Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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000
FXUS63 KDTX 190755
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
355 AM EDT SUN APR 19 2015

.SHORT TERM...TODAY AND TONIGHT

LARGE EXPANSE OF QUIET WEATHER STRETCHING FROM MISSOURI INTO
KENTUCKY AT 07Z THIS MORNING AS THE FORCING ASSOCIATED WITH THE
STRONG LOW OVER THE WESTERN HIGH PLAINS HAS YET TO ARRIVE. A PARTIAL
COVERAGE OF SHOWERS IS NOTED INVOF MEMPHIS PADUCAH WITHIN THE
RESERVOIR OF HIGH MOISTURE CONTENT RESIDING OVER THE TENNESSEE AND
LOWER OHIO RIVER VALLEYS. THE SHORTWAVE DIGGING INTO THE NORTHERN
PLAINS WILL CAUSE THE STRONG CLOSED LOW OVER KS TO OPEN UP AND
TRANSLATE EAST OVER THE NEXT 24 HOURS. THE ARRIVAL OF DEEP LAYER
SOUTH/SOUTHEAST FLOW EAST OF THE MISSISSIPPI RIVER BY 18Z WILL
ADVECT THIS SLUG OF MOISTURE NORTHWARD. AT THE SAME TIME,
SUPERPOSITION OF INCREASINGLY FAVORABLE UPPER ATMOSPHERE DIVERGENCE
AND ISENTROPIC ASCENT WILL FORCE RAINFALL TO BLOSSOM OVER KY/IL/IN
THROUGHOUT THE MORNING.

SUPPORTED IN PART BY A COMPLEX OF SHORTWAVE ENERGY EMANATING FROM
CONVECTION OVER THE DEEP SOUTH, THIS ACTIVITY WILL LIFT TOWARD
LOWER MICHIGAN DURING THE DAY. INITIAL ARRIVAL OF MID-LEVEL MOISTURE
COINCIDENT WITH A NARROW BAND OF 290-295K ASCENT MAY SUPPORT A FEW
SHOWERS DURING THE LATE MORNING-MID AFTERNOON, BUT LACK OF
APPRECIABLE DEPTH/DURATION SUGGESTS MAINTAINING A CONSERVATIVE
APPROACH TO THE FORECAST THROUGH THIS PERIOD. AS SUCH, HELD MOST
PLACES AT 30-40 POP WITH MINIMAL QPF THROUGH AT LEAST 21Z. STIFF
EASTERLY FLOW WILL PUT A LID ON HIGH TEMPERATURES, BUT STILL EXPECT
MOST PLACES NOT NEAR LAKE SHORES TO APPROACH OR EXCEED 60 DEGREES,
ROUGHLY IN LINE WITH THE 00Z MAV GUIDANCE, AS PREDOMINANTLY DRY
CONDITIONS DOMINATE THROUGH LATE AFTERNOON.

PRIMARY CORRIDOR OF 305-310K ISENTROPIC ASCENT WILL LIFT FROM SOUTH
TO NORTH THROUGH THE FORECAST AREA 21Z-06Z THIS EVENING BENEATH
STRONGLY DIVERGENT FLOW ALOFT. LOW-LEVEL JET FORCING COULD BE
CONSIDERABLE DURING AT LEAST A PORTION OF THIS TIME FRAME AS A 60-
70KT LLJ IMPINGES ON THE EASTERN CWA. STRONG MOISTURE TRANSPORT
CENTERED WITHIN A DEEP 10KFT WARM CLOUD LAYER WILL LEND ITSELF TO
HIGHLY EFFICIENT HYDROMETEOR PRODUCTION AND SEVERAL HOURS OF
MODERATE RAIN WITH EMBEDDED HEAVY SHOWERS. FAVORED GUIDANCE
INDICATES A QPF MAXIMUM ALONG/EAST OF THE GLACIAL RIDGE WITH A SOLID
0.6" TO 0.8" AREAL AVERAGE ACROSS THE URBAN CORRIDORS OF METRO
DETROIT. URBAN AND SMALL STREAM FLOODING WILL BE POSSIBLE, LARGELY
DEPENDENT ON NATURE OF LLJ EVOLUTION IN ROUGHLY THE LOWER IMPACT
PERIOD OF 02-07Z FOR DETROIT AND SURROUNDING AREAS.

