Area Forecast Discussion
Issued by NWS Chicago, IL

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666
FXUS63 KLOT 110924
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
324 AM CST THU FEB 11 2016

.SHORT TERM...
315 AM CST

THROUGH FRIDAY MORNING...

THE FORECAST MESSAGE CONTINUES WITH UNSEASONABLE COLD AS THE
EMPHASIS...IN PARTICULAR FRIDAY NIGHT THROUGH SATURDAY EVENING.
AT THIS TIME IT APPEARS A WIND CHILL ADVISORY WILL BE NEEDED FOR
PART OF FRIDAY NIGHT AND SATURDAY MORNING. AS FOR
PRECIPITATION...LATE TONIGHT AND FRIDAY MORNING WILL LIKELY HAVE A
LITTLE LIGHT SNOW/FLURRIES ALTHOUGH IMPACTS SHOULD BE MINIMAL.
LAKE EFFECT SNOW SHOWERS FOR PORTER COUNTY INDIANA LOOK TO PICK UP
AGAIN FRIDAY NIGHT AND SATURDAY MORNING WITH MINOR ACCUMULATION
PROBABLE AND A CHANCE FOR BRIEF HEAVIER RATES. FINALLY...THE
CONFIDENCE HAS INCREASED ON A MORE BROAD SNOW EVENT IN THE GENERAL
UPPER MISSISSIPPI VALLEY/WESTERN GREAT LAKES REGION ON SUNDAY.

SURFACE RIDGING IS OVER THE AREA THIS MORNING EMANATING FROM A
MODIFIED 1029MB ARCTIC HIGH OVER MINNESOTA. EARLY MORNING
TEMPERATURES ARE IN THE SINGLE DIGITS. THE NORTHWEST SURFACE FLOW
CONTINUES TO GENERATE MAINLY LIGHT LAKE EFFECT SNOW
SHOWERS/FLURRIES FOR NORTHEAST PORTER COUNTY AND EXPECT THAT TO
CONTINUE THIS MORNING BEFORE FINALLY TEMPORARILY SHUTTING DOWN.
SOME HIGH CLOUDS WILL LIKELY THICKEN LATER ACROSS MAINLY NORTH
CENTRAL ILLINOIS TODAY BUT OTHERWISE MUCH OF THE AREA SHOULD SEE
MORE SUN. THE SUN AND FAR LESS COLD ADVECTION SHOULD YIELD HIGHS
FOUR TO FIVE DEGREES ABOVE YESTERDAYS.

THE UNSETTLED AND ACTIVE NORTHWEST FLOW PATTERN CONTINUES WITH A
140KT JET PUSHING INTO THE NORTHERN PLAINS BY THIS EVENING
USHERING A LOW AMPLITUDE SHEARED SHORT WAVE INTO THE MID-
MISSISSIPPI VALLEY BY DAYBREAK FRIDAY. A FAIRLY LARGE DISPARITY
IN GUIDANCE EXISTS WITH THIS PROBABLY BECAUSE IT IS SO LOW
AMPLITUDE. FEEL THE EC IS JUST TOO FAR SOUTH AND THE NAM PROBABLY
TOO FAR NORTH BASED ON WHERE THE BAROCLINIC ZONE IS NOW...SO
PREFERRING A MIDDLE ROUTE CLOSE TO THE GEM WHICH SEEMS TO OFTEN
HANDLE THESE LITTLE CLIPPERS FAIRLY WELL. THE SATURATION ACROSS
THE CWA IS AT A GOOD THERMAL PROFILE TO RATTLE OUT AT LEAST
FLURRIES ALL THE WAY UP TO THE WI STATE LINE...BUT THINK THE BEST
CHANCES FOR LIGHT ACCUMULATION OF ONE HALF INCH PLUS ARE MAINLY
ALONG/SOUTH OF I-80. COULD SEE UP TO ONE INCH IN SOME PARTS OF THE
SOUTH. THE TIMING WOULD INTERSECT THE MORNING COMMUTE SO SOME
MINIMAL IMPACTS POSSIBLE...MAINLY SOUTH. THE HIGHS ON FRIDAY
SHOULD BE SIMILAR TO TODAY DESPITE A WARMER AIR MASS...AND MAY BE
REACHED PRIOR TO NOON BEFORE THE COLD SURGE ARRIVES.

