Area Forecast Discussion
Issued by NWS Central Illinois

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000
FXUS63 KILX 050833
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
333 AM CDT TUE MAY 5 2015

.SHORT TERM...(TODAY)
ISSUED AT 332 AM CDT TUE MAY 5 2015

A FRONTAL BOUNDARY IS ORIENTED WEST-EAST ACROSS CENTRAL IL THIS
MORNING WITH PRECIPITATION IN ISENTROPIC ASCENT REGION LARGELY TO
THE NORTH OF THE BOUNDARY. MODELS INDICATE THE BOUNDARY AND
PRECIPITATION WILL SHIFT SLOWLY NORTHWARD TODAY. WEAK DISTURBANCES
MOVING ALONG THE BOUNDARY WILL PRODUCE SOME ENHANCEMENTS IN
CONVECTIVE SHOWER COVERAGE IN THE VICINITY...EARLY THIS MORNING FROM
AROUND THE ILLINOIS RIVER NORTHWESTWARD...AND LATE IN THE AFTERNOON
NORTH OF THE I-74 CORRIDOR. FOR THE MOST PART...CONVECTION SHOULD BE
WEAK AT THIS POINT WITH ONLY WEAK MID-LEVEL INSTABILITY REMAINING
THROUGH THE NIGHT...AND 0-6KM BULK SHEAR UP TO 25-30 KTS THIS
MORNING DIMINISHING SUBSTANTIALLY FOR THE AFTERNOON. 1000-1500
JOULES OF SURFACE-BASED CAPE SHOULD BE ABLE TO DEVELOP WITH
AFTERNOON HEATING ALONG/NORTH OF I-72 AND CAN`T RULE OUT ISOLATED
THUNDERSTORMS SOUTHWARD TO I-72 AS A RESULT.

&&

.LONG TERM...(TONIGHT THROUGH MONDAY)
ISSUED AT 332 AM CDT TUE MAY 5 2015

ONGOING CONVECTION ALONG THE BOUNDARY OVER NORTHERN ILLINOIS THIS
MORNING NOT ONLY DRIVING THE WEATHER THROUGHOUT THE DAY, BUT INTO
THE OVERNIGHT AS WELL. GFS AND NAM CONTINUE TO KEEP A BIT OF PRECIP
PRETTY FAR SOUTH, AS FAR SOUTH AS A LINE FROM HAVANA TO BLOOMINGTON.
HOWEVER, THE RAP/RUC AND THE HRRR ARE PUSHING THE AREA OF CONVECTION
WELL TO THE NORTH THROUGH THE MORNING WITH THE BOUNDARY. WHEN THE
SECONDARY WAVE RIPPLES THROUGH THE REGION AFTER 00Z, IT WOULD BE
DISPLACED NORTH OF THE FA.  THE 4KM WRF HAS JUST THAT SOLUTION,
STARTING MORE IN LINE WITH THE RAP/RUC AND HRRR...AND KEEPING THE FA
DRY AFTER 00Z, BUT A LITTLE MORE GENEROUS WITH SOME ISOLATED
INSTABILITY SHOWERS.  HAVE KEPT ISO TS IN THE NORTH, MAINLY ALONG
AND NORTH OF I-74 FOR THE EARLY EVENING.

HIGH PRESSURE BEGINS TO BUILD BACK INTO THE REGION LATER TONIGHT,
SOUTHERLY WINDS PUSHING THE FRONT BACK TO THE NORTH AND OUT OF THE
FORECAST AREA THROUGH WED NIGHT. FORECAST REMAINS ROUGHLY THE SAME
BEYOND DAY 3... PRECIP CHANCES SLOWLY EDGING BACK INTO WEST CENTRAL
ILLINOIS FOR THURSDAY AS AN UPPER LEVEL WAVE PUSHES OUT OF THE SW.
THE ENERGY IS PART OF A GENERAL PATTERN SHIFT TO MORE SOUTHWESTERLY
FLOW WITH THE UPPER LEVEL TROF DIGGING BACK IN OVER THE SWRN CONUS.
THE SFC LOW MOVES OUT INTO THE UPPER MIDWEST AND INTO CANADA BY THE
END OF THE WEEK, BUT IN SHIFTING TO MORE SOUTHWESTERLY FLOW ALOFT,
OPENS THE DOOR TO A SERIES OF SHORTWAVES THAT KEEP THE FORECAST WET
FOR THE END OF THE WORK WEEK AND INTO THE WEEKEND.  TEMPS RATHER
WARM THROUGH THE FORECAST WITH OVERCAST AND RAINY SKIES KEEPING THE
OVERNIGHT LOWS UP A BIT, BUT LIKELY NOT NEARLY AS WARM AS THE TREND
IN THE GUIDANCE.  HAVE KNOCKED THEM DOWN A COUPLE DEGREES. SOUTHERLY
FLOW AND A RELATIVELY WARM AIRMASS KEEPING THE HIGHS A BIT ABOVE
NORMS, EVEN WITH THE PASSAGE OF THE FIRST LOW SKIRTING TO THE
NW...THE MID LEVELS REMAIN WARM UNTIL THE MAIN TROF OVER THE SW
LIFTS INTO AND OUT OF THE GREAT LAKES.  COOLER AIR IN THE MIDLEVELS
IS ONLY AROUND FOR 36 HOURS DAY 7/8 BEFORE THE WARM AIRMASS
REESTABLISHES ITSELF.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z TUESDAY NIGHT)
ISSUED AT 1144 PM CDT MON MAY 4 2015

FAIRLY SMALL AREA OF SHOWERS AND EMBEDDED THUNDERSTORMS IS STILL
MAKING ITS WAY ACROSS CENTRAL ILLINOIS, AND THIS AREA IS ONLY A
THREAT AT KBMI AND KCMI FOR A FEW MORE HOURS. MORE WIDESPREAD
SHOWERS/STORMS ARE UPSTREAM FROM THE CENTRAL ILLINOIS TERMINAL
AREA. RECENT SHORT RANGE/HIGH RESOLUTION MODEL GUIDANCE, SUPPORTED
BY RADAR LOOPS, SUGGESTS THAT MUCH OF THIS PRECIPITATION WILL PASS
TO THE NORTH OF THE LOCAL TERMINALS. KPIA AND KBMI STAND THE BEST
CHANCE OF BEING IMPACTED BY THIS UPSTREAM PRECIPITATION FOR
SEVERAL MORE HOURS, WHILE KSPI, KDEC, AND KCMI WILL BE MOSTLY DRY.
OUTSIDE OF ANY APPRECIABLE RAINFALL AREAS, WHICH WILL BRIEFLY
PRODUCE MVFR CONDITIONS, VFR CONDITIONS SHOULD PREVAIL. MOST OF
THE REST OF THE NIGHT SHOULD SEE VARIABLE WINDS WITH A NEARLY
STATIONARY BOUNDARY IN THE VICINITY. EXPECT WINDS TO TREND
SOUTHWESTERLY TUESDAY MORNING AS THE FRONT SHIFTS BACK NORTH.


&&

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

$$

SHORT TERM...ONTON
LONG TERM...HJS
AVIATION...BAK



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