Area Forecast Discussion
Issued by NWS Chicago, IL

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000
FXUS63 KLOT 032030
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
230 PM 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 20Z...

* WSWLY WINDS GUSTING TO 20-25KT UNTIL FROPA EARLY THIS
  EVENING...THEN WIND SHIFTING TO WNWLY OVERNIGHT AND NWLY
  TOMORROW GUSTING TO 20KT.

* IFR VIS IN -DZ/BR FOR A COUPLE MORE HOURS...IMPROVING TO MVFR IN
  BR UNTIL FROPA.

* IFR CIGS UNTIL FROPA...THEN IMPROVING TO MVFR OVERNIGHT INTO
  EARLY TOMORROW MORNING.

KREIN

//DISCUSSION...UPDATED 18Z...

WARM...MOIST ADVECTION HAS SET UP ACROSS THE REGION IN ADVANCE OF
A STRONG COLD FRONT EXTENDING FROM NERN MN THROUGH CNTRL IOWA.
CIGS HAVE BECOME MORE UNIFORMLY 005-007 ACROSS THE REGION AS
TEMPERATURES RISE INTO THE LOWER TO MIDDLE 30S AND DEWPOINTS RISE
INTO THE UPPER 20S TO LOWER 30S. DRY AIR OVERSPREADING THE NEARLY
SATURATED LOWER LEVELS HAS TRANSITIONED PCPN OVER TO DZ WHERE SFC
TEMPS ARE ABOVE FREEZING AND FZDZ WHERE TEMPS REMAIN BELOW
FREEZING. A FEW ISOLD POCKETS OF MORE STEADY RAIN REMAIN...BUT
SHOULD BE BRIEF. EXPECT THAT MDW/GYY HAVE ALREADY TRANSITIONED
OVER TO DZ...WHILE ORD/DPA/RFD REMAIN UNDER FZDZ. A SFC WAVE ALONG
THE FRONT IS QUICKLY TRACKING NEWD ALONG THE FRONT AND HAS ALREADY
MOVED INTO WISCONSIN...WITH A 7MB/3HR PRESSURE RISE/FALL COUPLET
GENERATING WIND GUSTS TO 25KT ACROSS THE REGION. EXPECT THE DZ TO
END AS THE SFC LOW CONTINUES NEWD INTO THE UPPER GREAT
LAKES...WITH LATEST RADAR IMAGERY SHOWING A RELATIVELY SHARP BACK
EDGE TO THE PCPN MOVING EWD THROUGH NCNTRL IL. CONDITIONS SHOULD
GRADUALLY IMPROVE TO MVFR AND VFR FOLLOWING THE FROPA AS
COLDER...DRIER AIR FILTERS ACROSS THE REGION. FOLLOWING THE
FROPA...EXPECT THAT STRONG ADVECTION BEHIND THE FRONT WILL HELP
DRIVE NWLY GUSTS TO 25KT TOMORROW.

KREIN

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

* MEDIUM CONFIDENCE IN TIMING PCPN ENDING.

* LOW CONFIDENCE IN TIMING OF CIGS/VIS IMPROVING TO MVFR AND VFR.

* 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...

230 PM...LOW PRESSURE OVER THE NORTHERN LAKES WILL MERGE WITH
DEEPER LOW PRESSURE OVER NORTHERN ONTARIO TONIGHT AND THEN MOVE
INTO QUEBEC WEDNESDAY MORNING. WINDS WILL BE SHIFTING WESTERLY
OVER THE NEXT FEW HOURS AND THEN MORE NORTHWEST ACROSS THE
SOUTHERN PART OF THE LAKE OVERNIGHT. THE GRADIENT WILL REMAIN
TIGHT AS HIGH PRESSURE BUILDS ACROSS THE NORTHERN AND CENTRAL
PLAINS WEDNESDAY AND WEDNESDAY NIGHT AND COMBINED WITH RETURNING
COLD AIR...WINDS TO 30KT LOOKS REASONABLE. AS THE HIGH MOVES EAST
ACROSS THE SOUTHERN LAKES AND OHIO VALLEY THURSDAY NIGHT INTO
FRIDAY...THE GRADIENT WILL TIGHTEN ACROSS THE WESTERN LAKES WITH
SOUTHWEST WINDS INCREASING BACK TO 30KT WITH SOME POTENTIAL FOR
LOW END GALES. THESE WINDS WILL GRADUALLY DIMINISH FRIDAY NIGHT AS
THE GRADIENT BEGINS TO WEAKEN. CMS

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS UNTIL 6 PM WEDNESDAY.

&&

$$

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