FXUS63 KAPX 230524
AFDAPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GAYLORD MI
1219 AM EST WED DEC 23 2009

.SYNOPSIS.../ISSUED AT 314 PM/

HIGH PRESSURE WILL INFLUENCE THE GREAT LAKES THROUGH THURSDAY... 
PROVIDING THE REGION WITH DRY AIR...AND INSIGNIFICANT WEATHER. 
CLOUDS WILL INCREASE THURSDAY AND THURSDAY NIGHT...AHEAD OF AN 
APPROACHING WINTER STORM. THIS STORM WILL BRING A PERIOD OF MIXED 
WINTRY PRECIPITATION TO THE NORTH WOODS...FROM LATE CHRISTMAS EVE 
INTO CHRISTMAS DAY. SOME LIGHT SNOW WILL LINGER INTO THIS 
WEEKEND...AS THE STORM GRADUALLY WEAKENS AND EXITS THE REGION. SOME 
LAKE EFFECT SNOW IS THEN EXPECTED TO DEVELOP EARLY NEXT WEEK.

JH

&&

.SHORT TERM.../ISSUED AT 1004 PM/...TONIGHT

OVERNIGHT FORECAST CONCERNS CENTER ON NORTHERN LAKES LOW LEVEL CLOUD 
DECK AND ITS AFFECTS ON EARLY MORNING TEMPERATURE TRENDS. PER LATEST 
11U-3.9U LOW CLOUD SATELLITE IMAGERY...STRATUS DECK CONTINUES TO SAG 
SOUTH INTO THE TIP OF THE MITT...WITH RENEWED LAKE ENHANCED CLOUDS 
ACROSS NORTHERN LAKE HURON AND THE NORTHEAST LOWER COASTLINE UNDER 
REMNANT OVER-WATER INSTABILITY REGIME. MAINTENANCE OF BOUNDARY LAYER 
WEAK NORTH FLOW SHOULD ALLOW SOUTH DRIFT TO CONTINUE...ESPECIALLY AS 
MOISTURE REMAINS FIXED BELOW STRONG 900MB SUBSIDENCE INVERSION. 
THUS...WILL CONTINUE THEME INITIALLY SET FORTH BY DAY CREW... 
FEATURING INCREASING CLOUDS THROUGH THE OVERNIGHT FROM NORTH TO 
SOUTH. AS ONE WOULD EXPECT UNDER VERY LIGHT WIND REGIME AND 
SNOW-COVERED LANDSCAPE...TEMPERATURE TRENDS OVERNIGHT HIGHLY TIED TO 
AFOREMENTIONED CLOUD SHIELD. LATEST OBSERVATIONAL ANALYSIS FULLY 
SUPPORTS THE ABOVE...WITH THE WARMEST READINGS ACROSS NORTHERN 
CHIPPEWA COUNTY (WHERE CLOUDS HAVE BEEN ALL EVENING)...AND A QUICK 
DROP-OFF SOUTH OF THE MIGHTY MAC...WHERE SOME LOCALES ARE ALREADY IN 
THE SINGLE DIGITS. TEMPERATURE CURVE FOR THE REMAINDER OF THE 
OVERNIGHT WILL SIMPLY FOLLOW THE CLOUD DECK...WITH READINGS SOMEWHAT 
STABILIZING ONCE CLOUDS OVERSPREAD THE AREA. STILL...A FEW LOCATIONS 
ACROSS THE TYPICALLY COLD INTERIOR REGIONS OF NORTHERN LOWER WILL 
LIKELY MAKE A RUN AT THE ZERO MARK (PERHAPS A FEW DEGREES COLDER?) 
BEFORE THIS STABILIZATION OCCURS. TO SUM IT UP...INHERITED FORECAST 
IN EXCELLENT SHAPE WITH ONLY COSMETIC CHANGES WARRANTED ON REAL-TIME 
TEMPERATURE...CLOUD...AND DEWPOINT TRENDS.

