Area Forecast Discussion
Issued by NWS Chicago, IL

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000
FXUS63 KLOT 252030
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
330 PM CDT TUE AUG 25 2015

.SHORT TERM...

TONIGHT THROUGH THURSDAY NIGHT...

232 PM...GENERALLY QUIET WEATHER EXPECTED THRU THE PERIOD.

LOW PRESSURE OVER JAMES BAY WILL CONTINUE TO LIFT NORTHEAST TONIGHT
AS HIGH PRESSURE OVER THE PLAINS SLOWLY SPREADS EAST TONIGHT AND
WEDNESDAY. WINDS WILL TURN MORE NORTHERLY ACROSS THE LAKE LATER
TONIGHT INTO WEDNESDAY MORNING AS THE HIGH APPROACHES. WITH THE
COLDER TEMPS ALOFT...RAIN SHOWERS WILL BE LIKELY EAST OF LAKE
MICHIGAN BUT SOME OF THESE MAY MAKE IT INTO NORTHEAST PORTER COUNTY
LATE TONIGHT INTO WEDNESDAY MORNING. APPEARS MOST OF THIS WILL
REMAIN EAST OF THE CWA AND MAINTAINED A DRY FORECAST.

EDGE OF THE CLOUD COVER CONTINUES TO SLOWLY MOVE EAST AND MAY SEE
SOME DECREASE IN CLOUDS DIURNALLY THIS EVENING BUT LAKE EFFECT CLOUD
COVER IS EXPECTED TO INCREASE OVERNIGHT INTO WEDNESDAY MORNING AND
THIS COULD LINGER THROUGH MUCH OF WEDNESDAY...THOUGH DO EXPECT SOME
SCATTERING AND THINNING BY WEDNESDAY EVENING.

WHILE TEMPS SHOULD WARM INTO THE LOWER/MID 70S WEDNESDAY...WINDS
TURN NORTHEAST OFF LAKE MICHIGAN AND TEMPS COULD COOL INTO THE
LOWER/MID 60S NEAR THE LAKE BY EVENING. TEMPS WARM BACK INTO THE
UPPER 70S THURSDAY BUT EASTERLY WINDS WILL CONTINUE TO KEEP THE
LAKESHORE AREAS COOLER. CMS

&&

.LONG TERM...
329 PM CDT

FRIDAY THROUGH TUESDAY...

MORE ZONAL FLOW ALOFT RETURNING FRIDAY AS STACKED LOW MOVES CONTINUES
TO EXIT THE REGION TO THE EAST. UPPER LEVEL SHORTWAVE TROUGH
RIDING THROUGH UPPER RIDGE EJECTS EAST INTO THE PLAINS AND
APPROACHES THE AREA FRIDAY BRINGING INCREASED CLOUD COVER WITH
INCREASING POPS WEST TO EAST FRIDAY AFTERNOON AND EVENING. LOW
LEVEL WARM AIR ADVECTION/SOUTHERLY FLOW WILL HELP BOOST TEMPS WELL
INTO THE 70S APPROACHING 80 SOME LOCATIONS AHEAD OF INCREASING
CLOUDS. SOME MODEL DIFFERENCES IN TIMING AND TRACK OF THE
SHORTWAVE STILL TO BE RESOLVED IN COMING RUNS HOWEVER BEST WINDOW
FOR RAIN APPEARS TO BE LATE FRIDAY NIGHT AND SATURDAY MORNING
ACROSS THE LOCAL AREA.

THIS UPPER LEVEL SHORTWAVE MOVES OFF TO THE EAST ONLY SLOWLY SUNDAY
AS MODELS TRENDING TOWARD DEVELOPING A MORE AMPLIFIED FLOW
PATTERN AGAIN FOR EARLY NEXT WEEK. UPPER RIDGING PREVAILING ACROSS
THE AREA MONDAY AND TUESDAY POINTING TOWARD DRY WEATHER AGAIN THAT
PERIOD WITH MAX TEMPS WELL INTO THE 80S... VERY WARM HEADING INTO
THE END OF AUGUST.

ED F

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 20Z...

* LOW CHANCE OF MVFR CLOUDS.
* NE TO E WINDS WEDNESDAY AFTERNOON.

