Area Forecast Discussion
Issued by NWS Central Illinois

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000
FXUS63 KILX 261951
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
251 PM CDT SUN JUL 26 2015

.SHORT TERM...(TONIGHT)
ISSUED AT 251 PM CDT SUN JUL 26 2015

MORNING MCS HAS COMPLETELY DISSIPATED ACROSS CENTRAL ILLINOIS EARLY
THIS AFTERNOON...WITH 19Z/2PM RADAR IMAGERY SHOWING NO LINGERING
PRECIP.  THE FOCUS FOR ADDITIONAL CONVECTION THIS AFTERNOON AND
EVENING WILL SHIFT FURTHER NORTH AND EAST ALONG A NEARLY STATIONARY
FRONTAL BOUNDARY EXTENDING FROM NORTH-CENTRAL INDIANA INTO EASTERN
IOWA.  SCATTERED THUNDERSTORMS ARE ALREADY DEVELOPING ALONG THE
BOUNDARY WITHIN A NARROW INSTABILITY AXIS CHARACTERIZED BY SBCAPES
OF 1500 TO 2500J/KG.  HRRR HAS BEEN CONSISTENTLY SHOWING STORMS
FIRING ALONG THE FRONT THIS AFTERNOON, AS WELL AS ALONG AN OUTFLOW
BOUNDARY/DIFFERENTIAL HEATING BOUNDARY CREATED BY THE MORNING MCS.
GIVEN CURRENT SATELLITE/RADAR TRENDS...SEE NO REASON TO STRAY FROM
THIS SOLUTION.  AS A RESULT...HAVE FOCUSED HIGHEST POPS ALONG/NORTH
OF I-74 AND EAST OF I-55 THIS AFTERNOON INTO THE EVENING.  ANY
STORMS THAT DEVELOP WILL BE DIURNALLY DRIVEN AND WILL LIKELY
DISSIPATE AFTER SUNSET.  AFTER THAT...THE QUESTION BECOMES WHETHER
ANY NOCTURNAL CONVECTION CAN DEVELOP OVERNIGHT.  THE HRRR AND RAPID
REFRESH MODELS SAY NO...HOWEVER THE NAM KEEPS AT LEAST SCATTERED
PRECIP GOING.  THE MAIN 850MB JET WILL BE ORIENTED FROM THE SOUTHERN
PLAINS INTO THE DAKOTAS TONIGHT...SO THERE WILL NOT BE MUCH SUPPORT
FOR OVERNIGHT STORMS IN ILLINOIS.  WITH THAT BEING SAID...NAM DOES
SHOW A WEAK 20-25KT BRANCH OF THE LLJ NOSING INTO THE AREA.  WITH
THIS WEAK INFLOW COMBINED WITH THE PRESENCE OF THE STATIONARY
FRONTAL BOUNDARY IN THE VICINITY...HAVE OPTED TO MAINTAIN JUST
SLIGHT CHANCE POPS AFTER MIDNIGHT.  LOW TEMPERATURES WILL ONCE AGAIN
BE IN THE LOWER 70S.

&&

.LONG TERM...(MONDAY THROUGH SUNDAY)
ISSUED AT 251 PM CDT SUN JUL 26 2015

WITH HIGH PRESSURE TO THE NORTHEAST AND A WEAK RESIDUAL BOUNDARY IN
OR CLOSE TO THE CWA...BELIEVE A SMALL CHANCE/SLIGHT CHANCE OF PCPN
WILL REMAIN POSSIBLE TOMORROW THROUGH TUE. THIS WILL ONLY BE SEEN
THROUGH MONDAY NIGHT IN THE WORDING...BUT WILL BE SEEN THROUGH TUE.
ONCE THIS WEAK BOUNDARY BREAKS DOWN ENOUGH TUE NIGHT SHOULD BE MOSTLY
DRY EXCEPT IN THE NORTHWEST OF THE IL RIVER WITH APPROACH OF THE
NEXT WEATHER SYSTEM. MODELS HAVE GOTTEN LITTLE FASTER WITH THIS
FRONT AND IT NOW ARRIVES EARLY ON WED IN THE AREA. CONVECTION WILL
BE POSSIBLE ALONG THIS FRONT WED AND THEN QUICKLY EXIT THE AREA LATE
WED AFTERNOON...SO WED NIGHT SHOULD BE DRY THROUGHOUT THE CWA.

