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AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
505 AM EST SUN DEC 28 2014


.AVIATION...

HIGH PRESSURE BUILDING INTO THE REGION WILL RESULT IN CLEARING SKIES 
THROUGH THE AFTERNOON AND LIGHT NORTHWESTERLY FLOW. CLOUDS WILL 
START OFF TODAY WITH SOME LINGERING MVFR CIGS BUT DRY AIR WILL BRING 
VFR CONDITIONS TO ALL TERMINALS THIS AFTERNOON AND INTO THE 
OVERNIGHT. A COLD FRONT DROPPING IN FROM THE NORTH WILL INTRODUCE 
SOME MID CLOUDS LATE TONIGHT. 

FOR DTW...ONLY ISSUE IN THE NEAR TERM IS THE POCKETS OF MVFR CIGS IN 
THE AREA HOVERING AROUND THE 2000FT THRESHOLD. THEY SHOULD NOT LAST 
LONG INTO THE DAYLIGHT HOURS BEFORE LIFTING TO VFR.

//DTW THRESHOLD PROBABILITIES...

* HIGH FOR CEILING BELOW 5000 FEET THROUGH ABOUT 16Z...AND 
  MEDIUM AFTER 12Z MONDAY.

&&

.PREV DISCUSSION...ISSUED 358 AM EST SUN DEC 28 2014 

SHORT TERM...TODAY AND TONIGHT

THE STORY FOR THE SHORT TERM IS THE INFLUX OF COLD AIR RESULTANT OF 
A PAIR OF COLD FRONTS PASSING THROUGH LOWER MI. THE FIRST FRONT 
PASSED THROUGH SE MI BETWEEN 00-04Z EARLY SATURDAY NIGHT. 
TEMPERATURES ALOFT HAVE ALREADY BEEN TRENDING DOWN WITH THE WARM 
BUBBLE AT 700MB DROPPING FROM ABOUT 3C 00Z SATURDAY TO -3C SUNDAY 
00Z AND FORECAST TO BE DOWN TO -10C BY 12Z SUNDAY. CAA WILL STEADY 
ITSELF THROUGH THE DAY BEFORE A BACK DOOR COLD FRONT PASSES THROUGH 
TONIGHT BRINGING ANOTHER SURGE OF COLD AIR INTO THE AREA. BESIDES 
DECREASING TEMPERATURES...THE AIRMASS WILL BE MUCH DRIER WITH LITTLE 
MOISTURE ABOVE 850MB UNTIL THE BACK DOOR COLD FRONT BRINGS IN SOME 
MID LEVEL MOISTURE. THE DRY AIR SHOULD BE ABLE TO SCATTER OUT THE 
LOW STRATUS DECK ALLOWING A GOOD DEAL OF SUNSHINE LATER THIS 
AFTERNOON...ESPECIALLY FOR SOUTHERN LOCATIONS FURTHER AWAY FROM THE 
APPROACHING BACKDOOR COLD FRONT. THIS WILL OFFSET SOME DEGREE OF 
COOLING BUT NOT ENOUGH TO ALLOW TEMPS TO CLIMB OUT OF THE MID 30S. 
SOME RETURNS ON RADAR EARLY THIS MORNING ARE AMOUNTING TO NOTHING 
MORE THAT A LOW STRATUS DECK OVER THE AREA. SOME LAKE ENHANCED SNOW 
SHOWERS DRIFTING ACROSS WESTERN LOWER WILL TAKE A RUN AT OUR WESTERN 
COUNTIES BUT WITH THE SHALLOW NATURE OF THE MOISTURE AND THE DRY AIR 
IT HAS TO WORK ACROSS...WILL KEEP THE FORECAST DRY. WITH MOSTLY 
CLEAR SKIES TAKING US INTO THE OVERNIGHT...RADIATIONAL COOLING WILL 
ALLOW US TO DROP INTO THE 20S BEFORE CLOUDS START FILLING BACK IN.

LONG TERM... MONDAY THROUGH SATURDAY

A GRADUAL EXPANSION OF THE LOWER HEIGHT FIELD ASSOCIATED WITH THE 
NORTHERN STREAM CENTRAL CANADIAN TROUGH WILL WORK INTO SE MICHIGAN 
ON MONDAY.  THIS PROCESS WILL HELP INITIATE THE EARLY AND WEAKER 
STAGES OF WHAT BECOMES ROUGHLY A 60 HOUR PERIOD OF COLD AIR 
ADVECTION THAT WILL DEFINE WEATHER CONDITIONS THROUGHOUT THE EARLY 
AND MID WEEK PERIODS. LEAD FRONTAL BOUNDARY WILL EXIT TO THE SOUTH 
BY MONDAY MORNING...THE ENSUING COLD AIR ADVECTION DROPPING 
TEMPERATURES WITHIN THE 850-925 MB LAYER 4-5 DEGREES RELATIVE TO 
TODAY.  LOW LEVEL FLOW OUT OF THE NORTHWEST FAVORS A DRIER LOW LEVEL 
MOISTURE PROFILE...THE LIMITED DEPTH SUGGESTING AT LEAST PARTIAL 
SUNSHINE WITH SIMPLY A FEW FLURRIES WITHIN ANY POCKETS OF STRATOCU 
WITH THE CLOUD LAYER RESIDING AROUND -12C.  HIGHS UPPER 20S NORTH TO 
LOWER 30S SOUTH.  
 
