Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 211602 AAA
AFDMKX

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI
1002 AM CST WED JAN 21 2015

.UPDATE...

LIGHT SNOW CURRENTLY FALLING OVER SOUTHERN WISCONSIN WILL LINGER
THROUGH THE MORNING...BUT WILL CLEAR OUT BY THE AFTERNOON. EXPECT
AN ADDITIONAL DUSTING TO A COUPLE TENTHS OF NEW SNOW. SKIES WILL
STAY OVERCAST THROUGHOUT THE DAY. TEMPERATURES APPEAR TO BE ON
TRACK WITH OUR FORECAST...WITH LOWER 30S ALONG THE SOUTHERN HALF
OF OUR CWA AND UPPER 20S ACROSS THE NORTHERN HALF FOR TODAYS HIGH
TEMPS.

&&

.AVIATION/18Z TAFS/...

A BAND OF LIGHT SNOW IS SLOWLY MOVING SOUTH ACROSS SOUTHERN
WISCONSIN THIS MORNING. ADDITIONAL SNOW ACCUMULATIONS WILL RANGE
FROM A DUSTING TO A FEW TENTHS OF AN INCH. THIS SNOW WILL PERSIST
THROUGH THE MORNING HOURS...AND MOVE OUT BY THE AFTERNOON. IFR
CONDITIONS WILL PERSIST THIS MORNING WITH CIGS NEAR 800 FT. EXPECT
LOW-END MVFR CONDITIONS IN THE EVENING THROUGH THE THURSDAY
MORNING HOURS.

&&

.PREV DISCUSSION... /ISSUED 332 AM CST WED JAN 21 2015/

SHORT TERM...

TODAY...FORECAST CONFIDENCE - MEDIUM.

SFC LOW PRESSURE OVER NORTHEAST IA AND ASSOCD MID-LEVEL SHORT WAVE
WILL FOLLOW SIMILAR PATH TO TUESDAY MORNING SYSTEM AND TRACK TO THE
SOUTH OF SRN WI THIS MORNING. COLUMN MOISTURE SLIGHTLY DEEPER
RESULTING IN MORE WIDESPREAD -SN...HOWEVER MAJORITY OF SYNOPTIC
SCALE FORCING WITH THIS SYSTEM WILL REMAIN TO THE SOUTH.  WEAK LAYER
Q-VECTOR CONVERGENCE EXITS SRN WI EARLY THIS MRNG AS DOES WEAK LOW
LEVEL FRONTOGENETICAL LIFT IN BETTER DENDRITIC SNOW GROWTH REGION.
MID-LEVEL DEFORMATION ALSO JUST GRAZES SRN WI EARLY THIS MRNG BEFORE
RAPID DIMINISHING TREND.  HENCE WEAK FRONTOGENETICAL BANDS THRU 12Z
MAY DEPOSIT UP TO 1 INCH CENTRAL AND SOUTH.  FAR NORTHEAST SHOULD
ONLY SEE A DUSTING TO A FEW TENTHS. MAY ALSO BE A BRIEF PERIOD OF
-ZL/-ZR MAINLY IN THE SOUTHWEST CWA EARLY THIS MRNG AS IR SATELLITE
ENHANCEMENT SHOWING WARMER CLOUD TOPS IN THIS REGION AT 08Z.
OTHERWISE...ICE CRYSTAL SEEDING FROM HIGHER CLOUDS HAS BEEN ERODING
PATCHY -ZL IN THE EAST LAST FEW HOURS AS SEEN BY INCREASING
CORRELATION COEFFICIENTS TOWARDS 1.

EXPECT SNOW LIQUID RATIOS AROUND 15 TO 1...HIGHEST AMOUNTS PERHAPS
EXCEEDING AN INCH IN THE SOUTHWEST CWA THROUGH EARLY MRNG. EXPECT
DIMINISHING TREND TO -SN AFTER 13Z OR SO WITH ONLY A SMALL CHANCE
FOR LINGERING -SN THIS AFTN.

TONIGHT...FORECAST CONFIDENCE - HIGH.

LOW TO MID LEVEL MOISTURE LINGERS THROUGH MOST OF TONIGHT AS WEAK
MID-LEVEL TROF SAGS SOUTH THRU SRN WI.  WL CONTINUE FLURRY MENTION
THROUGH 06Z BUT KEEP CLOUDS LINGERING THROUGH THE NIGHT ALONG WITH
MILDER TEMPS.

THURSDAY THROUGH FRIDAY NIGHT... FORECAST CONFIDENCE MEDIUM.

