National Weather Service Weather Forecast Office

• Home
• Site Map
• News
• Organization
• Search for: NWS All NOAA 

000
FXUS63 KLOT 100830
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
330 AM CDT MON MAR 10 2014

.DISCUSSION...

330 AM...PRIMARY FORECAST CONCERNS ARE RAIN CHANGING TO SNOW
TUESDAY EVENING WITH AN INCH OR TWO OF SNOW ACCUMULATION NORTH TO
PERHAPS SEVERAL INCHES ACROSS THE SOUTHERN CWA...THEN A SHORT
LIVED BLAST OF CHILLY TEMPS WEDNESDAY/WEDNESDAY NIGHT.

WARM AIR HAS SPREAD ACROSS THE REGION WITH TEMPS HOLDING STEADY IN
THE UPPER 30S/LOWER 40S. TEMPS MAY DROP A FEW DEGREES THROUGH
SUNRISE BUT BASICALLY STEADY. MID DECK CURRENTLY PASSING ACROSS
THE AREA MAY GENERATE A FEW SPRINKLES OVER THE NEXT FEW HOURS BUT
THE BACK EDGE OF THE HIGH CLOUDS IS QUICKLY PUSHING SOUTHEAST
THROUGH MN/WI AND SHOULD SEE MOSTLY SUNNY SKIES BY MID MORNING
WHICH WILL AID ALREADY MILD TEMPS TO WARM INTO THE 50S JUST ABOUT
EVERYWHERE. OVER THE DEEPER SNOWPACK ACROSS NORTHWEST IL...TEMPS
MAY ONLY BRIEFLY TOUCH LOWER 50S. ELSEWHERE MID/UPPER 50S ON TRACK
WITH THE POTENTIAL FOR SOME LOWER 60S ACROSS THE SOUTHERN CWA.

A FRONTAL BOUNDARY WILL SLOWLY SAG ACROSS SOUTHERN WI AND NORTHERN
IL LATE TONIGHT INTO TUESDAY MORNING. PRECIP WILL INITIALLY BE
RATHER LIGHT WITH A CONSENSUS OF KEEPING MUCH OF THE PRECIP NEAR
OR JUST NORTH OF THE STATE LINE THROUGH MIDDAY TUESDAY. THIS WILL
DRIFT SOUTH INTO NORTHERN IL DURING THE AFTERNOON WITH THERMAL
PROFILES SHOWING PRECIP TYPE SHOULD REMAIN LIGHT RAIN...THOUGH IT
WILL BE A CHILLY RAIN WITH TEMPS SLOWLY FALLING THROUGH THE 30S.
EVENTUALLY...PRECIP WILL TRANSITION TO LIGHT SNOW TUESDAY EVENING
WITH SOME LIGHT SNOW ACCUMULATIONS OF AN INCH OR SO POSSIBLE OVER
NORTHERN IL.

A DEVELOPING STORM SYSTEM OVER THE PLAINS TUESDAY WILL MOVE EAST
ACROSS THE OHIO VALLEY TUESDAY NIGHT WITH A BAND OF HEAVIER QPF
FALLING ACROSS CENTRAL IL INTO CENTRAL/NORTHWEST INDIANA TUESDAY
NIGHT INTO EARLY WEDNESDAY MORNING. EXACT PLACEMENT OF THIS
HEAVIER AXIS OF QPF IS STILL UNCERTAIN. IN ADDITION...PRECIP MAY
BEGIN AS RAIN OR A RAIN/SNOW MIX. ONCE IT CHANGES OVER TO ALL
SNOW...IT COULD BE RATHER WET WITH SNOW/WATER RATIOS AROUND OR
JUST UNDER 10:1. THIS ALL MAKES SNOW ACCUMULATIONS RATHER TRICKY.
THOUGH AS COLDER AIR SPREADS INTO THE REGION WEDNESDAY MORNING...
THE SNOW SHOULD BECOME A BIT DRIER WITH SOME BLOWING SNOW POSSIBLE
MAINLY OVER THE SOUTHERN THIRD OF THE CWA. BUT STORM TOTAL AMOUNTS
OF 1-3 INCHES ARE POSSIBLE ALONG A PNT TO VPZ LINE WITH MAYBE 3-5
INCHES ACROSS FAR SOUTHERN CWA BUT CHANGES ARE POSSIBLE AS TRENDS
BECOME MORE CLEAR.

WHILE TUESDAY WILL BE COOLER THAN TODAY OVER MUCH OF THE AREA...
WEDNESDAY WILL BE A BIG CHANGE FROM THE EXPECTED WARMER WEATHER.
HIGHS WILL LIKELY REMAIN IN THE 20S ACROSS MUCH OF THE AREA WITH A
NORTH WIND OF 15-25 MPH...PUSHING WIND CHILLS INTO THE LOWER TEENS
MAYBE EVEN SINGLE DIGITS BY LATE AFTERNOON. WINDS QUICKLY DIMINISH
WEDNESDAY EVENING AS HIGH PRESSURE MOVES ACROSS THE REGION. LOWS
EXPECTED IN THE TEENS WEDNESDAY NIGHT/THURSDAY MORNING BUT WITH
SOME WEAK WARMING ALOFT BY MORNING...COULD SEE STEADY OR SLOWLY
RISING TEMPS BY THURSDAY MORNING. TEMPS WILL MODERATE THURSDAY...
BACK INTO THE MID/UPPER 30S...BUT THIS IS COOLER THAN PREVIOUSLY
ADVERTISED AS WARMER AIR IS DELAYED AND TEMPS FRIDAY DEPENDENT ON
SPEED/TIMING OF A WEAK COLD FRONT THAT WILL PUSH ACROSS THE AREA
IN THE AFTERNOON. CMS

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* GUSTY SOUTHWEST WINDS THROUGH 09Z AND RETURNING AGAIN DURING
  TODAY.
* LLWS THROUGH 09Z OR SO.
* CHANCE FOR LIGHT FOG THIS EVE.
* WINDS TURNING NORTH NORTHEAST LATE IN THE TAF PERIOD.

