000 
FXUS63 KAPX 101549
AFDAPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GAYLORD MI
1150 AM EST MON JAN 10 2005

.SHORT TERM...RADAR SHOWING THAT MID LEVEL MOISTURE IS INCREASING 
INTO NRN LOWER. SNOW SHOWERS HAVE ALREADY DEVELOPED ACROSS EASTERN 
UPPER WITH MANY OBS SHOWING BETWEEN 1SM AND 4SM -SHSN. SNOW SHOWERS 
HAVE DEVELOPED AS FAR SOUTH AS CHEBOYGAN...BEAVER ISLAND AND 
CHARLEVOIX AS OF 11AM. ONGOING FORECAST LOOKS PRETTY GOOD BUT A FEW 
CHANGES WERE MADE. 

A TROUGH WAS SWINGING THROUGH MACKINAC ISLAND WITH A DRYING TREND 
NOTED BEHIND THIS FEATURE. THE DRY AIR IS EVIDENT ON THE OBS 
UPSTREAM AND THIS SHOULD LIMIT THE SNOW POTENTIAL TO SOME DEGREE. 
THIS MAY BE REFLECTED IN THE H9-H7 RH TOO...AS BOTH MODELS AND 
ESPECIALLY THE ETA DROPS THE RH OFF THROUGH THE AFTERNOON TO LESS 
THAN 40% ACROSS EASTERN UPPER BY 00Z. THIS WILL LIMIT THE AMOUNT OF 
TIME THAT SNOW CAN ACCUMULATE. THERMAL REGIMES REMAIN MORE FAVORABLE 
ACROSS EASTERN UPPER WHILE THE RH IS DECENT ENOUGH...SO WILL JUST 
LOWER SNOWFALL AMOUNTS EVERYWHERE. STILL EXPECT 1 TO 2 INCHES ACROSS 
EASTERN UPPER WITH A FEW LOCATIONS MAYBE SEEING 3 INCHES. IN NRN 
LOWER...A HALF INCH AT BEST IS EXPECTED. 

TEMPERATURES HAVE BEEN ADJUSTED BASED ON CURRENT OBS...BUT NO MAJOR 
CHANGES. THE PRIMARY WEATHER CONCERNS CONTINUE TO BE TUESDAY NIGHT 
AND WEDNESDAY NIGHT-THURSDAY TIMEFRAME AS 2 SEPARATE WEATHER SYSTEMS 
WILL BRING A VARIETY OF CONCERNS TO NRN MICHIGAN.  SMD 

&&

.PREV DISCUSSION ISSUED AT 430 AM EST MON JAN 10 2005...
FORECAST PROBLEMS FOR TODAY INCLUDE PRECIP TYPE EARLY...AND LAKE 
EFFECT SNOW POTENTIAL FOR BALANCE OF DAY.

