Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 051748
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
1248 PM EST FRI FEB 5 2016


.AVIATION...

WEAK SHORTWAVE ENERGY RESIDES ALONG THE LEAD WARM ADVECTION SURGE TO
THE RISING HEIGHTS. THIS SHORTWAVE WILL TRACK THROUGH THE SAGINAW
VALLEY AND NORTHERN THUMB THIS AFTERNOON....BRINGING A CHANCE FOR
LIGHT SNOW SHOWERS TO THE NORTHERN TERMINALS. RECENT SURFACE
OBSERVATIONS AND MODEL DATA SUPPORTS ENOUGH OF A FAVORABLE
ENVIRONMENT TO SUPPORT A POTENTIAL WINDOW BETWEEN 19-23Z FOR IFR
VISIBILITY RESTRICTIONS IN LIGHT SNOW. WARM BOUNDARY LAYER
TEMPERATURES AT OR JUST ABOVE FREEZING WILL MITIGATE MUCH OF THE
IMPACTS. FARTHER SOUTH...THERE WILL BE A CHANCE FOR P6SM
FLURRIES...DURING THE LATE AFTERNOON BUT THE OVERALL CONVERGENCE
SIGNAL WITHIN THE DATA THAT FAR SOUTH IS WEAK WITH LOW CONFIDENCE.
WEAK SHORTWAVE RIDGING TONIGHT WILL SUPPORT A RETURN TO VFR CIGS
THROUGH THE END OF THE PERIOD WITH SOUTHWESTERLY WIND DIRECTIONS
EXPECTED TO PERSIST.

FOR DTW...RISING HEIGHTS LED TO A PERIOD OF WIDESPREAD VFR
CONDITIONS THIS MORNING. SHORTWAVE ENERGY PASSING TO THE NORTH OF
THE TERMINAL WILL BRING THE POTENTIAL FOR A P6SM SNOW SHOWER CHANCE
THIS AFTERNOON...BUT CONFIDENCE IS TOO LOW FOR EXPLICIT MENTION.
WILL ALSO MONITOR THE EXPANSION OF THE MVFR STRATOCUMULUS OVER
PORTIONS OF IL/IN DURING THE AFTERNOON. THIS CLOUD RESIDES IN AN
AREA OF COLD ADVECTION THAT IS FORECASTED TO SLIDE THROUGH
SOUTHEASTERN MICHIGAN THIS EVENING. CONFIDENCE IN WHAT THIS CLOUD
WILL DO IS VERY LOW AS THERE IS CURRENTLY A DIURNAL HEATING BOOST.
THIS POTENTIAL FOR MVFR WAS REFERENCED IN THE PRIOR DISCUSSION FOR
01-03Z.

//DTW THRESHOLD PROBABILITIES...

* HIGH FOR CIGS AOB 5KFT DURING THE LATE AFTERNOON AND EVENING. LOW
  FOR LATE TONIGHT.

&&

.PREV DISCUSSION...ISSUED 347 AM EST FRI FEB 5 2016

DISCUSSION...

BENIGN CONDITIONS OVER THE NEXT COUPLE OF DAYS WILL NOT BE FOR A
LACK OF WEATHER FEATURES MOVING THROUGH THE GREAT LAKES...JUST THAT
THEY WILL PRODUCE ONLY TRACE AMOUNTS OF PRECIPITATION IF ANY AND
ALLOW TEMPERATURES TO HOLD A FEW DEGREES ABOVE NORMAL FOR EARLY
FEBRUARY. READINGS WILL EXTEND MORE ABOVE NORMAL SUNDAY AHEAD OF
THE NEXT LARGER LOW PRESSURE SYSTEM THAT WILL BRING OUR NEXT SOLID
CHANCE OF RAIN/SNOW SHOWERS SUNDAY NIGHT INTO MONDAY.

THE FIRST OF TWO WEAKER LOW PRESSURE SYSTEMS WILL EXIT THE GREAT
LAKES DURING THE MORNING AND PULL A FILLING OCCLUDED FRONT THROUGH
OUR AREA. COMPARED TO YESTERDAY...THIS WILL ACT MORE AS A WARM FRONT
THAT WILL SCOUR THE LOW LEVEL THERMAL TROUGH EASTWARD WHILE
OTHERWISE ONLY ABLE TO SUPPORT SCATTERED TO BROKEN CLOUD COVER
THROUGH THE DAY AUGMENTED BY SOME MOISTURE FROM LAKE MICHIGAN. MODEL
FORECAST SOUNDINGS DO AGREE THAT SOME STEEPER LAPSE RATES WILL
LINGER THROUGH THE LOW LEVELS WITH SOME SUPERSATURATION WRT ICE THAT
COULD SUPPORT SOME FLURRIES WITHIN THE REMNANT SURFACE TROUGH DURING
THE AFTERNOON. AT THE SAME TIME...SUBSIDENCE UNDER THE SHORT WAVE
RIDGE ALOFT WILL SQUASH CONVECTIVE DEPTH TO ABOUT 850 MB WHICH
SUGGESTS HOLDING THE LINE ON JUST A CLOUD MENTION FOR NOW.