MTF

&&

.LONG TERM...
315 AM CST

FRIDAY AFTERNOON THROUGH THURSDAY...

A LOBE OF THE SEMI-PERMANENT POLAR VORTEX WILL DROP INTO EASTERN
CANADA WITH 500MB HEIGHTS DOWN TO SUB 490DM IN QUEBEC BY FRIDAY
NIGHT. AN ASSOCIATED ARCTIC COLD FRONT PUSHES ACROSS THE AREA
DURING FRIDAY AFTERNOON WITH FALLING TEMPERATURES WHICH ARE
LIKELY TO TUMBLE RAPIDLY FRIDAY EVENING WITH SOME PLACES NEAR
ZERO BY MIDNIGHT /WHICH IS QUITE IMPRESSIVE WITH NO REAL SNOW
COVER/. FORECASTED WINDS GUSTING TO 30 MPH WILL ASSIST IN
STEERING WIND CHILLS DOWN TO 10 TO 25 BELOW ZERO LIKELY PROMPTING
A WIND CHILL ADVISORY FOR AT LEAST PART OF THE AREA INTO SATURDAY
MORNING.

THE DEEP COLD ADVECTION REGIME SUPPORTS A QUICK UPTICK IN LAKE
EFFECT SNOW INTO LOWER MICHIGAN AND WHAT STILL SEEMS PART OF
NORTHWEST INDIANA FRIDAY NIGHT INTO SATURDAY. THE MOST FAVORED
DURATION AND GENERAL CONFLUENCE APPEARS POINTED TOWARD FAR SW MI.
SO PORTER COUNTY MAY DODGE THE HEAVIEST RATES BUT STILL BEING 48
HOURS OUT OR SO...TOUGH TO PIN DOWN FOR CERTAIN. CONTINUE WITH
FAIRLY HIGHS POPS AND LIGHT SNOW AMOUNTS FOR NORTHERN PORTER
COUNTY...ALTHOUGH SOME SNOW COULD EXTEND WILL INLAND TO NORTHERN
JASPER COUNTY.

AFTER A COLD SATURDAY WITH MOST COMMUNITIES STRUGGLING TO REACH
DOUBLE DIGITS...ATTENTION THEN TURNS TO AN END OF THE WEEKEND
SYSTEM. THIS CLIPPER SYSTEM...WHICH IS PROJECTED TO PHASE WITH
SOME PACIFIC ENERGY OVER THE UPPER MISSISSIPPI VALLEY LATE
SATURDAY NIGHT/SUNDAY MORNING...HAS BEEN FAIRLY CONSISTENTLY
FORECAST BY THE GFS. THE 11.00 EC DID COME MORE IN LINE WITH
ITS NCEP COUNTERPART REGARDING THE SYSTEMS SOUTHERN REACH AND
ORIENTATION/DEPTH...WHILE THE GEM REMAINS MORE UNPHASED AND
PRODUCES LITTLE QPF. FEEL ENOUGH SIGNAL IS THERE WITH THE GFS AND
EC AND THEIR ENSEMBLES TO INCREASE POPS WITH AT LEAST LIKELY LIGHT
SNOW FOR NORTH CENTRAL ILLINOIS AND INCREASED CHANCES EASTWARD. A
SLIGHT NEGATIVE TILT AND DEEPENING OF THE SHORT WAVE IS PROJECTED
EASTWARD DURING SUNDAY THAT WOULD FAVOR DEEPER WARM ADVECTION
ASCENT AND TIGHTENED BAROCLINIC ZONE OVER/NEAR PART OF THE
FORECAST AREA. MOISTURE RETURN IS LIMITED WITHIN THIS NORTHWEST TO
LIKELY PREVENT TOO HIGH OF A QPF EVENT...YET A POTENTIALLY DEEP
DENDRITIC ZONE AND HIGHER RATIOS COULD STILL SUPPORT A SEVERAL
INCH SNOWFALL EVENT. GIVEN THE CORE OF THIS SYSTEM ENERGY STILL
BEING OVER THE NORTH PACIFIC THERE IS POTENTIAL FOR LARGE SHIFTS
IN INTENSITY AND SPEED OF THIS SYSTEM AND MAYBE EVEN TRACK.

