Area Forecast Discussion
Issued by NWS Gaylord, MI

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000
FXUS63 KAPX 172315
AFDAPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GAYLORD MI
615 PM EST WED DEC 17 2014

.NEAR TERM...(THIS EVENING THROUGH TONIGHT)
ISSUED AT 407 PM EST WED DEC 17 2014

...WIDESPREAD SNOW TAPERS TO SNOW SHOWERS THIS EVENING...

HIGH IMPACT WEATHER POTENTIAL: SYNOPTIC SNOW TRANSITION TO LAKE
INDUCED SNOW SHOWERS THIS EVENING FOR NORTHERN LOWER.

PATTERN SYNOPSIS/FORECAST: 19Z SURFACE ANALYSIS SHOW FILLING LOW
PRESSURE ALONG THE SOUTHERN QUEBEC BORDER...THERMALLY INDUCED TROUGH
AXIS EXTENDS BACK TO THE WEST THROUGH THE STRAITS REGION INTO
WESTERN UPPER.  ENHANCED BAROCLINICITY ALONG THIS TROUGH
(ESSENTIALLY A COLD FRONT) WITH TEMPERATURES IN THE TEENS TO THE
EAST OF LAKE SUPERIOR.  WATER VAPOR IMAGERY HIGHLIGHTS AND ELONGATED
POTENTIAL VORTICITY AXIS FROM THE EASTERN DAKOTAS SOUTHEAST INTO
SOUTHERN LOWER MICHIGAN/SOUTHERN NEW YORK.  ALONG THE NORTHERN EDGE
OF THIS PV ANOMALY IS WIDESPREAD LIGHT SNOWFALL ACROSS NORTHERN
MICHIGAN WITH SOME ENHANCEMENT OFF LAKE MICHIGAN INTO NORTHWEST
LOWER.  SNOW/LIQUID RATIOS HAVE BEEN LOW/WET DURING THIS EVENT (4:1-
7:1 COMMON)...LOTS OF SMALL FLAKE SNOW OUT THE WINDOW THAT IS GOOD
AT REDUCING VISIBILITIES BUT NOT ACCUMULATING EFFICIENTLY.

POTENTIAL VORTICITY ANOMALY WILL TRACK EAST QUICKLY ACROSS SOUTHERN
LOWER MICHIGAN THIS EVENING...AS SURFACE TROUGH/COLD FRONT SAGS INTO
NORTHERN LOWER.

PRIMARY FORECAST CONCERNS: TRANSITION FROM SYNOPTIC/LAKE ENHANCED
SNOWFALL TO MORE TYPICAL LAKE INDUCED SNOW SHOWERS.

TONIGHT: STILL SOME SNOW WRAPPING INTO NORTHERN MICHIGAN FROM
NORTHEAST ONTARIO AT LATE AFTERNOON...BUT ARRIVAL OF STRONG DOWNWARD
QG FORCING THIS EVENING EXPECTED TO BRING WIDESPREAD SNOW TO AN
END...WITH A TRANSITION TO MORE PURE LAKE INDUCED CONVECTION
DOWNWIND OF LAKES MICHIGAN/HURON AS BOUNDARY LAYER FLOW EXPECTED TO
BECOME MORE NORTHERLY.  WILL ISSUE A SPECIAL WEATHER STATEMENT AT
FORECAST ISSUANCE TIME TO COVER SLIPPERY ROADS DUE TO WET SNOW AND
OCCASIONAL POOR VISIBILITY FOR THE AFTERNOON "DRIVE TIME" (OR WHAT
PASSES FOR SUCH ACROSS NORTHERN MICHIGAN).  EASTERN UPPER MICHIGAN
EXPECTED TO DRY OUT LATER THIS EVENING...WITH SOME OF THE COLD AIR
OVER THE NORTHERN ONTARIO PLATEAU DRAINING ACROSS THE ST. MARY`S
RIVER OVERNIGHT.  ACROSS NORTHERN LOWER...INCREASING SUBSIDENCE WILL
BEGIN TO PUSH INVERSION HEIGHTS DOWN FROM 850MB TO AROUND 900MB BY
THURSDAY MORNING.  BEST SNOWFALL POTENTIAL THEREFORE SHOULD BE
DURING THE EVENING HOURS...BUT WOULD ONLY EXPECT AN INCH OR TWO
ACROSS NORTHWEST LOWER MAINLY ALONG/WEST OF THE US-131 CORRIDOR.

