Area Forecast Discussion
Issued by NWS Grand Rapids, MI

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
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 311930
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
330 PM EDT SUN AUG 31 2014

LATEST UPDATE...
SYNOPSIS/SHORT TERM/LONG TERM/HYDRO/MARINE

.SYNOPSIS...
ISSUED AT 322 PM EDT SUN AUG 31 2014

A WEAK AREA OF HIGH PRESSURE WILL KEEP MUCH OF THE REGION DRY INTO
THE EVENING. A COLD FRONT WILL APPROACH FROM THE WEST ON LABOR DAY
TRIGGERING SHOWERS AND THUNDERSTORMS. HIGH PRESSURE WILL RETURN
FOR TUESDAY DRYING THE REGION OUT.

&&

.SHORT TERM...(THIS EVENING THROUGH TUESDAY NIGHT)
ISSUED AT 322 PM EDT SUN AUG 31 2014

THE MAIN CHALLENGE IN THE SHORT TERM DEALS WITH THE POTENTIAL FOR
SEVERE WEATHER ON MONDAY. OVERALL THE POTENTIAL STILL EXISTS.

ONE POTENTIAL LIMITING FACTOR WILL BE WHAT IMPACTS THE DECAYING
AREA OF THUNDERSTORMS WILL HAVE AS IT MOVES IN FROM THE WEST
MONDAY MORNING. THE HRRR RUC SHOWS THIS SYSTEM WEAKENING WELL
BEFORE IT ARRIVES IN MI...SO I AM THINKING THIS WILL HAVE A
MINIMAL IMPACT ON THE POTENTIAL INSTABILITY MONDAY. THE
COMBINATION OF HEATING AND MOISTURE ADVECTION SUPPORTS CAPE OVER
1500 J/KG ON MONDAY. DEEP LAYER SHEAR INCREASES TOWARD 18Z AS THE
MID LEVEL WAVE CURRENTLY IN WI ARRIVES IN NW LOWER. THE LIFT
ASSOCIATED WITH THIS FEATURE SHOULD TRIGGER STORMS. THE SHEAR WILL
HELP TO INCREASE THE POTENTIAL FOR ORGANIZED CONVECTION AND
RESULTING SEVERE WEATHER. DAMAGING WINDS AND LARGE HAIL A THREAT.
SRH VALUES AROUND 200 M2/S2 DO SUPPORT A RISK FOR TORNADOES.





.LONG TERM...(WEDNESDAY THROUGH SUNDAY)
ISSUED AT 322 PM EDT SUN AUG 31 2014

MEDIUM RANGE MODELS ARE IN DECENT AGREEMENT INTO NEXT WEEKEND...
HOWEVER THERE ARE TIMING DIFFERENCES WITH A STRONG COLD FRONT THAT
COMES THROUGH FRIDAY/FRIDAY NIGHT.

LARGE HIGH PRESSURE IS EXPECTED TO BE SITTING OVER THE EAST SEABOARD
BY MID WEEK.  THIS WILL BRING WARMING SOUTHERLY FLOW TO THE GREAT
LAKES REGION.  IT CONTINUES TO LOOK LIKE THURSDAY WILL BE THE
WARMEST DAY OF THE WEEK WITH 80S FOR HIGHS.  THE RISK FOR SHOWERS
AND STORMS WILL INCREASE ON THURSDAY WITH A COLD FRONT MOVING INTO
THE WESTERN GREAT LAKES. WARM AND MOIST AIR WITH MOVE IN AHEAD OF
THIS FRONT.  IF A LOW LEVEL JET COMES INTO PLAY WE COULD BE LOOKING
AT STRONG TO SEVERE STORMS TOWARD THE END OF THE DAY.

THERE CONTINUES TO BE TIMING DIFFERENCES WITH THE FRONT...BUT THE
GFS SLOWED THE FRONT DOWN...CLOSER TO THE WHAT THE ECMWF HAS SHOWN.
THEREFORE BELIEVE THE FRONT WILL BE COMING THROUGH ON FRIDAY WITH
ADDITIONAL CHANCES FOR SHOWERS AND STORMS.  MUCH COOLER AIR FOLLOWS
THIS STRONG FRONT FOR FRIDAY NIGHT AND INTO NEXT WEEKEND.  H8 TEMPS
DROP TO +7 TO +10C AS COMPARED TO AROUND +19C AHEAD OF THE COLD
FRONT.  THE WEEKEND SHOULD FEATURE HIGHS IN THE UPPER 60S TO MID 70S
WITH MAINLY DRY WEATHER.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z MONDAY AFTERNOON)
ISSUED AT 134 PM EDT SUN AUG 31 2014

CEILINGS WERE TRENDING TOWARD VFR EARLY THIS AFTERNOON...HOWEVER
SOME MVFR MAY HOLD ON UNTIL ABOUT 20Z. OTHERWISE THE VFR AND LIGHT
WINDS WILL BE MAINTAINED INTO AND THROUGH MUCH OF THE OVERNIGHT. I
HAVE INTRODUCED SOME MVFR CEILINGS RETURNING AROUND DAYBREAK
MONDAY DUE TO MOIST LOW LEVELS AND DIURNAL TRENDS.

THEN BY LATE MONDAY MORNING/EARLY AFTERNOON SSW WINDS WILL
INCREASE WITH GUSTS AROUND 20 KNOTS. ALSO IN THIS TIME FRAME
WIDELY SCATTERED THUNDERSTORMS MAY BEGIN TO DEVELOP AS INSTABILITY
INCREASES AHEAD OF AN APPROACHING COLD FRONT.


&&

.MARINE...
ISSUED AT 322 PM EDT SUN AUG 31 2014

BEACH HAZARDS AND SCA ISSUED FOR MONDAY

&&

.HYDROLOGY...
ISSUED AT 322 PM EDT SUN AUG 31 2014

HIGH PWAT VALUES SUPPORT LOCALLY HEAVY RAIN ON MONDAY.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...BEACH HAZARDS STATEMENT FROM MONDAY MORNING THROUGH MONDAY
     EVENING FOR MIZ037-043-050-056-064-071.

LM...SMALL CRAFT ADVISORY FROM 10 AM TO 10 PM EDT MONDAY FOR
     LMZ844>849.

&&

$$

SYNOPSIS...MJS
SHORT TERM...MJS
LONG TERM...JK
AVIATION...JK
HYDROLOGY...MJS
MARINE...MJS






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