Area Forecast Discussion
Issued by NWS Chicago, IL

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FXUS63 KLOT 210310
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1010 PM CDT MON OCT 20 2014

.DISCUSSION...
249 PM CDT

TONIGHT...
UPPER LEVEL WAVE CONTINUES TO ROTATE OVER NORTHEAST ONTARIO...WITH A
A COUPLE WEAK LOBES OF VORTICITY ROTATING AROUND THE BACK EDGE OF
THIS SYSTEM...PUSHING SOUTH INTO THE NORTHERN GREAT LAKES. VISIBLE
IMAGERY SHOWS CONSIDERABLE CLOUD COVER ACROSS MICHIGAN...STRETCHING
WEST ACROSS THE LAKE AND BEGINNING TO SLIDE INTO FAR NORTHEAST IL.
GUIDANCE SUGGESTS A FEW LIGHT SHOWERS WILL ACCOMPANY THIS WAVE AS IT
PUSHES SOUTHEAST ACROSS WISCONSIN AND PERHAPS INTO FAR NORTHEAST IL
LATE THIS EVE...BEFORE SHIFTING EAST INTO FAR NORTHWEST IN BY
DAYBREAK TUE. OTHERWISE EXPECT CLOUDS TO THICKEN THIS EVE ACROSS THE
CWFA...PERHAPS LESS CLOUD COVER ACROSS THE FAR WEST/SOUTHWEST
PORTIONS OF THE FORECAST AREA. WITH THE CLOUD COVER TONIGHT...THIS
SHOULD KEEP TEMPS GENERALLY AROUND 40 TO THE LOW 40S TONIGHT.

TUESDAY THROUGH THURSDAY...
500MB TROUGH AXIS WILL BEGIN TO PUSH EAST...WITH A HIGH AMPLITUDE
RIDGE BEGINNING TO BUILD INTO THE REGION FROM THE CENTRAL PLAINS.
THIS WILL BRING A BROAD SFC RIDGE TO THE AREA STRETCHING FROM
CENTRAL CANADA SOUTH TO THE WESTERN GULF. GUIDANCE THEN CONTINUES TO
MAINTAIN THIS FEATURE THROUGH THUR MORNING...HOWEVER THERE IS A WEAK
WAVE SLIDING EAST ACROSS THE CENTRAL CONUS WED NGT THAT IS PROGGED
TO LIFT NORTHEAST OF THE CWFA THUR AFTN/EVE. THIS SYSTEM COULD BRING
SOME LIGHT PRECIP TO THE AREA...BUT AT THIS TIME HAVE ONLY GONE WITH
SLIGHT CHANCE OF POPS GIVEN THE MOISTURE AVAILABILITY APPEARS TO BE
MINIMAL. TEMPS WILL GENERALLY BE IN THE UPR 50S TO LOW 60S...WITH
OVERNIGHT LOWS IN THE MID 30S TO MID 40S.

FRIDAY THROUGH MONDAY...
ENSEMBLES CONTINUE TO FEATURE A TROUGH PERSISTING ALONG THE FAR
SOUTHWEST CONUS...ALLOWING RIDGING TO DOMINATE THE CENTRAL CONUS
LATE IN THE WEEK INTO THE WEEKEND. THIS WILL LIKELY CONTINUE THE DRY
PATTERN FOR THE REGION. IN ADDITION IT APPEARS TEMPS WILL BE ABLE TO
STEADILY MODERATE...PERHAPS REACHING THE UPR 60S TO ARND 70.

ENSEMBLES DO SUGGEST THAT TOWARDS THE SECOND HALF OF THE WEEKEND THE
RIDGE WILL BEGIN TO DRIFT EAST...WITH A TROUGH DIGGING INTO THE
CENTRAL CONUS AND PERHAPS BRINGING UNSETTLED WEATHER BACK INTO THE
REGION EARLY NEXT WEEK.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 03Z...

* NORTH-NORTHEAST WINDS GREATER THAN 10 KT WITH GUSTS OF 17-20 KT
  TUESDAY.

* CIGS LOWER TO MVFR TUESDAY MORNING WITH ISOLATED SHOWERS
  POSSIBLE...ESPECIALLY AT MDW.

* MVFR CIGS PERSIST THROUGH MUCH OF THE DAY THEN SCATTER LATE
  AFTERNOON OR EARLY TUESDAY EVENING.

