FXUS63 KAPX 231751
AFDAPX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GAYLORD MI
150 PM EST WED DEC 23 2009
.SYNOPSIS.../ISSUED AT 417 AM/
HIGH PRESSURE WILL MAINTAIN ITS INFLUENCE OVER THE GREAT LAKES
THROUGH THURSDAY...PROVIDING DRY AIR AND QUIET WEATHER. CLOUDS WILL
INCREASE THURSDAY AND THURSDAY NIGHT...AHEAD OF AN APPROACHING
WINTER STORM. THIS STORM WILL BRING A MIXTURE OF WINTRY
PRECIPITATION TO THE NORTH WOODS FROM LATE CHRISTMAS EVE INTO
CHRISTMAS DAY. SOME PERIODS OF LIGHT SNOW WILL CONTINUE THROUGH THE
WEEKEND...WITH LAKE EFFECT SNOW DEVELOPING BEHIND THIS SYSTEM EARLY
NEXT WEEK.
SMD
&&
.SHORT TERM.../ISSUED AT 1005 AM/...THIS AFTERNOON
GOING FCST LOOKS TO BE IN GOOD SHAPE...WITH ONLY MINOR TWEAKS MADE.
SPECIFICALLY...FCST ISSUE OF THE DAY IS CLOUD COVER AND TEMPS. AS
ANTICIPATED THE PAST FEW SHIFTS...LOW STRATUS DECK DID INDEED MAKE A
RUN AT NORTHERN MICHIGAN OVERNIGHT...EVEN OVERACHIEVING ACRS THE
SOUTH/WEST WITH CLOUDS SPREADING ALL THE BACK TOWARD FLINT AND BACK
TO THE LAKE MICHIGAN COAST...MOST CERTAINLY AUGMENTED BY SHALLOW
OVERLAKE INSTABILITY (900MB TEMPS RUNNING -11C PER 12Z APX RAOB).
EVEN A FEW FLURRIES NOTED FROM THE DECK GIVEN CLOUD TOP TEMPS JUST
SUFFICIENT FOR ICE PRODUCTION (-11C)...THOUGH THESE ABOUT HISTORY
WITH DRIER AIR BLEEDING INTO THE AREA ON MEAN NORTHEAST BOUNDARY
LAYER FLOW. SPEAKING OF DRY AIR...SATELLITE TRENDS LEND CREDENCE TO
SHORT TERM GUIDANCE TREND OF GRADUALLY ERODING LOW CLOUD DECK INTO
THE AFTN...THOUGH THIS WILL SURELY BE A SLOW PROCESS GIVEN RATHER
STOUT INVERSION AND WEAK LATE DECEMBER SUN. AREAS MOST LIKELY TO
BREAK UP FIRST INCLUDE EASTERN UPR WHERE CLOUDS QUICKLY ERODING
ALREADY...AND THE LAKE MICHIGAN COASTAL AREAS ON DOWNSLOPE FLOW.
HIGHER TERRAIN LIKELY THE LAST AREA TO SEE SUN...BUT SHOULD SEE SOME
PEAKS INTO THE AFTN...THOUGH ALSO WATCHING SOME INCREASE IN CIRRUS
THRU THE DAY. GOING HIGH TEMPS LOOK GOOD THOUGH WILL RAISE A DEGREE
OR TWO WHERE SUN ALREADY PEAKING THROUGH.
LAWRENCE
&&
.LONG TERM.../ISSUED AT 417 AM/...TONIGHT AND BEYOND
RIDGING WILL GIVE WAY TO SOUTHERN STREAM ENERGY TO OUR SOUTHWEST
COLLIDING WITH NORTHERN STREAM ENERGY CHRISTMAS DAY. THE MAIN
CHALLENGE CONTINUES TO BE THE DETAILS OF THE STORM SYSTEM MOVING UP
FROM THE SOUTH.
TONIGHT INTO THURSDAY...RIDGING AT THE SURFACE AND ALOFT WILL
CONTINUE TO RESULT IN PRECIPITATION FREE CONDITIONS. LIKELY WILL SEE
MORE STRATUS FORMATION OFF OF LAKE HURON AFTER MIDNIGHT AS EASTERLY
FLOW INCREASES. IN ADDITION...MID/HIGH CLOUDS WILL INCREASE LATER
TONIGHT WITH LOTS OF CLOUDS EXPECTED FOR THURSDAY. EASTERLY FLOW
PICKS UP TONIGHT AND THIS IN COMBINATION WITH CLOUD COVER SHOULD
KEEP TEMPERATURES FROM DROPPING OFF THE TABLE LIKE THE LAST COUPLE
OF NIGHTS. FORECAST LOWS WILL BE IN THE TEENS TO LOWER 20S. HIGHS
THURSDAY GENERALLY IN THE UPPER 20S AND LOWER 30S.
THURSDAY NIGHT INTO FRIDAY...EXTENDED MODELS HAVE COME INTO BETTER
(BUT STILL FAIR) AGREEMENT IN THAT SOUTHERN STREAM ENERGY (CURRENTLY
ACROSS THE SOUTHERN ROCKIES) PHASES WITH NORTHERN STREAM ENERGY
(CURRENTLY ACROSS ALBERTA) OVER THE CENTRAL PLAINS ON CHRISTMAS DAY.
