Area Forecast Discussion
Issued by NWS Chicago, IL

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000
FXUS63 KLOT 262059
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
259 PM CST MON JAN 26 2015

.SHORT TERM...
258 PM CST

TONIGHT THROUGH TUESDAY...
WEAK CLIPPER HAS PRODUCED SOME LIGHT SNOW ACROSS NORTHERN IL THIS
AFTERNOON. LATEST RADAR IMAGERY SUGGESTS THE BACK EDGE OF THE
PRECIP BEGINNING TO WORK EAST ALONG I-39. WITH CONSIDERABLE DRY
AIR AT THE SFC...NOT ALL PRECIP HAS BEEN ABLE TO REACH THE SFC.
THE SLIGHTLY STEADIER SNOW WAS LOCATED ACROSS FAR NORTHEAST
IL...MAINLY OVER LAKE/MCHENRY COUNTIES. MOST HI-RES GUIDANCE
INDICATES THE LIFT/OMEGA WILL QUICKLY DISSIPATE ARND 00Z...WHICH
SUGGESTS WE MAY BE ABLE TO END THE LIGHT SNOW EARLIER. IT IS
POSSIBLE THAT WITH SOME WEAK LLVL CONVERGENCE THAT SOME
FLURRIES/LGT SNOW MAY LINGER TO 3Z...BUT THIS IS A LOW CONFIDENCE
SCENARIO. THE OTHER LINGERING CONCERN IS THE POSSIBILITY FOR
PATCHY FZDZ. WITH THE LACK OF GOOD SATURATION...THINK AT MOST THIS
WILL END UP AS A PATCHY FZDZ.

CLOUDS WILL LIKELY REMAIN LOCKED IN THRU THE OVERNIGHT
PERIOD...DESPITE THE CLEAR SKIES THIS AFTN ACROSS CENTRAL IOWA. THE
LACK OF MIXING WILL PERSIST THRU TUE MORNING...ANTI-CYCLONIC FLOW
WILL STEADILY MIX IN DRY AIR TUE MIDDAY. THIS MAY PROVIDE SOME
BREAKS IN THE CLOUD COVER BY EARLY AFTN. LLVL FLOW WILL TURN
NORTHEASTERLY...WHICH COULD HOLD TEMPS IN THE LOW 30S. IF CLOUDS CAN
THIN EARLIER IN THE DAY...TEMPS MAY BE ABLE TO WARM AN ADDTL DEGREE
OR TWO GIVEN THE LACK OF SNOW PACK.

SFC RIDGE WILL BE OVERHEAD TUE NGT...WITH DRY CONDS PERSISTING.
TEMPS SHUD EASILY RADIATE INTO THE MID-TEENS.

BEACHLER

&&

.LONG TERM...
258 PM CST

WEDNESDAY THROUGH MONDAY...
MID-LVL RIDGING WILL SLIDE EAST ACROSS THE CENTRAL PLAINS WED...WITH
A ROBUST MID-LVL THERMAL RIDGE OF 10 TO 14 DEG C LIFTING NORTHEAST
INTO A PORTION OF THE MID-MISSOURI VALLEY. THIS WILL LIKELY SET THE
STAGE FOR POTENTIALLY A MILD WED AFTN/EVE...AS TEMPS COULD WARM INTO
THE UPR 30S TO POSSIBLY THE LOW 40S ALONG THE SOUTHERN CWFA. LLVL
MOISTURE WILL BE SLOW TO ADVECT NORTH...HOWEVER GUIDANCE SUGGESTS
THAT AS THE BETTER MID-LVL VORT ARRIVES PRECIP SHIELD WILL INCREASE.
EQUALLY LATE WED NGT/EARLY THUR A DRY SLOT IS BEING PROGGED TO
DEVELOP. WITH THE LACK OF STRONG LLVL FORCING...IT IS POSSIBLE THAT
PARCELS REMAIN SMALL MORE IN THE FORM OF DRIZZLE. WILL MAINTAIN A
RAIN/SNOW MIX...BUT FEELING IS THAT ENOUGH WARM AIR WILL BE IN PLACE
TO PUSH THIS OVER TO LGT RAIN.

500MB PATTERN TRIES TO TRANSITION TOWARDS QUASI-ZONAL. THIS WILL
PROVIDE A RELATIVELY ACTIVE SETUP TOWARDS THE UPCOMING WEEKEND. THE
MID-WEEK SHORTWAVE WILL SLIDE EAST BY THUR NGT...WITH LIKELY A DRY
END TO THE WEEK. TEMPS WILL BE MILD AGAIN THUR...THE CHALLENGE IS
HOW WARM. CURRENT THINKING IS THAT WITH FROPA LIKELY IN THE MORNING
THUR THAT MAX TEMPS MAY OCCUR PRIOR TO DAYBREAK...MAINLY IN THE UPR
30S. POSSIBLY ARND 40 IN THE SOUTHERN CWFA. THEN WITH COLD AIR
ADVECTING IN FROM THE NORTHWEST...TEMPS WILL STEADILY COOL THUR AFTN
INTO THE LOW/MID 30S. DRY AIR MOVES IN THUR NGT WITH SFC RIDGING AND
SHUD REMAIN IN PLACE THRU MUCH OF FRI.

