Area Forecast Discussion
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000
FXUS63 KLOT 251957
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
257 PM CDT WED MAR 25 2015

.SHORT TERM...
228 PM CDT

THROUGH THURSDAY EVENING...

MAIN CONCERN IN THE NEAR TERM WILL BE ANOTHER ROUND OF RAIN
OVERSPREADING SOUTHERN PORTIONS OF THE FORECAST AREA...WITH THE
BEST CHANCES APPEARING ALONG AND SOUTH OF A OTTAWA TO GARY LINE.
THIS AFTERNOON...ONE SURFACE LOW IS ANALYZED OVER LAKE SUPERIOR
WITH A COLD FRONT STRETCHING SOUTH ALONG THE MISSISSIPPI RIVER
VALLEY. MEANWHILE...ANOTHER LOW IS LOCATED NEAR THE TEXAS
PANHANDLE WITH TROUGHING EXTENDING EAST INTO THE MID MISSISSIPPI
VALLEY. WATER VAPOR IMAGERY SHOWS A SHORTWAVE TROUGH OVER SE
WY/NRN CO AND IS PROGGED TO MOVE ACROSS THE CENTRAL PLAINS TONIGHT
WITH A WEAK STABLE WAVE DEVELOPING ALONG THE TROUGH OVER THE MID
MISSISSIPPI VALLEY. AS THIS OCCURS...F-GEN WILL INCREASE NORTH OF
THE SURFACE WAVE WITH PRECIP SPREADING NORTH ACROSS CENTRAL
ILLINOIS LATE THIS EVENING INTO THE EARLY OVERNIGHT HOURS. EXPECT
A SHARP CUTOFF OF PRECIP ON THE NORTH SIDE OF THIS SYSTEM WITH
MUCH OF THE NORTHERN HALF OF THE CWA EXPECTED TO REMAIN DRY
OVERNIGHT. EVEN IN AREAS WITH THE STRONGEST F-GEN...DRY AIR IS
NOTED BELOW 700MB AND WILL TAKE SOME TIME TO SATURATE...SO INITIAL
RADAR RETURNS WILL LIKELY ONLY BE VIRGA AS THE COLUMN SATURATES
TOP-DOWN. PRECIPITATION SHOULD CLEAR THE FORECAST AREA BY AROUND
DAYBREAK THURSDAY WITH ATTENTION TURNING TO TEMPERATURES. COLD
ADVECTION WILL DRIVE 850MB TEMPS FROM AROUND 5C TODAY TO AROUND
-7C BY MID AFTERNOON THURSDAY. COLD ADVECTION WILL RESULT IN STEEP
LAPSE RATES...SO AS MID-HIGH CLOUDS EXIT TO OUR EAST...EXPECT COLD
AIR STRATOCUMULUS TO FILL IN IMMEDIATELY BEHIND RESULTING IN
MOSTLY CLOUDY CONDITIONS THROUGH THE DAY. MIXING DOWN TEMPS FROM
AROUND 900MB RESULTS IN HIGH TEMPS IN THE LOW 40S TOMORROW.

DEUBELBEISS

&&

.LONG TERM...
228 PM CDT

THURSDAY NIGHT THROUGH WEDNESDAY

AN ELONGATED UPPER LEVEL TROUGH WILL EXTEND FROM NORTHERN QUEBEC
THROUGH TEXAS THURSDAY EVENING.  THE TROUGH WILL SLOWLY SHIFT EAST
WITH THE TROUGH AXIS MOVING THROUGH THE REGION FRIDAY MORNING.  HIGH
PRESSURE WILL ALSO BE CENTERED OVER SOUTH CENTRAL CANADA AND DRIFT
SOUTHEAST. WINDS BECOME NORTH TO NORTHEAST RESULTING IN A FAVORABLE
FETCH FOR LAKE EFFECT PRECIP.  NOT OVERLY IMPRESSED WITH THE LAKE
EFFECT PARAMETERS FOR THE IL SIDE OF THE LAKE THURSDAY EVENING SO
CAPPED POPS IN THE SLIGHT CHANCE RANGE.  FORECAST SOUNDINGS FEATURE
A BIT OF LLWS THAT WILL PROBABLY LEAD TO MULTI-BANDED LAKE EFFECT.
PRECIP COULD BEGIN TO FALL AS A RAIN/SNOW MIX AS SFC TEMPS WILL BE A
BIT ABOVE FREEZING AND WE WILL NOT BE SATURATED IN THE DGZ.  HOWEVER
EXPECTING SATURATION TO QUICKLY OCCUR AND TURN THE PRECIP OVER TO
SNOW.

