Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 290354
AFDMKX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI
954 PM CST WED JAN 28 2015

.UPDATE...

PULLED BACK POPS THROUGH 06Z TO REFLECT THE NEED FOR DEEPER
SATURATION BEFORE PCPN CAN START OVER CWA. WHILE REGIONAL RADAR
RETURNS SHOW SCATTERED AREAS OF LOW REFLECTIVITY OVER THE ENTIRE
REGION INCLUDING SRN WI...THE ONLY GROUND TRUTH ARE DRIZZLE AND
UNKNOWN PCPN /UP/ REPORTS FROM OB SITES AROUND MSP AND NORTH OF
LA CROSSE. THESE REPORTS LINE UP WELL WITH PERSISTENT FOCUS FOR
THE LIGHT PCPN TO CROSS MAINLY CENTRAL WI OVERNIGHT ON HI-RES/
RAPID UPDATE MODELS. THIS AREA COULD CLIP THE FAR NORTHERN
COUNTIES. LEFT LIKELY POPS THERE FOR HIGH PROBABILITY OF
OCCURRENCE/LOW PROBABILITY OF MEASURING.

SOME ACCAS SPRINKLES ALSO REPORTED FROM AREA OF RADAR RETURNS IN
CENTRAL IL WITH CLOUD CEILINGS BETWEEN 9K AND 12K FT THAT WILL BE
MOVING ACROSS THE NE IL OVERNIGHT AND COULD BRUSH THE FAR SE. WILL
NEED TO TAKE A CLOSER LOOK AT 00Z DATA TO SEE IF HIGHER POPS IN
THE EASTERN CWA NEED TO BE TRIMMED BACK TO THE NORTH.

HAVE UPDATED THE SPS TO CONTINUE THE POTENTIAL FOR SEEING SOME
FREEZING DRIZZLE/LIGHT FREEZING RAIN AHEAD OF THE LOW...WITH SOME
LIGHT SNOW...MIXED WITH SLEET EARLY THURSDAY MORNING IN THE COLD
AIR ADVECTION BEHIND THE LOW. WILL BE MONITORING UPSTREAM
CONDITIONS FOR THE NEED FOR AN ADVISORY IF AREAS OF FZDZ/FZRA
BECOME MORE EXPANSIVE..

&&

.AVIATION/06Z TAFS/...

CURRENT VFR CONDITIONS WILL RAPIDLY DROP TO MVFR FROM WEST TO
EAST AS INVERTED TROUGH EXTENDING NWD FROM LOW ENTERING NW IL
CROSSES SRN WI OVERNIGHT. STILL EXPECT TO SEE AT LEAST PATCHY
FREEZING DRIZZLE/POCKETS OF FREEZING RAIN WITH THIS FEATURE...BUT
FOCUS ON MAJORITY OF RAPID UPDATE MODELS AND THE LATEST NAM KEEPS
THE BETTER CHANCES NORTH OF TAF SITES. COLD AIR ON BACK SIDE OF
TROUGH WILL TURN THE LIGHT PCPN TO LIGHT SNOW...POSSIBLY MIXED
WITH SLEET BETWEEN 12Z AND 15Z BUT WITH LITTLE TO NO
ACCUMULATION. PCPN LOOKS TO END AFTER 15Z...BUT LATEST NAM
HINTING AT POCKETS OF FLURRIES IN THE AFTERNOON WITH STEEP LOW-
LEVEL LAPSE RATES AND LIFT FROM TRAILING MID-LEVEL IMPULSES
CROSSING THE REGION. WILL LEAVE OUT FOR NOW BUT KEEP MVFR CIGS IN
THROUGH THE REMAINDER OF THE DAY AS MODEL LOW-LEVEL RH FIELDS
INDICATE LOW DECK WONT BREAK UNTIL AFTER 00Z...AND POSSIBLY AFTER
03Z.

&&

.MARINE...

GUSTY S TO SE WINDS WILL CONTINUE INTO THE OVERNIGHT...EASING FOR
A TIME AROUND 12Z AS THE INVERTED TROUGH EXTENDING NORTH OF THE
LOW CENTER CROSSES WESTERN LAKE MICHIGAN. WINDS THEN TURN NW AND
INCREASE RAPIDLY BY 15Z BACK TO SMALL CRAFT ADVISORY LEVELS..WITH
A FEW GALE FORCE GUSTS POSSIBLE. NO CHANGES TO CURRENT SMALL
CRAFT ADVISORY.

 &&

.PREV DISCUSSION... /ISSUED 315 PM CST WED JAN 28 2015/

TONIGHT AND THURSDAY...CONFIDENCE - MEDIUM.