KMD

//DISCUSSION...UPDATED 20Z...

UPPER LEVEL LOW PRESSURE SOUTH OF JAMES BAY WILL CONTINUE SLOWLY
LIFTING NORTH AND EAST THROUGH THE TAF PERIOD. MVFR/LOW END VFR
STRATOCUMULUS FIELD OVER THE TERMINALS HAS BEEN SLOW TO LIFT TODAY
GIVEN THE WEAK HEATING...BUT WE HAVE SEEN SOME SCATTERING/SLIGHT
LIFTING TO MORE OF A VFR SCT/BKN DECK...AND MOST GUIDANCE SUGGESTS
THIS CLOUD BASES SHOULD CONTINUE TO HOLD AT THESE LEVELS. WITH
THE UPPER LOW PULLING EAST...LOOKS LIKE THERE WILL BE SOME
SCATTERING OF THE CLOUD DECK OVERNIGHT INTO WEDNESDAY MORNING.

SURFACE HIGH PRESSURE SHIFTS NORTH THEN OUT OVER NORTHERN LAKE
MICHIGAN ALLOWING WINDS TO TURN NORTHERLY WEDNESDAY MORNING THAN
NORTHEASTERLY WEDNESDAY AFTERNOON. GUIDANCE KEEPS WINDS IN THE 7-9
KT RANGE AND THUS MEDIUM CONFIDENCE IN WINDS UNDER 10 KT. FORECAST
SOUNDINGS INDICATE SOME ADDITIONAL LOW END VFR CLOUDS REFORMING
AGAIN WEDNESDAY LATE MORNING.

KMD

//ORD AND MDW CONFIDENCE...UPDATED 20Z...

* MEDIUM-HIGH THAT CIGS HOLD JUST ABOVE MVFR.
* MEDIUM IN NE WINDS HOLDING UNDER 10KT WEDNESDAY AFTERNOON.

KMD

//OUTLOOK FOR ORD/MDW FOR 00Z THURSDAY-12Z TUESDAY...UPDATED 12Z...

WEDNESDAY NIGHT...VFR. EAST TO NORTHEAST WINDS.

THURSDAY...VFR. SOUTHEAST WINDS.

FRIDAY...CHC SHRA AND SCHC TSRA OVERNIGHT. SOUTH WINDS.

SATURDAY...CHC SHRA AND SCHC TSRA DURING THE DAY...SCHC SHRA
OVERNIGHT. MAINLY VFR. SOUTHEAST WINDS.

SUNDAY...VFR. SOUTH WINDS.

MONDAY...VFR. SOUTHWEST WINDS.

JEE

&&

.MARINE...
303 PM CDT

LOW PRESSURE NEAR JAMES BAY WILL MOVE ONLY SLOWLY EAST TONIGHT AND
WEDNESDAY. THIS WILL ALLOW A RIDGE OF HIGH PRESSURE OVER THE
NORTHERN PLAINS TO BUILD SLOWLY EAST INTO THE WESTERN GREAT LAKES
BY WEDNESDAY EVENING. WINDS WILL CONTINUE TO EASE AS THE LOW MOVES
AWAY AND THE RIDGE BUILDS OVER THE AREA THROUGH WEDNESDAY.

HIGH PRESSURE MOVING OVERHEAD EARLY THURSDAY WILL BRING A PERIOD
OF LIGHT AND VARIABLE WINDS DURING THAT TIME. AS THE HIGH MOVES
EAST LATER ON THURSDAY AND THURSDAY NIGHT INTO FRIDAY...
SOUTHERLY WINDS WILL SET UP ON THE BACK SIDE OF THE HIGH AND
INCREASE MODESTLY FRIDAY. WEAK LOW PRESSURE OVER THE CENTRAL
PLAINS WILL THEN LIFT NORTHEAST ON SATURDAY REACHING SOUTHERN LAKE
MICHIGAN SUNDAY... HELPING TO MAINTAIN A GENERALLY LIGHT WIND
REGIME THROUGH THE WEEKEND.

ED F

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...BEACH HAZARDS STATEMENT...INZ002 UNTIL 10 PM TUESDAY.

LM...NONE.
&&

$$

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