COLD AIR ADVECTION WILL STRENGTHEN INTO TUESDAY AS THE PASSAGE OF 
WEAK SHORTWAVE ENERGY PROVIDES A MORE SIZABLE SOUTHWARD EXPANSION OF 
THE EXISTING LOWER HEIGHT FIELD.  THIS PROCESS WILL CONTINUE THROUGH 
TUESDAY NIGHT...REINFORCED BY A SECONDARY AND STRONGER ELONGATED 
WAVE OF ARCTIC ORIGIN TRANSLATING THROUGH.  850 MB TEMPERATURES 
REMAIN PROJECTED TO BOTTOM OUT IN THE -18C RANGE BY WEDNESDAY.  
HIGHS WILL ARRIVE IN THE 20S BOTH DAYS /COLDEST WEDNESDAY/...THE 
FIRST TIME FOR CONSECUTIVE DAYS BELOW THE 30 DEGREE MARK SINCE LATE 
NOVEMBER.  SUPPRESSED INVERSION HEIGHTS WITH LIMITED MOISTURE DEPTH 
ABOVE 850 MB MAINTAINS A LACKLUSTER PROFILE FOR GREATER DOWNSTREAM 
PENETRATION OF LAKE MOISTURE AND ASSOCIATED SNOW SHOWERS THROUGH 
THIS TIME...DESPITE A GENERAL REALIGNMENT OF THE FLOW TOWARD WEST-
NORTHWEST BY WEDNESDAY.  VOID OF ANY TANGIBLE FORCING AT THIS 
STAGE...LOOKING AT NOTHING MORE THAN THE OCCASIONAL FLURRIES.
 
UPPER TROUGHING FIRMLY ENTRENCHED THROUGH NEW YEARS DAY...MODEST 
RECOVERY OFF THE COLD MORNING LOWS /TEENS/ WILL AGAIN LEAVE HIGHS IN 
THE 20S.   DEEPENING SOUTHWEST FLOW IMMEDIATELY DOWNSTREAM OF THE 
SOUTHWEST CONUS CUTOFF LOW SET TO EJECT EAST INITIATES A SOLID 
RESPONSE IN WARM AIR ADVECTION AND MOISTURE TRANSPORT BY FRIDAY.  
THIS WILL LIKELY INTRODUCE A LEAD CORRIDOR OF PRECIPITATION WITHIN 
THE EXPANDING WING OF ISENTROPIC ASCENT...AS EARLY AS FRIDAY NIGHT.  
TOO EARLY AT THIS STAGE TO PROPERLY DELINEATE PTYPE...BUT BOTH THE 
ECMWF AND GFS POINT TOWARD A THERMAL PROFILE STILL COLD ENOUGH FOR 
SNOW AT LEAST AT THE ONSET.  BEYOND THIS...THE USUAL UNCERTAINTY 
REMAINS AT THIS TIMESCALE IN TERMS OF TIMING...STRENGTH AND TRACK OF 
THE PARENT UPPER LOW/WAVE PROJECTED TO OPEN UP AND WORK EAST-
NORTHEAST ACROSS THE MIDWEST THROUGH SATURDAY.  SUBSEQUENT MODEL 
TREATMENT OF THE MATURATION OF THIS SYNOPTIC SYSTEM AS IT PULLS EAST 
OF THE MISSISSIPPI WILL CERTAINLY BE WORTH MONITORING GOING FORWARD.

MARINE...

RECENT OBSERVATIONS ACROSS NORTHERN LAKE HURON INDICATE WINDS ARE 
DIMINISHING IN SPEED EARLY THIS MORNING.  THIS WILL SUPPORT ALLOWING 
THE ONGOING GALE WARNING AND SMALL CRAFT HEADLINES TO EXPIRE AS 
SCHEDULED.  A MODEST WESTERLY WIND WILL REMAIN IN PLACE TODAY.  
WINDS WILL SHIFT TO NORTHWESTERLY AS MUCH COLDER AIR FUNNELS IN 
THROUGH THE EARLY WEEK PERIOD.  DESPITE THIS WIND SPEEDS WILL REMAIN 
AT MODERATE LEVELS BOTH MONDAY AND TUESDAY.  THERE WILL BE SOME 
INCREASE IN WINDS BY WEDNESDAY AND THURSDAY.  THIS WILL BRING THE 
POTENTIAL FOR A PERIOD OF WEST OR SOUTHWEST GALES OVER PORTIONS OF 
LAKE HURON DURING THIS TIME.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LAKE HURON...NONE.
LAKE ST CLAIR...NONE.
MICHIGAN WATERS OF LAKE ERIE...NONE.
&&

$$

AVIATION.....DRK
SHORT TERM...DRK
LONG TERM....MR
MARINE.......MR


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