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
000
FXUS63 KDTX 301923
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
323 PM EDT SAT APR 30 2016

.DISCUSSION...

A GOOD AMOUNT OF MOISTURE POOLED UP OVER WESTERN OHIO VALLEY (12Z
KILX SOUNDING INDICATED 9 C DEW PT AT 850 MB) WILL CONTINUE TO
PROGRESS OFF TO THE NORTHEAST INTO SOUTHERN LOWER MICHIGAN EARLY
THIS EVENING. SOLID UPPER LEVEL DIVERGENCE/PV ADVECTION/HEIGHT FALLS
AND LOW LEVEL MOISTURE TRANSPORT/ISENTROPIC ASCENT TO SUPPORT
WIDESPREAD RAINFALL...WITH PW VALUES REACHING 1 INCH ALONG/SOUTH OF
I-69 CORRIDOR...SUPPORTIVE OF AMOUNTS REACHING AND LIKELY ECLIPSING
HALF AN INCH TONIGHT...ESPECIALLY WITH ANY CONVECTIVE ELEMENTS...AS
SHOWALTER INDEX PROGGED TO DROP BELOW ZERO JUST PAST THE SOUTHERN
MICHIGAN BORDER...BUT LITTLE IN THE WAY OF ACTUAL CAPE...SHOULD BE
HARD PRESSED TO SEE ANY THUNDERSTORMS. MID LEVEL LAPSE RATE DO
BECOME STEEP ON SUNDAY (7+ C/KM)...BUT MAINLY DUE TO THE DRYING
OCCURRING IN THE MID LEVELS...AND DON`T EXPECT MUCH SHOWER ACTIVITY
DURING THE DAY. VERY TIGHT LOW LEVEL BAROCLINIC ZONES IN PLACE (850
MB TEMPS OF 1 C OVER SAGINAW TO 10 C NEAR OHIO BORDER PER 12Z
EURO)...AND EVEN WOULD NORTHEAST SURFACE WINDS...COULD SEE FAR SOUTH
REACH AND EXCEED 60 DEGREES WITH PREVIOUSLY MENTIONED DRYING/LULL IN
ACTIVITY.

THE 00Z MODEL SUITE INDICATED A FARTHER NORTH SURFACE/LOW LEVEL
FRONTAL BOUNDARY PLACEMENT TOMORROW...WHICH LOOKS TO SET US UP FOR
ANOTHER ROUND OF RAINFALL SUNDAY EVENING....AS SECOND WAVE AND
LEFTOVER UPPER LEVEL CIRCULATION FROM THE CENTRAL PLAINS SLIDES
EAST...PROVIDING GOOD UPPER LEVEL DIVERGENCE/DEFORMATION AXIS WHICH
LOOKS TO CLIP AREAS SOUTH OF I-69 CORRIDOR. THE 12Z MODEL
NAM/GFS/CANADIAN HAVE SHIFTED BACK TO THE SOUTH A BIT...BUT 12Z EURO
REMAINS MOST AGRESSIVE/ADAMANT...AND FEEL CONFIDENT TO GO LIKELY
POPS SOUTH OF I-69 TO CATEGORICAL NEAR THE OHIO BORDER. SUBSTANTIAL
COLD ADVECTION TO TAKE PLACE BEHIND THE MERGING NORTHERN STREAM
TROUGH AXIS PASSAGE MONDAY MORNING...WITH 850 MB TEMPS STILL PROGGED
TO FALL TO ZERO...OR EVEN SLIGHTLY COLDER. NORTHEAST FLOW OFF LAKE
HURON AND EXPECTED CLOUD COVER ON MONDAY COULD PROVE SUFFICIENT TO
KEEP MAXES UNDER 60 DEGREES. IF LOW CLOUDS DISSIPATE MONDAY
NIGHT...FROST CONCERNS WILL RETURN AS TEMPERATURES POTENTIALLY
FALL BACK INTO THE 30S WITH CALM/NEARLY CALM WINDS.

