Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 231737
AFDMKX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI
1137 AM CST TUE DEC 23 2014

.UPDATE...
IN THE VERY SHORT TERM...DRIER AIR IS WORKING INTO SOUTHERN
WISCONSIN ON SOUTHWEST WINDS AHEAD OF LOW PRESSURE LOCATED NEAR
THE DELLS LATE THIS MORNING. THAT LOW CONTINUES TO MOVE NORTHEAST.
TEMPS ARE ON THEIR WAY TO THE MID 40S THIS AFTERNOON. SO JUST
SOME SPRINKLES OUT THERE TODAY WITH NO TRAVEL ISSUES DUE TO
FREEZING TEMPS. GENERALLY QUIET WEATHER CONTINUES TONIGHT WHILE WE
WAIT FOR THE SECOND LOW TO MOVE OUT OF THE SOUTHERN MISSISSIPPI
VALLEY. TEMPS SHOULD REMAIN JUST ABOVE FREEZING.

THIS SECOND LOW IS COMING INTO SHARPER FOCUS FOR OUR AREA...AS
WELL AS ITS POTENTIAL IMPACT ON THE SOUTHEAST.

WE WILL BE RAISING SNOW AMOUNTS A FEW INCHES AND ARE COLLABORATING
WITH NEIGHBORING OFFICES AND THE WEATHER PREDICTION CENTER ON A
POSSIBLE WINTER WEATHER ADVISORY FOR THE FAR SOUTHEAST. DETAILS
WILL COME OUT WITH THE STANDARD FORECAST PACKAGE BY 3-4 PM THIS
AFTERNOON. THE NAM IS HITTING US THE HARDEST BUT IT LOOKS LIKE
ITS QPF FIELD IS SUFFERING SOME USUAL AGGRESSIVENESS. THE
GFS/GEMS AND OLD EC WOULD CLIP OUR SE...MAINLY
MILWAUKEE/RACINE/KENOSHA COUNTIES WITH 2-4 INCHES OF WET
SNOW...LOCAL AREAS MAY GET MORE. WE STILL NEED TO DIGEST MUCH MORE
DATA...SO THOSE NUMBERS MAY CHANGE.

THE GUIDANCE IS SHOWING A PERIOD DURING THE AFTERNOON WHERE WE GET
VERY STRONG OMEGA RIGHT IN THE MIDDLE OF THE DENDRITE
ZONE...SUGGESTING A POTENTIAL BURST OF HEAVY SNOW. SURFACE TEMPS
WILL BE IN THE MID TO UPPER 30S BEFORE THE SNOW...LIKELY COOLING
TO NEAR FREEZING AS THE BURST OCCURS. THIS PRESENTS A CHALLENGE
WITH SNOWFALL AND MELTING. WE BELIEVE THE SNOWFALL WILL EASILY
EXCEED MELTING POTENTIAL FOR A TIME. THE SNOW SHOULD CONTINUE INTO
THE EARLY EVENING...THEN DIMINISH QUICKLY.

CHRISTMAS IS STILL LOOKING DRY UNDER HIGH PRESSURE.

&&

.AVIATION/18Z TAFS/...
LOOK FOR PERSISTENT MVFR TO IFR CONDITIONS THROUGH TONIGHT. A COLD
FRONT WILL SWEEP ACROSS THE AREA OVERNIGHT. MVFR CONDITIONS WILL
BE FOUND AHEAD OF THE FRONT WITH IFR CIGS/VSBYS BEHIND IT.

WE ARE CONCERNED ABOUT THE POTENTIAL FOR A HEAVY WET SNOW
ACCUMULATION AT THE MILWAUKEE/WAUKESHA/KENOSHA TAF SITES FROM
ABOUT EARLY AFTERNOON THROUGH ABOUT 6 PM WEDNESDAY AS LOW PRESSURE
TRACKS JUST TO OUR EAST. THIS WILL LIKELY HAVE AN IMPACT ON
AIRPORT OPERATIONS FOR A TIME. CONDITIONS WILL BE IFR ACROSS THE
ENTIRE AREA FROM MID MORNING WEDNESDAY THROUGH WEDNESDAY EVENING.

&&

.MARINE...

PERSISTENT WINDS AND HIGH WAVES HAVE RESULTED IN AN EXTENSION OF
THE SMALL CRAFT ADVISORY THROUGH THE AFTERNOON NORTH OF MILWAUKEE.

&&

.PREV DISCUSSION... /ISSUED 330 AM CST TUE DEC 23 2014/

SHORT TERM...

