Area Forecast Discussion
Issued by NWS Chicago, IL

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FXUS63 KLOT 030903
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
303 AM CST TUE MAR 3 2015

.SHORT TERM...
300 AM CST

THROUGH WEDNESDAY...

MAIN FORECAST CONCERNS THIS MORNING WILL BE DEALING WITH PRECIP TYPE
ISSUES WITH WARM FRONT LIFTING ACROSS THE REGION EARLY THIS MORNING.
SURFACE LOW IS IN PLACE ACROSS EASTERN COLORADO AND WESTERN KANSAS
EARLY WITH AXIS OF STRONGEST PRESSURE FALLS SPRAWLED ACROSS THE MID
MISSOURI VALLEY INTO SOUTHEASTERN MINNESOTA. MID LEVEL WARM
ADVECTION IS RAMPING UP ACROSS THE MIDWEST AND WILL CONTINUE TO
INCREASE ACROSS NORTHERN ILLINOIS OVER THE NEXT FEW HOURS...THEN
SHOULD START TO SPREAD NORTH AND NORTHEAST OF THE FORECAST AREA FROM
MID MORNING ON. WIDESPREAD PRECIPITATION NOTED ON RADAR ALREADY THIS
MORNING WITH REPORTS OF FREEZING RAIN AND SLEET UPSTREAM. BEST
CHANCE FOR ANY SNOW ACCUMULATIONS WITH THIS SYSTEM WILL BE ALONG AND
NORTH OF I-80...BUT PARTICULARLY CLOSER TO THE WI STATE LINE WHICH
WILL REMAIN MARGINALLY COLD ENOUGH ALOFT FOR SNOW THROUGH MID
MORNING. H9-H8 LAYER MAX WET BULB TEMPS WILL RISE ABOVE FREEZING
SOUTH OF THE I-80 CORRIDOR BY AROUND 12Z...AND ACROSS THE ENTIRE CWA
BY 15Z AT WHICH POINT SLEET OR FREEZING RAIN CAN BE EXPECTED FOR
AREAS WITH SURFACE TEMPS STILL BELOW FREEZING. GUIDANCE IS
INITIALIZING TOO COLD WITH SURFACE TEMPS THIS MORNING...AND SOME
MODELS SUCH AS THE NAM SEEM TO HOLD ON TO FREEZING TEMPS TOO
LONG...SO FEEL THE THREAT FOR FREEZING RAIN MAY BE SOMEWHAT
LIMITED...THOUGH ANY ICE ACCUMULATIONS WILL CAUSE ISSUES
PARTICULARLY WITH THE TIMING DURING THE MORNING COMMUTE. AREAS SOUTH
OF I-80 SHOULD SEE SURFACE TEMPS RISE ABOVE THE FREEZING MARK 13-15Z
AND THROUGH 15-17Z THE FREEZING LINE SHOULD LIFT UP TO THE STATE
LINE MARKING THE END OF THE FREEZING RAIN THREAT. MEANWHILE...LATE
THIS MORNING INTO THE EARLY AFTERNOON MID LEVEL DRY SLOT WILL PUNCH
IN FROM THE WEST WITH PRECIP TAPERING TO A LIGHT RAIN OR DRIZZLE
BEFORE ENDING ALTOGETHER THIS EVENING.

HIGH PRESSURE WILL BEGIN TO BUILD ACROSS THE NORTHERN PLAINS TONIGHT
WITH A MODERATE NORTHWEST GRADIENT AND COLD/DRY ADVECTION IN PLACE
TONIGHT. STEEP LOW LEVEL LAPSE RATES DEVELOP AND THERE IS SOME
INDICATION THERE MAY BE A FEW LIGHT FLURRIES THAT DEVELOP THIS
EVENING AND EARLY OVERNIGHT BEFORE DRIER AIR MOVES IN...BUT FOR NOW
CHANCES SEEM TOO LOW TO INCLUDE MENTION IN FORECAST. COLD ADVECTION
WILL DRIVE TEMPERATURES INTO THE SINGLE DIGITS IN THE NORTHWEST
CWA...AND UPPER TEENS TO LOW 20S IN THE SOUTHEAST. TEMPERATURES WILL
NOT REBOUND MUCH ON WEDNESDAY WITH HIGHS IN THE HIGH TEENS TO LOWER

DEUBELBEISS

&&

.LONG TERM...
300 AM CST

WEDNESDAY NIGHT THROUGH MONDAY...

