Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 281822 AAA
AFDMKX

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI
1222 PM CST FRI NOV 28 2014

.UPDATE...

THE MORNING SNOW MOVED OUT OF SOUTHERN WI AND THERE IS SUNSHINE WEST
OF MADISON. THERE IS A LOT OF UNCERTAINTY ABOUT WHAT IS GOING TO
HAPPEN WITH THE CLOUDS AND PRECIP CHANCES FOR THE LATE
AFTERNOON/EARLY EVENING TIME PERIOD. THE 12Z MODELS ARE STILL
SHOWING LIGHT QPF OVER ALMOST ALL OF SOUTHERN WI. THIS IS DUE TO 850-
700MB FRONTOGENESIS MOVING THROUGH. THE UNCERTAINTY IS HOW MUCH DRY
AIR WILL HINDER PRECIP DEVELOPMENT AND ALSO WHAT TYPE OF PRECIP
WOULD HIT THE GROUND.

TEMPERATURES WILL BE WARMING ALOFT THROUGH THE AFTERNOON WITH MAX
TEMP AROUND 800-850MB OF +4C AT MSN. THIS IS ALSO A DRY LAYER WITH
THE WAA ADVECTING DRIER AIR IN FROM THE PLAINS. 500MB SHORTWAVE
ENERGY AND UPPER DIVERGENCE IN THE ENTRANCE REGION OF A JET STREAK
WILL LEAD TO ENHANCED UPWARD MOTION WITHIN THE DENDRITIC GROWTH
ZONE... LOCATED AT 500-600MB LEVEL. THIS LAYER WILL ALSO BE
SATURATED. IT IS HARD TO IGNORE THIS SIGNAL EVEN THOUGH THERE MAY
BE A DRY LAYER IN THE LOWER LEVELS. IF THERE IS ENOUGH FORCING
ALOFT... THEN THERE IS A GOOD CHANCE IT WILL BE ABLE TO SATURATE
FROM THE TOP DOWN AND PRODUCE LIGHT PRECIP AT THE GROUND... GIVEN
ENOUGH TIME. THE ONLY THING IS THAT IT WILL BE A SHORT-LIVED EVENT
OVER SOUTHERN WI. THE TEMPERATURE PROFILE WILL DETERMINE WHAT
PRECIP TYPE IT WILL BE... BUT LIKELY A MIX OF SLEET AND FREEZING
RAIN THAT CHANGES TO SNOW BEFORE ENDING... ALL WITHIN A 2 TO 3
HOUR PERIOD.

THE GFS BRINGS IT FURTHER SOUTH ACROSS SOUTHERN WI THAN THE NAM...
AND ALSO A LITTLE EARLIER THAN THE NAM. WE WILL BE WATCHING TRENDS
UPSTREAM OVER SOUTHERN MN AND NORTHERN IOWA EARLY THIS AFTERNOON.

&&

.AVIATION/18Z TAFS/...

THERMAL PROFILES SUGGEST THAT ANY PRECIPITATION DURING THE LATE
AFTERNOON AND EVENING WOULD BE FREEZING RAIN OR SLEET.  THERE IS
STILL A LOT OF UNCERTAINTY ABOUT WHETHER OR NOT IT WILL DEVELOP. IF
IT DOES... EXPECT ONLY LIGHT AMOUNTS WITH SLEET OR FREEZING RAIN
POSSIBLY CHANGING OVER TO SNOW BEFORE ENDING... ALL WITHIN A 2-3
HOUR PERIOD.

RIGHT AHEAD OF A COLD FRONT OVERNIGHT...SOUTH WINDS PULL IN WARMER
AND SOMEWHAT MORE MOIST AIR OVER SNOWPACK AND PROBABILITIES OF IFR
CEILINGS INCREASE...ESPECIALLY INTO MSN. NOT CONFIDENT THAT THE
REALLY LOW IFR CIGS THAT THE NAM AND HRRR SUGGEST WILL PAN OUT.

&&

.PREV DISCUSSION... /ISSUED 548 AM CST FRI NOV 28 2014/

UPDATE...

