Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 192015
AFDMKX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI
215 PM CST MON JAN 19 2015

.SHORT TERM...

.TONIGHT AND TUESDAY...FORECAST CONFIDENCE IS MEDIUM.

A SERIES OF LOW AMPLITUDE DISTURBANCES RIDING NORTHWEST FLOW ALOFT
WILL IMPACT SOUTHERN WISCONSIN THROUGH THE PERIOD. SURFACE FRONTAL
ZONE MEANDERS ALONG THE ILLINOIS/WISCONSIN BORDER AS A SURFACE WAVE
TRAVELS SOUTHEASTWARD ACROSS THE SOUTHERN CWA ON TUESDAY. LIGHT
ACCUMULATING SNOWFALL IS EXPECTED.

WEAK HEIGHT FALLS ASSOCAITED WITH UPSTREAM PV ANOMALY/SHORTWAVE ARE
NOTED ACROSS THE DAKOTAS TODAY. THIS PIECE OF ENERGY WILL SLIDE
SOUTHEASTWARD INTO IOWA OVERNIGHT...WITH ACCOMPANYING SURFACE LOW
CROSSING SOUTHERN WISCONSIN. LOW-LEVEL FRONTOGENETIC FORCING AND
WARM ADVECTION ARE MAXIMIZED ACROSS THE NE CWA OVERNIGHT...WITH
ATMOSPHERIC PROFILES SATURATING THROUGH 750 MB AT SBM BY 0Z.
TIMING DIFFERENCES AMONG THE DETERMINISTIC MODELS INTRODUCE
UNCERTAINTY IN ONSET TIMING...WITH THE GFS BRINGING PRECIP INTO THE
NORTHERN CWA BEFORE 0Z WHILE THE EURO KEEPS IT DRY UNTIL AROUND 6Z.
NAM SEEMS LIKE A GOOD COMPROMISE SOLUTION...SO BROUGHT CHANCE POPS
INTO THE NE CWA AT 0Z. LIGHT SNOW WILL START IN THE NE CWA
BEFORE SPREADING SOUTHWEST OVERNIGHT. ACCUMULATIONS WILL BE
LIGHT...WITH UP TO ONE HALF TO ONE INCH POSSIBLE IN THE NE
CWA. LATEST RAP SOUNDINGS SUGGEST SOME FREEZING DRIZZLE POTENTIAL
OVERNIGHT...BUT CONFIDENCE IN OCCURANCE IS LOW. WILL CONTINUE
MONITORING TRENDS.

LIGHT SNOW OR FLURRIES MAY LINGER INTO TUESDAY AFTERNOON AS ANOTHER
WEAK PIECE OF ENERGY DROPS SOUTHEASTWARD FROM CENTRAL WISCONSIN
TOWARDS LAKE MICHIGAN. A MORE SIGNIFICANT SHORTWAVE WILL SLIDE
SOUTHEAST OF THE CWA TUESDAY EVENING...WITH LOW TO MID-LEVEL
FRONTOGENESIS MAXIMIZED OVER THE SOUTHERN CWA. ACCOMPANYING SURFACE
LOW WILL TRACK FROM SOUTHWESTERN WISCONSIN INTO NORTHERN ILLINOIS
DURING THIS TIME...WITH LIGHT SNOW EXPECTED DURING THE EVENING.

CONSENSUS MODEL BLENDED TEMPERATURES APPEAR LARGELY ON TRACK SO WILL
NOT DEVIATE. LOWS IN THE 20S TONIGHT WITH HIGHS IN THE LOWER TO MID
30S ON MONDAY SEEM REASONABLE.

.TUESDAY NIGHT AND WEDNESDAY... FORECAST CONFIDENCE HIGH.

THE UPPER FLOW BECOMES ZONAL WITH A WEAK BROAD TROUGH ACROSS THE
GREAT LAKES...AS A WEAK SHORTWAVE MOVES ACROSS WISCONSIN. A
LAGGING MID LEVEL TROUGH PERSISTS THROUGH WEDNESDAY. THE NAM
LINGERS THE LIGHT PRECIPITATION THROUGH WEDNESDAY WHILE THE GFS
AND ECMWF HAVE HALF OR LESS OF THE PRECIPITATION THAT THE NAM IS
PRODUCING. PREFER THE GFS/ECMWF DUE TO THE WEAK UPWARD MOTION EVEN
ON THE NAM. TEMPERATURES ARE IN THE FAVORABLE SNOW GROWTH ZONE
FROM 9 TO 11 THSD FT DURING THE LIFT...BUT AS COLD AIR ADVECTION
OCCURS THAT EXPANDS THE SNOW GROWTH ZONE TO 6 TO 11 THSD FT...THE
LIFT WEAKENS. EVEN IF THE NAM VERIFIES...SNOW AMOUNTS WOULD NOT
REACH ADVISORY CRITERIA.

