Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 231540
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
1040 AM EST MON FEB 23 2015

.UPDATE...

PLANNING ON ALLOWING WIND CHILL WARNINGS/ADVISORIES EXPIRE AT NOON
AS FORECASTED. FULL SUNSHINE HAS ALLOWED TEMPS TO CLIMB TO ZERO
ACROSS MOST SPOTS...WITH HIGHS STILL EXPECTED TO TOP OUT AROUND
10 DEGREES...WITH LITTLE TO NO WIND TO SPEAK OF.
FOR TONIGHT...BASED ON THE EXTREMELY DRY AIRMASS...SEE 12Z DTX
SOUNDING/CURRENT DEW PTS...FAVORING TEMPS A BIT COLDER TONIGHT
THAN PREVIOUSELY FORECASTED...BUT SUSPECT WINDS WILL BE A TOUCH
LIGHTER AS WE DECOUPLE OR COME CLOSE THIS EVENING. WIND CHILLS
ACROSS THE AREA CERTAINTLY WILL BE AROUND 15 BELOW ZERO FOR SHORT
PERIOD TONIGHT AS WINDS BEGIN TO INCREASE LATE TONIGHT WITH
INCREASING SOUTHWEST FLOW...BUT NOT SURE IF IT REQUIRES A WIND
CHILL ADVISORY FOR THE MARINGAL WIND CHILLS. ALSO...WANT TO SEE
WHAT KIND OF PROGESS THE LAKE MICHIGAN CLOUDS MAKE DURING THE
AFTERNOON AS WINDS BACK AROUND TO WEST-SOUTHWEST.

&&

.AVIATION...ISSUED 648 AM EST MON FEB 23 2015

AVIATION CONDITIONS WILL START OUT CLEAR AND COLD WITH A LIGHT
NORTHERLY WIND THAT WILL BACK TOWARD THE WEST AND SOUTHWEST DURING
THE DAY. THIS WILL OCCUR AS HIGH PRESSURE SLIDES INTO THE OHIO
VALLEY AND AS THE NEXT LOW PRESSURE SYSTEM APPROACHES FROM CENTRAL
CANADA. THE WESTERLY LOW LEVEL FLOW WILL BRING PATCHES OF STRATOCU
EASTWARD FROM LAKE MICHIGAN DURING THE AFTERNOON. TERMINALS FROM THE
TRI CITIES DOWN TO FLINT AND PONTIAC HAVE THE BEST CHANCE OF A
CEILING THAT WILL BE BORDERLINE MVFR/VFR BASED ON SHORELINE
OBSERVATIONS DURING THE MORNING. SOUTHWEST WIND WILL THEN PICK UP
SPEED TONIGHT BUT BRING AIR IN FROM THE CENTRAL PLAINS WHERE IT IS
DRY ENOUGH TO CUT OFF THE FLOW OF LAKE CLOUDS DURING THE EVENING.
VFR WILL THEN CONSIST OF THICKENING HIGH CLOUDS DURING THE REST OF
THE NIGHT THROUGH TUESDAY MORNING.

//DTW THRESHOLD PROBABILITIES...

* LOW FOR CEILING BELOW 5000 FT DURING THE AFTERNOON.

