Special Weather Statement, NWS Lincoln, IL

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1240 AM CDT SUN APR 1 2012

.DISCUSSION...
ISSUED 825 PM CDT SAT MAR 31 2012

SCATTERED THUNDERSTORMS STARTING TO FIRE OVER PARTS OF CENTRAL
IOWA THIS EVENING ON NOSE OF 35-40 KT LLJ AND 850 MB WARM AXIS.
EXPECT THE STORMS TO CONTINUE TO DEVELOP AND MOVE EAST AND THEN
TURN MORE ESE ALONG THICKNESS GRADIENT LATER TONIGHT. MOST
UNSTABLE CAPES OF AROUND 1000 J/KG COUPLED WITH 40-50 KT EFFECTIVE
SHEAR MAY LEAD TO SOME HAILERS IN OUR AREA OVERNIGHT AS THE
COMPLEX TRACKS SE ACRS AT LEAST OUR NORTHEAST HALF OF THE FORECAST
AREA. SPC HAS UPDATED OUR AREA...AT LEAST THE NORTH HALF...TO A
SLIGHT RISK OVERNIGHT.

JUST WHAT AFFECT...IF ANY...THE STORMS WILL HAVE TOMORROW
ON CLOUD COVER AND TEMPS...ESP OVER OUR NORTHERN AND EASTERN
COUNTIES...REMAINS TO BE SEEN BUT MOST MODELS KEEP ALL OF OUR
AREA SOUTH OF THE ADVANCING BACKDOOR COLD FRONT SLATED TO EDGE
CLOSER TO OUR NORTH BY LATE AFTN OR EVENING. HAVE UPDATED THE
WORDING FOR THE OVERNIGHT HOURS TO SCATTERED THUNDERSTORMS ACRS
THE NORTH...AND KEPT THE LOWER CHANCE POPS GOING FURTHER SOUTH IN
CASE OF A SHARPER TURN TO THE SE LATE TONIGHT. UPDATED ZONES
SHOULD BE OUT BY 845 PM.

SMITH

&&

.AVIATION...
ISSUED 1240 AM CDT SUN APR 1 2012...FOR THE 06Z TAFS

STORMS WILL PUSH ACROSS PIA/BMI/CMI BETWEEN 06Z AND 09Z...WITH
MVFR VIS IN HEAVY RAIN AND SMALL HAIL. BASED ON UPSTREAM OBS
DURING STORMS...CIGS SHOULD REMAIN VFR DURING THE STORMS. WIND
GUSTS UP TO 35 MPH ARE POSSIBLE. LIGHTER RAIN AND MORE ISOLATED
THUNDERSTORMS ARE PROJECTED TO REACH THE SOUTHERN TERMINALS OF
SPI/DEC. STILL BRIEF PERIODS OF MVFR VIS IN RAIN IS POSSIBLE. WE
DID NOT INCLUDE TEMPOS FOR MVFR AT SPI/DEC WITH THE INITIAL
ISSUANCE...AS WE EXPECT THE LINE OF STORMS TO WEAKEN AS IT
PROGRESSES FARTHER FROM THE FAVORABLE WIND SHEAR...LLJ...AND
INSTABILITY.

SKIES ARE EXPECTED TO CLEAR RELATIVELY QUICKLY BEHIND THE LINE OF
SHOWERS/STORMS. A PERIOD OF MVFR VIS IN FOG MAY DEVELOP IN
PIA/BMI/CMI IF ANY CLEARING DEVELOPS BEFORE SUNRISE. FOG WOULD
CLEAR TO VFR BY 15Z IN THAT SCENARIO.

WINDS WILL VEER FROM SOUTHEAST TO SOUTHWEST BETWEEN 10Z-14Z...THEN
REMAIN SOUTHWEST UNTIL A BACK DOOR COLD FRONT REACHES NEAR
PIA/BMI/CMI TOWARD 06Z. THEN WINDS WILL BACK TO THE EAST BEHIND
THAT FRONT.

SHIMON
&&

.PREV DISCUSSION...
ISSUED 300 PM CDT SAT MAR 31 2012

SHORT TERM...TONIGHT THROUGH TUESDAY...
SURFACE BOUNDARY EXTENDS FROM A WEAK LOW OVER SD TO NORTHWESTERN MO
TO NEAR MEMPHIS. A SOUTHERLY LOW LEVEL NOCTURNAL JET IS EXPECTED TO
DEVELOP TONIGHT AND FOSTER CONVECTIVE DEVELOPMENT NORTH OF THE FRONT
OVER CENTRAL OR EASTERN IA AS RELATIVELY MOIST AIR PARCELS ARE
LIFTED ISENTROPICALLY ABOVE THE FRONTAL INVERSION. THIS ACTIVITY
WILL THEN MOVE EAST-SOUTHEAST WITH THE MEAN FLOW INTO ABOUT THE
NORTHERN HALF OF IL AFTER MIDNIGHT...LINGERING IN THE EAST DURING
THE MORNING HOURS. STEEP MID LEVEL LAPSE RATES AND ELEVATED
INSTABILITY ALONG WITH ADEQUATE EFFECTIVE SHEAR MAY LEAD TO HAIL
DEVELOPMENT IN THE STRONGER STORMS...BUT THE PROSPECTS FOR ORGANIZED
SEVERE WEATHER AS FAR SOUTHEAST AS CENTRAL IL LOOK SLIM DUE TO
WEAKENING OF THE INSTABILITY AND WIND FIELDS WITH EASTWARD EXTENT.

