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 052033
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
233 PM CST FRI FEB 5 2016

.SHORT TERM...
232 PM CST

TONIGHT THROUGH SATURDAY...

LOW CLOUDS CONTINUE TO SCATTER-OUT FROM NORTHWEST TO SOUTHEAST
THIS AFTERNOON AS WEAK SURFACE HIGH PRESSURE MOVES INTO THE REGION
IN THE WAKE OF THIS MORNINGS WEAK COLD FRONT. HIGH CLOUDS WERE
ALREADY BEGINNING TO SPREAD ACROSS THE AREA FROM THE WEST...AHEAD
OF THE NEXT DISTURBANCE OVER THE PLAINS. EXPECT THAT TEMPS WILL
FALL OFF INTO THE 20S WITH SUNSET...THEN HOLD NEARLY STEADY
OVERNIGHT AS CLOUDS THICKEN. GUIDANCE IN CLOSE AGREEMENT WITH
TEMPS AND DID NOT STRAY MUCH FROM MET/MAV BLEND.

ANOTHER WEAK CLIPPER SYSTEM WILL MOVE ACROSS THE AREA TONIGHT
INTO SATURDAY MORNING...KICKING A WEAK SHORT WAVE OVER THE MID-
MISSOURI VALLEY NORTHEAST ACROSS THE REGION AHEAD OF IT TONIGHT.
UPSTREAM 12Z RAOBS FROM THIS MORNING DEPICT FAIRLY DRY AIR BELOW
ABOUT 650 MB AND MODEL SOUNDINGS AND TIME-HEIGHT DEPICTIONS
INDICATE THAT LOWER LEVELS MAY STRUGGLE TO WITH GENERALLY WEAK
FORCING FOR ASCENT. REGIONAL RADAR MOSAIC AND SURFACE OBS DO
INDICATE LIGHT SNOW OCCURRING ACROSS WESTERN IA AT THIS
TIME...THOUGH MODELS ERODE THIS PRECIP WITH TIME AS IT TRIES TO
SPREAD EAST. THUS WHILE MID/HIGH CLOUDS WILL THICKEN THIS
EVENING...NO GUIDANCE PRODUCES MEASURABLE PRECIP FROM THE
APPROACHING SYSTEM AND IT APPEARS THAT ANYTHING MORE THAN A FEW
FLURRIES IS UNLIKELY. TIMING FOR FLURRIES APPEARS TO BE MAINLY
AFTER MIDNIGHT TONIGHT THROUGH EARLY SATURDAY MORNING.

MID-LEVEL TROUGH AXIS MOVES OFF TO THE EAST OF THE FORECAST AREA
SATURDAY AFTERNOON...WITH ASSOCIATED SURFACE TROUGH WASHING OUT
ACROSS THE CWA AND BECOMING INDISTINCT. T-SECTS INDICATE SKIES
WILL BECOME PARTLY SUNNY ESPECIALLY ACROSS THE SOUTHERN PARTS OF
THE CWA. MODEST SOUTHWEST WINDS MAINTAIN WARM ADVECTION THROUGH
THE DAY AND 925-950 MB TEMPS SUPPORT AFTERNOON HIGHS IN THE MID-
UPPER 30S FAR NORTH...AND IN THE LOWER 40S ALONG AND SOUTH OF THE
I-80 CORRIDOR. PREFERRED THE SLIGHTLY WARMER MAV GUIDANCE FOR
SATURDAY MAX TEMPS.

RATZER

&&

.LONG TERM...
259 AM CST

SUNDAY THROUGH THURSDAY...

THE NEXT SYSTEM MOVES OVER THE REGION MONDAY AND THE SURFACE LOW
SHOULD BE VERTICALLY ALIGNED WITH THE UPPER LEVEL LOW.  THE TRICKY
PART WILL BE IF THERE WILL BE PRECIP SUNDAY AS THE UPPER LEVEL LOW/S
VORTICITY STREAMERS ROTATE THROUGH. DECIDED TO INCLUDE LOW END
SLIGHT CHANCE TO CHANCE POPS FOR LIGHT PRECIP THROUGH THE DAY.  THE
BETTER CHANCES WILL BE ALONG THE IL/WI STATE LINE CLOSER TO THE
PARENT LOW AND FORCING. TEMPS WILL BE INCREASING TO ABOVE FREEZING
SUNDAY SO HAVE PRECIP BEGINNING AS SNOW BECOMING RAIN BY MID DAY.
THERE IS A DECENT CHANCE THAT SUNDAY MAY BE DRY...SO HAVE HIGH
CONFIDENCE IN TEMPS SUNDAY BUT LOW CONFIDENCE IN PRECIP CHANCES.

THE LOW MOVES OVER THE REGION SUNDAY NIGHT AND GUIDANCE FEATURES
SOME DIFFERENCES IN THE LOWS PATH.  EITHER WAY HAVE HIGHER
CONFIDENCE IN PRECIP SUNDAY NIGHT THROUGH MONDAY.  COLDER AIR MOVES
IN THE WITH THE LOW RESULTING IN LOWS BELOW FREEZING SUNDAY NIGHT.
AS SUCH HAVE RAIN BECOMING SNOW.  INITIAL SNOWFALL TOTALS THROUGH
SUNDAY NIGHT ARE ALL LESS THAN A HALF OF AN INCH AS FORCING LOOKS
MEAGER.