WINDS BECOME DUE NORTH AFTER MIDNIGHT THURSDAY NIGHT LEADING TO A
BETTER CHANCE FOR LAKE EFFECT SNOW OVER NORTHWEST
INDIANA...ESPECIALLY FRIDAY MORNING. WIND SHEAR REDUCES SO LIKING
OUR LOCAL ARW/S SOLUTION OF A SINGLE BAND OVER NORTHWEST INDIANA.
IT/S STILL A BIT FAR OUT TO IDENTIFY EXACTLY WHERE THE BAND WILL SET
UP SO HAVE A BROAD AREA OF CHANCE POPS LATE THURSDAY NIGHT INTO
FRIDAY MORNING. FOR SNOW TOTALS...WENT A BIT LOWER THAN PREVIOUSLY
FORECAST FOR THE IL SIDE WITH TOTALS LESS THAN A HALF INCH.  FOR NW
INDIANA...EXPECTING AROUND AN INCH OF NEW SNOW WITH LOCALLY HIGHER
TOTALS IF A STRONG BAND OF SNOW FORMS.  EXPECTING LAKE EFFECT SNOW
TO DIMINISH IN THE EARLY AFTERNOON AS WE LOSE FORCING BUT SCATTERED
FLURRIES COULD HANG AROUND ALL AFTERNOON.

A SURFACE HIGH MOVES OVER THE REGION FRIDAY EVENING.  WINDS DIMINISH
AND SKIES CLEAR UNDER THE HIGH AND EXPECTING LOW TEMPS FRIDAY NIGHT
TO BE IN THE TEENS...EXCEPT FOR AROUND 20 DOWNTOWN.  TEMPS COULD
CERTAINLY BE A BIT COOLER IF THE SURFACE IS ABLE TO DECOUPLE.  THE
WARM UP BEGINS SATURDAY WITH DRY CONDITIONS AND HIGHS IN THE 30S.
LOCATIONS ALONG AND WEST OF I-39 MAY REACH 40.

THE HIGH CONTINUES SOUTHEAST WITH THE NEXT LOW PASSING OVER SOUTHERN
ONTARIO SUNDAY.  AN UPPER LEVEL SHORTWAVE ALSO SCOOTS THROUGH THE
REGION SUNDAY AFTERNOON.  EXPECTING GUSTY SOUTHWEST WINDS SUNDAY
WITH MAX GUSTS ARND 35 MPH. AMPLE WAA WILL RESULT IN HIGH TEMPS IN
THE MID TO UPPER 40S. THE LOWS COLD FRONT SWINGS THROUGH SUNDAY
AFTERNOON AND EVENING WITH RAIN EXPECTED AHEAD OF AND ALONG THE
FRONT.  FORECAST SOUNDINGS DO NOT FEATURE ANY INSTABILITY...SO KEPT
THUNDERSTORMS OUT OF THE FORECAST.

THE MAJORITY OF COOLER AIR ASSOCIATED WITH THE LOW STAYS TO OUR
NORTH ALLOWING US TO REMAIN AT OR ABOVE NORMAL MONDAY WITH HIGHS IN
THE 50S. THE ECMWF FEATURES AN UPPER LEVEL WAVE WITH PRECIP MOVING
THROUGH MONDAY...BUT IT SEEMS TO BE AN OUTLIER SO KEPT RAIN OUT OF
THE FORECAST FOR EARLY NEXT WEEK.  AN UPPER LEVEL RIDGE MOVES
OVERHEAD TUESDAY LEADING TO HIGH TEMPS IN THE 60S.

JEE

&&

.AVIATION...

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

* LOW END MVFR CIGS THIS AFTERNOON...LIFTING SOME THIS EVENING.

* SOUTHWEST/WEST WINDS 12-15KT WITH GUSTS 20-22 KT. A FEW HIGHER
  GUSTS PSBL.

