Hail in Illinois, May 27, 2005

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
ISSUED BY NWS LINCOLN
230 PM CDT FRI MAY 27 2005

.DISCUSSION FOR AFTERNOON ZFP/GRIDS...
BIGGEST CHALLENGE THIS AFTERNOON IS TIMING OF PRECIP CHANCES INTO
EARLY NEXT WEEK.

LARGE COLD VORTEX CONTINUES TO CHURN OVER LAKE WINNEPEG PRODUCING
OCCASIONAL LOBES THAT ROTATE DOWN THROUGH NORTHERN ILLINOIS THROUGH
THE HOLIDAY WEEKEND.  ALTHOUGH THE MODELS ARE SIMILAR ON THE
EVOLUTION OF THE LOW INTO A SLOW MOVING ELONGATED STRUCTURE...MODELS
DIFFER SIGNIFICANTLY ON TIMING AND STRENGTH OF LOBES MAKING A
DETERMINATION OF PRECIP AND DRY PERIODS SOMEWHAT DIFFICULT.  BASED
ON INTIALIZATION WITH RESPECT TO LOBE MOVING OUT OF IOWA AND SECOND
LOBE IN SOUTHEAST SOUTH DAKOTA...IT APPEARS THAT GFS MAY HAVE BEST
INITIAL HANDLE ON ENERGY ROTATING AROUND SYSTEM AND WILL GENERALLY
FOLLOW GFS INTO EARLY NEXT WEEK.

DIURNAL INDUCED INSTABILITY IS TOUCHING OFF SHOWERS OVER NORTHERN
ILLINOIS THIS AFTERNOON. RUC ANALYSIS SHOWING -22C 500 MB TEMPS
MOVING INTO REGION PRODUCING SIGNIFICANT LAPSE RATES. LACK OF A LOW
LEVEL FOCUS SHOULD KEEP ORGANIZATION LIMITED. SOME SMALL HAIL OR
GUSTY WINDS IS NOT OUT OF THE QUESTION LATE THIS AFTERNOON AND INTO
THIS EVENING FROM LOW TOPPED CONVECTION. HOWEVER...WITH DIMINISHING
SOLAR HEATING THE STORMS SHOULD DISSIPATE QUICKLY SOON AFTER DARK.

GFS SUGGESTS NEXT SIGNIFICANT CHANCE OF PRECIPITATION WILL HOLD OFF
UNTIL SUNDAY AND SUNDAY NIGHT. CONVECTIVE FEEDBACK IS LIKELY
CONTAMINATING THE 12Z GFS FOR THIS PERIOD...AND THE GFS ENSEMBLE
MEAN DOES SUGGEST A DRIER SOLUTION.  HOWEVER...IT APPEARS THAT WE
WILL HAVE A BOUNDARY PASSAGE ALLOWING SOME SURFACE CONVERGENCE. WILL
INCREASE ONLY TO 30 POPS AND ALLOW FUTURE PACKAGES TO TREND IF FURTHER
INCREASES ARE NECESSARY.

500 MB LOW IS CLOSEST TO NORTHEASTERN ILLINOIS ON MONDAY...BUT
SURFACE BOUNDARY AND MAIN LOBE IS EAST OF AREA. ALTHOUGH LAPSE RATE
MAY BE SUFFICIENT TO PRODUCE SOME ADDITIONAL POST FRONTAL
CONVECTION...WILL ONLY GO 20 POPS GIVEN UNCERTAINTY IN TIMING AND
POTENTIAL SUBSIDENCE IN WAKE OF SUNDAY NIGHT WAVE.

HEIGHTS INCREASE AS SURFACE AND SHORTWAVE RIDGE BUILD INTO THE
REGION OVER THE REMAINDER OF THE WEEK. PRECIP DEVELOPING OVER
CENTRAL PLAINS SHOULD HAVE DIFFICULTY MAKING IT EAST TO THE GREAT
LAKES GIVEN THE STEADY MIDLEVEL HEIGHT RISES AND THE SLOW EXIT OF
THE 5H LOW OVER THE CANADIAN MARITIMES. GULF MAY FINALLY OPEN SOME
TOWARD THE END OF THE WEEK...BUT GIVEN THE DRY CONDITIONS IN PLACE
OVER THE MIDWEST AND THE SLOW PROGRESSION OF ENERGY TOWARD THE
AREA...FAVOR LEAVING FRIDAY DRY FOR NOW.

