Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 241059
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
659 AM EDT FRI APR 24 2015


.AVIATION...

DEEP COLUMN RIDGING WILL SUPPORT VFR CONDITIONS ACROSS SOUTHEASTERN
MICHIGAN TODAY AND TONIGHT. WARM AIR ADVECTION ALOFT WILL EVENTUALLY
SUPPORT INCREASING HIGH-MID CLOUD BY TOMORROW MORNING. LIGHT
WESTERLY WINDS WILL EVENTUALLY TRANSITION TO EASTERLY IN RESPONSE TO
APPROACHING LOW PRESSURE.

//DTW THRESHOLD PROBABILITIES...

* NONE.

&&

.PREV DISCUSSION...ISSUED 413 AM EDT FRI APR 24 2015

SHORT TERM...TODAY AND TONIGHT

CONFLUENT UPPER LEVEL FLOW IN ADDITION TO THE STABLE GREAT LAKES
AGGREGATE WILL KEEP SURFACE HIGH PRESSURE CENTERED OVER SOUTHEASTERN
MICHIGAN TODAY. THE SURFACE ANTICYCLONE WILL BEGIN TO PULL AWAY THIS
EVENING...EVENTUALLY GETTING PUSHED EASTWARD LATE TONIGHT AS THE
PRESSURE GRADIENT INCREASES IN RESPONSE TO APPROACHING LOW PRESSURE.
IR IMAGERY IN ADDITION TO MODEL SOUNDINGS SUPPORT LITTLE TO NO SKY
FRACTION TO BEGIN THE DAY. WITH FULL SUNSHINE...MARKED IMPROVEMENT
IS EXPECTED IN THE TEMPERATURE DEPARTMENT WITH A STRONG CONSENSUS IN
GUIDANCE FOR HIGHS TODAY REACHING THE LOW TO MIDDLE 50S. A GOOD
SIGNAL EXISTS FOR A LAKE SHADOW ENCOMPASSING ALL OF THE THUMB DUE TO
NORTHWESTERLY FLOW. THIS WILL KEEP TEMPERATURES IN THE THUMB
COUNTIES IN THE 40S.

FLOW WILL SWITCH EASTERLY TONIGHT IN RESPONSE TO THE APPROACHING
SURFACE LOW. DRAINAGE FLOW OFF THE DEPARTING SURFACE HIGH WILL
PERSIST...KEEPING A STEADY SUPPLY OF LOW LEVEL DRY AIR FEEDING INTO
THE STATE. WHILE ISENTROPIC ASCENT WILL BE ON THE INCREASE....BEST
UPPER LEVEL FRONTAL SUPPORT WILL RESIDE VERY HIGH IN THE COLUMN (10
KFT AGL AND ABOVE). WILL MAINTAIN THE DRY FORECAST...WITH THE IDEA
THAT HIGH CLOUD WILL STEADILY LOWER INTO A MID CLOUD DECK BY THE END
OF THE PERIOD.