RAIN WILL DIMINISH IN COVERAGE AS THE WING OF STRONG ISENTROPIC AND
A SIZEABLE PERCENTAGE OF MID-LEVEL MOISTURE LIFTS NORTH. HOWEVER,
INCREASINGLY CYCLONIC FLOW WILL BE SPREADING INTO LOWER MICHIGAN AT
THIS TIME AND AN ABUNDANCE OF LOW-LEVEL MOISTURE WILL BE ACCOMPANIED
BY STEEPENING LAPSE RATES AS THE THERMAL RIDGE LIFTS NORTHEAST. AS A
RESULT, EXPECT A HEALTHY COVERAGE OF SHOWERS TO CONTINUE INTO THE
PREDAWN HOURS MONDAY MORNING. THE STRONG GRADIENT AND STEEP LAPSE
RATE ENVIRONMENT SHOULD ALSO CONTRIBUTE TO A PERIOD OF 25 TO
POSSIBLY 30 KT WIND GUSTS BEFORE THE STRONG WIND FIELD OVER SE
MICHIGAN DIMINISHES EARLY MONDAY.

&&

.LONG TERM...MONDAY THROUGH SATURDAY

AFTER A FAIRLY PLEASANT WEEK OR TWO IN SE MI THE LONG TERM TAKES A
TURN BACK TO COOL AND DREARY WITH SEVERAL OPPORTUNITIES FOR RAIN
SHOWERS...AND POSSIBLY A FEW SNOWFLAKES.

BY MONDAY THE REGION WILL BE BE ENGULFED BY A LARGE AREA OF SFC LOW
PRESSURE RESULTING FROM COMPLEX INTERACTION OF THE NORTHERN AND
SOUTHERN STREAMS OF THE JET IN ADDITION TO THE REMNANTS OF A CUTOFF
LOW THAT DRIFTED ACROSS THE CONUS OVER THE LAST FEW DAYS. THE
MID/UPPER LEVEL TROUGH WILL STILL BE OFF TO OUR WEST BY MONDAY
MORNING WITH THE FIRST STRONG SHORTWAVE LIFTING THROUGH THE NORTHERN
GREAT LAKES INTO ONTARIO. MODELS CONTINUE TO ADVERTISE ONE MORE
SOUTHERN STREAM SHORTWAVE LIFTING NNE ALONG A COLD FRONT PUSHING
EAST THROUGH SOUTHERN MI. THERE MAY BE A BIT OF A LULL IN THE PRECIP
EARLY MONDAY AS WE LOOK TO FALL IN A REGION OF SUBSIDENCE BETWEEN
THE TWO SHORTWAVES. THERE REMAINS LOWER CONFIDENCE IN TIMING OF ANY
OF THESE FEATURES AS MODELS HAVE BEEN CONTINUALLY SLOWING DOWN DUE
TO NOT HANDLING THE DEEPENING OF THE SYSTEM EFFECTIVELY YET. SO WILL
START OFF THE DAY WITH CHANCE POPS AND INCREASE LATER IN THE
AFTERNOON WHEN THE WAVE LOOKS TO LIFT THROUGH. THE TIMING IS
PRESENTING ADDITIONAL PROBLEMS REGARDING INSTABILITY AHEAD OF THE
COLD FRONT. CURRENTLY MODELS ARE SHOWING THE WARM SECTOR OF THE WAVE
JUST SKIRTING TO THE SOUTH OF SOUTHERN MI...YET THEY KEEP SOME HINT
OF INSTABILITY ALONG THE FRONT IN SE MI. IF THE SYSTEM CAN SLOW DOWN
A BIT MORE ALLOWING THE CENTER OF THE WAVE TO LIFT WEST OF THE
DETROIT METRO...WE MAY GET A LITTLE BOOST IN INSTABILITY FROM THE
WARM SECTOR CLIPPING THE AREA. MORAL OF THE STORY IS THAT WILL LEAVE
THE MENTION OF THUNDER IN THE FORECAST MONDAY AFTERNOON.
EXPECTATIONS ARE FOR RAIN SHOWERS ALONG THE FRONT WITH A FEW RUMBLES
OF THUNDER POSSIBLE.