BARKER

&&

.AVIATION...
ISSUED BY NWS CHICAGO/ROMEOVILLE IL
1255 PM CDT

RE 18Z TAFORS...MINOR SHR/WV MOVG ACROSS CHI VC ATTM ENHANCING
DIURNAL CONVECTION AND SCT SHRA...FOLLOWED BY SHRT/WV TROF MOVG E
ACROSS SRN MN AND IA. UVV WITH THIS IMPULSE COMBINED WITH DAYTIME
HEATING WILL RESULT IN CONT DVLPMNT OF SHRA AND TSRA INTO SWRN WI
AND E CNTRL IA ERLY AFTERNOON...AND MOVG INTO RFD VC ERLY AFTERNOON
AND CHI VC MID AFTERNOON. ACTIVITY TO DEC DURG EVE WITH LOSS OF
HEATING...THO WILL STILL BE SOME SHRA AROUND AS ANOTHER MINOR
IMPULSE CURRENTLY NR ERN SD/NEB BORDER MOVS ACROSS NRN IL DURG
ERLY-MID EVE. SFC WNDS...OUTSIDE OF TSRA...AT MAX NOW FOR AFTERNOON
AS LWR TROP WELL MIXED. DIURNAL DEC/INC TONIGHT AND SAT MORNING.
&&

.LOT...WATCHES/WARNINGS/ADVISORIES...
.IL...NONE.
.IN...NONE.
.LK MI...NONE.

HAZARDOUS WEATHER OUTLOOK...UPDATED
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
115 PM CDT FRI MAY 27 2005

ILZ003>006-008-010>014-019>022-023-032-033-039-INZ001-002-010-011-019
-281100-
WINNEBAGO-BOONE-MCHENRY-LAKE IL-OGLE-LEE-DE KALB-KANE-DU PAGE-COOK-
LA SALLE-KENDALL-GRUNDY-WILL-KANKAKEE-LIVINGSTON-IROQUOIS-FORD-
LAKE IN-PORTER-NEWTON-JASPER-BENTON-
115 PM CDT FRI MAY 27 2005

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

.DAY ONE... THIS AFTERNOON AND TONIGHT

SCATTERED SHOWERS AND THUNDERSTORMS WILL AFFECT THE OUTLOOK AREA
THIS AFTERNOON THROUGH THIS EVENING...BEFORE DIMINISHING WITH
SUNSET. THERE IS A SLIGHT CHANCE THAT SOME OF THE STRONGER ISOLATED
STORMS COULD PRODUCE HAIL OR WIND GUSTS UP TO SEVERE LIMITS MAINLY
DURING THE MID TO LATE AFTERNOON HOURS.

.DAYS TWO THROUGH SEVEN... SATURDAY THROUGH THURSDAY

THE PROBABILITY FOR WIDESPREAD HAZARDOUS WEATHER IS LOW.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE NECESSARY THIS AFTERNOON.

&&

COMPLETE FORECAST INFORMATION IS AVAILABLE ON THE
NWS CHICAGO WEBPAGE: WEATHER.GOV/CHICAGO (LOWER CASE)

LMZ740>745-766-281100-
WINTHROP HARBOR IL TO NEW BUFFALO MI-
LAKE MICHIGAN-
115 PM CDT FRI MAY 27 2005

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

.DAY ONE... THIS AFTERNOON AND TONIGHT

SCATTERED SHOWERS AND THUNDERSTORMS WILL AFFECT SOUTHERN LAKE
MICHIGAN THIS AFTERNOON THROUGH THIS EVENING. THERE IS A SLIGHT
CHANCE THAT SOME OF THE STRONGER ISOLATED THUNDERSTORMS COULD
PRODUCE HAIL OR WIND GUSTS NEAR SEVERE LIMITS...MAINLY DURING THE
MID AND LATE AFTERNOON HOURS.

.DAYS TWO THROUGH SEVEN... SATURDAY THROUGH THURSDAY

THE PROBABILITY FOR WIDESPREAD HAZARDOUS WEATHER IS LOW.

&&

COMPLETE FORECAST INFORMATION IS AVAILABLE ON THE
NWS CHICAGO WEBPAGE: WEATHER.GOV/CHICAGO (LOWER CASE)