WEAK AND FRAGILE HIGH PRESSURE WILL LINGER OVER LOWER MICHIGAN
TUESDAY BETWEEN LOW PRESSURE OVER THE OHIO VALLEY AND THE NEXT COLD
FRONT PUSHING THROUGH NORTHERN ONTARIO. EXPECT THERE WILL AT LEAST
BE CLOUDS AROUND WITH A PORTION OF THE UPPER TROUGH SUPPORTING THE
OHIO VALLEY SURFACE TROUGH. THIS WILL PRODUCE TEMPERATURES RIGHT
AROUND NORMAL FOR EARLY MAY FOR ONE MORE DAY BEFORE THE ONTARIO
FRONT MOVES THROUGH THE GREAT LAKES WEDNESDAY. THERE IS INCREASING
EVIDENCE IN GLOBAL MODEL SOLUTIONS THAT SUPPORT CLOSING OFF THE
ASSOCIATED UPPER WAVE BY THURSDAY WHICH WILL KEEP SHOWERS AND COOLER
TEMPERATURES OVER THE REGION POSSIBLY EVEN INTO FRIDAY. THIS IS AN
UNPLEASANT WEATHER SCENARIO FOR THE SECOND HALF OF NEXT WEEK
HIGHLIGHTED BY TEMPERATURES THAT WILL STRUGGLE TO REACH GUIDANCE
VALUES IN THE LOWER TO MID 50S...ESPECIALLY FOR THURSDAY. THESE
TYPES OF CLOSED SYSTEMS OFTEN END UP BEING SLOWER TO EVOLVE THAN
MODEL FORECASTS WHICH ALSO POINTS TO A SHAKY START TO NEXT WEEKEND
AS WELL.

&&

.MARINE...

WINDS WILL INCREASE FROM THE NORTHEAST TONIGHT AS LOW PRESSURE
PASSES THROUGH THE OHIO VALLEY...AND REMAIN GUSTY OVER LAKE HURON
TOMORROW AS THE LOW MOVES INTO THE EASTERN GREAT LAKES. SMALL CRAFT
ADVISORIES REMAIN IN EFFECT LATE TONIGHT THROUGH SUNDAY FOR THE LAKE
HURON NEARSHORE WATERS...INCLUDING SAGINAW BAY...AS PERSISTENT AND
STRONG FLOW ACROSS THE LAKE ALLOWS WAVE HEIGHTS TO BUILD BETWEEN 4
AND 8 FEET. GUSTS AROUND 25 KNOTS WILL ALSO DEVELOP TONIGHT AND
CONTINUE INTO SUNDAY BEFORE LOW PRESSURE MOVES EAST AND SPEEDS
DECREASE. THIS WILL ALSO ALLOW LARGE WAVES TO SUBSIDE DURING THE
LATE EVENING. A VERY LARGE DOME OF HIGH PRESSURE CENTERED OVER THE
CENTRAL PLAINS WILL THEN KEEP WINDS FAIRLY LIGHT MONDAY INTO TUESDAY.

A BRIEF PERIOD OF GUSTY EAST-NORTHEAST WINDS IS ALSO EXPECTED THIS
EVENING...BETWEEN 6 PM AND 11 PM...OVER WESTERN LAKE ERIE AS THE
CENTER OF LOW PRESSURE DRAWS CLOSER. GUSTS MAY APPROACH 25 KNOTS FOR
SEVERAL HOURS BEFORE WINDS WEAKEN AND FINALLY TURN LIGHT FROM THE
NORTH BEFORE SUNRISE.

&&

.HYDROLOGY...

LOW PRESSURE PASSING THROUGH THE OHIO VALLEY WILL SPREAD WIDESPREAD
AND STEADY RAINFALL INTO SOUTHEAST MICHIGAN LATE THIS AFTERNOON
THROUGH TONIGHT...WITH SHOWERS THEN LINGERING THROUGH SUNDAY. THE
HEAVIEST RAIN LOOKS TO FALL BETWEEN 9 PM AND 4 AM TONIGHT. TOTAL
RAINFALL THROUGH 2 PM SUNDAY LOOKS TO EXCEED 0.25 INCHES ACROSS ALL
OF SOUTHEAST MICHIGAN...WITH TOTALS BETWEEN 0.75 AND 1.00 INCH SOUTH
OF THE M-59 CORRIDOR. THIS RAINFALL WILL PROMPT RISES ON AREA
RIVERS...CREEKS...AND STREAMS...BUT FLOODING IS NOT EXPECTED.

