Area Forecast Discussion
Issued by NWS Chicago, IL

Home | Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary On
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 102004
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
204 PM CST WED FEB 10 2016

.SHORT TERM...
331 AM CST

THROUGH TONIGHT...

THE MESSAGE FOR THE REMAINDER OF THE WEEK AND THIS WEEKEND IS
SIMPLY UNSEASONABLY COLD. EARLY MORNING LOWS MAY DIP TO SUBZERO IN
OUTLYING LOCATIONS THURSDAY MORNING THEN AGAIN SATURDAY AND SUNDAY
MORNINGS. AT THIS TIME IT APPEARS FOR THE MOST PART WIND CHILLS
SHOULD REMAIN ABOVE OUR CRITERIA OF ADVISORY /WHICH IS AOB
-15F/...THOUGH COULD DIP TO THAT LEVEL LATER FRIDAY NIGHT AND
SATURDAY MORNING. NO MAJOR SNOW CHANCES EXIST THROUGH
SATURDAY...THOUGH CONTINUING TO SEE A TREND FOR PART OF NORTHWEST
INDIANA TO SEE SOME LAKE EFFECT SNOW FRIDAY NIGHT AND SATURDAY.

THE HIGHLY AMPLIFIED LONG WAVE TROUGH OVER EASTERN NORTH AMERICA
IS FINALLY SHIFTING ITS WAY EASTWARD. UPPER TROPOSPHERIC NORTHERLY
FLOW BEHIND THIS WILL KEEP THE COLD PATTERN IN PLACE THOUGH WITH A
MODIFIED ARCTIC AIR MASS HAVING SPREAD INTO THE REGION. THE MIXED
LAYER WILL WARM LITTLE TODAY WITH 925MB TEMPERATURES AROUND -16C.
THIS PROFILE AND UPSTREAM TEMPERATURES YESTERDAY LOOK TO SUPPORT
MID TEENS FOR HIGHS. THE CLOUD FORECAST FOR TODAY IS CHALLENGING
AS OFTEN CAN BE THE CASE AT THE PERIPHERY OF DEPARTING CYCLONIC
FLOW. EXPECT THAT EARLY MORNING HOLES WILL FILL IN DURING MIDDAY
WITH THE CONTINUED STEEP LAPSE RATES. DRY ADVECTION HAS BROUGHT
DEW POINTS TO AROUND OR EVEN BELOW ZERO INTO THE FORECAST
AREA...SO THE CLOUDS ARE LIKELY TO BE THIN. THESE SHOULD ADVECT
AWAY TONIGHT. COMBINED WITH WEAKENING WINDS AND A LIGHT BUT FRESH
SNOW IN PLACES...THE CLEAR NIGHT WILL SEE LOWER TO MID SINGLE
DIGITS IN MOST LOCATIONS WITH THE SUBZERO LOWS POSSIBLE IN THE
USUAL COLDER SPOTS.

MTF

&&

.LONG TERM...
331 AM CST

THURSDAY THROUGH WEDNESDAY...

HIGH PRESSURE AT THE SURFACE WILL PREVAIL THURSDAY INTO THURSDAY
NIGHT WITH THE DAYTIME HOURS OF THURSDAY LIKELY TO BE PRIMARILY
SUNNY AND ASSISTING IN A WEE BIT OF TEMPERATURE MODERATION. MODEL
GUIDANCE CONTINUES TO INDICATE A SHEARED SHORT WAVE TROUGH DIVING
SOUTHEAST FROM THE UPPER PLAINS TO THE LOWER OHIO VALLEY THURSDAY
NIGHT INTO FRIDAY. THIS IS BASICALLY RIDING THE ELEVATED
BAROCLINIC ZONE SIMILAR TO A SYSTEM TODAY OFF TO OUR SOUTHWEST.
CONTINUE TO THINK MOST SNOW WITH THIS WILL REMAIN SOUTH. FRIDAY
SHOULD BE CLOUDY THOUGH AND MAYBE ENOUGH WEAK ISENTROPIC ASCENT
FOR SOME FLURRIES.

