Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 261540 AAA
AFDMKX

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI
940 AM CST THU FEB 26 2015

.UPDATE...

A LAKE EFFECT SNOW ADVISORY IS IN EFFECT FOR RACINE AND KENOSHA
COUNTIES UNTIL 16Z THIS MORNING. LOOKS LIKE THE LAKE EFFECT SNOW
SQUALL IS STARTING TO SHIFT OFF TO THE EAST AS THE WINDS HAVE
STARTED BACKING TO A MORE NORTHWEST DIRECTION. THIS SHOULD HELP
MOVE THE SNOW SQUALL TO THE SOUTHEAST. MESO MODELS ALSO INDICATE
THE SNOW SQUALL WILL TAPER OFF RAPIDLY AND MOVE OUT OF THE
FORECAST AREA LATER THIS MORNING. EASTERN PORTIONS OF RACINE AND
KENOSHA WILL STILL BE DEALING WITH SOME LIGHT TO MODERATE SNOW FOR
THE NEXT HOUR OR SO.

&&

.AVIATION/18Z TAFS/...

MVFR CONDITIONS WILL PERSIST INTO THE AFTERNOON AS SOME LOW CLOUDS
WILL STICK AROUND THE AREA. ENW SHOULD SEE THE CURRENT LAKE
EFFECT SNOW SQUALL BAND QUICKLY SHIFT OFF TO THE EAST THIS MORNING.
OTHERWISE...EXPECT SOME LOW LEVEL CLOUDS...MAINLY FEW TO SCT WILL
PREVAIL THIS AFTN. SOME BKN SKIES COULD OCCUR AS LOW LEVEL LAPSE
RATES STEEPEN THIS AFTN. WINDS WILL STAY AT MORE NORTHERLY
DIRECTION THIS AFTN AND SHIFT MORE TO THE WEST AS ARCTIC HIGH
PRESSURE WILL ONCE AGAIN MOVE INTO THE REGION. COLD TEMPERATURES
WILL RETURN LATER TONIGHT. HOWEVER...WINDS SHOULD BE FAIRLY LIGHT
TONIGHT.

&&

.PREV DISCUSSION... /ISSUED 527 AM CST THU FEB 26 2015/

UPDATE...DECIDED TO EXTEND LAKE EFFECT SNOW ADVY FOR MILWAUKEE CO
UNTIL 14Z AND RACINE/KENOSHA COUNTIES UNTIL 16Z. KMKX/TMKE RADARS
SHOW ENHANCED LAKE BAND CONTINUING TO REGENERATE AND EXTENDS ABOUT
30 MILES NORTHEAST OF KMKE AND IS MOVING STEADILY SSW AT 20KTS.
THIS WILL PROBABLY BE THE LAST ROUND OF HEAVIER SNOW SHOWERS IN
SOUTHEAST MKE COUNTY BUT MAY STILL CLIP ERN RACINE/KENOSHA
COUNTIES THROUGH LATE MRNG. LATEST RAP SHOWS ENHANCED CONVERGENCE
AND OMEGA WEAKENING AND SLIDING SOUTHEAST OF KENOSHA CO BY LATE
MRNG.

&&

.TODAY...FORECAST CONFIDENCE IS MEDIUM.

PULLED TRIGGER ON LAKE EFFECT SNOW ADVY FOR THREE SOUTHEAST
COUNTIES EARLIER. OBSERVER IN OAK CREEK HAD REPORTED 4 INCHES OF
FLUFF BEFORE LAKE BAND HAD DEVELOPED. AROUND 07Z...IMPRESSIVE LAKE
EFFECT ENHANCED BAND RAPIDLY DEVELOPED OVER THE NEAR SHORE WATERS
AND SPREAD INLAND BY 0730Z. THIS WAS WHEN THE STRONGEST LOW LEVEL
CONVERGENCE AND PEAK LIFT WERE TO OCCUR OVER THE NEARSHORE
WATERS...SPREADING INLAND THRU PARTS OF THE THREE COUNTIES.

WITH BAND ORIENTATED NNE TO SSW AND MOVING TO THE SSW...HIGH SNOW
LIQUID RATIOS WOULD RESULT IN ADDITIONAL 1 TO 3 INCHES...ADDING TO
THE ALREADY 1 TO 3 INCHES THAT HAD ALREADY OCCURRED OVER MUCH OF
THE AREA.

LATEST RAP13 CONTINUES TO SHOW OMEGA LINGERING OVER SE MKE COUNTY
UNTIL ABOUT 14Z AND ERN RAC/KEN COUNTIES UNTIL 15Z OR SO. HOWEVER
DURING THIS TIME...LOW LEVEL FLOW BEGINS BACKING MORE TO THE NORTH
TO NORTHEAST...DECREASING FETCH AND LOW LEVEL RH ALSO DECREASES.
MAY NEED TO EXTEND LAKE EFFECT SNOW ADVY FOR AN HOUR OR TWO
PENDING STRENGTH OF LAKE BAND.

OTHERWISE...GRADUAL CLEARING SHOULD CONTINUE AS DRIER AIR SLIDES
ACROSS SRN WI TODAY. MAY BE SOME LINGERING SC FOR A TIME THIS AFTN
DUE TO LINGERING LOW LEVEL RH FLOW AND STEEP LOW LEVEL LAPSE
RATES.

.TONIGHT...FORECAST CONFIDENCE IS HIGH.

