FXUS63 KMKX 112114
AFDMKX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI
315 PM CST FRI DEC 11 2009

.SHORT TERM /TONIGHT THROUGH MONDAY/...
TWO EVENTS TO WORRY ABOUT FOR THE PERIOD.  HOWEVER...INITIALLY... 
SOME CONSTERNATION OVER OVERNIGHT LOW TEMPERATURES. TEMPS SHOULD 
RAPIDLY LOSE 5 TO 15 DEGREES THROUGH EARLY EVENING...THEN BEGIN TO 
LEVEL OFF AS LOW LEVEL WARM AIR ADVECTION BEGINS TO INCREASE.  
DESPITE LOW LEVEL TEMP INVERSION...INCREASING WAA AND 3 TO 8KT SLY 
WINDS SHOULD PREVENT LOW TEMPS FROM GETTING COMPLETELY OUT OF HAND. 
A FEW MID LEVEL CLOUDS POSSIBLE AS WELL.  WINDS AND TEMPS LIKELY TO 
DROP WIND CHILL TO 5 TO 15 BLO MOST AREAS TNGT.

GOES SOUNDER SHOWS VERY DRY AIRMASS OVER REGION WITH PWAT VALUES 
LESS THAN TWO TENTHS INCH.  HIGHER PWAT VALUES HAVE NUDGED FARTHER 
NORTH INTO THE SRN PLAINS...HOWEVER SURFACE DEWPTS STILL HOLDING IN 
THE MIDDLE 20S IN THIS AREA.  PWAT VALUES EXPECTED TO APPROACH 0.50 
INCH SAT NGT AS LOW LEVEL WINDS INCREASE TO 30 TO 40KTS EARLIER ON 
SAT.  UPSTREAM SHORT WAVE TROUGH APPARENT ON WV IMAGERY OVER SWRN NV 
TRACKS ENE...CROSSING SRN WI SAT NGT. Q-VECTOR CONVERGENCE INCREASES 
TO AROUND -5 TO -10 UNITS DURING THIS PERIOD.  INITIAL RAPID 
MOISTENING OF BOUNDARY LAYER SHOULD RESULT IN EVAPORATIVE COOLING 
AND A PERIOD OF MOSTLY -SN DEVELOPING OVER SRN WI SAT EVE.  THE 
PERIOD OF -SN WL BE SHORT LIVED HOWEVER AS THE DEEPER MID LEVEL 
MOISTURE AND FORCING RACES EAST OF AREA SHORTLY AFT 
06Z/SUN...LEAVING BEHIND A MOIST LAYER BLO 5K FEET.  WE LOSE THE ICE 
CRYSTALS FALLING INTO THE CLOUD BEARING LAYER...HOWEVER SPEED AND 
DIRECTIONAL SHEAR NOTED NEAR THE TOP OF THE MOIST LAYER ALONG WITH 
THE APPROACHING WEAK SFC TROF MAY RESULT IN PATCHY FREEZING DRIZZLE 
LATER SAT NGT INTO EARLY SUN. COBB RATIOS APPEAR HIGH FOR THIS 
EVENT.  WOULD EXPC LOWER RATIOS AROUND 10-13 TO 1 TAKING INTO 
ACCOUNT THICKNESS. FOR NOW...WL GO WITH 1 INCH SNOW AMOUNTS 
CONSIDERING SWIFTNESS OF SYSTEM...AND QUESTIONS CONCERNING TIMING OF 
TOTAL COLUMN MOISTENING.

WEAK TROFFING LINGERS OVER SRN WI INTO MON AS WINDS BECOME ONSHORE.  
HOWEVER LAKE EFFECT THREAT MINIMAL DUE TO LOW DELTA-T AND MORE SELY 
WND COMPONENT IN THE LOW LEVELS.

SHORT WAVE TROUGH AND SURFACE LOW PRESSURE FORMS ALONG LINGERING 
BAROCLINIC ZONE OVER ERN NE SUN NGT AND TRACKS NORTHEAST.  WARMER 
AIR LINGERS IN THE LOW LEVELS ACROSS SRN WI SUN NIGHT INTO MONDAY.  
STRONGEST FORCING AND Q-VECTOR CONVERGENCE OF 10 TO 15 UNITS PASSES 
TO THE NORTH OF CWA.  LOW LEVEL THERMAL STRUCTURE FAVORS MIX OF 
PRECIP OVER SRN WI WITH A POTENTIAL FOR A PERIOD OF -ZL OR -ZR.  DUE 
TO UNCERTAINTY WITH THIS SYSTEM...KEPT POPS IN CHANCE CATEGORY FOR 
NOW WITH MIX ALL AREAS.  MAY RECEIVE A COUPLE INCHES IN THE NORTH.  
FORTUNATELY...THE WARMER TEMPS EXPECTED THE NEXT SEVERAL DAYS SHOULD 
HELP TO MELT THE HEAVY SNOW LINGERING FROM WED ON MOST TREES AND 
WIRES.
 
