Forecast-Discussion
000
FXUS63 KLOT 312354
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
654 PM CDT SAT JUL 31 2010
.DISCUSSION...
250 PM CDT
THERE WILL BE SOME FOG TONIGHT. THUNDERSTORMS ARE EXPECTED TO
RETURN MONDAY NIGHT THROUGH WEDNESDAY.
TONIGHT...THE COOLER AIR WILL MOVE INTO THE FORECAST AREA AND
WITH THE RESIDUAL MOISTURE FROM THE RAIN ...FOG MAY DEVELOP.
THE LOW OVER SOUTHERN ILLINOIS IS FORECAST TO MOVE EAST BY
SUNDAY. WE USED THE NAM AND OUR LOCALLY RUN WRF MODEL. THOSE
MODELS WERE THE MOST CONSISTANT WITH THE MOVEMENT OF THE SURFACE
LOW DURING THE LAST 6 HOURS.
SUNDAY THROUGH MONDAY NIGHT...WE USED THE ECMWF MODEL FOR THE
FORECAST. A SURFACE HIGH WILL MOVE THROUGH ILLINOIS SUNDAY. THE
SURFACE HIGH WILL MOVE EAST BY EARLY MONDAY MORNING. A LOW IS
FORECAST TO MOVE INTO MISSOURI BY TUESDAY AFTERNOON. THE EQUIVALENT
POTENTIAL TEMPERATURE FORECAST SHOWS A WARM FRONT OVER CENTRAL
ILLINOIS.
TUESDAY THROUGH WEDNESDAY...THE MODELS SHOW SOME STRONG WARM AIR
ADVECTION OVER NORTHERN ILLINOIS TUESDAY. THERE IS ALSO FORECAST
HIGH VALUES OF PRECIPITABLE WATER AND MOISTURE ADVECTION. THERE
COULD BE THUNDERSTORMS WITH HEAVY RAIN TUESDAY AND TUESDAY NIGHT.
WE WILL WATCH FOR POTENTIAL FLOODING FOR TUESDAY AND TUESDAY
NIGHT.
SOME OF THE RIVERS MAY REMAIN IN FLOOD AND OTHER RIVERS MAY GO
ABOVE FLOOD STAGE TUESDAY NIGHT AND WEDNESDAY.
THURSDAY THROUGH FRIDAY...A STATIONARY FRONT MAY LAY ACROSS
CENTRAL ILLINOIS. THERE WILL BE A CHANCE OF THUNDERSTORMS
THURSDAY. THE HIGH TEMPERATURES MAY REACH THE UPPER 80S.
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 00Z...
FOG/IFR POTENTIAL OVERNIGHT
SHEA
//DISCUSSION...UPDATED 00Z...
A VERY WEAK PRESSURE GRADIENT WILL GENERATE LIGHT AND SOMEWHAT
VARIABLE WINDS OVER THE NEXT DAY OR SO...CIGS EVENTUALLY RAISED TO
VFR LATE IN THE AFTERNOON AND CONTINUE TO GO FROM BROKEN TO
SCATTERED TO FEW TO EVEN CLEAR IN SOME LOCATIONS. THE LACK OF
DIRECT SOLAR HEATING THIS AFTERNOON HINDERED ANY DRYING IN THE
BOUNDARY LAYER AND WILL HELP TO CONTRIBUTE TO FOG DEVELOPMENT OVERNIGHT.
AT THIS POINT - FIGURE THE OUTLYING AREAS WILL GET DOWN TO LIFR
LEVELS...AND THE POTENTIAL IS THERE TO GO EVEN LOWER. FOR
ORD/MDW...WHERE THE URBAN HEAT ISLAND PLAYS MORE OF A ROLE...NOT
ANTICIPATING VISBYS TO FALL BELOW MVFR AT THIS TIME...THOUGH IF
TRENDS ARE DETERIORATING FASTER THAN ANTICIPATED...COULD SEE THEM
FALL TO IFR LEVELS.
SHEA
//ORD AND MDW CONFIDENCE...UPDATED 00Z...
HIGH CONFIDENCE ON CIGS REMAINING AOA VFR THROUGH THE EVENING. MEDIUM
CONFIDENCE OF MVFR OVERNIGHT...AND EVEN LOWER IN OUTLYING AREAS.
SHEA
//OUTLOOK FOR ORD/MDW FOR 06Z MONDAY-12Z FRIDAY...UPDATED 18Z...
SUNDAY NIGHT...IFR POSSIBLE.
MONDAY...CHC OF TSRA AT NIGHT...OTHERWISE VFR.
TUESDAY...CHC OF TSRA...OTHERWISE VFR.
WEDNESDAY...VFR.
THURSDAY...VFR.
FRIDAY...VFR.
LENNING
&&
.MARINE...
107 PM CDT
A LARGE TROUGH OF LOW PRESSURE MOVED ACROSS THE WESTERN GREAT
LAKES AS HIGH PRESSURE STARTED TO NOSE INTO THE REGION. THE
SURFACE GRADIENT WILL SLACKEN AND WINDS WILL BECOME MUCH LIGHTER.
AS THE HIGH DRIFTS TO THE EAST ON SUNDAY EVENING...THE GRADIENT
WILL TIGHTEN AND WINDS INCREASE OUT OF THE SOUTH AS A COLD FRONT
APPROACHES THE LAKES FROM THE WEST. THE FRONT SHOULD REACH THE
LAKE TUESDAY. THE FRONT WILL THEN SWEEP ACROSS THE LAKE BY
TUESDAY NIGHT. HIGH PRESSURE WILL AGAIN BUILD IN ACROSS THE REGION
AS THE COLD FRONT EXITS.
SHEA
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&
$$
NWS LOT Office Area Forecast Discussion