TEMPS WILL BE QUITE WARM THROUGH WED WITH UPPER 80S TO LOWER 90S
POSSIBLE MON AND WED...AND LOWER TO MIDDLE 90S LIKELY FOR TUESDAY.
THIS HEAT WILL COMBINE WITH DWPTS IN THE 70S...UPPER 70S ON
TUESDAY...TO CREATE HEAT INDEX VALUES OF 90S TO 105 FOR MON AND
WED...AND 105-110 FOR TUESDAY. HEAT ADVISORY CRITERIA...105...WILL
BE CLOSE TOMORROW BUT ONLY IN EXTREME WESTERN COUNTIES. SO LEANING
AWAY FROM ADVISORY AT THIS TIME. CRITERIA IS MET ON TUE AND THEN
MAYBE IN THE SOUTHEAST PARTS OF THE CWA FOR WED. OVERNIGHT SHIFT CAN
GET ANOTHER LOOK FOR TOMORROW BECAUSE CLOUDS AND POSSIBLE PCPN COULD
BE A LIMITING FACTOR.

ONCE THE MID WEEK FRONT MOVES THROUGH DRY WEATHER IS EXPECTED THE
REST OF THE WEEK AND INTO THE WEEKEND. COOL CANADIAN HIGH PRESSURE
IS EXPECTED OVER THE AREA...WHICH WILL ALSO BRING IN DRIER DWPTS TO
THE AREA. THIS RIDGE DOES BEGIN TO BREAK DOWN OVER THE WEEKEND AND
WILL ALLOW A FRONT TO DROP INTO THE AREA FOR THE LAST PART OF THE
WEEKEND. FOR NOW WILL JUST HAVE A SLIGHT CHANCE OF PCPN FOR SAT
NIGHT AND SUNDAY. TEMPS WILL ALSO BE COOLER WITH AFTERNOON HIGHS
REMAINING IN THE 80S THROUGH THE PERIOD AND OVERNIGHT LOWS IN THE
60S.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z MONDAY AFTERNOON)
ISSUED AT 1239 PM CDT SUN JUL 26 2015

DECAYING MCS CONTINUES TO TRACK ACROSS THE ILLINOIS RIVER VALLEY
EARLY THIS AFTERNOON...WITH 17Z/12 PM RADAR IMAGERY SHOWING ONLY
LIGHT SHOWERS REMAINING. HAVE INTRODUCED PREVAILING LIGHT RAIN AT
BOTH KPIA AND KSPI BETWEEN 18Z AND 19Z...BUT THINK THE PRECIP WILL
COMPLETELY DISSIPATE BEFORE PUSHING ANY FURTHER EASTWARD. WILL
HAVE TO KEEP AN EYE ON THE OUTFLOW BOUNDARY FROM THIS SYSTEM AS
ISOLATED CONVECTION MAY DEVELOP FURTHER EAST OVER THE NEXT COUPLE
OF HOURS. IN ADDITION...SEVERAL HIGH-RES MODELS ARE SUGGESTING
SCATTERED SHOWERS/STORMS MAY FIRE ALONG A STATIONARY FRONTAL
BOUNDARY DRAPED ACROSS NORTH-CENTRAL ILLINOIS THIS AFTERNOON INTO
THE EARLY EVENING. HAVE THEREFORE INCLUDED VCTS AT THE I-74
TERMINALS BETWEEN 20Z AND 02Z-03Z. ONCE ANY DIURNALLY DRIVEN
CONVECTION DISSIPATES...DRY CONDITIONS ARE EXPECTED FROM MID-EVENING
THROUGH MONDAY MORNING. DUE TO THE HIGHER DEWPOINT AIRMASS IN
PLACE ACROSS THE REGION AND CONTINUED LIGHT/VARIABLE WINDS...MAY
SEE SOME FOG OVERNIGHT AS WELL. DO NOT THINK IT WILL BECOME
WIDESPREAD OR DENSE...BUT WILL MENTION SLIGHTLY REDUCED VISBYS IN
THE TAFS LATE TONIGHT.


&&

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

$$

SHORT TERM...BARNES
LONG TERM...AUTEN
AVIATION...BARNES


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