Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 311927
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
327 PM EDT MON AUG 31 2015

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

.SYNOPSIS...
ISSUED AT 327 PM EDT MON AUG 31 2015

HIGH PRESSURE WILL BE IN CONTROL OF THE AREAS WEATHER OVER THE NEXT
FEW DAYS.  THIS WILL KEEP THE REGION WARM WITH HIGHS IN THE 80S AND
MAINLY DRY.  THERE WILL BE THE CHANCE FOR SCATTERED SHOWERS AND
STORMS HOWEVER WEDNESDAY AFTERNOON AND WEDNESDAY NIGHT.

SHOWER CHANCES APPEAR TO REMAIN LOW THROUGH THE WEEKEND.  IT SHOULD
STAY WARM WITH HIGHS IN THE 80S...WITH A FEW TEMPERATURES NEAR 90.

&&

.SHORT TERM...(THIS EVENING THROUGH WEDNESDAY NIGHT)
ISSUED AT 327 PM EDT MON AUG 31 2015

AN UPPER RIDGE WILL DOMINATE THE WEATHER INTO TUESDAY...BUT THEN IT
SLOWLY BREAKS DOWN.  A SHORT WAVE TRIES TO MOVE INTO THE RIDGE
WED/WED NIGHT THAT COULD BE ENOUGH TO PRODUCE ISOLATED OR WIDELY
SCATTERED SHOWERS AND STORMS.

LITTLE CHANGE TO THE FORECAST FOR TONIGHT AND TUESDAY WITH THE UPPER
RIDGE IN PLACE.  THERE WILL BE A WEAK UPPER LOW OVER CENTRAL INDIANA
IN THE MEANTIME...BUT ANY ISOLATED CONVECTION ASSOCIATED WITH THIS
FEATURE SHOULD REMAIN SOUTH.  AREAS OF FOG ARE LIKELY AGAIN
TONIGHT...BUT A BIT MORE MIXING SHOULD LEAD TO LESS AREAS OF DENSE
FOG.  HIGHS ON TUESDAY AWAY FROM THE LAKE MAINLY IN THE MID 80S...
WITH A FEW UPPER 80S WELL INLAND.

AS THE UPPER RIDGE BREAKS DOWN SOME OF THE MOISTURE FROM THE INDIANA
UPPER LOW MAY CREEP INTO THE SOUTHERN CWA TUESDAY NIGHT.  HAVE 20
POPS IN CASE A STRAY SHOWER OR STORM MOVES IN.  INCREASED MIN TEMPS
TUESDAY NIGHT AS SOUTHERLY WINDS AND HIGH DEW POINTS PRODUCE A
WARM/MUGGY NIGHT.

THE INCREASED MOISTURE INTO WEDNESDAY COULD PRODUCE DIURNAL SHOWERS
AND STORMS...MAINLY EAST OF U.S. 131.  THEN THERE IS NOT GOOD
AGREEMENT IN THE MODELS AS TO HOW SUCCESSFUL THE NEXT SHORT WAVE
MOVES THROUGH THE WEAKENING UPPER RIDGE BY WEDNESDAY NIGHT.  BUT IT
WOULD SEEM THAT THIS RIDGE WEAKNESS AND SHORT WAVE SHOULD LEAD TO AN
MCS MOVING ALONG THE WESTERN EDGE OF THE RIDGE.  ADDED CHANCE POPS
FOR THIS MCS TO IMPACT THE NW CWA.

.LONG TERM...(THURSDAY THROUGH MONDAY)
ISSUED AT 327 PM EDT MON AUG 31 2015

THE MAIN STORY IN THE LONG TERM IS THAT VERY WARM TEMPERATURES AND
HUMID CONDITIONS WILL CONTINUE THROUGH THE HOLIDAY WEEKEND. THE
DAILY RISK OF RAIN IS QUITE LOW WITH LIMITED COVERAGE OF CONVECTION
EXPECTED.

A FEW SHOWERS OR THUNDERSTORMS ARE POSSIBLE ON THURSDAY DUE TO THE
COMBINATION OF A MID LEVEL SHORTWAVE PASSING THROUGH AND A WEAK
BACKDOOR COLD FRONT SLIPPING DOWN FROM THE NORTHEAST AND STALLING.
THIS ILL-DEFINED SFC BOUNDARY MAY STILL BE SITUATED NW-SE OR N-S
ACROSS THE AREA ON FRIDAY AND WEAK CONVERGENCE ALONG IT... OR THE
LAKE BREEZE... COULD FOCUS A FEW ISOLATED SHOWERS OR STORMS.

ON SATURDAY AND SUNDAY THE UPPER RIDGE RE-AMPLIFIES IN RESPONSE TO
THE UPPER LOW/TROUGH DROPPING SOUTH THROUGH THE PACIFIC NORTHWEST.
THE RIDGE DOES BEGIN TO FLATTEN OUT ON LABOR DAY AS SHORTWAVE ENERGY
EJECTS OUT OF THE WESTERN TROUGH. THE SHOWER AND TSTM POTENTIAL MAY
INCREASE AS THIS HAPPENS... ALTHOUGH CONFIDENCE IS LOW AS TO WHEN
(AND IF) THE COLD FRONT WILL ARRIVE.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z TUESDAY AFTERNOON)
ISSUED AT 156 PM EDT MON AUG 31 2015

WE WILL PROBABLY SEE A REPEAT OF IFR/LIFR FOG AND STRATUS AGAIN
LATE TONIGHT AND EARLY TUESDAY. THE LATEST GUIDANCE IS NOT QUITE
AS AGGRESSIVE ON DEVELOPING FOG TONIGHT...SHOWING DRIER BOUNDARY
LAYER CONDITIONS AND A BIT MORE WIND JUST ABOVE THE SFC. HOWEVER
SINCE THE OVERALL SYNOPTIC REGIME AND AIR MASS IS LARGELY
UNCHANGED... DECIDED TO GO WITH PERSISTENCE AND FCST IFR FOG AT
ALL THE TAF SITES FROM 09Z TO 14Z. THIS WILL BE FOLLOWED BY
QUICKLY IMPROVING CONDITIONS BY MID TO LATE MORNING DUE TO THE
SHALLOW NATURE OF THE FOG/STRATUS.

&&

.MARINE...
ISSUED AT 327 PM EDT MON AUG 31 2015

RATHER QUIET REGIME ON THE LAKE WITH RIDGING OVERHEAD.  THE PRESSURE
GRADIENT SHOULD TIGHTEN A BIT INTO TUESDAY NIGHT AND SSW WINDS SHOULD
PICK UP.  IT CAUSE THE LAKE TO BECOME A BIT ROUGH WITH SOME 2-3 FOOT
WAVES.

&&

.HYDROLOGY...
ISSUED AT 327 PM EDT MON AUG 31 2015

HYDRO CONCERNS ARE LOW THIS WEEK. THERE ARE SMALL CHANCES FOR A
SHOWER IN ANY GIVEN LOCATION FROM MID WEEK INTO THE WEEKEND.
EXCESSIVE RAINFALL IS UNLIKELY.

&&

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

$$

SYNOPSIS...JK
SHORT TERM...JK
LONG TERM...MEADE
AVIATION...MEADE
HYDROLOGY...CAS/JK
MARINE...JK



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