THE REAL PUSH OF COLD AIR COMES WITH A COLD FRONT POSITIONED ALONG
THE MID LEVEL TROUGH AXIS PIVOTING THROUGH EARLY MONDAY NIGHT. THE
NORTHERN STREAM OF THE JET WILL BE ALIGNED NORTH TO SOUTH WHICH WILL
FUNNEL COLD AIR INTO THE REGION. WITH THE UPPER LOW STALLING OVER
THE AREA INTO THE WEEKEND...THIS CAA PATTERN WILL REMAIN IN PLACE
THROUGH THE END OF THE WEEK. 850MB TEMPS WILL FALL BELOW 0C MONDAY
NIGHT...DROPPING TO NEAR -10C BY THURSDAY NIGHT...BEFORE RIDGING
LOOKS TO DISPLACE THE LOW EASTWARD OVER THE WEEKEND. THE AIRMASS
WILL BE MUCH DRIER WITH PWATS AROUND 0.3 INCHES WHICH WILL RESULT IN
ONLY SOME CHANCE OR SLIGHT CHANCE POPS AS ADDITIONAL LOBES OF
VORTICITY ROTATE DOWN AROUND THE LOW THROUGH THE REGION THROUGH MID
WEEK. OTHERWISE LOOK FOR HIGH TEMPS TO STRUGGLE TO HIT 50 AT TIMES
WITH LOWS FALLING TO AROUND FREEZING.

&&

.MARINE...

HIGH PRESSURE CENTERED OVER THE ONTARIO/QUEBEC BORDER HAS SET UP
EASTERLY FLOW ACROSS THE REGION. THIS FLOW WILL INCREASE TODAY AS
LOW PRESSURE DEEPENS AND LIFTS TOWARD THE GREAT LAKES FROM THE
SOUTH. SMALL CRAFT ADVISORIES HAVE BEEN ISSUED FOR ALL NEARSHORE
ZONES AS GUSTY WINDS BUILD WAVE HEIGHTS ALONG THE SHORELINES NOW
INTO EARLY MONDAY. THOUGH SOME GUSTS MAY APPROACH GALE FORCE...THE
MARINE LAYER LOOKS TO BE FAIRLY STABLE WHICH WILL LIMIT THIS
POTENTIAL. AFTER STALLING A BIT OVER THE REGION TONIGHT...THE LOW
WILL LIFT NORTHWARD TO NEAR JAMES BAY BY MONDAY NIGHT. THIS WILL
ALLOW WINDS TO GRADUALLY RELAX THROUGH THE DAY MONDAY.

&&

.AVIATION...ISSUED 1151 PM EDT SAT APR 18 2015

DEPARTING SFC HIGH PRESSURE TO THE NORTHEAST WILL SUSTAIN A STRONG
EAST-NORTHEAST GRADIENT OVER SE MI THROUGH THE REST OF THE NIGHT.
WHILE NIGHTTIME COOLING WILL SUPPRESS THE DEGREE OF
GUSTINESS...SUSTAINED SPEEDS OF 8 TO 12 KNOTS SHOULD PERSIST THROUGH
DAYBREAK. LOW PRESSURE WILL APPROACH FROM THE SOUTH ON
SUNDAY...LEADING TO A STRENGTHENING OF THE EASTERLY WINDS AFTER
DAYBREAK. AN INFLUX OF GULF MOISTURE WITH THE ARRIVAL OF THIS LOW
PRESSURE SYSTEM WILL CAUSE RAIN AND LOWERING CEILINGS TO OVERSPREAD
THE SE MI TERMINALS LATE SUN AFTERNOON INTO THE EVENING.

FOR DTW...THE ONSET OF DAYTIME HEATING WILL STRENGTHEN WINDS AROUND
14Z /WITH GUSTS POSSIBLY TOPPING 20 KNOTS/. THE PUSH OF HIGHER LOW
LEVEL MOISTURE SHOULD ADVANCE INTO METRO IN THE 20 TO 22Z TIME
FRAME. THIS WILL MARK THE ARRIVAL OF RAIN AND ONSET OF LOWERING
CEILING HEIGHTS.

//DTW THRESHOLD PROBABILITIES...

* HIGH IN CEILINGS DROPPING BELOW 5000 FT AFTER 21Z SUNDAY.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LAKE HURON...SMALL CRAFT ADVISORY FROM 4 PM THIS AFTERNOON TO 2 PM EDT MONDAY
     FOR LHZ441>443.

     SMALL CRAFT ADVISORY FROM 10 PM THIS EVENING TO 2 PM EDT MONDAY FOR
     LHZ421-422.

LAKE ST CLAIR...SMALL CRAFT ADVISORY FROM 8 AM THIS MORNING TO 8 AM EDT MONDAY FOR
     LCZ460.

MICHIGAN WATERS OF LAKE ERIE...SMALL CRAFT ADVISORY UNTIL 4 AM EDT MONDAY FOR LEZ444.

&&

$$

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


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


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