LONG TERM...SATURDAY THROUGH THURSDAY

THE SLOW EASTWARD PROGRESS OF THE ELONGATED UPPER LOW ROTATING OFF
THE COAST OF NRN NEW ENGLAND AND THE CANADIAN MARITIMES ON SATURDAY
WILL SUSTAIN A STRONGLY CONFLUENT MID LEVEL FLOW ACROSS THE GREAT
LAKES REGION. MEANWHILE...AN UPPER WAVE WILL LIFT FROM THE DESERT SW
INTO THE MID MS VALLEY ON SUNDAY. THE 00Z MODEL SUITE HAVE GENERALLY
TRENDED TOWARD THIS WAVE DEVELOPING INTO A SLIGHTLY DEEPER CUT OFF
LOW TONIGHT INTO SAT BEFORE RAPIDLY DAMPENING AS IT EMERGES INTO THE
MORE CONFLUENT FLOW ACROSS THE OHIO VALLEY/GREAT LAKES. THESE TRENDS
SUGGESTS THE UPPER WAVE WILL BE FORCED WELL SOUTH OF THE STATE.
WATER VAPOR IMAGERY CONFIRMS THAT THIS SYSTEM WILL HAVE A GOOD
DEGREE OF PACIFIC MOISTURE TO WORK WITH. MODEL SOLUTIONS AGREE THAT
THERE WILL BE A RATHER DYNAMIC FRONTAL RESPONSE ON THE NORTHERN EDGE
OF THIS SYSTEM. WITH THE ASSOCIATED SURFACE LOW EXPECTED TO TRACK
ACROSS THE SRN OHIO VALLEY AND STRONG HIGH PRESSURE TO THE NORTH OF
THE GREAT LAKES...A STRENGTHENING NE FLOW ON SATURDAY WILL SUSTAIN A
GOOD DEAL OF LOW LEVEL DRY AIR ACROSS LOWER MI. THIS IS ALSO LIKELY
TO CAUSE A SHARP BACK EDGE TO THE RAINFALL ON THE NORTH SIDE OF THIS
SYSTEM. THE GFS REMAINS RATHER BULLISH WITH QPF ACROSS FAR SRN LOWER
MI ON SATURDAY...BUT HAS SOMEWHAT OF A CONVECTIVE FEEDBACK LOOK TO
THE MODEL GENERATED FORCING. THE OTHER MODEL SOLUTIONS SUPPORT A
DRIER FORECAST ON SATURDAY...WHICH WILL WARRANT SOME REDUCTION IN
POPS. A CHANCE OF RAIN WILL STILL HOWEVER BE MAINTAINED ACROSS THE
SRN THIRD OF THE FORECAST AREA SAT AFTERNOON AND EVENING IN THE
EVENT THIS SYSTEM TRENDS BACK NORTHWARD.

LOW LEVEL N-NE WINDS WILL MAINTAIN COOL CONDITIONS /HIGHS IN THE
50S/ ACROSS THE FORECAST AREA THIS WEEKEND /NOT NEARLY AS COLD AS
THE LAST COUPLE OF DAYS/. TEMPS WILL HOWEVER AVERAGE SEVERAL DEGREES
COOLER NEAR LAKE HURON/SAGINAW BAY. THE MEDIUM RANGE MODELS SUITE
AGREE THAT THERE WILL BE SOME RETROGRESSION OF THE UPPER LOW OFF THE
EAST COAST OF CANADA WITH SHORT WAVE FEATURES ROTATING ACROSS THE
ERN GREAT LAKES SUNDAY INTO MONDAY. THIS WILL MAINTAIN THE COOL
NORTHERLY FLOW INTO MONDAY. DRY CONDITIONS LOOK TO HOLD THROUGH THE
END OF THE FORECAST PERIOD WITH SOME REBOUNDING HEIGHTS SUPPORTING A
MODEST WARMING TREND HEADING INTO THE MIDDLE OF NEXT WEEK.

MARINE...

A SURFACE TROUGH TO THE NORTH OF LAKE HURON AND HIGH PRESSURE
BUILDING IN ACROSS LOWER MI WILL SUSTAIN SOME RATHER GUSTY NORTHWEST
WINDS ACROSS THE OPEN WATERS OF LAKE HURON THIS MORNING AND
AFTERNOON. THE WINDS WILL DIMINISH TONIGHT INTO SATURDAY AS THIS
HIGH ADVANCES TO THE EASTERN GREAT LAKES. DEVELOPING LOW PRESSURE
FORECAST TO MOVE ACROSS THE OHIO VALLEY SATURDAY AND SATURDAY NIGHT
AND STRONG HIGH PRESSURE TO THE NORTH OF THE GREAT LAKES WILL
CAUSING STRENGTHENING N-NE WINDS SAT AFTERNOON AND NIGHT. THESE
WINDS WILL PERSIST INTO MONDAY BEFORE THE GRADIENT RELAXES. THERE IS
A POTENTIAL FOR SOME SMALL CRAFT ADVISORY CONDITIONS TO
DEVELOP...PARTICULARLY ON SAGINAW BAY AS THE NE FLOW FUNNELS INTO THE
BAY.

&&

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

$$

AVIATION.....CB
SHORT TERM...CB
LONG TERM....SC
MARINE.......SC


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