Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 070444
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
1144 PM EST FRI MAR 6 2015


.AVIATION...

SOUTHWEST WINDS HAVE BROUGHT WARMER AIR OVER SOUTHEAST MICHIGAN
OVERNIGHT WITH THICKENING MID AND LOW LEVEL CLOUDS. MVFR CLOUDS HAVE
ALREADY DEVELOPED OVER MBS BUT HAVE NOT YET FORMED FROM FNT SOUTH TO
THE METRO AIRPORTS. UPSTREAM OBSERVATIONS SHOW FNT SHOULD DEVELOP
THIS DECK IN DUE TIME...HOWEVER PTK SOUTH TO THE METRO AIRPORTS DOES
NOT YET SHOW SIGNS OF THIS HAPPENING. MOS GUIDANCE IS MIXED WITH THE
GFS SHOWING NO MVFR DECK DEVELOPING WHILE THE NAM MOS DEVELOPS THIS
DECK DURING THE AFTERNOON HOURS. GIVEN THIS DECK IS AT LEAST IN
MICHIGAN WILL NOT COMPLETELY GET RID OF IT BUT WILL BRING IT IN
LATER WITH SOME SKEPTICISM ATTACHED TO THIS FORECAST. ONCE IN
PLACE...THE CLOUDS WILL TEND TO LINGER THROUGH SATURDAY NIGHT AS THE
MILDER AIR FLOWS OVER THE EXPANSE OF SNOW COVER EAST OF THE
MISSISSIPPI RIVER. REGARDING PRECIPITATION WITH THE FRONT...THIS
AFTERNOON WILL PRESENT A BETTER CHANCE OF SNOW WITH THE NEXT LOW
PRESSURE SYSTEM...BUT WILL STILL BE IN THE LOW CHANCY CATEGORY.

//DTW THRESHOLD PROBABILITIES...

* MODERATE FOR CEILING BELOW 5 KFT SATURDAY AFTERNOON AND SATURDAY
  NIGHT.

&&

.PREV DISCUSSION...ISSUED 343 PM EST FRI MAR 6 2015

SHORT TERM... AFTERNOON AND TONIGHT

INCREASING WIND HAS MAINTAINED AN EDGE TO THE FEEL OF TEMPERATURES
MANAGING TO RISE NEARLY 10 DEGREES WARMER TODAY THAN YESTERDAY
AROUND SE MICHIGAN. AFTERNOON HIGHS REACHING INTO THE LOWER HALF OF
THE 20S ARE BEING CUT BACK BY WIND CHILL CLOSER TO ZERO AT TIMES
THANKS TO SOUTHWEST WIND GUSTING AROUND 25 MPH. THAT SOUTHWEST WIND
FEELS HARSH BUT IS WELCOME AS IT SIGNALS THE BEGINNING OF A WARMING
TREND SET TO GET UNDERWAY THROUGH THE WEEKEND.

HIGH CLOUDS THICKENING DURING THE REST OF THE AFTERNOON AND LOWERING
THROUGH THE EVENING WILL BE ANOTHER SIGN OF WARMER AIR ON THE WAY.
THESE CLOUDS WILL BE A RESULT OF MID LEVEL ISENTROPIC ASCENT TIED TO
THE SURFACE WARM FRONT DEVELOPING OVER THE MIDWEST. THE ISENTROPIC
ASCENT WILL BE ADEQUATE FOR CLOUD DEVELOPMENT FROM A SYSTEM RELATIVE
PERSPECTIVE...BUT TOO WEAK FOR PRECIPITATION TO REACH THE GROUND.
POCKETS OF VIRGA ON RADAR WILL BE SYMPTOMATIC OF DIFFICULTY
SATURATING THE LOW LEVELS UNDER THE FRONTAL SLOPE JUDGING BY HOURLY
MODEL SOUNDINGS. A STRAY FLURRY WILL BE POSSIBLE AS THE MID LEVEL
THETA-E RIDGE MOVES THROUGH LOWER MICHIGAN DURING THE EVENING. AFTER
THAT...THE MID LEVEL THETA-E/MOISTURE AXIS WILL GET DEFLATED
OVERNIGHT AS THE WIND FIELD REORIENTS AHEAD OF THE NEXT WAVE
ARRIVING IN THE NORTHERN GREAT LAKES FROM CENTRAL CANADA. THIS WILL
STALL THE EASTWARD DEVELOPMENT OF THE SURFACE WARM FRONT BUT
MAINTAIN ENOUGH CLOUD COVER AND SOUTHWEST WIND OVER SE MICHIGAN TO
BOOST TEMPERATURES INTO THE LOWER 20S BY SUNRISE AFTER DROPPING INTO
THE TEENS FOR LOWS DURING THE LATE EVENING/AROUND MIDNIGHT.

