Area Forecast Discussion
Issued by NWS Chicago, IL

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000
FXUS63 KLOT 011352
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
852 AM CDT SAT NOV 1 2014

.SHORT TERM...
330 AM CDT

SATURDAY THROUGH SUNDAY...

THERE IS A HIGHLY AMPLIFIED FLOW PATTERN ACROSS THE CONTINENTAL
UNITED STATES. A LARGE UPPER TROUGH IS OFF THE PACIFIC COAST...WITH
AN UPPER RIDGE ACROSS THE CENTER OF THE COUNTRY AND EXTENDING INTO
NORTH CENTRAL CANADA. MEANWHILE...THE MASSIVE ANOMALOUS UPPER LOW
ASSOCIATED WITH THE ACTIVE WEATHER TO BEGIN THE WEEKEND OVER OUR
AREA FRIDAY CONTINUES TO DIG SOUTHEAST OF THE REGION EARLY THIS
MORNING...DRIVING TEMPERATURES INTO THE 30S AS FAR SOUTH AS CENTRAL
GEORGIA. A MODEST SURFACE PRESSURE GRADIENT REMAINS DRAPED OVER LAKE
MICHIGAN ON THE BACK SIDE OF THE DEPARTING UPPER LOW AS STRONG
SURFACE HIGH PRESSURE BUILDS EAST...WITH THE CENTER OF THE HIGH
CURRENTLY SPRAWLED OUT FROM NORTHERN LAKE SUPERIOR SOUTHEAST TO THE
SOUTHERN PLAINS.

RADAR CONTINUES TO SHOW MUCH LESS ORGANIZATION TO LAKE EFFECT SNOW
EARLY THIS MORNING AS DEEP LEVEL RH VALUES DECLINE
SIGNIFICANTLY...AND SOUNDINGS CONTINUE TO SHOW A RAPID DECLINE IN
INVERSION HEIGHTS. WINDS WILL ALSO CONTINUE THE DOWNWARD TREND AS
THE SURFACE HIGH TO THE WEST BECOMES CENTERED OVER NE ILLINOIS LATER
THIS AFTERNOON...BUT WINDS OFF THE LAKE WITH LESS FRICTION STILL ARE
BLOWING PRETTY GOOD ALONG THE SHORELINE. LOW LEVEL FLOW WILL REMAIN
OUT OF THE NORTHEAST INTO AT LEAST EARLY AFTERNOON...AND SOUNDINGS
CONTINUE TO SHOW THE LOW LEVEL MOISTURE REMAINS TRAPPED UNDER THE
INVERSION AWHILE LONGER...WHICH WILL ALLOW LOW CLOUDS TO LINGER FOR
SOME TIME TODAY...AND EVEN SOME CONTINUED LIGHT LAKE EFFECT
SHOWERS/FLURRIES THROUGH THE MORNING. THIS WILL KEEP READINGS FROM
GETTING OUT OF THE 40S TODAY. FINALLY TONIGHT THE HIGH IS
GENERALLY OVERHEAD. THIS WILL ALLOW FOR A DECENT RADIATIONS
COOLING SETUP AS WINDS SLACKEN AND SKIES CLEAR. EXPECT LOWS TO
DIP INTO THE 20S. VARIABLE CLOUDINESS DUE TO ANY LINGERING LOWER
CLOUD AND HIGHER CLOUDS PUSHING OVER THE UPPER RIDGE TO THE WEST
MAY KEEP THINGS IN CHECK A BIT...BUT EXPECT EVEN THE URBAN AREAS
TO GET DOWN TO NEAR 30.

ON SUNDAY THE UPPER RIDGE IN THE CENTER OF THE COUNTRY WILL BE
MOVING OVERHEAD AS THE SURFACE HIGH SHIFTS TO THE EAST...MEANING DRY
CONDITIONS CONTINUE.  LOWER LEVEL WARM ADVECTION UNDER SW FLOW WILL
ALLOW FOR SOME WARMING AFTER THE COOL START. EXPECT AFTERNOON
BREEZES AND READINGS TO GET INTO THE 50S...STILL COOL.

KMD

&&

.LONG TERM...
330 AM CDT

MONDAY THROUGH FRIDAY...