BASED ON RADAR TRENDS OVER THE DAKOTAS...00Z ECMWF...06Z
GFS/NAM...AND LATEST HRRR/RAP...HAVE DECIDED TO BOOST AFTERNOON
POPS WITH SECOND WAVE OF PRECIPITATION WHICH WILL BE FREEZING RAIN
AND SLEET AS WARM LAYER MOVES IN. FAR NORTHEAST MAY HOLD ONTO ALL
SNOW SO THAT 1-2 INCH AMOUNTS HOLD TRUE.

PREV DISCUSSION... /ISSUED 340 AM CST FRI NOV 28 2014/

TODAY...FORECAST CONFIDENCE IS MEDIUM.

WESTERLY FLOW HAS ALLOWED MILD PACIFIC AIR TO SPREAD ACROSS
NORTHERN ROCKIES INTO CENTRAL PLAINS. STRONG WARM ADVECTION
PUSHING ACROSS WISCONSIN THIS MORNING WITH A FEW HOURS OF SNOW.
NOT MUCH ALONG THE IL BORDER...BUT 1-2" OF SNOW IN THE SHEBOYGAN
AREA. MOST AREAS JUST RECEIVE A DUSTING.

SOME OF THE MODELS HAVE A SECOND BATCH OF PRECIPITATION THIS
AFTERNOON. THIS IS DURING A PERIOD WHERE A WARM LAYER DEVELOPS AND
WOULD SUGGESTION FREEZING RAIN POTENTIAL...ESPECIALLY IN THE
SOUTHWEST. MOST OF THE LIFT AND MOISTURE BY THIS TIME IS PRETTY
HIGH UP...WITH RATHER DRY AIR IN LOW LEVELS NEAR THE WARM NOSE.
WILL LEAN ON THE DRIER SIDE BUT CERTAINLY WILL NEED TO BE WATCHED.

TONIGHT...FORECAST CONFIDENCE IS MEDIUM.

THINGS DRY OUT ALOFT BUT GUIDANCE SHOWS INCREASING MOISTURE IN
THE BOUNDARY LAYER WITH SOUTHERLY WINDS AHEAD OF FRONT. LOOKS LIKE
A STRATUS DECK WILL FORM BUT MOST OF THE UNCERTAINTY IS IN WHETHER
IT WILL BECOME AN ADVECTION SNOW EVENT OVER THE SNOWPACK. HIGH
CONFIDENCE IN VERY LOW CLOUDS BUT LOW CONFIDENCE IN DENSE FOG.
TEMPERATURES LIKELY TO RISE DURING THE NIGHT.

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

SYNOPTIC MODELS IN GOOD AGREEMENT WITH WARM AIR ADVECTION
CONTINUING ACROSS THE AREA SATURDAY AND SATURDAY NIGHT...WITH
GENERALLY ZONAL 500 MB FLOW. THERE ARE SIGNIFICANT DIFFERENCES
WITH LOW LEVEL MOISTURE PROFILES BETWEEN THE NAM/GFS AND
ECMWF/CANADIAN MODELS. THE NAM/GFS HOLD ONTO SATURATED BOUNDARY
LAYER BELOW INVERSION DURING THIS TIME...WHILE THE ECMWF/CANADIAN
MODELS ARE DRIER.

THIS RESULTS IN THE NAM/GFS SHOWING BLOTCHY QPF ACROSS THE AREA
SATURDAY INTO SATURDAY NIGHT...INDICATIVE OF DRIZZLE/VERY LIGHT
RAIN. MOS GUIDANCE ALSO SHOWING SOME FOG DEVELOPMENT IN THE AREA
AS WELL SATURDAY MORNING. THE ECMWF/CANADIAN MODELS ARE DRY
DURING THIS TIME.

NAM/GFS HAVE BEEN OVERDONE WITH BOUNDARY LAYER MOISTURE IN THE
RECENT AND DISTANT PAST...ESPECIALLY THE NAM...SO AM SKEPTICAL ON
THE DRIZZLE/VERY LIGHT RAIN AND FOG. FOR NOW...CONTINUED TO KEEP
SATURDAY AND SATURDAY NIGHT DRY...WITH SKIES BECOMING PARTLY
CLOUDY SATURDAY NIGHT. MILD TEMPERATURES IN THE LOWER TO MID 40S
ARE EXPECTED SATURDAY...HOLDING IN THE 30S SATURDAY NIGHT.