MDB

//DISCUSSION...UPDATED 03Z...

RESIDUAL LAKE INFLUENCE CONTINUES TO PRODUCE NORTHEAST WINDS AT
ORD/MDW/GYY. EXPECT THE LAKE IMPACT TO FADE IN THE NEXT HOUR OR
TWO ALLOWING WINDS TO TURN MORE STEADILY TO THE NORTH/NORTH-
NORTHWEST. CIGS WILL LOWER THROUGH THE NIGHT AND SHOULD BECOME
MVFR TUESDAY MORNING. ISOLATED TO SCATTERED SHOWERS ARE EXPECTED
TO DEVELOP OVER LAKE MICHIGAN LATE TONIGHT AND TUESDAY MORNING
WHICH WILL LIKELY IMPACT GYY AT TIMES. THE ILLINOIS SHORELINE WILL
PROBABLY ALSO SEE SOME SPOTTY SHOWERS WHICH MAY REACH ORD/MDW WITH
MDW HAVING THE GREATER POTENTIAL.

STEADY NORTH-NORTHEAST WINDS WILL SET UP TUESDAY MORNING WITH
GUSTS INTO THE 15-20 KT RANGE WHICH WILL EASE OUT TOWARDS RFD IN
THE AFTERNOON...THEN ELSEWHERE WITH SUNSET. MVFR CIGS LOOK TO
PERSIST THROUGH MUCH OF THE DAY WITH THE EXCEPTION BEING RFD WHICH
SHOULD SEE LESS COVERAGE BUT MAY VARY BETWEEN SCT AND BKN. DO NOT
HAVE A GREAT DEAL OF CONFIDENCE IN HOW LONG MVFR PERSISTS INTO THE
AFTERNOON OR EVENING BUT SUSPECT THERE WILL BE AT LEAST SOME
SCATTERING LATER IN THE DAY.

MDB

//ORD AND MDW CONFIDENCE...UPDATED 03Z...

* HIGH CONFIDENCE IN WIND FORECAST THROUGH TUESDAY.

* HIGH CONFIDENCE IN CIGS LOWERING TO MVFR TUESDAY MORNING
  PERSISTING THROUGH TUESDAY AFTERNOON BUT LOW CONFIDENCE IN
  TIMING OF LIFTING/SCATTERING TO VFR TUESDAY AFTERNOON/EVENING.

* MEDIUM CONFIDENCE IN SHRA OCCURRING AT MDW AND LOW CONFIDENCE IN
  OCCURRENCE AT ORD.

MDB

//OUTLOOK FOR ORD/MDW FOR 12Z WEDNESDAY-12Z MONDAY...UPDATED 00Z...

* WEDNESDAY...DRY/VFR. EAST/NORTHEAST WINDS.
* THURSDAY...DRY/VFR. SOUTH WINDS.
* FRIDAY...DRY/VFR. SOUTHWEST WINDS.
* SATURDAY...DRY/VFR. WEST WINDS.
* SUNDAY...DRY/VFR. SOUTH WINDS.

MDB

&&

.MARINE...

250 PM...LOW PRESSURE CONTINUES TO INFLUENCE THE REGION CENTERED
OVER NORTHERN LAKE HURON LATE THIS AFTERNOON AND IS EXPECTED TO
SLOWLY DRIFT EAST OVERNIGHT. THIS LOW WILL THEN REACH LAKE ONTARIO
AROUND DAYBREAK TUE. THE BACK EDGE OF THIS LOW CONTINUES TO
FEATURE A TIGHTENING PRESSURE GRADIENT...WHICH HAS PRODUCED GUSTY
WINDS JUST BEGINNING TO SLIDE OVER THE NORTHERN PORTIONS OF THE
LAKE. THESE GUSTY WINDS WILL EVENTUALLY SLIDE SOUTH THIS
EVENING...AND EXPECT NORTH GUSTS UP TO 30 KTS. HIGH PRESSURE OVER
ONTARIO WILL BEGIN TO BUILD SOUTH OVERNIGHT...THEN STRETCH FROM
ONTARIO SOUTH TO THE WESTERN GULF OF MEXICO BY TUE NGT. THIS WILL
BRING MUCH LIGHTER WINDS TO THE LAKE BY WED.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 7 AM WEDNESDAY.

&&

$$

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