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000
FXUS63 KLOT 072044
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
244 PM 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 20Z...

* SOUTH-SOUTHWEST WINDS 10+ KT THIS AFTN.
* COLD FRONTAL PASSAGE WITH WIND SHIFT TO NORTHWEST BY LATE
  EVENING.
* MVFR CIG DEVELOPMENT OVERNIGHT WITH A PERIOD OF LIGHT SNOW LATE
  TONIGHT/EARLY SATURDAY.
* NORTHEAST WINDS 10-15 KT SATURDAY.

RATZER

//DISCUSSION...UPDATED 18Z...

WEAK AREA OF LOW PRESSURE MOVING ACROSS THE NORTHERN GREAT LAKES
THIS AFTERNOON WILL TRAIL A COLD FRONT THROUGH THE FORECAST AREA
THIS EVENING. NARROW AXIS OF RETURN MOISTURE IN SOUTHERLY WINDS
AHEAD OF FRONT WILL RESULT IN GRADUAL LOWERING OF VFR CLOUD BASES
THROUGH THIS EVENING...WITH DEVELOPMENT OF MVFR CEILINGS LIKELY
ALONG/BEHIND COLD FRONT OVERNIGHT. A SERIES OF RELATIVELY MINOR
UPPER LEVEL DISTURBANCES WILL RIPPLE OVERHEAD THROUGH SATURDAY...
WITH THE BEST COMBINATION OF DEEPER LIFT AND SATURATION INDICATED
BY VARIOUS MODELS TO OCCUR VERY LATE TONIGHT INTO SATURDAY
MORNING...BEFORE MID-LEVEL DRYING AND SINKING AIR DEVELOPS
SATURDAY AFTERNOON. MODELS DO DIFFER WITH DETAILS OF
SATURATION/LIFT JUXTAPOSITION HOWEVER...LENDING TO SOMEWHAT LOWER
CONFIDENCE IN IMPACTS TO CIG/VIS EARLY SATURDAY. TIMING BETWEEN
GUIDANCE IS REASONABLY SIMILAR HOWEVER...AND HAVE GENERALLY
MAINTAINED A CONSISTENT FORECAST TREND.

SOUTHWEST WINDS 10-15 KT THIS AFTERNOON WILL DECREASE AND SHIFT
MORE WESTERLY AS THE COLD FRONT APPROACHES EARLY THIS EVENING...
WITH COLD FROPA STILL LOOKING TO BE APPROXIMATELY 01-02Z AT KRFD
AND 03-04Z ACROSS THE CHICAGO TERMINALS. WIND EXPECTED TO
INITIALLY SHIFT NORTHWEST BEHIND THE FRONT...THEN VEER TO THE
NORTH-NORTHEAST EARLY SATURDAY WITH SPEEDS AGAIN IN THE 10-15 KT
RANGE THROUGH SATURDAY.

RATZER

//ORD AND MDW CONFIDENCE...UPDATED 20Z...

* HIGH CONFIDENCE IN WINDS.
* MEDIUM-HIGH CONFIDENCE IN CIG TRENDS.
* MEDIUM CONFIDENCE IN SNOW INTENSITY/TIMING AND CIG/VIS IMPACTS.

RATZER

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

SATURDAY NIGHT-MONDAY...VFR LIKELY.
TUESDAY...CHC OF RAIN DURING THE DAY AND SNOW DURING THE NIGHT.
WEDNESDAY-THURSDAY...VFR LIKELY.

MTF

&&

.MARINE...
236 PM CST

A COLD FRONT DROPPING ACROSS THE LAKE THIS EVENING WILL TURN WINDS
TO THE NORTHWEST AND THEN NORTH. HIGH PRESSURE APPROACHING FROM
THE UPPER MIDWEST WILL RELAX THE GRADIENT TOMORROW AND ALLOW WINDS
TO BACK WEST AGAIN. THE NEXT LOW MOVING ACROSS SOUTHERN CANADA
WILL TIGHTEN THE GRADIENT ON SUNDAY AND LIKELY SUPPORT A PERIOD OF
SOUTH TO SOUTHWEST GALE FORCE GUSTS SUNDAY AFTERNOON AND NIGHT.
THE LOW MOVES ACROSS THE NORTHERN LAKES AND INTO THE EASTERN LAKES
BY EARLY NEXT WEEK, TURNING WINDS WEST AGAIN. EXTENSIVE ICE
COVERAGE ACROSS THE LAKE WILL CONTINUE TO INHIBIT WAVE GROWTH
CONSIDERABLY.

LENNING

&&

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

$$

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