976
FXUS63 KLOT 041925
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
225 PM CDT SAT JUL 4 2009
DISCUSSION
221 PM CDT
MODELS RELIABLY CLOSE ON PASSAGE OF THIS SYSTEM NOW SPREADING RAIN
ACROSS THE FCST AREA. CURRENT LOW LVL JET FEEDING GULF MSTR OVER
THE WARM FRONTAL BOUNDARY ACROSS CENTRAL ILLINOIS WHICH IS PROGGED
TO REMAIN SOUTH OF NRN IL/NRN INDY THRU THE EVENT. NOT MUCH IN
ELEVATED INSTABILITY. NAM INDICATING A MAX LIFTED INDEX AREA ALONG
AND NORTH OF I-80. CAPES RISING ABOVE ZERO ALONG AND SOUTH OF THIS
WARM FRONT WAY TO THE SOUTH. SO LITTLE EVIDENCE OF ANY TSTM SUPPORT
HERE TO DEAL WITH AND WILL ONLY MENTION SHOWERS FOR FORECAST
PACKAGE THIS AFTN.
MID LVL TROF SUPPORTING WHAT CONVECTION IS AVAILABLE WILL DIVE SE
FROM ERN IA TO CENTRAL IL THIS EVENING WHERE MODELS TEND TO SLOW IF
NOT PAUSE FURTHER MOTION SOUTHEAST UNTIL MORNING. AT THAT
TIME...THIS UPR TROF STARTS FILLING AND KICKING OUT TO THE SOUTHEAST
AGAIN INTO CENTRAL INDIANA. THIS MOVEMENT A BIT SLOWER THAN PREVIOUS
RUNS AND HAVE EXTENDED THE END OF RAIN FOR SOUTHEAST PORTIONS OF THE
CWA UNTIL AROUND MIDNIGHT. ALBEIT HAVE RATHER LIGHT POPS SOUTH OF
I-80 FOR THIS EVENING...BUT THINK IT TOO EARLY TO NIX PCPN
COMPLETELY TOO EARLY.
SRN IOWA WAS RECEIVING SIGNIFICANT RAINFALLS FROM THIS SYSTEM THIS
MRNG BUT LITTLE EVIDENCE OF DELUGES IN NRN IL CWA AS YET. RADAR
MOVEMENT WUD SUGGEST BETTER QPF DIVING SE THRU CENTRAL IL. BASED
ON RADAR EXTENT OF PCPN...END OF IT PROBABLE IN NRN TWO TIERS OF
COUNTIES ARND 6PM BUT NOT DEPARTING SRN TIER OF COUNTIES UNTIL
AFTER 9PM.
AS MID LVL TROF DIVES SE TOWARD THE OHIO VALLEY...RATHER WEAK AND
DIFFUSE HIGH PRESSURE FOLLOWS OVERNIGHT INTO SUNDAY. MODELS
SUGGESTING ANTICYCLONIC FLOW EARLY BUT SECONDARY WAVE MOVING DOWN
LK MICHIGAN DURING THE DAY SUNDAY. NOT EXPECTING ANY PCPN WITH
THIS BUT CYCLONIC CURVING OF LOW LVL FLOW WUD SUGGEST SOME
DEVELOPING AFTN CU ACROSS NERN IL...DISSIPATING IN THE EVENING
SUNDAY NIGHT. SHUD BE SUNSHINE AVAILABLE THOUGH ON SUNDAY TO ALLOW
TEMPS TO CLIMB INTO THE LOW 80S. WEAK SFC FLOW SHUD PERMIT A LAKE
BREEZE SUN AFTN WITH THAT MUCH LAND AND LAKE TEMP DIFFERENTIAL.
THIS SECONDARY TROF MOVES SE AND WEAKENS SUN NIGHT. HOWEVER BOTH NAM
AND GFS INDICATING ANOTHER MID LVL WAVE DIVING SE FROM WI ON MONDAY
WITH SOME CAPE SUPPORT FOR CONVECTION...BUT NOT MUCH CONFIDENCE
BASED ON RATHER RAGGED ORGANIZATION OF LOW LVL FEATURES...LACKING
LOW LVL JET MOISTURE INPUT. WILL CONTINUE WITH CURRENT PROJECTION OF
DRY WX THRU MIDWEEK BUT PICK UP ON CLOUD COVER A BIT.
