Area Forecast Discussion
Issued by NWS Chicago, IL

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000
FXUS63 KLOT 041153
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
553 AM CST WED MAR 4 2015

.SHORT TERM...
316 AM CST

TODAY THROUGH FRIDAY...

COLD FRONT WHICH MOVED ACROSS THE AREA LAST EVENING HAS PUSHED INTO
THE OHIO VALLEY OVERNIGHT...THOUGH PUSH OF COLDER ARCTIC ORIGIN AIR
HAS BEEN GRADUAL. AREA OF STRONGER NORTHWEST WINDS AND A SHARPER
GRADIENT TO COLDER/DRIER TEMP/DEW POINT NOTED IN 08Z SURFACE
ANALYSIS FROM EAST CENTRAL WI INTO NORTHWEST IL AND NORTHERN
MO...AND THIS WILL CONTINUE TO PUSH SOUTHEAST ACROSS THE AREA TODAY.
THIS PERSISTENT COLD ADVECTION WILL KEEP TEMPERATURE TREND RATHER
FLAT TODAY...WITH ONLY A FEW DEGREES RISE OVER MORNING LOWS NEAR 10
ABOVE NORTHWEST...AND RELATIVELY STEADY READINGS IN THE LOWER 20S IN
THE SOUTHEAST. PARTIAL CLEARING WAS WORKING INTO WESTERN PARTS OF
THE FORECAST AREA EARLY THIS MORNING...THOUGH ADDITIONAL MID/HIGH
CLOUDS WERE NOTED UPSTREAM ACROSS THE PLAINS AND THESE WILL CONTINUE
TO SPREAD NORTHEAST ACROSS THE AREA THIS MORNING AS ANOTHER MINOR
AMPLITUDE SHORT WAVE LIFTS NORTHEAST ACROSS THE AREA AHEAD OF
POSITIVE TILT UPPER TROUGH WHICH WILL SLOWLY PUSH SOUTHEAST ACROSS
THE REGION THROUGH THURSDAY MORNING. PASSAGE OF THIS FEATURE AND THE
RESULTING HEIGHT RISES AND DEEP SUBSIDENCE BEHIND IT WILL FINALLY
ALLOW SURFACE HIGH PRESSURE TO BUILD INTO THE AREA THURSDAY AND
THURSDAY NIGHT. DURING THIS PERIOD...ARCTIC AIR WILL BE IN PLACE
WITH 850 MB TEMPS NEAR -20 C. LOWS TONIGHT WILL DIP INTO THE SINGLE
DIGITS BELOW ZERO MAINLY ACROSS NORTH CENTRAL IL WHERE CLEAR SKIES
AND LIGHTER WINDS ARE MOST LIKELY...WHILE SOME PATCHY CLOUD COVER
AND MODEST NORTHWEST WINDS WILL KEEP EASTERN/SOUTHEASTERN PARTS OF
THE CWA GENERALLY IN THE SINGLE DIGITS ABOVE ZERO. DESPITE A GOOD
AMOUNT OF SUNSHINE ON THURSDAY...SHALLOW MIXING OF COLD AIR MASS
WITHIN THE PASSING SURFACE RIDGE LOOKS TO LIMIT MAX TEMPS TO THE
LOW-MID TEENS. CLEAR SKIES AND LIGHT WINDS THURSDAY EVENING SHOULD
ALLOW A QUICK DROP IN TEMPS AGAIN INTO +/- SINGLE DIGITS...BEFORE
INCREASING SOUTH WINDS AND WARM ADVECTION DEVELOPING ALOFT WORK TO
PRODUCE STEADY/RISING TEMPERATURES OVERNIGHT PARTICULARLY ACROSS
NORTH CENTRAL IL. WIND CHILL READINGS WILL DROP INTO THE -15 TO -20
DEGREE RANGE BOTH LATE TONIGHT AND AGAIN THURSDAY NIGHT...BUT SHOULD
REMAIN JUST ABOVE ADVISORY CRITERIA EXCEPT FOR A BRIEF TIME AT THE
COLDEST SPOTS OVER NORTH CENTRAL IL.

ON FRIDAY...WHILE FLOW REMAINS NORTHWEST ALOFT THE LOW LEVEL WINDS
WILL BE GUSTY FROM THE SOUTH-SOUTHWEST. THIS WILL MARK THE BEGINNING
OF A WARMING TREND...WITH TEMPERATURES APPROACHING THE FREEZING MARK
ACROSS THE WESTERN COUNTIES OF THE CWA ALBEIT WITH THOSE GUSTY WINDS
MAINTAINING A BRISK FEEL TO THE DAY WITH WIND CHILLS IN THE TEENS.

