Area Forecast Discussion
Issued by NWS Chicago, IL

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

000
FXUS63 KLOT 282337
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
537 PM CST SUN DEC 28 2014

.SHORT TERM...
346 PM CST

REMAINDER OF THIS AFTERNOON AND TONIGHT...

QUIET WEATHER WILL CONTINUE THROUGH THE REMAINDER OF THIS AFTERNOON
AND TONIGHT WITH CLEAR SKIES OVER MUCH OF THE CWA.  THE ONLY CLOUD
COVER OF SIGNIFICANT IS A LAYER OF DENSE CIRRUS OVER NWRN INDIANA
AND EAST-CENTRAL IL ASSOCIATED WITH THE SUBTROPICAL JET STREAM
EXTENDING FROM THE WRN GLFMEX THROUGH NEW ENGLAND.  AS SFC HIGH
PRESSURE CONTINUES TO SPREAD SOUTHEAST TOWARD THE OHIO VALLEY...ALL
CLOUD COVER SHOULD MOVE OUT OF THE AREA AND CLEAR SKIES SHOULD
PREVAIL ACROSS THE REGION TONIGHT.  THE AMPLE SUNSHINE HAS SLIGHTLY
COUNTERED THE PERSISTENT COLD ADVECTION ACROSS THE REGION...ALLOWING
TEMPERATURES TO TOP OUT IN THE LOWER 30S THIS AFTERNOON.  WHILE
WINDS ARE EXPECTED TO DROP OFF OVERNIGHT WITH THE BUILDING HIGH
PRESSURE...DIRECTION SHOULD VEER A BIT MORE NELY...SETTING UP A
FETCH OFF OF LAKE MICHIGAN...SO SFC DEWPOINTS SHOULD REMAIN IN THE
UPPER TEENS TO LOWER 20S...WITH THE VERY DRY AIR CURRENTLY OVER THE
UPPER MISSISSIPPI VALLEY WITH SFC DEWPOINTS IN THE SINGLE DIGITS
ABOVE 0F TO THE SINGLE DIGITS BELOW 0F REMAINING TO THE NORTH AND
WEST OF THE CWA...LIMITING THE RADIATIVE COOLING.  SO...ONLY EXPECT
THAT TEMPS SHOULD DROP INTO THE LOWER TO MIDDLE 20S ACROSS THE
AREA...WITH UPPER 20S TEMPS NEAR THE LAKE.

KREIN

&&

.LONG TERM...
346 PM CST

MONDAY THROUGH SUNDAY...

THE NEXT WEATHER OF CONCERN WILL BE THE CHANCES FOR LAKE EFFECT SNOW
ACROSS NERN IL AND NWRN IN.  AS THE SFC HIGH BUILDS ACROSS THE
REGION...LOW LEVEL WINDS WILL INITIALLY BE NELY MONDAY MORNING.
MODEL SOUNDINGS INDICATE AT LEAST SOME WEAK INSTABILITY OVER THE SRN
END OF THE LAKE...WHICH WOULD BE CONDUCIVE TO LAKE EFFECT SNOW
SPREADING INLAND BEGINNING EARLY MONDAY MORNING.  LOW LEVEL FLOW
WILL GRADUALLY BACK FROM NELY...THROUGH NLY MONDAY NIGHT AND THEN
NWLY BY TUESDAY MORNING.  EQUILIBRIUM HEIGHTS THROUGH THE PERIOD
WILL RANGE FROM ARND 4KFT-6KT WITH LAKE INDUCED CAPE OF ARND
300-400J/KG...SO SOME LAKE EFFECT SNOW WILL BE LIKELY...BUT
ANTICIPATE THAT THE GREATEST CHANCES FOR ACCUMULATING SNOW WILL BE
RELATIVELY CLOSE TO THE LAKE...WITH ONLY SCT -SHSN OR FLURRIES
FARTHER INLAND INTO THE CHICAGO METRO AREA.  ALSO...WITH LOW LEVEL
FLOW SLOWLY...BUT CONTINUOUSLY BACKING FROM NELY TO NWLY FROM MONDAY
MORNING THROUGH TUESDAY MORNING...DO NOT ANTICIPATE THAT ANY SINGLE
LAKE PLUME...SHOULD ONE DEVELOP...TO REMAIN OVER ANY GIVEN AREA FOR
A SIGNIFICANT AMOUNT OF TIME...SO WOULD ANTICIPATE THAT ANY
ACCUMULATIONS WOULD BE BELOW ADVISORY CRITERIA.  LATEST INDICATORS
SUGGEST THAT THE COOK COUNTY LAKEFRONT...INCLUDING DOWNTOWN CHICAGO
COULD SEE 1 TO 3 INCHES TOTAL SNOWFALL...WHILE NWRN INDIANA MAY SEE
2 TO 4 INCHES.  HOWEVER...THESE AMOUNTS WILL BE HIGHLY DEPENDENT ON
SFC FETCH AND HOW QUICKLY SFC WINDS WILL BACK FROM NELY TO NWLY...SO
THERE IS STILL SOME UNCERTAINTY IN THE SNOWFALL AMOUNTS.  HAVE
BETTER CONFIDENCE IN GENERAL THAT ACCUMULATING SNOW WILL BE CONFINED
TO LOCATIONS NEAR THE LAKE AND THAT ANY SNOW OBSERVED FARTHER INLAND
WILL BE CLOSER TO A DUSTING.  BY TUESDAY AFTERNOON...LOW LEVEL WINDS
SHOULD VEER FAR ENOUGH THAT ANY LAKE EFFECT SNOW SHOULD BE OUT OF
THE CWA...WITH THE POSSIBLE EXCEPTION OF FAR NERN PORTER COUNTY.

