Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 282053
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
353 PM EST WED JAN 28 2015

.SHORT TERM...THIS EVENING

A DEPARTING LOW LEVEL ANTICYCLONE HAS MAINTAINED AMPLE LOW LEVEL DRY
AIR ACROSS SE MI TODAY. LIGHT S-SE RETURN FLOW HAS IN TURN ALLOWED
TEMPS TO RISE INTO THE UPPER 20S/LOW 30S. HIGH CLOUDS WILL BE ON THE
INCREASE DURING THE REST OF THE AFTERNOON...FOLLOWED BY INCREASING
MID LEVEL CLOUDS THIS EVENING. THIS WILL OCCUR AS THE BROAD RIBBON
OF WARM AIR ADVECTION/MID LEVEL MOISTURE TRANSPORT NOW EXPANDING
ACROSS THE WRN GREAT LAKES CONTINUES TO ADVANCE TO THE EAST. THERE
SHOULD BE JUST ENOUGH DECOUPLING IN THE BOUNDARY LAYER TO SUPPORT
SOME DEGREE OF TEMP DROP THIS EVENING. STRENGTHENING LOW LEVEL
SOUTHERLY FLOW AHEAD OF A SFC LOW WILL DRIVE WARMER AIR IN DURING
THE NIGHT. THIS ALONG WITH INCREASING CLOUDS WILL LEAD TO A SLOW
WARMING TREND AFTER MIDNIGHT.

&&

.LONG TERM...LATE TONIGHT THROUGH NEXT WEDNESDAY

THE BEST SHOT AT PRECIP IN THE COMING WEEK ARRIVES RIGHT AWAY ON
THURSDAY AS A PAIR OF WAVES ATTEMPTS TO PHASE OVER THE REGION. LOW
AMPLITUDE LONG WAVE PATTERN ACROSS THE WEST/CENTRAL CONUS WILL
TRANSITION TO DEEP TROUGHING OVER THE EASTERN CONUS. THIS WILL OCCUR
AS ENERGY RELEASED FROM THE ALASKAN BAY LOW SURGES DOWN INTO THE
MIDWEST. A CURRENT SOUTHERN STREAM WAVE AND RESULTANT SFC LOW OVER
THE CENTRAL PLAINS WILL TRACK EASTERLY THE SOUTHERN GREAT LAKES
THURSDAY...LOOKING TO STAY JUST AHEAD OF THE FIRST NOTABLE NORTHERN
STREAM WAVE. THIS INTERACTION IS KEY TO HOW THE SYSTEM WILL PLAY OUT
FOR SE MI. THE SLOWER THE NORTHERN STREAM WAVE IS...THE MORE LIKELY
THE SOUTHERN STREAM WAVE WILL REMAIN IN TACK...VS A FASTER WAVE
CATCHING UP AND PHASING DIRECTLY OVERHEAD. THIS WOULD DISRUPT THE
LOW...SHEARING IT NORTH/SOUTH THROUGH THE REGION AS IT TRIES TO
REDEVELOP FURTHER DOWNSTREAM. IN THE END...MODEL SUITE HAS TRENDED
TOWARD KEEPING SOME SEPARATION BETWEEN THE SYSTEMS...THUS HAVE
ADJUSTED THE FORECAST ACCORDINGLY. THE DETAILS TO FOLLOW...