RATZER

&&

.LONG TERM...
316 AM CST

SATURDAY THROUGH TUESDAY...

FROM THE WEEKEND INTO EARLY NEXT WEEK...THE UPPER FLOW MAINTAINS A
BROAD EASTERN CONUS UPPER TROUGH WHICH IS LESS AMPLIFIED THAN IN
RECENT WEEKS. A SERIES OF SHORT WAVE IMPULSES DOES PASS SOUTHEAST
THROUGH THE FLOW ACROSS THE UPPER MIDWEST AND GREAT LAKES REGION.
HOWEVER...SURFACE HIGH PRESSURE BECOMES ANCHORED FROM TEXAS ACROSS
THE SOUTHEASTERN STATES AND KEEPS ANY SIGNIFICANT GULF MOISTURE
RETURN FROM REACHING THE MIDWEST. HAVE MAINTAINED A DRY FORECAST
THROUGH THE PERIOD...AS TIMING/AMPLITUDE DETAILS OF INDIVIDUAL MINOR
SHORT WAVES LOWER CONFIDENCE IN NARROWING A SHORT WINDOW OF ANY
LIGHT PRECIP POTENTIAL IN OTHERWISE FAIRLY DRY REGIME. MODERATION OF
TEMPERATURES THROUGH THE PERIOD LOOKS TO BRING US BACK TO NORMAL OR
SLIGHTLY ABOVE BY MONDAY/TUESDAY. IN ADDITION TO WORKING ON MELTING
OUR SNOWPACK...MEDIUM RANGE TEMP FORECASTS BY THE MIDDLE OF NEXT
WEEK INDICATE SOME 50 DEGREE WEATHER MAY BE IN STORE FOR OUR
WINTER-WEARY CWA.

RATZER

&&

.CLIMATE...

WE COULD COME CLOSE TO A COUPLE RECORDS WITH THIS NEXT COLD SPELL.
THE ONES WITH STARS (*) ARE MOST VULNERABLE.

  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)

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 12Z...

* GUSTY NORTHWEST WINDS.

BMD

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

HIGH PRESSURE BUILDING ACROSS THE NORTHERN PLAINS WILL RESULT IN
VFR CONDITIONS AND BREEZY NORTHWEST WINDS THROUGH THE TAF PERIOD.
WIND GUSTS WILL LIKELY PICKUP AFTER DAYBREAK AND LAST AT LEAST
UNTIL SUNSET IF NOT A LITTLE LATER. GUIDANCE HAS BACKED OFF SOME
ON THE WIND SPEEDS TODAY SO TAPERED THE MAGNITUDE OF THE GUSTS
BACK INTO THE HIGH TEENS IN THE TAFS. MID AND HIGH LEVEL CLOUDS
ARE EXPECTED THROUGH THE PERIOD...AND LOWER COLD AIR STRATOCUMULUS
MAY FORM LATER TODAY BUT FOR NOW EXPECT COVERAGE TO REMAIN FEW TO
SCATTERED.

BMD


//ORD AND MDW CONFIDENCE...UPDATED 12Z...

* MEDIUM-HIGH CONFIDENCE IN WIND DIRECTION...MEDIUM CONFIDENCE IN
  WIND GUST SPEEDS.

BMD

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

THURSDAY NIGHT...VFR.
FRIDAY THROUGH SUNDAY...MVFR POSSIBLE. SUNDAY...
MONDAY THROUGH TUESDAY...PRIMARILY VFR.

BMD

&&

.MARINE...
301 AM CST

A COLD FRONT HAS DROPPED ACROSS LAKE MICHIGAN WITH HIGH PRESSURE
BUILDING INTO THE NORTHERN PLAINS TODAY RESULTING IN MODERATE
NORTHWEST WINDS. WINDS ARE EXPECTED TO PEAK AROUND 30 KT TODAY
WHICH COMBINED WITH COLDER TEMPERATURES MOVING OVER THE LAKE
COULD RESULT IN SOME FREEZING SPRAY. WINDS SHOULD TAPER GRADUALLY
TONIGHT AS THE HIGH MOVES ACROSS THE MIDWEST...THEN BACK TO THE
SOUTHWEST THROUGH THE DAY THURSDAY AS THE HIGH SETTLES ALONG THE
OHIO VALLEY. WINDS INCREASE AGAIN FRIDAY AHEAD OF A COLD
FRONT...BUT WARM ADVECTION OVER THE LAKE SHOULD HELP KEEP THE
GUSTS IN CHECK. THE COLD FRONT WILL PUSH ACROSS LAKE MICHIGAN LATE
FRIDAY NIGHT INTO EARLY SATURDAY.

BMD

&&

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

&&

$$

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