AS OVER LAKE INSTABILITY INCREASES IN COLD ADVECTION 
REGIME...CONDITIONS SHOULD BECOME FAVORABLE FOR LAKE EFFECT SNOW 
SHOWERS IN WNW/NW FLOW AREAS. HOWEVER...DURING THE TRANSITION EARLY 
THIS MORNING...RADAR TRENDS HAVE INDICATED A SIGNIFICANT DECREASE IN 
PRECIP COVERAGE...AND 0Z MODEL SOUNDINGS SUGGEST MOIST MIXED LAYER 
WILL BE SHALLOW...STRUGGLING TO PENETRATE THE -10C LAYER...SO THERE 
MAY STILL BE A BIT OF FREEZING DRIZZLE MIXED WITH LIGHT SNOW 
SHOWERS/FLURRIES. HOWEVER...COVERAGE OF ANY FREEZING PRECIP SHOULD 
BE SUFFICIENTLY SPARSE TO ALLOW ALL HEADLINES TO BE DISCONTINUED IN 
THIS PACKAGE. MEANWHILE...MQT RADAR DEPICTS AN INCREASE IN LAKE 
EFFECT SNOW COVERAGE UPSTREAM...AND THIS REGIME SHOULD SPREAD EAST 
THIS MORNING...EVENTUALLY JUSTIFYING LIKELY POPS IN FAVORED WNW/NW 
FLOW AREAS. ACROSS THE EASTERN UP...LAKE-850 MB DELTA TS INCREASING 
TO AROUND 20C/INVERSION HEIGHTS INCREASING TO AROUND 4 KFT SHOULD 
SUPPORT 1-3 ACCUMULATION IN FAVORED AREAS FROM MID MORNING THROUGH 
LATE AFTERNOON. BRIEF PERIOD OF WEAK 700-500 MB QG FORCING/
ASSOCIATED 700 MB MOISTURE PROGGED TO PUSH THROUGH THE AREA EARLY 
THIS AFTERNOON MAY PRODUCE AN EXTRA INCH OR TWO IN A FEW 
LOCATIONS...BUT MODEL SOUNDINGS DEPICT ONLY A SUBTLE RESPONSE TO 
THIS FEATURE...SO WILL LEAVE DECISION TO RAISE AMOUNTS TO DAY SHIFT 
BASED ON TRENDS LATER THIS MORNING. SOUTH OF THE STRAITS...LAKE-850 
MB DELTA TS STRUGGLE TO REACH 15C...WHILE INVERSION HEIGHTS REMAIN 
AT OR BELOW 3 KFT...BARELY SUFFICIENT TO PUSH INTO THE -10C TO -12C 
LAYER...SO I CUT SNOW AMOUNTS FROM THE PREVIOUS FORECAST TO AROUND 
AN INCH IN FAVORED WNW AREAS. AWAY FROM FAVORED AREAS...MAY BE 
NOTHING MORE THAN FLURRIES FOR THE REST OF THE DAY. 

LONG TERM...VERY COMPLEX FORECAST SCENARIO FROM LATE TONIGHT THROUGH 
THURSDAY...WITH PRIMARY FORECAST PROBLEMS RANGING FROM POPS LATE 
TONIGHT...PRECIP TYPE TUESDAY THROUGH WEDNESDAY MORNING...PROSPECTS 
FOR HEAVY RAIN ON SNOW COVER WEDNESDAY NIGHT...THEN MAGNITUDE OF 
COLD ADVECTION IN WAKE OF COLD FROPA THURSDAY.

AFTER A FEW LINGERING FLURRIES/LIGHT SNOW SHOWERS ACROSS
THE NORTH THIS EVENING...SHOULD BE A PERIOD OF SEVERAL HOURS WITH NO 
PRECIP AS HIGH PRESSURE PASSES OVER THE REGION. TEMPS WILL BE 
TRICKY...THIS FORECAST HOLDS LOW CLOUDS OVER AREA UNDER SUBSIDENCE 
INVERSION...WITH LOWS IN THE SINGLE DIGITS/TEENS MOST AREAS...BUT 
ANY CLEARING THAT OCCURS MAY SUPPORT ISOLATED LOWS CLOSER TO ZERO.
THEN...AFTER SURFACE HIGH PUSHES EAST AFTER MIDNIGHT...0Z ETA/GFS 
DEPICT WEAK SYNOPTIC FORCING...AS DEPICTED BY 280-295K ISENTROPIC 
ASCENT...850-700 MB FRONTOGENESIS...700-500 MB QG FORCING AND UPPER 
DIVERGENCE IN RIGHT REAR QUAD OF 120+ KNOT 300 MB JET MAX. MODEL 
SOUNDINGS ACROSS THE SOUTH BY MOISTENING...ENOUGH TO GENERATE SOME 
LIGHT SNOW BY 9Z...SO LOW CHANCE POPS ARE JUSTIFIED SOUTH OF M-72 
LATE TONIGHT.

0Z GFS/ETA SOLUTIONS DIVERGE TUESDAY MORNING...WITH THE ETA 
DEPICTING A QUICK TRANSITION TO MID LEVEL DRYING...LEAVING ONLY SOME 
DRIZZLE/FREEZING DRIZZLE...WHILE THE GFS DEPICTS DEEPER MOISTURE/A 
CONTINUED CHANCE OF SNOW. WITHOUT A GREAT DEAL OF CONFIDENCE IN 
EITHER SCENARIO...THIS FORECAST WILL COMPROMISE...WITH A CHANCE OF 
SNOW OR FREEZING DRIZZLE MOST AREAS. 

