Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 270140
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
940 PM EDT SUN OCT 26 2014

.UPDATE...

THE LEADING EDGE OF A MID LEVEL MOISTURE GRADIENT AND INSTABILITY
AXIS HAS LED TO SOME CONVECTION ACROSS ERN WISCONSIN THIS EVENING.
THIS MID LEVEL MOISTURE WILL ARRIVE INTO AT LEAST THE WESTERN HALF
OF THE FORECAST BY 11 OR 12Z. UPSTREAM SATELLITE IMAGERY WILL
SUPPORT AN INCREASE IN FCST CLOUD COVER LATE TONIGHT. PRIOR TO THE
ARRIVAL OF THESE CLOUDS...GOOD RADIATIONAL COOLING SHOULD STILL
DROP TEMPS DOWN INTO THE 30S OUTSIDE OF URBAN DETROIT. SO THE
CURRENT MIN TEMP FORECAST STILL LOOKS GOOD. THE DEGREE OF MID
LEVEL MOISTURE ADVECTION IN ADVANCE OF THE APPROACHING SFC WARM
FRONT AND STEEP MID LEVEL LAPSE RATES WILL SUPPORT RAISING THE
CHANCES FOR CONVECTION MONDAY MORNING ACROSS THE ENTIRE FORECAST
AREA /OUTSIDE OF THE THUMB WHERE THE MOISTURE ARRIVES LATER/.

&&

.AVIATION...ISSUED 700 PM EDT SUN OCT 26 2014

//DISCUSSION...

HIGH PRESSURE CENTERED OVER SE MI TONIGHT AND VERY DRY LOW LEVEL AIR
WILL MAINTAIN CLEAR SKIES BELOW 12K FT AND LIGHT WINDS THROUGH
DAYBREAK. A WARM FRONT WILL LIFT INTO SOUTHERN MICHIGAN ON
MONDAY...BRINGING SOME LOWERING CLOUDS BASES THROUGH THE DAY.

FOR DTW...CLOUDS SHOULD BEGIN TO INCREASE AROUND 11 OR 12Z AND
SHOULD REMAIN BASED ABOVE 6K FT THROUGH ROUGHLY 15Z BEFORE
ADDITIONAL MOISTURE IN THE LOW LEVELS ARRIVES.

//DTW THRESHOLD THREATS...

* NONE.

&&

.PREV DISCUSSION...ISSUED 318 PM EDT SUN OCT 26 2014

SHORT TERM...TONIGHT

CLEAR SKIES PREVAIL ACROSS THE CENTRAL UNITED STATES BENEATH
EXPANSIVE DOME OF HIGH PRESSURE, THE AXIS OF WHICH IS CENTERED OVER
THE MISSISSIPPI VALLEY. GRADUAL EASTWARD PROGRESSION WILL CONTINUE
INTO MONDAY MORNING WHICH WILL FORCE THE UPSTREAM SURFACE RIDGE AXIS
TO TRANSLATE ACROSS THE AREA DURING THE OVERNIGHT PERIOD. THE
COMBINATION OF CLEAR SKIES ALOFT, THE VERY DRY AIRMASS INDICATED ON
THIS MORNING`S 12Z DTX SOUNDING, AND A LIGHT SURFACE PRESSURE
GRADIENT WILL YIELD FAVORABLE RADIATING CONDITIONS. PARTIAL COVERAGE
OF CIRRUS SPILLING OVER THE RIDGE AXIS AND ADVECTING IN FROM THE SW
AND WARM ADVECTION ALOFT WILL BE THE ONLY INHIBITING FACTORS. LOW
TEMPERATURES IN THE UPPER 30S FOR MOST LOCATIONS, LOW 30S IN FAVORED
SPOTS FOR RADIATING, SEEMS LIKE A REASONABLE EXPECTATION.

LONG TERM...MONDAY THROUGH SUNDAY

SHORTWAVE RIDGING WILL EXPAND BACK OVER THE REGION FROM MONDAY INTO
MUCH OF TUESDAY IN ADVANCE OF THE NEXT APPROACHING NORTHERN STREAM
SHORTWAVE WHICH WILL BE CROSSING THE CANADIAN ROCKIES AND EMERGING
OVER THE NORTHERN CONUS PLAINS/SOUTHERN PRAIRIE PROVINCES DURING
EARLY IN THE WEEK. THIS WILL BRING MILDER READINGS BACK TO SOUTHERN
LOWER MIGHIGAN WITH TEMPERATURES RANGE FROM THE MID 60S TO LOWER 70S
FROM NORTH TO SOUTH ACROSS THE CWA MONDAY AND REACHING VERY CLOSE TO
THAT AGAIN ON TUESDAY...ALTHOUGH INCREASED CLOUD COVER AND SHOWER
AND THUNDERSTORM CHANCES WILL LIMIT SOLAR INSOLATION A FAIR AMOUNT
AS COMPARED TO MUCH OF THE AREA ON MONDAY.