FAIRLY QUIET WEATHER EXPECTED FROM MIDWEEK THROUGH THE WEEKEND. HIGH
PRESSURE WILL BUILD FROM THE NORTHERN PLAINS WEDNESDAY NIGHT TO
DOWNSTATE ILLINOIS THURSDAY. COLDER AIR WILL ACCOMPANY THE HIGH WITH
MODELS CONTINUING TO ADVERTISE H85 TEMPS AROUND -20C WEDNESDAY
NIGHT. HIGH PRESSURE CENTERED TO OUR WEST WILL ALLOW WESTERN
COUNTIES TO BEGIN TO CLEAR AND WINDS TO DECOUPLE ALLOWING TEMPS TO
RADIATE BELOW ZERO...THOUGH A MODEST GRADIENT AND LINGERING CLOUD
COVER IN EASTERN COUNTIES MAY PROP UP TEMPS ABOVE ZERO. HIGH
PRESSURE SHIFTS TO OUR EAST LATER ON THURSDAY AND RETURN FLOW AND
WARM ADVECTION WILL RESULT IN TEMPS LEVELING OFF OR RISING THURSDAY
NIGHT. THIS IS IN ADVANCE OF LOW PRESSURE OVER NORTHERN ONTARIO
DRAGGING A COLD FRONT ACROSS THE UPPER MIDWEST. TEMPERATURES SHOULD
BE ABLE TO RISE ABOVE FREEZING FRIDAY AND SATURDAY BEFORE THE COLD
FRONT PASSES THROUGH NORTHERN ILLINOIS SATURDAY AFTERNOON/EVENING.
FRONT IS PRETTY MOISTURE STARVED SO MAYBE A FEW FLURRIES IF IT
DOESNT COME THROUGH DRY.

DEUBELBEISS

&&

.CLIMATE...

A FEW RECORD LOW AND AND RECORD LOW MAXIMUM TEMPERATURES ARE IN
JEOPARDY ON WEDNESDAY AND THURSDAY.

HERE ARE THE CURRENT RECORDS FOR ROCKFORD AND CHICAGO. THE ONES THAT
STAND THE BEST CHANCE TO BE REACHED OR BROKEN HAVE A STAR (*) NEXT TO
THEM.

  WED 3/4  THU 3/5
ROCKFORD

RECORD LOW-11 (2002)-11 (2002)
RECORD LOW MAX 14 (2002)* 17 (1960)*

CHICAGO
RECORD LOW-12 (1873)  0 (1978)*
RECORD LOW MAX 17 (1890)* 12 (1901)

KMD/KJB/BMD

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* SNOW EXPECTED TO DEVELOP DURING PREDAWN HOURS...QUICKLY
  TRANSITIONING TO A SNOW/SLEET MIX AND THEN FREEZING RAIN DURING
  THE MORNING. TEMPS RISE TO/ABOVE FREEZING BY MIDDAY WITH PRECIP
  CHANGING TO RAIN/DRIZZLE.

* CIG/VIS EXPECTED TO DETERIORATE FAIRLY QUICKLY FROM VFR TO
  IFR/LIFR WITH PRECIPITATION THIS MORNING. SLOW IMPROVEMENT IN
  CONDITIONS EXPECTED LATER THIS AFTERNOON/EVENING...WITH MVFR
  CIGS LIKELY LINGERING TONIGHT.

* SOUTH-SOUTHEAST WINDS INCREASING 10-15 KT EARLY THIS MORNING AND
  BECOMING GUSTY AROUND 20 KTS AT TIMES WHILE BACKING SOUTH LATE
  THIS MORNING. SOUTHWEST WINDS GUSTING AROUND 20 KTS THIS
  AFTERNOON BECOME WEST-NORTHWEST BY EARLY EVENING AND REMAINING
  GUSTY.

RATZER

//DISCUSSION...UPDATED 06Z...

LOW PRESSURE WAS DEVELOPING OVER EASTERN COLORADO AROUND MIDNIGHT...
WITH SOUTH-SOUTHEAST WINDS INCREASING ACROSS THE PLAINS AND MIDWEST
AND STARTING TO PULL MOISTURE NORTHWARD FROM THE WESTERN GULF.
REGIONAL RADAR MOSAIC SHOWS PRECIPITATION BLOSSOMING ACROSS THE
MID-MISSISSIPPI VALLEY AND LIFTING NORTHEAST AHEAD OF WARM FRONT
DEVELOPING ACROSS MISSOURI AND KANSAS. FORECAST MODELS CONTINUE TO
DEPICT PRECIPITATION SPREADING ACROSS THE LOCAL TERMINALS ROUGHLY
10-12Z...WITH THERMAL PROFILES SUPPORTING INITIALLY SNOW...QUICKLY
MIXING WITH SLEET AND FREEZING RAIN AS TEMPERATURES WARM ALOFT.
SURFACE TEMPS LOOK TO CLIMB TO/ABOVE FREEZING BY LATE MORNING OR
MIDDAY WITH ANY LINGERING PRECIPITATION IN THE FORM OF RAIN OR
DRIZZLE AS THE BETTER FORCING WITH THE ELEVATED WARM FRONT LIFTS
NORTH OF THE AREA.

