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000
FXUS63 KILX 170817
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
317 AM CDT FRI MAY 17 2013

.DISCUSSION...
ISSUED 317 AM CDT FRI MAY 17 2013

SHORT TERM...TODAY THROUGH SUNDAY

SURFACE BOUNDARY WHICH HAS BROUGHT SCATTERED STORMS TO THE AREA THE
PAST COUPLE DAYS HAS MIGRATED BACK NORTH AND NOW LIES NEAR THE
NORTHERN FRINGE OF THE CWA. THIS FEATURE WILL SLOWLY EDGE NORTH
TODAY...AND SOUTHEAST FLOW WILL CONTINUE TO BRING IN SEASONABLE
WARMTH AND MODEST HUMIDITY WITH DEWPOINTS IN THE LOW 60S. A CLOSED
UPPER LOW NOW TRACKING INTO SOUTHEAST MO IS FORECAST TO OPEN UP
AND LIFT TOWARDS THE LOWER OHIO VALLEY BY 00Z/SAT. INCREASING
MOISTURE AND LIFT ASSOCIATED WITH THIS LOW WILL BRING SCATTERED
CONVECTION BACK TO THE AREA TODAY. FEEL HIGHEST COVERAGE WILL BE
TIED TO DIURNAL HEATING...AND FOCUSED LIKELY POPS DURING THE
AFTERNOON. FOLLOWED 4KM WRF FOR CONVECTIVE TRENDS AS THIS MODEL
HANDLED YESTERDAYS SITUATION WELL. IN AREAS THAT DO SEE RAIN...HEAVY
RAINFALL RATES WILL AGAIN BE POSSIBLE AS PW RISES TO 1.5 INCHES
AND WINDS ALOFT ARE UNDER 15 KTS. THIS ACTIVITY SHOULD QUICKLY DIE
OFF THIS EVENING AS THE ATMOSPHERE STABILIZES.

FOR SATURDAY...THE UPPER LOW WILL SLOWLY DRIFT UP THE OHIO VALLEY
WITH ENOUGH LIFT AND MOISTURE LINGERING BACK INTO EASTERN IL TO
KEEP A CHANCE OF SCATTERED STORMS GOING. FARTHER WEST...DRY
WEATHER IS EXPECTED AS BRIEF UPPER RIDGING BUILDS TOWARDS THE
MISSISSIPPI VALLEY BY 00Z/SUN. BY SATURDAY NIGHT...A DEEP UPPER
TROUGH DIGGING EAST OF THE ROCKIES SPINS UP A SURFACE LOW OVER THE
CENTRAL PLAINS. THIS SENDS A WARM FRONT NORTHEAST ACROSS MO...WITH
ELEVATED CONVECTION POSSIBLY GETTING AS FAR NORTHEAST AS THE
WESTERN CWA LATE AND HAVE ADDED SCHC POPS TO ACCOUNT FOR THIS.

00Z MODELS SHOW THE WARM FRONT LIFTING WELL NORTH OF THE AREA ON SUNDAY
AND WITH 850 MB TEMPS RISING TO NEAR +20C HIGHS IN THE MID OR
UPPER 80S ARE POSSIBLE. MUCH OF THE CWA SHOULD REMAIN DRY WITH
WEAK CAPPING IN PLACE. HOWEVER ACROSS THE WEST WILL CARRY A LOW
CHANCE FOR AFTERNOON TSTMS AS CINH IS NEGLIGIBLE AND LEAD SHORTWAVE
ENERGY LIFTING OUT OF THE WESTERN TROF COULD SPARK SOME ACTIVITY.

LONG TERM...MONDAY THROUGH THURSDAY

MUCH OF THE EXTENDED FORECAST WILL BE ACTIVE AS A HIGH AMPLITUDE SLOW
MOVING UPPER TROF SHIFTS FROM THE NORTHERN PLAINS INTO THE GREAT
LAKES BY MID-WEEK. THIS WILL REQUIRE A PROLONGED PERIOD OF CHANCE
TO LIKELY POPS INTO WEDNESDAY. SUSTAINED SOUTHERLY FLOW AHEAD OF
THE PLAINS SURFACE LOW BRINGS GULF MOISTURE AND ASSOCIATED UPPER
60S TO AROUND 70F DEWPOINT POOL INTO THE MIDWEST. MODERATE TO HIGH
INSTABILITY WILL BE IN PLACE FOR MONDAY AND TUESDAY...AND AS
SEVERAL SHORTWAVES LIFT ACROSS THE CWA IN DIFLUENT SOUTHWEST
FLOW...ROUNDS OF STRONG TO SEVERE CONVECTION ARE POSSIBLE. LATEST
00Z MEDIUM RANGE MODEL RUNS SHOW THE ACTUAL COLD FRONT NOT
ARRIVING UNTIL LATE TUESDAY OR EARLY WEDNESDAY. SO IN ADDITION TO
POSSIBLE SEVERE WEATHER HEAVY RAIN ALSO MAY BE REALIZED IF THE CURRENTLY
ADVERTISED TRENDS OF A STRONG SLOW MOVING SYNOPTIC SYSTEM AND HIGH
PW AIRMASS MATERIALIZE. TEMPERATURES WILL REMAIN SEVERAL DEGREES
ABOVE NORMAL UNTIL THE FRONT EVENTUALLY PASSES. POST- FRONTAL
AIRMASS WILL BRING TEMPS BACK TO NEAR OR SLIGHTLY BELOW NORMAL FOR
THE END OF NEXT WEEK.



25
&&

.AVIATION...
ISSUED 1154 PM CDT THU MAY 16 2013

04Z/11PM RADAR IMAGERY SHOWS DRY CONDITIONS ACROSS MUCH OF CENTRAL
ILLINOIS...WITH ONE CLUSTER OF PERSISTENT SHOWERS/THUNDER BETWEEN
KVYS AND KPNT. STATIONARY FRONTAL BOUNDARY JUST NORTH OF THE I-74
CORRIDOR WILL CONTINUE TO TRIGGER ISOLATED CONVECTION
OVERNIGHT...HOWEVER IT IS EXPECTED TO REMAIN NORTH OF THE KILX
TERMINALS. UPPER LOW CURRENTLY SPINNING OVER THE OZARKS WILL LIFT
NORTHEASTWARD INTO THE OHIO RIVER VALLEY ON FRIDAY. DEEPER
MOISTURE ARRIVING WITH THIS FEATURE WILL LEAD TO SCATTERED SHOWERS
AND THUNDERSTORMS THROUGHOUT THE DAY INTO THE EARLY EVENING. BASED
ON NAM TIMING...HAVE INTRODUCED VCTS AT KSPI AND KDEC BY
13Z...THEN FURTHER NORTH TO KPIA BY 16Z. AS LOW SHIFTS FURTHER
EAST AND DAYTIME INSTABILITY IS LOST...CONVECTION WILL DISSIPATE
AFTER 02Z. WINDS WILL BE LIGHT AND SOUTHERLY OVERNIGHT...THEN WILL
BACK TO E/SE ON FRIDAY.

BARNES
&&

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

$$