THERE WILL BE A CHANCE OF SCATTERED SHOWERS MONDAY...PARTICULARLY
OVER THE NORTHERN CWA AS LIFT ALONG AN ADVANCING WARM FRONT SHIFTS
THROUGH THE AREA. RAIN CHANCES WILL THEN INCREASE FROM MONDAY NIGHT
INTO TUESDAY AS THE AFOREMENTIONED SHORTWAVE DEEPENS AND SHIFTS INTO
THE UPPER MISSISSIPPI VALLEY/NORTHERN GREAT LAKES. AS THE UPPER
TROUGH AXIS SHIFTS EAST INTO THE AREA...MOISTURE WILL FUNNEL NORTH
INTO THE AREA AND FORCING WILL INCREASE AS A COLD FRONT WRAPS EAST
INTO AREA AROUND THE BASE OF THE DEVELOPING UPPER LOW PRESSURE
SYSTEM TO THE NORTH/NORTHWEST. INSTABILITY WITHIN THIS EXPANDING
THETA-E RIDGE IN ADVANCE OF THE SYSTEM SHOULD BE SUFFICIENT TO
PRODUCE SCATTERED STORMS ON TUESDAY...WITH A FEW STRONGER STORMS
POSSIBLE BEFORE ACTIVITY SHIFTS EAST BY LATE AFTERNOON/EARLY
EVENING.

MUCH COOLER AIR WILL SURGE INTO THE AREA TUESDAY NIGHT IN THE WAKE
OF THE PASSING COLD FRONT...BRINGING LOW TEMPERATURES DOWN TO AROUND
40 DEGREES ACROSS THE AREA...UPPER 30S SAGINAW VALLEY TO LOWER 40S
DETROIT METRO SOUTHWARD. THIS WILL BE SOME 15-20F COOLER THAN THE
MILD READING EXPECTED MONDAY NIGHT WHEN MOST OF THE CWA REMAINS IN
THE MID/UPPER 50S.

THE LAST 3 DAYS OF OCTOBER WILL TREND MUCH COOLER...AND SHOULD
RESULT IN THE MONTH ENDING AROUND 1 DEGREE LOWER THAN NORMAL. A
PERSISTENT FEATURE IN THE EXTENDED MODELS CONTINUES TO BE A SHARP
500 MB TROUGH DUG-IN BY A 125KT JET DIVING SOUTHEAST ACROSS MANITOBA
TO WISCONSIN ON HALLOWEEN. LEFT EXIT JET DYNAMICS WILL ASSIST
CYCLONE DEVELOPMENT AND PRECIPITATION DURING THE DAY FRIDAY...THEN
BRISK WINDS WILL FOLLOW TO BRING APPARENT TEMPS DOWN TO NEAR 30
DEGREES AT 8PM AND 20 DEGREES BY SATURDAY MORNING.

MARINE...

SMALL CRAFT ADVISORIES WILL BE ALLOWED TO EXPIRE AS WEST/NORTHWEST
FLOW CONTINUES TO SUBSIDE IN DECREASING PRESSURE GRADIENT. WHILE
WAVES WILL TAKE LONGER TO SUBSIDE...NEAR SHORE WATERS SHOULD HAVE
WAVES DOWN TO 2 TO 4 FEET OR LESS FOR THE MOST PART BY LATE THIS
AFTERNOON AND EARLY THIS EVENING.

RELATIVELY CALM CONDITIONS WILL THEN SET UP TONIGHT INTO MONDAY
BEFORE SOUTHERLY FLOW INCREASES MONDAY NIGHT INTO TUESDAY IN ADVANCE
OF AN APPROACHING COLD FRONT. WINDS WILL THEN VEER TO THE WEST WITH
THE PASSAGE OF THIS FRONT LATE TUESDAY INTO TUESDAY NIGHT. AT THIS
TIME...IT APPEARS THE LOW PRESSURE SYSTEM DRIVING THIS FRONT WILL
PASS FAR ENOUGH NORTH OF THE AREA TO NECESSITATE HEADLINES FOR LAKE
HURON. THAT SAID...WIND GUSTS TO 20 KNOTS WILL BECOME COMMON DURING
THIS TIME FRAME WITH INCREASINGLY UNSETTLED WEATHER AS SHOWERS AND A
FEW THUNDERSTORMS EXPAND ACROSS THE AREA FROM MONDAY INTO TUESDAY.

&&

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

$$

UPDATE.......SC
AVIATION.....SC
SHORT TERM...JVC
LONG TERM....DG/MM
MARINE.......DG


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



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