000
FXUS63 KAPX 070450
AFDAPX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GAYLORD MI
1150 PM EST TUE JAN 6 2009
.SYNOPSIS.../ISSUED AT 338 PM/
LOW PRESSURE ACROSS THE PLAINS WILL ORGANIZE AND STRENGTHEN
TONIGHT...THEN GRADUALLY WORK THROUGH LOWER MICHIGAN ON WEDNESDAY.
AS THIS OCCURS...SNOW WILL SPREAD INTO NORTHERN MICHIGAN LATE
TONIGHT AND CONTINUE INTO WEDNESDAY EVENING...WITH RELATIVELY LIGHT
SNOW ACCUMULATIONS EXPECTED.
SNOWFALL WILL DIMINISH AND TRANSITION TO LAKE EFFECT SNOW SHOWERS
ACROSS THE SNOWBELTS TO WRAP UP THE WORK WEEK. JUST IN TIME FOR AN
ALBERTA CLIPPER SYSTEM TO SLIDE THROUGH EARLY IN THE WEEKEND...
YIELDING THE POTENTIAL FOR MORE ACCUMULATING SNOW.
ADAM
&&
.SHORT TERM.../ISSUED AT 938 PM/...TONIGHT
AREA IS GETTING SQUEEZED BY DISTURBANCES APPROACHING FROM THE SW AND
NW. SURFACE SYSTEM STILL GETTING IT/S ACT TOGETHER...WITH A 999MB
PRESSURE MIN NEAR CINCY...AND ANOTHER NEAR THE TWIN CITIES...
EMBEDDED WITHIN A MUCH BROADER. NO PRECIP HERE YET...THOUGH MID
RETURNS ARE BLOSSOMING AS THE UPPER DISTURBANCES GO TO WORK.
LOW PRESSURE WILL BECOME BETTER ORGANIZED TONIGHT...WITH A CIRCA
992MB LOW CENTERED NEAR DETROIT AT DAWN. THE BEST DYNAMICS AND
PRECIP WITH THIS EVENT WILL STAY TO OUR EAST...ACROSS THE UPPER OHIO
VALLEY AND EASTERN GREAT LAKES. FORCING FOR ASCENT LOOKS SOMEWHAT
UNIMPRESSIVE THIS FAR WEST...ESPECIALLY GIVEN THE NORMAL HIGH-IMPACT
NATURE OF PHASING SYSTEMS.
WE ARE STILL VERY MUCH ON TARGET FOR LOW LEVEL DRY AIR TO BE
OVERCOME OVERNIGHT...AS LIFT ALOFT BECOMES SOMEWHAT STRONGER. THE SW
ZONES WILL PROBABLY BE THE 1ST TO SEE PRECIP (TOWARD
MIDNIGHT)...EXPANDING NORTHWARD WITH TIME. WILL BACK OFF A BIT ON
POPS/SNOW NORTH OF THE BRIDGE...SNOW MAY NOT ARRIVE THERE UNTIL
ALMOST DAWN.
THE 18Z NAM GAVE A BIT OF A DANGER SIGNAL...BRINGING IN SOME EXTRA
QPF INTO PARTS OF N CENTRAL AND NE LOWER MI LATE TONIGHT. THE 00Z
RUN CONTINUES THAT TREND...BUT REALLY FOCUSING ON LAKE ENHANCEMENT
POTENTIAL. MID-LAKE SURFACE TEMPS ARE STILL RUNNING ABOUT 3C ON
HURON. WITH 850MB TEMPS RUNNING AROUND -10C DURING THE /HEIGHT/ OF
THE EVENT (12Z-15Z) AS WINDS BACK FROM E TO NE...THERE IS AT LEAST
DECENT POTENTIAL FOR THE LAKE TO ASSIST. THE NAM SOUNDINGS ACTUALLY
LOOK QUITE FAVORABLE...WITH HIGH INVERSION HEIGHTS FOR A LAKE-
ENHANCED EVENT (4-5K FT)...AND A DEEP ISOTHERMAL LAYER FROM -10C TO
-12C ON TOP OF THAT (WOULD BE MORE FAVORABLE IF THAT WAS A BIT
COLDER).
WITH THAT IN MIND...AM GOING TO INCREASE TOTAL SNOW AMOUNTS IN THE
ROGERS CITY/APN/ATLANTA AREAS TO 3 TO 5 INCHES...AND HOIST AN
ADVISORY FOR THOSE 3 COUNTIES. FOR THE REST OF THE REGION...THE
GOING FORECAST LOOKS PRETTY REASONABLE.
JZ
&&
.LONG TERM.../ISSUED AT 338 PM/...WEDNESDAY AND BEYOND
ENERGETIC WEATHER REGIME SET TO KICK IT UP A NOTCH AS VERY STRONG...
