Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 250338 AAA
AFDMKX

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI
938 PM CST WED DEC 24 2014

.UPDATE...

SHOULD SEE THE LAST BAND OF MIXED PRECIPITATION OVER FAR EASTERN
WISCONSIN...MAINLY VERY LIGHT SNOW MIXED WITH RAIN NORTH OF
I-94...WITH DRIZZLE...LIGHT RAIN...AND SOME SLEET FROM I-94
SOUTH...EXITING OUT OVER LAKE MICHIGAN BETWEEN 1030 PM AND 11 PM.

AIR TEMPERATURES ARE STILL ABOVE FREEZING BUT WILL SLOWLY FALL TO
AROUND 30F...THOUGH NOT UNTIL WELL AFTER THE PCPN HAS GONE. WITH ROAD
SURFACE TEMPS STILL WELL ABOVE 32F LITTLE IN THE WAY OF ICING
EXPECTED. WEAK RETURNS ON UPSTREAM RADARS INDICATE WE COULD SEE A
FEW SNOW FLURRIES AHEAD OF A WEAK RIPPLE CROSSING IL OVERNIGHT
INTO THURSDAY MORNING...BUT NO ACCUMULATIONS EXPECTED.

&&

.AVIATION/06Z TAFS/...

ANY MIXED PCPN SHOULD BE OUT OF KMKE AND KENW BY 0430Z. CIGS ARE
CLIMBING TO ABOVE 1K FT...WITH SOME MVFR CIGS IN THE WESTERN
FORECAST AREA. LATEST RAP SOUNDINGS SHOW CIGS AT 2K FT OR HIGHER
WILL BE SHORT-LIVED SO WILL KEEP CIGS AT FUEL ALTERNATE MINIMUMS
THROUGH THE OVERNIGHT...THEN RAISE THEM TO MVFR MID MORNING...AND
VFR BY LATE MORNING. EASTERN TAF SITES HAVE THE BEST CHANCE TO SEE
CLOUDS SCATTER OUT THURSDAY AFTERNOON...WITH OVERCAST SKIES
RETURNING THURSDAY EVENING WITH WARM ADVECTION ON DEVELOPING SW
WINDS AHEAD OF DEEPENING WESTERN TROUGH. NAM GUIDANCE WANTS TO
DROP CIGS BACK TO FUEL ALTERNATE MINIMUMS BY 03Z AT KMSN AND
BETWEEN 06Z AND 09Z AT KMKE...EVEN AS LOW AS IFR BY 09Z 12/26 AT
KMKE. WILL KEEP CIGS NO LOWER THAN 1000 TO 1500 FT FOR NOW.

&&

.MARINE...

LAKESHORE OB SITES NOT GUSTING TO CRITERIA...BUT LATEST RAP AND
00Z NAM SOUNDINGS OVER THE WATER INDICATE MIXING UP TO 24-27 KNOT
WINDS AT LEAST INTO EARLY THURSDAY MORNING. WILL LET ADVISORY
CONTINUE AND LET OVERNIGHT CREW RE-ASSESS.

&&

.PREV DISCUSSION... /ISSUED 320 PM CST WED DEC 24 2014/

TONIGHT AND CHRISTMAS DAY...CONFIDENCE - HIGH

SURFACE TEMPERATURES ARE EXPECTED TO MAINLY STAY ABOVE FREEZING
DURING THE TIME OF PRECIP CHANCES. WITH SATURATION ONLY UP TO
ABOUT -10C AND MUCH OF THE SATURATED LAYER BELOW FREEZING...PRECIP
TYPE WILL DEPEND ON ICE CRYSTAL FORMATION. SEEMS A RAIN/SNOW MIX
IS THUS THE WAY TO GO THROUGH THE REMAINDER OF THIS EVENT. EITHER
WAY...PRECIP AMOUNTS WILL BE VERY LIGHT...LIKELY STRUGGLING TO
MEASURE RAIN OR SNOW MOST PLACES.

LOW CLOUDS WILL LIKELY LINGER THROUGH AT LEAST TONIGHT...WITH A
CHANCE FOR SOME SUNSHINE BY TOMORROW AFTERNOON. THE SUN MAY BE
FILTERED THROUGH HIGH CLOUDS...BUT SUN OF ANY FORM WOULD PROBABLY BE
WELCOME AFTER THIS RECENT STRETCH OF CLOUDS. WITH THE THE POSSIBLE
AFTERNOON SUN...MILD SOUTHERLY LOW LEVEL FLOW...AND INCREASING TEMPS
ALOFT...LOOKS LIKE HIGHS WILL BE UP NEAR 40 FOR CHRISTMAS.

THURSDAY NIGHT THROUGH SATURDAY...CONFIDENCE - MEDIUM.

SHORT TERM GUIDANCE IN FAIR AGREEMENT ON INCOMING SHORT WAVE TROF
INTO THE PACIFIC NORTHWEST DIGGING SOUTHEAST AND AMPLIFYING.  ONCE
WEAK HIGH PRESSURE PASSES BY THE EAST...INCREASING SOUTHERLY WINDS
AHEAD OF UPSTREAM TROFFING WILL PULL DEEPER COLUMN MOISTURE
NORTHWARD INTO THE REGION THURSDAY NIGHT INTO SATURDAY.  COLUMN PWAT
VALUES INCREASE SLIGHTLY TO AROUND ONE HALF INCH DURING THIS
TIME...WHICH IS AROUND THE 75TH PERCENTILE FOR LATE DECEMBER.

