Area Forecast Discussion
Issued by NWS Chicago, IL

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000
FXUS63 KLOT 260310
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
910 PM CST SUN JAN 25 2015

.UPDATE...
820 PM CST

PCPN IS WINDING DOWN ACROSS THE AREA WITH ONLY SOME LINGERING
LIGHT SNOW SOUTH OF THE KANKAKEE RIVER. WHILE WINDS ARE CURRENTLY
STILL RATHER BREEZY ACROSS THE AREA...THE GENERAL TREND OF THE
REMAINDER OF THE EVENING AND OVERNIGHT SHOULD BE FOR WINDS TO
DIMINISH AND ANY LINGERING SNOW SHOULD PUSH OUT OF THE AREA.
TEMPERATURES SHOULD ALSO DROP OFF WITH PARTIALLY CLEARING SKIES
AND SOME COOLER AIR FILTERING IN AS THE LOW PRESSURE CENTER
ASSOCIATED WITH THE SYSTEM THAT BROUGHT TODAY`S PRECIPITATION
MOVES OFF TO THE SOUTHEAST.

HAVE MADE SOME CHANGES TO THE GOING FORECAST FOR TOMORROW. THE
LATEST 00Z MODEL RUNS ARE TRENDING TOWARD THE NEXT CLIPPER
DROPPING A LITTLE FARTHER SOUTH...WITH SOME MODEST LIFT IN THE
ZONE AHEAD OF A WEAK WARM FRONT ASSOCIATED WITH THE NEXT CLIPPER.
SO HAVE INCREASED POPS...WITH LIKELY POPS FOR THE AFTERNOON HOURS
ACROSS MUCH OF THE AREA...WITH THE EXCEPTION OF THE FAR SOUTHERN
PORTIONS OF THE CWA. ALSO...THE THERMAL PROFILES IN THE LATEST
MODEL SOUNDINGS SUGGEST THAT THE PCPN SHOULD BE ALL SNOW...WITH A
DEEP ENOUGH SATURATED LAYER TO SUPPORT ALL SNOW...AND LESSER
CHANCES FOR FREEZING DRIZZLE. SO...HAVE REMOVED THE FREEZING
DRIZZLE MENTION FOR THE DAYTIME HOURS. STILL FEEL THAT THERE IS A
BETTER CHANCE FOR FREEZING DRIZZLE TOMORROW NIGHT AS DRIER AIR
ALOFT LOWERS THE DEPTH OF THE SATURATED LAYER ENOUGH TO MINIMIZE
THE CHANCE FOR ICE PRODUCTION IN THE SATURATED LAYER. WHILE POPS
HAVE BEEN RAISED...THERE IS LITTLE AVAILABLE DEEP LAYER
MOISTURE...SO ACTUAL SNOWFALL AMOUNTS SHOULD BE LIGHT...ONLY
PERHAPS A COUPLE TENTHS OF AN INCH OF ACCUMULATION.

KREIN

&&

.SHORT TERM...
206 PM CST

TONIGHT THROUGH MONDAY NIGHT...

COOL AIR HAS STRUGGLED TO SLIDE SOUTH THIS AFTERNOON...HOWEVER TEMPS
ARE BEGINNING TO FALL INTO THE UPR 20S ACROSS FAR NORTHEAST IL.
ACROSS THE CENTRAL/SOUTHERN CWFA TEMPS REMAIN IN THE LOW 30S WITH
DEW POINT DEPRESSIONS NOT MUCH MORE THAN 1 TO 2 DEGREES. NORTH OF
I-80 PRECIP IS MAINLY FLURRIES...WITH A RAIN/SNOW MIX SLOWLY
CHANGING TO ALL SNOW LATER THIS AFTERNOON ACROSS THE SOUTHERN CWFA.
THE SHORTWAVE THAT BROUGHT THE LIGHT SNOW CONTINUES TO SLIDE EAST
ACROSS SOUTHERN IL...AND WILL STEADILY BRING AN END TO THE PRECIP
ACROSS THE FORECAST AREA THIS EVENING FROM NORTHWEST TO SOUTHEAST.
WINDS WILL GRADUALLY DIMINISH AS WELL AS THE PRESSURE GRADIENT
RELAXES.

