National Weather Service Weather Forecast Office

• Home
• Site Map
• News
• Organization
• Search for: NWS All NOAA 

000
FXUS63 KILX 161155
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
655 AM CDT THU MAY 16 2013

.DISCUSSION...
ISSUED 319 AM CDT THU MAY 16 2013

SHORT TERM...TODAY THROUGH FRIDAY

QUASI-STATIONARY FRONT LIES WEST-EAST ACROSS CENTRAL IL EARLY
THIS MORNING BUT HAS BECOME ILL DEFINED DUE TO CONVECTION AND
RESULTING OUTFLOW BOUNDARIES. BEST COVERAGE OF THUNDERSTORMS FOR
PAST FEW HOURS HAS OCCURRED OVER THE NORTHERN THIRD OF THE CWA
WHERE A 30 KT WSW LOW LEVEL JET HAS PROVIDED ENHANCED CONVERGENCE
INTO THE LOW AND MID LEVEL BOUNDARIES. THIS ACTIVITY WILL CONTINUE
TO FADE TOWARDS SUNRISE AS THE LLJ WEAKENS. MAIN FORECAST
CHALLENGE TODAY WILL BE COVERAGE AND TIMING OF TSTMS WITH BOUNDARY
REMAINING IN THE AREA...AND A CLOSED UPPER LOW CURRENTLY OVER
OKLAHOMA WHICH WILL BE OPENING UP AND LIFTING NORTHEAST. MOISTURE
LEVELS INCREASE AHEAD OF THIS FEATURE SO EXPECT BETTER STORM
COVERAGE THAN YESTERDAY ESPECIALLY DURING PEAK AFTERNOON
INSTABILITY. LATEST HI-RES SHORT RANGE MODELS FOCUS THIS ACTIVITY
OVER THE CENTRAL AND SOUTHERN CWA AND HAVE PLACED HIGHEST CHANCE
POPS HERE.  FORECAST SOUNDINGS SHOW ENOUGH MID LEVEL COOLING TO
ERODE CAPPING...AND AFTERNOON/EARLY EVENING CAPES ON THE ORDER OF
1K J/KG. WINDS ALOFT ARE QUITE LIGHT NEAR 10 KTS SO STORMS WILL BE
SLOW MOVERS AND CAPABLE OF HEAVY RAIN RATES AS PRECIPITABLE WATER
RISES TO AROUND 1.25 INCHES. STORMS SHOULD DISSIPATE DURING THE
EVENING WITH LOSS OF DAYTIME HEATING AND NO LLJ SUPPORT.

THE BOUNDARY LIFTS NORTH OF THE CWA ON FRIDAY...BUT
MORE SCATTERED AFTERNOON CONVECTION EXPECTED AS THE UPPER TROF
SHIFTS ACROSS THE AREA. TEMPS WILL REMAIN SEVERAL DEGREES ABOVE
NORMAL FOR THE NEXT COUPLE DAYS WITH HIGHS IN THE LOWER 80S AND
LOWS IN THE LOWER 60S.

LONG TERM...SATURDAY THROUGH WEDNESDAY

LINGERING EFFECTS OF THE UPPER TROF COULD BRING SCATTERED
CONVECTION BACK TO PRIMARILY THE EASTERN CWA SATURDAY
AFTERNOON...CLOSER TO THE DEPARTING TROF. BY LATE SATURDAY INTO
SUNDAY UPPER RIDGING WILL BUILD ACROSS THE MISSISSIPPI VALLEY IN
RESPONSE TO THE NEXT SYSTEM DEVELOPING OVER THE ROCKIES. THIS
PROVIDES THE BEST SHOT AT A DRY PERIOD IN THE FORECAST AND HAVE
REMOVED ANY MENTIONABLE POPS SATURDAY NIGHT THROUGH SUNDAY
AFTERNOON. SUNDAY HAS THE POTENTIAL TO BE THE WARMEST OF THE NEXT
7 DAYS AS 850MB TEMPS WARM INTO THE UPPER TEENS AND AMPLE
SUNSHINE. HAVE BOOSTED HIGHS IN TO THE MID 80S.

A DEEP UPPER LOW IS FORECAST TO CLOSE OFF OVER THE NORTHERN PLAINS
BY THE END OF THE WEEKEND...AND SLOWLY MOVE TOWARDS THE WESTERN
GREAT LAKES BY WEDNESDAY ACCORDING TO THE GFS...OR OVER THE CWA
ACCORDING TO THE 00Z ECMWF. IN EITHER CASE THIS SETS UP A
PROLONGED PERIOD OF DIFFLUENT SOUTHWEST MID LEVEL OVER THE MIDWEST
FROM SUNDAY NIGHT...THROUGH AT LEAST TUESDAY. GULF MOISTURE WILL
HAVE OVERSPREAD THE MIDWEST BY THIS TIME...AND WITH SHORTWAVES
RIPPLING OVER THE AREA SCATTERED CONVECTION WILL BE AROUND FROM
TIME TO TIME. HAVE CHANCE POPS IN THE REMAINDER OF THE EXTENDED
AND WHILE CERTAINLY MANY HOURS WILL BE DRY...IMPOSSIBLE TO TIME AT
THIS POINT. STRONG OR SEVERE STORMS MAY BE POSSIBLE DEPENDING ON
INSTABILITY...BUT WITH A DEEPLY OCCLUDED SYSTEM THIS SCENARIO IS
NOT AS WELL DEFINED AS 24 HOURS AGO. TEMPERATURES WILL REMAIN WELL
ABOVE NORMAL UNTIL THE LONGWAVE TROF CAN SHIFT THROUGH WHICH MAY
NOT BE UNTIL THE END OF THE FORECAST PERIOD OR LATER.

25
&&

.AVIATION...
ISSUED 655 AM CDT THU MAY 16 2013

AN ILL DEFINED FRONTAL BOUNDARY LIES NEARLY WEST/EAST ACROSS
CENTRAL ILLINOIS THIS MORNING. A BROKEN BAND OF SHOWERS AND A FEW
THUNDERSTORMS HAS BEEN MOVING JUST NORTH OF AND NEARLY PARALLEL TO
THE FRONT. THIS PRECIPITATION HAS BEEN ON THE DECREASE OVERALL
WITH THE GRADUAL LOSS OF THE NOCTURNAL LOW LEVEL JET. EXPECT AN
INCREASE IN SHOWER/STORM COVERAGE THIS AFTERNOON AND EARLY
EVENING AS THE FRONT BEGINS A SLOW NORTHWARD PUSH LATER TODAY...
ALONG WITH A DIURNAL INCREASE IN INSTABILITY. HOWEVER...AT THIS
POINT...CONFIDENCE IN TIMING/COVERAGE OF THE PRECIPITATION IS TOO
LOW TO GO ABOVE A VICINITY MENTION. WINDS WILL BE FAIRLY LIGHT FOR
THE MOST PART...WITH THE MOST NOTABLE SHIFTS OCCURRING IN THE
VICINITY OF FROPA OR A STORM INDUCED GUST FRONT.

BAK
&&

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

$$