MSB 

&&

.LONG TERM.../ISSUED AT 314 PM/...WEDNESDAY AND BEYOND

QUIET WEATHER THROUGH MIDWEEK WITH INDUCED UPPER RIDGE ACROSS THE 
GREAT LAKES...WITH ALL ATTENTION TURNING TOWARD OUR COMPLEX AND 
DIFFICULT STORM SYSTEM FOR CHRISTMAS.  WITH THIS SAID...MAIN 
FORECAST ISSUES REVOLVING AROUND POPS AND PRECIPITATION TYPE ON 
CHRISTMAS EVE AND CHRISTMAS DAY.  

WEDNESDAY AND WEDNESDAY NIGHT...QUIET WEATHER AND SEASONABLE 
TEMPERATURES AS UPPER RIDGING SLIDES ACROSS THE GREAT LAKES.  
INCREASING CLOUDS BY WEDNESDAY NIGHT AS WARMER AIR BEGINS TO MAKE A 
PUSH NORTHWARD IN ADVANCE OF DEVELOPING LOW OVER THE PLAINS.  THESE 
CLOUDS SHOULD HELP TO KEEP TEMPS WARMER THAN PREVIOUS NIGHTS...WITH 
MOST AREAS IN THE TEENS /SINGLE DIGITS COLDER LOCATIONS?/.  

THURSDAY INTO CHRISTMAS...NOW THE FUN...MODELS STILL SHOWING PLENTY 
OF DIVERGENCE IN SOLUTIONS WITH NUMEROUS DISCREPANCIES ON THE AMOUNT 
OF PHASING THAT WILL TAKE PLACE AND HOW RAPIDLY THE SYSTEM IN THE 
PLAINS DEEPENS /WHICH IMPACTS HOW QUICKLY IT MIGHT OCCLUDE AND CUT 
OFF THE WARM AIR PUSH TO THE NORTH/.  THE GFS IS THE COLDEST OF THE 
SOLUTIONS...AS IT OCCLUDES THE SYSTEM TO OUR SOUTHWEST THE 
FASTEST...THEREBY CUTTING OFF THE WARMER AIR PUSH TO THE NORTH. 
ALTHOUGH THERMALLY AN OUTLIER...THE GFS STRENGTH/POSITION DOES HAVE 
SUPPORT FROM ECMWF AND ENSEMBLES.  TO MAKE MATTERS MORE 
COMPLICATED...THE 12Z CANADIAN WANTS TO DEVELOP A SECONDARY AREA OF 
LOW PRESSURE TOWARD THE EASTERN LAKES...THEREBY KEEPING NORTHERN 
MICHIGAN COLDER AND POINTING MORE TOWARD FROZEN PCPN.  

SO WHAT TO DO?  PREFER THE CONSISTENCY OF THE ECMWF OVER THE PAST 
SEVERAL RUNS AND IT APPEARS TO HAVE A REASONABLE COMPROMISE BACKED 
UP BY THE ENSEMBLE ENVELOPE OF SOLUTIONS.  BASED ON THAT... UPPER 
FEATURE SLIDES TOWARD SOUTHERN WISCONSIN ON CHRISTMAS DAY WITH 
SURFACE FEATURE OVER NORTHERN IOWA.  AMBIENT DRY AIRMASS ACROSS 
NORTHERN MICHIGAN BEING REINFORCED SOMEWHAT BY EAST/SOUTHEAST LOW
LEVEL FLOW. SO ATMOSPHERE WILL TAKE SOME TIME TO MOISTEN UP AND
PCPN MAY NOT DEVELOP UNTIL AFTER MIDNIGHT ON THURSDAY NIGHT.
TAKING INTO ACCOUNT WET BULBING WITH AMBIENT DRY AIR...MOST LIKELY
PERIOD FOR FROZEN/FREEZING PCPN WILL BE LATE THURSDAY NIGHT INTO
CHRISTMAS MORNING. WITH SO MUCH UNCERTAINTY IN RELATIVELY SMALL
VARIATIONS IN LOW LEVEL THERMAL PROFILES...WILL NOT GET TOO
DETAILED THIS FAR OUT AND WILL GO WITH BROAD BRUSHED
RAIN/SNOW/FREEZING RAIN LIKELY. AFTER INITIAL PUSH OF WARM AIR
ADVECTION PCPN INTO CHRISTMAS MORNING... NORTHERN MICHIGAN MAY BE
"DRY SLOTTED" FOR THE MIDDAY/AFTERNOON HOURS WITH DRIZZLE AND FOG.
THE HIGHER TERRAIN AND PARTS OF EASTERN UPPER MAY STRUGGLE TO GET
MUCH ABOVE FREEZING AT THE SURFACE...AND LIGHT ICING PROBLEMS
COULD CONTINUE INTO THE AFTERNOON HOURS.