THE NEXT BATCH OF PRECIPITATION WILL HEADING OUR WAY LATER MONDAY
INTO TUESDAY AS THE TROUGH OFF THE PACIFIC MOVES THROUGH THE CONUS.
WARM ADVECTION WILL BE IN PLACE AHEAD OF THE TROUGH AS THE MAIN
SURFACE LOW ORGANIZES IN CANADA...WHICH DESPITE INCREASING CLOUD
COVER SHOULD PUSH TEMPS WELL THROUGH THE 50S TO NEAR 60. ON MONDAY THE
TROUGH AXIS SLIDES THROUGH MONDAY NIGHT WITH A WEAK COLD FRONT
WHICH WILL BE THE BEST CHANCE FOR SOME RAIN SHOWERS BEFORE
SHIFTING TO THE EAST. A DECENT BAROCLINIC ZONE...UPPER JET...AND
MODEST MOISTURE WILL BRING SOME RAIN TO MOST AREAS. NEAR NORMAL
READINGS IN THE MID 50S ARE EXPECTED.

WEDNESDAY LOOKS FAIRLY QUIET AS SURFACE HIGH PRESSURE BUILDS IN.
ANOTHER PACIFIC SYSTEM IN NW FLOW ALOFT WILL TRAVERSE THE AREA WEDS
INTO THURSDAY BRINGING ANOTHER CHANCE OF RAIN...BEST CHANCE FOR AREAS
EAST. AFTERWARDS...BEHIND THE COLD FRONT...CONDITIONS DRY OUT AND
READINGS DIP BACK INTO THE 40S TO NEAR 50.

KMD

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 14Z...

* NORTH WINDS AT ORD SHIFTING NORTH-NORTHEAST THIS MORNING...WHILE
  NORTH-NORTHEAST WINDS CONTINUING AT MDW. OCCASIONAL MORNING
  GUSTS TO 20 KT.

* 2800-3500 FT CIGS THROUGH EARLY AFTERNOON.

MDB/MTF


//DISCUSSION...UPDATED 12Z...

HIGH PRESSURE CONTINUES TO MOVE IN FROM THE WEST WHICH IS ALLOWING
WINDS TO STEADILY DIMINISH FROM WEST TO EAST. SPEEDS AT MDW/GYY
REMAIN STRONGEST WITH FREQUENT GUSTS GIVEN BETTER PROXIMITY TO THE
LAKE. LOWER END VFR LAKE EFFECT CLOUDS CONTINUE TO STREAM ACROSS
THE TERMINALS WITH BASES SLOWLY LOWERING TOWARD MVFR. BASED ON HOW
SLOW THE LOWERING HAS BEEN AND THE ARRIVAL OF DAYLIGHT...IN
CONJUNCTION WITH A FAIRLY DRY AIRMASS BELOW THE CLOUD DECK...HAVE
SOME DOUBTS THAT LOWERING TO MVFR WILL OCCUR. WILL RAISE CIGS TO
030 FOR NOW BUT THIS COULD EVEN BE A BIT TOO LOW.

WINDS WILL CONTINUE TO DIMINISH AS HIGH PRESSURE COMES OVERHEAD BY
EVENING SO AM EXPECTING GUSTS TO END INTO THE AFTERNOON FOR ALL
SITES EXCEPT GYY WHICH MAY HANG ON TO SOME UPPER TEENS GUSTS UNTIL
NEAR SUNSET. DIRECTION WILL BECOME A BIT MORE NORTHEASTERLY FROM
THIS MORNING ONWARD. CIGS WILL BEGIN TO LIFT THIS AFTERNOON AND
SHOULD BEGIN TO SCATTER AS LAKE PROCESSES WIND DOWN. TIMING OF THE
SCATTERING/CLEARING WILL BE SUBJECT TO ADJUSTMENT WITH UPCOMING
TAFS. WINDS WILL GO CALM OR LIGHT AND VARIABLE THIS EVENING THEN
TURN SOUTH TO SOUTHWEST SUNDAY MORNING WITH SPEEDS INCREASING TO
10-15 KT AS HIGH PRESSURE SHIFTS TO THE EAST.

MDB


//ORD AND MDW CONFIDENCE...UPDATED 14Z...

* HIGH IN WIND DIRECTION FORECAST. MEDIUM IN TIMING OF SPEEDS
  DIMINISHING TO LESS THAN 10 KT.

* HIGH IN CIGS REMAINING BETWEEN THE 2500-3500 FT RANGE THROUGH
  THE MORNING. MEDIUM CONFIDENCE AFTER.

MDB/MTF


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

SUNDAY NIGHT...DRY/VFR. SOUTH WINDS 10-20 KT.

