FXUS63 KMKX 230931
AFDMKX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI
331 AM CST WED DEC 23 2009
.DISCUSSION...FORECAST FOCUS ON PRECIP TYPES/AMOUNTS ASSOCIATED WITH
APPROACHING STORM SYSTEM AND WHAT TO DO WITH HEADLINES. WINDOW OF
FREEZING RAIN POTENTIAL THE MAIN CONCERN TONIGHT INTO THURSDAY
MORNING.
TODAY AND TONIGHT- CONFIDENCE...LOW
STRONG STORM SYSTEM CLEARLY SEEN ON WATER VAPOR IN ARIZONA AND
NEW MEXICO. HIGH PRESSURE TO THE NORTHEAST PROVIDING AN EASTERLY
DRY COMPONENT. WITH CYCLOGENESIS REALLY GETTING GOING TODAY...850
LOW LEVEL JET INCREASES TOWARDS THE WESTERN CWA AND PRECIP IN THE
FORM OF SNOW DEVELOPS. NAM SUGGESTING MORE FREEZING RAIN/ICE
PELLET POTENTIAL RIGHT AT THE OUTSET...WILL HINT AT THIS. THOUGH
GFS MAY BE RIGHT WITH MORE EVAP COOLING WITH DRY EASTERLY FLOW HAVING
A SAY ON THE SOUNDINGS AT LEAST EARLY ON. 700 OMEGA ALSO SPIKES
UP. BUFKIT SOUNDINGS/THICKNESS AND ENERGY CONSIDERATIONS SHOW
MAINLY SNOW THROUGH 6Z...THEN THE ELEVATED WARM LAYER APPEARS AND
THE MODEL DIFFERENCES APPEAR AT THAT POINT. GFS SHOWS VERY LITTLE
IN THE WAY OF WARM LAYER WHILE THE NAM HAS AROUND 2C DURING MAX
QPF BUT DOESN/T GET TO 3C UNTIL 10 OR 11Z WHEN BULK OF PRECIP HAS
TRAILED OFF. MUCH OF THE QPF WILL BE CONTRIBUTING TO SNOW
PRODUCTION...AND NOT ENOUGH ICE PRODUCTION TO REACH WARNING
CRITERIA. MODEL CONSENSUS IS TO HAVE AROUND 0.30 INCH LIQUID
BETWEEN 0-6Z WITH INDICATIONS THAT WILL FALL AS SNOW WITH FAIRLY
LOW RATIOS. QPF MIN EVOLVES AFTER 6Z...AND WITH A SOUNDING THAT
SHOWS MORE OF A MIX OF PRECIP TYPES RATHER THAN PURE FREEZING
RAIN. CAN'T SIT ON A WATCH AT THIS POINT. FEEL MORE EVIDENCE
POINTING TOWARDS HIGH END ADVISORY THAN LOW END WARNING SO WILL GO
IN THAT DIRECTION.
CHRISTMAS EVE- CONFIDENCE...MEDIUM
NEXT SURGE ARRIVES WITH STRENGTHENING LOW LEVEL JET. BOUNDARY LAYER
TEMPS WILL SLOWLY MODIFY...THOUGH LINGERING PRECIP IN THE NORTHERN
CWA MAY STILL YET POSE SOME ICE CONCERN. MAIN ISSUE WILL BE IN THE
MORNING WITH LINGERING TEMPS NEAR 32...ESPECIALLY INLAND AWAY FROM
THE LAKE AND MUCH OF THE WESTERN AND NORTHERN CWA. THE NAM IS MUCH
WARMER WITH THE 850 THERMAL RIDGE. INTERESTING AND ODD LOOKING JET
COUPLING EVOLVES WITH INCREASING WITH MUCH OF THE FORCING WITH LOW
LEVEL FRONTOGENETICAL FORCING/MOISTURE ADVECTION. DECENT SURGE OF
DIFFERENTIAL CYCLONIC VORTICITY ADVECTION THURSDAY NIGHT BEFORE
SYSTEM CLOSES OFF AND GOES INTO PLOD MODE.
CHRISTMAS- CONFIDENCE...MEDIUM
WITH 850 THERMAL RIDGE ACROSS THE CWA TO START OFF THE DAY WILL GO
WITH MORNING HIGHS. 850 MILLIBAR COLD AIR ADVECTION WRAPS IN FROM
THE SOUTHWEST. THE RAIN CHANGING TO SNOW IDEA STILL LOOKS GOOD.
SATURDAY AND SUNDAY- CONFIDENCE...MEDIUM
UPPER LOW WILL BE SLOWLY PLODDING AROUND THE AREA WITH OCCASIONAL
SNOW SHOWERS A GOOD BET. 850 TEMPS RATHER CHILLY IN THE MINUS TEENS.
&&
.AVIATION...WEAK ISENTROPIC LIFT MAY PRODUCE PATCHY FLURRIES OR
FREEZING DRIZZLE THIS MRNG. OTHRW...EXPECT MOSTLY MVFR CIGS TO
CONTINUE TODAY...HOWEVER DRY MID LEVELS AND STRONG MIXING WL LIKELY
RESULT IN SEVERAL PERIODS OF VFR CIGS...ESPECIALLY IN THE EAST.
SURGE OF MOISTURE TNGT TIED TO SHORT WAVE FORCING WL RESULT IN MIX
OF SNOW...SLEET AND FREEZING RAIN TONIGHT...WITH LOWEST VSBYS IN
PRECIP AT KMSN. CIGS WL RETURN TO MVFR AND LWR.
&&
.MARINE...PRESSURE GRADIENT OVER SOUTHERN LAKE MICHIGAN WILL ONLY
FURTHER TIGHTEN THROUGH THU NIGHT BEFORE GRADUALLY WEAKENING IN
RESPONSE TO SLOWLY WEAKENING LOW PRESSURE THAT WILL BE AFFECTING THE
REGION THROUGH THE HOLIDAY WEEKEND. STEEP LOW LEVEL LAPSE RATES AND
STRONG WINDS JUST OFF THE SURFACE ARE EXPECTED TO REACH GALE
CRITERIA THU AFTN INTO FRI MRNG WHEN PRES GRADIENT WILL BE THE
TIGHTEST. HENCE SMALL CRAFT ADVISORY RAMPS UP TO GALE WARNING ON
THU.
&&
.MKX WATCHES/WARNINGS/ADVISORIES...
WI...WINTER WEATHER ADVISORY FROM 4 PM THIS AFTERNOON TO NOON CST
THURSDAY FOR WIZ062-067-068.
WINTER WEATHER ADVISORY FROM 6 PM THIS EVENING TO NOON CST
THURSDAY FOR WIZ046-047-056>058-063>066-069>072.
WINTER WEATHER ADVISORY FROM 9 PM THIS EVENING TO NOON CST
THURSDAY FOR WIZ051-052-059-060.
LM...SMALL CRAFT ADVISORY UNTIL NOON CST THURSDAY FOR LMZ643>646.
GALE WARNING FROM NOON THURSDAY TO NOON CST FRIDAY FOR
LMZ643>646.
&&
$$
SHORT/LONG TERM...PC
AVIATION/MARINE...MBK
