FXUS63 KMKX 222131
AFDMKX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI
331 PM CST TUE DEC 22 2009
.SHORT TERM...
TONIGHT...CONFIDENCE: MEDIUM
WATER VAPOR IMAGERY SHOWS SHORTWAVE THAT BROUGHT THE LIGHT SNOW TO
SOUTHERN WISCONSIN WAS EXITING THE NORTHEAST ILLINOIS AREA. ANY
ACCUMULATION SNOW WILL BE OVER LATE THIS AFTERNOON.
EAST WIND OFF LAKE MICHIGAN WITH DELTA T JUST BELOW CONDITIONAL
CATEGORY SO SOME FLURRIES POSSIBLE. HOWEVER DESPITE SATURATED
SOUNDINGS BELOW 800 MB...LOW LEVEL INVERSION LOWERS TO BELOW 900
MB. EAST WIND FETCH IS MINIMAL...BUT RATHER STEEP LAPSE RATES
BELOW 925 MB.
DEEP LOW LEVEL MOISTURE BUT ICE CRYSTAL REGION IS NOT SATURATED.
THEREFORE SOME PATCHY FREEZING DRIZZLE POSSIBLE.
.WEDNESDAY...CONFIDENCE: MEDIUM
FOCUS IS ON STRONG SHORTWAVE OVER THE SOUTHWEST UNITED STATES.
UPPER RIDGE OVER WISCONSIN SHOULD KEEP MUCH OF THE PRECIPITATION
SOUTH INITIALY ON WEDNESDAY. PERSISTENT EAST FLOW OFF LAKE
MICHIGAN CONTINUES. INVERSION LOWERS A LITTLE MORE...BUT A FEW
FLURRIES STILL POSSIBLE NEAR THE LAKE. NAM NOW IS FASTER WITH PUSH
OF PRECIP NORTH DUE TO DEVELOPING LOW LEVEL JET. ALSO UPPER LEVEL
DIFLUENCE BECOME RATHER PRONOUNCED AS UPPER RIDGE AXIS MOVES OFF
TO THE NORTHEAST.
THICKNESS/850MB TEMPS INDICATE A MIX OF PRECIPITATION TYPES.
INITIALLY SURFACE TEMPERATURES INLAND WILL BE BELOW FREEZING.
TEMPERATURES ARE CLOSE TO ISOTHERMAL OVER A LARGE PORTION OF THE
ATMOSPHERIC COLUMN. SNOW CRYSTAL REGION IS NEAR 600 MB AND
ABOVE...BUT BEST LIFT IS IN THE MID LEVELS SO SOME SNOW STILL
EXPECTED. PREFER NAM SOUNDINGS WITH TEMPERATURE PROFILES IN THE
WEDNESDAY NIGHT AND THURSDAY TIME FRAME. TEMPERATURES NOW ABOVE
ZERO CELSIUS FROM 800 TO 900MB. EXPECT THE SNOW TO QUICKLY
BECOME MIXED WITH SLEET AND FREEZING RAIN. STRONG WINDS OFF LAKE
MICHIGAN SHOULD KEEP SURFACE TEMPERATURES ABOVE FREEZING NEAR THE
LAKE.
ENOUGH ICING POTENTIAL FOR A WATCH. EXPECT EVENT WILL BE MAINLY
ADVISORY OR LOW END WARNING...MAINLY FOR THE FREEZING RAIN AND
SLEET. AREAS NEAR LAKE MICHIGAN FROM MILWAUKEE TO KENOSHA MAY NOT
SEE MUCH IF ANY ICING DUE TO THE EAST WINDS OFF LAKE MICHIGAN.
WATCH FOR THOSE COUNTIES IS FOR INLAND AREAS.
THURSDAY AND CHRISTMAS...CONFIDENCE: MEDIUM
MODELS FOCUSING ON A SURFACE TRACK FROM IOWA TO CENTRAL
WISCONSIN.
GFS AND NAM SHOW A STRONG LOW BECOMING WELL OCCLUDED AND
WEAKENING BY THE TIME IT REACHES WISCONSIN FRIDAY NIGHT. ECMWF IS
AN OUTLIER WITH A MUCH STRONGER LOW NEAR WATERLOO IOWA FRIDAY
EVENING. PREFER THE GFS/NAM. GREATEST QPF WILL FALL THURSDAY
NIGHT...BUT BY THIS TIME MUCH OF THE PRECIPITATION WILL HAVE
CHANGED TO RAIN.