LONG TERM...

FAST UPPER LEVEL NORTHWEST FLOW IN PLACE THIS WEEKEND...WITH
MULTIPLE SHORTWAVES TRACKING THROUGH THE AREA. ONE SUCH UPPER
WAVE/COLD POOL (-31 C AT 500 MB) TRACKS THROUGH SATURDAY
MORNING...WITH SURFACE TROUGH/COLD FRONT PROVIDING MODEST LOW LEVEL
CONVERGENCE...WORTHY OF CHANCE POPS. ESPECIALLY ACROSS THE NORTHERN
THUMB REGION WITH SUPPORT FROM A SECOND UPPER WAVE...WHICH WILL DROP
SOUTHEAST FROM LAKE SUPERIOR AND TRACK THROUGH NORTHERN LAKE HURON
EARLY SATURDAY AFTERNOON. WITH THE SOUTHWEST FLOW AND LOW LEVELS
(850 MB) STRUGGLING TO SATURATE...PREFERENCE IS WITH THE WARMER 12Z
MAV/EURO GUIDANCE WHICH SUPPORTS HIGHS PREDOMINATELY IN THE UPPER
30S TO AROUND 40 DEGREES...AS 925 MB TEMPS FORECASTED TO APPROACH
ZERO. FAIRLY COLD WESTERLY FLOW SATURDAY NIGHT...WITH NAM SOUNDINGS
EVEN INDICATING ENOUGH MOISTURE DEPTH/LOW LEVEL LAPSE RATES TO
SUPPORT FLURRIES. HOWEVER...12Z EURO IS MUCH DRIER...SEE 925 MB RH.
THUS...EXTENT OF CLOUD COVER AND AMOUNT OF WIND AT THE SURFACE
REMAINS MUDDLED...WITH MINS REMAINING CHALLENGING AS 12Z EURO SHOWS
TEENS FOR NORTHERN TWO THIRDS OF THE CWA. WILL FAVOR THE MIDDLE OF
THE ROAD...UPPER TEENS/LOWER 20S NORTH TO LOW/MID 20S SOUTH.

PLENTY OF MODEL TIMING ISSUES WITH ADDITIONAL UPPER WAVES
SUNDAY/SUNDAY NIGHT AND SUBSEQUENT STRENGTH OF SURFACE RIDGE DURING
THE DAYTIME HOURS OF SUNDAY BETWEEN 12Z CANADIAN/NAM/GFS/EURO.
VARIOUS PLACEMENT OF NARROW/ACTIVE FGEN ZONES THIS FAR OUT IS
PROBLEMATIC...AS OVERALL MOISTURE CONTENT IS LOW AND COVERAGE SHOULD
BE LIMITED. FAVOR A DRY FORECAST (SLIGHT CHANCE POPS) AT THIS TIME.
NO CHANGES MADE TO INHERITED TEMPS SUNDAY/SUNDAY NIGHT.

MAIN BRANCHES OF THE POLAR AND SUBTROPICAL JETS WILL MERGE OVER THE
EASTERN GREAT LAKES EARLY NEXT WEEK...LEADING TO CONFLUENT FLOW AND
DRY WEATHER OVER THE LOCAL AREA. WARM AIR ADVECTION ON
WEST/SOUTHWESTERLY LOW LEVEL FLOW WILL ALSO CONTINUE...COMBINED WITH
A GOOD DEAL OF MARCH SUN ALLOWING FOR A SLIGHT UPWARD ADJUSTMENT IN
TEMPERATURES MON-WED. IN FACT...WE MAY SEE HIGH TEMPS EXCEED DAILY
NORMALS FOR THE FIRST TIME IN ABOUT A MONTH AS HIGHS APPROACH 50F
TUE/WED. GFS 2M TEMPS LIKELY SUFFERING FROM A LOW BIAS DUE TO SNOW
COVER SO SIDED TOWARD WARMER MEX MOS VALUES.

MARINE...

SOUTHWEST FLOW PEAKING THIS AFTERNOON OVER LAKE HURON...AND WIND
SPEEDS LOOK TO BE GUSTING AROUND 30 KNOTS. LOW PRESSURE SLIDING
THROUGH THE NORTHERN GREAT LAKES TONIGHT INTO TOMORROW WILL ALLOW
FOR SLIGHTLY LIGHTER WIND REGIME...AS AIRMASS ALSO CONTINUES TO
MODIFY.  A RIDGE OF HIGH PRESSURE ARRIVING ON SUNDAY OVER THE
CENTRAL GREAT LAKES WILL ASSURE LIGHT WINDS FOR THE LAST HALF OF THE
WEEKEND.

&&

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

$$

AVIATION.....KURIMSKI
SHORT TERM...BT
LONG TERM....SF/DT
MARINE.......SF


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