WHILE CONFIDENCE IS HIGHER ON MILDER TEMPS AND DEEPER
MOISTURE...SHORT TERM GUIDANCE DIFFER ON TIMING OF EJECTION OF
UPSTREAM TROF ACROSS THE PLAINS.  PREFERRING SIMILAR NAM AND ECMWF
SOLUTIONS WHICH HAVE BETTER Q-VECTOR CONVERGENCE AND SYNOPTIC SCALE
FORCING AFFECTING SRN WI LATER FRIDAY NIGHT INTO SATURDAY.  HENCE
PREFER SLIGHTLY SLOWER SOLUTION WHICH KEEPS WARMER LOW LEVEL THERMAL
BOUNDARY ACROSS SRN WI INTO SATURDAY...RESULTING IN A BETTER CHANCE
FOR MORE LIQUID PRECIP IN THE EAST.  SOME WEAK LOW TO MID LAYER
FRONTOGENETICAL FORCING ENHANCING SYNOPTICS...SO WL BUMP UP POPS TO
HIGH CHANCE CATEGORY FOR SAT MRNG.  TEMPS EXPECTED TO BE ABOVE
FREEZING MOST OF THE DAY SO ONLY LIGHT SNOW ACCUMULATIONS...IF
ANY...EXPECTED.

SATURDAY NIGHT THROUGH WEDNESDAY...CONFIDENCE - MEDIUM.

WILL NEED TO CARRY SMALL POPS FOR LINGERING PRECIP INTO SATURDAY
EVENING AS BOTH ECMWF AND GEM IN AGREEMENT ON SLOWER EWD PROGRESS OF
SFC TROF AS WELL AS WEAKENING ELONGATED ELEVATED TROFFING.  HOWEVER
EXPECT THIS FEATURE TO SLIDE OFF TO THE EAST SAT NGT IN RESPONSE TO
UPSTREAM KICKER WAVE MOVING ACROSS THE WESTERN CONUS OVER THE
WEEKEND.  COLDER...MORE SEASONAL TEMPERATURES ARE EXPECTED TO RETURN
BEHIND THE DEPARTING SYSTEM FOR THE WEEKEND.

WEAK HIGH PRESSURE BETWEEN THESE TWO FEATURES WILL RESULT IN DRY BUT
COLDER CONDITIONS FOR SUNDAY.  DURING THIS PERIOD...INCREASING
NORTHWEST WINDS ACROSS SOUTHERN CANADA WILL BE PULLING COLDER AIR
INTO THE BORDER AREA...WHICH WILL BE POISED TO SURGE ACROSS THE
UPPER MIDWEST EARLY NEXT WEEK.

AN AMPLIFYING LONG WAVE TROF OVER THE CENTRAL CONUS IN RESPONSE TO
LOW PRESSURE MOVING ACROSS THE SOUTHEAST CONUS WILL ALLOW THE COLDER
AIR TO SURGE SWD AND AFFECT SRN WI HEADING INTO THE NEW YEAR.
HOWEVER STEERING FLOW ALOFT REMAINS MORE WESTERLY AS COLD AIR
SETTLES INTO THE REGION.  LAYER RH LOOKS LOW...BUT A WEAK WAVE
MOVING IN WESTERLIES MAY BRING A PERIOD OF -SN TO THE AREA MON AND
TUE.  925H TEMPS FALL TO AROUND -20C BY WED...WHICH WOULD RESULT IN
DAYTIME TEMPS IN THE SINGLE DIGITS AND TEENS WITH A LACK OF
SIGNIFICANT SNOW COVER.  SOME RECOVERY IN TEMP EXPECTED FOR NEW
YEARS DAY.

AVIATION/00Z TAFS/...

LATEST MODELS CONTINUE TO THE DOWNWARD TREND IN PRECIP
CHANCES...WITH NO APPRECIABLE RAIN OR SNOW EXPECTED THROUGH THE
REMAINDER OF THE DAY. STILL MAY SEE A LITTLE LIGHT SNOW OR RAIN AT
TIMES INTO THE EVENING HOURS AS THE UPPER THROUGH SWINGS THROUGH.

A FEW LOWER VISIBILITIES ARE LINGERING OUT THERE...BUT THESE SHOULD
CONTINUE TO IMPROVE THROUGH THE AFTERNOON. LOW CLOUDS WILL LIKELY
PERSIST INTO TONIGHT. SHOULD THEN SEE A RETURN TO VFR CONDITIONS BY
MID OR LATE THURSDAY MORNING.

MARINE...

THE SMALL CRAFT ADVISORY IN EFFECT FOR THIS EVENING THROUGH
CHRISTMAS MORNING IS LOOKING A BIT MORE MARGINAL...BUT STILL
PROBABLY WORTH KEEPING. BEST CHANCE FOR GUSTS TO 25 KNOTS WILL BE
TOWARD OPEN WATERS.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...NONE.
LM...SMALL CRAFT ADVISORY UNTIL NOON CST THURSDAY FOR LMZ643>646.

&&

$$

UPDATE...REM
TONIGHT/THURSDAY AND AVIATION/MARINE...DDV
THURSDAY NIGHT THROUGH WEDNESDAY...MBK


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