HIGH PRESSURE RIDGE AXIS REMAINS WEST OF WI OVERNIGHT TONIGHT AS
SHORT WAVE RIDGING SETTLES IN. INCREASING SUBSIDENCE SHOULD CLEAR
SKIES OVERNIGHT AS LOW LEVEL FLOW TURNS NORTHWEST. WITH LAKE
SUPERIOR PRETTY WELL ICE-COVERED...NOT THINKING MUCH THREAT OF
LAKE CLOUDS FROM THE NORTH.

ENOUGH MIXINESS OF 3 TO 5 KTS OVERNIGHT...AND OVERNIGHT LOWS FROM
4 TO 12 BELOW...TO RESULT IN A THREE HOUR WINDOW OF WIND CHILLS
AROUND 20 BELOW. WL LET DAY SHIFT MAKE FINAL DECISION ON WIND
CHILL ADVY.

.SHORT TERM...FRIDAY THROUGH SUNDAY...FORECAST CONFIDENCE IS
MEDIUM.

MODELS ARE IN GOOD AGREEMENT WITH TAKING ARCTIC HIGH PRESSURE FROM
WESTERN IOWA TO NORTHERN OHIO FRIDAY AND FRIDAY NIGHT. THE HIGH
WILL BRING QUIET WEATHER BUT CONTINUED COLD TEMPERATURES. GIVEN
MOSTLY CLEAR SKIES AND STRONG INVERSION JUST ABOVE THE
SURFACE...COULD SEE RADIATIONAL COOLING WITH LOWS EVEN COLDER THAN
CURRENTLY FORECAST FRIDAY NIGHT.

WIND CHILLS AGAIN HOVER AROUND 20 BELOW ZERO FOR A COUPLE
HOURS...THOUGH WINDS MAY BE TOO LIGHT IF DECOUPLING OCCURS. LATER
SHIFTS CAN EVALUATE NEED FOR WIND CHILL ADVISORY.

WARM AIR ADVECTION SLOWLY DEVELOPS ACROSS THE AREA SATURDAY INTO
SATURDAY NIGHT...AS THE HIGH MOVES FURTHER EAST OF THE REGION.
DEEP MOISTURE SHIFTS NORTHEASTWARD INTO THE AREA SATURDAY
NIGHT...ALONG WITH INITIAL 500 MB VORTICITY MAXIMUM. SURFACE COLD
FRONT THEN SHIFTS EASTWARD THROUGH THE REGION SUNDAY. TIMING OF
THE FRONTAL PASSAGE VARIES SOMEWHAT ON THE MODELS. UPWARD VERTICAL
MOTION SATURDAY NIGHT AND SUNDAY IS WEAK TO MODEST...THOUGH DOES
TAP DENDRITE SNOW GROWTH ZONE.

SREF PROBABILITIES OF MEASURABLE PRECIPITATION ARE OVER 90
PERCENT FOR SATURDAY NIGHT. THUS...RAISED POPS ESPECIALLY LATER
SATURDAY NIGHT...WITH LIKELY VALUES IN THE SOUTHWEST COUNTIES. MAY
NEED EVEN HIGHER POPS SATURDAY NIGHT INTO SUNDAY MORNING IN LATER
FORECASTS...IF MODELS REMAIN CONSISTENT. COULD SEE 1 TO 2 INCHES
OF SNOW ACCUMULATION NORTH...TO 2 TO 3 INCHES SOUTH...HIGHEST
AMOUNTS FAR SOUTHEAST.

.LONG TERM...SUNDAY NIGHT THROUGH WEDNESDAY...FORECAST CONFIDENCE
IS MEDIUM.

MAIN ISSUE THIS PERIOD WILL BE SYSTEM FOR TUESDAY AND
PRECIPITATION AMOUNTS/TYPES. GFS/ECMWF ARE IN SOMEWHAT BETTER
AGREEMENT WITH THE SURFACE LOW TRACK. THEY TAKE LOW FROM CENTRAL
KANSAS TO CENTRAL ILLINOIS TUESDAY...THEN INTO THE EASTERN GREAT
LAKES REGION TUESDAY NIGHT. GOOD AMOUNT OF WARM AIR ADVECTION
OCCURS MONDAY NIGHT INTO TUESDAY...WITH STRONG MOISTURE ADVECTION
AND A 500 MB VORTICITY MAXIMUM PASSAGE INTO TUESDAY NIGHT.

MODELS SHOWING THE BEST UPWARD VERTICAL MOTION OVER THE AREA
TUESDAY. GFS FORECAST SOUNDINGS ARE SUGGESTING SOME MIXINESS OF
FREEZING RAIN/SLEET IN THE FAR SOUTH AND SOUTHEAST TUESDAY. RAISED
POPS FOR MONDAY NIGHT INTO TUESDAY NIGHT...HIGHEST ON TUESDAY.
SEVERAL INCHES OF SNOW ARE POSSIBLE...WITH SLEET/FREEZING RAIN
POSSIBLE...SO STAY TUNED.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...LAKE EFFECT SNOW ADVISORY UNTIL 10 AM CST THIS MORNING FOR
     WIZ071-072.

LM...SMALL CRAFT ADVISORY UNTIL 10 AM CST THIS MORNING FOR LMZ645-646.

&&

$$
UPDATE...JTS
TODAY/TONIGHT AND AVIATION/MARINE...MBK
FRIDAY THROUGH WEDNESDAY...WOOD



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