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AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
552 AM EST WED JAN 28 2015


.AVIATION...

HIGH PRESSURE WILL BRING VFR CONDITIONS TODAY...BUT CLOUDS 
WILL INCREASE TONIGHT AS THIS HIGH SHIFTS EAST AND LOW PRESSURE 
APPROACHES FROM THE WEST. CIGS SHOULD REMAIN AOA 10KFT OR SO MUCH OF 
THE NIGHT...BUT MVFR CIGS/VSBYS WILL LIKELY DEVELOP KMBS/KFNT AFTER 
09Z-10Z AS -SN BR WORK INTO THE AREA WITH THIS SYSTEM.

FOR DTW...LIGHT SNOW AND MVFR CONDITIONS SHOULD HOLD OFF UNTIL AFTER 
12Z THURSDAY.

//DTW THRESHOLD PROBABILITIES...

* LOW IN CIGS AOB 5000 FEET LATE TONIGHT...WITH HIGHER CONFIDENCE 
  THURSDAY MORNING.

&&

.PREV DISCUSSION...ISSUED 309 AM EST WED JAN 28 2015 

SHORT TERM...TODAY AND TONIGHT

AFTER A CHILLY START...TEMPERATURES WILL REBOUND TO NEAR 30 DEGREES 
TODAY AS SOUTHERLY WINDS INCREASE IN ADVANCE OF AN APPROACHING WAVE 
OF LOW PRESSURE. MOSTLY SUNNY SKIES WILL GIVE WAY TO INCREASING HIGH 
CLOUDINESS AS THE LEADING EDGE OF MOISTURE ASSOCIATED WITH THE WAVE 
OVERSPREADS THE AREA.

CLOUDS WILL THEN THICKEN AND LOWER GRADUALLY INTO TONIGHT AS THIS 
SYSTEM MOVES INTO THE CENTRAL GREAT LAKES WITH LIGHT SNOW LIKELY 
DEVELOPING LATE TONIGHT OVER PARTS OF THE AREA. ACCUMULATIONS WILL 
BE MINIMAL PRIOR TO 12Z WITH JUST A FEW TENTHS OF AN INCH AT MOST. 
TEMPERATURES...MEANWHILE...WILL REMAIN RELATIVELY MILD AS CLOUDS 
INCREASE WITH LOWS HOLDING IN THE LOWER 20S.

LONG TERM...

UPPER JET WILL INTENSIFY OVER NORTHERN CANADA TODAY AS EAST PAC 
RIDGING BUILDS TOWARD DIGGING HIGH-LATITUDE ENERGY OVER NORTHERN 
ALASKA AND THE NW TERRITORIES AT 07Z THIS MORNING. THIS JET 
ENHANCEMENT WILL HELP TO AMPLIFY A NORTHERN STREAM TROUGH THAT WILL 
ABSORB THE SHORTWAVE OVER SOUTHERN ALBERTA/SASKATCHEWAN THIS MORNING 
BY LATE TONIGHT INTO EARLY THURSDAY. THE DIGGING TROUGH WILL ALSO 
STEER THE REMNANT BAJA ENERGY OVER WYOMING ACROSS THE OHIO VALLEY.

MERIDIONALLY ORIENTED SURFACE TROUGH WILL TRANSIT THE STATE ON 
THURSDAY, ANCHORED ON BOTH ENDS BY WEAK LOW PRESSURE CENTERS TIED TO 
NORTHERN & SOUTHERN FORCING MAXIMA ACCORDINGLY. AS NOTED IN THE 
PREVIOUS FORECAST PACKAGE, IT IS REASONABLE TO RESPECT MODEL 
SOLUTIONS LEANING TOWARD A STRONGER SOUTHERN WAVE GIVEN LIMITED 
UPSTREAM STATIC STABILITY THAT WILL FAVOR STRONGER LARGE SCALE 
ASCENT. THE 00Z GFS HAS, IN FACT, TRENDED IN THIS DIRECTION. THE 
ECMWF HAS SHOWN LITTLE CHANGE AND DEPICTS A MORE OPEN SURFACE 
CIRCULATION, BUT STILL STRONGER THAN THE REMAINING GUIDANCE. RESPECT 
IS GIVEN TO THE 00Z GFS, BUT AS A 4+MB OUTLIER AT THIS RATHER SHORT 
LEAD TIME, DECIDED AGAINST A FULL BUY-IN.