FOCUS IS ON PRECIP TYPE AND COVERAGE WITH PASSING LOW PRESSURE
TRACKING TO OUR SOUTH LATER TONIGHT INTO THURSDAY MORNING. CONSENSUS
IS TO GO THE SPS ROUTE AS SURFACE TEMPS AND LONGEVITY OF WARM LAYER
KEEP CONFIDENCE OF AN ADVISORY IN THE LOW CATEGORY AT THIS TIME.
PLENTY OF WARM AIR ALOFT WITH 17C AT KOMA ON 12Z SOUNDING. SINCE
TEMPS ONLY GOT CLOSE TO MOS VALUES WE ARE NOT THAT FAR FROM
FREEZING. MESO MODELS SHOW ONLY SPOTTY PRECIP COVERAGE THUS THE LOW
POPS FROM THE CONSSHORT OUTPUT. MEANWHILE GLOBAL MODELS SHOWING MORE
UNIFORM LIGHT PRECIP ACROSS SRN WI WITH HIGHER POPS. WARM LAYER
REACHES THE PEAK AROUND 6Z...THOUGH MODELS LARGELY DRY UNTIL THAT
POINT WITH BETTER PRECIP POTENTIAL ASSOCIATED WITH DEF ZONE OF
SHORTWAVE AND BETTER DEVELOPED SURFACE LOW PASSING TO OUR SOUTH.
LINGERING LIGHT SNOW/FLURRIES GRADUALLY DIMINISH THURSDAY MORNING.
LOW LEVEL RH PROGS/MOS AND CYCLONIC CURVATURE OF UPPER FLOW SUGGESTS
CLOUDS WILL LIKELY STICK AROUND FOR MUCH OF THE AREA.

THURSDAY NIGHT THROUGH SATURDAY...CONFIDENCE - MEDIUM.

A QUIET PERIOD IS EXPECTED WITH PASSING HIGH CLOUDINESS ON FRIDAY
WITH THICKER CLOUDS EXPECTED ON SAT. BLUSTERY NORTHWEST WINDS WILL
CONTINUE TO PULL COLDER AIR INTO SRN WI THU NGT WITH 925H TEMPS
FALLING TO AROUND -14C...AHEAD OF APPROACHING HIGH PRESSURE. COLD
THERMAL TROF LINGERS INTO FRIDAY WITH SLIGHT RECOVERY IN TEMPS IN
THE AFTN.  FILTERED SUNSHINE AND LIGHTER WINDS SHOULD HELP DAYTIME
TEMPS RECOVER INTO THE LOWER 20S.

BRISK NW WINDS ALOFT WILL CARRY MID-LEVEL SHORT WAVE ACROSS CENTRAL
WI LATER FRI NGT...WHICH GRAZES NORTHEAST CWA.  HESITANT AT THIS
POINT TO ADD ANY POPS AS GFS AND ECMWF SHOWING MUCH DRIER COLUMN
BELOW 5K FEET VS NAM.  WITH CORE OF Q-VECTOR CONVERGENCE AND DEEPER
RH REMAINING FARTHER NORTH...WL CONTINUE DRY FORECAST.

WEAK SURFACE TROF PASSES THRU ON SATURDAY...HOWEVER COLUMN REMAINS
DRY IN THE LOW LEVELS.  DROPPED SCHC POPS AND EXPECT WARMER DAYTIME
TEMPS DUE TO PERIOD OF LOW LEVEL WARM AIR ADVECTION AHEAD OF TROF.

SATURDAY NIGHT THROUGH WEDNESDAY...CONFIDENCE - MEDIUM.

MEDIUM RANGE GUIDANCE IN REASONABLE AGREEMENT ON SOUTHWEST CONUS
UPPER LOW CONTINUING TO SHIFT SOUTH INTO NRN MEXICO EARLY IN THE
WEEKEND AS STRONGER MID-LEVEL SHORT WAVE MOVES FROM SOUTHWEST CANADA
ACROSS THE ROCKIES INTO THE CENTRAL PLAINS BY SAT NGT.
MEANWHILE...WEAK TROF THAT PASSED THROUGH SRN WI ON SAT WL HAVE
RESULTED IN A TIGHTENING LOW LEVEL BAROCLINIC ZONE IN THE AREA.
PWAT VALUES TO INCREASE TO AROUND 0.4 INCH WHICH IS APPROACHING 75TH
PERCENTILE FOR FEB 1.

