Area Forecast Discussion
Issued by NWS Chicago, IL

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000
FXUS63 KLOT 281553
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
953 AM CST SUN DEC 28 2014

.SHORT TERM...
236 AM CST

THROUGH MONDAY...

HIGH PRESSURE NOSING IN FROM THE WEST RESULTING IN GRADUAL CLEARING
FROM WEST TO EAST EARLY THIS MORNING WITH THE BACK EDGE ALREADY
THOROUGH ROCKFORD. ONCE THE LOW CLOUDS CLEAR EXPECT SOME PASSING HIGH
CLOUDS THIS MORNING EMANATING FROM A MODEST UPPER LOW IN
TEXAS...OTHERWISE IT WILL BE A SEASONAL MOSTLY SUNNY DAY WITH
HIGHS TOPPING OUT IN THE LOW 30S OR SO. WE`LL HOLD A WEST WIND
WHICH WILL MAKE IT FEEL A LITTLE COOLER...THOUGH TODAY LOOKS TO BE
THE WARMEST FOR THE REST OF 2014. ARCTIC HIGH PRESSURE CONTINUES
TO SINK INTO THE CENTER OF THE COUNTRY TONIGHT. LOCALLY...OUR
WINDS TURN NORTHERLY ALLOWING SOME OF THIS CONTINUE MOVING IN.
ZONAL FLOW ALOFT WILL KEEP SOME HIGHER CLOUDS PUSHING INTO THE
REGION PREVENTING A REAL COLD NIGHT...BUT STILL THE COLDEST WE/VE
SEEN IN A WHILE WITH LOWS INTO THE 20S.

BY MONDAY MORNING...A BACKDOOR FRONT MOVING DOWN THE LAKE WILL
CONTINUE THE STREAM OF COLDER AIR. ADDITIONALLY LAKE EFFECT CLOUDS
WILL MOVE INTO NORTHWEST INDIANA AND PORTIONS OF NORTHEAST ILLINOIS.
WITH THE CONTINUED COLD ADVECTION AND MIX OF LOW AND MID
CLOUD...TEMPS WILL STRUGGLE TO GET TO FREEZING IN MANY SPOTS. NAM IS
STILL HINTING AT SOME LAKE EFFECT FLURRIES OR LIGHT SNOW SHOWERS THOUGH
LAKE EFFECT PARAMETERS DURING THE DAY ARE NOT SUPER IMPRESSIVE.

KMD

&&

.LONG TERM...
236 AM CST

MONDAY NIGHT THROUGH SATURDAY...

MONDAY NIGHT...A MORE SIGNIFICANT SURGE OF COLD AIR COMES STREAMING IN.
THIS WILL ENHANCE LAKE EFFECT PARAMETERS...ESPECIALLY IN NORTHWEST
INDIANA AND PORTIONS OF SOUTHERN COOK COUNTY. EQUILIBRIUM LEVELS ARE
NOT MUCH BETTER THAN DURING THE DAY MONDAY...BUT LOW LEVEL LAPSE
RATES/LAKE INDUCED CAPE ARE SLIGHTLY BETTER TO SUPPORT SOME LIGHT
ACCUMULATIONS...ESPECIALLY AFTER MIDNIGHT IN NW INDIANA.

AS THE ARCTIC HIGH CONTINUES SOUTH INTO THE PLAINS...WINDS WILL BACK
TO NW AND PUSH LAKE EFFECT SNOWS EASTWARD. 850 TEMPS IN THE MINUS
TEENS SUPPORT HIGHS ONLY IN THE UPPER TEENS TO LOW 20S IN SPITE OF
SOME CLEARING THROUGH THE DAY.

TUESDAY NIGHT/WEDNESDAY MORNING FEATURE THE COLDEST AIR MASS. NW
FLOW PERSISTS WITH MIGRATORY SHORTWAVE ENERGY. WINDS WILL BACK TO
THE WSW THROUGH THE DAY. GIVEN THE COLD START...EXPECT HIGHS SIMILAR
TO TUESDAY AND POSSIBLY A BIT COOLER WITH 20 BEING A STRETCH IN
PLACES.