SFC RIDGE CENTERED TO THE NORTH THIS AFTERNOON...WILL SAG SOUTH AND
EXPAND TO COVER A PORTION OF THE WESTERN GREAT LAKES/MISSOURI VALLEY
OVERNIGHT. WHILE SOME EROSION TO THE CLOUDS IS PROBABLE NORTH OF THE
FORECAST AREA...EXPECT SOME DECREASE IN CLOUDS CLOSER TO DAYBREAK
MON. CURRENTLY EXPECT OVERNIGHT LOWS TO DIP INTO THE MID/UPR
TEENS...HOWEVER THIS WILL LIKELY NOT OCCUR UNTIL CLOSER TO DAYBREAK
MON.

THE BRIEF BREAK IN CLOUDS MON MORNING WILL QUICKLY GIVE WAY TO THE
NEXT CLIPPER SYSTEM ARRIVING MON AFTN/EVE. GUIDANCE HAS MAINTAINED A
PROGRESSIVE LOOK TO THIS NEXT WAVE...HOWEVER OPERATIONAL SOLUTIONS
ARE EQUALLY BULLISH ON EROSION OF MOISTURE WITHIN THE LOWEST FEW
LAYERS OF THE ATMOS LATE MON NGT. HAVE SOME CONCERN ABOUT P-TYPE MON
AFTN/EVE. AT THE ONSET MOISTURE WILL QUICKLY SATURATE THRU THE -10
DEG C LAYER AND TOUCH THE FAVORED DGZ...HOWEVER THE DEPTH OF THE
MOISTURE BECOMES MORE SHALLOW MON EVE. ALONG WITH THE LACK OF GOOD
LIFT AND SHALLOW MOISTURE...IT IS LOOKING MORE LIKELY THAT PRECIP
MAY BE A MIX OF FREEZING DRIZZLE/LGT-SNOW.

A WEAK THERMAL RIDGE TRIES TO PUSH OVERHEAD MON AFTN...AS LLVL FLOW
TURNS SOUTHWESTERLY. TEMPS SHUD HOVER ARND FREEZING...HOWEVER THIS
WILL HINGE ON CLOUD COVER ARRIVAL AND DEVELOPMENT OF PRECIP. IF THIS
IS DELAYED...TEMPS COULD PUSH A FEW DEGREES WARMER MON EARLY AFTN.

HEIGHTS SLOWLY INCREASE MON NGT...WITH THE MOISTURE PEELING EAST
ALONG WITH THE WEAKENING SHORTWAVE. AT THIS TIME HAVE MAINTAINED A
MENTION OF LGT SNOW OR PATCHY FREEZING DRIZZLE MON NGT...BUT COULD
END UP WITH A DRY PERIOD.

BEACHLER

&&

.LONG TERM...
206 PM CST

TUESDAY THROUGH SUNDAY...
TOWARDS THE MIDDLE OF THE WEEK ENSEMBLES MAINTAIN A HIGH CONFIDENCE
IN THE TROUGH ALONG THE SOUTHEAST CONUS WEAKENING WITH RIDGING
EXPANDING EAST ACROSS THE CENTRAL PLAINS. THIS SHUD PLACE THE BULK
OF THE REGION INTO A WEAK SFC RIDGE TUE/WED. WED AFTN THE SFC RIDGE
QUICKLY SLIDES SOUTHEAST...WHICH COULD ALLOW SOME WARM AIR TO ADVECT
NORTHEAST INTO THE CWFA AND PUSH SFC TEMPS CLOSE TO 40 DEG.

WITH A QUASI-ZONAL SETUP WED NGT/THUR...GUIDANCE SUGGESTS A ROBUST
MID-LVL VORT WILL QUICKLY SLIDE EAST FROM THE ROCKIES TOWARDS THE
PLAINS WED EVE. GUIDANCE THEN FURTHER STRENGTHENS THIS WAVE AND
LIFTS NORTHEAST ACROSS THE FORECAST AREA THUR. SOUNDINGS SUGGESTS
THAT PRECIP COULD START AS MAINLY RAIN WITH THIS SYSTEM...THEN
DYNAMICALLY COOL OVERNIGHT INTO THUR AND TRANSITION PRECIP OVER TO
LGT SNOW.