&&

.PREV DISCUSSION...ISSUED 353 AM EST MON FEB 23 2015

SHORT TERM... TODAY AND TONIGHT

THE WIND CHILL HEADLINES REMAIN IN EFFECT THROUGH THE MORNING AS THE
LATEST ARCTIC AIR MASS SETTLES OVER LOWER MICHIGAN. TRENDS IN EARLY
MORNING SURFACE ANALYSIS INDICATE ACTUAL TEMPERATURE WILL MAKE A RUN
TOWARD -15 IN THE TRI CITIES AND NORTHERN THUMB BEFORE SUNRISE. THE
WIND WILL BE LIGHTER THERE BUT A SPEED OF JUST 5 MPH WILL PUSH WIND
CHILL DOWN AROUND -25 UNTIL ABOUT MID MORNING. FARTHER SOUTH...
ACTUAL TEMPERATURES WILL BE AROUND -5 BUT A STRONGER WIND WILL
SUPPORT WIND CHILL OF -15 TO -20 BEFORE READINGS REBOUND MID TO LATE
MORNING AS WELL. THE TEMPERATURE REBOUND WILL GAIN SOME TRACTION
THANKS TO FULL SUN THAT WILL LAST THROUGH THE MORNING INTO EARLY
AFTERNOON...BUT EXPECT READINGS WILL STRUGGLE TO REACH DOUBLE DIGITS
ABOVE ZERO BEFORE BACKING LOW LEVEL FLOW DIRECTS SOME STRATOCU
EASTWARD FROM LAKE MICHIGAN. A GENERAL INCREASING CLOUD TREND WILL
LIKELY RESULT IN BROKEN COVERAGE IN THE TRI CITIES AND NORTHERN
THUMB DURING THE AFTERNOON WITH SMALLER POCKETS OR SHORTER DURATION
OF COVERAGE AVERAGING PARTLY SUNNY CONDITIONS TOWARD THE OHIO
BORDER.

THE EVENING TEMPERATURE TREND WILL BE VERY SENSITIVE TO THE
REMAINING CLOUD COVERAGE IN THE NORTH AND THE DURATION OF WIND
DECOUPLING TOWARD THE OHIO BORDER. MODEL EVIDENCE SUPPORTS
MAINTAINING LOW SINGLE DIGIT READINGS OVER THE TRI CITIES. THIS IS
WHERE LINGERING STRATOCU AND THICKENING HIGH CLOUDS WILL COMBINE
WITH BETTER ESTABLISHED SOUTHWEST WIND TO BUOY TEMPERATURES. FARTHER
SOUTH...THE OPPOSITE WILL ALLOW READINGS TO DROP A COUPLE DEGREES
BELOW ZERO BEFORE THE INCREASING WIND STARTS A TEMPERATURES
RECOVERY. ALL LOCATIONS WILL HAVE TEMPERATURES RISE OVERNIGHT AS
SOUTHWEST WIND INCREASES INTO THE 10 TO 20 MPH RANGE. THAT SHOULD
GET ACTUAL TEMPERATURES INTO THE LOWER SINGLE DIGITS BY SUNRISE
TUESDAY BUT WITH WIND CHILL RUNNING NEAR -15 DURING THE TRANSITION.

LONG TERM...TUESDAY THROUGH SUNDAY

ENERGY FROM NEAR THE NORTH POLE WILL DROP INTO THE GREAT LAKES ON
TUESDAY. THIS WILL KICK AN AREA OF SURFACE LOW PRESSURE ACROSS
NORTHERN ONTARIO...WITH SURFACE TROUGHING EXTENDING DOWN INTO
MICHIGAN TUESDAY INTO TUESDAY NIGHT. AHEAD OF THE TROUGH AND
APPROACHING COLD FRONT...THETA-E ADVECTION AND ISENTROPIC ASCENT
(BEST AT 280K) WILL COMBINE WITH LEFT EXIT REGION FORCING TO PROVIDE
A CHANCE FOR SNOW SHOWERS...ESPECIALLY BY AFTERNOON/EVENING AS LAPSE
RATES STEEPEN. SNOW SHOWERS LOOK LIKELY DURING THE LATER PART OF THE
DAY...AND THEN THROUGH THE EARLY PART OF THE NIGHT AS THE COLD FRONT
DROPS THROUGH. THERE IS ALSO SOME POTENTIAL FOR MOISTURE TO GET
PULLED OFF LAKE MICHIGAN IN WESTERLY FLOW JUST AHEAD OF THE FRONT.
OVERALL...STILL DEPICTING A HIGH POP/LOW QPF SCENARIO WITH LESS THAN
INCH OF SNOW ACCUMULATION SOUTH OF I-69...AND NO MORE THAN 2 INCHES
NORTH OF THERE.

