Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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443
FXUS63 KMKX 140300
AFDMKX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI
900 PM CST SAT FEB 13 2016

.UPDATE...

00Z NAM VERY SIMILAR WITH SNOW AMOUNTS. THEREFORE WILL NOT CHANGE
FORECAST. SLOWED ARRIVAL OF SNOW A FEW HOURS...ESPECIALLY
SOUTHEAST...BUT WILL HAVE TO WATCH FOR SNOW SHOWERS/FLURRIES OFF
LAKE MICHIGAN AS SOUTHEAST WINDS DEVELOP.

&&

.AVIATION/06Z TAFS/...

EXPECT HIGH CLOUDS TO THICKEN AND LOWER TONIGHT. 700 MILLIBAR RH
ON THE INCREASE. SFC RIDGE AXIS POSITIONED ACROSS SOUTHEAST
WISCONSIN AT 06Z AND THEN INTO THE OH VALLEY LATER IN THE NIGHT.
LATEST MODELS CONTINUE TO SHOW SNOW SPREADING ACROSS SRN WI SUNDAY
MORNING IN RESPONSE TO INCREASING MOISTURE AND APPROACHING SHORTWAVE.
CONSIDERABLE LOW AND MID LEVEL DRY AIR SHOULD SATURATE RAPIDLY IN
A TOP/DOWN FASHION DURING THE MORNING AS VERTICAL MOTION FIELD
RAMPS UP WITHIN A DEEP DENDRITIC GROWTH ZONE. HARD TO ARGUE WITH
THE TRENDS IN MOS WITH CIGS/VSBYS SHOWING A LOWERING TREND TO IFR
LEVELS.

&&

MARINE...
SOUTHEAST WINDS EXPECTED TO INCREASE TO SMALL CRAFT ADVISORY
LEVELS ON SUNDAY AHEAD OF A LOW PRESSURE TROUGH. SATELLITE IMAGERY
DID SHOW SOME ICE COVERAGE...ESPECIALLY ACROSS THE SOUTHERN TWO
ZONES. WOULD STILL EXPECT THE ONSHORE FLOW TO LEAD TO SOME HIGHER
WAVES IN ICE FREE AREAS. WINDS ARE EXPECTED TO SHIFT SOUTHWEST
SUNDAY NIGHT AND DEPENDING ON THE MODEL COULD REMAIN GUSTY. SOME
POTENTIAL FOR A SLACKENING GRADIENT WITHIN THE TROUGH AXIS SO
ADVISORY MAY BE ABLE TO END SOONER DEPENDING ON LINGERING WAVE
ACTION.

ALSO EXPECT SOME MODERATE FREEZING SPRAY SUNDAY AFTERNOON INTO
EARLY SUNDAY NIGHT.

&&

.PREV DISCUSSION... /ISSUED 324 PM CST SAT FEB 13 2016/

SHORT TERM...TONIGHT...FORECAST CONFIDENCE IS MEDIUM

COLD HIGH PRESSURE WILL DOMINATE INTO THIS EVENING. RIDGE AXIS
SHIFTS EAST OF THE AREA AFTER 06Z WITH SOME UPTICK IN SOUTHERLY
SFC/925 FLOW NOTED IN THE PROGS. HOWEVER CONCERN LIES WITH HOW
HARD TEMPS CRASH HERE IN THE EVENING ESP WITH CLOUD DECK STILL A
WAYS OFF. WINDS WILL BE ON THE LIGHT SIDE AND AIRMASS IS QUITE
DRY. CURRENT FORECAST LOWS ARE ALREADY COLDER THAN MOST GUID SO WE
MAY BE IN GOOD SHAPE. 700 RH DOES INCREASE INTO SW 1/2 OF THE CWA
LATER IN THE NIGHT BUT THE NORTHEAST SHOWS LITTLE MOISTURE. WAA
BAND OF LIGHT SNOWS MAY NUDGE INTO THE FAR SW CWA LATER IN THE
NIGHT. LATEST MODEL TRENDS CONTINUE TO HIGHLIGHT THIS AREA WITH
LIGHT QPF.