TODAY AND TONIGHT...FORECAST CONFIDENCE...HIGH

THE 250 MB UPPER LEVEL TROUGH AXIS FROM OKLAHOMA TO MINNESOTA
SHARPENS AND  REMAINS JUST WEST OF THE MISSISSIPPI VALLEY. ONE JET
MAX ON THE EAST SIDE LIFTS FROM THE OHIO VALLEY AND EASTERN GREAT
LAKES AREA INTO SOUTHEAST CANADA WHILE A SECOND JET MAX BEGINS TO
LIFT OUT FROM THE WESTERN GULF AREA LATE TONIGHT.  WEAK UPPER LEVEL
DIVERGENCE EXTENDS ACROSS SOUTHERN WISCONSIN.  ONE MID LEVEL 500 MB
SHORTWAVE MOVES ACROSS SOUTHERN WISCONSIN THIS MORNING TO JUST EAST
OF LAKE SUPERIOR THIS EVENING. THIS LIFTS AN AREA OF MODERATE 700 MB
UPWARD MOTION ACROSS SOUTHERN WISCONSIN THIS MORNING TO CENTRAL AND
NORTHERN WISCONSIN THIS AFTERNOON. WITH LITTLE IN THE WAY OF UPWARD
MOTION TONIGHT.

A 700 MB DRY WEDGE LIFTS NORTHEAST AFFECTING SOUTHEAST WISCONSIN THE
MOST.  FAR SOUTHEAST WISCONSIN IS ON THE EDGE OF 850 MB AND EVEN 925
MB DRYING.  AS A RESULT THERE IS A CHANCE FOR THE FAR SOUTHEAST TO
GET ENOUGH INTO THE WARM SECTOR TO CAUSE SOME BREAKS IN THE LOW
OVERCAST.

THE WEAK OCCLUDED LOW MOVES ACROSS SOUTHERN WISCONSIN THIS
MORNING...REACHING NORTHEAST WISCONSIN LATE THIS AFTERNOON. THIS
RESULTS IN THE RAIN DIMINISHING FROM SOUTH TO NORTH LATER THIS
MORNING.

WEDNESDAY AND WEDNESDAY NIGHT... FORECAST CONFIDENCE MEDIUM.

A SECONDARY UPPER LOW WILL DEVELOP AT THE BASE OF THE ELONGATED
TROUGH OVER THE AR/MO AREA ON WEDNESDAY AND TRACK NORTHEAST THROUGH
LOWER MICHIGAN WED EVENING. A 150 KT UPPER JET STREAK WILL LEAD TO
SURFACE CYCLOGENESIS OVER THE EASTERN GREAT LAKES. THE EXACT TRACK
OF THE SURFACE LOW IS STILL UP FOR DEBATE... EVEN FOR ONE DAY OUT.
THE MODELS HAVE HAD A REALLY HARD TIME WITH THIS SYSTEM. THE 00Z
RUNS YESTERDAY SHOWED A SLIGHTLY MORE EASTERN TRACK THAN THE
12/18/00Z RUNS YESTERDAY AND TODAY. THE 00Z ECWMF TODAY SHIFTED BACK
TO THE EAST. THE GFS HAS BEEN VERY CONSISTENT IN A WESTERLY TRACK OF
THE SURFACE LOW AND HAS BEEN PAINTING THE MOST QPF OVER SOUTHEAST WI
COMPARED TO ALL OF THE OTHER MODELS FOR THE PAST WEEK. THE CANADIAN
MODEL IS LIKE THE GFS IN ITS MOST RECENT RUNS. THE NAM IS THE
SLOWEST AND FARTHEST EAST... ALTHOUGH THE 06Z NAM RUN LOOKS VERY
SIMILAR TO THE 00Z ECWMF.

SOUTHEAST WI WILL BE ON THE FAR WESTERN PERIPHERY OF THIS SYSTEM.
THE MAIN QUESTION IS WHETHER OR NOT THE AXIS OF HIGHEST QPF WILL
CLIP SOUTHEAST WI. A MODEL COMPROMISE SUGGESTS THAT THE AXIS WILL
LAND SOMEWHERE IN NORTHEAST IL. I USED A BLEND OF MODELS FOR QPF FOR
A TOTAL OF A HALF INCH IN THE FAR SOUTHEAST CORNER OF WI... MOST OF
IT FALLING WEDNESDAY AFTERNOON.

THE NEXT QUESTION IS WHAT TYPE OF PRECIP. SURFACE TEMPS WILL BE JUST
ABOVE FREEZING DURING THE DAY WED. THE BOUNDARY LAYER NEAR THE LAKE
WILL ALSO REMAIN MILD LONGER DUE TO WARMING FROM NORTHEAST FLOW OFF
THE LAKE. TEMPS ALOFT WILL BE JUST BELOW FREEZING. SNOW WILL BE
INTRODUCED ALOFT AND MAY MELT BEFORE IT REACHES THE GROUND.
THEREFORE... THE HEAVIER PRECIP WED AFTERNOON COULD BEGIN AS RAIN
AND THEN CHANGE OVER TO MODERATE SNOW AS THE AIR DYNAMICALLY COOLS.
PRECIP WILL HAVE TO INITIALLY OVERCOME MID LEVEL DRY AIR IN THE
MORNING. THE BEST FORCING WILL BE WED AFTERNOON WHEN THE UPPER LEVEL
LOW TRACKS ACROSS SOUTHWEST LOWER MICHIGAN. SOUTHEAST WI LANDS IN
THE DEFORMATION ZONE OF THE SYSTEM. EVEN THE DRIER NAM SHOWS A
CROSSHAIR SIGNATURE IN BUFKIT AT KENW FOR THE POTENTIAL FOR A SHORT
DURATION MODERATE SNOWFALL.

