National Weather Service Raw Text Product

355 
FXUS63 KILX 071750
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1250 PM CDT TUE MAY 7 2013

.DISCUSSION...
ISSUED 1030 AM CDT TUE MAY 7 2013

RADAR AND SATELLITE TRENDS SHOW A LINGERING BAND OF MID CLOUDS AND
SPRINKLES WILL AFFECT AREAS GENERALLY ALONG A LINE FROM EFFINGHAM
TO PARIS THE REST OF THE MORNING. AS INSTABILITY PARAMETERS BECOME
MORE FAVORABLE FOR STRONG UPDRAFTS THIS AFTERNOON...SHOWERS AND
ISOLATED STORMS WILL BECOME POSSIBLE. SATELLITE IMAGES INDICATE A
BAND OF DRY MID LEVEL AIR ACROSS INDIANA IS POISED TO ROTATE
WESTWARD INTO OUR EASTERN AREAS THIS AFTERNOON...WHICH WILL WORK
TO DESTABILIZE THE AIRMASS AS WELL. EVAPORATIVE COOLING IN THE DRY
LAYER WILL CREATE STEEPER LAPSE RATES AND INCREASED ELEVATED MIXED
LAYER /EML/ CAPE VALUES. NO SEVERE STORMS ARE EXPECTED...BUT SOME
GUSTY WINDS, SMALL HAIL, AND BRIEF HEAVY DOWNPOURS WILL BE
POSSIBLE.

THE SHOWERS AND STORMS SHOULD GENERALLY COME TO AN END BY THIS
EVENING...WITH DRY CONDITIONS OVERNIGHT AND WEDNESDAY.

TEMPERATURES WILL BE WARMER THIS AFTERNOON NORTHWEST OF I-55 WHERE
SUNSHINE WILL PREVAIL FOR MOST OF THE DAY. EXPECT UPPER 70S TO
NEAR 80 IN THAT AREA. ADDITIONAL CLOUD COVER SHOULD KEEP THE
SOUTHEAST AREAS IN THE MID 70S. BRIEF CLEARING TOWARD
LAWRENCEVILLE MAY ALLOW THAT AREA TO SEE UPPER 70S AS WELL.

UPDATED FORECAST INFO WILL BE AVAILABLE SHORTLY.

SHIMON

&&

.AVIATION...
ISSUED 1250 PM CDT TUE MAY 7 2013...FOR THE 18Z TAFS

A LAYER OF HIGHER RH AT 4-5K FT IS STARTING TO FILL IN ACROSS THE
SOUTHEAST HALF OF THE AREA...WHERE MU CAPE VALUES ARE CLIMBING
BETWEEN 500 AND 1000 J/KG. SATELLITE IMAGES ARE SHOWING THE CU
FIELD WITH SOME STRONGER UPDRAFTS ALREADY AT 1730Z SOUTHWEST OF
SPI AND EAST OF CHAMPAIGN. WE ADDED A VCSH FOR THE SOUTHERN AND
EASTERN TERMINALS OF SPI/DEC/CMI FROM 20Z TO 00Z. WE DID NOT
INCLUDE THUNDER YET... SINCE COVERAGE OF ANY STORMS SHOULD BE
ISOLATED ENOUGH TO MISS THOSE TERMINAL SITES. WILL MONITOR
PROGRESS OF THUNDER CLOSELY FOR THE NEED TO ADD TS IN AN UPDATE.

WINDS WILL REMAIN GENERALLY LIGHT FROM THE NORTH TO NORTHEAST...AS
LOW PRESSURE CONTINUE TO CHURN OFF TO THE EAST OF ILLINOIS. 

PRECIP SHOULD QUICKLY DIMINISH THIS EVENING...WITH LIGHT NORTH
WINDS.

TOMORROW MORNING LOOKS TO BE SIMILAR TO TODAY...WITH A CU FIELD
DEVELOPING IN THE HEAT OF THE DAY. A STRAY SHOWER OR TWO MIGHT
DEVELOP JUST BEYOND THIS TAF PERIOD...WED AFTERNOON.

