Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 291755
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1255 PM CDT FRI MAY 29 2015

.UPDATE...
ISSUED AT 1036 AM CDT FRI MAY 29 2015

15Z/10AM SURFACE ANALYSIS SHOWS FRONTAL BOUNDARY WELL TO THE NORTH
ALONG THE WISCONSIN/ILLINOIS BORDER...WITH WARM/HUMID AIRMASS IN
PLACE FURTHER SOUTH ACROSS ALL OF CENTRAL AND SOUTHEAST ILLINOIS.
DESPITE INCREASED DEEP-LAYER MOISTURE AND SURFACE DEWPOINTS IN THE
MIDDLE TO UPPER 60S, LACK OF STRONG SYNOPTIC FORCING IS PREVENTING
WIDESPREAD CONVECTION. LATEST RADAR SHOWS ONLY ISOLATED
SHOWERS...MAINLY WEST OF THE I-57 CORRIDOR. WATER VAPOR IMAGERY
INDICATES SEVERAL WEAK WAVES EMBEDDED WITHIN THE BROAD
SOUTHWESTERLY FLOW PATTERN ACROSS THE PLAINS/MIDWEST, WITH THE
MOST SIGNIFICANT FEATURE WELL TO THE SOUTHWEST OVER TEXAS. A
WEAKER WAVE IS RIPPLING NORTHWARD ACROSS SOUTHWEST
MISSOURI/NORTHWEST ARKANSAS AND WILL APPROACH ILLINOIS LATE IN THE
DAY. AS STRONGER FORCING GRADUALLY ARRIVES, SHOWERS AND
THUNDERSTORMS WILL BECOME MORE WIDESPREAD FROM MID-AFTERNOON INTO
THE EVENING HOURS. AMPLE CLOUD COVER AHEAD OF THE WAVE MAY INHIBIT
INSTABILITY, SO AREAL COVERAGE OF PRECIP IS STILL IN QUESTION. AS
A RESULT, OPTED TO ADJUST POPS DOWN SLIGHTLY TO GO WITH SCATTERED
WORDING TODAY. RAIN CHANCES WILL INCREASE LATER TONIGHT INTO
SATURDAY AS A COLD FRONT CURRENTLY DROPPING THROUGH THE NORTHERN
PLAINS ARRIVES.

&&

.SHORT TERM...(TODAY)
ISSUED AT 332 AM CDT FRI MAY 29 2015

07Z/2AM SURFACE ANALYSIS SHOWS THE WARM FRONT HAS PROGRESSED NORTH
OF OUR COUNTIES INTO NORTHERN IL, WITH DEWPOINTS CLIMBING FIRMLY
INTO THE LOW TO MID 60S IN ITS WAKE CREATING MUGGY CONDITIONS FOR
EARLY MORNING. RADAR IMAGES INDICATE RAIN SHOWERS FOCUSED NW OF THE
IL RIVER AND INTO EASTERN IOWA, WITH A FEW SHOWERS TO OUR SW IN
EASTERN MISSOURI NEAR ST LOUIS.

THE RAPID REFRESH AND HRRR BOTH SHOW SHOWERS AND STORMS DEVELOPING
ACROSS CENTRAL IL THIS MORNING. WATER VAPOR IMAGERY SHOWS AN
ELONGATED AREA OF ROTATIONAL ENERGY IN THE CENTRAL PLAINS, WITH
SHORTWAVES EVIDENT IN NEBRASKA, MISSOURI, KANSAS, AND OK/TX. THE
MISSOURI WAVE WILL PROVIDE ENHANCED LIFT THIS MORNING, WHICH WILL
PUT MOST OF OUR COUNTIES UNDER THE THREAT OF RAIN. WE WENT WITH HIGH
CHANCE POPS PRIMARILY, WITH A SMALL AREA OF LIKELY CLOSER TO THE
CENTER OF THE WAVE IN OUR N COUNTIES. THE KANSAS WAVE WILL FOLLOW
IMMEDIATELY ON THE HEELS OF THE FIRST WAVE TRIGGERING ADDITIONAL
STORMS BY LATE AFTERNOON, PROMPTING LIKELY POPS WEST OF I-55.

HIGH TEMPS TODAY WILL BE TEMPERED SOMEWHAT BY PERIODIC CLOUD COVER
AND SHOWERS/STORMS. HOWEVER, WE EXPECT ENOUGH FILTERED SUNSHINE TO
PUSH HIGHS INTO THE 80 TO 85 DEGREE RANGE THIS AFTERNOON. WINDS WILL
BE SOUTHERLY THROUGH THE DAY AS CENTRAL ILLINOIS REMAINS IN THE WARM
SECTOR. A FEW GUSTS MAY APPROACH 20 MPH BY AFTERNOON.