A RELATIVELY ACTIVE PATTERN CONTINUES TOWARDS THE END OF THE WEEK
INTO EARLY NEXT WEEKEND...WITH TEMPS GENERALLY IN THE UPR 20S/LOW
30S.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 03Z...

* LIGHT SNOW POSSIBLE MONDAY AFTERNOON/EVENING

IZZI

//DISCUSSION...UPDATED 00Z...

SYSTEM RESPONSIBLE FOR TODAY`S WEATHER IS QUICKLY MOVING AWAY AND
ANTICIPATE WINDS TO QUICKLY SUBSIDE THIS EVENING AND SKIES TO
CLEAR OUT. MID-HIGH LEVEL CLOUDINESS WILL ARRIVE LATER TONIGHT IN
ADVANCE OF THE NEXT FAST MOVING WEAK SYSTEM SLATED TO AFFECT THE
AREA MONDAY AFTERNOON AND EVENING. STILL LOOKS LIKE A SEVERAL HOUR
PERIOD OF LIGHT SNOW COULD OCCUR MONDAY AFTERNOON AND
EVENING...BUT AMOUNTS WOULD BE LIGHT AND CONFIDENCE NOT TERRIBLY
HIGH SO HAVE JUST MAINTAINED PROB30 FOR NOW. GUIDANCE CONTINUES TO
APPEAR OVERLY PESSIMISTIC WITH RESPECT TO LOW CLOUD DEVELOPMENT
MONDAY AND HAVE LEANED TOWARD THE RECENTLY MORE SUPERIORLY
PERFORMING MAV GUIDANCE WITH JUST SOME MVFR CIGS IN THE AFTERNOON.
LIGHT WINDS OVERNIGHT INTO MONDAY MORNING WILL TREND MORE LIGHT
SOUTH TO SOUTHEAST MONDAY AFTERNOON AND EVENING.

IZZI

//ORD AND MDW CONFIDENCE...UPDATED 03Z...

* MEDIUM CONFIDENCE IN TIMING AND LOW CONFIDENCE IN OCCURRENCE OF
  LIGHT SNOW MONDAY
* HIGH CONFIDENCE IN REMAINING FORECAST ELEMENTS

IZZI

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

TUESDAY...MVFR CIGS POSSIBLE.

WEDNESDAY...VFR DURING THE DAY THEN CHANCE OF -RASN AND MVFR/IFR
AT NIGHT.

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

FRIDAY...CHANCE OF MVFR CIGS...ESPECIALLY EARLY.

SATURDAY...CHANCE OF LIGHT SNOW/MVFR CIGS.

IZZI

&&

.MARINE...
131 PM CST

A QUICK MOVING CLIPPER SYSTEM...CURRENTLY CENTERED ACROSS SOUTHERN
ILLINOIS...WILL RAPIDLY SHIFT EASTWARD TOWARDS THE ATLANTIC COAST
BY MONDAY MORNING. NORTHEASTERLY WINDS OF 30-35 KT CONTINUE ACROSS
THE SOUTHERN 1/3RD OF LAKE MICHIGAN...AND THESE WINDS LOOK TO
CONTINUE FOR THE NEXT FEW HOURS...BEFORE A DIMINISHING TREND BEGINS
EARLY THIS EVENING. ANOTHER WEAKENING LOW WILL SHIFT SOUTHWARD JUST
WEST OF THE LAKE LATE MONDAY AND MONDAY NIGHT. THIS WILL RESULT IN A
PERIOD OF SOUTHERLY WINDS OVER THE LAKE DURING THIS PERIOD. LATER IN
THE WEEK ANOTHER LOW IS EXPECTED TO IMPACT THE GREAT LAKES REGION.
THIS SYSTEM STILL HAS THE POTENTIAL TO PRODUCE A PERIOD OF STRONG
SOUTHERLY WINDS LATE WEDNESDAY AND WEDNESDAY NIGHT...FOLLOWED BY A
PERIOD OF STRONG NORTHERLY WINDS THURSDAY INTO EARLY FRIDAY.

KJB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 9 AM MONDAY.

&&

$$

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