THE SURFACE BOUNDARY IS FORECAST TO LIFT NORTHEASTWARD INTO NORTHERN
ILLINOIS SUNDAY AFTERNOON...BUT HOW FAR WILL DEPEND ON HOW ORGANIZED
THE PRECEDING MORNING STORMS GET. A MAJORITY OF THE MODEL OUTPUT
SHOWS MOST IF NOT ALL OF CENTRAL IL GETTING INTO THE WARM SECTOR...
WITH 850 MB TEMPERATURES EASILY SUPPORTING HIGHS WELL INTO THE 80S
BOTH SUNDAY AND MONDAY. SOME RECORD HIGHS MAY BE ATTAINED AT A FEW
LOCATIONS AS DETAILED IN THE CLIMATE SECTION BELOW.

AN UPPER LOW OFF THE COAST OF CA IS EXPECTED TO MOVE INTO THE
SOUTHERN PLAINS BY EARLY TUESDAY...WHILE A NORTHERN STREAM SHORTWAVE
MOVES ACROSS SOUTHERN CANADA. THIS WILL PRESENT A COMPLICATED
SCENARIO WITH THE MODELS IN DISAGREEMENT REGARDING THE DISTRIBUTION
OF ENERGY BETWEEN THE NORTHERN AND SOUTHERN STREAMS. FOR NOW WILL
COUNT ON A COLD FRONT TO MOVE THROUGH IL ASSOCIATED WITH THE
NORTHERN STREAM WAVE ON TUESDAY...WITH CHANCE POPS BEGINNING MONDAY
NIGHT AND EXTENDING THROUGH TUESDAY NIGHT.

LONG TERM...WEDNESDAY THROUGH SATURDAY...
THE ABOVE-MENTIONED UPPER LOW WILL BE MOVING SLOWLY AND CROSS TO THE
SOUTH OF IL AROUND THURSDAY. THIS WILL REQUIRE KEEPING SHOWERS IN
THE FORECAST THROUGH THEN...WITH LOWER POPS IN THE NORTH WHERE HIGH
PRESSURE IS EXPECTED TO PUSH DRIER AIR SOUTHWARD FROM CANADA. THE
MODEL DIFFERENCES CONTINUE THROUGH NEXT WEEKEND AS THE FASTER GFS
PUSHES THE NEXT FRONT INTO THE MIDWEST BY SATURDAY...WHILE THE ECMWF
STILL HAS THIS FRONT OUT WEST IN THE PLAINS BY SATURDAY. WILL KEEP A
DRY FORECAST FROM THURSDAY NIGHT ON...BUT WITH A LOW CONFIDENCE. THE
LONGER RANGE MODELS HAVE HAD MORE THAN AVERAGE DIFFICULTY WITH
SOUTHWESTERN UPPER LOWS FOR THE ENTIRE SEASON...AND THIS CASE IS NO
EXCEPTION.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

HAZARDOUS WEATHER OUTLOOK...UPDATED
NATIONAL WEATHER SERVICE LINCOLN IL
820 PM CDT SAT MAR 31 2012

ILZ027>031-036>038-040>046-048-053>057-011100-
CHAMPAIGN-COLES-DE WITT-DOUGLAS-EDGAR-FULTON-KNOX-LOGAN-MACON-
MARSHALL-MASON-MCLEAN-MENARD-MOULTRIE-PEORIA-PIATT-SCHUYLER-STARK-
TAZEWELL-VERMILION-WOODFORD-
820 PM CDT SAT MAR 31 2012

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF CENTRAL ILLINOIS
AND EAST CENTRAL ILLINOIS.

.DAY ONE...TONIGHT

SCATTERED THUNDERSTORMS WILL BE POSSIBLE LATE TONIGHT AS A WEATHER
DISTURBANCE DEVELOPS IN IOWA AND MOVES ACROSS NORTHERN ILLINOIS.
THE PRIMARY THREAT FROM THE THUNDERSTORMS OVERNIGHT WILL BE FROM
HAIL UP TO THE SIZE OF QUARTERS.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY

THUNDERSTORMS WILL BE POSSIBLE EARLY SUNDAY MORNING BEFORE THE
STORM SYSTEM MOVES OFF TO THE NORTHEAST. A FEW OF THE STORMS
EARLY IN THE MORNING MAY CONTINUE TO POSE A THREAT FOR HAIL.

ANOTHER ROUND OF THUNDERSTORMS WILL AFFECT THE AREA MONDAY
NIGHT AND TUESDAY.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE NEEDED DURING THE EARLY MORNING
HOURS...ROUGHLY FROM 200 AM UNTIL 800 AM.

ILZ047-049>052-061>063-066>068-071>073-011100-
CASS-CHRISTIAN-CLARK-CLAY-CRAWFORD-CUMBERLAND-EFFINGHAM-JASPER-
LAWRENCE-MORGAN-RICHLAND-SANGAMON-SCOTT-SHELBY-
820 PM CDT SAT MAR 31 2012

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF CENTRAL
ILLINOIS...EAST CENTRAL ILLINOIS AND SOUTHEAST ILLINOIS.

.DAY ONE...TONIGHT

THERE IS A CHANCE OF THUNDERSTORMS DEVELOPING LATE TONIGHT...BUT THE
MAJORITY OF THE STORMS SHOULD STAY JUST TO OUR NORTH OVERNIGHT.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY

ANOTHER ROUND OF THUNDERSTORMS WILL AFFECT THE AREA MONDAY
NIGHT AND TUESDAY.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS NOT ANTICIPATED THROUGH TONIGHT.

SMITH

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