WITH DEVELOPMENT OF PRECIPITATION...GUIDANCE REMAINS STEADFAST IN
A RAPID DETERIORATION OF VFR CONDITIONS TO IFR/LIFR WITHIN A FEW
HOURS OF ONSET. CIGS SHOULD LIFT ABOVE LIFR THIS AFTERNOON AS WARM
FRONT MOVES NORTH...AND EVENTUALLY TO MVFR LATE THIS AFTERNOON AND
THIS EVENING AS A COLD FRONT PUSHES EAST ACROSS THE AREA.

SOUTH-SOUTHEAST WINDS WILL BACK MORE SOUTHEAST EARLY THIS MORNING
AND INCREASE INTO THE 10-15 KT RANGE AS THE LOW MOVES QUICKLY
ACROSS THE PLAINS. WINDS WILL BACK SOUTH BY LATE MORNING/EARLY
AFTERNOON AS THE LOW PASSES NORTH ACROSS WISCONSIN. FORECAST
SOUNDINGS SUPPORT GUSTS AROUND 20 KTS BY LATE MORNING...AND
CONTINUE TO INDICATE GUSTY CONDITIONS AS WINDS SHIFT SOUTHWEST
THIS AFTERNOON AND WEST-NORTHWEST THIS EVENING.

RATZER

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* MEDIUM IN TIMING PRECIP DEVELOPMENT AND TRANSITION OF P-TYPES AS
  WELL AS CIG/VIS IMPACTS.

* HIGH IN WINDS...AND DRY WEATHER WITH LINGERING MVFR CIGS THIS
  EVENING.

RATZER

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

WEDNESDAY...MVFR CIGS.

THURSDAY AND FRIDAY...VFR.

SATURDAY AND SUNDAY...MVFR CIGS POSSIBLE.

BEACHLER

&&

.MARINE...
214 AM CST

MAIN FOCUS FOR THE LAKE MICHIGAN FORECAST REMAINS IN THE NEAR
TERM...AS SOUTH WINDS INCREASE QUICKLY THIS MORNING IN ADVANCE OF AN
AREA OF LOW PRESSURE MOVING QUICKLY FROM THE PLAINS TO THE WESTERN
LAKES BY THIS EVENING. SOUTH WINDS TO 30 KT...WITH A FEW GALE FORCE
GUSTS TO 35 KT...ARE EXPECTED ON MAINLY THE SOUTHERN PORTION OF THE
LAKE. THE LOW WILL TRAIL A COLD FRONT ACROSS THE LAKE EARLY THIS
EVENING WHICH WILL SHIFT WINDS TO THE WEST INITIALLY AND MORE
NORTHWEST OVERNIGHT AND WEDNESDAY...AS THE GRADIENT CONTINUES TO
SUPPORT 25-30 KT WINDS AS HIGH PRESSURE SLOWLY BUILDS FROM THE
NORTHERN PLAINS TO THE OHIO VALLEY. THE HIGH WILL PASS SOUTHWEST OF
THE LAKES THURSDAY AND THURSDAY NIGHT ALLOWING WINDS TO EASE AND
BACK SOUTHWEST BY EARLY FRIDAY. THE GRADIENT WILL TIGHTEN UP ONCE
AGAIN FRIDAY HOWEVER...BETWEEN THE HIGH RETREATING TO THE SOUTHEAST
AND AN AREA OF LOW PRESSURE MOVING NORTH OF THE LAKES ACROSS
ONTARIO. 30 KT SOUTHWESTERLIES LIKELY FRIDAY...BEFORE THE LOW TRAILS
A COLD FRONTAL TROUGH INTO THE AREA EARLY SATURDAY AND ALLOWS WINDS
TO RELAX A BIT AND SHIFT TO THE WEST.

SMALL CRAFT HEADLINES REMAIN UP FOR THE ILLINOIS AND INDIANA
NEARSHORE TODAY THROUGH WEDNESDAY EVENING FOR THE 25-30 KT WINDS.
RECENT POLAR-ORBITING SATELLITE IMAGERY FROM MONDAY AFTERNOON SHOWS
A GOOD PORTION OF THE ILLINOIS SHORE TO BE MAINLY OPEN WATER OR THIN
ICE FLOES...THUS HAVE INCLUDED WAVE FORECAST FOR ILLINOIS WATERS
WHILE INDIANA SHORE APPEARS TO REMAIN LARGELY ICE-COVERED. THE SAME
GOES FOR WESTERN PORTIONS OF NORTHERN LAKE MICHIGAN...WHICH APPEAR
TO HAVE A FAIR AMOUNT OF OPEN WATER.

RATZER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...WINTER WEATHER ADVISORY...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-
     ILZ010-ILZ011-ILZ012-ILZ013-ILZ014-ILZ019-ILZ020-ILZ021-
     ILZ022-ILZ023-ILZ032-ILZ033-ILZ039 UNTIL NOON TUESDAY.

IN...WINTER WEATHER ADVISORY...INZ001-INZ002-INZ010-INZ011-INZ019
     UNTIL NOON TUESDAY.

LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 6 PM WEDNESDAY.

&&

$$

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