Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 260340
AFDMKX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI
940 PM CST WED FEB 25 2015

.UPDATE...LAKE EFFECT SNOW SHOWERS WILL GET BETTER ORGANIZED
DURING THE OVERNIGHT AS A NELY 1000-850 MB FLOW INCREASES TO 20
KTS AND LAKE TO 850 MB TEMP DIFFERENCES REACH 20C. MESOSCALE
MODELS ARE SHOWING THE MOST ENHANCED BANDING OVER SE MKE COUNTY
INTO RAC COUNTY. THE SNOW BAND WILL THEN BEGIN TO SHIFT SEWD AFTER
10Z AND MOSTLY EXIT EASTERN RACINE AND KENOSHA COUNTIES BY 15Z.
WENT WITH A 2-3 INCH FORECAST OVER THESE AREAS USING GUIDANCE
FROM THE LAKE EFFECT SNOW CHART.


&&

.AVIATION/06Z TAFS/...VFR CONDITIONS WILL PREVAIL FOR KMSN AND
KUES FOR THU AND THU NT AS RELATIVELY DRY AND COLD AIR MOVES INTO
THE REGION. FOR FAR SE WI INCLUDING KMKE AND KENW...LAKE EFFECT
SNOW SHOWERS WILL BE PERSISTENT THU AM THROUGH ABOUT 12-15Z. CIGS
WILL MAINLY RANGE FROM 1.0-1.9 KFT ALTHOUGH BRIEFLY LESS THAN 1.0
KFT WITH THE HEAVIER BURSTS OF LAKE EFFECT SNOW. VARIABILITY IS
EXPECTED WITH THE VSBYS GIVEN THE SHOWERY NATURE OF LAKE EFFECT
SNOW BUT WILL MAINLY RANGE FROM 1-2SM...SOMETIMES LOWER OR HIGHER.
VFR CONDITIONS WILL THEN PREVAIL BY LATE MORNING OR EARLY
AFTERNOON OVER FAR SE WI AND CONTINUE THROUGH THU NT.


&&

.PREV DISCUSSION... /ISSUED 306 PM CST WED FEB 25 2015/

TONIGHT - CONFIDENCE...MEDIUM
SNOW CONTINUES TO SLOWLY SHIFT EASTWARD THROUGH SRN WI OVERCOMING
THE DRY LOW LAYERS THAT WERE EVIDENT ON 12Z GRB SOUNDINGS. WITH THE
SATURATION HAS COME VSBYS DOWN TO 1/2 TO 3/4SM AT TIMES...ESP SW OF
KMSN. RADAR ANIMATION CONTINUES TO SUPPORT THE MODEL TRENDS OF
KEEPING BEST ACCUMS ALONG AND SOUTH OF I-94 CORRIDOR WITH THE
SYSTEMS BEST ACCUMS MISSING US ACROSS NORTHERN ILLINOIS. SO WILL
HAVE HIGHEST POPS AND ACCUMS IN THE SOUTHERN COUNTIES. THE OTHER
CONSIDERATION IS THE LAKE EFFECT POTENTIAL. TERMINAL DOPPLER HAS
BEEN SHOWING THE BAND HOLDING OFFSHORE THOUGH RAP SOUNDINGS DO SHOW
ONSHORE COMPONENT WITH DELTA T VALUES OF AROUND 21. EQUILIBRIUM
LEVELS ALSO PUSH 6K FEET. HAVE BUMPED UP SOME AMOUNTS A BIT ESP FROM
SE MKE CNTY THROUGH ERN RAC/ENW COUNTIES. WHILE ICE IS EVIDENT
THERE ARE ENOUGH BREAKS/SLUSHINESS TO ALLOW THE NECESSARY
INSTABILITY TO BE REALIZED FOR THE LAKE EFFECT. SO OVERALL 1-2 OF
SYSTEM SNOW FOR MAINLY SRN HALF OF THE CWA WITH SOME ISOLD 3 INCH
AMOUNTS ADJACENT TO THE LAKE SOUTH OF KMKE TO WI/IL BORDER KENW DUE
TO ADDED INFLUENCE OF LAKE EFFECT.

THURSDAY - CONFIDENCE...MEDIUM
STILL SEEING SOME LINGERING ONSHORE COMPONENT DURING THE MORNING HOURS
SO THE GFS/NAM IDEA OF HANGING ONTO SOME LES POTENTIAL SEEMS REASONABLE.
ENOUGH NNW FETCH ESTABLISHED BY MIDDAY AND INTO THE AFTERNOON HOURS TO
REMOVE LES FROM GRIDS. 850 THERMAL TROUGH WILL BE IN PLACE WITH 925
TEMPS -17C TO -19C. SO MUCH BELOW NORMAL TEMPS EXPECTED WITH HIGHS UPPER
SINGLE DIGITS/LOW TEENS.