.WEDNESDAY NIGHT AND THURSDAY...FORECAST CONFIDENCE HIGH.

THE NAM/GFS AND ECMWF BRINGS A 500 MB LEVEL TROUGH AXIS ACROSS
SOUTHERN WISCONSIN WEDNESDAY NIGHT. THEN SOUTHERN WISCONSIN WILL
BE IN A NORTHWEST MID LEVEL FLOW. THE 250 MB TROUGH AXIS IS SLOWER
TO CROSS SOUTHERN WISCONSIN. THE HIGHER 700 MB RH DRIES DURING
WEDNESDAY NIGHT AND IS VERY DRY. THE 925/850 MB LAYER REMAINS
HIGH.

AT THE SURFACE A SOUTHWEST FLOW BEGINS WITH WARM AIR ADVECTION
OCCURRING LATER THURSDAY.

.LONG TERM...

.THURSDAY NIGHT AND FRIDAY...FORECAST CONFIDENCE HIGH.

THE MID AND UPPER LEVEL FLOW IS OUT OF THE NORTHWEST AS A WEAK
SHORTWAVE MOVES ACROSS THE NORTHERN PLAINS TOWARDS WISCONSIN LATER
FRIDAY.

WARM AIR ADVECTION IS OCCURRING AHEAD OF AN APPROACHING
SURFACE TROUGH...WITH LITTLE IF ANY PRECIPITATION ACROSS THE
SOUTH...ALTHOUGH SOME PRECIPITATION OCCURS MAINLY ON THE GFS
TOWARD CENTRAL WISCONSIN FRIDAY. PREFER THE DRIER ECMWF.

.FRIDAY NIGHT AND SATURDAY...FORECAST CONFIDENCE MEDIUM.

THE GFS AND 00Z ECMWF ARE IN BETTER AGREEMENT IN EXITING THE
NORTHERN STREAM SHORTWAVE SATURDAY.

THE SURFACE TROUGH MOVES ACROSS THE AREA FRIDAY NIGHT WITH WEAK
COLD AIR ADVECTION.  THE 00Z ECMWF IS A LITTLE SLOWER.

.SUNDAY AND MONDAY...FORECAST CONFIDENCE MEDIUM.

YET ANOTHER SHORTWAVE DROPS IN FROM THE NORTHWEST ON SUNDAY. THE
12Z GFS IS A LITTLE STRONGER AND MORE SOUTH. BY MONDAY THE TROUGH
SHIFTS EAST WITH A NORTHWEST FLOW ACROSS THE UPPER MISSISSIPPI
VALLEY. BOTH THE 12Z GFS AND 00Z ECMWF HAVE AN APPROACHING WEAK
SHORTWAVE LATE SUNDAY.

THE GFS BRUSHES SOUTHWEST AREAS OF THE FORECAST AREA WITH SOME
LIGHT SNOW...WHILE THE 00Z ECMWF IS WELL SOUTH. HIGH PRESSURE
THEN BUILDS ACROSS THE GREAT LAKES WITH THE GFS PUSHING IN A WEAK
CLIPPER FOR LATE MONDAY. THE 00Z ECMWF IS SLOWER AND
WEAKER...KEEPING THE HIGH ACROSS THE GREAT LAKES.

&&

.AVIATION/00Z TAFS/...

A WEAK COLD FRONT PUSHING DOWN LAKE MICHIGAN
AND SOUTHEAST LAND AREAS SHOULD BRING SOME MVFR CONDITIONS FOR A
TIME THIS MORNING AT KMKE/KUES/KENW. BUT...EXPECT IT TO LIFT BACK TO
VFR LEVELS BY MID MORNING AS DRIER AIR WORKS IN WITH WEAK HIGH
PRESSURE SETTLING IN. A FAST MOVING WEAK LOW PRESSURE SYSTEM PUSHES
IN FROM THE NORTHWEST TONIGHT. THIS SHOULD BRING A CHANCE OF LIGHT
SNOW TO AREAS MAINLY NORTH OF MADISON AND MILWAUKEE. BUT...THE TAF
SITES COULD SEE A PERIOD OF LIGHT SNOW WITH AMOUNTS ONLY EXPECTED TO
BE AROUND 1/10 OF AN INCH...OR A DUSTING.  ALONG WITH THE
SNOW...CIGS SHOULD LOWER TO MVFR THIS EVENING.

&&

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

$$

TONIGHT/TUESDAY AND AVIATION/MARINE...COLLAR/SPM
TUESDAY NIGHT THROUGH MONDAY...HENTZ


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