SUNDAY...FORECAST CONFIDENCE IS MEDIUM

COMBO OF WAA AND DCVA WITH APPCH SHORTWAVE WILL LEAD TO APPRECIABLE
VERTICAL MOTION TO SUPPORT SNOW DEVELOPMENT FROM SW TO NE ACRS SRN
WI DURG THE MRNG HRS. THERE IS CONSIDERABLE DRY AIR TO OVERCOME
FROM THIS LINGERING ARCTIC AIRMASS SO SOME CONCERN THAT MODEL QPF
VALUES ARE TOO HIGH. THIS HAS BEEN SOMEWHAT BEARED OUT WITH LOWER
SUPERBLEND QPF NUMBERS. SO SNOW AMOUNTS HAVE BEEN TRIMMED A SMIDGE.
STILL THINK AREAS FROM KMSN TO LOCALES WEST AND SOUTH IS WHERE
GREATEST CONFIDENCE IS OF 3 INCH PLUS TOTALS...SO WILL MATCH WITH
ARX/DVN/LOT AND HOIST AN ADVISORY FOR THESE AREAS. TEMPS WILL BE
MILDER WITH THE 925/850 THERMAL ADVECTION PATTERN. CONSENSUS OF
MOS LOOKS PRETTY GOOD.

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

LIGHT SNOW WILL LINGER OVER THE FORECAST AREA SUNDAY NIGHT THROUGH
THE MONDAY MORNING AS A BROAD 500 MB SHORTWAVE TROUGH TRANSLATES
THROUGH THE UPPER MIDWEST. THE GFS MODEL IS SHOWING A POSITIVE
VORTICITY ADVECTION MAXIMA SWEEPING RIGHT ALONG THE WI/IL BORDER.
THE NAM BUFKIT SOUNDINGS ARE SHOWING SATURATION WITHIN THE
DENDRITIC SNOW GROWTH ZONE BETWEEN THE 950-600 MB LAYER BETWEEN
00Z AND 12Z MONDAY. HOWEVER...ISENTROPIC OMEGA PROFILES LOOK
MARGINALLY NEGATIVE...INDICATING LIMITED LIFT WITHIN THE DENDRITIC
GROWTH ZONE.

AFTER 12Z MONDAY...THE MODEL SOUNDINGS INDICATE A WARMING THERMAL
PROFILE COUPLED WITH DRY AIR INTRUSION IN THE MID LEVELS. THIS
SHOULD LEAD TO THE END OF THE SNOWFALL BY THE MONDAY MORNING.
HOWEVER...SOME FLURRIES ARE STILL POSSIBLE DURING THE DAY MONDAY
AS LOW LEVEL LAPSE RATES STEEPEN IN THE AFTERNOON.

MONDAY NIGHT THROUGH TUESDAY NIGHT...FORECAST CONFIDENCE IS LOW

A BRIEF RESPITE FROM PRECIPITATION WILL COME TO S WI MONDAY NIGHT
THROUGH TUESDAY MORNING BEFORE A CLIPPER SYSTEM IS PROGGED TO
TRANSLATE THROUGH CENTRAL IA AND INTO IL. S WI COULD SEE
PRECIPITATION AS EARLY AS MID MORNING TUESDAY. SOME QUESTIONS
EXIST ON HOW FAR SOUTH THE HEAVIEST AXIS OF PRECIPITATION WILL
GO...AS WELL AS HOW QUICKLY THIS SYSTEM MOVES THROUGH. BOTH THE
13.12Z NAM AND GFS ARE SHOWING QPF ENTERING S WI BY 15Z TUE AND
EXITING BY 06Z WED. THE NAM PROGS THE ASSOCIATED SFC LOW MOVING
ABOUT 80 MILES TO THE NORTHWEST OF WHERE THE GFS IS PROGGING THE
SFC LOW AT 18Z TUE. AS A RESULT...THE NAM IS BRINGING MORE QPF TO
S WI THAN THE GFS IS...WITH A DIFFERENCE OF ABOUT 0.15" OF QPF.
DUE TO THIS UNCERTAINTY...WENT WITH THE CONSENSUS MODEL BLENDS TO
HANDLE QPF.

WEDNESDAY THROUGH THURSDAY...FORECAST CONFIDENCE IS HIGH

WED AND THURS ARE LOOKING QUIET AS MID LEVEL RIDGING COUPLED WITH
ASSOCIATED SFC HIGH PRESSURE TAKES CONTROL OF THE REGION. ANOTHER
FAST MOVING CLIPPER SYSTEM IS PROGGED TO DEVELOP...BUT LOOKS TO KEEP
ITS DISTANCE FROM S WI AND MOVE THROUGH CENTRAL IA AND CENTRAL IL.
TEMPERATURES LOOK TO BE MORE SEASONAL...ESPECIALLY FOR THURSDAY AS
LOW LEVEL WARM AIR ADVECTION ENTERS THE SOUTHERN PART OF WISCONSIN
THURSDAY INTO THE DAY FRIDAY. THE FORECAST AREA IS PROGGED TO BE
BETWEEN LOW PRESSURE TO THE NORTHWEST AND HIGH PRESSURE TO THE
EAST...WHICH WILL HELP USHER IN THE WARM AIR FROM THE SOUTH AS
WINDS TURN FROM THE SOUTHEASTERLY DIRECTION. HIGHS WED LOOK TO BE
IN THE MID TO UPPER 20S AND THE LOWER TO MID 30S THURSDAY.