WITH THE CENTRAL PLAINS SFC LOW BEING LESS AFFECTED BY THE INCOMING
WAVE/JET MAX INTO SOUTHERN MI...THE LOW WILL BE ABLE TO MAINTAIN
MORE OF ITS STRUCTURE/FORCING. THIS IS ALREADY BEING SHOWN IN THE
MODELS BY KEEPING THE STRONG BAND OF ISENTROPIC ASCENT IN TACK AS IT
LIFTS THROUGH SW/CENTRAL MI EARLY THURSDAY MORNING AND THE
DEFORMATION BAND AS IT SWINGS THROUGH THURSDAY AFTERNOON. IT ALSO
KEEPS BRINGS THE NOSE OF A THETA E PLUME UP THROUGH THE AREA BETWEEN
12-18Z WITH A DECENT GRADIENT ON THE LEAD EDGE. A DEEP LAYER OF DRY
AIR FROM THE SFC TO 700MB IN PLACE WEDNESDAY NIGHT WILL HOLD BACK
MUCH OF THE PRECIP TIL AFTER 12Z MONDAY...AT LEAST FOR LOCATIONS
EAST OF I75. THE LEAD ISENTROPIC LIFT ON THE NE SIDE OF THE LOW WILL
LIFT THROUGH THE SAGINAW BAY FROM ABOUT 09-12Z. THIS WILL GIVE THAT
AREA AROUND A HALF INCH OF SNOWFALL FOR THE MORNING COMMUTE WHILE
BEGINNING TO SATURATE THE LOW LEVELS ACROSS THE REST OF THE REGION.
AFTER 12Z...STRONG SW FLOW IN THE LOW LEVELS PROMOTES GOOD WAA IN
THE 900-800MB LAYER WITH TEMPS GOING NEARLY ISOTHERMAL IN THE LAYER
RIGHT AROUND 0C. MODELS VARY A DEGREE OR TWO WITH THE LL THERMAL
PROFILE IN THE 12-18Z TIMEFRAME. THIS LEADS TO A COMPLICATED MIXED
PRECIP SCENARIO OVER SOUTHERN MI INTO THE EARLY AFTERNOON. THE MIXED
PRECIP WILL END LATER IN THE AFTERNOON OR EARLY EVENING AS STRONG
CAA SURGES IN FROM THE NW BEHIND THE NORTHERN STREAM TROUGH. THIS
WILL TURN THE REMAINING PRECIP...MAINLY IN THE DEFORMATION
BAND...INTO ALL SNOW FOR THE TAIL END OF THE EVENT. LOOKING FOR A
POSSIBLE INCH OVER THE THUMB AS THE BAND SWEEPS THROUGH WITH LESS
THAN A HALF INCH FURTHER SOUTH NEAR DETROIT. MODELS ARE PRETTY WELL
IN LINE WITH QPF FOR THE EVENT...WHICH HAS NOT CHANGED MUCH OVER THE
LAST FEW MODEL RUNS...MAINTAINING AROUND 0.25 INCHES ACROSS THE
NORTH AND AROUND 0.15-0.20 INCHES ACROSS THE SOUTH. THE WARM AIR
ALOFT WILL REALLY CUT INTO SNOWFALL TOTALS ACROSS THE
AREA...ESPECIALLY SOUTH OF M59 WHERE A MIX OF FREEZING RAIN AND
SLEET WILL LIKELY OCCUR FOR SEVERAL HOURS BEFORE CAA COOLS THE
ENVIRONMENT ENOUGH FOR SNOW. NOT EXPECTING MUCH IN THE WAY OF ICE
ACCUMULATION AS THIS AREA WILL WARM INTO THE MID 30S WITH RAIN
POSSIBLE BY AFTERNOON. LOCATIONS BETWEEN I69 AND M59 WILL LIKELY SEE
MORE OF A SNOW/SLEET MIX RESULTING IN MINOR ACCUMULATIONS OF 1-2
INCHES. NORTH OF I69 STANDS THE BEST CHANCE TO SEE A PURE SNOW
EVENT...BUT WITH LOW SNOWFALL RATIOS WILL LIKELY ONLY AMOUNT TO 2-3
INCHES.

ONCE THE PRECIP ENDS THURSDAY NIGHT...A SECOND COLD FRONT WILL SWEEP
THROUGH DOWN THROUGH MI DROPPING 850MB TEMPS TO 15C. EVEN WITH HIGH
PRESSURE AND A GOOD DEAL OF SUNSHINE FRIDAY AFTERNOON...HIGH
TEMPERATURES WILL LIKELY ONLY RISE INTO THE TEENS. LOWS FRIDAY NIGHT
WILL DIP BACK INTO THE SINGLE DIGITS.

AS FAR AS THIS WEEKEND...MODELS ARE AGAIN JUMPING BACK AND FORTH ON
THE TRACK FOR THE SUNDAY SYSTEM.  LATEST MODEL RUNS ARE INDICATING A
WEAKER AND MORE SOUTHERN TRACK WITH THE MAIN JET ENERGY AND
SHORTWAVE ASSOCIATED WITH THIS SYSTEM STAYING TO THE SOUTH OF THE
AREA.  SEEING THE MODEL SOLUTIONS VARYING...HAVE GONE WITH CHANCE
POPS UNTIL MODELS COME TO INTO BETTER CONSENSUS.  AT THIS
POINT...THE BETTER LOCATIONS FOR SEEING ANY SNOW WOULD LIKELY BE
AREAS CLOSER TO THE OHIO BORDER.  COLDER TEMPS WILL HANG AROUND AS
THE GREAT LAKES REGION REMAINS IN THE LONGWAVE TROUGH THROUGH THE
REMAINDER OF THE EXTENDED.

