Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 031743
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1243 PM CDT MON AUG 3 2015

.UPDATE...
ISSUED AT 1047 AM CDT MON AUG 3 2015

15Z/10AM SURFACE ANALYSIS SHOWS COLD FRONT SETTLING SOUTHWARD
THROUGH CENTRAL ILLINOIS. TO THE NORTH OF THE FRONT...A SLIGHTLY
COOLER AND LESS HUMID AIRMASS IS TRICKLING SOUTHWARD ACROSS IOWA
AND NORTHERN ILLINOIS WHERE DEWPOINTS HAVE DROPPED INTO THE 50S.
FURTHER SOUTH...A WARM/HUMID AIRMASS REMAINS IN PLACE WITH
DEWPOINTS POOLING IN THE UPPER 60S TO AROUND 70 ALONG THE
BOUNDARY. AS THE FRONT SAGS FURTHER SOUTHWARD...BOTH THE NAM AND
RAPID REFRESH SHOW ISOLATED CONVECTION DEVELOPING SOUTH OF THE
I-70 CORRIDOR LATE THIS AFTERNOON INTO THE EVENING. CURRENT
FORECAST HANDLES THIS WELL...SO NO MAJOR UPDATES ARE NEEDED AT
THIS TIME.

&&

.SHORT TERM...(TODAY)
ISSUED AT 336 AM CDT MON AUG 3 2015

COLD FRONT...CURRENTLY LOCATED JUST WEST OF I-55...WILL CONTINUE TO
SLOWLY PUSH SOUTH THROUGH CENTRAL ILLINOIS TODAY. BY 18Z THE FRONT
SHOULD BE IN SOUTHEASTERN ILLINOIS SO DURING PEAK HEATING THIS
AFTERNOON...ISOLATED STORMS ARE POSSIBLE. OTHER THAN THE SOUTHEAST
PART OF THE CWA...DRY WEATHER AND MOSTLY SUNNY SKIES IS EXPECTED
ACROSS THE AREA TODAY THROUGH THIS AFTERNOON. WINDS WILL BECOME
NORTHWESTERLY BEHIND THE FRONT...WHICH WILL BRING IN LOWER
DEWPOINTS AND COOLER AIR. AFTERNOON HIGH TEMPS WILL BE IN THE LOW
TO MID 80S NORTH OF THE FRONT...TO THE UPPER 80S TO AROUND 90
SOUTH OF THE FRONT. GUIDANCE NUMBERS LOOK SIMILAR AND CLOSE TO
CURRENT THINKING.

.LONG TERM...(TONIGHT THROUGH SUNDAY)
ISSUED AT 336 AM CDT MON AUG 3 2015

ISOLATED SHOWER OR THUNDERSTORM IN FAR SOUTHEAST IL EARLY THIS
EVENING SOUTH OF HIGHWAY 50 WITH FRONTAL BOUNDARY SAGGING SOUTHWARD
INTO CENTRAL PARTS OF KY/MO THIS EVENING. THEN SLIGHT CHANCES OF
CONVECTION RETURN TO FAR SW CWA LATER TONIGHT INTO TUE AHEAD OF
SHORT WAVES EJECTING INTO THE CENTRAL PLAINS. NEARBY WEAK HIGH
PRESSURE OVER NORTHERN WI AND MI OVERNIGHT INTO TUE SHOULD KEEP MOST
OF CENTRAL IL DRY TONIGHT INTO TUE. COOLER LOWS TONIGHT IN THE LOW
TO MID 60S WITH MILDEST READINGS SW CWA WHERE MORE CLOUDS EXPECTED.
HIGHS TUE IN THE LOW TO MID 80S WITH WARMEST READINGS SW CWA.
DEWPOINTS IN THE LOW TO MID 60S TUE AND HIGHEST IN SW CWA.

00Z MODELS CONTINUE TO SHOW INCREASING CHANCES OF SHOWERS AND
THUNDERSTORMS TUE NIGHT THROUGH THU AS STORM SYSTEM EJECTS EAST
ACROSS THE MID MS RIVER VALLEY WITH SLOWLY DEEPENING SURFACE LOW
PRESSURE WHICH TRACKS ACROSS SE IL THU MORNING. THE NAM AND GEM
MODELS ARE FURTHER NORTH WITH LOW PRESSURE AND QPF FIELDS WHILE
ECMWF AND GFS MODELS ARE FARTHER SOUTH. WILL BLEND BETWEEN THESE
SOLUTIONS AND INCREASED RAIN CHANCES AND QPF ESPECIALLY OVER
SOUTHERN AREAS. MAIN CHANCES OF CONVECTION TUE NIGHT IS SOUTH OF I-
74. SPC HAS MARGINAL RISK OF SEVERE STORMS SW OF A JACKSONVILLE TO
ROBINSON LINE TUE NIGHT. HAVE HIGHER POPS SPREADING ACROSS CWA
WED/WED NIGHT AND THEN DIMINISHING POPS FROM NW TO SE BY THU
AFTERNOON/EVENING. COOLER HIGHS IN UPPER 70S/LOWER 80S WED/THU DUE
TO MORE CLOUDS AND RAIN AROUND AND COULD BE EVEN COOLER HIGHS IN MID
70S OVER PARTS OF EAST CENTRAL IL THU DEPENDING ON SURFACE LOW
PRESSURE TRACK.

UPPER LEVEL RIDGE WILL BE OVER THE WESTERN STATES AND UPPER LEVEL
TROF OVER NE STATES INTO EASTERN CANADA LATE THIS WEEK AND WILL GIVE
A BIT BELOW NORMAL TEMPERATURES OVER CENTRAL/SE IL INTO THIS
WEEKEND. A DRIER PERIOD EXPECTED FRI/SAT WITH INCREASING POPS OVER
CENTRAL IL SUNDAY ESPECIALLY OVER THE IL RIVER VALLEY AND ACROSS
AREAS SUNDAY NIGHT WITH NEXT SHORT WAVE RIDING OVER TOP OF UPPER
LEVEL RIDGE TOWARD THE AREA.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z TUESDAY AFTERNOON)
ISSUED AT 1242 PM CDT MON AUG 3 2015

VFR CONDITIONS WILL PREVAIL THROUGH THE ENTIRE 18Z TAF PERIOD. A
COLD FRONT WILL DROP SOUTH OF THE TERMINALS THIS AFTERNOON...THEN
WILL BECOME NEARLY STATIONARY ACROSS SOUTHERN ILLINOIS TONIGHT
INTO TUESDAY. W/NW WINDS OF 8 TO 12KT THIS AFTERNOON WILL BECOME
LIGHT/VARIABLE TONIGHT AS HIGH PRESSURE BUILDS INTO THE REGION.
WHILE THE FRONT WILL REMAIN WELL TO THE SOUTH...MOST MODELS ARE
SUGGESTING SCATTERED SHOWERS/THUNDER WILL DEVELOP NEAR THE
BOUNDARY LATE TONIGHT. THINK PRECIP WILL STAY S/SW OF THE TAF
SITES...BUT HAVE INCLUDED A MID-LEVEL CLOUD DECK AT KSPI AFTER 09Z
ACCORDINGLY.


&&

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

$$

UPDATE...BARNES
SHORT TERM...AUTEN
LONG TERM...07
AVIATION...BARNES


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