BEFORE THIS OCCURS...AN INITIAL WARM SURGE OF AIR AT MID LEVELS (850
MB TEMPS IN THE PLUS 3 TO PLUS 5 RANGE) IS SHOWN TO WORK ITS WAY
INTO NORTHERN MICHIGAN BEFORE THE NORTHERN STREAM ENERGY WIPES OUT
THE WARM LAYER. MOISTURE STREAKS OUT AHEAD OF THE SYSTEM BUT AN
EXTREMELY DRY EASTERLY FLOW WILL MAKE PRECIPITATION PRODUCTION
TOUGH FOR THURSDAY NIGHT WITH MODEL SOUNDINGS INDICATING MASSIVE
AMOUNTS OF EVAPORATIVE COOLING. THE QUESTION IS WHETHER OR NOT
THE EVAPORATIVE COOLING WILL BE SUFFICIENT TO OVERCOME THE WARM
LAYER RESULTING IN AN ALL SNOW EVENT. RIGHT NOW IT REMAINS TOO
CLOSE TO CALL BUT WITH THE GROUND HAVING BEEN BELOW FREEZING FOR
SEVERAL DAYS...ANY RAINFALL WOULD LIKELY FREEZE ON CONTACT (MAKING
FOR VERY SLIPPERY BACK ROADS AT A MINIMUM). AM NOT EXPECTING ENOUGH
QPF TO REACH WARNING CRITERIA FOR EITHER SNOWFALL OR ICE
ACCUMULATION SO WILL NOT ISSUE A WATCH AT THIS TIME. BELIEVE THAT
ANY RAIN OR FREEZING RAIN TO START (LATE THURSDAY NIGHT INTO EARLY
FRIDAY) WILL TRANSITION OVER TO A PERIOD OF MODERATE SNOW BY
FRIDAY AFTERNOON DUE TO THE COMBINATION OF THE EVAPORATIVE COOLING
AND COLD AIR ADVECTION FROM THE SOUTH AS THE UPPER LOW TRACKS
CLOSER TO THE AREA. THERE APPEARS TO BE POTENTIAL FOR A FEW
INCHES OF SNOWFALL ACCUMULATION. AT THIS POINT WOULD THINK THAT A
WINTER WEATHER ADVISORY WOULD MOST LIKELY HANDLE THE MIXED
PRECIPITATION FORECAST EVENT...BUT THIS OF COURSE COULD CHANGE.
TEMPERATURES THURSDAY NIGHT ONLY DROPPING OFF INTO THE MIDDLE 20S
TO AROUND 30 WITH HIGHS CHRISTMAS DAY IN THE LOWER AND MIDDLE 30S.
FRIDAY NIGHT THROUGH SUNDAY...CUTOFF UPPER LOW CRAWLS ACROSS THE
REGION AS THE SURFACE LOW SLOWLY FILLS. MODEL SOUNDINGS/CROSS
SECTIONS INDICATE THAT MOISTURE WILL REMAIN ABUNDANT BUT FORCING IS
SHOWN TO BE RATHER WEAK SO AM EXPECTING PERIODS OF MAINLY LIGHT
SNOW. HIGHS GENERALLY RANGING FROM THE MIDDLE 20S TO LOWER 30S WITH
LOWS IN THE UPPER TEENS AND 20S.
SULLIVAN
&&
.MARINE.../ISSUED AT 417 AM/
SURFACE RIDGE WILL RESULT IN A LIGHT NORTHEASTERLY FLOW ACROSS THE
UPPER LAKES THROUGH THIS EVENING. EASTERLY WINDS WILL BEGIN TO
INCREASE LATER TONIGHT INTO CHRISTMAS EVE OUT AHEAD OF LOW PRESSURE
APPROACHING FROM THE SOUTH. AT A MINIMUM...SMALL CRAFT ADVISORIES
WILL BE NEEDED THURSDAY NIGHT WITH THE POSSIBILITY OF GALES THURSDAY
NIGHT INTO CHRISTMAS DAY.
AJS
&&
.AVIATION.../ISSUED AT 150 PM/...VALID FOR 18Z TAFS
FCST IS LARGELY CONTINUITY WITH 12Z TAFS.
THIS AFTN: MVFR STRATOCU GRADUALLY MIXING OUT TO SCT. IMPROVEMENT TO
VFR EXPECTED SHORTLY AT TVC. 25K FT CIRRUS WILL OVERSPREAD THE
TERMINALS IN LIGHT N-E BOUNDARY LAYER (BL) FLOW.
TONIGHT: VFR TO START THEN MVFR STRATOCU EXPECTED TO MOVE BACK IN FM
E TO W. CIRRUS CIGS GRADUALLY YIELD TO MULTI-LAYERED MID LEVEL
ALTOCU/ALTOST ABOVE LOW-LEVEL LAKE CLDS. LIGHT E BL FLOW.
THU THRU 18Z: DIURNAL MIXING AND DOWNSLOPE FLOW AT SHOULD ERODE MVFR
STRATOCU AT PLN/TVC...REVEALING MULTI-LAYERED 8-12K FT MID-LEVEL
OVC. E BL FLOW WILL BEGIN INCREASING.
JH/JPB
&&
.APX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LM...NONE.
LH...NONE.
LS...NONE.
&&
$$