THAT SHORT WAVE AND JET WITH REINFORCE THE COLD AIR INTO THE
REGION...BRINGING THE ARCTIC COLD FRONT BACK SOUTH FRIDAY
AFTERNOON OR EVENING. THIS SETS UP THE COLD WEEKEND PARTICULARLY
SATURDAY. WHILE AGAIN SOME FLURRIES MAY BE SEEN WITH THIS...MOST
OF THE AREA SHOULD BE DRY. THE EXCEPTION IS FAR NORTHWEST INDIANA
WHERE BOUNDARY LAYER FLOW IS LIKELY TO TURN MORE NORTHERLY WITH A
DEEP LOW FAVORED OFF THE NORTHEAST U.S. AND A 1040MB+ HIGH TO THE
WEST. FORECAST EQUILIBRIUM LEVELS FROM THE GFS ARE OVER 10000
FT...BUT MOISTURE MAY BE DRY ENOUGH THAT COVERAGE OF ANY LAKE
EFFECT SNOW SHOWERS MAY BE IN SINGLE BAND/S/. TOO EARLY YET TO
TELL IF THERE WILL BE VERY FOCUSED CONVERGENCE OR EVEN IF SNOW
SHOWERS WILL ROTATE BACK TO THE WEST FAR ENOUGH TO IMPACT PORTER
AND LAKE COUNTIES.

GLOBAL GUIDANCE HAS INDICATED A PACIFIC/CLIPPER HYBRID SYSTEM
CROSSING THE GENERAL REGION SOMETIME LATE IN THE WEEKEND/EARLY
NEXT WEEK. CONFIDENCE IN THIS SYSTEM IS LOW AND IT CERTAINLY COULD
SLOW TOO. EVEN IF THAT WERE TO HAPPEN THE COLD AIR IN ADVANCE
LOOKS LIKE THE PROFILES SHOULD BE COOL ENOUGH TO SUPPORT SNOW. HOW
MUCH IF ANY SNOW THOUGH WILL DEPEND ON ITS EXACT TRACK WHICH COULD
VARY SIGNIFICANTLY YET FOR SEVERAL MODEL RUNS.

MTF

&&

.AVIATION...
FOR THE 18Z TAFS...

FAIRLY QUIET FORECAST ON TAP FOR THE CHICAGO/ROCKFORD AREA
TERMINALS THROUGH TOMORROW. AREA OF THIN OVERCAST STRATUS THAT
WAS IN PLACE THIS MORNING HAS BECOME SCT-BKN THIS HOUR AND EXPECT
PRIMARILY VFR CONDITIONS TO PREVAIL THROUGH REMAINDER OF THE
FORECAST PERIOD. RIDGE OF HIGH PRESSURE CURRENTLY STRETCHES FROM
THE LOWER TO UPPER MISSISSIPPI VALLEY AND WILL INCH TOWARDS THE
TERMINALS ALLOWING WINDS TO DIMINISH...AND EVENTUALLY BACK TO THE
WEST/SOUTHWEST THURSDAY. AN AREA OF LOW PRESSURE IS PROGGED TO
MOVE FROM THE PLAINS INTO THE LOWER MISSISSIPPI VALLEY TONIGHT
RESULTING IN AN INCREASE IN MAINLY UPPER LEVEL CLOUD
COVER...THOUGH ANY PRECIP WITH THIS SYSTEM WILL STAY WELL TO OUR
WEST AND SOUTH.

BMD

&&

.MARINE...
202 PM CST

A MODERATELY STRONG NORTH TO NORTHWESTERLY GRADIENT WILL PERSIST
OVER LAKE MICHIGAN THROUGH TONIGHT AHEAD OF A RIDGE THAT STRETCHES
FROM THE NORTHWEST TERRITORIES INTO THE MISSISSIPPI VALLEY.
WINDS OF 30 KT AND FREEZING SPRAY WILL CONTINUE INTO SOME OF THE
OVERNIGHT HOURS THEN SHOULD DIMINISH EARLY THURSDAY AS THE HIGH
INCHES EAST ALLOWING THE GRADIENT TO RELAX. WINDS ALSO BACK TO THE
WEST ON THURSDAY AS THE HIGH BUILDS SOUTH OF LAKE MICHIGAN...THEN
FRESHEN UP AS LOW PRESSURE FORMS OVER ONTARIO. THIS LOW WILL BRING
A REINFORCING SHOT OF COLD AIR SOUTH ON FRIDAY BEHIND A TRAILING
COLD FRONT AND AS A STRONG ARCTIC HIGH BUILDS ACROSS CANADA INTO
THE UPPER MIDWEST. AT LEAST A SHORT WINDOW OF NORTHERLY GALES ARE
EXPECTED BEHIND THE COLD FRONT FRIDAY EVENING OR OVERNIGHT...THEN
WINDS SHOULD GRADUALLY DIMINISH OVER THE WEEKEND AS THE HIGH
BUILDS ACROSS THE GREAT LAKES.

BMD

&&

.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.

&&

$$

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.