TEMPERATURES FOR MONDAY SHOULD RANGE FROM THE UPPER 20S TO AROUND 30
ALONG THE WISCONSIN BORDER TO THE MIDDLE 30S SOUTH OF I-80.  THE
MORE SIGNIFICANT COOLING TREND WILL BEGIN MONDAY NIGHT AS THE ARCTIC
HIGH PRESSURE SPREADS ACROSS THE AREA AND INTO THE OHIO VALLEY AND
THROUGH THE LOWER MISSISSIPPI VALLEY.  BY TUESDAY
MORNING...ANTICIPATE LOW TO RANGE FROM THE LOWER TEENS OVER THE
ROCKFORD AREA TO THE LOWER 20S EAST OF THE I-55 CORRIDOR.
PERSISTENT COLD ADVECTION WILL KEEP HIGHS ON TUESDAY AND WEDNESDAY
IN THE MIDDLE TO UPPER TEENS.  THE LOWEST TEMPS SHOULD OCCUR
WEDNESDAY MORNING WITH MUCH OF THE CWA SEEING TEMPS DROP INTO THE
SINGLE DIGITS ABOVE 0F OVER NRN IL AND 10-13F OVER NWRN INDIANA.
WITH WINDS REMAINING AROUND 10 MPH THROUGH THE NIGHT...MIN WIND
CHILL READINGS TUESDAY MORNING SHOULD DROP TO AROUND -5F TO -10F.

SOME MODERATION IS EXPECTED FOR LATER IN THE WEEK...BUT TEMPERATURES
SHOULD REMAIN AROUND SEASONAL NORMAL LEVELS.  THE NEXT QUESTION FOR
THE EXTENDED FORECAST PERIOD WILL FOCUS ON THE EVOLUTION OF A STRONG
PACIFIC SHORTWAVE DROPPING DOWN THE WEST COAST AND CLOSING OFF OVER
THE DESERT SOUTHWEST WEDNESDAY NIGHT AND THURSDAY.  THE DIGGING
TROUGH OVER THE WEST SHOULD INITIATE SOME HEIGHT RISES OVER THE
MIDWEST...WHICH WILL HELP WITH THE MODERATING TEMPERATURES IN SPITE
OF PERSISTENT NWLY FLOW ALOFT AS BROAD LOW AMPLITUDE TROUGHING
DEVELOPS OVER THE NCNTRL/NERN CONUS WHILE AN UPPER HIGH PARKS OVER
THE GREATER ANTILLES AND WRN CARIBBEAN.  THE FORECAST CONCERNS WILL
FOCUS ON HOW QUICKLY THE UPPER LOW WILL LIFT OUT OF THE DESERT
SOUTHWEST WITH SRN STREAM ENERGY LIFTING THROUGH THE SRN PLAINS
AND...ULTIMATELY INTO THE SRN GREAT LAKES...AND HOW MUCH PHASING
WILL OCCUR WITH NRN STREAM ENERGY.  THE 12Z GFS IS STILL TRENDING
MUCH QUICKER THAN THE OTHER LONGER RANGE GUIDANCE WITH THE 12Z ECMWF
ADVERTISING THE SLOWEST SOLUTION AND THE GEM TAKING A MIDDLE OF THE
ROAD SOLUTION.  STILL FAVOR A SLOWER SOLUTION FOR A SRN STREAM
CUT-OFF AS THE MODELS ARE NOTORIOUS FOR BEING TOO FAST IN LIFTING
THESE SYSTEM NEWD.  THE GENERAL TREND FOR THE LATTER PORTIONS OF THE
EXTENDED FORECAST PERIOD SHOULD BE FOR INCREASING TEMPERATURES AND
POPS BY THE END OF THE WEEK AND INTO THE WEEKEND...BUT CONFIDENCE IS
STILL LOW ON THE EXACT DETAILS OF ANY ASSOCIATED PCPN.  TEMPERATURES
THROUGH THEN PERIOD SHOULD GENERALLY BE LOW ENOUGH TO SUPPORT SOME
SNOW...BUT THERE COULD ALSO BE PERIODS WHERE TEMPS COULD BE HIGH
ENOUGH FOR SOME OF THE PCPN TO BE EITHER RAIN OR A RAIN-SNOW MIX.

