Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS63 KDTX 210744
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
344 AM EDT TUE APR 21 2015

.SHORT TERM...TODAY AND TONIGHT

A DEEP LOW PRESSURE SYSTEM STACKED FROM THE SFC INTO THE UPPER
LEVELS WILL CONTINUE TO SIT OVER THE NORTHERN GREAT LAKES REGION
MOVING VERY LITTLE THROUGH THE SHORT TERM. THE LOW WILL STEER THE
NORTHERN STREAM OF THE JET DOWN AROUND MI TAKING IT SE THROUGH THE
UPPER MS VALLEY AND DOWN THROUGH THE OHIO VALLEY. MEANWHILE OVER SE
MI...CAA AND INCREASINGLY DRIER AIRMASS IN THE BL WILL ENCOURAGE THE
DEVELOPMENT OF A DEEP DIURNAL MIXED LAYER...UP TO NEAR 750MB. STRONG
LL LAPSE RATES INTO THE MID LEVELS WILL PROMOTE A CONVECTIVE MODE TO
ANY SHOWERS THAT DEVELOP IN THE COLD CYCLONIC FLOW. AIDING IN THE
SHOWER POTENTIAL WILL BE SEVERAL PIECES OF ENERGY ROTATING ABOUT THE
LOW.

BIGGEST CONCERN WITH THE SETUP TODAY WILL BE THE WIND. MODEL
SOUNDINGS SHOW A FAIRLY UNIFORM WIND FIELD THROUGHOUT THE MIXED
LAYER...AVERAGING 35-40 KNOTS ACROSS THE CWA. SOME 50 KNOT WINDS ARE
SHOWING UP AS WELL IN THE 650-750MB LAYER...BUT MAINLY FOR POINTS
SOUTH OF ABOUT M59. NAM AND GEMREG BOTH SHOW THE STRONGEST
FLOW...WIDEST SWATH OF 50+ KNOT LL JET FLOW...JUST SOUTH OF THE
MI/OH BORDER ACROSS IN/OH. WE ARE LOOKING AT TWO POSSIBLE SCENARIOS
FOR POTENTIAL WIND ADVISORY STRENGTH WIND GUSTS OVER THE AREA. THE
FIRST...AS MENTIONED BY THE PREVIOUS FORECASTER...WILL BE THE
CONVECTIVE SHOWERS BRINGING DOWN SOME HIGHER WIND GUSTS. WITH
WIDESPREAD 30-35 KNOT GUSTS FROM SYNOPTIC FORCING...AND TAKING INTO
ACCOUNT A FEW GUSTS ON MONDAY TAPPED THE 40 KNOT RANGE...CANNOT RULE
OUT A FEW HIGHER GUSTS WITHIN THESE STRONGER SHOWERS. THE SECOND
SCENARIO IS THAT THE LL JET IS NOT HELD SOUTH OF THE BORDER AND
BLEEDS INTO OUR SOUTHERN TIER OF COUNTIES OR TWO. NOT REALLY SOLD ON
EITHER AT THIS POINT ENOUGH TO ISSUE A WIND ADVISORY...BUT THE GRIDS
ALREADY HAVE FAIRLY STRONG WORDING FOR GUSTS SO THINK THAT HANDLES
THE SITUATION WELL. IF GUSTS EARLY SEEM TO BE OVERACHIEVING...A
SHORT FUSED ADVISORY MAY BE WARRANTED.

CAA WILL INCREASE OVERNIGHT AS THE TROUGH OF COLD AIR SHIFTS
EASTWARD. 850MB TEMPS WILL DROP FROM -2C TO AROUND -7C BY 12Z
WEDNESDAY. DRY AIR IN THE LOW LEVELS WILL AID IN EFFICIENT COOLING
SETUP WITH LOWS DIPPING INTO THE LOW 30S.

&&

.LONG TERM...

DEEP LAYER MOIST CYCLONIC FLOW WITHIN THE CYCLONE CENTERED NEAR THE
STRAITS WILL PERSIST THROUGH THURSDAY. EMBEDDED PV ANOMALY WILL
ROTATE ACROSS LOWER MICHIGAN LATE TUESDAY NIGHT/EARLY WEDNESDAY
FORCING A COLD FRONT THROUGH THE AREA PRIOR TO SUNRISE. COLD
ADVECTION WILL ENSURE ANOTHER DAY CHARACTERIZED BY DEEP BOUNDARY
LAYER MIXING PRODUCING PLENTY OF WIND AS H85 TEMPERATURES FALL TO -
8C BY WED AFTERNOON. STRATOCU DEVELOPMENT WILL BE PLENTIFUL AND, AS
A RESULT, FELT IT PRUDENT TO LEAN TOWARD THE COLDER GUIDANCE AS
INSOLATION WILL BE GREATLY LIMITED THROUGH THE DAY. HIGHS WILL
STRUGGLE TO 40F ALONG THE GLACIAL RIDGE WITH LOW TO MID 40S IN
DOWNSLOPE AREAS. WIDESPREAD WIND GUSTS THROUGH THE DAY WILL CONFINE
WIND CHILLS TO AROUND 30 DEGREES. THOUGH THE NAM REMAINS DRY, IT
WOULD CERTAINLY SEEM THAT DIURNAL SHOWERS WILL ONCE AGAIN BE
POSSIBLE. IT DOES APPEAR THAT THERE WILL BE A LACK OF FOCUSED
FORCING, BUT STILL HAVE TO RESPECT POTENTIAL GIVEN SYNOPTIC SCALE
ENVIRONMENT AND MODEST SBCAPE. MAINTAINED THE INHERITED CHC POP. IF
ANY MORE VIGOROUS SHOWERS DO DEVELOP WEDNESDAY, THE CORES WILL BE
CAPABLE OF PRODUCING SNOW GIVEN FREEZING LEVELS OF 1KFT AND SUB-
FREEZING SURFACE WET BULB TEMPS.