THE DYING FRONTAL SYSTEM TODAY WILL BE FOLLOWED QUICKLY BY THE NEXT
SHORT WAVE MOVING FROM THE PLAINS INTO THE GREAT LAKES TONIGHT. THE
SYSTEM MAINTAINS DECENT STRUCTURE ALOFT BUT IS FEATURELESS IN TERMS
OF SURFACE PRESSURE. HIGH STATIC STABILITY IN THE LOW LEVELS WITH A
LACK OF BAROCLINICITY AND MOISTURE DOES NOT SUPPORT CYCLOGENESIS
ANYWHERE EXCEPT FARTHER NORTH TOWARD THE ARCTIC FRONT. THE UPPER
WAVE DOES WHAT IT CAN WITH CHINTZY PACIFIC MOISTURE IN THE MID
LEVELS WHILE THE GULF REMAINS CLOSED BY HIGH PRESSURE RUNNING FROM
EASTERN TEXAS TO THE MID ATLANTIC. MODEL SOLUTIONS THEREFORE LOOK ON
TARGET IN KEEPING THINGS DRY OVER LOWER MICHIGAN THROUGH SATURDAY
NIGHT.

THE CURRENT GULF OF ALASKA UPPER LOW IS THE ONE THAT WILL MAKE IT
INTO THE GREAT LAKES BY SUNDAY NIGHT INTO MONDAY. IT WILL BE A
CONSIDERABLY LARGER AND STRONGER SYSTEM COMPARED THOSE OF TODAY AND
SATURDAY...AND IT WILL HAVE A CHANCE TO TAP SOME MODIFIED
CONTINENTAL AIR FROM THE GULF COAST BY THEN TO SUPPORT LIKELY POPS.
STRONG SOUTHWEST LOW LEVEL FLOW WILL ALSO BRING EVEN WARMER AIR INTO
THE REGION WHICH FAVORS THE WARM SIDE OF TEMPERATURE GUIDANCE ACROSS
THE AREA. MAX TEMPS IN THE MID 40S OHIO BORDER TO UPPER 30S NORTHERN
THUMB LOOK VERY REACHABLE BY SUNDAY AFTERNOON BEFORE PRECIP MOVES
INTO THE REGION. THE WARM BOUNDARY LAYER WILL SUPPORT RAIN OR A
RAIN/SNOW MIX INITIALLY SUNDAY EVENING. EXPECT GRADUAL CHANGE OVER
TO SNOW AROUND MIDNIGHT AS WET BULB AND DIURNAL COOLING BEGIN TO
DOMINATE THE TEMPERATURE PROFILE. THIS APPEARS BETTER REPRESENTED BY
NAM SOUNDINGS AT THIS POINT BUT WHICH ARE STILL CLOSE TO 0C IN THE
BOUNDARY LAYER EVEN BY MONDAY MORNING. THE WARM PROFILE AND LATE
CHANGE OVER WILL KEEP ACCUMULATION MINIMAL.

EXTENDED MODEL SIMULATIONS ARE IN GOOD AGREEMENT WITH A CLOSED LOW
SOLUTION OVER THE GREAT LAKES AND OHIO VALLEY MONDAY AND TUESDAY.
THE ECMWF OFFERS PERSISTENCE OF THE SURFACE LOW AND MID LEVEL
MOISTURE AXIS RIGHT OVER SE MICHIGAN WHICH WOULD PRODUCE AN ACTIVE
PERIOD OF SNOW SHOWERS FOR THE FIRST HALF OF NEXT WEEK. ASSUMING
THE SYSTEM DOES LIFT AWAY DURING WEDNESDAY...THEN COLDER AIR WILL
TAKE ITS PLACE FOR THE SECOND HALF OF THE WEEK.

MARINE...

LIGHT TO MODERATE WSW WINDS WILL INCREASE DURING THE DAY SATURDAY IN
ADVANCE OF THE NEXT LOW PRESSURE. WIND GUSTS WILL APPROACH 30 KNOTS
AT TIMES OVER CENTRAL LAKE HURON. EXPANSIVE LOW PRESSURE WILL THEN
SETTLE OVER THE GREAT LAKES FOR THE FOLLOWING SEVERAL DAYS. MODERATE
TO OCCASIONALLY FRESH WINDS WILL GRADUALLY BACK FROM SOUTHEASTERLY
EARLY SUNDAY TO NORTHWESTERLY BY WEDNESDAY.

&&

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

$$

AVIATION.....CB
DISCUSSION...BT
MARINE.......JVC


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