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000
FXUS63 KLOT 070928
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
328 AM CST FRI MAR 7 2014

.DISCUSSION...

328 AM...FORECAST CONCERNS INCLUDE HIGH TEMPERATURES JUST ABOUT
EVERY DAY OVER THE NEXT WEEK...POTENTIAL FOR MINOR SNOW
ACCUMULATIONS LATE TONIGHT INTO SATURDAY MORNING AND ANOTHER
PERIOD OF SNOW ACCUMULATION TUESDAY NIGHT INTO WEDNESDAY.

HIGH/MID LEVEL CLOUDS WILL BE INCREASING LATER THIS MORNING AND
WILL LIKELY BECOME BKN/OVC BY MID/LATE AFTERNOON. WHILE THIS MAY
HAVE AN IMPACT ON HIGH TEMPS TODAY...STRONG WARM AIR ADVECTION
WILL TAKE PLACE WITH WINDS TURNING SOUTHWEST. CURRENT TEMPS ACROSS
NORTHERN MO/SOUTHWESTERN IA ARE IN THE LOWER/MID 30S. THUS HAVE
CONTINUED WITH CURRENT FORECAST OF HIGHS GENERALLY IN THE LOWER/
MID 40S...PERHAPS A FEW UPPER 30S ACROSS NORTHERN AREAS AND THEN
POSSIBLE UPPER 40S/NEAR 50 FAR SOUTH WHERE SNOWPACK HAS MELTED.

A COLD FRONT WILL ENTER THE NORTHWESTERN CWA THIS EVENING...
MOVING SOUTH OF THE AREA BY SATURDAY MORNING. AFTER A QUICK DROP
WITH SUNSET...TEMPS WILL LIKELY HOLD IN THE MID/UPPER 30S UNTIL
FROPA. ONCE WINDS TURN OFF THE LAKE...COLDER AIR OVER THE ICE PACK
COULD USHER IN SLIGHTLY COLDER AIR THAN MIGHT OTHERWISE BE
EXPECTED. THERMAL PROFILES SUPPORT PRECIP TYPE QUICKLY SWITCHING
FROM RAIN TO SNOW. THERE COULD BE A BRIEF PERIOD WHERE PRECIP TYPE
MIXES WITH SOME SLEET OR SURFACE TEMPS DROP BELOW FREEZING BEFORE
PRECIP SWITCHES OVER TO SNOW. HAVE MAINTAINED JUST RAIN TO SNOW IN
THE FORECAST BUT LATE EVENING THROUGH EARLY OVERNIGHT WILL NEED TO
BE MONITORED FOR A POSSIBLE MIX.

GEM/ECMWF/GFS ALL IN GOOD AGREEMENT WITH A BAND OF LIGHT QPF
MOVING ACROSS THE NORTHERN HALF/TWO THIRDS OF THE CWA OVERNIGHT
INTO SATURDAY MORNING WITH THE BULK OF THIS FALLING AS SNOW. THUS
SNOW ACCUMULATIONS OF UP TO OR AROUND AN INCH LOOK ON TRACK THOUGH
CONFIDENCE ON SPECIFIC AMOUNTS IS A BIT LOWER DUE TO SURFACE TEMPS
AND SNOW/WATER RATIOS. SNOW COULD BE RATHER WET AS IT BEGINS WITH
SOME INITIAL MELTING.

THIS PRECIP SHIFTS SOUTHEAST BY SATURDAY AFTERNOON WITH DRY
WEATHER EXPECTED THROUGH MONDAY NIGHT ALONG WITH A WARMING TREND.
A RIDGE OF HIGH PRESSURE WILL SETTLE ACROSS THE REGION SATURDAY
NIGHT INTO SUNDAY MORNING. LIGHT WINDS AND CLEAR SKIES SHOULD
ALLOW FOR GOOD RADIATIONAL COOLING. HAVE HELD TEMPS CLOSE TO
PREVIOUS FORECAST...WARMING THEM A FEW DEGREES. BUT IF THE HIGH
SPEEDS UP AND FLOW TURNS SOUTHWESTERLY FASTER...WARMER AIR ALOFT
MAY KEEP LOW TEMPS WARMER THAN CURRENTLY ADVERTISED AND THIS
TREND WILL LIKELY CONTINUE INTO SUNDAY. WITH SUNNY SKIES EXPECTED
HAVE INCREASED TEMPS A FEW DEGREES TOWARD WARMER MAV NUMBERS AND
THIS MAY END UP STILL BEING TOO COOL...CURRENTLY MID/UPPER 30S
NORTH TO MID 40S SOUTH.

