Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 010549
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
149 AM EDT MON SEP 1 2014

LATEST UPDATE...
AVIATION

.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 06Z TAFS THROUGH 06Z MONDAY NIGHT)
ISSUED AT 149 AM EDT MON SEP 1 2014

THERE ARE A FEW ITEMS THAT COULD IMPACT AVIATION OPERATIONS OVER
THE NEXT 24 HOURS ACROSS SW LOWER MI. THE FIRST ITEM IS FOG
POTENTIAL. A DECENT AMOUNT OF LOW LEVEL MOISTURE REMAINS IN
PLACE THIS MORNING AND TEMPS AND DEW POINTS ARE CLOSE ALREADY. THE
BEST CHC FOR FOG AND SOME POSSIBLE STRATUS WILL BE ALONG AND SE OF
I-69 WHERE A FEW SHOWERS WERE PRESENT EARLIER AND WHERE THE
MOISTURE HAS HUNG IN THE MOST. CAN NOT RULE OUT SOME NEAR KGRR AND
KAZO...BUT THE FURTHER WEST THE WINDS WILL REMAIN UP AND LIMIT FOG POTENTIAL.

THE NEXT THING IS THE POTENTIAL FOR PCPN TODAY. MOST DATA
INDICATES THAT WHATEVER IS LEFT OF THE LINE OF SHOWERS/STORMS NEAR
THE MISSISSIPPI RIVER AS OF 0545Z WILL MOVE INTO THE AREA
TOWARD 15Z OR SO. IT WILL INITIALLY FALL APART WITH LESS CHC OF
IMPACTS FROM IT TOWARD THE LAKESHORE. AS IT ENCOUNTERS SOME
DIURNAL INSTABILITY TOWARD THE EAST...WE EXPECT IT TO REINTENSIFY
INTO A LINE OF STORMS BY THE TIME IT REACHES U.S.-127 BY 19Z OR
SO. BEST CHC FOR LOWER CONDITIONS WILL BE ACROSS THE EAST WHERE
IFR WOULD BE LIKELY IN HEAVY RAINFALL. THIS CAN BE FINE TUNED
CLOSER TO THE EVENT.

ONCE THE LINE OF STORMS MOVES EAST...THERE SHOULD BE SOMEWHAT OF A
BREAK. ANOTHER PERIOD OF SOME SHOWERS WILL BE POSSIBLE WITH THE
WAVE TOWARD 00Z AND AFTER THAT.

&&

.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 10 AM EDT THIS MORNING THROUGH THIS
     EVENING FOR MIZ037-043-050-056-064-071.

LM...SMALL CRAFT ADVISORY FROM 10 AM THIS MORNING TO 10 PM EDT THIS
     EVENING FOR LMZ844>849.

&&

$$

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





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