MONDAY...DRY/VFR DURING THE DAY. SHRA LIKELY MONDAY NIGHT. GUSTY
SOUTHWEST WINDS 15-20 KT.

TUESDAY...SHRA/MVFR LIKELY. SOUTHWEST WINDS.

WEDNESDAY...DRY/VFR. SOUTHWEST WINDS.

THURSDAY...DRY/VFR. WEST-NORTHWEST WINDS.

FRIDAY...DRY/VFR. SOUTHWEST WINDS.

MDB

&&

.MARINE...
305 AM CDT

HIGH PRESSURE WILL STEADILY BUILD ACROSS LAKE MICHIGAN TODAY
BRINGING STEADILY DIMINISHING NORTH TO NORTHEAST WINDS. THE PRESSURE
GRADIENT REMAINS QUITE STRONG ACROSS THE FAR SOUTHERN SECTIONS OF
THE LAKE EARLY THIS MORNING WITH SOME OBSERVATIONS STILL REPORTING
LOWER END GALES. THE SOUTH BUOY CONTINUES TO GUST TO AROUND 30 KT
WITH SOME SHORE SITES PUSHING 35-40 KT. WITH SOME LAND BREEZE
CONVERGENCE SETTING UP SOME OF THE COASTAL OBS ALONG THE WI/IL
SHORELINE HAVE TURNED NNW AND AND THEREFORE ARE NOT REPRESENTING THE
FLOW OVER THE LAKE. THIS IS EVIDENCED BY THE SHARP DROP OFF IN WIND
SPEEDS WITH A SHIFT FROM NNE TO NNW...WHILE SITES THAT ARE STILL NNE
CONTINUE TO SHOW 35-40 KT. WITH THE DOWNWARD TREND AND A STEADILY
SHRINKING AREA OF HIGHER WIND SPEEDS AS THE HIGH BUILDS IN WILL
ALLOW THE GALE WARNING TO EXPIRE AT 09Z FOR THE OPEN WATERS AND THE
NEARSHORE. WILL MENTION A FEW 35 KT GUSTS IN THE TEXT PRODUCTS EARLY
THIS MORNING BUT EXPECT THESE TO BE DIMINISHED BY DAYBREAK IF NOT
SOONER. GIVEN THE CONTINUED LARGE WAVES ACROSS THE IL/IN NEARSHORE
WATERS WILL HOIST A SMALL CRAFT ADVISORY THROUGH THE AFTERNOON INTO
EARLY EVENING.

THE HIGH WILL BE OVERHEAD BY EVENING THEN SHIFT TO THE SOUTH AND
EAST TONIGHT. LOW PRESSURE OVER THE NORTHERN ROCKIES WILL MOVE
NORTHEAST INTO SOUTHERN MANITOBA LATER SUNDAY WHICH WILL SET UP A
TIGHTENING PRESSURE GRADIENT ACROSS LAKE MICHIGAN. THIS WILL LEAD TO
AN INCREASE IN SOUTHWESTERLY WINDS THROUGH THE DAY SUNDAY...WITH
GUSTS PUSHING 30 KT AT TIMES SUNDAY EVENING AND SUNDAY NIGHT. THE
GRADIENT WILL SLACKEN NORTH MONDAY MORNING ALLOWING WINDS TO EASE UP
ACROSS NORTHERN AREAS. THE LOW WILL CONTINUE NORTHWARD TOWARDS
HUDSON BAY MONDAY NIGHT WITH A COLD FRONT TRAILING IT AND CROSSING
THE LAKE MONDAY NIGHT/TUESDAY MORNING. THE PRESSURE GRADIENT WILL
TIGHTEN UP SOMEWHAT AHEAD OF THE FRONT ALLOWING WINDS TO INCREASE
MODESTLY ACROSS CENTRAL AND SOUTHERN SECTIONS OF THE LAKE LATER
MONDAY...BEFORE THEY SHIFT TO THE WEST BEHIND THE FRONT TUESDAY.
WEAK HIGH PRESSURE THEN BUILDS IN WEDNESDAY. ANOTHER LOW IS FORECAST
TO PASS OVER OR NEAR THE LAKE WEDNESDAY NIGHT BRINGING ANOTHER
INCREASE IN WINDS FROM THE NORTHWEST BEHIND IT...WITH FAIRLY STRONG
GUSTS POSSIBLE THANKS TO ANOTHER PUSH OF COLDER AIR BEHIND AN
ASSOCIATED COLD FRONT.

MDB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 10 PM SATURDAY.

&&

$$

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