Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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000
FXUS63 KMKX 242119
AFDMKX

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

.TONIGHT AND CHRISTMAS DAY...CONFIDENCE - HIGH

SEEING LIGHT RADAR RETURNS INCREASING A BIT THIS AFTERNOON AS
EXPECTED...ALONG WITH A FEW OBS REPORTING MIXED PRECIP. THE CHANCE
FOR LIGHT MIXED PRECIP WILL CONTINUE THROUGH THE AFTERNOON AS AN
UPPER LEVEL TROUGH PUSHES THROUGH...ENDING FROM WEST TO EAST FROM
LATE AFTERNOON TO LATE EVENING.

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 FROM 6 PM CST THIS EVENING UNTIL NOON CST
THURSDAY FOR LMZ643>646.

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


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