* POSSIBLE LGT RAIN SHOWER THIS EVENING MAINLY SOUTH OF KMDW.

* NW WINDS AT 320 DEGREES GREATER THAN 10 KT ON THURSDAY.

KMD

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

EXTENSIVE STRATUS ACROSS THE AREA AND UPSTREAM AS WELL. WE ARE
STARTING TO SEE SOME LIFTING IN IOWA EARLY THIS AFTERNOON WHERE A
WEAK SURFACE BOUNDARY EXISTS AND THE CLOUD LAYER FLOW IS OUT OF
THE NORTHWEST. IT LOOKS LIKE THE LOW END MVFR/IFR CONDITIONS WILL
STICK AROUND FOR A FEW MORE HOURS BEFORE SOME LIFTING OCCURS THIS
LATER THIS AFTERNOON AND MORE SO THIS EVENING. MODELS ARE
GENERALLY KEEPING PRECIPITATION SOUTH OF THE TERMINALS THIS
EVENING AND OVERNIGHT...THOUGH EXPECT THEM TO GET CLOSE TO A
KVYS...KJOT...TO KGYY LINE WITH LARGELY VIRGA FARTHER NORTH WHERE
THE LOW TO MID LEVEL AIR REMAINS RATHER DRY.

EXPECT WINDS TO VEER TO MORE WNW THIS EVENING...THEN NW BEHIND THE
COLD FRONT IN THE 8-10Z TIME FRAME...POSSIBLY BRIEFLY GUSTY BEHIND
THE FRONT. THEN EXPECT 10+ KT WINDS FROM THE NW THROUGH THE DAY.
SOME MVFR CLOUDS ARE POSSIBLE AGAIN IN THE MORNING BEHIND THE
FRONT.

KMD

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

* MEDIUM-HIGH CONFIDENCE IN WIND DIR/SPEED/GUSTS.

* MEDIUM-HIGH CONFIDENCE IN CIGS REMAIN AT OR ABOVE 1000 FT THIS
  AFTERNOON.

* MEDIUM CONFIDENCE IN CIGS LIFTING TO VFR SOMETIME THIS
  EVENING...THOUGH LOW CONFIDENCE ON TIMING.

* HIGH CONFIDENCE IN PRECIP REMAINING OUT OF TAF SITES THRU 02Z
  ...MEDIUM-HIGH CONFIDENCE PRECIP THIS EVENING WILL STAY SOUTH OF
  ORD...MEDIUM FOR MDW.

KMD

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

THURSDAY NIGHT...CHANCE OF SNOW SHOWERS. PATCHY MVFR CIGS AND
POSSIBLE VSBY REDUCTION.

FRIDAY...VFR.

SATURDAY...VFR.

SUNDAY...CHANCE RAIN THROUGH THE DAY...POSSIBLY MIXING WITH SNOW
EARLY. MVFR CIGS/VIS POSSIBLE.

MONDAY...VFR.

TUESDAY...VFR.

BEACHLER

&&

.MARINE...
228 PM CDT

MODERATE WEST TO SOUTHWEST WINDS ARE IN PLACE TODAY AHEAD OF AN
APPROACHING COLD FRONT WHICH WILL SWEEP ACROSS LAKE MICHIGAN
TONIGHT. WINDS TURN NORTHWEST THEN NORTH TOMORROW WITH 30 KTS
EXPECTED TO SPREAD DOWN THE LAKE BY TOMORROW EVENING. WINDS
GRADUALLY DIMINISH FRIDAY AND FRIDAY NIGHT AS HIGH PRESSURE BUILDS
OVER LAKE MICHIGAN BY SATURDAY MORNING...THEN WINDS TURN BACK TO THE
SOUTH/SOUTHWEST AGAIN BY LATER SATURDAY. ANOTHER COLD FRONT IS
PROGGED TO SWEEP ACROSS LAKE MICHIGAN SUNDAY NIGHT. A PERIOD OF
SOUTHWEST GALES APPEARS POSSIBLE AHEAD OF THE FRONT STARTING EARLY
SUNDAY MORNING...THEN NORTHWEST GALES ARE POSSIBLE BEHIND THE FRONT
SUNDAY NIGHT...EASING MONDAY MORNING.

BMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 4 PM WEDNESDAY.

&&

$$

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