BY THURSDAY THE UPPER FLOW PATTERN WILL MODIFY AS THE DEEP COLD
TROUGH EXTENDING FROM NORTHERN ONTARIO BACK SOUTHWEST TO THE PACIFIC
GETS PINCHED OFF IN THE NORTH AND SHIFTS EAST OUR FOCUS THEN SHIFTS
TO A CUT OFF LOW OVER CALIFORNIA. SOUTHERLY FLOW AHEAD OF THIS
SYSTEM WILL TRANSPORT SOME SLIGHTLY WARMER AIR ALONG WITH ADDITIONAL
GULF MOISTURE. MEANWHILE...THE SHORTWAVE ENERGY WILL CONTINUE TO
ROTATE SOUTH AND WEST AROUND THE ARCTIC VORTEX THAT AT THIS POINT
SETS UP NORTH OF HUDSON BAY. THE CALI LOW WILL EVENTUALLY EJECT EAST
AND NORTH FRIDAY INTO SATURDAY. THE CLASH OF THE WARMER GULF AIR AND
ARCTIC AIR ENTRENCHED OVER THE REGION LOOKS TO RESULT IN A DYNAMIC
WINTER STORM SYSTEM. PRECIP TYPE WILL BE AN ISSUE SOMEWHERE IN THE
REGION AHEAD OF THE LOW...WITH AN IMPRESSIVE DEFORMATION SNOW BAND
EXPECTING TO SET UP BEHIND IT DUE TO A REPLENISHMENT OF COLD AIR AND
STRONG BAROCLINIC ZONE. A LOT HINGES ON THE INTERACTION WITH THE
NORTHERN STREAM AS TO WHERE THIS SYSTEM HEADS...BUT MODELS TO THIS
POINT HAVE BEEN SOMEWHAT CONSISTENT ON THE TIME FRAME OF CONCERN BEING
LATER FRIDAY AND ESPECIALLY INTO SATURDAY WITH SOME WINTRY
PRECIPITATION SOMEWHERE IN OUR AREA. COLD AIR COMES RIGHT BACK IN
BEHIND IT.

KMD

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 16Z...

* LAKE EFFECT CLOUDS/FLURRIES POSSIBLE MONDAY MORNING.

JEE

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

VFR WITH LIGHT WINDS THROUGH TONIGHT. SUBTLE FRONT MOVES ACROSS
AREA LATE TONIGHT AND ALLOWS WINDS TO TURN IN OFF THE LAKE WHICH
SHOULD BRING SOME MVFR CIGS AND PROBABLY SOME FLURRIES INTO NE
ILLINOIS MONDAY MORNING.

IZZI

//ORD AND MDW CONFIDENCE...UPDATED 16Z...

* LOW-MEDIUM CONFIDENCE IN LAKE EFFECT CLOUDS/FLURRIES.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

JEE

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

MONDAY NIGHT...MVFR CIGS/LAKE EFFECT SNOW SHOWERS POSSIBLE.

TUESDAY THROUGH FRIDAY...SLIGHT CHANCE OF MVFR CIGS AT TIMES
OTHERWISE VFR.

FRIDAY NIGHT AND SATURDAY...CHANCE OF SNOW AND IFR.

IZZI

&&

.MARINE...
150 AM CST

MODERATE NORTHWEST WINDS WILL EASE SOME TODAY AND THEN VEER MORE
NORTHERLY TONIGHT INTO MONDAY. NORTHERLY WINDS WILL FRESHEN UP
MONDAY NIGHT INTO TUESDAY AS ARCTIC AIR SPILLS INTO THE REGION.
WINDS WILL BACK TO SOUTHWEST AND INCREASE FURTHER TO GALES WEDNESDAY
AND CONTINUE THROUGH THURSDAY MORNING AND STRONG LOW PRESSURE MOVES
SOUTH INTO HUDSON BAY TIGHTENING UP THE PRESSURE GRADIENT WITH
ARCTIC AIR FIRMLY ENTRENCHED OVER THE AREA. WINDS LOOK TO SUBSIDE
LATER THURSDAY INTO EARLY FRIDAY BEFORE POTENTIALLY RAMPING UP AGAIN
NEXT WEEKEND AS ANOTHER STORM SYSTEM POTENTIALLY APPROACHES THE
REGION THOUGH SIGNIFICANT MODEL DIFFERENCES EXIST IN TRACK AND
INTENSITY OF THAT SYSTEM.

IZZI

&&

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

$$

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