Area Forecast Discussion
Issued by NWS Grand Rapids, MI

Home | Current Version | Previous Version | Text Only | 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 KGRR 011746
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
146 PM EDT WED OCT 1 2014

LATEST UPDATE...
AVIATION

.SYNOPSIS...
ISSUED AT 335 AM EDT WED OCT 1 2014

THE WEATHER WILL BE RATHER FALL LIKE OVER THE COURSE OF THE NEXT
SEVERAL DAYS WITH SWINGS IN TEMPERATURES...BREEZY CONDITIONS AND
SOAKING RAINS. CONDITIONS WILL BE RATHER BENIGN TODAY AND INTO
TONIGHT AS A RIDGE OF HIGH PRESSURE RETREATS FROM THE GREAT LAKES
REGION. A COLD FRONT WILL APPROACH THE AREA FROM THE WEST THURSDAY
AND THURSDAY NIGHT AND SWING THROUGH FRIDAY MORNING. SHOWERS WILL
BEGIN TO INCREASE IN COVERAGE THURSDAY MORNING AND BECOME MORE
WIDESPREAD AS WE HEAD THROUGH THE DAY AND INTO THURSDAY NIGHT. THE
HIGHEST CONCENTRATION OF PRECIPITATION WILL LIKELY COME THURSDAY
NIGHT INTO FRIDAY MORNING WHEN SHOWERS AND THUNDERSTORMS ARE
EXPECTED. COOLER AND SHOWERY WEATHER WILL SWEEP INTO THE REGION FOR
THE WEEKEND. HIGH TEMPERATURES WILL REACH A PEAK...70S...ON THURSDAY
IN THE SOUTHERLY WINDS AHEAD OF THE COLD FRONT. SATURDAY BEHIND THE
FRONT WE WILL STRUGGLE TO AROUND 50 FOR MAX TEMPERATURES.

&&

.UPDATE...
ISSUED AT 1120 AM EDT WED OCT 1 2014

STILL ANTICIPATING CLEARING TO OCCUR. PILOT REPORTS OVER THE
REGION SHOW THE CLOUDS WERE ONLY ABOUT 2K FEET THICK THIS
MORNING. DTX 12Z MORNING SOUNDING SHOWS AN INVERSION AROUND 4K
FEET TRAPPING THIS MOIST IN PLACE. HOWEVER EXPECT MIXING WILL
BREAK THIS INVERSION DOWN AND THE CLOUDS WILL ERODE. ALREADY SOME
BREAKS ALONG I-94...BREAKS OVER THE LAKE WEST OF LDM...AND A SMALL
HOLE OPENING UP NEAR CAD. WITH MAX AFTERNOON MIXING OCCURRING...
EXPECT MOST AREAS WILL SEE PEEKS OF SUN BY 2 PM AND INTO THE REST
OF THE AFTERNOON. BECAUSE OF THE DELAYED CLEARING I INCHED THE MAX
TEMPS DOWN SLIGHTLY. EXPECT MAINLY MID 60S WITH A COUPLE LOCATIONS
POSSIBLY REACHING THE UPPER 60S. THESE MAXES WILL PROBABLY NOT
OCCUR UNTIL LATE AFTERNOON.

&&

.SHORT TERM...(TODAY THROUGH FRIDAY)
ISSUED AT 335 AM EDT WED OCT 1 2014

MAIN FORECAST FOCUS IS ON THE STRONG FALL STORM SYSTEM TO SWING
THROUGH THE AREA THURSDAY INTO FRIDAY. CHANCES FOR PRECIPITATION
BEGIN TO INCREASE LATE TONIGHT AS MOISTURE BEGINS TO SURGE IN FROM
THE WEST. A SOLID INCREASE IN DEW POINTS AT 850MB/S IN NOTED BY ALL
THE MODELS WE WILL NOT HAVE SIGNIFICANT INSTABILITY IN PLACE SO ONLY
EXPECTING SHOWERS IN THE WEST LATE.

BETTER CHANCES BEGIN TO SHOW UP ON THURSDAY AS 850MB MOISTURE
TRANSPORT BEGINS TO INCREASE. THAT SAID...THE VALUES ARE NOT
SIGNIFICANT. EXPECTING DECENT COVERAGE TO OVERSPREAD THE AREA
THOUGH...ESPECIALLY IN THE AFTERNOON. MOST AREAS SHOULD SEE RAIN
SHOWERS ALONG WITH SOME EMBEDDED THUNDERSTORMS ESPECIALLY IN THE
AFTERNOON.