LIGHT SNOW CONTINUES THROUGH TUESDAY NIGHT ESPECIALLY OVER NORTHWEST
INDIANA WHERE LAKE EFFECT SNOW MAY PERSIST INTO WEDNESDAY. THE LOW
AND ITS TROUGH PUSH EAST TUESDAY AFTERNOON...BUT A SECOND
TROUGH/VORT STREAMER PUSHES SOUTH FROM CANADA INTO THE MIDWEST
TUESDAY NIGHT INTO WEDNESDAY. THE BIGGER STORY WITH THE SECOND
STREAMER WILL BE A PUNCH OF COLD AIR...-10 TO -20C AT 850
MB...MOVING OVER THE REGION. IT LOOKS LIKE WE WILL MISS THE COLDEST
AIR ASSOCIATED WITH THE STREAMER...BUT WIND CHILLS TUESDAY
NIGHT/WEDNESDAY MORNING WILL BE AROUND 0 OR SLIGHTLY BELOW ZERO.

HIGH PRESSURE MOVES OVER THE REGION MID TO LATE NEXT WEEK WITH LAKE
EFFECT SNOW FOCUSING EAST OF THE WARNING AREA. TEMPS WILL BE IN THE
20S WEDNESDAY AND THEN AROUND 30 THURSDAY.

JEE

&&

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

MAIN AVIATION CONCERNS ARE LINGERING 1300-1900 FT MVFR BKN CIGS
EARLY THIS AFTERNOON...AND LOW PROBABILITY OF FLURRIES LATER
TONIGHT/EARLY SATURDAY MORNING.

WEAK MID-LEVEL WAVE CONTINUES TO MOVE SLOWLY EAST-SOUTHEAST ACROSS
SOUTHERN LAKE MICHIGAN THIS AFTERNOON...WITH A FEW FLURRIES
LINGERING OVER GYY-VPZ AREAS AND BKN MVFR DECK ERODING FROM THE
NORTHWEST ACROSS OTHER TERMINALS. WHILE SOME HOLES HAVE OPENED UP
ACROSS ORD...VISIBLE SATELLITE TRENDS SUGGEST A COUPLE HOURS OF
BKN MVFR CIGS STILL LIKELY EARLY THIS AFTERNOON. HIGH CLOUDS ARE
ALREADY STREAMING IN FROM THE WEST AHEAD OF THE NEXT DISTURBANCE
WHICH WILL MOVE ACROSS THE AREA TONIGHT AND SATURDAY MORNING. THIS
APPROACHING SYSTEM IS WEAKER THAN THE ONE WHICH BROUGHT LIGHT SNOW
TO THE REGION THIS MORNING...AND MODEL FORECAST SOUNDINGS INDICATE
ATMOSPHERE WILL STRUGGLE TO SATURATE THROUGH A DEEP LAYER. SOME
POTENTIAL FOR A LOWER VFR CEILING IN THE 3500-4500 FT RANGE FROM
THIS EVENING INTO EARLY SATURDAY...AND A FEW FLURRIES CANT BE
RULED OUT...THOUGH NO HIGH-RES GUIDANCE ACTUALLY INDICATES
MEASURABLE PRECIP FOR ANY OF THE TAF SITES. CONFIDENCE IS HIGH
THAT MVFR CIGS WILL SCATTER TO VFR THIS AFTERNOON...AND MEDIUM-
HIGH IN MAINTAINING VFR CONDITIONS THROUGH SATURDAY MORNING.

AS FOR WINDS...NORTHWEST WINDS NEAR 10 KT AT MIDDAY WILL SLOWLY
DIMINISH AND BECOME SOUTHWEST BY MID-LATE EVENING AS WEAK SURFACE
HIGH PRESSURE MOVES ACROSS THE AREA. SOUTH-SOUTHWEST WINDS LESS
THAN 10 KTS PICK UP TO AROUND 10 KTS LATER SATURDAY AFTERNOON.
CONFIDENCE IS HIGH IN WIND TRENDS.

RATZER

&&

.MARINE...
104 PM CST

MARINE FORECAST CONCERNS FOCUS ON A COUPLE PERIODS OF STRONGER
FLOW. THE FIRST OF THESE COMES TONIGHT INTO SATURDAY MORNING
ACROSS NORTHERN PARTS OF THE LAKE...AS WEST-SOUTHWEST WINDS
INCREASE TO 25-30 KT IN RESPONSE TO AN AREA OF LOW PRESSURE
PASSING TO THE NORTH OF LAKE SUPERIOR. THE GRADIENT WILL EASE A
BIT BY SATURDAY AFTERNOON AS A WEAK COLD FRONT SAGS ACROSS THE
NORTHERN LAKES. DEEPER LOW PRESSURE WILL TRACK SOUTHEAST ALONG
THIS BOUNDARY SATURDAY NIGHT... RESULTING IN WINDS BACKING MORE
SOUTHERLY AND PICKING UP TO 20-25 KT. THE LOW IS EXPECTED TO MOVE
ACROSS LAKE MICHIGAN ON MONDAY WITH WINDS DECREASING AS THE
GRADIENT AGAIN WEAKENS NEAR THE LOW CENTER. THE LOW WILL MOVE
SLOWLY OFF TO THE EAST-SOUTHEAST MONDAY NIGHT...WHILE HIGH
PRESSURE BUILDS ACROSS THE CANADIAN PRAIRIES AND NORTHERN PLAINS
AND CAUSES THE GRADIENT TO STRENGTHEN AGAIN. NORTH-NORTHWEST WINDS
ARE EXPECTED TO INCREASE TO 30 KT AFTER MIDNIGHT MONDAY NIGHT AND
CONTINUE THROUGH TUESDAY. SOME MODEL FORECASTS SUPPORT MARGINAL
GALES DURING THIS PERIOD.

RATZER

&&

.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.