Area Forecast Discussion
Issued by NWS Central Illinois

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000
FXUS63 KILX 162354
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
654 PM CDT THU APR 16 2015

.SHORT TERM...(THIS EVENING THROUGH FRIDAY)
ISSUED AT 310 PM CDT THU APR 16 2015

HIGH PRESSURE RIDGE SLIDING OFF TO THE EAST AS QUASI ZONAL
FLOW TRANSITIONING TO A SLIGHTLY SOUTHWESTERLY FLOW WITH A DEEP LOW
DIGGING IN AT H5 OVER THE DESERT SW. REMNANT MOISTURE AFFILIATED
WITH WAVE PULLING OFF TO THE EAST STILL IMPACTING THE EASTERN EDGES
OF THE STATE THIS AFTERNOON WITH A MORE PERSISTENT CLOUD COVER.
LIGHT AND VARIABLE WINDS TONIGHT WITH CLEARING SKIES JUST BEFORE
SUNSET SHOULD SET UP A GOOD ENVIRONMENT FOR SOME RADIATIONAL
COOLING.  WITH RELATIVELY HIGHER RH IN THE BOUNDARY LAYER TODAY NOT
GETTING MUCH OF A CHANCE FOR MIXING...HAVE PUT FOG IN FOR THE
OVERNIGHT IN THE EAST AND SOUTHEAST.  CONCERN THAT IT MAY BE MORE
WIDESPREAD THAN THE CURRENT PLACEMENT WITH THE DWPTS IN THE WEST
STILL NEAR 50.

.LONG TERM...(FRIDAY NIGHT THROUGH THURSDAY)
ISSUED AT 310 PM CDT THU APR 16 2015

FRIDAY WILL FEATURE UPPER LEVEL RIDGING AND WARMING ACROSS ILLINOIS,
AS A CUT-OFF LOW IN THE PLAINS SLOWLY DRIFTS FROM THE FOUR CORNERS
INTO COLORADO. HIGHS WILL REACH INTO THE UPPER 70S IN MANY AREAS
FRIDAY AFTERNOON, UNDER A LIGHT SOUTHEAST WIND.

RAIN AHEAD OF THE CUT-OFF LOW WILL ADVANCE EASTWARD ACROSS THE
PLAINS ON FRIDAY, EXPANDING ACROSS IOWA AND MISSOURI FRIDAY NIGHT
AND SATURDAY. CENTRAL ILLINOIS SHOULD REMAIN DRY THROUGH FRIDAY
NIGHT, WITH A FEW SHOWERS POSSIBLY AFFECTING AREAS SW OF SPI TO
EFFINGHAM ON SATURDAY. INCREASING CLOUDS ON SATURDAY WILL WORK TO
KEEP HIGHS A FEW DEGREES BELOW POTENTIAL HIGHS, BUT WE STILL EXPECT
MID 70S TO PREVAIL FOR HIGHS.

THE LOW WILL BECOME AN OPEN WAVE SATURDAY NIGHT, AS UPPER JET
SUPPORT DEVELOPS IN THE LEE OF THE TROUGH. THAT WILL WORK TO
INCREASE COVERAGE OF SHOWERS AND A FEW THUNDERSTORMS FROM SOUTHWEST
TO NORTHEAST ACROSS CENTRAL ILLINOIS SATURDAY NIGHT. AN INFLUX OF
GULF MOISTURE WILL INCREASE LOW LEVEL INSTABILITY THROUGH THE
WEEKEND. A BETTER CHANCE OF STRONG TO SEVERE STORMS LOOKS TO BE ON
SUNDAY WHEN A SURFACE LOW LIFTS NORTHEAST ACROSS ILLINOIS. THE
PASSAGE OF THE UPPER TROUGH AXIS SUNDAY NIGHT WILL CAUSE
THUNDERSTORM CHANCES TO LINGER AT LEAST THROUGH MIDNIGHT. SPC HAS
WESTERN IL IN THE DAY 4 15 PERCENT SEVERE OUTLOOK, WHICH INCLUDES
12Z SUNDAY TO 12Z MONDAY. WE KEPT LIKELY POPS ACROSS OUR AREA FROM
LATE SATURDAY NIGHT THROUGH SUNDAY NIGHT.

RAINFALL AND PERSISTENT CLOUD COVER SATURDAY NIGHT THROUGH SUNDAY
NIGHT WILL LIMIT DIURNAL TEMP SWINGS. LOWS SAT NIGHT WILL BE IN THE
MID TO UPPER 50S, WITH HIGHS NEAR 70 ON SUNDAY.

A MORE SIGNIFICANT AIRMASS CHANGE IS EXPECTED TO BEGIN SUNDAY NIGHT
BEHIND A DEPARTING SURFACE COLD FRONT. A LONG WAVE TROUGH ALOFT WILL
SETTLE INTO THE HEARTLAND, ALLOWING COOLER CANADIAN AIR TO SETTLE
INTO OUR AREA. LIGHT RAINFALL WILL LINGER ON MONDAY MORNING, MAINLY
EAST OF I-55, BUT CLOUDS SHOULD EVENTUALLY BEGIN TO CLEAR ACROSS
WESTERN IL MONDAY AFTERNOON.

AN EXTENDED PERIOD OF TEMPS AT OR BELOW NORMAL WILL CONTINUE FROM
MONDAY THROUGH AT LEAST WEDNESDAY, AS THE UPPER TROUGH STALLS OVER
THE GREAT LAKES AND NW FLOW DOMINATES ALOFT.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z FRIDAY EVENING)
ISSUED AT 654 PM CDT THU APR 16 2015

VFR CONDITIONS WITH LIGHT WINDS THIS EVENING AS A SURFACE HIGH
PRESSURE CENTER REMAINS NEAR THE NORTHEAST CORNER OF THE STATE.
SCATTERED CUMULUS CLOUD COVER AT 4-5 KFT WILL TEND TO DISSIPATE
OVERNIGHT WITH THE LOSS OF SURFACE HEATING. MODERATE AMOUNTS OF
LOW LEVEL MOISTURE WILL REMAIN GIVEN THE LIGHT FLOW OVER THE
REGION...AND WILL LIKELY RESULT IN SOME FOG FORMATION OVERNIGHT.
WITH HIGHER DEWPOINTS TOWARD SOUTHEAST IL...EXPECT FOG TO BE MORE
PREVALENT OVER KDEC-KBMI-KCMI EASTWARD...AND EXPECT AREAS OF IFR
OR WORSE VISIBILITY TO DEVELOP BY 08Z-11Z. WITH DAYTIME
HEATING...FOG SHOULD DISSIPATE 13Z-15Z WITH SCATTERED CUMULUS
DEVELOPMENT ABOVE MVFR THRESHOLD.

&&

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

$$

SHORT TERM...HJS
LONG TERM...SHIMON
AVIATION...ONTON


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