BEACHLER

&&

.AVIATION...

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

* SNOW THIS AFTERNOON WITH MVFR CONDITIONS AND TEMPO IFR...AND
  LIGHT ACCUMULATIONS LESS THAN AN INCH.
* SNOW TAPERING THIS EVENING AND POSSIBLY TRANSITIONING TO OR
  MIXING WITH DRIZZLE.

BMD

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

SHEARED UPPER LEVEL DISTURBANCE IS HELPING TO DRIVE AN AREA OF SNOW
ACROSS ILLINOIS AND WISCONSIN EARLY THIS AFTERNOON. THIS SNOW IS
EXPECTED TO MOVE INTO THE CHICAGO AREA OVER THE NEXT COUPLE HOURS.
INITIALLY DRY LOW/MID LEVELS WILL TAKE THEIR TIME TO SATURATE AS THE
RADAR RETURNS MOVE OVERHEAD...PRECIPITATION INITIALLY EVAPORATING IN
THE DRY AIR...BUT THEN EXPECT CONDITIONS TO DETERIORATE TO MVFR WITH
TEMPO IFR VSBY IN ANY MODERATE BURSTS OF SNOW. ACCUMULATIONS ARE
EXPECTED TO BE FAIRLY MINIMAL...A DUSTING TO AROUND HALF AN INCH OR
SO. PRECIPITATION SHOULD BEGIN TO TAPER LATE THIS AFTERNOON OR EARLY
THIS EVENING AS UPPER LEVEL RIDGING BEGINS TO BUILD OVERHEAD
SUPPRESSING THE DEEPER MOISTURE. ON THE OTHER HAND...PERSISTENT LOW
LEVEL CONVERGENCE NEAR THE SURFACE TROUGH MAY RESULT IN WEAK ASCENT
LATER INTO THE EVENING WHICH WOULD SUPPORT A FEW FLURRIES...OR
POSSIBLY DRIZZLE AT TIMES AS SOUNDINGS INDICATE LOSS OF ICE IN THE
COLUMN LATER THIS EVENING AS DRY AIR BUILDS DOWN IN THE UPPER LEVEL
SUBSIDENCE. SOUTH WINDS THIS AFTERNOON SHOULD BACK AROUND TO THE
NORTHEAST OVERNIGHT.

BMD

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

* MEDIUM CONFIDENCE IN VSBY/CIG TRENDS WITH PRECIP.
* MEDIUM-HIGH CONFIDENCE IN PREVAILING MVFR CIGS DEVELOPING THIS
  AFTERNOON.
* LOW CONFIDENCE IN END TIME OF PRECIP TONIGHT. LOW-MEDIUM
  CONFIDENCE THAT SNOW MAY CHANGE OR MIX WITH DRIZZLE AT SOME
  POINT LATE THIS EVENING.

BMD

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

TUESDAY NIGHT...MAINLY VFR.

WEDNESDAY...MAINLY VFR DURING THE DAY. CHANCE OF RAIN/SNOW AT
NIGHT WITH MVFR/IFR POSSIBLE.

THURSDAY...CHANCE OF LIGHT SNOW. MVFR LIKELY/IFR POSSIBLE.

FRIDAY...MAINLY VFR.

SATURDAY...CHANCE OF SNOW/MVFR CIGS.

SUNDAY...MVFR CIGS POSSIBLE.

RATZER

&&

.MARINE...
216 PM CST

LOW PRESSURE OVER THE UPPER MIDWEST WILL DROP SOUTH TOWARDS THE
TENNESSEE VALLEY TODAY AND TONIGHT...BUT WEAKENING WHILE DOING SO.
THIS WEAKENING TREND ALONG WITH HIGH PRESSURE BUILDING ACROSS THE
CENTRAL GREAT LAKES TONIGHT WILL HELP MAINTAIN OVERALL LIGHTER
WINDS IN PLACE. THIS WILL CONTINUE ON TUESDAY AND TUESDAY NIGHT AS
THE CENTER OF THE HIGH PASSES OVER THE LAKE. THIS HIGH WILL THEN
SHIFT TO THE EAST WEDNESDAY INTO WEDNESDAY NIGHT AS LOW PRESSURE
SHIFTS EAST THROUGH THE CENTRAL PLAINS. EXPECT SOUTHERLY WINDS TO
INCREASE OUT AHEAD OF THE LOW DURING THIS PERIOD...AND ESPECIALLY
WEDNESDAY NIGHT WHEN SPEEDS APPROACHING 30KT WILL BE OBSERVED.

RODRIGUEZ

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

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