SHORT TERM...FRIDAY THROUGH SATURDAY NIGHT...FORECAST CONFIDENCE
IS MEDIUM.

HIGH PRESSURE MOVES INTO THE REGION FRIDAY AND WINDS WILL BACK
FROM A MORE NORTHERLY DIRECTION TO THE NORTHWEST AND WEST BY
FRIDAY AFTERNOON. HIGHS FRIDAY WILL GENERALLY BE BETWEEN 10 AND 15.
THIS AREA OF HIGH PRESSURE SHOULD KEEP CONDITIONS QUIET THROUGH
THE DAY SATURDAY.

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

ECMWF IS PROGGING A POTENT 140KT 250 MB JET STREAK TO TRANSLATE
INTO THE REGION EARLY SUNDAY. SOUTHERN WISCONSIN WILL BE IN THE
LEFT EXIT REGION WITH SOME ASSOCIATED UPPER LEVEL DIVERGENCE. THIS
ALONG WITH A 500 MB SHORTWAVE DISTURBANCE LOOKS TO BRING A SYSTEM
INTO THE REGION FROM THE SOUTHWEST. THE GFS LOOKS TO BE MORE
BULLISH WITH THE 500 MB ENERGY THAN THE ECMWF ACCORDING TO THE
LATEST RUNS. 850 MB WARM AIR ADVECTION AND SOUTHERLY WINDS WILL
HELP BRING IN MOIST LOW LEVEL AIR AS WELL. THE BULK OF THE QPF
AMOUNTS LOOK TO STAY FURTHER SOUTH...OUT OF OUR FORECAST
AREA...BUT NOT BY MUCH. ALSO...THE ECMWF IS SLIGHTLY FASTER THAN
THE GFS REGARDING THE ONSET OF THE PRECIPITATION BY A FEW HOURS.
STILL SOME UNCERTAINTY AS TO THE LOCATION OF THE MAIN QPF AXIS.

ANOTHER SHOT OF COLD AIR ALONG WITH SOME NORTHWEST WINDS AS HIGH
PRESSURE RETURNS TO THE REGION MONDAY ONCE THE SUNDAY SYSTEM
MOVES OUT.

ANOTHER SYSTEM LOOKS TO MOVE INTO THE REGION FOR TUESDAY AS
ANOTHER PULSE OF 500 MB POSITIVE VORTICITY ENERGY TRANSLATES INTO
THE REGION...ALONG WITH BEING IN THE RIGHT ENTRANCE REGION OF A
STRONG 180KT 250 MB JET STREAK AND UPPER LEVEL DIVERGENCE. THERE
IS STILL MUCH UNCERTAINTY WITH THIS PARTICULAR EVENT. CURRENT SNOW
ACCUMULATIONS COULD BE BETWEEN 5 AND 6 INCHES ACROSS THE FORECAST
AREA. AT THE MOMENT...THE TIMING OF THE BULK OF THE SNOW WILL BE
DURING THE DAY TUESDAY. WE WILL CONTINUE TO MONITOR THE
PRECIPITATION TIMING AND AMOUNTS.

AVIATION/00Z TAFS/...WATER VAPOR SHOWS SHORTWAVE RIDING EAST
FROM IA. MEANWHILE SURFACE LOW DROPPING SE INTO ERN KS/WRN MO.
MODELS IN GOOD AGREEMENT IN SPREADING SNOW ACROSS REMAINDER OF SE
WI THIS AFTN AND EVE WITH ONSHORE COMPONENT LEADING TO SOME LAKE
EFFECT SNOWS AS WELL. SO EXPECTING SOME IFR CIGS AND PERHAPS SOME
LIFR VSBYS...BUT MOSTLY IFR VSBYS. LAKE EFFECT WRAPS UP THURSDAY
MORNING. SO OVERALL 1-2 OF SYSTEM SNOW FOR MAINLY SRN HALF OF THE
CWA WITH SOME ISOLD 3 INCH AMOUNTS NEAR LAKE MI DUE TO ADDED
INFLUENCE OF LAKE EFFECT.

MARINE...WIND GUSTS WL GET CLOSE TO SMALL CRAFT ADVY FOR A TIME
TONIGHT AS PRESSURE GRADIENT TIGHTENS DUE TO LOW PRESSURE PASSING
WELL SOUTH OF THE AREA.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...NONE.
LM...NONE.
&&

$$

UPDATE...GEHRING
TONIGHT/THURSDAY AND AVIATION/MARINE...COLLAR
THURSDAY NIGHT THROUGH WEDNESDAY...JTS


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