Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

Home | Current Version | Previous Version | Graphics & Text | 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 200151
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
951 PM EDT SUN APR 19 2015

.UPDATE...

THE REGION OF RAIN ASSOCIATED WITH A GOOD MOISTURE SURGE WITHIN A
WARM AIR ADVECTION REGIME HAS BEEN LIFTING NORTHWARD RATHER
RAPIDLY ACROSS THE FORECAST AREA. AS OF 945 PM...THE BACK EDGE OF
THE STEADIER RAINFALL WAS ALREADY LIFTING ACROSS MONROE/LENAWEE
COUNTIES. AT THIS PACE...THE WIDESPREAD RAIN SHOULD LIFT NORTH OF
THE FORECAST AREA BY 2 AM. UPSTREAM RADAR DOES HOWEVER SHOW
ADDITIONAL SHOWERS AND FEW THUNDERSTORMS ACROSS SRN INDIANA AND
OHIO...LIFTING NORTHWARD. THESE SHOWERS ARE BEING AIDED BY LIFT
ALONG A MID LEVEL SHORT WAVE FEATURE AND ARE ALONG A SECONDARY LOW
LEVEL THETA E PLUME ALIGNED ALONG A SURFACE WARM FRONT. THESE
FEATURES WILL LIFT NORTHWARD INTO SE MI OVERNIGHT AND WILL STILL
SUPPORT SCT TO NMRS POPS. SO IN SHORT...THE CURRENT FORECAST
WHICH FEATURES CATEGORICAL RAIN TRANSITIONING TO SCT-NMRS SHOWERS
OVERNIGHT STILL LOOKS IN LINE. A UPDATE WILL BE ISSUED LATER THIS
EVENING SIMPLY TO ADJUST TIMING. IN LIGHT OF CURRENT RADAR
RAINFALL ESTIMATES...FORECAST QPF MAY BE TAKEN DOWN A LITTLE AS
WELL.

&&

.AVIATION...ISSUED 700 PM EDT SUN APR 19 2015

RAIN WILL CONTINUE EXPANDING ACROSS SE MI AND WILL OVERSPREAD THE
TERMINALS BY 00Z. EASTERLY WINDS HAVE BEEN SUSTAINING LOW LEVEL DRY
AIR WHICH IN TURN HAS HELD CEILINGS UP. A SUBSTANTIAL AMOUNT OF
MOISTURE ADVECTION DURING THE EVENING AND OVERNIGHT ALONG WITH
INCREASING INTENSITY OF RAINFALL WILL HOWEVER LEAD TO A STEADY
LOWERING TREND IN CEILINGS THIS EVENING. IFR CONDITIONS ARE EXPECT
TO DEVELOP EITHER LATE THIS EVENING OR EARLY IN THE OVERNIGHT
PERIOD. UPSTREAM OBSERVATIONS DO HOWEVER SUGGEST THERE IS LIKELY TO
BE A GOOD DEAL OF VARIABILITY IN CEILING HEIGHTS. THIS RAIN AND
MOISTURE THAT IS LIFTING ACROSS THE AREA IS ASSOCIATED WITH A LOW
PRESSURE SYSTEM OVER INDIANA. THIS LOW WILL LIFT ACROSS WESTERN
LOWER MI TONIGHT. EVEN WITH THE RAINFALL...THE SFC GRADIENT SHOULD
SUSTAIN SOME DEGREE OF GUSTINESS TO THE WINDS TONIGHT /POSSIBLY
TOPPING 20 KNOTS AT TIMES/. A WARM FRONT ASSOCIATED WITH THE SFC LOW
IS FORECAST TO LIFT NORTH ACROSS SE MI BETWEEN 09Z AND 12Z. THE
PASSAGE OF THIS FRONT WILL VEER WINDS TO THE SOUTH AND MAY ACTUALLY
LEAD TO SOME LIFTING OF CLOUD BASES AS THE WARM SECTOR NUDGES INTO
THE AREA.

FOR DTW...THE PEAK IN RAINFALL INTENSITY IS EXPECTED TO OCCUR
BETWEEN 02Z AND 05Z...WHERE SOME PERIODIC HEAVY RAINFALL IS
POSSIBLE. WHILE CEILING HEIGHTS WILL FLUCTUATE A GOOD DEAL...THE
OVERALL TREND HEADING INTO THE OVERNIGHT WILL BE FOR THE DEVELOPMENT
OF IFR CONDITIONS.

//DTW THRESHOLD PROBABILITIES...

* HIGH IN CIGS AOB 5KFT TONIGHT AND MONDAY.

* LOW IN THUNDERSTORMS TONIGHT AND MONDAY.