AFTER WEDNESDAY...UPR FLOW FLATTENS ACROSS THE UPR MIDWEST. WHILE
PERMITTING MAJOR SYSTEMS TO GLIDE NORTH OF IL AND ACROSS THE UPPER
GREAT LAKES...THE UPPER RIDGING POKING NE FROM THE DESERT SW ALSO
ALLOWS 850 TEMPS IN THE MID TO UPPER 70S TO INVADE THE MS VLY FOR
THE LATTER HALF OF THE WEEK. DAYTIME TEMPS LIKELY TO RESPOND TO
THIS IN THE MID AND UPPER 80S WHILE SOUTH TO SOUTHWEST SFC WINDS
TAP DEWPTS IN THE MID 60S OR BETTER. THUS A LATE WEEK SWELTER IS
PROBABLY IN STORE.
RLB
AVIATION
125 PM CDT
1800 UTC TAFS...NORTHERN PORTION OF AREA OF MORE SOLID LIGHT RAIN
CONTINUES TO SPREAD EAST-SOUTHEAST ACROSS NORTHERN IL AND
NORTHWEST IN AT MIDDAY AS MAIN SHORT WAVE TROUGH MOVES FROM
SOUTHEAST IA AND EASTERN MO OVER CENTRAL AND SOUTHERN IL.
AS THIS MORE WIDESPREAD RAIN IN AND MOISTENS THE LOWER LAYERS
AREAS OF MVFR AND LOCAL IFR CEILINGS SPREADING IN. EXTRAPOLATION
OF BACK EDGE OF PREVAILING RAIN ARRIVES AT CHI VICINITY AROUND 22Z
AND LINGERING SHOWERS END AROUND 00Z.
SHOWERS HAVE BEEN DEVELOPING ACROSS SOUTHEAST MN INTO WEST CENTRAL
WI ALONG FRONTAL BOUNDARY DRAPED ACROSS THIS AREA AND AS A SECOND
SHORT WAVE DROPS FROM THE EASTERN DAKOTAS TOWARD SOUTHWEST MN AND
NORTHWEST IA. MODELS KEEP THE SHOWERS IN THE VICINITY OF THE
BOUNDARY ACROSS CENTRAL WI WHILE DAMPING OUT THE SHORT WAVE AS IT
MOVES FURTHER EAST DURING THE AFTERNOON AND EARLY EVENING.
SUBSIDENCE FOLLOWING MAIN SHORT WAVE TROUGH PASSAGE WILL LEAD TO
CLEARING OVERNIGHT. LINGERING SHALLOW MOIST LAYER ALONG WITH EXPECTED
ADDITION OF SIGNIFICANT AMOUNTS OF SMOKE FROM FIREWORKS...LEGAL AND
OTHERWISE...TONIGHT WILL SHOULD LEAD TO MVFR VISIBILITY IN WITH
BR..FU..HZ WITH SURFACE BASED INVERSION FORMING IN LIGHT SURFACE
FLOW IN WEAK SURFACE RIDGE.
TRS
MARINE
217 PM CDT
LOW PRESSURE IN NORTHWEST MO MOVES EAST-SOUTHEAST TONIGHT REACHING
THE LOWER OH VALLEY BY MORNING...AND CENTRAL TN BY SUN EVENING.
THIS ALLOWS BROAD RIDGE TO SETTLE SOUTHEASTWARD FROM THE DAKOTAS
INTO THE MID MS VALLEY. THE RIDGE WILL GRADUALLY SHIFT EAST ACROSS
THE REGION THROUGH THE MIDDLE OF THE WEEK. BY LATE WED THE HIGH
WILL BE POSITIONED OVER THE NORTHEAST U.S. AND LOW PRESSURE WILL
BE TRACKING ACROSS SOUTHERN MANITOBA.
TRS
LOT WATCHES/WARNINGS/ADVISORIES
IL...NONE.
IN...NONE.
LM...NONE.
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page