&&

.MARINE...

SOUTH-SOUTHEASTERLY WINDS WILL BE ON THE INCREASE TONIGHT AS LOW
PRESSURE APPROACHES FROM THE WEST. THE RESULTING WARM AIR ADVECTION
WILL INHIBIT THE DEGREE OF MIXING OVER THE LAKES. SO ALTHOUGH MODEL
SOLUTIONS SUGGEST GALE FORCE WINDS DOWN TO 1K FT...THE SHALLOW
STABLE LAYER OVER THE LAKES WILL INHIBIT THE POTENTIAL FOR GALE
FORCE WIND GUSTS TO OCCUR OVER A PERIOD GREATER THAN THREE HOURS.
THIS SUGGESTS THAT A GALE WARNING FOR TONIGHT WILL NOT BE NEEDED.
ALTHOUGH FREQUENT GUSTS TO 30 KNOTS ARE EXPECTED...MAINLY LATE
TONIGHT THROUGH THURS MORNING. WINDS WILL DECREASE THURS AFTERNOON
AS THE SURFACE LOW TRACKS OVERHEAD AND THEN VEER TO THE WEST-
NORTHWEST LATE THURS AS THE LOW HEADS EAST OF LAKE HURON. ARCTIC AIR
WILL THEN INFILTRATE THE REGION WITH THE DEPARTURE OF THE SFC LOW.
THIS WILL BOOST MIXING DEPTHS OVER THE LAKE AND WILL SUPPORT GALE
FORCE WINDS GUSTS THURS NIGHT INTO FRIDAY MORNING AND LAKE HURON
BEFORE THE GRADIENT WEAKENS SUBSTANTIALLY FRI AFTERNOON. THE GALE
WATCH WILL REMAIN IN PLACE FOR LAKE HURON WITH GROWING CONFIDENCE
THAT THIS WILL BE UPGRADED TO A GALE WARNING EITHER THIS EVENING OR
EARLY THURS MORNING.

&&

.AVIATION...ISSUED 1202 PM EST WED JAN 28 2015

VERY DRY AIR IN THE LOW LEVELS ASSOCIATED WITH HIGH PRESSURE
DEPARTING TO THE EAST WILL MAINTAIN CLEAR SKIES BELOW 10K FT THROUGH
THE AFTERNOON AND EVENING. STRENGTHENING SOUTHERLY FLOW AHEAD OF AN
APPROACHING SFC LOW RAISES SOME CONCERN FOR LOW LEVEL WIND SHEAR
OVERNIGHT WITH WINDS FORECAST TO INCREASE TO 45 KNOTS AT 2K FT.
CURRENT INDICATIONS ARE THAT THERE WILL BE ENOUGH MIXING NEAR THE
SURFACE TO LEAD TO MORE OF A LOW LEVEL TURBULENCE SITUATION /GUSTY
SFC WINDS/ PRIMARILY BETWEEN 08Z THROUGH DAYBREAK. THIS LOW LEVEL
SYSTEM WILL BRING A MIX OF RAIN/SLEET/SNOW TO THE REGION STARTING
ROUGHLY AROUND 12Z. AN EARLIER ARRIVAL OF THE FORCING AND A COLDER
THERMAL PROFILE SUGGESTS ALL SNOW AT MBS...STARTING AROUND OR
SHORTLY AFTER 09Z.

FOR DTW...CONSIDERING THE DEGREE OF WARM AIR ALOFT FORECAST TO
OVERSPREAD METRO DETROIT...PRECIP IS EXPECTED TO START MAINLY AS
FREEZING RAIN. IT SHOULD TRANSITION OVER TO PURE RAIN DURING THE
COURSE OF THE MORNING AS SFC TEMPS WARM ABOVE FREEZING.

//DTW THRESHOLD PROBABILITIES...

* HIGH IN CIGS BELOW 5000 FT AFTER 10Z.

* MEDIUM IN PRECIP TYPE STARTING AS A FZRA/IP MIX THURS MORNING.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LAKE HURON...GALE WATCH FROM THURSDAY EVENING THROUGH FRIDAY MORNING FOR LHZ362-
     363-421-441>443-462>464.

     GALE WATCH FROM THURSDAY EVENING THROUGH LATE THURSDAY NIGHT FOR
     LHZ361.

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

$$

SHORT TERM...SC
LONG TERM....DRK/SS
MARINE.......SC
AVIATION.....SC


YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE
AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE).


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