECAST PERIOD.
HIGH PRESSURE BUILDS ACROSS THE UPPER MIDWEST/WESTERN LAKES BEHIND
THE S/WV SUNDAY.

RATZER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 18Z...

* SOUTH TO SOUTHWEST WINDS THIS AFTERNOON AND EVENING.

* SLIGHT CHANCE OF TSRA IMPACTING ORD AFTER 00Z.

PAW

//DISCUSSION...UPDATED 18Z...

A COLD FRONT WILL BE MOVING TO THE SOUTH ACROSS MN AND WI
TONIGHT...AND WILL MOVE THROUGH NORTHERN IL AND NORTHWEST IN
TUESDAY MORNING. TSRA WILL DEVELOP NEAR AND AHEAD OF THE FRONT
OVER WI THIS AFTERNOON. TSRA ARE EXPECTED TO STAY TO THE NORTH OF
THE TERMINALS...THOUGH THEY COULD GET CLOSE TO ORD AND RFD AFTER
00Z. THE CHANCES OF TSRA ACTUALLY GETTING TO THE TERMINALS IS TOO
LOW TO BE INCLUDED IN THE TAFS AT THIS TIME.

WHEN THE COLD FRONT MOVES THROUGH ON TUESDAY MORNING WINDS WILL
SHIFT FIRST TO THE WEST AND THEN TO THE NORTHWEST. THE CHICAGO
AREA TERMINALS WILL THEN SHIFT TO THE NORTHEAST IN THE AFTERNOON.

PAW

//ORD AND MDW CONFIDENCE...UPDATED 18Z...

* HIGH CONFIDENCE IN WIND TREND.

* LOW CONFIDENCE IN TSRA REACHING ORD.

PAW

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT AND WEDNESDAY...VFR.

THURSDAY AND FRIDAY...VFR. SLIGHT CHANCE TSRA/SHRA WITH
OCCASIONAL MVFR CIGS.

SATURDAY...CHANCE OF TSRA/SHRA WITH OCCASIONAL MVFR CIGS.

SUNDAY...VFR.

JEE

&&

.MARINE...
306 AM CDT

HIGH PRESSURE HAS DRIFTED EASTWARD AND IS SPREAD ACROSS THE NEW
ENGLAND AREA EARLY THIS MORNING.  A WEAK TROUGH OF LOW PRESSURE
EXTENDS FROM SOUTHEAST ONTARIO THROUGH EASTERN SOUTH DAKOTA.  THE
LOW PRESSURE AREA WILL CONTINUE EASTWARD OVER THE NORTHERN GREAT
LAKES. SOUTH TO SOUTHWEST WINDS ARE EXPECTED ACROSS THE LAKE THROUGH
THIS EVENING.  THE LOWS COLD FRONT SWEEPS ACROSS THE LAKE LATE
TONIGHT THROUGH TUESDAY MORNING WITH WINDS BECOMING NORTHWEST AND
STRENGTHENING TO 20-25 KT BEHIND THE FRONT. THE STRONG NORTH
FLOW WILL LIKELY LEAD TO A SMALL CRAFT ADVISORY AND AN INCREASED
RISK OF RIP CURRENTS FOR THE INDIANA SHORES FOR TUESDAY AND TUESDAY
NIGHT.  HIGH PRESSURE BUILDS IN BEHIND THE COLD FRONT LEADING TO
VARIABLE WINDS LESS THAN 15 KT OR LESS THAT BECOME SOUTH WEDNESDAY
NIGHT.

JEE

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

HAZARDOUS WEATHER OUTLOOK...CORRECTED
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1042 AM CDT MON JUL 30 2012

ILZ003>006-008-010>014-019>023-032-033-039-INZ001-002-010-011-019-
311545-
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-
1042 AM CDT MON JUL 30 2012 /1142 AM EDT MON JUL 30 2012/

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

.DAY ONE...THIS AFTERNOON AND TONIGHT.

  WEATHER HAZARDS EXPECTED:

  ISOLATED TO SCATTERED THUNDERSTORMS...A FEW COULD BE SEVERE AND
  MAY PRODUCE:

  WIND GUSTS IN EXCESS OF 60 MPH.
  HAIL TO 1 INCH IN DIAMETER.
  LOCALIZED DOWNPOURS.
  FREQUENT CLOUD TO GROUND LIGHTNING.

   AREAS AFFECTED AND TIMING:

   WHILE ISOLATED THUNDERSTORMS WILL BE POSSIBLE OVER MOST OF
   THE OUTLOOK AREA THIS EVENING INTO THE OVERNIGHT HOURS...
   ISOLATED STRONG TO SEVERE STORMS ARE MOST LIKELY ACROSS FAR
   NORTHERN ILLINOIS NORTH OF THE INTERSTATE 88 CORRIDOR DURING
   THE EVENING HOURS.