MTF

&&

.AVIATION...
FOR THE 06Z TAFS...

NO SIG CHANGES TO THE GOING FORECAST. FAIRLY QUIET FOR THE AREA
TERMINALS THROUGH TOMORROW NIGHT. CLOUD COVER WILL MAINLY BE SCT-
BKN CI ASSOCIATED WITH A STRONG UPPER JET DIVING THROUGH THE
MIDDLE MISSISSIPPI VALLEY. SFC HIGH PRESSURE EXTENDS FROM CNTRL
CANADA TO THE CENTRAL GULF COAST. THE CENTER OF THE HIGH WILL
SLIDE SOUTH OVERNIGHT AND TOMORROW...GENERALLY ALONG THE
MISSISSIPPI RIVER. THIS SHOULD KEEP WINDS GENERALLY NWLY...THOUGH
DECREASING OVERNIGHT AND TOMORROW TO ARND 5KT AS THE PRESSURE
GRADIENT WEAKENS ACROSS THE AREA. AS THE HIGH CONTINUES TO SLIDE
SOUTHEAST INTO THE OHIO VALLEY TOMORROW EVENING...WINDS SHOULD
BACK TO SWLY WHILE REMAINING ARND 5KT.

KREIN

&&

.MARINE...
245 AM CST

NO CHANGES WERE MADE TO THE CURRENT SMALL CRAFT ADVISORIES. HOISTED
A GALE WATCH FOR THE OPEN WATERS LATE FRIDAY AFTERNOON THROUGH EARLY
SATURDAY MORNING. WILL LIKELY ALSO NEED A SMALL CRAFT ADVISORY AND
FREEZING SPRAY HEADLINE FOR THAT TIME PERIOD.

HIGH PRESSURE DRIFTS OVER THE OHIO VALLEY TODAY LEADING TO
DIMINISHING WINDS THAT BACK TO THE WEST.  A WEAK LOW FORMS OVER
SOUTHEAST ONTARIO THURSDAY NIGHT AND DRAGS A COLD FRONT DOWN THE
LAKE FRIDAY. AT THE SAME TIME A LARGE HIGH WILL BUILD OVER THE
PLAINS. AS SUCH...WINDS BECOME NORTHWEST AND INCREASE TO GALE
FORCE...POSSIBLY UP TO 40 KT...LATE FRIDAY AFTERNOON INTO EARLY
SATURDAY MORNING. THE PUSH OF COLD AIR AND STRONG WINDS WILL LIKELY
LEAD TO ACCUMULATING FREEZING SPRAY. A FREEZING SPRAY WARNING WILL
LIKELY BE NEEDED.  WINDS DIMINISH AND BACK SATURDAY AS THE HIGH
BUILDS OVER THE WESTERN GREAT LAKES.  THE HIGH CONTINUES EAST
REACHING THE EAST COAST SUNDAY NIGHT. WINDS BECOME SOUTH TO 25 KT
BEHIND THE HIGH. A WEAK LOW PASSES OVER THE LAKE EARLY NEXT WEEK
FOLLOWED BY ANOTHER SURFACE HIGH.

JEE

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...INDIANA NEARSHORE WATERS UNTIL 3 PM THURSDAY.

     SMALL CRAFT ADVISORY...ILLINOIS NEARSHORE WATERS UNTIL 9 AM THURSDAY.

     GALE WATCH...LMZ777-LMZ779...3 PM FRIDAY TO 6 AM SATURDAY.

&&

$$

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