//DISCUSSION...UPDATED 06Z...

SOUTHWEST FLOW ENCOMPASSES THE ENTIRE AREA VERY EARLY THIS
MORNING. AREA AMDAR SOUNDINGS AND VAD PROFILERS INDICATE 50 KT
FLOW AROUND 2000FT...AND 40KT FLOW MAY BE AS LOW AS SEVERAL
HUNDRED FEET ALOFT NEAR THE BASE OF THE TEMPERATURE INVERSION.
WE CONTINUE TO MENTION LLWS FOR THE 50 KT FLOW CORRIDOR DURING THE
FIRST SEVERAL HOURS OF THE TAF. SURFACE GUSTS ARE FAVORED TO ABATE
SOME TOWARD DAYBREAK BUT KICK BACK UP IN THE LATER MORNING AND
AFTERNOON BASED ON WARMING TEMPERATURES ALLOWING FOR AT LEAST
SHALLOW MIXING. AS A WEAK SURFACE TROUGH APPROACHES THE AREA LATE
IN THE DAY INTO THIS EVE...WINDS WILL TURN NORTHWEST. THIS TROUGH
WILL BASICALLY WEAKEN OVER THE AREA DURING THIS EVE AND THAT MAY
FOSTER FOG FORMATION AFTER A DAY OF SNOW MELT AND SUBLIMATION.
CONFIDENCE ON THIS AND WHAT CATEGORY IT WOULD BE IS LOW AT THIS
TIME. IN ADDITION...THIS SHOULD ALLOW FOR WINDS TO TURN NORTHEAST
LATER INTO MONDAY NIGHT AS COLD AIR ADVECTION OOZES SOUTHWARD INTO
THE REGION.

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* HIGH IN WIND TRENDS THROUGH EARLY THIS MORNING...THEN MEDIUM
  THEREAFTER.
* HIGH IN LLWS.
* LOW IN TIMING OF WIND SHIFT TO NORTHEAST LATE IN THE TAF PERIOD
  AND ANY FOG THIS EVE.

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

TUESDAY...CHC OF RAIN DURING DAY WITH A CHC OF RAIN OR SNOW IN
          EVENING AND CHC SNOW OVERNIGHT. IFR POSSIBLE.
WEDNESDAY...SLGT CHC OF SNOW. GUSTY NORTHERLY WINDS.
THURSDAY-SATURDAY...VFR LIKELY.

MTF/RC

&&

.MARINE...
225 AM CDT

AN ACTIVE AND PROGRESSIVE PATTERN IN THE MIDDLE OF THE COUNTRY WILL
PRESENT NUMEROUS PERIODS OF AT LEAST MODEST WINDS OVER LAKE
MICHIGAN. WHILE A FEW SOUTHWEST WIND GUSTS TO AROUND 30 KT WILL
BE SEEN THROUGH DAYBREAK OVER THE FAR SOUTHERN PART OF THE
LAKE...MOST OF THE SOUTHWEST GUSTS SEEN TODAY WILL BE 20 KT OR
LESS. AS LOW PRESSURE MOVES EAST ACROSS ONTARIO TONIGHT...A WEAK
COLD FRONT WILL TURN THE WIND NORTHWEST OVER THE LAKE.

THE WIND WILL TURN MORE NORTHERLY ON TUESDAY AS LOW PRESSURE
DEVELOPS ALONG THE AFOREMENTIONED FRONT IN THE SOUTHERN PLAINS.
AS THIS LOW ADVANCES UP THE OHIO RIVER VALLEY LATER TUESDAY NIGHT
INTO WEDNESDAY...NORTHERLY WINDS WILL FURTHER INCREASE OVER THE
LAKE WITHIN A TIGHT PRESSURE GRADIENT. GALE POTENTIAL REMAINS
ACROSS THE SOUTHERN PART OF THE LAKE...INCLUDING THE ILLINOIS AND
INDIANA NEARSHORE FOR LATE TUESDAY NIGHT AND WEDNESDAY. DID
CONSIDER A WATCH AS OVERALL SYNOPTIC SIGNATURE IS GOOD FOR
GALES...WITH A LOW PASSING TO THE SOUTH AND A PRESSING HIGH TO THE
NORTH. WITH STILL JUST BEYOND 48 HOURS...HAVE OPTED TO HOLD BACK
AT THIS TIME...AS SOME SHIFTING OF THE LOW PATH MAY OCCUR. LATE IN
THE WEEK...ANOTHER PACIFIC/CLIPPER TYPE SYSTEM IS FORECAST TO
APPROACH THE LAKE FROM THE NORTHWEST AND WOULD FAVOR A PERIOD OF
AGAIN MODEST SOUTHWEST TO WEST WINDS.

MTF

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS UNTIL 7 AM MONDAY.

&&

$$

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

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