EXTENDED EAST ASIAN JET GETS READY TO KICK THE AMPLIFICATION PROCESS
INTO HIGH GEAR...WITH BURGEONING EAST PACIFIC RIDGING AND SUBSEQUENT
DEVELOPMENT OF EASTERN NOAM TROUGHING. EXACT AXES OF ABOVE MID AND
UPPER LEVEL FEATURES YET TO BE IRONED OUT...BUT ALL SIGNS POINTING
TOWARDS STEP DOWN COOLING PROCESS (LIKE ITS NOT ALREADY COLD ENOUGH
:))...WITH DEFINITE POTENTIAL FOR POLAR EXPRESS VISIT JUST OUTSIDE
OF THIS FORECAST PACKAGE AS EXCEEDINGLY COLD ALASKA/NORTHWEST
TERRITORIES AIRMASS (JUST TAKE A GANDER AT THE FAIRBANKS ALASKA
OBSERVATIONS/FORECAST... WOW! HINT...TODAYS HIGHS UP THERE A SULTRY
35 TO 50 BELOW ZERO!) IS FORCED ON A SOUTHWARD JOURNEY IN RESPONSE
TO BUILDING GULF OF ALASKA HEIGHTS. ANYWAY...FOCUSING MORE ON THE
NEAR TERM...EXTENDED FORECAST LOOKS TO START OUT ON A SNOWY NOTE AS
WELL ADVERTISED CONGLOMERATE OF SYSTEMS OVERSPREADS THE AREA
WEDNESDAY...WITH THE REST OF THE EXTENDED DOMINATED BY LAKE EFFECT
CONCERNS AND CLIPPER SYSTEMS AS AFOREMENTIONED PATTERN
RECONFIGURATION BEGINS.
WEDNESDAY...AH...WHAT COULD HAVE BEEN. ALTHOUGH HAVE BEEN AWAY FROM
THE FORECAST DESK FOR THE LAST 5 DAYS...COULD SEE THE POTENTIAL FOR
WEDNESDAYS SYSTEM...WITH A VIGOROUS SHORTWAVE EJECTING INTO THE
SOUTH CENTRAL PLAINS AS ADDITIONAL ENERGY DROPS SOUTHEAST OUT OF
CANADA. UNFORTUNATELY (FORTUNATELY)...PHASING OF THESE STREAMS
EXPECTED TO OCCUR JUST A LITTLE TOO LATE...WITH BOMBOGENESIS TAKING
PLACE OF THE NEW ENGLAND COASTLINE WEDNESDAY NIGHT. ALTHOUGH BEST
MOISTURE FLUX REMAINS TIED TO EJECTING SOUTHERN STREAM WAVE...STILL
ENOUGH MOISTURE WRAPPING BACK IN DEVELOPING... EXTENDED LOW AND MID
LEVEL TROWAL AXIS OVER THE NORTHERN LAKES TO RESULT IN A RATHER
PROLONGED PERIOD OF STEADY LIGHT SNOW. GIVEN STEADY-STATE MIXING
RATIOS OF 2 TO 3 G/KG ON THE 280K-290K ISENTROPIC SURFACES AND
PROLONGED NATURE OF THE EVENT...INHERITED GRIDS FEATURING A GENERAL
1 TO 3 INCHES OF ADDITIONAL SNOW WEDNESDAY LOOKS IDEAL. AS FOR THE
LAKE HURON ENHANCEMENT POTENTIAL...NOT LOOKING LIKE A BIG DEAL WITH
VERY MARGINAL OVER-WATER INSTABILITY (DELTA T/S SUB 13C) AND MORE
IMPORTANTLY...A RAPIDLY BACKING LOW LEVEL WIND FIELD...WITH EAST
WINDS IN THE MORNING BECOMING NORTHERLY BY EVENING.
WEDNESDAY NIGHT THROUGH THURSDAY NIGHT...TROWAL AXIS PIVOTS SOUTH
DURING THE EVENING...WITH SYNOPTIC SCALE LIGHT SNOWFALL FOLLOWING
SUITE. ATTENTION...OF COURSE...TURNS TO N/NW FLOW LAKE EFFECT AS
REMNANT MOISTURE FIELD PIVOTS OVER THE LAKES. WHILE OVER-WATER
INSTABILITY IS NOT GREAT...GENERALLY IN THE LOWER TEENS...DEEP LAYER
MOISTURE FIELD SHOULD HELP COMPENSATE SOME...SO THINKING ANOTHER 2
TO 3 INCHES OF SNOW ALONG WEST OF THE US-131 CORRIDOR NOT OUT OF THE
QUESTION. FLOW LOOKS A LITTLE TOO NORTHERLY TO HAVE MUCH IMPACT
ACROSS EASTERN UPPER. FLOW STEADILY BACKS AROUND MORE NORTHWESTERLY
ON THURSDAY...TARGETING THE TRADITIONAL SNOWBELTS OF NORTHWEST LOWER
AND EASTERN UPPER MICHIGAN. ONCE AGAIN...ANOTHER COUPLE INCHES OF
ACCUMULATION IS EASILY ASCERTAINABLE IN FAVORED AREAS WITH INVERSION
LEVELS UP NEAR 800MB AND DECENT MOISTURE PROFILES THROUGH 700MB.
STEADILY BACKING FLOW...WAA PROCESSES...AND LOWERING INVERSION
HEIGHTS AHEAD OF APPROACHING CLIPPER SYSTEM SHOULD BRING A STEADY
DEMISE TO LINGERING LAKE SNOWS THURSDAY NIGHT.
