FXUS63 KAPX 261207
AFDAPX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GAYLORD MI
707 AM EST SAT DEC 26 2009
.SYNOPSIS.../ISSUED AT 232 AM/
AN AREA OF LOW PRESSURE WILL SLOWLY ROTATE EASTWARD ACROSS THE GREAT
LAKES THROUGH SUNDAY WITH COLDER AIR FILTERING BACK INTO THE REGION.
AFTER SOME EARLY MORNING FREEZING DRIZZLE TODAY...PERIODS OF LIGHT
SNOW CAN BE EXPECTED THROUGH SUNDAY. SNOW SHOWERS WILL REMAIN LIKELY
INTO EARLY NEXT WORK WEEK...AS THE LAKE EFFECT MACHINE CRANKS UP
AGAIN WITH A SECONDARY SURGE OF COLD AIR ARRIVING ON MONDAY.
&&
.SHORT TERM.../UPDATE ISSUED AT 622 AM/...TODAY
UPDATE...WEDGE OF DRIER AIR HAS FILLED IN BEHIND THE RELATIVELY
BRIEF PERIOD OF SNOW AND FREEZING DRIZZLE. SKIES MAY ACTUALLY SHOW
A LITTLE SUN THIS MORNING TOO. NEXT BATCH OF DEEPER MOISTURE AND
SNOW SHOWERS WILL ROTATE UP INTO GTV BAY REGION LATE MORNING/THIS
AFTERNOON. CHANCE/SCATTERED LIGHT SNOW SHOWERS ELSEWHERE FOR THE
BALANCE OF THE DAY. KEPT WINTER WEATHER ADVISORY GOING THROUGH
MORNING DUE TO THE PERIOD OF MIXED PRECIPITATION...AS WELL AS FOR
BELOW FREEZING TEMPERATURES AND POTENTIAL FOR BLACK ICE. FROM A
WEATHER STAND-POINT HOWEVER...NO FURTHER HAZARDOUS WEATHER IS
ANTICIPATED.
EARLIER DISCUSSION...
CURRENTLY...SPRAWLING STACKED/OCCLUDED LOW PRESSURE OVER
IOWA CONTINUES TO FILL AND WEAKEN. OCCLUDED FRONT SWINGING
NORTHWARD THROUGH THE CWA ATTM...WITH WARM WEDGE OF AIR
ALOFT/PERIODS OF RAIN NORTH OF THE FRONT. PRECIP COVERAGE NOT
SPECTACULAR AFTER DRY SLOTTING...BUT THE LOWER HALF OF THE
ATMOSPHERE IS STILL DEEP IN MOISTURE FOR CATEGORICAL RAINS TO
PERSIST...ESPECIALLY WITH HELP FROM UPPER JET DIVERGENCE/DPVA.
COOLING TEMPS ALOFT WITH SCATTERED RAIN AND SNOW SHOWERS SOUTH OF
THE OCCLUDED FRONT...WHERE MOISTURE IS LESS AND LESS...ESPECIALLY
OVER THE EASTERN CWA...FURTHER AWAY FROM DEEPER
MOISTURE/ADDITIONAL VORT MAXIMA/DPVA...WRAPPING AROUND THE UPPER
LOW.
THE OCCLUDED FRONT IS OFFERING A BURST OF SNOW...MAINLY OVER THE
HIGHER TERRAIN...BUT ACCUMULATIONS ARE LITTLE/MINOR. IT WILL TAKE A
FEW HOURS MORE FOR THE LOW LYING REGIONS TO SEE THE CHANGE TO
SNOW...SINCE THE SFC BASED WARM LAYER NEEDS TO COOL OFF AS WELL
(STILL AS MUCH AS 3KFT THICK NEAR THE COASTS).
THROUGH DAYBREAK...BACK EDGE OF BETTER PRECIP COVERAGE/ALONG AND
NORTH OF OCCLUDED FRONT/IN STRONGEST...YET MODEST OVERALL H7-H5
-DIVQ...LIFTS INTO EASTERN UPPER...KEEPING CATEGORICAL RAINS THERE.