BY FAR THE BEST MOISTURE TRANSPORT OCCURS THURSDAY NIGHT INTO FRIDAY
MORNING. EXPECTING SOAKING RAINS DURING THIS TIME FRAME WITH ROUNDS
OF SHOWERS AND STORMS MOVING THROUGH THE AREA. CONVECTION ALLOWING
MODELS SHOW THIS TO BE THE CASE AS WELL...INCLUDING THE 4KM NAM.
SEVERE THREAT STILL LOOKS SLIM GIVEN TIMING WHICH WILL LIMIT
INSTABILITY. WINDS ARE STRONG IN THE LOWER TROP HOWEVER AND WE WILL
NEED TO KEEP AN EYE ON LINEAR STORMS FOR WIND POTENTIAL. 40-50 KNOTS
RESIDES IN THE PROFILE BETWEEN 1500-4000FT.

THE COLD FRONT SWEEPS EAST ON FRIDAY WITH COLD AIR ADVECTION SETTING
IN THROUGH THE COURSE OF THE DAY. WE WILL PROBABLY FALL BACK INTO
THE 50S DURING THE AFTERNOON.

AS FOR TODAY...EXPECTING A GRADUAL EROSION OF THE LOW CLOUDS FROM
THE SOUTH. THE NAM HAS DONE VERY WELL THE LAST COUPLE DAYS IN REGARD
TO THE LOW CLOUDS THOUGH AND IT KEEPS SOLID MOISTURE IN AT LEAST
THROUGH THE EARLY AFTERNOON. THE TREND SHOULD BE TOWARD
IMPROVEMENT/CLEARING THOUGH.

.LONG TERM...(FRIDAY NIGHT THROUGH TUESDAY)
ISSUED AT 335 AM EDT WED OCT 1 2014

THE MAIN THEME FOR THE LONG TERM PORTION OF THE FCST CONTINUES TO BE
COOL AND UNSETTLED CONDITIONS EXPECTED RIGHT THROUGH THE PERIOD.

THE PATTERN SHIFT IN THE UPPER LEVELS OF THE ATMOSPHERE THAT WILL
TAKE PLACE WILL BE JUST ABOUT COMPLETE BY THE BEGINNING OF THE LONG
TERM ON FRI NIGHT. WE WILL BE SEEING THE LONG WAVE TROUGH THAT
EXTENDS FROM THE ROCKIES RIGHT ON THROUGH NRN BRITISH COLUMBIA
DIGGING SE. A STRONG SHORT WAVE WILL HELP DRIVE THIS LONG WAVE
TROUGH OVER THE AREA AND SET IT UP AS THE UPPER AIR PATTERN BECOMES
QUITE AMPLIFIED FROM THE PACIFIC THROUGH THE ATLANTIC. STRONG
RIDGING ACROSS THE ERN PACIFIC AND WRN ATLANTIC WILL HELP KEEP THIS
PATTERN INTACT.

THIS LONG WAVE TROUGH WILL BRING A COLD POOL OF AIR DOWN FROM CANADA
ALONG WITH A WAVE TRAIN OF SHORT WAVES POISED TO MOVE THROUGH THE
REGION ON NW FLOW ALOFT. THIS WILL BRING WAVES OF RAIN SHOWERS TO
THE AREA AT TIMES...WITH SOME ENHANCEMENT OF THE SHOWERS AND SOME
PURE LAKE EFFECT RAIN SHOWERS FROM LAKE MICHIGAN WITH SUFFICIENT
OVER LAKE INSTABILITY PRESENT. TIMING OF THESE FEATURES WILL BE
PROBLEMATIC AS EXPECTED WITH A PATTERN LIKE THIS. WATERSPOUTS REMAIN
A DISTINCT POSSIBILITY OVER THE LAKE WITH THE TROUGH AND COLD POOL
ALOFT OVERHEAD.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z THURSDAY AFTERNOON)
ISSUED AT 145 PM EDT WED OCT 1 2014

I AM STILL GOING WITH THE IDEA THESE LOW CLOUDS WILL CLEAR OUT BY
LATE AFTERNOON. THE VISIBLE SATELLITE LOOPS SHOWS SKIES CLEARING
WEST OF A MKE TO BEH TO FWA LINE AT 1730Z. THIS AREA IS WHERE THE
925 MB WIND BECOMES MORE SOUTHERLY. I EXPECT THIS AREA TO REACH
THE I-96 TAF SITES IN THE 22Z TIME FRAME. SKIES WILL REMAIN MOSTLY
CLEAR THROUGH AT LEAST 06Z OR SO.