FRIDAY AND FRIDAY NIGHT...UNFORTUNATELY...MORE QUESTIONS THAN
ANSWERS REGARDING POTENTIAL CLIPPER SYSTEM FRIDAY AFTERNOON AND
NIGHT AS GUIDANCE STRUGGLES WITH "SPLITTING" OF ELONGATED SHORTWAVE
TROUGH AXIS AS IT PUSHES ACROSS THE INTERMOUNTAIN WEST. VARIOUS
MODELS ALL OVER THE PLACE IN MAGNITUDE AND PLACEMENT OF NORTHERN
ENERGY...WITH THE 12Z GFS MOST AGGRESSIVE IN THIS REGARD...SWEEPING
IT AND A PRETTY IMPRESSIVE SURFACE RESPONSE ACROSS THE NORTHERN
LAKES FRIDAY NIGHT. ON THE OTHER HAND...LATEST UKMET AND ECMWF
MAINTAINING TRENDS FIRST OBSERVED LAST NIGHT...WITH MUCH WEAKER
NORTHERN STREAM ENERGY AND A MUCH FARTHER SOUTH LOW PLACEMENT. IN
FACT...LATEST ECMWF WOULD SUGGEST MUCH OF THE MEASURABLE
PRECIPITATION REMAINING SOUTH OF THE AREA...TARGETING SOUTHERN LOWER
MICHIGAN. IN LIGHT OF THE UNCERTAINTIES (REALITY PROBABLY SOMEWHERE
IN-BETWEEN)...FELT MAKING CHANGES FOR THIS PERIOD UNJUSTIFIED...
FEATURING CHANCE POPS FRIDAY AND MAINTAINING LIKELY WORDING FRIDAY
NIGHT.
REST OF THE FORECAST (THIS WEEKEND INTO EARLY NEXT WEEK)...AS
MENTIONED...POSITIVE PNA CONFIGURATION CONTINUES TO DEVELOP THIS
WEEKEND...EVENTUALLY CARVING OUT A RATHER DEEP GREAT LAKES TROUGH
AXIS DURING EARLY/MID NEXT WEEK. WHILE NOT A PATTERN CONDUCIVE TO A
LARGE SYNOPTIC SNOWSTORM WITH THE GULF ESSENTIALLY CLOSED FOR
BUSINESS IN SUCH A FLOW...THE PATTERN IS AN ACTIVE ONE FOR "ALBERTA
CLIPPER" TYPE SYSTEMS...FOLLOWED BY SHOTS OF LAKE EFFECT SNOWS. HAVE
ESSENTIALLY USED CHANCE POPS...HIGHEST IN CLIMATOLOGICALLY FAVORED
LAKE EFFECT ZONES...THROUGH THIS PERIOD TO ACCOUNT FOR THE INHERENT
TIMING DIFFICULTIES OF SUCH CLIPPER SYSTEMS. LATEST GUIDANCE
CONTINUES TO SHOW MUCH COLDER WEATHER ON TAP FOR THE MIDDLE AND END
OF NEXT WEEK AS FLOW EMANATING FROM THE POLAR REGIONS DROPS 850MB
TEMPERATURES SUB -24C.
MSB
&&
.MARINE.../ISSUED AT 338 PM/
SFC LOW PRESSURE EXPECTED TO DEEPER AND SLOWLY SLIDE ACROSS LOWER
MICHIGAN ON WEDNESDAY. BUT NO MARINE HEADLINES EXPECTED THROUGH THE
DAY WEDNESDAY AS OVERALL GRADIENT REMAINS RATHER LIGHT AND WIND
SPEEDS GENERALLY UNDER 15 KNOTS. HOWEVER...AS THIS SYSTEM DEPARTS
WEDNESDAY NIGHT...A TIGHTER PRESSURE GRADIENT MAY BRING THE RETURN
TO SMALL CRAFT GUST AND/OR WAVES LATE WED NIGHT INTO THURS.
ADAM
&&
.AVIATION.../ISSUED AT 1150 PM/...VALID FOR 06Z TAFS
SNOW WILL DEVELOP AT ALL TAF SITES OVER THE NEXT FEW HOURS...AS LOW
PRESSURE SLOWLY ORGANIZES TO OUR SOUTH. THE LOW WILL MOVE NE AWAY
FROM THE DETROIT AREA DURING THE DAY ON WEDNESDAY. IFR VSBYS WILL
PREVAIL...WITH THE WORST CONDITIONS AT APN. IMPROVEMENT TO MVFR IS
EXPECTED AT TVC/PLN AROUND MIDDAY...AND TOWARD EVENING AT APN. LAKE
EFFECT SNOW SHOWERS WILL IMPACT TVC WEDNESDAY EVENING AS WINDS BACK
TO THE NNW.
JZ
&&
.APX WATCHES/WARNINGS/ADVISORIES...
MI...WINTER WEATHER ADVISORY FROM 2 AM TO 5 PM WEDNESDAY FOR
MIZ018-023-024.
LM...NONE.
LH...NONE.
LS...NONE.
&&
$$