.LONG TERM...(TONIGHT THROUGH THURSDAY)
ISSUED AT 332 AM CDT FRI MAY 29 2015

PREVIOUSLY, MODELS WERE PRETTY SUCCINCT WITH THE PASSAGE OF THE
COLD FRONT EDGING TOWARDS THE MIDWEST OVERNIGHT TONIGHT/TOMORROW.
AND CURRENTLY, THE NAM, GFS, AND ECMWF ARE ALL PROFUSE WITH THE QPF
ACROSS THE BOARD.  HOWEVER, THE LATEST RUNS OF THE 4 KM WRF
INITIALIZED WELL, PICKING UP ON THE SHOWERS TO THE NW AND SO FAR, IS
RIGHT ON TRACK. OF COURSE, THE 4 KM WRF TAKES THE IMPULSE THAT IS
CURRENTLY TO THE SW AND DRAGS IT UP AND ALONG THE FRONT, KEEPING ALL
OF THE PRECIP TO THE NW BEFORE TOMORROW MORNING.  THE OTHER MODELS
ARE A LITTLE SLOWER WITH THE SOUTHERN MOST SHORTWAVE, AND
CONSIDERING THE LACK OF RAPID FLOW, AND THE UNSTABLE AIRMASS (PW
VALUES FROM 1.5-2 BEFORE 12Z) IN THE REGION...AM KEEPING TO A WETTER
FORECAST OVERNIGHT. WILL NOT TAKE MUCH IN THE WAY OF CONVERGENCE,
EITHER FROM THE FRONT ITSELF OR FROM OUTFLOW FROM ONGOING
CONVECTION.

PRECIP LIKELY TOMORROW AS WELL AS THE FRONT MAKES ITS WAY THROUGH
THE REGION. FRONT SLOWING A BIT WITH THE CONVECTION TOMORROW AND
TOMORROW NIGHT...MAKING IT INTO THE OHIO RIVER VALLEY AND STALLING
IN PARALLEL FLOW SOMEWHAT.  LINGERING POPS IN THE SE START TO
LESSEN, BUT WILL BE HIGHLY DEPENDENT ON THE LOCATION OF THE REMNANT
FRONT.  COOLER AIR MOVING IN BEHIND THE BOUNDARY, AND THE WEEKEND
WRAPS UP UNSEASONABLY COOL FOR SUNDAY THROUGH TUESDAY WITH TEMPS IN
THE 60S AND 70S.  SUN NIGHT THROUGH WED NIGHT SHOULD SEE LITTLE
CHANCE FOR RAIN  AND THE MODELS ARE FINALLY STARTING TO RETURN A
DRIER SOLUTION.  HOWEVER, TOWARDS THE END OF THE FORECAST
PD...SOUTHERLY FLOW KICKS BACK IN AND THE LACK OF FLOW ALOFT SETS UP
ANOTHER SUMMERY AFTERNOON SHOWER/THUNDERSTORM PATTERN FOR THE LATTER
HALF OF NEXT WEEK.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SATURDAY AFTERNOON)
ISSUED AT 1255 PM CDT FRI MAY 29 2015

SHOWERS AND THUNDERSTORMS WILL DEVELOP ACROSS CENTRAL ILLINOIS
THIS AFTERNOON IN AN INCREASINGLY UNSTABLE AIRMASS...HOWEVER WITH
NO SIGNIFICANT FORCING IN PLACE...THINK AREAL COVERAGE WILL
REMAIN SCATTERED. A SHORT-WAVE TROUGH CURRENTLY EVIDENT ON WATER
VAPOR IMAGERY OVER OKLAHOMA/TEXAS WILL LIFT NORTHEASTWARD INTO
ILLINOIS TONIGHT...BRINGING ENHANCED FORCING AND A GREATER AREAL
COVERAGE OF PRECIP. BASED ON RAPID REFRESH FORECAST...HAVE
INTRODUCED PREDOMINANT RAIN WITH VCTS AT KPIA AND KSPI BY
03Z...THEN FURTHER EAST TO KCMI BY 08Z. WILL GIVE EACH TAF SITE A
10-HOUR PERIOD OF SHOWERS...FOLLOWED BY VCSH BY SATURDAY MORNING
AS THE WAVE TRACKS NORTH OF THE AREA. FORECAST SOUNDINGS INDICATE
LOW VFR CEILINGS INITIALLY...LOWERING TO MVFR SATURDAY MORNING
IMMEDIATELY AHEAD/ALONG AN APPROACHING COLD FRONT. WINDS WILL BE
SOUTHWESTERLY THROUGH THE ENTIRE 18Z TAF PERIOD...THEN WILL BECOME
W/NW BEHIND THE FRONT BY SATURDAY AFTERNOON.

&&

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

$$

UPDATE...BARNES
SHORT TERM...SHIMON
LONG TERM...HJS
AVIATION...BARNES


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