ANOTHER QUICK ROUND OF RAINFALL IS EXPECTED SUNDAY NIGHT ACROSS FAR
SOUTHERN MICHIGAN. LOCATIONS ALONG AND SOUTH OF I-94 MAY PICK UP AN
ADDITIONAL 0.25 INCHES OF RAIN.

&&

.AVIATION...ISSUED 133 PM EDT SAT APR 30 2016

HIGH CLOUDS AND VFR CONDITIONS WILL START OUT THE 18Z TAF PERIOD
BEFORE A LOW PRESSURE SYSTEM TRACKING THROUGH THE OHIO VALLEY BRINGS
A DETERIORATION IN CEILINGS/VIS AS RAIN MOVES INTO THE AREA. RAIN
SHIELD STRETCHING FROM SOUTHWEST MICHIGAN DOWN THROUGH NORTHWEST
OHIO IS ADVANCING TOWARDS THE AREA NOW...AND IS EXPECTED TO SPILL
INTO THE TERMINALS DURING THE 20-23Z TIMEFRAME. DRY FEED OF LOW-
LEVEL FLOW FROM THE EAST WILL INITIALLY KEEP CEILINGS/VIS AT VFR AS
RAIN BEGINS. BETTER FORCING AND MOISTURE ARRIVING AROUND 00Z WILL
THEN QUICKLY DROP CONDITIONS TO LOW-END MVFR AND IFR BY MID-EVENING.
RAIN WILL BE HEAVIER NEAR THE DETROIT-AREA TERMINALS WHERE A LITTLE
MORE INSTABILITY WILL RESIDE...AND EXPECT TO SEE A FEW DIPS TO LIFR
DURING THE LATE EVENING AND VERY EARLY MORNING ON SUNDAY. RAIN WILL
LIFT NORTH AND EAST OF THE AREA OVERNIGHT...BY ABOUT 08Z FOR MOST
LOCATIONS. A FEW SHOWERS WILL LINGER THROUGH EARLY
SUNDAY...ESPECIALLY AT MBS.

FOR DTW...LATEST MODEL FORECAST GUIDANCE AND EXTRAPOLATION FROM
UPSTREAM RADAR SUPPORTS RAIN BEGINNING AT DTW BETWEEN 20-21Z...WITH
HEAVIER RAINFALL AND MVFR/IFR CEILINGS ARRIVING AFTER 00Z TONIGHT.
CEILINGS WILL INITIALLY BE VFR AS RAIN BEGINS AS DRY AIR IN THE LOW-
LEVELS MUST FIRST BE OVERCOME. A PERIOD OF STRONGER FORCING AND
INSTABILITY TONIGHT...ROUGHLY BETWEEN 02Z AND 05Z...MAY DROP
CONDITIONS TO LIFR IN HEAVIER SHOWERS. THUNDERSTORM POTENTIAL IS
LOW...BUT NOT ZERO.

//DTW THRESHOLD PROBABILITIES...

* MEDIUM FOR CIGS AOB 5KFT BY 22Z...HIGH AFTER 00Z.

* LOW FOR A THUNDERSTORM TO IMPACT DTW TONIGHT.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LAKE HURON...SMALL CRAFT ADVISORY FROM 5 AM TO 8 PM EDT SUNDAY FOR LHZ421-422-
     441>443.

LAKE ST CLAIR...NONE.
MICHIGAN WATERS OF LAKE ERIE...NONE.
&&

$$

DISCUSSION...SF/BT
MARINE.......HLO
HYDROLOGY....HLO
AVIATION.....HLO


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.