CENTRAL PLAINS SHORT WAVE EXPECTED TO STRENGTHEN AS IT TRACKS EWD
ACROSS THE CENTRAL MS VALLEY INTO THE OH/TN VALLEY REGION SUN INTO
SUN NGT.  HOWEVER TREND FROM BOTH GFS AND EWCMF HAS BEEN KEEPING THE
FLOW MORE PROGRESSIVE WITH THE SHORT WAVE REMAINING WEAKER AS IT
SPEEDS OFF TO THE EAST LATER SUN/SUN NGT.  THIS GUIDANCE EMPHASIZING
DRIER NORTHERLY FLOW AS LARGE HIGH PRESSURE NOSES INTO THE UPPER
UPPER MIDWEST FROM CANADA.  LATEST GEM MEANWHILE CONTINUES WETTER
AND SNOWIER OUTLOOK FOR SUNDAY.  DUE TO INCREASING UNCERTAINTY...WL
CONTINUE CHANCE POPS AND DECREASE POTENTIAL SNOW AMOUNTS TO SEVERAL
INCHES. COLDER AIR TO BE FIRMLY ENTRENCHED OVER THE REGION SO WOULD
BE MAINLY SNOW OVER THE WEEKEND.

LOOKS COLDER EARLY NEXT WEEK HELPED ALONG BY FRESH SNOW COVER.
NORTHWEST UPPER FLOW EXPECTED TO TURN MORE ZONAL BY MID-WEEK WHICH
SHOULD ALLOW MORE SEASONAL TEMPS TO RETURN.  WEAK IMPULSES CAUGHT IN
BRISK WEST TO NORTHWEST FLOW MAY BRING SEVERAL PERIODS OF -SN TO THE
AREA FROM MON THRU WED.

AVIATION/00Z TAFS/...

IMPRESSIVE WAA WITH KOMA AT 17C AND KGRB AT -2C. CIRRUS RIDING ATOP
THE STRATUS DECK IN SC WI. STRATUS DECK HAS LIFTED NORTH FROM SC WI
THOUGH CIRRUS CONTINUES TO SPILL ACROSS AND IS THICKENING UP. STILL
LOOKING FOR A RENEWED SURGE OF IFR/LIFR CIGS AND SOME IFR VSBYS
LATER TONIGHT INTO EARLY THURSDAY AS LOW PRESSURE TRACKS SOUTH OF
WI. MODELS SETTLING ON ABOUT 0.04 TO 0.06 IN LIQUID PRECIP. LITTLE
SATURATION IN DENDRIDIC GROWTH ZONE SO SURFACE TEMPS WILL BE KEY FOR
ANY FREEZING PRECIP. DOES APPEAR TO BE A WINDOW FOR THAT POTENTIAL
ESPECIALLY SINCE TEMPS ARE STRUGGLING TODAY WITH PRONOUNCED LOW
LEVEL INVERSION AND CLOUD COVER. COLD ADVECTION DOES COMMENCE LATER
TONIGHT SO WARM LAYER WILL BE SLOWLY ERODING WITH TIME SO A PERIOD
OF LIGHT SNOW POSSIBLE BEFORE PRECIP SHIFTS EAST OF WI THURSDAY
MORNING. EXPECT IMPROVEMENT IN CIGS AS DAY GOES ON WITH SOME DRYING
AFTER PRECIP...THOUGH LLVL RH PROGS KEEP CLOUD COVER IN PLACE FOR
MOST OF THE DAY.


MARINE...

TIGHTENING PRESSURE GRADIENT AHEAD OF APPROACHING LOW PRESSURE TROF
HAS CONTRIBUTED TO STEADILY INCREASING SOUTH TO SOUTHEAST WINDS
SINCE LATE MORNING.  WINDS NOW FLIRTING WITH SMALL CRAFT ADVISORY
CRITERIA AT LAKESHORE STATIONS.  ORE CARRIER PARKED IN MKE HARBOR
REPORTING SUSTAINED WINDS AT 20KTS.  STRONGEST WINDS EXPECTED NOW
THRU 03Z OR SO WITH GUSTS POTENTIALLY UP TO 30KTS.  ONSHORE
COMPONENT TO WINDS REEULTING IN BUILDING WAVES.

AS LOW PRESSURE TROF APPROACHES WESTERN LAKE MI LATER TNGT AND
PASSES TO THE EAST EARLY THU...WINDS WILL DECREASE AND VEER TO THE
NORTHWEST UPON TROF PASSAGE.  THE NORTHWEST WINDS WILL BECOME GUSTY
LATER THU MRNG AND LIKELY GUST TO 30-32 KTS AT TIMES AWAY FROM
SHORE.  HOWEVER AS WINDS TURN OFFSHORE...WAVE HEIGHTS WILL SLOWLY
DECREASE LATE TNGT THRU THU.  STATUS QUO ON TIMING WITH CURRENT SMALL CRAFT
ADVY.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...NONE.
LM...SMALL CRAFT ADVISORY UNTIL 6 AM CST FRIDAY FOR LMZ643>646.

&&

$$

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


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