KREIN

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 00Z...

* MVFR CIGS DEVELOPING OVERNIGHT...AND CONTINUING MONDAY.
* LAKE EFFECT FLURRIES MONDAY AND MONDAY EVENING.
* NORTH/NORTHEAST WINDS APPROACHING 10KT MONDAY AFTERNOON. CMS

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

A WEAK TROUGH/FRONTAL BOUNDARY WILL MOVE ACROSS THE AREA THIS
EVENING WITH LIGHT WEST WINDS SHIFTING TO LIGHT NORTH/NORTHEAST
WINDS. AS HIGH PRESSURE BUILDS ACROSS THE PLAINS MONDAY INTO
MONDAY NIGHT...THE GRADIENT WILL SLOWLY TIGHTEN...WITH NORTHEAST
WINDS INCREASING UP TO 10 KTS OR SO BY LATER MONDAY AFTERNOON.
THE WINDS WILL THEN TURN MORE NORTHERLY MONDAY NIGHT WITH SPEEDS
IN THE 10-15KT RANGE POSSIBLE.

MVFR CIGS OVER CENTRAL WI WILL MOVE SOUTH THIS EVENING AND MAY
SPREAD ACROSS THE TERMINALS OVERNIGHT WITH MVFR CIGS CONTINUING
MONDAY. LOW CONFIDENCE REGARDING HOW SOON THESE CIGS WILL ARRIVE
BUT ONCE THEY DO...THEY SHOULD BECOME PREVAILING. AS COLDER AIR
SPREADS ACROSS THE AREA...LAKE EFFECT FLURRIES OR SNOW SHOWERS
ARE POSSIBLE MONDAY INTO MONDAY NIGHT. CONFIDENCE REGARDING HOW
WIDESPREAD THIS ACTIVITY BECOMES IS LOW AND FOR NOW OPTED TO
MAINTAIN VFR FLURRIES MENTION WITH A PROB FOR POSSIBLE LOWER
CONDITIONS AT GYY...THOUGH BEST CHANCES FOR LAKE EFFECT SNOW
SHOWERS AT GYY COULD BE MONDAY EVENING...AFTER THE END OF THIS
FORECAST. CMS

//ORD AND MDW CONFIDENCE...UPDATED 00Z...

* HIGH FOR MVFR CIGS...MEDIUM FOR TIMING.
* MEDIUM FOR LAKE EFFECT FLURRIES MONDAY/MONDAY EVENING.
* MEDIUM FOR WINDS THRU THE PERIOD. CMS

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

* TUESDAY...DRY. MVFR CIGS POSSIBLE. NORTHWEST WINDS.
* WEDNESDAY AND THURSDAY...DRY/VFR. GUSTY WESTERLY WINDS.
* FRIDAY...CHANCE OF SNOW. MVFR POSSIBLE. SOUTH/SOUTHEAST WINDS.
* SATURDAY...CHANCE OF RAIN OR SNOW. IFR POSSIBLE. SOUTH WINDS
  BECOMING WEST.

&&

.MARINE...
326 PM CST

LIGHTER SPEEDS HAVE BEEN OBSERVED OVER THE LAKE TODAY...WHILE A
NORTHWEST DIRECTION PREVAILED. A LINGERING TROUGH OF LOW PRESSURE
OVER SOUTHEAST ONTARIO IS HELPING FOR SLIGHTLY HIGHER SPEEDS OVER
THE NORTHERN HALF OF THE LAKE WHERE 15 TO 25 KT WINDS CONTINUE TO
BE OBSERVED...WITH 10 TO 20 KT BEING OBSERVED OVER THE SOUTHERN
HALF. THIS WILL LIKELY CONTINUE TONIGHT AS A FRONT PUSHES SOUTH
DOWN THE LAKE...AND THEN AS HIGH PRESSURE BUILDS SOUTHEAST THROUGH
THE UPPER MIDWEST AND GREAT LAKES. THIS HIGH WILL THEN CONTINUE TO
BUILD SOUTHEAST ON MONDAY...WITH THE CENTER OF THE STRONG HIGH
BUILDING SOUTH ACROSS THE PLAINS TUESDAY INTO WEDNESDAY. THIS WILL
HELP WITH A NORTH TO NORTHWEST WIND TO REMAIN IN PLACE DURING THIS
PERIOD...BEFORE WINDS TURN MORE WESTERLY TUESDAY NIGHT INTO
WEDNESDAY. EXPECT WINDS TO SIGNIFICANTLY INCREASE DURING THE DAY
WEDNESDAY WITH GALES APPEARING TO BE LIKELY...AS THE STRONG HIGH
REMAINS TO THE SOUTHWEST AND DEVELOPING LOW PRESSURE MOVES SOUTH
THROUGH HUDSON BAY.

RODRIGUEZ

&&

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

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.