SNOW RATIOS WILL BE STEADILY FALLING THROUGH THE AFTERNOON AND I
WENT WITH A 10:1 RATIO BY 6 PM WED. TOTAL SNOWFALL COULD BE AROUND 2
INCHES IN FAR SOUTHEAST WI WITH A SHARP CUTOFF TO THE WEST. THERE IS
STILL A LOT OF UNCERTAINTY. A HIGHER SNOWFALL RATE DURING THE LATE
AFTERNOON ON CHRISTMAS EVE WOULD HAVE AN IMPACT ON RUSH HOUR TRAFFIC
AND HOLIDAY TRAVEL. EXPECT GUSTY NORTHERLY WINDS IN THE AFTERNOON AS
WELL. STAY TUNED FOR UPDATES.

THE PRECIP WILL PULL OUT QUICKLY TO THE EAST WEDNESDAY EVENING WITH
DRY WEATHER ARRIVING.

LONG TERM...

CHRISTMAS DAY...FORECAST CONFIDENCE HIGH.

ALL THE MODELS ARE IN GOOD AGREEMENT THAT THURSDAY WILL BE DRY AND
MILD WITH A HIGH PRESSURE RIDGE BRIEFLY MOVING OVERHEAD. WE MIGHT
EVEN SEE A LITTLE SUNSHINE. THE LAST TIME WE SAW WIDESPREAD SUNSHINE
WAS OVER TWO WEEKS AGO.

FRIDAY... FORECAST CONFIDENCE MEDIUM.

SURFACE LOW PRESSURE... IN RESPONSE TO A DIGGING UPPER TROUGH OVER
THE INTERMOUNTAIN WEST... WILL DEVELOP IN THE CENTRAL PLAINS THU
NIGHT AND TRACK NORTHEAST ACROSS CENTRAL WI FRI AFTERNOON/EVENING AS
IT WEAKENS. SOUTHERN WI WILL BE IN THE DRIER WARM SECTOR FOR FRIDAY.
THEN THERE WILL BE A CHANCE FOR LIGHT PRECIP FRIDAY NIGHT WITH THE
COLD FRONT. THE TEMP PROFILE SUGGESTS A RAIN THAT TRANSITIONS TO
SNOW OR A RAIN/SNOW MIX FRI EVENING/NIGHT BEFORE ENDING.

SATURDAY THROUGH MONDAY... FORECAST CONFIDENCE HIGH.

SURFACE HIGH PRESSURE AND DRY WEATHER WILL DOMINATE FOR THE WEEKEND
INTO MONDAY... BUT TEMPERATURES WILL BE BELOW AVERAGE.

AVIATION/12Z TAFS/...

IFR/LIFR CIGS/VSBYS IN RAIN AND FOG THIS MORNING AS LOW PRESSURE
MOVES ACROSS SOUTHERN WISCONSIN.

EXPECT TO SEE CIGS LIFT TO MVFR LEVELS OR EVEN VFR IN THE LATE
MORNING/EARLY AFTERNOON IN PORTIONS OF SOUTHEAST WISCONSIN.  AREAS
NORTH AND WEST OF MADISON MAY STAY IFR.

ANY VFR IN THE SOUTHEAST SHOULD LOWER BACK TO MVFR LEVELS AS COLDER
AIR WRAPS BACK IN UNDER SURFACE LOW AS IT LIFTS OFF TO THE
NORTHEAST.

MARINE...

PERSISTENT ONSHORE FLOW WILL KEEP WAVES HIGH INTO THE MORNING...WITH
WINDS EASING AS A BAGGY GRADIENT EXTENDS AROUND SURFACE LOW MOVING
ACROSS SOUTHERN WISCONSIN.

A SECONDARY LOW LIFTING NORTH INTO LOWER MICHIGAN WILL BRING SMALL
CRAFT ADVISORY CONDITIONS WEDNESDAY AFTERNOON INTO THURSDAY
MORNING WITH BRISK NORTH WINDS AND HIGH WAVES ACROSS SOUTHERN LAKE
MICHIGAN.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...NONE.
LM...SMALL CRAFT ADVISORY UNTIL 6 PM CST THIS EVENING FOR LMZ643-644.

&&

$$

UPDATE...DAVIS
TODAY/TONIGHT AND AVIATION/MARINE...99
WEDNESDAY THROUGH MONDAY...99


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