850MB TEMPERATURES ARE PROGGED TO BOTTOM OUT AT AN IMPRESSIVE -10C
DURING THE MORNING ON THURSDAY BEFORE UNDERGOING MODEST WARMING
THROUGH THE AFTERNOON AS AN EMBEDDED SHORTWAVE RIDGE PIVOTS THROUGH.
MINOR MID-LEVEL WARMING WILL MOST LIKELY BE RENDERED MOOT BY THE
VERY COLD THERMAL PROFILE THAT WILL BE IN PLACE FOR THE FIRST HALF
OF THE DAY, PARTICULARLY WITH EXPANSIVE DIURNAL STRATOCU EXPECTED
ONCE AGAIN. CURRENT FORECAST OF UPPER 40S MAY ULTIMATELY BE
OPTIMISTIC. MOISTURE QUALITY WILL DIMINISH AS THE LOW PULLS AWAY AND
THE GRADIENT WILL FINALLY EASE THURSDAY NIGHT SUPPORTING LOW
TEMPERATURES FALLING INTO AT LEAST THE UPPER 20S BY FRIDAY MORNING.

&&

.MARINE...

FRESH SOUTHWESTERLY WIND GUSTING AS HIGH AS 30 KNOTS WILL DEVELOP
TODAY AND PERSIST INTO THIS EVENING WITHIN ALL NEARSHORE ZONES.
SMALL CRAFT ADVISORIES THEREFORE REMAIN IN EFFECT. LIGHT TO MODERATE
WINDS WILL DOMINATE THE BULK OF THE OVERNIGHT HOURS BEFORE PICKING
UP AGAIN WEDNESDAY THROUGH THURSDAY NIGHT. ADDITIONAL SMALL CRAFT
ADVISORIES FOR THE NEARSHORE ZONES WILL BE LIKELY DURING THIS TIME.
IN ADDITION...COLD NORTHWEST FLOW WILL RESULT IN GUSTS TO NEAR GALES
THURSDAY INTO THURSDAY NIGHT. PERSISTENT OFFSHORE FETCH THROUGHOUT
THIS TIME WILL LIMIT SIGNIFICANT WAVE HEIGHTS TO 3 FEET OR LESS FOR
NEARSHORE AREAS.

&&

.AVIATION...ISSUED 1150 PM EDT MON APR 20 2015

CEILINGS HEIGHTS UPSTREAM HAVE BEEN LIFTING AS DRIER AIR PUSHES INTO
THE AREA IN THE WAKE OF THIS EVENINGS LIGHT RAIN SHOWERS. A POOL OF
DEEPER COLD AIR WILL OVERSPREAD SRN MI TONIGHT. THIS WILL LIFT
INVERSION BASES AND TOGETHER WITH THE DRIER AIR WILL MAINTAIN VFR
CEILINGS INTO THE AFTERNOON. WINDS SPEEDS WILL CONTINUE TO DECREASE
DURING THE EARLY MORNING UNDER CONTINUED COOLING IN THE BOUNDARY
LAYER. RAPID DEEPENING OF THE DAYTIME MIXED LAYER AIDED BY THE DEPTH
OF THE COLD POOL ALOFT WILL LEAD TO STRONG SW WINDS LATE IN THE
MORNING THROUGH TUES AFTERNOON. THE CURRENT SET OF TAFS ACCOUNTS FOR
SOME POTENTIAL FOR STRONG CONVECTIVE WIND GUSTS OUT OF AFTERNOON
SHOWERS ON TUES...WHICH STILL LOOKS REASONABLE.

FOR DTW...THERE IS A CLEARING TREND NOTED UPSTREAM WHICH WILL LIKELY
MAKE INROADS INTO METRO PRIOR TO DAYBREAK. WITH THE LIFTING
INVERSION HEIGHTS AND THIS DRIER AIR...LINGERING CEILINGS AT OR
BELOW 5000 FT SHOULD BE LIMITED. WINDS SHOULD INCREASE RATHER
DRAMATICALLY WITH THE ONSET OF DAYTIME HEATING...ROUGHLY AROUND 14Z.

//DTW THRESHOLD PROBABILITIES...

* LOW IN CEILINGS AT OR BELOW 5000 FT THIS MORNING AND AFTERNOON.

* LOW IN WIND GUSTS EXCEEDING CROSS WIND THRESHOLDS TUESDAY
  AFTERNOON.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LAKE HURON...SMALL CRAFT ADVISORY UNTIL 11 PM EDT THIS EVENING FOR LHZ421-422-
     441>443.

LAKE ST CLAIR...SMALL CRAFT ADVISORY UNTIL 11 PM EDT THIS EVENING FOR LCZ460.

MICHIGAN WATERS OF LAKE ERIE...SMALL CRAFT ADVISORY UNTIL 11 PM EDT THIS EVENING FOR LEZ444.

&&

$$

SHORT TERM...DRK
LONG TERM....JVC
MARINE.......JVC
AVIATION.....SC


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



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.