SHIMON
&&

.PREV DISCUSSION...
ISSUED 311 AM CDT TUE MAY 7 2013
UPPER AIR PATTERN A BIT DIFFUSE IN THE CENTER OF THE CONUS THIS
MORNING...AND MUCH OF THE MIDWEST. SE DOMINATED BY PERSISTENT LOW
OF THE LAST FEW DAYS...CONTINUING TO SPIN AND PUSH PLENTY OF AC
INTO THE REGION. ANOTHER LOW STILL JUST OFF THE SOUTHERN PACIFIC
COAST...AND MAKING VERY LITTLE PROGRESS OVERALL. WAVE OVER NRN
PLAINS ACTUALLY ON TRACK TO BE THE EVENTUAL KICKER FOR THE SERN
LOW. HOWEVER...ALL OF THE SYSTEMS RATHER SLOW TO PROGRESS.
STILL A CONCERN THAT THIS TREND WILL CONTINUE AND THROW OFF THE
FORECAST TIMING A BIT. THAT INCONSISTENCY IS PART OF THE REASON
FOR RATHER DIFFUSE POPS BTWN THE NRN WAVE AND THE SWRN
LOW...THOUGH THE DEPICTION OF BOTH OF THEM IS STARTING TO SEPARATE
A BIT IN THE MODELS. LITTLE BIT OF A WARM UP ON THE WAY IN THE
SHORT TERM...AS THE MID-LEVELS WARM IN THE WAKE OF THE LOW DRIFTING
EWD.

SHORT TERM...TODAY AND TOMORROW...
AC PERSISTENT THROUGH THE MORNING IN THE RUC...AND WITH THE SLOW
MOTION OF THE LOW TO THE SE EXPECTED TO CONTINUE...FEEL MORE OF A
SLOW PROGRESSION IS THE WAY TO GO. HOWEVER...NOT EXPECTING MUCH IN
THE WAY OF A HINDRANCE TO THE WARMUP...PARTICULARLY NW OF THE
ILLINOIS RIVER VALLEY THAT MAY SEE A BIT MORE SUNSHINE. IN THE
SE...WITH THE COOLER TEMPS AND MORE CLOUD COVER...A BIT OF A
CHANCE FOR SOME ISO AFTERNOON SHOWERS VERY MUCH STILL UNDER THE
INFLUENCE OF CYCLONIC FLOW. TOMORROW...WARM UP ANTICIPATED TO BE
MORE WIDESPREAD AND DRY THROUGH THE DAY. POPS RETURN FOR WED NIGHT
AS THE WAVE IN THE NRN STREAM EJECTS THROUGH THE MIDWEST. RATHER
QUICK MOTION OF THE LOW IN THE MODELS LOOKS A BIT SUSPICIOUS AS
THE DEEPER TROF OVER THE DESERT SW SLOWS EVEN MORE. HOPEFULLY THE
NEXT COUPLE OF RUNS WILL ACTUALLY BE ABLE TO SAMPLE MORE OF THE
SWRN WAVE AND BRING A LITTLE MORE CONFIDENCE TO THE PATTERN SHIFT
OVERALL.  

LONG TERM...THURSDAY THROUGH MONDAY...
THESE TWO WAVES WILL DRIVE THE FORECAST FOR THE NEXT FEW DAYS.
GFS/ECMWF/NAM ALL RATHER DAMP WITH A STRETCHED OUT FRONTAL
BOUNDARY BTWN THE TWO WAVES ADVANCING INTO THE FA. LACK OF FLOW
DIRECTION ALOFT...RATHER DIFFUSE AIR MASSES OVERALL...EVEN THE COLD
AIR SHOT IS RATHER BRIEF. WILL NEED TO ADDRESS THE AMOUNT OF
ACTUAL CONVERGENCE ON THE BOUNDARY BTWN THE IMPULSES AND CLEAN UP
THE POPS A LITTLE BIT THURS NIGHT/FRI. FRONTAL LOCATION WILL BE
VERY IMPORTANT ON THE OTHER SIDE OF THE FIRST WAVE. THAT BEING
SAID...MODELS ALSO BEGINNING TO SHIFT AND ALTER THE SECOND WAVE
OUT OF THE SW TO JUST A PORTION OF THE ENERGY...LEAVING THE
BROADER TROF IN PLACE. YET ANOTHER PATTERN SHIFT IN THE
PERSISTENCE TO KEEP AN EYE ON. DEEPER LOW TRAVELING ALONG THE NRN
STREAM DRAGGING A FRONT THROUGH THE AREA AND ASSOCIATED PRECIP FOR
SATURDAY SHOWING WELL IN BOTH MODELS. SYSTEM MOVING RATHER QUICKLY
AND FORECAST DRIES OUT ON THE OTHER SIDE OF SATURDAY...AND BRIEFLY
CHILLY ON SUNDAY. 

HJS 


&&

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

$$