Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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000
FXUS63 KGRR 260008
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
808 PM EDT TUE AUG 25 2015

LATEST UPDATE...
MARINE

.SYNOPSIS...
ISSUED AT 315 PM EDT TUE AUG 25 2015

A LARGE SLOW MOVING LOW PRESSURE SYSTEM OVER THE LAKE SUPERIOR
REGION WILL CONTINUE TO PRODUCE FALL LIKE WEATHER THROUGH
WEDNESDAY WITH EXTENSIVE CLOUD COVER AND VERY COOL TEMPERATURES.
SCATTERED SHOWERS WILL LINGER TODAY INTO TONIGHT BEFORE GRADUALLY
ENDING WEDNESDAY. A HIGH PRESSURE RIDGE WILL BUILD IN AND BRING
FAIR WEATHER THURSDAY INTO FRIDAY ALONG WITH MODERATING
TEMPERATURES.

&&

.SHORT TERM...(THIS EVENING THROUGH THURSDAY NIGHT)
ISSUED AT 315 PM EDT TUE AUG 25 2015

FALL LIKE WX WILL CONTINUE THROUGH WEDNESDAY DUE TO A LARGE
VERTICALLY STACKED SFC/UPPER LEVEL LOW PRESSURE SYSTEM CENTERED
JUST NE OF LAKE SUPERIOR THAT WILL CONTINUE TO PRODUCE EXTENSIVE
LOW CLOUD COVER. UNSEASONABLY COOL WX WILL CONTINUE LATE THIS
AFTERNOON THROUGH TONIGHT AND WEDNESDAY WITH MIN TEMPS TONIGHT IN
THE 50S AND HIGH TEMPS WEDNESDAY ONLY REACHING THE 60S.

SEVERAL UPPER LEVEL DISTURBANCES MOVING SE AROUND THE PERIPHERY
OF THE UPPER LOW CENTER WILL COMBINE WITH DEEP LOW TO MID LEVEL
MOISTURE TO BRING A FEW LIGHT RAIN SHOWERS TONIGHT AND WEDNESDAY.
A LITTLE LAKE ENHANCEMENT IS POSSIBLE ALSO WITH H8 TEMPS OF ONLY
AROUND 6-7C THRU MIDDAY WED YIELDING DELTA T/S IN THE MIDDLE
TEENS.

SKIES WILL GRADUALLY CLEAR WEDNESDAY NIGHT AS THE VERTICALLY
STACKED LOW PRESSURE SYSTEM MOVES FURTHER NE AND AWAY FROM OUR
REGION AND OUR SFC WINDS VEER TO THE NORTH TO NE. HIGH PRESSURE
WILL BRING FAIR WX THURSDAY WITH A MIX OF SUN AND CLOUDS AND
SEASONABLE TEMPS REACHING THE 70 TO 75 DEGREE RANGE.

.LONG TERM...(FRIDAY THROUGH TUESDAY)
ISSUED AT 315 PM EDT TUE AUG 25 2015

OUR MAIN FOCUS IS ON ONE SYSTEM THAT COULD AFFECT PORTIONS OF THE
AREA FROM FRI NIGHT THROUGH SUN. WE WILL BE LOOKING AT TEMPS IN THE
LONG TERM RECOVERING TO AVERAGE LEVELS AND EVENTUALLY WARMING ABOVE
AVERAGE BY MID WEEK NEXT WEEK.

WE WILL SEE MOST OF FRI CONTINUE THE DRY TREND THAT STARTS IN THE
SHORT TERM ON THU. UPPER SHORT WAVE RIDGING WILL GRADUALLY SLIDE
EAST OF THE AREA LATE IN THE DAY. RAIN WILL TRY TO MOVE IN LATE
FRI...BUT LOOKS MORE LIKELY ON FRI NIGHT AS A SLOW MOVING SHORT WAVE
TROUGH APPROACHES THE AREA FROM THE WSW. THIS TROUGH LOOKS TO BE
DETACHED FROM THE MAIN JET ACROSS CANADA...THUS THE REASON FOR THE
SLOW MOVEMENT.