THURSDAY NIGHT THROUGH SATURDAY...FORECAST CONFIDENCE IS LOW

ANOTHER AREA OF LOW PRESSURE LOOKS TO DIVE THROUGH THE UPPER
MIDWEST FRIDAY...WHICH COULD BRING ANOTHER SHOT AT PRECIPITATION.
HOWEVER...MOST PRECIPITATION THAT FALLS SHOULD BE RAIN DUE TO THE
ABOVE FREEZING THERMAL PROFILES. THERE IS A CHANCE OF LIGHT
FREEZING RAIN FOR OUR NORTHERN COUNTIES THURSDAY NIGHT BEFORE A
MORE FAVORABLE THERMAL PROFILE FOR RAIN MOVES IN. THERE IS SOME
UNCERTAINTY AS THE QPF AMOUNTS DIFFER BETWEEN THE GFS AND ECMWF
MODELS. WILL GO WITH THE CONSENSUS MODEL BLENDS FOR NOW. HIGHS
FRIDAY LOOK TO BE ON COURSE FOR THE LOWER TO MID 40S ACROSS S WI.

SATURDAY LOOKS QUIET AS THE LOW PRESSURE DEPARTS SATURDAY MORNING.
TEMPERATURES SHOULD COOL BACK DOWN AS THE LOW DEPARTS AND A
NORTHWESTERLY WIND REGIME BRINGS IN COOLER AIR.

AVIATION/00Z TAFS/...VFR SKC CONTINUES WITH HIGH PRESSURE
DOMINATING WELL INTO THE EVENING HOURS. 700 MILLIBAR RH ON THE
INCREASE BUT NOT UNTIL AFTER 06Z. IN FACT...MODELS KEEP MUCH OF NE
CWA LARGELY CLOUD FREE FOR MUCH OF THE NIGHT. SFC RIDGE AXIS
POSITIONED ACROSS FAR ERN WI AT 06Z AND THEN INTO THE OH VLY LATER
IN THE NIGHT. LATEST MODELS CONTINUE TO SHOW SNOW SPREADING ACROSS
SRN WI SUNDAY MORNING IN RESPONSE TO INCREASING LLVL WAA AND APPCHNG
SHORTWAVE. CONSIDERABLE LOW AND MID LEVEL DRY AIR PER BUFKIT IS
PROGGD TO SATURATE RAPIDLY IN A TOP/DOWN FASHION DURING THE MORNING
AS VERTICAL MOTION FIELD RAMPS UP WITHIN A DEEP DENDRITIC GROWTH
ZONE. HARD TO ARGUE WITH THE TRENDS IN MOS WITH CIGS/VSBYS SHOWING A
LOWERING TREND TO IFR LEVELS. HAVE TRIMMED SNOW AMOUNTS DOWN
SLIGHTLY.

MARINE...SOUTHEAST WINDS EXPECTED TO INCREASE TO SMALL CRAFT
ADVISORY LEVELS ON SUNDAY AHEAD OF A LOW PRESSURE TROUGH. VSBL
IMAGERY DOES SHOW SOME ICE COVERAGE...ESP ACROSS THE SRN TWO ZONES.
WOULD STILL EXPECT THE ONSHORE FLOW TO LEAD TO SOME HIGHER WAVES IN
ICE FREE AREAS. WINDS ARE EXPECTED TO SHIFT SOUTHWEST SUNDAY NIGHT
AND DEPENDING ON THE MODEL COULD REMAIN GUSTY. SOME POTENTIAL FOR A
SLACKENING GRADIENT WITHIN THE TROUGH AXIS SO ADVISORY MAY BE ABLE
TO END SOONER DEPENDING ON LINGERING WAVE ACTION.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...WINTER WEATHER ADVISORY FROM 6 AM TO 9 PM CST SUNDAY FOR WIZ062-
     063-067>069.

LM...SMALL CRAFT ADVISORY FROM NOON SUNDAY TO 6 AM CST MONDAY FOR
     LMZ643>646.

&&

$$

UPDATE...HENTZ
TONIGHT/SUNDAY AND AVIATION/MARINE...COLLAR
SUNDAY NIGHT THROUGH SATURDAY...JTS



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