&&

.PREV DISCUSSION...ISSUED 356 PM EDT SUN APR 19 2015

SHORT TERM...TONIGHT

THE ARC OF SHOWER ACTIVITY FORCED ON AN INITIAL SURGE/GRADIENT OF
850-700MB MOISTURE HAS STRUGGLED FROM A VIGOR PERSPECTIVE DUE TO A
LACK OF INSTABILITY. WITH SHOWERS WORKING UP THE FRONTAL SLOPE AS IT
TRACKS NORTHWARD...EXPECT THE WEAK NATURE TO CONTINUE.

THE MAIN BAND OF SYNOPTIC FORCING AND WIDESPREAD RAIN ACTIVITY WILL
LIFT ACROSS THE OHIO AND MICHIGAN BORDER AROUND 21Z. REGIONAL MOSAIC
AS OF 19Z... SHOWS THE MIDLEVELS SATURATING SOUTH OF TOLEDO. REALLY
A TREMENDOUS AMOUNT OF SYNOPTIC SCALE SUPPORT FOR LIFT AND
PRECIPITATION GENERATION TONIGHT AS SOUTHEASTERN MICHIGAN REMAINS
FAVORABLY POSITIONED AHEAD OF A HIGH AMPLITUDE WARM SECTOR
STRUCTURE AND OPTIMAL WARM AIR ADVECTION. EVERYTHING APPEARS TO BE
LINING UP FROM A FORCING STANDPOINT FOR A FAVORABLE PERIOD OF
WIDESPREAD RAIN INCLUDING A POTENTIAL FOR HEAVY RAINFALL.
SPECIFICALLY...LARGE BULLSEYE OF 1000-500MB HEIGHT FALLS...LINKAGE
OF RIGHT NOSE OF LOW LEVEL JET AXIS WITH RIGHT ENTRANCE REGION
DYNAMICS ALOFT...AND A DIRECT HIT FROM A SECONDARY VORTICITY
MAXIMUM. NWP SUPPORTS THIS SECONDARY VORTICITY MAXIMUM BECOMING
ORGANIZED/STRENGTHENING NEAR LOUISVILLE NOW AND LIFTING INTO FAR
SOUTHEASTERN MICHIGAN BETWEEN 00-03Z. NAM REALLY BITES ON THIS
FEATURE SHOWING DEPICTIONS OF A PSEUDO SHARS TYPE RESPONSE AND
HIGH AMOUNTS OF 3HR QPF. BROAD NATIONAL MOSAIC OF REFLECTIVITY
ALONG WITH SATELLITE IMAGERY OF CLEARING/DESTABILIZING STRAIGHT
INTO CENTRAL KENTUCKY SUPPORTS THIS STRONG SOLUTION OF THE
SECONDARY VORTICITY MAXIMUM. THUS...THE EARLIER FORECAST OF
FORECASTING QPF AMOUNTS OF UPWARDS OF 1.00 INCH FOR FAR
SOUTHEASTERN MICHIGAN INCLUDING THE DETROIT METRO APPEARS
REASONABLE. THERE AT LEAST REMAINS SOME POTENTIAL THAT THIS DRY
AIR/SLOT COULD WORK NORTHWARD AT A CRITICAL TRAJECTORY AND CAUSE
HEAVY PRECIPITATION TO DEFLECT AWAY FROM THE CWA. CONFIDENCE IN
PROJECTING THAT OUT IS LOW. WHILE FORECASTED QPF AMOUNTS ARE
RELATIVELY HIGH FROM AN EVENT STANDPOINT...THE STEADY NORTHWARD
PROGRESSION OF SHOWERS/EMBEDDED THUNDER WILL LIMIT THE CONCERN FOR
FLOODING.

LONG TERM...

STRONG LOW PRESSURE WILL CONTINUE TO DEEPEN AS IT LIFTS NORTHWARD
THROUGH NORTHERN LOWER MICHIGAN INTO ONTARIO ON MONDAY. MODELS HAVE
TRENDED SLIGHTLY SLOWLY AND FURTHER WEST WITH THE TRACK OF THIS
SYSTEM...AND THIS WILL MOSTLY LIKELY HAVE SOME NOTABLE IMPLICATIONS
TO THE GOING FORECAST. AS SUCH...HAVE MADE A FEW ADJUSTMENTS FOR
THIS PACKAGE.

THE "NEW" CONSENSUS TRACK FORECAST WILL ESSENTIALLY DELAY THE COLD
FRONTAL PASSAGE THROUGH THE AREA UNTIL LATE AFTERNOON AND ALLOW FOR
TEMPERATURES TO CLIMB WELL INTO THE 60S OVER A GOOD PORTION OF THE
AREA. THIS...IN TURN...WILL ALLOW FOR SOME DESTABILIZATION AS SBCAPE
VALUES CLIMB TO AROUND 500 J/KG BY AFTERNOON. THIS SHOULD ALLOW FOR
MORE VIGOROUS CONVECTION ALONG THE COLD FRONT WITH THE POTENTIAL FOR
HAIL INCREASING AS FREEZING LEVELS DROP BELOW 7000-8000 FEET AS COLD
AIR WRAP AROUND THE UPPER CIRCULATION.