SCENARIO BECOMES MORE COMPLICATED TUESDAY AFTERNOON AND ESPECIALLY 
TUESDAY NIGHT INTO WEDNESDAY MORNING...AS NEXT SHORT OF DEEP LAYER 
ASCENT...STRONGER THAN WHAT IS FORECAST TO OCCUR LATE TONIGHT INTO 
TUESDAY MORNING...PUSHES INTO THE REGION AHEAD OF SURFACE WAVE 
LIFTING NE FROM THE MID MS RIVER VALLEY INTO THE SOUTHERN LAKES. 
THE BASIC DIFFERENCES BETWEEN THE GFS AND THE ETA CENTER ON 
DEPICTIONS OF THE SURFACE WAVE...WITH A STRONGER ETA PUSHING MUCH 
WARMER AIR INTO THE REGION...VERSUS THE WEAKER GFS WHICH HOLDS 
COLDER AIR OVER THE REGION. IN BOTH CASES...AT LEAST LIKELY POPS ARE 
IN ORDER FOR ALL BUT THE EASTERN UP. CONFIDENCE IN EITHER SOLUTION 
IS NOT HIGH ENOUGH TO DOMINATE THE FORECAST...SO A COMPROMISE ONCE 
AGAIN APPEARS REASONABLE...WITH SNOW CHANGING TO MIXED PRECIP AT 
LEAST ACROSS THE SOUTHERN 1/2 OF THE FORECAST AREA. WITH THE 
PROSPECT FOR ELEVATED WARM ADVECTION/SURFACE TEMPERATURES AT OR 
BELOW FREEZING...THIS COULD BECOME A SIGNIFICANT ICE EVENT FOR SOME 
PART OF NORTHERN LOWER MICHIGAN...ESPECIALLY SOUTH OF M-32...BUT 
THERE REMAINS TOO MUCH UNCERTAINTY TO JUSTIFY A 4TH PERIOD WATCH AT 
THIS POINT.  

THE 0Z ETA AND GFS AGREE THAT MIX LEVELS WILL DRY OUT FOR A TIME 
WEDNESDAY MORNING...SO A MENTION OF DRIZZLE/FREEZING DRIZZLE IS 
JUSTIFIED. OTHERWISE...MIXED PRECIP MAY LINGER INTO THE 
MORNING...THUS ADJUSTED THE FORECAST ACCORDINGLY. 

WEDNESDAY AFTERNOON AND WEDNESDAY NIGHT...STRONGEST SYSTEM OF THE 
WEEK WILL PUSH NE THROUGH STRONG BAROCLINIC ZONE FROM CENTRAL PLAINS 
THROUGH THE WESTERN LAKES. WITH THE EXCEPTION OF THE EASTERN 
UP...WHERE MIXED PRECIP MAY LINGER THROUGH THE EVENT...SUFFICIENT 
WARM AIR WILL FLOW INTO THE FORECAST AREA TO PRODUCE A RAIN EVENT 
WEDNESDAY AFTERNOON AND WEDNESDAY NIGHT. DEEP/STRONG ASCENT MAY 
SUPPORT HEAVY RAIN...ESPECIALLY IF PRECIP BECOMES CONVECTIVE PER 
FORECAST ELEVATED CONVECTIVE PARAMETERS (700-500 MB LAPSE RATES 
EXCEEDING 6 C/KM AND SHOWALTER INDICES 0-2 MAY SUPPORT SOME 
THUNDER). LATEST GUIDANCE SUGGESTS 1-2 INCHES OF RAIN MAY FALL WITH 
THIS SYSTEM...AND FUTURE SHIFTS WILL NEED TO ASSESS POTENTIAL FOR 
FLOODING PROBLEMS DUE TO RAINFALL/SNOWMELT...ALTHOUGH FLASH FLOOD 
GUIDANCE IS HIGH (EXCEEDING 4 INCHES IN 6 HOURS).

AS THE LOW PASSES THE REGION...AN ARCTIC COLD FRONT WILL SWEEP 
THROUGH THE REGION...BRINGING A TRANSITION TO FRIGID 
TEMPERATURES...LAKE EFFECT SNOW SHOWERS AND GUSTY WINDS THURSDAY.  

&&

.APX...WATCHES/WARNINGS/ADVISORIES...NONE.
       

&&

$$

ROWLEY