THE CHC OF RAIN WILL CONTINUE THROUGH MOST OF THE WEEKEND...HOWEVER
THERE IS A BIT OF UNCERTAINTY REGARDING TO LOCATION OF THE RAIN. THE
MODELS ARE SPLIT BETWEEN HAVING A PHASED SYSTEM BRING RAIN TO THE
ENTIRE AREA...AND HAVING A UNPHASED SYSTEM THAT WOULD FAVOR RAIN
OVER MAINLY THE SOUTH. WE ARE FAVORING THE UNPHASED SOLUTION AT THIS
TIME AS THE GFS AND NAM ARE NOTORIOUS FOR OVERDEVELOPING LOWS DUE TO
CONVECTION...AND DUE TO THE CONSISTENCY OF THE ECMWF.

ONCE THE WEAKENING TROUGH MOVES THROUGH ON SUN...WE ARE THEN LOOKING
AT A FAIRLY SIGNIFICANT WARM UP AFTER THIS RECENT COOL SPELL. A
FAIRLY SUBSTANTIAL LONG WAVE TROUGH WILL MOVE INTO THE WRN PORTION
OF NORTH AMERICA. THIS WILL IN TURN BUILD THE DOWNSTREAM RIDGE AS IT
MOVES TOWARD THE AREA. 500 MB HEIGHTS WILL BE APPROACHING 590 DM AND
H850 TEMPS LOOK TO APPROACH THE MID TO UPPER TEENS C. TEMPS COULD BE
APPROACHING 90 BY THIS TIME NEXT WEEK. WE SHOULD BE MAINLY DRY MON
AND TUE WITH THE RIDGE TAKING CONTROL.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z WEDNESDAY EVENING)
ISSUED AT 649 PM EDT TUE AUG 25 2015

THE MAIN CHALLENGE WITH THE AVIATION FORECAST DEALS WITH THE
CEILING HEIGHTS AND ANY IMPACTS. MOISTURE WILL REMAIN ELEVATED IN
THE LOW LEVELS INTO WEDNESDAY. THE WIDESPREAD MVFR CEILINGS ARE
FORECASTED TO GIVE WAY TO MVFR CEILINGS BY MIDNIGHT AS SLIGHT
DRYING OCCURS. HOWEVER THE CEILINGS WILL LIKELY LOWER AGAIN AS
SOME LIFT DEVELOPS LATE TONIGHT. THEREFORE I FEATURE MVFR CEILINGS
FOR LATER TONIGHT...ALSO WITH SOME SHOWERS IN THE AREA.

AS TEMPERATURES START TO WARM UP ON WEDNESDAY...THIS WILL ACT TO
RAISE THE CEILINGS AGAIN...TO VFR LEVELS. HOW QUICKLY THIS OCCURS
IS NOT CERTAIN...BUT BY 18Z IT APPEARS THAT WE SHOULD SEE THIS
IMPROVEMENT.


&&

.MARINE...
ISSUED AT 806 PM EDT TUE AUG 25 2015

WAVES WILL GENERALLY RUN 2 TO 4 FEET INTO WEDNESDAY. THE MAIN
REASON FOR THE ELEVATED WAVES IS THE CONTINUED COLD AIR ADVECTION
PATTERN THAT WE ARE IN.  THUS A MODERATE RISK FOR BEACH HAZARDS
AND NEAR SMALL CRAFT CONDITIONS ARE FORECASTED. THE WEB CAMS AND
BUOYS SUPPORTED DROPPING THE EXISTING HEADLINES FOR NOW.

&&

.HYDROLOGY...
ISSUED AT 1240 PM EDT TUE AUG 25 2015

WITH LIGHT RAIN FORECAST INTO WEDNESDAY FOLLOWED BY DRY WEATHER
THURSDAY/FRIDAY AND MORE LIGHT RAIN FRIDAY NIGHT INTO SATURDAY...
RIVER LEVELS WILL REMAIN LOW INTO NEXT WEEK WITH NO FLOODING
CONCERNS.

&&

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

$$

SYNOPSIS...LAURENS
SHORT TERM...LAURENS
LONG TERM...NJJ
AVIATION...MJS
HYDROLOGY...63
MARINE...MJS



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