AS UPPER LOW APPROACHES DYNAMIC COOLING WILL AGAIN CHANGE THE
PRECIPITATION TO SNOW DURING THE DAY FRIDAY. BUT BY THIS TIME THE
HEAVIEST PRECIPITATION WILL BE TO THE NORTH AND NORTHEAST...AND IN
THE DEFORMATION ZONE TO THE WEST. ANY WARNING CRITERIA WILL BE WITH
THE INITIAL FREEZING RAIN AND SLEET EVENT.
.LONG TERM...
SATURDAY AND SUNDAY...CONFIDENCE: MEDIUM
SURFACE LOW MOVES OFF TO THE NORTHEAST AND LINGERING LIGHT SNOW
DIMINISHES TO FLURRIES UNDER COLD AIR ADVECTION IN THE WESTERN
SECTION OF UPPER LOW/TROUGH.
MONDAY...CONFIDENCE: MEDIUM
SURFACE HIGH OVER THE PLAINS IS SLOW TO BUILD INTO THE UPPER
MISSISSIPPI VALLEY WITH COLD AIR ADVECTION CONTINUING ON THE BACK
SIDE OF THE DEPARTING LOW.
&&
.AVIATION...
EXPECT THE LIGHT SNOW TO TAPER OFF BY EVENING ACROSS THE
TAF SITES. AN EXCEPTION WOULD BE AT KMKE AND KENW...WHERE VERY LIGHT
LAKE EFFECT SNOW SHOWERS MAY PERSIST UNTIL AROUND 06Z WEDNESDAY.
EXPECT VFR VISIBILITIES AND MVFR CEILINGS ACROSS THE AREA TONIGHT
AND WEDNESDAY. THERE IS A SMALL CHANCE OF FREEZING DRIZZLE ACROSS
THE AREA TONIGHT UNTIL AROUND 15Z WEDNESDAY...BUT FEEL CHANCES ARE
TOO SMALL TO INCLUDE IN TAFS AT THIS TIME.
EASTERLY WINDS WILL GRADUALLY INCREASE TONIGHT INTO WEDNESDAY...WITH
GUSTS TO 23 KNOTS EXPECTED AFTER 15Z WEDNESDAY. MODERATE SNOW WITH
IFR CEILINGS AND VISIBILITIES TO SPREAD NORTHEAST INTO FAR SOUTHERN
WISCONSIN LATER WEDNESDAY AFTERNOON...BUT SHOULD NOT REACH TAF SITES
UNTIL AFTER 00Z THURSDAY.
&&
.MARINE...
SMALL CRAFT ADVISORY CONTINUES FROM 09Z WEDNESDAY UNTIL
12Z THURSDAY. TIGHTENING SURFACE PRESSURE GRADIENT WITH APPROACHING
STRONG LOW PRESSURE WILL BRING PERSISTENT EASTERLY WINDS OF 15 TO 25
KNOTS...WITH SOME 30 KNOT GUSTS POSSIBLE ON WEDNESDAY NIGHT. HIGH
WAVES BUILDING TO 6 TO 10 FEET ARE POSSIBLE BY WEDNESDAY NIGHT.
A GALE WATCH HAS BEEN POSTED FOR THURSDAY AND THURSDAY NIGHT...AS
WINDS VEER SOUTHEAST. GOOD LOW LEVEL MIXING WILL ALLOW FREQUENT
GUSTS OF 35 KNOTS TO POSSIBLY MIX DOWN. THE HIGH WAVES WILL CONTINUE
DURING THIS TIME.
SMALL CRAFT ADVISORIES WILL LIKELY BE NEEDED FOR FRIDAY THROUGH
SATURDAY...AS THE BRISK SOUTHEAST WINDS SHIFT SOUTH ON
FRIDAY...LASTING THROUGH SATURDAY. WAVES WILL REMAIN HIGH DURING
THIS PERIOD.
&&
.MKX WATCHES/WARNINGS/ADVISORIES...
WI...WINTER STORM WATCH FROM WEDNESDAY AFTERNOON THROUGH THURSDAY
AFTERNOON FOR WIZ062-067-068.
WINTER STORM WATCH FROM WEDNESDAY EVENING THROUGH THURSDAY
AFTERNOON FOR WIZ046-047-056>058-063-064-069-070.
WINTER STORM WATCH FROM WEDNESDAY EVENING THROUGH THURSDAY
MORNING FOR WIZ066-071-072.
WINTER STORM WATCH FROM WEDNESDAY EVENING THROUGH THURSDAY
AFTERNOON FOR WIZ051-052-059-060-065.
LM...SMALL CRAFT ADVISORY FROM 3 AM WEDNESDAY TO 6 AM CST THURSDAY
FOR LMZ643>646.
&&
$$
SHORT/LONG TERM...06/HENTZ
AVIATION/MARINE...07/WOOD
