Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 031745
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1245 PM CDT WED JUN 3 2015

.UPDATE...
ISSUED AT 1027 AM CDT WED JUN 3 2015
HIGH PRESSURE RIDGE JUST OFF TO THE EAST THIS MORNING, BUT CLEAR
SKIES LOSING GROUND TO SOUTHERLY WINDS PUSHING MORE LLVL MOISTURE
INTO THE REGION. CU FIELD DEVELOPED EARLY AND RATHER DENSE ON SAT
IMAGERY. INCREASED THE CLOUD COVER IN THE FORECAST AND ADJUSTED
THE HIGHS DOWN A DEGREE OR SO. CONVECTION OFF TO THE WEST,
HOWEVER, SHOULD CONTINUE TO ERODE AS IT PUSHES EASTWARD INTO THE
MISS RIVER VALLEY/THE SFC RIDGE. HRRR REMAINS LARGELY DRY ON THE
WESTERN BORDER OF THE STATE THROUGH 00Z.

&&

.SHORT TERM...(TODAY)
ISSUED AT 258 AM CDT WED JUN 3 2015

INITIAL CONCERNS ARE ON FOG FORMATION IN SOUTHEAST COUNTIES. THE
SURFACE RIDGE AXIS HAS SHIFTED SLIGHTLY TO THE SOUTHEAST FROM
YESTERDAY, AND NOW SITS EXTENDS ACROSS IL JUST SOUTHEAST OF OUR
FORECAST AREA. SOUTHEAST WINDS ARE BEGINNING TO DEVELOP IN THE WAKE
OF THE RIDGE AXIS, WHICH MAY WORK TO PULL THE MOISTURE LADEN AIR IN
SE IL TOWARD CENTRAL IL. HRRR GUIDANCE HAS CONTINUED TO INDICATE
SOME LOCALLY DENSE FOG MAY FORM FROM IN AREAS FROM LAWRENCEVILLE TO
LINCOLN. SURFACE OBS ARE SHOWING LIGHT FOG ALREADY FORMING IN THE
SOUTHERN PORTION OF THAT AREA, AND DEWPOINT DEPRESSIONS ARE 2-
3F...SO SOME CONFIDENCE IS BUILDING TOWARD EXPANDING OF FOG COVERAGE
AND DENSITY. WILL KEEP AREAS OF FOG IN THE GRIDS SOUTHEAST OF
LINCOLN THROUGH 13Z/8AM. NOT AS CONFIDENT ON ANY DENSE FOG FORMING,
BUT SOME VISIBILITY RESTRICTION FOR TRAVEL IS EXPECTED EARLY THIS
MORNING IN THE SOUTHEAST.

THE REST OF THE DAY WILL FOCUS ON AN MCS IN THE PLAINS ROLLING OVER
THE UPPER RIDGE TOWARD EASTERN MISSOURI. WE WILL SEE INCREASING
CIRRUS CLOUDS AS THE STORM COMPLEX REACHES NORTH CENTRAL MISSOURI BY
18Z, THEN DISSIPATES BY 21Z AS IT REACHES EASTERN MISSOURI. WE WILL
NOT SEE ANY RAIN OR STORMS IN ILLINOIS, JUST SOME INCREASE IN HIGH
CLOUDS. FILTERED SUNSHINE TODAY ALONG WITH A RISE OF 2-4C IN 850MB
TEMPS IN THE LAST 24 HOURS WILL HELP HIGH TEMPS CLIMB INTO THE UPPER
70S TO AROUND 80. THE WARMER HIGH TEMPS WILL BE LOCATED IN OUR SW
COUNTIES, WEST OF LINCOLN TO SPRINGFIELD, WHERE SOUTHWEST FLOW AND
WARMING WILL INCREASE THE SOONEST.

.LONG TERM...(TONIGHT THROUGH TUESDAY)
ISSUED AT 258 AM CDT WED JUN 3 2015

WARMTH AND HUMIDITY WILL BUILD EARLY IN THE PERIOD, ALTHOUGH NOT TO
SIGNIFICANTLY ABOVE NORMAL LEVELS, AND LIKELY LINGER INTO AT LEAST
THE MIDDLE OF NEXT WEEK. DRY WEATHER WILL ATTEMPT TO HOLD ON INTO
THURSDAY WITH UPSTREAM RIDGING HOLDING FAIRLY STRONG, BUT GRADUAL
WEAKENING OF THE RIDGE WILL ALLOW PERIODIC STORM COMPLEXES TO DRAW
CLOSER BEFORE DISSIPATING.

BY LATER THURSDAY NIGHT INTO FRIDAY A STRONGER WAVE WILL TOP THE
WEAKENING UPSTREAM RIDGE, PROVIDING THE BEST RAIN CHANCES OF THE
WEEK. THE ARRIVAL OF THIS WAVE WILL ALSO SIGNAL THE START OF A MORE
ACTIVE WEATHER PERIOD, WITH PERIODIC SHOWERS/STORMS WELL INTO NEXT
WEEK AS THE UPPER FLOW TRANSITIONS TO AT LEAST WEAKLY CYCLONIC.
WHILE IT WILL CERTAINLY NOT BE RAINING ALL THE TIME DURING THE
EXTENDED RANGE OF THE FORECAST, IT IS PRETTY TOUGH TO PIN-POINT
PERIODS COMPLETELY FREE FROM PRECIPITATION RISK. THIS IS RESULTING
IN AN PROLONGED PERIOD OF CHANCE POPS. THIS SHOULD BE ABLE TO FINE
TUNED IN LATER FORECASTS AS MODEL DISAGREEMENT IN THE EXPLICIT
TIMING/TRACK OF DISCRETE SHORT WAVES DIMINISHES.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z THURSDAY AFTERNOON)
ISSUED AT 1239 PM CDT WED JUN 3 2015
LOW LEVEL MOISTURE ENHANCED BY SOUTHERLY FLOW PROVIDING JUST
ENOUGH FOR A BKN CU FIELD...BUT THE CIRRUS STARTING TO BLOCK SOME
OF THE HEATING IN THE WEST...CONCENTRATING THE CU IN THE EASTERN
HALF OF THE STATE. CLEARING OF THE CU EXPECTED TOWARDS THE END OF
THE DAY, AND SCT/BKN CIRRUS TO CONTINUE. WITH THE EXTENT OF THE
CLOUD COVER OVER CENTRAL ILLINOIS, MIXING OUT THE BOUNDARY LAYER
MOISTURE WILL BE LIMITED. AS A RESULT, HAVE ADDED A TEMPO FOR
REDUCED VIS FOR THE MORNING HOURS.

&&

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

$$

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


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