IN ADDITION...THIS ACTIVITY WILL LIKELY PRODUCE SOME GUSTY WINDS AS
DEEP SWATH OF 35 TO 40 KT SOUTHWEST FLOW OVERSPREADS THE AREA. EVEN
OUTSIDE OF STORMS...WIND GUSTS WILL LIKELY REACH 35 MPH AT TIMES BY
AFTERNOON AND HAVE UPPED THE OVERALL FORECAST WINDS A FAIR AMOUNT.
WHILE WIDESPREAD STRONG STORMS ARE PROBABLY NOT TOO LIKELY...A FEW
WILL CERTAINLY BECOME A BIT ROBUST AS FORCING ALONG THE COLD FRONT
HELPS FOCUS THE MARGINAL INSTABILITY THAT IS ABLE TO BUILD OVER
PARTS OF THE AREA.

CONDITIONS WILL QUIET FROM MID EVENING INTO TUESDAY AS THE LOW LIFTS
TO NEAR JAMES BAY AND STALLS. THAT SAID...CONDITIONS WILL REMAIN
RATHER UNSETTLED INTO THE TUESDAY AND TUESDAY NIGHT PERIOD AS THIS
LOW ONLY GRADUALLY WEAKENS. EXPECT COOLER TEMPERATURES AND CONTINUE
GUSTY WINDS WITH SCATTERED RAIN SHOWERS DOTTING THE REGION...MAINLY
IN THE TUESDAY AFTERNOON PERIOD DURING THE DIURNAL TEMPERATURE AND
INSTABILITY MAX. DOWNSLOPING WEST/SOUTHWEST FLOW SHOULD ALLOW METRO
DETROIT AND SURROUNDING AREAS TO CLIMB INTO THE MID 50S DESPITE THE
MUCH COLDER AIRMASS...BUT STILL EXPECT LOWS WELL INTO THE 30S BY
TUESDAY NIGHT AS THE COLD AIRMASS DEEPENS OVER THE AREA.

EXTENDED FORECAST STARTING WEDNESDAY AND INTO NEXT WEEKEND WILL BE
RELATIVELY QUIET AS FAR AS PRECIPITATION GOES WITH BELOW NORMAL
TEMPERATURES.  COOLER AIR WILL CONTINUE TO FILTER INTO THE REGION AS
THE GREAT LAKES RESIDES IN THE PERSISTENT LONGWAVE TROUGHING.  WHILE
THERE WILL BE SLIGHT PRECIPITATION CHANCES WHILE THE REGION RESIDES
IN THE TROUGH...THE CAVEAT IS THE LACK OF MOISTURE THAT WILL BE
AVAILABLE.  RIDGING DOES NOT LOOK TO START BUILDING INTO THE WESTERN
GREAT LAKES REGION UNTIL THE END OF THE FORECAST PERIOD.

MARINE...

EAST FLOW WILL GRADUALLY BECOME SOUTHEAST TONIGHT AS DEEPENING LOW
PRESSURE PUSHES A WARM FRONT THROUGH THE AREA. DURING THIS TIME
FRAME...EXPECT STEADILY INCREASING WIND SPEEDS WHICH WILL ALLOW
WAVES TO BUILD. AS THIS LOW PASSES INTO THE NORTHERN GREAT LAKES
MONDAY...WINDS REMAIN GUSTY AND VEER TO THE SOUTH AND THEN SOUTHWEST
AS A COLD FRONT SWEEPS AROUND THE BASE OF THE EXITING LOW PRESSURE.
SMALL CRAFT ADVISORIES WILL CONTINUE INTO MONDAY. WHILE A FEW GUSTS
MAY APPROACH GALE FORCE...THE MARINE LAYER LOOKS TO BE FAIRLY STABLE
WHICH WILL LIMIT THIS POTENTIAL. WINDS WILL SUBSIDE TO SOME EXTENT
FROM MONDAY NIGHT INTO TUESDAY AS THE LOW STALLS NEAR JAMES BAY AND
BEGINS TO SLOWLY WEAKEN.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LAKE HURON...SMALL CRAFT ADVISORY UNTIL 8 PM EDT MONDAY FOR LHZ441>443.

     SMALL CRAFT ADVISORY UNTIL 8 PM EDT MONDAY FOR LHZ421-422.

LAKE ST CLAIR...SMALL CRAFT ADVISORY UNTIL 8 PM EDT MONDAY FOR LCZ460.

MICHIGAN WATERS OF LAKE ERIE...SMALL CRAFT ADVISORY UNTIL 8 PM EDT MONDAY FOR LEZ444.

&&

$$

UPDATE.......SC
AVIATION.....SC
SHORT TERM...CB
LONG TERM....DG/SS
MARINE.......DG


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.