SFC BASED WARM LAYER OUGHT TO BE COLD ENOUGH PRIOR TO ONSET OF NEXT
BATCH OF SHOWERS/DEEPER MOISTURE/DPVA PINWHEELING UP ACROSS THE GTV
BAY REGION AT 12Z. WILL GO WITH SOME SCATTERED SNOW SHOWERS
THERE...BUT WE HAVE ICE INTRODUCTION ISSUES WITH MOISTURE DIPPING
BELOW THE -10C ISOTHERM BEHIND THIS SNOW SHOWER ACTION. UPSTREAM OBS
SUPPORT FREEZING DRIZZLE...SO WILL HAVE TO HAVE THIS MENTION AS
WELL. ISOLATED TO NO ACTION BETWEEN THE TWO AREAS OF PRECIP...MAYBE
JUST SOME CHANCE OF FREEZING DRIZZLE...AS MOISTURE NEVER LOOKS TO BE
DEEP ENOUGH FOR ANYTHING OTHER THAN DRIZZLE. HAVE ALREADY ISSUED
THE WINTER WEATHER ADVISORY FOR THE SNOW/FREEZING DRIZZLE. TO ADD
TO ICE ISSUES...WET ROADS/TEMPS DROPPING TO BELOW FREEZING WILL
RESULT IN SOME BLACK ICE POTENTIAL AS WELL. ADVISORY A GOOD IDEA.
THROUGH THE DAY...AREAS OF FREEZING DRIZZLE WILL PERSIST INTO THE
MORNING...THEN...DEEPER MOISTURE/DPVA SPREADS IN ACROSS THE
ENTIRE CWA...AS UPPER/SFC LOWS DRAW NEARER. INCREASING BROAD LOW
LEVEL CONVERGENCE WILL AT LEAST ALLOW FOR SCATTERED ACTIVITY.
HOWEVER THE BEST COVERAGE WILL STILL BE CONFINED ACROSS THE GTV
BAY REGION WHERE COLDER POOL ALOFT AND DIURNAL PROCESSES WILL LEAD
TO MORE NUMEROUS SHOWERS. FINALLY...AS IF THERE ISN'T ENOUGH
ALREADY...BUT AS H8 TEMPS COOL TO -10C TO -12C...GOTTA START
LOOKING AT POTENTIAL LAKE ENHANCEMENT. MARGINAL OVERLAKE
INSTABILITY...WEAK 10KT 1000-850MB FLOW AND POOR TRAJECTORIES
(SOUTH/SSE) DO NOT PROVIDE MUCH IN THE WAY OF LAKE ASSISTANCE.
HAVE TO WATCH FAR WESTERN AND FAR EASTERN AREAS OF CHIP/MACK
COUNTIES OF EASTERN UPPER...BUT STILL FEEL THAT OVERALL
ENHANCEMENT IN NEGLIGIBLE.
EARLY MORNING TEMPERATURES IN THE MIDDLE TO UPPER 30S...WILL BE
FALLING OFF INTO THE UPPER 20S BEHIND THE FRONT. TEMPERATURES LIKELY
WILL NOT DO MUCH THROUGH THE DAY...HOLDING IN THE UPPER 20S TO
AROUND 30 DEGREES FOR COMMON READINGS THROUGHOUT THE DAY. SMD
&&
.LONG TERM.../ISSUED AT 408 AM/...TONIGHT AND BEYOND
TONIGHT...DEEPER MOISTURE/COLDER AIR/SFC LOW AND DPVA FROM
PINWHEELING VORTICITY MAXIMA...ALL LIFT UP ACROSS THE NORTH WOODS
TONIGHT TO BRING A PERIOD OF SNOW TO ALL LOCATIONS. NO SIGNIFICANT
ACCUMULATIONS EXPECTED ATTM...BUT MAYBE UP TO 2 INCHES CAN FALL
ACROSS BEST LOW LEVEL CONVERGENCE THAT LIES FROM MANISTEE TO
DRUMMOND ISLAND. CLOUDS WITH MINIMAL THERMAL ADVECTIONS TO KEEP
TEMPERATURES IN THE 20S.