CHRISTMAS NIGHT AND BEYOND...STRONG OCCLUDED FRONT SWINGS ACROSS THE 
AREA CHRISTMAS NIGHT AND ANY LEFTOVER PCPN WILL CHANGE BACK TO LIGHT 
SNOW.  NEBULOUS FORECAST FOR THE WEEKEND WITH UPPER FEATURE BLOCKED 
FROM COMING EAST AND JUST MEANDERING AROUND THE WESTERN LAKES.  
LIMITED FORCING ACROSS OUR AREA BUT PLENTY OF MOISTURE...SO LIKELY 
SOME NUISANCE LIGHT SNOW/"SNIZZLE" TYPE PCPN ISSUES...BUT NOT 
EXPECTING MUCH IN THE WAY OF ACCUMULATION.  TEMPERATURES RETURNING 
TO BELOW NORMAL...WITH HIGHS GENERALLY IN THE 20S AND LOWS IN THE 
SINGLE DIGITS/TEENS.  LAKE EFFECT SNOWSHOWERS RETURN TO THE FORECAST 
FOR EARLY NEXT WEEK AS SEVERAL PIECES OF NORTHERN STREAM ENERGY MOVE 
ACROSS THE AREA.  

JK  

&&

.MARINE.../ISSUED AT 439 AM/

SURFACE RIDGE WILL RESULT IN A LIGHT NORTHERLY/NORTHEASTERLY FLOW
ACROSS THE UPPER LAKES THROUGH WEDNESDAY EVENING. WINDS WILL BEGIN
TO INCREASE LATER WEDNESDAY NIGHT INTO CHRISTMAS EVE OUT AHEAD OF
LOW PRESSURE APPROACHING FROM THE SOUTH.

AJS

&&

.AVIATION.../ISSUED AT 1219 AM/...VALID FOR 06Z TAFS

LIGHT AND COLD NORTHERLY WINDS ACROSS THE REGION AND GENERATING 
SHALLOW STRATO CU LAKE CLOUDS...PRIMARILY ACROSS PLN (FROM WESTERN 
CHIP/MACK COUNTIES) AND AROUND APN. DOWNSLOPING AT TVC SHOULD KEEP 
SKIES SKC...AS HIGH PRESSURE AND OVERALL EXTREMELY DRY AIR IS IN 
PLACE. HOWEVER...WILL HAVE TO DEAL WITH ROAMING STRATO CU AT BOTH 
APN/PLN OVER THE NEXT 24HRS. BELIEVE MOST OF THIS CLOUD WILL AFFECT 
APN AS WINDS WILL PREDOMINANTLY BE EASTERLY. PLN BRINGS ABOUT A 
SEPARATE ISSUE OF FREEZING FOG TOO...WILL JUST HAVE SOME MVFR VSBYS 
AFTER 08Z FOR NOW. SHALLOW STRATO CU COULD BE MORE WIDESPREAD 
TOMORROW NIGHT. SMD 

&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LM...NONE.
LH...NONE.
LS...NONE.

&&

$$