  DISCUSSION:

  AN AREA OF LOW PRESSURE WILL MOVE ACROSS THE NORTHERN GREAT
  LAKES REGION TODAY...AND WILL TRAIL A WEAK COLD FRONT ACROSS
  THE UPPER MIDWEST. THE FRONT IS FORECAST TO MOVE INTO FAR
  NORTHERN ILLINOIS LATE THIS EVENING...AND WILL PUSH SOUTHEAST
  ACROSS THE REMAINDER OF THE OUTLOOK AREA OVERNIGHT. WARM...
  FAIRLY HUMID AIR AHEAD OF THE FRONT IS EXPECTED TO BECOME
  MODERATELY UNSTABLE DURING THE AFTERNOON AND EARLY EVENING
  HOURS...WITH ISOLATED TO SCATTERED THUNDERSTORMS DEVELOPING
  ACROSS LAKE MICHIGAN AND SOUTHERN WISCONSIN BY LATE AFTERNOON.
  THESE STORMS WILL LIKELY MOVE SOUTHEAST INTO NORTHERN ILLINOIS
  DURING THE EVENING AHEAD OF THE FRONT. THE COMBINATION OF THE
  UNSTABLE AIR MASS AND INCREASING MID LEVEL WINDS ASSOCIATED WITH
  AN UPPER DISTURBANCE WILL SUPPORT AT LEAST AN ISOLATED THREAT OF
  SEVERE THUNDERSTORMS...WITH THE POTENTIAL FOR DAMAGING WIND
  GUSTS IN EXCESS OF 60 MPH BEING THE MAIN THREAT. THUNDERSTORMS
  SHOULD THEN DIMINISH IN COVERAGE AND WEAKEN AS THE FRONT
  CONTINUES TO MOVE TO THE SOUTHEAST OVERNIGHT.

AN AIR QUALITY ACTION DAY HAS BEEN DECLARED FOR LAKE AND PORTER
COUNTIES OF NORTHWEST INDIANA THROUGH MIDNIGHT CDT TONIGHT...DUE
TO ELEVATED OZONE LEVELS.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY.

THERE IS A SLIGHT CHANCE OF A LINGERING THUNDERSTORM EARLY
TUESDAY MORNING ACROSS PORTIONS OF NORTHWEST INDIANA.

THERE MAY BE AN INCREASED RISK OF RIP CURRENTS ALONG THE
INDIANA SHORE OF LAKE MICHIGAN TUESDAY AFTERNOON AND TUESDAY
NIGHT.

THERE IS A SLIGHT CHANCE OF PERIODIC THUNDERSTORMS ACROSS THE
OUTLOOK AREA THURSDAY THROUGH FRIDAY...THEN A GREATER CHANCE
OF THUNDERSTORMS SATURDAY AND SATURDAY NIGHT.

.SPOTTER INFORMATION STATEMENT...

SPOTTERS MAY BE NEEDED ACROSS FAR NORTHERN ILLINOIS THIS EVENING.

&&

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

LMZ740>745-311545-
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-
1042 AM CDT MON JUL 30 2012

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

.DAY ONE...THIS AFTERNOON AND TONIGHT.

THERE IS A CHANCE OF THUNDERSTORMS TONIGHT...ESPECIALLY DURING
THE EVENING HOURS. A FEW STORMS COULD BE SEVERE WITH DAMAGING
WINDS IN EXCESS OF 50 KNOTS.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY.

NORTHERLY WINDS AND BUILDING WAVES MAY LEAD TO HAZARDOUS CONDITIONS
FOR SMALL CRAFT TUESDAY AFTERNOON AND TUESDAY NIGHT PARTICULARLY
IN THE INDIANA WATERS.

THERE IS A SLIGHT CHANCE OF PERIODIC THUNDERSTORMS ACROSS THE
OUTLOOK AREA THURSDAY THROUGH FRIDAY...THEN A GREATER CHANCE
OF THUNDERSTORMS SATURDAY AND SATURDAY NIGHT.

&&

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-
870-872-874-876-878-311545-
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 TWO 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-
1042 AM CDT MON JUL 30 2012

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

.DAY ONE...THIS AFTERNOON AND TONIGHT.

THERE IS A CHANCE OF THUNDERSTORMS ACROSS CENTRAL AND NORTHERN
LAKE MICHIGAN TODAY...AND ACROSS CENTRAL AND SOUTHERN LAKE
MICHIGAN THIS EVENING. A FEW STORMS COULD BE SEVERE WITH WIND
GUSTS IN EXCESS OF 50 KNOTS.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY.

THERE IS A SLIGHT CHANCE OF PERIODIC THUNDERSTORMS ACROSS MUCH
OF LAKE MICHIGAN FROM WEDNESDAY NIGHT THROUGH THURSDAY NIGHT...
AND ACROSS FAR SOUTHERN LAKE MICHIGAN THROUGH FRIDAY. THERE IS
A GREATER THREAT OF THUNDERSTORMS ACROSS THE LAKE SATURDAY AND
SATURDAY NIGHT.

&&

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

RC