CLOUDS FROM THE FRONTAL SYSTEM TO OUR WEST MOVES IN AFTER 06Z. STILL
VFR SHOULD CONTINUE UNTIL THE CONVECTION FROM THE FIRST SURGE OF
DEEP MOISTURE MOVES IN AROUND 12Z. THERE IS ELEVATED INSTABILITY
AND THE 850 LI IS AROUND -1C BY 12Z. GIVEN THE PRECIPITABLE WATER
IS 2 STANDARD DEVIATIONS FROM NORMAL BY THEN... HARD TO IMAGINE WE
WOULD NOT GET AN AREA OF THUNDERSTORMS TO MOVE INTO SOUTHWEST
LOWER MICHIGAN. BOTH THE NAM AND GFS SHOW A STRENGTHENING LOW LEVEL
JET MOVING INTO SOUTHWEST MICHIGAN AROUND 12Z. THAT SHOULD HELP
THE CAUSE OF DEVELOPING THUNDERSTORMS. SEEMS THE CONVECTION
WEAKENS AS IT MOVES OUT AHEAD OF THE BETTER DYNAMICS BY MID
MORNING.... SO I EXPECT THE SHOWERS TO WEAKEN AS THEY REACH THE
I-69 TAF SITES BY 15Z. AFTER THE SHOWERS MOVE THROUGH I EXPECT LOW
CLOUDS AND FROM FOG.

&&

.MARINE...
ISSUED AT 335 AM EDT WED OCT 1 2014

FAIRLY TAME CONDITIONS OUT ON THE LAKE TODAY AND INTO TONIGHT BEFORE
THE WINDS BEGIN TO RAMP UP. WE ARE LOOKING AT SOUTHERLY WINDS WHICH
MAY FLIRT WITH SMALL CRAFT ADVISORY CONDITIONS THURSDAY AND THURSDAY
EVENING. BETTER CHANCES FOR STRONG WINDS AND HIGH WAVES SET UP FOR
LATE THURSDAY NIGHT INTO SATURDAY. SMALL CRAFT ADVISORY CONDITIONS
DURING THIS TIME ARE LIKELY IF NOT GALES AT TIMES. THE FALL SEASON
LOOKS TO BE TAKING SHAPE ON THE GREAT LAKES.


&&

.HYDROLOGY...
ISSUED AT 335 AM EDT WED OCT 1 2014

SOAKING RAINS ARE EXPECTED FROM THURSDAY INTO FRIDAY. AMOUNTS OF
0.75 TO 1.50 INCHES APPEAR COMMON. COULD SEE SOME LOCALLY HEAVIER
AMOUNTS ESPECIALLY ACROSS WEST CENTRAL LOWER MICHIGAN TOWARDS
MUSKEGON AND LUDINGTON. THE GOOD THING IS RIVER LEVELS ARE LOW AND
SHOULD BE ABLE TO ABSORB THOSE AMOUNTS WITHOUT MUCH ISSUE. WE WILL
BE KEEPING AN EYE ON MODEL FORECAST TRENDS THOUGH. WPC IS
FORECASTING AMOUNTS BY SATURDAY MORNING OF 2+ INCHES OVER A GOOD
DEAL OF WESTERN LOWER MI. PWAT VALUES ARE STILL FORECAST TO BE UP
AROUND 1.7 INCHES WHICH IS NEAR THE 99TH PERCENTILE FOR THIS TIME OF
YEAR. A SOLID SURGE OF MOISTURE IS FEEDING NORTH INTO THE SYSTEM OFF
THE GULF.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LM...NONE.
&&

$$

UPDATE...JK
SYNOPSIS...DUKE
SHORT TERM...DUKE
LONG TERM...NJJ
AVIATION...WDM
HYDROLOGY...DUKE
MARINE...DUKE





USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.