Area Forecast Discussion
Issued by NWS Central Illinois

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000
FXUS63 KILX 260825
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
325 AM CDT WED AUG 26 2015

.SHORT TERM...(TODAY)
ISSUED AT 324 AM CDT WED AUG 26 2015

DEEP UPPER LOW NORTH OF LAKE ERIE EARLY THIS MORNING CONTINUES TO
SLOWLY EDGE AWAY FROM THE MIDWEST. HOWEVER, SEVERAL WEAK SHORTWAVES
CONTINUE TO ROTATE SOUTHWARD AROUND THE WESTERN PERIPHERY OF THE
UPPER LOW ACROSS THE LOWER GREAT LAKES BRINGING CLOUD COVER MUCH
FURTHER INTO OUR FORECAST AREA THAN WHAT GUIDANCE SUGGESTED. THAT
WILL BE THE MAIN FORECAST CONCERN TODAY, AMOUNT OF CLOUD COVER OVER
CENTRAL IL AND ITS AFFECT ON TEMPERATURES. RAP FORECAST SOUNDINGS
AND TIME HEIGHT CROSS SECTIONS SHOWING QUITE A BIT OF MOISTURE AT OR
JUST BELOW 850 MB INTO EARLY THIS AFTERNOON, ESPECIALLY OVER THE
EASTERN HALF OF THE FORECAST AREA. WILL HIT THE CLOUD COVER A BIT
HEAVIER ACROSS THE EAST TODAY WITH TEMPS CUT BACK A FEW DEGREES AS A
RESULT, MAINLY IN THE MID 70S, WHILE FURTHER WEST, A BIT MORE SUN
SHOULD ALLOW AFTERNOON TEMPERATURES TO RISE INTO THE UPPER 70S.
SOUNDINGS INDICATE SOME GUSTS UP TO 20 MPH POSSIBLE AGAIN FROM THE
NORTHWEST LATER THIS MORNING INTO THE AFTERNOON HOURS, ESPECIALLY
ACROSS THE WEST WHERE THERE WILL BE DEEPER MIXING OCCURRING.

&&

.LONG TERM...(TONIGHT THROUGH TUESDAY)
ISSUED AT 324 AM CDT WED AUG 26 2015

SLIGHTLY COOLER THAN CLIMATOLOGICAL NORMS THROUGH THE END OF THE
WEEK, ALBEIT IN A SLIGHT WARMING TREND. FORECAST ISSUE IN THE
LONGER TERM REMAINS THE SYSTEM FOR THE BEGINNING OF THE WEEKEND. A
SHORT WAVE DIVES INTO THE MIDWEST RIPPLING THROUGH THE
PREDOMINANTLY NWRLY FLOW. MODELS HAVE BEEN INCONSISTENT WITH THE
TIMING AND THE SPEED OF THE SYSTEM ITSELF WITH ITS OWN FORWARD
MOTION. WAVE REACHES THE MIDWEST AND SLOWS CONSIDERABLY. EITHER
WAY, SOME CONSENSUS APPEARS AS TO ONSET OF PRECIP IN CENTRAL
ILLINOIS AFTER 00Z SATURDAY BTWN THE GFS/ECMWF/NAM. HOWEVER, AT
THIS POINT, THE PRECIP STARTS TO BECOME LESS IN COVERAGE. EXPECTED
THROUGH THE OVERNIGHT FRI NIGHT PERHAPS WITH THE LOSS OF A DIURNAL
COMPONENT, BUT LESS EXPECTED DURING THE DAY ON TUESDAY. THAT BEING
SAID, THE SOUNDINGS ARE NOT REPRESENTATIVE FOR RAIN, DRYING OUT
CONSIDERABLY WHILE THE MODELS ARE GENERATING QPF. A RATHER DRY
AIRMASS FOR DAYS...THE MODELS SEEM TO BE OVERDOING THE BOUNDARY
LAYER AVAILABLE MOISTURE. OVERBLOWN RH IN THE LOW LEVELS IN THE
NAM IS EXPECTED AND SO FAR, IT IS TRUE TO FORM IN PRODUCING
SIGNIFICANTLY MORE QPF. THE TREND, THOUGH, IS MORE TO A POTENTIAL
SHOWERY SITUATION. HAVE EASED BACK POPS WHERE COLLABORATIVELY
POSSIBLE, AND SWITCHED THE WORDING TO COVERAGE INSTEAD OF
PROBABILITY.

BEYOND THE POPS ON THE WEEKEND, THE FLOW SWITCHES TO A LESS
AMPLIFIED PATTERN.  THE WEAK SOUTHWESTERLY FLOW ALLOWS THE HEAT OVER
THE DESERT SW TO ESCAPE OUT FROM UNDER THE PERSISTENT RIDGE AND
BRING A WARMING TREND FOR THE FIRST COUPLE DAYS OF NEXT WEEK.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z WEDNESDAY NIGHT)
ISSUED AT 1142 PM CDT TUE AUG 25 2015

QUIET/VFR AVIATION WEATHER CONDITIONS EXPECTED ACROSS THE CENTRAL
ILLINOIS TERMINALS THROUGH THE 06Z TAF VALID TIME. A RIDGE OF
HIGH PRESSURE WILL SLOWLY BUILD INTO THE AREA DURING THE PERIOD
HELPING WINDS TO REMAIN LIGHT. CLOUD COVER SHOULD BE MINIMAL
OVERALL, BUT A PERIOD OF BROKEN VFR CIGS IS POSSIBLE FOR A FEW
MORE HOURS KPIA, KBMI, KDEC & KCMI AS AN UPPER LEVEL DISTURBANCE
DIVES SOUTHEAST FROM THE GREAT LAKES.


&&

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

$$

SHORT TERM...SMITH
LONG TERM...HJS
AVIATION...BAK


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