Area Forecast Discussion
Issued by NWS Central Illinois

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000
FXUS63 KILX 041955
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
255 PM CDT MON MAY 4 2015

.SHORT TERM...(TONIGHT)
ISSUED AT 245 PM CDT MON MAY 4 2015

FRONTAL BOUNDARY EXTENDING FROM SOUTHERN LAKE MICHIGAN TO NORTHERN
KANSAS WILL SINK SOUTHWARD...EVENTUALLY STALLING NEAR THE I-72
CORRIDOR LATER THIS EVENING.  SHOWERS AND THUNDERSTORMS WILL DEVELOP
ALONG THE BOUNDARY...WITH MOST MODEL SOLUTIONS SUGGESTING THE
GREATEST AREAL COVERAGE OF PRECIP ACROSS THE NORTHERN HALF OF THE
KILX CWA.  HRRR IS SHOWING WIDELY SCATTERED STORMS DEVELOPING OVER
THE NEXT COUPLE OF HOURS...WITH THE CONVECTION BECOMING MORE
WIDESPREAD AFTER SUNSET AS A WEAK LOW-LEVEL JET DEVELOPS.  HAVE
ADJUSTED RAIN CHANCES ACCORDINGLY...WITH LIKELY POPS ALONG/NORTH OF
I-72 TAPERING DOWN TO JUST SLIGHT CHANCE ALONG/SOUTH OF I-70.

&&

.LONG TERM...(TUESDAY THROUGH MONDAY)
ISSUED AT 245 PM CDT MON MAY 4 2015

AN UPPER LEVEL RIDGE IS EXPECTED TO AMPLIFY OVER THE CENTER OF THE
NATION STARTING ON TUESDAY WHICH SHOULD PUSH THE BETTER CHANCES FOR
SHOWERS AND THUNDERSTORMS NORTH OF THE FORECAST AREA...AT LEAST INTO
THURSDAY. SHORTWAVE ENERGY IS THEN FORECAST TO EJECTS NORTH OUT OF
THE SOUTHERN PLAINS AND BRING ABOUT A CHANCE FOR MORE SHOWERS AND
THUNDERSTORMS...ESPECIALLY ACROSS OUR WEST...THURSDAY NIGHT INTO
FRIDAY. A MORE POTENT 500 MB TROF IS THEN FORECAST TO SLOWLY TRACK
OUT OF THE ROCKIES DURING THE WEEKEND BRINGING PERIODS OF SHOWERS
AND THUNDERSTORMS TO THE FORECAST AREA. MOST MODELS TRACK THIS LOW
NORTH-NORTHEAST ON SUNDAY SUGGESTING THE MORE SIGNIFICANT LIFT TO
REMAIN WEST OF OUR AREA UNTIL LATE SUNDAY OR MONDAY OF NEXT WEEK
WHEN THE SYSTEM WILL SWING A COLD FRONT THROUGH CENTRAL ILLINOIS.
UNTIL THEN...WARM TEMPERATURES TO PREVAIL WITH THE SHOWER AND STORM
CHANCES ACROSS THE FAR NORTH TOMORROW AS THE FRONT RETREATS BACK
TO THE NORTH...AND THEN RAIN CHANCES RETURN LATE THU INTO FRIDAY
AND HOLDS THROUGH EARLY NEXT WEEK BEFORE WE FINALLY GET A CHANGE
IN AIR MASS.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z TUESDAY AFTERNOON)
ISSUED AT 1258 PM CDT MON MAY 4 2015

MODELS CONTINUE TO SHOW FRONTAL BOUNDARY CURRENTLY ACROSS NORTHERN
ILLINOIS DROPPING SLOWLY SOUTHWARD INTO THE AREA TONIGHT. SHOWERS
AND THUNDERSTORMS WILL DEVELOP ALONG/NEAR THIS BOUNDARY AFTER
01/02Z...WITH THE LONGEST PERIOD OF RAIN EXPECTED AT THE NORTHERN
TERMINALS OF KPIA AND KBMI. WILL CARRY PREDOMINANT SHOWERS AT
THESE SITES THROUGHOUT THE NIGHT. BIG QUESTION WILL BE WHETHER OR
NOT CEILINGS WILL LOWER INTO THE MVFR CATEGORY NORTH OF THE FRONT.
NAM FORECAST SOUNDINGS CONTINUE TO SHOW VFR CEILINGS EVEN AT
KPIA/KBMI WHERE WINDS BECOME E/NE LATER THIS EVENING, WHILE THE
HRRR HINTS AT LOWER CEILINGS AROUND 2500FT. LATEST REGIONAL OBS
SHOW A FEW MVFR CEILINGS NORTH OF THE FRONT ACROSS CENTRAL IOWA,
SO DO NOT WANT TO COMPLETELY IGNORE THE POSSIBILITY. HAVE
THEREFORE INCLUDED SCT025 AT BOTH KPIA AND KBMI AFTER 04Z AND WILL
CONTINUE TO MONITOR LATER OBS AND MODEL RUNS TO MAKE A FINAL
DETERMINATION. ALL MODELS SHOW THE BOUNDARY SHIFTING BACK
NORTHWARD TUESDAY MORNING, RESULTING IN DIMINISHING RAIN CHANCES
AND WINDS RETURNING TO THE S/SE.


&&

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

$$

SHORT TERM...BARNES
LONG TERM...SMITH
AVIATION...BARNES


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