GEM/ECMWF ARE NOW IN DECENT AGREEMENT WITH 850MB TEMPS INTO THE
+10C TO +12C RANGE FOR MONDAY AND MADE NO CHANGES TO GOING HIGHS
OF MID 40S NORTH TO MID 50S SOUTH AS THESE APPEAR ON TRACK AT THIS
TIME.

A COLD FRONT WILL MOVE SOUTH MONDAY NIGHT INTO TUESDAY AND ITS A
BIT EARLY FOR SPECIFIC TIMING BUT TEMPS AHEAD OF THIS FRONT WILL
STAY MILD AND THERE COULD BE QUITE A TEMP GRADIENT OVER THE CWA OR
NEARBY ON TUESDAY. POSSIBLE THAT TEMPS ACROSS THE SOUTHERN CWA
WILL BE BACK IN THE 50S AHEAD OF THE FRONT ON TUESDAY. DURING THIS
SAME TIME PERIOD...A STORM SYSTEM WILL BE DEVELOPING OVER THE
PLAINS AND SHIFTING EAST ACROSS THE OHIO VALLEY IN THE WEDNESDAY
TIME PERIOD. CURRENT TRENDS WOULD SUGGEST THE HEAVIEST PRECIP
FROM THIS SYSTEM WILL REMAIN SOUTH OF THE AREA...WITH A PERIOD OF
RAIN CHANGING TO SNOW WITH THE COLD FRONT...SIMILAR TO TONIGHTS
SYSTEM. HOWEVER...MADE NO SIGNIFICANT CHANGES TO TUESDAY/WEDNESDAY.
CMS

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 09Z...

* SW WINDS OVER 10 KT THIS AFTERNOON.
* CHC FOR A LIGHT MIX OF PRECIP LATE THIS EVE INTO EARLY OVERNIGHT
  BEFORE AN INCREASING CHANCE FOR LIGHT/MODERATE SNOW TOWARDS
  DAYBREAK SAT.
* WINDS BECOMING NORTHEAST OVERNIGHT PRIOR TO DAYBREAK SAT.

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

THE SURFACE HIGH PRESSURE RIDGE THAT HAD BEEN IN CONTROL MUCH OF
THU WILL CONTINUE THROUGH DAYBREAK FRI BEFORE SHIFTING EAST. THIS
WILL ENABLE SOUTHWEST WINDS TO INCREASE FRIDAY WITH SOME SPORADIC
GUSTINESS OVER 15 KT POSSIBLE. A COLD FRONT WILL EASE ITS WAY
ACROSS NORTHERN IL AND NORTHWEST IN ON FRI EVE. THIS FRONT HAS
MORE ANAFRONT CHARACTERISTICS...THAT IS THE FORCING FOR PRECIP IS
LOCATED BEHIND THE ACTUAL SURFACE WIND SHIFT. TEMPERATURES WILL
START TO COOL IN THE ATMOSPHERE AND IF PRECIP CAN HAPPEN EARLY
ENOUGH IT COULD BE RAIN OR ICE PELLETS BUT WOULD LIKELY BE LIGHT.
SUBSTANTIAL ENOUGH COOLING SHOULD OCCUR FOR PRECIP TYPE TO BE SNOW
WHEN THE STRONGER FORCING MOVES OVER THE AREA LATE FRI NIGHT INTO
EARLY SAT MORNING. SNOWFALL AMOUNTS ARE PRESENTLY FAVORED TO BE
UP TO AN INCH AT MOST.

