Area Forecast Discussion
Issued by NWS Chicago, IL

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FXUS63 KLOT 031622
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1022 AM CST TUE MAR 3 2015

.UPDATE...
1022 AM CST

THE MORE SIGNIFICANT PRECIP IS MOVING OFF TO THE EAST AND SHOULD SEE
PRECIP TAPER TO DRIZZLE/FREEZING DRIZZLE WITH JUST SOME INTERMITTENT
LIGHT RAIN OR FREEZING RAIN INTO THE EARLY AFTERNOON. TEMPERATURES
SHOULD CONTINUE TO INCH UPWARD AND CLIMB ABOVE FREEZING ACROSS THE
AREA IN THE NEXT COUPLE HOURS. IT IS POSSIBLE THAT WINTER WX
ADVISORY COULD NEED TO BE EXTENDED A COUPLE OF HOURS OVER NORTHERN
PORTIONS OF THE CWA...WILL CONTINUE TO MONITOR TEMP TRENDS AND MAKE
A LAST MINUTE DECISION ON THAT.

IZZI

&&

.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 15Z...

* FREEZING RAIN TURNING TO DRIZZLE AS TEMPS RISE ABOVE FREEZING
  LATE MORNING/MIDDAY.

* GENERALLY IFR VIS THROUGH LATE MORNING AND IFR CIGS THROUGH
  EARLY AFTERNOON. CIGS IMPROVING TO MVFR MID AFTERNOON AND VIS
  IMPROVING TO VFR MID AFTERNOON.

* SOUTH WINDS GUSTING TO ARND 25KT THROUGH MID DAY...VEERING
  SOUTHWEST THIS AFTERNOON AND NORTHWEST WINDS THIS EVENING.
  GUSTINESS TO PERSIST THROUGH TONIGHT.

KREIN

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

AREA OF PRECIPITATION HAS OVERSPREAD THE TERMINALS EARLY THIS
MORNING...WITH SOME MODERATE SNOW AT TIMES FROM ORD
NORTH/NORTHWEST. NORTHERN TERMINALS...RFD...DPA...ORD WILL LIKELY
CONTINUE TO BE THE FOCUS FOR HEAVIER SNOW/SLEET THIS MORNING WITH
OCCASIONALLY LOWER VIS/CIG CONDITIONS RESULTING. FARTHER SOUTH
SOME DRYING IN THE MID-LEVELS IS RESULTING IN LIGHTER PRECIP WHICH
WILL AFFECT MDW/GYY...AND MAY RESULT IN MORE OF A FZRA/FZDZ TREND
RATHER THAN SNOW FOR MUCH OF THE MORNING AT THOSE LOCATIONS.
IN ANY CASE...WARMING ALOFT WILL EVENTUALLY TURN PRECIP FROM SNOW
TO SLEET/FREEZING RAIN OR DRIZZLE OVER THE NEXT FEW HOURS...AND
EVENTUALLY TO RAIN/DRIZZLE AS SURFACE TEMPS RISE ABOVE FREEZING
LATER THIS MORNING. PRECIP IS EXPECTED TO END LATER THIS AFTERNOON
AS WINDS SHIFT WEST AND DRIER AIR FILTERS IN.

SPEAKING OF WINDS...WINDS ARE CURRENTLY SOUTHEAST AROUND 10 KT BUT
WILL INCREASE 10-15 KT WITH GUSTS AROUND 20 KT BY LATE MORNING...
BACKING TO THE SOUTH AND SOUTHWEST INTO THIS AFTERNOON AS LOW
PRESSURE MOVES ACROSS WISCONSIN. TRAILING COLD FRONT WILL SHIFT
WINDS WEST THIS EVENING...WITH GUSTS 20-25 KT LINGERING INTO
TONIGHT.

RATZER

//ORD AND MDW CONFIDENCE...UPDATED 15Z...

* MEDIUM CONFIDENCE IN TIMING OF PRECIP TYPE CHANGES AND CIG/VIS
  IMPACTS.

* LOW CONFIDENCE IN DZ END TIME.

* HIGH CONFIDENCE IN WIND TRENDS.

KREIN

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

WEDNESDAY NIGHT THROUGH FRIDAY...VFR.

SATURDAY THROUGH MONDAY...MVFR CIGS POSSIBLE.

RATZER

&&

.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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