SUNDAY...LINGERING LOW LEVEL CONVERGENCE AND DEEPER MOISTURE ACROSS
THE NW CWA...WHILE A DEVELOPING NW FLOW WILL ACTUALLY SERVE TO WARM
THE LOW LEVELS UP (H8 TO -8C...POTENTIAL ICE INTRODUCTION ISSUES
LATER IN THE DAY?). WILL KEEP ONGOING IDEA OF LIKELY CHANCES FOR
SNOW IN THE NW CWA...WHILE MORE SCATTERED ACTIVITY LIKELY DEVELOPS
ACROSS THE SE HALF OF THE CWA...WHERE COLD 700MB POCKET OF AIR
BRINGS ON A PERIOD OF STEEPER LOW LEVEL LAPSE RATES.
SUNDAY NIGHT INTO MONDAY...UPPER LOW SHIFTS EASTWARD...WHILE A NRN
STREAM SHORTWAVE DIVES ACROSS ONTARIO AND ACTUALLY SERVES TO SHARPEN
UP THE LOW LEVEL TROUGHING THROUGH MONDAY MORNING. 1000-850MB WINDS
WILL BE ON THE RISE (30KTS)...WHILE THE CYCLONIC CONVERGENCE IS
RATHER IMPRESSIVE ATTM...TAPPING INTO LAKE SUPERIOR QUITE WELL. H8
TEMPS ARE RIGHT AT -8C WHILE THE DEEPEST MOISTURE AND CONVERGENCE
ARE HERE. AS THE BETTER THERMAL PROFILES FOR LES ARRIVE LATER
MONDAY...WE UNDERGO SUBSTANTIAL DRYING. FOR THE SNOW LOVERS...WE
JUST CANNOT SEEM TO GET OUR SNOW ACT GOING. LES WILL BE LIKELY
DURING THIS TIME PERIOD.
LATER PERIODS...NO CHANGES. SMD
&&
.MARINE.../ISSUED AT 232 AM/
STRONG EASTERLY FLOW AHEAD OF NORTHWARD ADVANCING OCCLUDED FRONT
WILL CONTINUE TO BRING GALES TO MUCH OF THE LAKE HURON NEARSHORE
WATERS...FAR NRN LAKE MICHIGAN AND WHITEFISH BAY NEARSHORES AND
SAINT MARY'S RIVER SYSTEM. THIS LIKELY TO ONLY PERSIST THROUGH 5AM
OR SO...AS A MUCH LIGHTER WIND FIELD DEVELOPS OUT OF THE SOUTH.
THUS...PLAN ON DROPPING GALE WARNINGS AT 5AM ISSUANCE. WILL NEED
SOME SMALL CRAFT ADVISORIES FOR A TIME THIS MORNING DUE TO WAVE
ACTION AND DECAYING GUSTINESS. A LIGHT SOUTHERLY FLOW IS EXPECTED TO
SLOWLY TURN WESTERLY SUNDAY NIGHT. WINDS INCREASE OUT OF THE
NORTHWEST MONDAY...AS A STRONG COLD FRONT BLASTS THROUGH THE GREAT
LAKES. NEW HEADLINES (SMALL CRAFTS) ARE LIKELY. SMD
&&
.AVIATION.../ISSUED AT 703 AM/...VALID FOR 12Z TAFS
WEDGE OF DRY AIR IS WORKING IN OVER THE TAF SITES 12-14Z AND MAY
BRING A BRIEF PERIOD OF SUNSHINE THIS MORNING...BEFORE A BKN VFR
CIG REDEVELOPS LATER THIS MORNING. OVC MVFR CIGS RETURN LATE THIS
AFTERNOON AT TVC...AND THIS EVENING AT PLN AND APN WITH THE
ARRIVAL OF NEXT BATCH OF DEEPER MOISTURE AND SNOW SHOWERS. LIGHT
SOUTHERLY WINDS THROUGH THE TAF PERIOD. SMD
&&
.APX WATCHES/WARNINGS/ADVISORIES...
MI...WINTER WEATHER ADVISORY UNTIL 11 AM EST THIS MORNING FOR
MIZ019>023-025>029-031>035-041.
LM...SMALL CRAFT ADVISORY UNTIL 11 AM EST THIS MORNING FOR LMZ341.
LH...SMALL CRAFT ADVISORY UNTIL 5 PM EST THIS AFTERNOON FOR
LHZ345>349.
LS...SMALL CRAFT ADVISORY UNTIL 11 AM EST THIS MORNING FOR LSZ321-322.
&&
$$