IN ADDITION...WITH THE WIND SHIFT TO NORTHWEST...THE WIND
DIRECTION WILL BE MORE FAVORED TO TURN NORTH NORTHEAST OR EVEN
NORTHEAST AT CHICAGOLAND AIRPORTS LATE TONIGHT DUE TO THE LAKE
MICHIGAN INFLUENCE. WITH THIS...SPEEDS ARE ALSO FAVORED TO COME UP
OVER 10 KT LATE TONIGHT INTO THE MORNING SAT.

//ORD AND MDW CONFIDENCE...UPDATED 09Z...

* HIGH IN WIND FORECAST THROUGH TODAY THEN MEDIUM AFTER.
* MEDIUM IN SNOW OCCURRING LATE TONIGHT WHILE LOW ON LOWEST
  VISIBILITY AND CIG DURING THE SNOW. MEDIUM ON START TIME.

//OUTLOOK FOR ORD/MDW FOR 12Z SATURDAY-12Z FRIDAY...UPDATED 00Z...

SATURDAY...CHANCE SNOW...MAINLY IN THE MORNING...PERIODS OF MVFR
TO IFR CIGS/VIS POSSIBLE. VFR/WX NIL OVERNIGHT.

SUNDAY AND MONDAY...VFR/WX NIL.

TUESDAY...CHANCE OF RAIN DAYTIME. CHANCE OF SNOW OVERNIGHT. IFR
CIGS/VIS POSSIBLE.

WEDNESDAY...SLIGHT CHANCE OF SNOW WITH IFR CIGS/VIS POSSIBLE.

MTF/KJB

&&

.MARINE...
220 AM CST

THE PATTERN OVER LAKE MICHIGAN WILL TRANSITION BACK TO MORE ACTIVE
AS SEVERAL SYSTEMS WILL PASS OVER OR NEAR THE GREAT LAKES IN THE
NEXT WEEK. BY TONIGHT...LOW PRESSURE FROM THE UPPER MISSISSIPPI
VALLEY WILL ADVANCE TO SOUTHERN ONTARIO AND BRING A COLD FRONT
SOUTHWARD. WHILE THE LOW IS NOT MOVING THAT QUICKLY...THE FRONT
SHOULD PROGRESS NICELY DOWN THE LAKE TONIGHT AS ANAFRONTS OFTEN
CAN THIS TIME OF YEAR. HIGH PRESSURE WILL BUILD INTO THE PLAINS
STATES SATURDAY BUT ITS CENTER WILL EVOLVE MORE SOUTH THAN EAST
AS AN ACTIVE PACIFIC JET ADVANCES EASTWARD ALONG THE U.S./CANADIAN
BORDER. THIS WILL STEER TWO LOW PRESSURE SYSTEMS QUICKLY EASTWARD
WITH EACH FAVORED TO PASS JUST NORTH OF LAKE SUPERIOR...ONE SUNDAY
AND THE OTHER MONDAY AFTERNOON INTO NIGHT. WITH EACH WILL COME
WARM AIR ADVECTION. WITH SO MUCH OF THE LAKE BEING ICE
COVERED...AND SNOW ON TOP OF THAT ICE...A STOUT INVERSION IS
FAVORED. SO TO WHAT DEGREE GUSTS CAN REACH THE SURFACE IS
CHALLENGING. AT THIS POINT THE FIRST SYSTEM WOULD BE MORE FAVORED
TO BRING STRONG WINDS AND AT THIS TIME HAVE KEPT GUSTS BELOW GALES
IN THE FORECAST...BUT THE NORTH AND CENTRAL PARTS COULD END UP
BEING CLOSE TO AT LEAST TEMPORARY GALES.

THE VISIBLE SATELLITE FROM THURSDAY REVEALED THE LAKE IS MAINLY
ICE COVERED WITH THE NATIONAL ICE CENTER INDICATING THAT IS THE
CASE OVER 90 PERCENT OF LAKE MICHIGAN. SO WAVE FORECASTS ARE ONLY
FOR A SMALL PART OF THE OPEN WATER AND CONTINUE TO KEEP OUT WAVES
IN THE ILLINOIS AND INDIANA NEARSHORE FORECAST.

MTF

&&

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

$$

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