Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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000
FXUS63 KMKX 212134 AAA
AFDMKX

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI
334 PM CST SAT FEB 21 2015

UPDATED TO ADD MARINE SECTION

.SHORT TERM...

.TONIGHT AND SUNDAY... FORECAST CONFIDENCE HIGH.

THE SURFACE TROUGH AND ASSOCIATED COLD FRONT ARRIVED IN SOUTHEAST
WISCONSIN THIS MORNING ON LIGHT NORTHWEST TO NORTH WINDS. THE 925MB
COLD FRONT LAGS BEHIND IN CENTRAL WI AS OF 3 PM. THE 925MB FRONT AND
STRONGER COLD AIR ADVECTION WILL CAUSE STEEP LOW LEVEL LAPSE RATES
WITHIN THE DENDRITE GROWTH ZONE /DGZ/ WITH JUST ENOUGH OMEGA/UPWARD
MOTION TO PRODUCE SCATTERED LIGHT SNOW SHOWERS ACROSS SOUTHERN AND
CENTRAL WI FROM LATE AFTERNOON THROUGH THE MID EVENING HOURS. ONLY A
DUSTING OF SNOW IS EXPECTED.

CLOUDS WILL GRADUALLY CLEAR FROM NORTHWEST TO SOUTHEAST AFTER
MIDNIGHT. THE NAM KEEPS LOW LEVEL MOISTURE AND THUS CLOUDS IN PLACE
OVER SOUTHERN WI THROUGH SUNDAY AFTERNOON. BASED ON UPSTREAM
SATELLITE IMAGERY AND OBSERVATIONS... THAT APPEARS OVERDONE AND I
LEANED TOWARD THE DRIER GFS AND OTHER MODEL SOLUTIONS.

TEMPS ARE EXPECTED TO FALL TO AROUND ZERO NEAR THE DELLS AND 10
ABOVE NEAR KENOSHA BY 12Z SUNDAY. MODELS ARE SHOWING SLIGHTLY WARMER
TEMPS THAN THE PREVIOUS FORECAST. THE TEMPS WILL STEADY OUT IN THE
MORNING AND RISE VERY LITTLE THROUGH THE DAY... WITH HIGHS SUNDAY
MAINLY IN THE SINGLE DIGITS ABOVE ZERO. DESPITE STEADY NORTHWEST
WINDS... WIND CHILL TEMPS BOTTOM OUT IN THE TEENS BELOW ZERO TOWARD
THE DELLS. NO WIND CHILL ADVISORY PLANNED FOR THE MKX FORECAST AREA
TONIGHT.

SCATTERED LOW CLOUDS WILL BE POSSIBLE THROUGH THE DAY SUNDAY DUE TO
STEEP LOW LEVEL LAPSE RATES AND CONTINUED COLD AIR ADVECTION. CANNOT
RULE OUT A FEW FLURRIES.

.SUNDAY NIGHT AND MONDAY...FORECAST CONFIDENCE HIGH.

THE BASE OF THE UPPER TROUGH WILL MOVE THROUGH AND NORTHWEST FLOW
WILL RETURN BY MONDAY. VERY WEAK UPPER CONVERGENCE SUNDAY NIGHT
WITH VERY WEAK UPPER DIVERGENCE LATER MONDAY. WEAK 700 MB DOWNWARD
MOTION THROUGH MONDAY MORNING WITH VERY WEAK UPWARD MOTION MONDAY
AFTERNOON. 700 MB RH REMAINS DRY WITH SOME MOISTENING NORTH AREAS
MONDAY. LOW LEVELS ARE QUITE DRY.

850/700 MB WARM AIR ADVECTION BEGINS TOWARDS MONDAY MORNING...BUT
VERY COLD SURFACE TEMPERATURES ARE EXPECTED SUNDAY NIGHT AS THE
SURFACE HIGH BUILDS TOWARDS IOWA BUT THEN DROPS SOUTH. AS A RESULT
THE WINDS MAY NOT DECOUPLE COMPLETELY SO WIND CHILLS WILL REMAIN
AT PLAY IN THE ADVISORY CRITERIA.

THE HIGH DROPS SOUTH MONDAY WITH A SOUTHWEST LOW LEVEL FLOW AND
WARM AIR ADVECTION MONDAY. MUCH OF THE WARMING IS ALOFT WITH A LOW
LEVEL INVERSION AROUND 1 THSD FT EVEN DURING THE AFTERNOON. THE
MOIST LAYER BELOW THE INVERSION IS VERY SHALLOW...SO STRATUS NOT
EXPECTED...JUST INCREASING MID/HIGH LEVEL CLOUDS LATER MONDAY.

.MONDAY NIGHT AND TUESDAY...FORECAST CONFIDENCE HIGH.