MODELS BRING SURFACE COLD FRONT SOUTHEAST INTO THE AREA LATER
SATURDAY NIGHT AND THROUGH THE AREA BY MIDDAY SUNDAY. KEPT
FORECAST DRY FOR NOW WITH LACK OF DEEP MOISTURE AVAILABLE. STRONG
COLD AIR ADVECTION THEN TAKES OVER FOR LATER SUNDAY INTO SUNDAY
NIGHT...AS STRONG HIGH PRESSURE MOVES INTO THE NORTHERN PLAINS.
THIS WILL BRING COLD TEMPERATURES BACK INTO THE AREA. TEMPERATURES
SHOULD FALL THROUGH THE 30S ON SUNDAY...AND INTO THE TEENS SUNDAY
NIGHT.

LONG TERM...MONDAY THROUGH THURSDAY...FORECAST CONFIDENCE IS
MEDIUM.

GFS/ECMWF IN FAIR AGREEMENT WITH STRONG HIGH PRESSURE MOVING
SOUTHEAST INTO THE AREA MONDAY...MAINTAINING THE COLD TEMPERATURES
OVER THE AREA. 500 MB FLOW REMAINS FAIRLY ZONAL OVER THE REGION. THE
HIGH WILL SHIFT EAST OF THE REGION MONDAY NIGHT...ALLOWING FOR
WARM AIR ADVECTION TO KICK IN AND REMAIN INTO TUESDAY. THIS SHOULD
BRING A BRIEF REBOUND IN TEMPERATURES.

A COLD FRONT THEN SLIDES SOUTHEAST THROUGH THE AREA TUESDAY
NIGHT...WITH LOW POPS REMAINING IN THE FAR EAST. MAY BE ABLE TO
REMOVE THESE LOW POPS IN LATER FORECASTS IF MODELS CONTINUE THE
DRY TREND TUESDAY NIGHT. ANOTHER HIGH PASSING SOUTHEAST THROUGH
THE REGION WEDNESDAY INTO WEDNESDAY NIGHT SHOULD BRING ANOTHER
BRIEF SHOT OF COLD AIR.

GFS THEN BRINGS A BROAD AREA OF QPF WITHIN A WARM AIR ADVECTION
REGIME INTO THE REGION THURSDAY...WITH THE ECMWF KEEPING ANY QPF
WELL SOUTHWEST OF THE AREA. FOR NOW...WILL USE CONSENSUS POPS AND
TEMPERATURES THIS FAR OUT.

AVIATION/12Z TAFS/...

BATCH OF SNOW THIS MORNING WILL MAINLY IMPACT AREAS NORTH OF THE
TAF SITES. HOWEVER...BRIEF MVFR CONDITIONS AND A DUSTING OF SNOW
EXPECTED.

THERMAL PROFILES SUGGEST THAT ANY PRECIPITATION DURING THE LATE
AFTERNOON AND EVENING WOULD BE FREEZING RAIN OR SLEET.
HOWEVER...DO NOT EXPECT MUCH PRECIPITATION SO THIS SHOULD NOT BE
AN IMPACT.

RIGHT AHEAD OF COLD FRONT OVERNIGHT...SOUTH WINDS PULL IN WARMER
AND SOMEWHAT MORE MOIST AIR OVER SNOWPACK AND PROBABILITIES OF IFR
CEILINGS INCREASE...ESPECIALLY INTO MSN.

MARINE...

SOUTHERLY WINDS AND WAVES WILL APPROACH SMALL CRAFT ADVISORY THIS
AFTERNOON AND EVENING BUT MARGINAL NATURE OF EVENT DOES NOT APPEAR
TO WARRANT A SMALL CRAFT ADVISORY.

BRISK NORTHWEST WINDS SUNDAY EVENING AND MONDAY WILL ALSO
APPROACH SMALL CRAFT ADVISORY LEVELS IN THE WAKE OF A COLD FRONT.

BRISK SOUTH WINDS ON TUESDAY AND TUESDAY NIGHT WILL ALSO GENERATE
RATHER HIGH WAVES.

&&

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

$$

UPDATE...MRC
TODAY/TONIGHT AND AVIATION/MARINE...CRAVEN
SATURDAY THROUGH THURSDAY...WOOD


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