.LONG TERM/MONDAY NIGHT THROUGH FRIDAY/...
SECOND BLAST OF ARCTIC COLD POURS ACRS SRN WI AT THE START OF THE 
EXTENDED PD WITH 85H TEMPS FALLING TO 15 TO 20 BLO.  ECWMF SLOWER 
WITH MID LEVEL SHORT WAVE PASSING ACRS WI MAINLY TUE...WHILE MORE 
CONSISTENT GFS...UKMT AND CANADIAN FASTER WITH SHORT WAVE.  HOWEVER 
12Z RUN OF GFS MORE IN AGREEMENT WITH ECMWF.  SO WL ADD SMALL POPS 
FOR -SHSN AS THE COLD AIR BLASTS IN.

OTHERWISE AMPLIFYING LONG WAVE TROFFING OVER ERN CONUS/WRN ATLANTIC 
WILL RESULT IN UPSTREAM RIDGING AND QUIET CONDITIONS ACROSS THE 
UPPER MIDWEST FOR MID WEEK.  RIDGING EVENTUALLY BREAKS DOWN LATE IN 
THE WEEK.  DIFFICULT TO TIME MOISTURE RETURN AND WEAK IMPULSES BUT 
THREAT FOR PRECIPITATION WL INCREASE LATE IN THE WEEK.  FOR NOW...WL 
CONT DRY WORDING...BUT MAY NEED TO ADD PRECIP IN LATER FORECASTS.

GFS 5 DAY 5H MEANS SHOW SLIGHTLY NORTHWEST OF WEST ZONAL FLOW AVERGE 
BY NEXT WEEKEND.  UNSETTLED WEATHER LIKELY TO RETURN LEADING UP TO 
HOLIDAY...BUT TEMPS SHOULD BE WARMER...AT LEAST AT THE START OF THE 
WEEK. 

&&

.AVIATION...LITTLE CONCERNS OVER THE NEXT 24 HOURS AS HIGH PRESSURE 
SLIDES EAST. COULD SEE SOME MID OR HIGH CLOUDS SATURDAY 
AFTERNOON...BUT OTHERWISE SKIES SHOULD REMAIN MOSTLY CLEAR UNTIL 
SATURDAY EVENING AND OVERNIGHT WHEN LOW PRESSURE BRINGS A CHANCE FOR 
SOME MIXED PRECIP. THE NAM IS SUGGESTING NEAR 30 KTS OF 0-1 KFT BULK 
SHEAR LATER TONIGHT...BUT NOT SEEING THIS MUCH IN OTHER MODELS AND 
NAM IS BORDERLINE...SO WILL HOLD OFF ON MENTIONING IN TAFS.

&&

.MARINE...AS HIGH PRESSURE SLIDES EAST AND LOW PRESSURE APPROACHES 
FROM THE WEST...EXPECT A TIGHTENING PRESSURE GRADIENT TONIGHT AND 
SATURDAY...WITH BREEZY SOUTH TO SOUTHWEST WINDS. COULD MIX DOWN A 
FEW HIGHER GUSTS AND APPROACH SMALL CRAFT CONDITIONS...BUT THINGS 
LOOK TO MARGINAL AT THIS POINT TO ISSUE AN ADVISORY. WILL HAVE TO 
KEEP AN EYE ON THINGS TONIGHT AS THE GRADIENT BEGINS TO TIGHTEN.  

&&

.FORECAST CONFIDENCE...

TONIGHT THRU SUN...MEDIUM
SUN NIGHT...LOW-MEDIUM
MONDAY...LOW
EXTENDED PERIOD
MON NIGHT AND TUE...LOW
TUE NIGHT THRU THU...MEDIUM
FRI...LOW

&&

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

&&

$$
SHORT/LONG TERM...MBK
AVIATION/MARINE...DDV