MID LEVEL DRY AIR WILL SPREAD INTO SOUTHERN WI IN THE WAKE OF A
DEPARTING UPPER LOW THU MORNING. ONE MORE UPPER TROUGH WILL DROP
THROUGH THE REGION THU AFTERNOON WHICH WILL HELP TO STEEPEN LOW
LEVEL LAPSE RATES FOR SOME STRATOCUMULUS CLOUDS AND MAYBE A FEW
FLURRIES. THE NAM HANGS ONTO THE CLOUDS LONGER THAN THE GFS.
MEANWHILE... SURFACE HIGH PRESSURE WILL BE SLIDING ACROSS THE
MIDWEST. WITH 925MB TEMPS AROUND -6C THU EVENING AND A PERIOD OF
CLEAR SKIES AND LIGHT WINDS... EXPECT TEMPS TO DROP QUICKLY. LOWERED
MIN TEMPS DOWN TO AROUND 20.

THE PRESSURE GRADIENT WILL BEGIN TO INCREASE OVER SOUTHERN WI AS A
SURFACE LOW PRESSURE TROUGH APPROACHES FROM THE NORTHERN PLAINS LATE
THU NIGHT INTO FRI MORNING. TEMPS ARE EXPECTED TO RISE INTO THE
UPPER 30S BY FRI AFTERNOON ON GUSTY SOUTHWEST WINDS. ANY PRECIP
ASSOCIATED WITH THE LEADING EDGE OF THE TROUGH WILL LIKELY NOT MAKE
IT TO THE GROUND GIVEN BONE DRY LOW LEVEL AIR. BEHIND THE SURFACE
TROUGH... MID CLOUDS DISAPPEAR AND LOW CLOUDS SPREAD INTO SOUTHERN
WI FRI LATE EVENING. IF THE LOW LEVEL MOISTURE IS DEEP ENOUGH...
THERE MAY BE SOME LIGHT SNOW OR DRIZZLE ASSOCIATED WITH THEM. THERE
ARE STILL TIMING DIFFERENCES AND MOISTURE DIFFERENCES BETWEEN THE
MODELS SO STAY TUNED.

LONG TERM...

SATURDAY... FORECAST CONFIDENCE MEDIUM.

A NORTHWEST FLOW PATTERN WILL PERSIST OVER THE UPPER MIDWEST THROUGH
THE WEEKEND. SATURDAY WEATHER WILL BE QUIET BUT EXPECT LOW CLOUDS TO
LINGER UNDER CYCLONIC FLOW.

TEMPS WILL BE MILD SATURDAY WITH HIGHS IN THE UPPER 30S. THEN A
BACKDOOR COLD FRONT WILL DROP INTO SOUTHERN WI LATE SATURDAY NIGHT
AND CAUSE A CHANGE IN WIND DIRECTION FROM WEST TO EAST.

SUNDAY THROUGH TUESDAY... FORECAST CONFIDENCE MEDIUM.

A STRONGER SHORTWAVE WILL DROP DOWN FROM THE NORTHERN PLAINS AND
BRING A SWATH OF PRECIP ACROSS MN/IA/IL AND SOME PORTION OF WI LATE
SATURDAY NIGHT THROUGH SUNDAY NIGHT OR MONDAY MORNING. THERE IS
STILL QUITE A BIT OF UNCERTAINTY SINCE MODELS CANNOT AGREE ON THE
TRACK OF THE SURFACE LOW. THE ECWMF IS CONTINUING ITS TRACK THROUGH
SOUTH CENTRAL WI... THE GFS THROUGH IOWA AND THE CANADIAN THROUGH
UPPER MICHIGAN. KEPT THE CHANCE FOR SNOW IN THE FORECAST FOR
SOUTHERN WI.

NORTHWEST FLOW WILL PERSIST OVER THE REGION THROUGH MUCH OF NEXT
WEEK. ANOTHER SHORTWAVE MAY BRING LIGHT SNOW TO SOUTHERN WI AGAIN
MONDAY AFTERNOON/EVENING... WITH YET ANOTHER CHANCE TUE AFTERNOON.

AVIATION/12Z TAFS/...

AREAS OF IFR CIGS ASSOCD WITH -SN WILL DIMINISH THIS MRNG YIELDING
TO WIDESPREAD MVFR CIGS.  VSBYS MOSTLY 2SM OR BETTER BUT MAY BE
BRIEFLY 1SM IN WEAK FRONTOGENETICAL BAND EARLY THIS MRNG.  OTRW
EXPECT IMPROVING VSBYS THIS MRNG AS -SN DIMINISHES.

&&

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

$$

UPDATE...JTS
TODAY/TONIGHT AND AVIATION/MARINE...MBK
THURSDAY THROUGH TUESDAY...MRC


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