EXPECTATIONS FOR GENERAL EVOLUTION REMAIN LARGELY UNCHANGED 
REGARDLESS. LOW-LEVEL JET RESPONSE WILL DEVELOP OVER THE MIDDLE 
MISSISSIPPI VALLEY WITHIN BROADER SOUTHERLY FLOW REGIME TODAY BEFORE 
PROGRESSING EAST ACROSS THE AREA 6-12Z TONIGHT. WARMING OF THE MID-
LEVELS WILL BRING BRIEF BUT WELL-DEFINED WINDOW FOR FREEZING RAIN 
ACROSS SOUTHERN AREAS DURING THE MORNING. ONGOING SURFACE WARM 
ADVECTION AND DIURNAL HEATING WILL JEOPARDIZE SNOW CHANCES SOUTH OF 
AT LEAST I-94 FOR THE NEXT SEVERAL HOURS WHERE MIDDAY CONDITIONS 
WILL BE STRONGLY DEPENDENT ON THE STRENGTH OF THE SURFACE LOW. NORTH 
OF I-69, WEAK DEFORMATION AND MORE FAVORABLE THERMODYNAMIC PROFILES 
SHOULD HELP TRANSLATE 0.25" QPF INTO 2-3" OF SNOW ACCUMULATION. IN 
BETWEEN, MAINLY SNOW IS EXPECTED BETWEEN ROUGHLY I-696/M59, ALTHOUGH 
A DEEP LAYER OF TEMPERATURES DECIDEDLY WARMER THAN -10C THROUGH THE 
LOWEST 10KFT WILL SIGNIFICANTLY REDUCE SNOW RATIOS. HERE, 
ACCUMULATIONS ARE FORECAST TO RANGE FROM 0.5 TO 1.5". THE BEST SHOT 
OF ACCUMULATING SNOW FOR THE SOUTHERN 2/3 OF THE AREA WILL MOST 
LIKELY BE IMMEDIATELY IN THE WAKE OF THE SURFACE COLD FRONT AFTER 
20Z, WHEN COOLING THERMAL PROFILES WILL SUPPORT BETTER DENDRITE 
PRODUCTION PRIOR TO THE EXIT OF THE DEEPER MOISTURE.

DIGGING HIGH-LATITUDE ENERGY WILL PUSH A STRONG COLD FRONT THROUGH 
THE AREA FROM NW TO SE THURSDAY NIGHT. THIS SHOT OF COLD ADVECTION 
WILL DROP 925MB TEMPERATURES FROM A PEAK OF NEAR 0C DURING THURS 
AFTERNOON TO -17C FRIDAY MORNING. NORTHWEST FETCH SHOULD DEFLECT ANY 
LAKE EFFECT TO THE SOUTHWEST, BUT BOTH LAKE CLOUDS AND LES LOOK TO 
BE HARD TO COME BY GIVEN MODEL DEPICTIONS OF RAPIDLY BUILDING HIGH 
PRESSURE THURSDAY NIGHT. HIGHS FRIDAY WILL BE LIMITED TO THE 
MID/UPPER TEENS IN MOST SPOTS DESPITE PROSPECTS FOR MOSTLY SUNNY 
SKIES. QUICK REBOUND OF THE HEIGHT FIELD DOWNSTREAM OF PAC ENERGY 
STREAMING INTO THE WESTERN U.S. WILL HELP TEMPS RECOVER INTO THE MID 
20S ON SATURDAY.

FINALLY, MODEL CONSENSUS IS INCREASING THAT A WIDE SWATH OF 
ACCUMULATING SNOW WILL DEVELOP OVER THE OHIO VALLEY AND GREAT LAKES 
SATURDAY NIGHT INTO SUNDAY NIGHT. THIS WILL OCCUR AS A NORTHERN WAVE 
DIGS INTO THE WESTERN PLAINS AND ENTRAINS A HIGHLY UNCERTAIN 
PERCENTAGE OF ENERGY FROM A CLOSED LOW OVER THE 4 CORNERS. BROAD 
REGION OF NORTHWARD MOISTURE TRANSPORT AND STRONG LARGE SCALE RIGHT 
ENTRANCE JET SUPPORT FAVOR RETAINING THE ENTRY-LEVEL LIKELY POPS 
INTRODUCED BY THE BLENDED EXTENDED GRIDS.

MARINE...

FRESH TO STRONG SOUTHERLY WINDS WILL DEVELOP LATE TONIGHT INTO 
THURSDAY MORNING AS A WEAK LOW PRESSURE SYSTEM TRAVERSES THE GREAT 
LAKES. STABLE SOUTHERLY FLOW REGIME WILL LIMIT THE POTENTIAL FOR 
WIND GUSTS. THEREFORE...WHILE AN ISOLATED GUST TO GALE FORCE IS 
POSSIBLE OVER LAKE HURON...COVERAGE AND DURATION WILL MEET GALE 
CRITERIA. A STRONG COLD FRONT WILL THEN SURGE ACROSS THE WATERS ON 
THURSDAY NIGHT. MUCH COLDER NORTHWEST FLOW WILL SUPPORT WIDESPREAD 
GUSTS TO STRONG GALES ACROSS ALL OF LAKE HURON INCLUDING THE 
NEARSHORE WATERS. SIGNIFICANT WAVE HEIGHTS WILL EXCEED 12 FEET OVER 
THE SOUTHERN HALF OF LAKE HURON BY LATE THURSDAY NIGHT. WINDS AND 
WAVES WILL SUBSIDE FRIDAY INTO FRIDAY NIGHT.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LAKE HURON...GALE WATCH FROM THURSDAY EVENING THROUGH FRIDAY MORNING FOR 
     LHZ361>363-421-441>443-462>464.

LAKE ST CLAIR...NONE.
MICHIGAN WATERS OF LAKE ERIE...NONE.
&&

$$

AVIATION.....DG
SHORT TERM...DG
LONG TERM....JVC
MARINE.......JVC


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