&&

.SHORT TERM...(THURSDAY THROUGH SATURDAY)
ISSUED AT 407 PM EST WED DEC 17 2014

...QUIET AND COOL...

HIGH IMPACT WEATHER POTENTIAL: NONE.

PATTERN SYNOPSIS/ANTICIPATED EVOLUTION: PATTERN REMAINS FAIRLY
PROGRESSIVE...ALLOWING UPSTREAM DEEP LAYER RIDGING TO BUILD OVERHEAD
TO END THIS WEEK. RELATIVELY LOW AMP WAVE FOLLOWS FOR THE
WEEKEND...ALTHOUGH WITH A TOTAL DISCONNECT BETWEEN IT AND GULF
MOISTURE PLUME PLOWING THROUGH THE SOUTHEASTERN STATES. ALL IN
ALL...A FAIRLY BENIGN PATTERN (AT LEAST FOR NOW).

PRIMARY FORECAST CHALLENGES/CONCERNS: CLOUD TRENDS THROUGH THURSDAY
NIGHT. TEMPERATURE TRENDS THROUGH THE PERIOD.

DETAILS: AS MENTIONED...RATHER DEEP LAYER HIGH PRESSURE BUILDS
STEADILY OVERHEAD THURSDAY...EVENTUALLY CENTERING ITSELF ACROSS THE
AREA ON FRIDAY. MODEL SOUNDINGS/CROSS-SECTION MOISTURE ANALYSIS
CONTINUES TO SUPPORT LOW CLOUDS HANGING ON FOR MUCH OF NORTHERN
LOWER THURSDAY...WITH COOLING BOUNDARY LAYER AND STRONG SUBSIDENCE
INVERSION LOCKING IN STRATUS THROUGH MUCH OF THURSDAY NIGHT.
FORECAST ALREADY LARGELY TRENDED THIS DIRECTION BY PREVIOUS
FORECASTER...AND SIMPLY CAN FIND NO COMPELLING ARGUMENT AGAINST IT.
DEEP LAYER DRYING NORTH OF THE BIG BRIDGE SUPPORTS PLENTY MORE SUN
UP THAT WAY...WITH THIS CLEARING EVENTUALLY SPREADING SOUTH DURING
THE DAY FRIDAY. RIDGE DEPARTS FOR THE WEEKEND...REPLACED BY A
COMPLETELY MOISTURE AND DYNAMICALLY STARVED TROUGH AXIS. OTHER THAN
PERHAPS SOME INCREASING HIGH/MID CLOUDS...JUST NOT SEEING MUCH
OPPORTUNITY FOR ANY PRECIPITATION WITH THIS FEATURE.

TEMPERATURES: NEAR SEASONAL READINGS FOR THIS TIME OF THE
YEAR...WITH HIGHS GRADUALLY MODERATING FROM THE MID 20S/LOWER 30S
THURSDAY TO THE LOWER/MID 30S BY SUNDAY. OVERNIGHT LOWS MOSTLY IN
THE TEENS AND 20S.

&&

.LONG TERM...(SATURDAY NIGHT THROUGH WEDNESDAY)
ISSUED AT 407 PM EST WED DEC 17 2014

SATURDAY NIGHT THROUGH SUNDAY: FAIRLY QUIET DURING THIS PERIOD AS
HIGH PRESSURE GRADUALLY PUSHES TOWARD THE EAST COAST.

SUNDAY NIGHT THROUGH WEDNESDAY: GOOD AGREEMENT THAT A WEAK WAVE OF
LOW PRESSURE WILL BEGIN TO DIVE SOUTHEASTWARD OUT OF
CANADA...BECOMING CENTERED OVER THE DAKOTAS SUNDAY NIGHT. AS THIS
FEATURE DOES SO...THERE IS A SLIGHT CHANCE WE SEE A SHOT OF LIGHT
WARM AIR ADVECTION SNOW LATE SUNDAY NIGHT INTO EARLY MONDAY MORNING
OVER THE NORTHWESTERN THIRD OF THE CWA...BUT NOT MUCH EXPECTED IN
THE WAY OF IMPACTS AS SNOW AMOUNTS WOULD REMAIN MINOR.