A FEW OTHER ISSUES ON TUESDAY TO DISCUSS. IMPRESSIVE WIND FIELD WILL
SETTLE IN OVER THE AREA WITH 35-40 KNOT WIND CORE SHOWN TO BE WELL
PLACED WITHIN THE MIXED LAYER ON BOTH GFS AND NAM FORECAST
SOUNDINGS. THIS SHOULD TRANSLATE TO 40 MPH GUSTS AT THE
SURFACE...AND WILL HAVE TO WATCH POTENTIAL FOR HIGHER GUSTS. GUSTY
WINDS COULD ALSO CAUSE A PROBLEM WITH BLOWING AND DRIFTING SNOW.
TEMPERATURES WILL ALSO BE MILDER ON TUESDAY AHEAD OF THE FRONT. WIND
CHILLS ARE EXPECTED TO REMAIN IN THE SINGLE DIGITS HOWEVER DESPITE
ACTUAL HIGH TEMPS CRACKING THE UPPER TEENS TO LOW 20S. WARM AIR
ADVECTION THROUGH THE EVENING SHOULD ALLOW TEMPERATURES TO LEVEL OFF
OR EVEN RISE A LITTLE...BEFORE THE ARCTIC FRONT SWEEPS DOWN
OVERNIGHT AND CRASHES TEMPERATURES BACK DOWN INTO THE SINGLE DIGITS.
THE COLD TEMPERATURES COMBINED WITH WINDS OVERNIGHT WILL AGAIN LEAD
TO WIND CHILL CONCERNS...WITH VALUES FALLING WELL BELOW ZERO AGAIN
NORTH OF I-69.

STRONG DOME OF HIGH PRESSURE WILL BUILD INTO THE AREA BEHIND THE
FRONT...SLOWLY SHIFTING OVERHEAD BY FRIDAY. THIS WILL KEEP THE
WEATHER QUIET BUT ALSO KEEP COLD AIR LOCKED IN PLACE AND PROVIDE
WELL BELOW NORMAL TEMPERATURES. SUB-ZERO LOWS ARE EXPECTED THURSDAY
AND FRIDAY NIGHT...AND WIND CHILLS WILL BE A CONCERN ONCE AGAIN.

MARINE...

GUSTY NORTHWEST WINDS WILL SUBSIDE BY LATE THIS MORNING AS HIGH
PRESSURE EXPANDS INTO THE CENTRAL GREAT LAKES. WINDS WILL THEN TURN
SOUTHERLY AND INCREASE IN STRENGTH THIS EVENING AND OVERNIGHT AS A
LOW PRESSURE SYSTEM TRACKS ACROSS NORTHERN ONTARIO. WINDS LOOK TO
REACH GALE FORCE BY TUESDAY MORNING ACROSS MUCH OF LAKE HURON AS A
STRONG WIND FIELD PUSHES UP INTO THE AREA AHEAD OF THE LOW. A GALE
WARNING IS NOW IN EFFECT FOR MUCH OF LAKE HURON...INCLUDING SAGINAW
BAY...WITH WIND GUSTS TO 45 KNOTS EXPECTED. BRIEF GUSTS TO GALE
FORCE MAY ALSO OCCUR OVER LAKE ST CLAIR AND WESTERN LAKE
ERIE...HOWEVER THE DURATION DOES NOT LOOK LONG ENOUGH TO WARRANT A
GALE HEADLINE. ANOTHER ARCTIC COLD FRONT WILL SWEEP DOWN ACROSS THE
CENTRAL GREAT LAKES TUESDAY NIGHT...FLIPPING WINDS TO THE NORTHWEST.
THESE WINDS WILL REMAIN ELEVATED...BUT AT THIS TIME...GUSTS LOOK TO
REMAIN AROUND 30 KNOTS OVER LAKE HURON.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...WIND CHILL ADVISORY UNTIL NOON EST TODAY FOR MIZ047-048-053-060-
     068>070-075-076-082-083.

     WIND CHILL WARNING UNTIL NOON EST TODAY FOR MIZ049-054-055-061>063.

LAKE HURON...GALE WARNING FROM 4 AM TO 7 PM EST TUESDAY FOR LHZ362-363-421-422-
     441-462>464.

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

$$

UPDATE.......SF
AVIATION.....BT
SHORT TERM...BT
LONG TERM....HLO
MARINE.......HLO


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