A SPLIT FLOW DEVELOPS IN THE UPPER LEVELS WITH A NORTHERN TROUGH
PUSHING INTO WISCONSIN TUESDAY. THE ECMWF HAS COME MORE IN LINE
WITH THE GFS WITH THE STRONGER MID LEVEL TROUGH BRUSHING THE
NORTHERN GREAT LAKES WITHOUT THE PRIOR LEAD CYCLONIC VORTICITY
MAXIMUM ACROSS SOUTHERN WISCONSIN.

A BAND OF HIGH RELATIVE HUMIDITY AT 925/850/700 MB SWINGS DOWN
ACROSS SOUTHERN WISCONSIN TUESDAY. THE SURFACE LOW IS NORTH OF
THE GREAT LAKES WITH A TRAILING COLD FRONT REACHING THE AREA
TUESDAY AFTERNOON.

THE NAM BRINGS A BAND OF LIGHT SNOW WITH THE FRONT...BUT THE GFS
AND ECMWF ARE BOTH DRIER...WITH THE 00Z ECMWF HAVING NO MEASURABLE
PRECIPITATION. WILL CONTINUE THE LOW MENTION OF LIGHT SNOW.

.LONG TERM...

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

THE BASE OF THE NORTHERN STREAM TROUGH EXTENDS ACROSS THE GREAT
LAKES TO THE NORTHEAST U.S. WEDNESDAY.

ANOTHER SURFACE COLD HIGH NORTH OF MONTANA AND THE DAKOTA...
BUILDS INTO THE UPPER MISSISSIPPI VALLEY WITH NORTH LOW LEVEL
WINDS AND COLD AIR ADVECTION.

.THURSDAY AND FRIDAY...FORECAST CONFIDENCE HIGH.

THE NORTHERN STREAM BECOMES A BIT MORE ZONAL AS IT WEAKENS AND A
SOUTHWEST U.S. TROUGH BEGINS TO DEVELOP.

THE SURFACE COLD HIGH SAGS INTO THE UPPER MISSISSIPPI VALLEY AND
WESTERN GREAT LAKES REGION. AS THE HIGH MOVES ACROSS...WELL BELOW
NORMAL TEMPERATURES WILL HAVE A FIRM GRIP ON THE REGION. WITH
LIGHT WINDS. LOW TEMPERATURES WILL BE VERY COLD.

.SATURDAY...FORECAST CONFIDENCE MEDIUM.

THE GFS LIFTS AN INITIAL SHORTWAVE INTO THE PLAINS AND MISSISSIPPI
VALLEY REGION ON SATURDAY WHILE THE 00Z ECMWF WAS SLOWER...BUT THE
12Z ECMWF IS NOW QUICKER THAN THE GFS.

AS A RESULT THE GFS BRINGS SOME LIGHT SNOW CLOSE TO SOUTHERN
WISCONSIN BUT THE MAJOR DIFFERENCES OCCUR TO OUR SOUTH AND ALSO
LATER SUNDAY AND MONDAY.

&&

.AVIATION/00Z TAFS/...

MVFR CIGS ARE EXPECTED OVER MOST OF SOUTHERN WI THROUGH THIS
EVENING...WITH CONDITIONS LIFTING TO VFR TOWARD MIDNIGHT AND
THEREAFTER AS SKIES GRADUALLY CLEAR FROM NORTHWEST TO SOUTHEAST.
STEEP LAPSE RATES IN THE COLD AIR ADVECTION SHOULD PRODUCE AN AREA
OF SCATTERED LIGHT SNOW SHOWERS OR FLURRIES LATE THIS AFTERNOON AND
EVENING. ONLY TRACE/DUSTING ACCUMULATIONS ARE EXPECTED.

WINDS WILL INCREASE THROUGH THE NIGHT AND REMAIN ELEVATED THROUGH
SUNDAY EVENING. GUSTS TO AROUND 23 KNOTS ARE POSSIBLE SUNDAY
AFTERNOON.

&&

.MARINE...

BRISK NORTHWEST WINDS ARE EXPECTED SUNDAY AS ARCTIC HIGH PRESSURE
SETTLES INTO THE UPPER MIDWEST. WIND GUSTS OF 20 TO 25 KNOTS ARE
POSSIBLE OVER THE NEARSHORE WATERS OF SOUTHEAST WISCONSIN SUNDAY
AFTERNOON.

WINDS WILL SHIFT TO THE SOUTHWEST MONDAY AFTERNOON AS THE HIGH
SLIDES INTO THE CENTRAL U.S. AND LOW PRESSURE DROPS OUT OF CENTRAL
CANADA. HIGH-END SMALL CRAFT ADVISORY WINDS AND GUSTS ARE EXPECTED
MONDAY NIGHT.

&&

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

$$

TONIGHT/SUNDAY AND AVIATION/MARINE...MRC
SUNDAY NIGHT THROUGH SATURDAY...HENTZ



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