MORE IMPRESSIVELY DURING THE DAY ON MONDAY...A 160-180 KT PACIFIC JET
BEGINS TO DIVE FROM THE PACIFIC NORTHWEST INTO THE CENTRAL
ROCKIES...AIDING IN DIGGING AN IMPRESSIVE TROUGH INTO THE SOUTHERN
CONUS BY TUESDAY MORNING. AS ENERGY ROUNDS THE BASE OF THE TROUGH
TUESDAY NIGHT...THE TROUGH BECOMES NEGATIVELY TILTED BY WEDNESDAY
MORNING AND CONTINUES TO STRENGTHEN AS REFLECTED BY THE DEEPENING
~970 MB SURFACE LOW MOVING FROM THE OHIO VALLEY INTO THE THUMB/FAR
SOUTHERN ONTARIO DURING THE DAY ON WEDNESDAY.

IN TERMS OF LOCAL IMPACTS...THERE IS FAIRLY DECENT AGREEMENT THAT
DESPITE TIMING DIFFERENCES IN TERMS OF THE PRECIP ARRIVAL THAT 850
MB TEMPERATURES WILL REMAIN BELOW 0C FOR MUCH OF THE EVENT.
HOWEVER...PRECIP COULD FALL AS RAIN FOR A PORTION OF THE EVENT AS
925 MB AND SFC TEMPS REMAIN ABOVE FREEZING BEFORE THE LOW PUSHES
NORTH WELL INTO CANADA ALLOWING FOR COLD AIR TO SURGE INTO THE AREA.
THIS PUSH OF COLD AIR MAY NOT OCCUR IN FULL FORCE UNTIL TOWARD THE
VERY TAIL END OF THE PERIOD & BEYOND. WITH THIS BEING SAID AND
FAIRLY GOOD MODEL CONSISTENCY OF A DEVELOPING SYSTEM OVER THE
EASTERN HALF OF THE CONUS...SMALL DEVIATIONS TO THE TRACK AND
OVERALL EVOLUTION OF THIS SYSTEM CAN AND WILL RESULT IN LARGE
CHANGES TO THE SENSIBLE WEATHER FELT ACROSS THE CWA. DEFINITELY
SOMETHING TO KEEP AN EYE ON AS WE HEAD INTO THE HOLIDAY TRAVEL
TIME FRAME.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z THURSDAY EVENING)
ISSUED AT 615 PM EST WED DEC 17 2014

WIDESPREAD SNOW WILL STEADILY END FROM WEST OF EAST ACROSS NRN LWR
MICHIGAN THIS EVENING AS LOW PRESSURE CONTINUES TO PULL AWAY FROM
OUR STATE. A BRIEF PERIOD OF LIGHT N/NW FLOW LAKE EFFECT SNOW
SHOWERS IS EXPECTED TO DEVELOP IN ITS WAKE...MAINLY FOR THE
OVERNIGHT HOURS...IMPACTING MAINLY TVC AND MBL WHERE MVFR
CONDITIONS WILL PREVAIL THRU THE NIGHT. DRIER AND WARMER AIR ALOFT
WILL BUILD INTO THE REGION ON THURSDAY...BRINGING AN END TO THE
SNOW SHOWERS AND IMPROVING CONDITIONS TO VFR. N/NW WINDS WILL
REMAIN AOB 10 KT THRU THE FORECAST PERIOD.

&&

.MARINE...
ISSUED AT 407 PM EST WED DEC 17 2014

GUSTY NORTHWEST TO NORTH WINDS TO CONTINUE THIS EVENING... WITH
SPEEDS LOWER OVERNIGHT AS HIGH PRESSURE BEGINS TO BUILD ACROSS THE
LAKES. LIGHT NORTH WINDS EXPECTED THURSDAY THROUGH FRIDAY AS HIGH
PRESSURE GRADUALLY CENTERS ITSELF OVERHEAD. WINDS LOOK TO REMAIN
LIGHT RIGHT THROUGH THIS UPCOMING WEEKEND.

&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LH...NONE.
LM...SMALL CRAFT ADVISORY UNTIL 1 AM EST THURSDAY FOR LMZ323-342-
     344>346.

LS...NONE.
&&

$$

NEAR TERM...JPB
SHORT TERM...MSB
LONG TERM...GILLEN
AVIATION...MLR
MARINE...MSB


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