Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 310336
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
1136 PM EDT WED JUL 30 2014

LATEST UPDATE...
AVIATION

.SYNOPSIS...
ISSUED AT 300 PM EDT WED JUL 30 2014

AN UPPER LEVEL LOW PRESSURE SYSTEM WILL REMAIN CENTERED OVER
ONTARIO THROUGH THE END OF THE WEEK. THIS SYSTEM WILL ACT TO KEEP
THE TEMPERATURES BELOW NORMAL FOR LOWER MICHIGAN. THERE WILL BE
A FEW SHOWERS AND THUNDERSTORMS AROUND...MAINLY DURING THE
AFTERNOON AND EVENING HOURS.

&&

.SHORT TERM...(THIS EVENING THROUGH FRIDAY NIGHT)
ISSUED AT 300 PM EDT WED JUL 30 2014

THE MAIN CHALLENGE IN THE SHORT TERM DEALS WITH THE POTENTIAL FOR
SHOWERS AND THUNDERSTORMS. ENOUGH INSTABILITY DEVELOPED TO FORM A
FEW SHOWERS TODAY. MAY END UP WITH A FEW STORMS BASED OFF OF LOCAL
LAPS SOUNDINGS. COULD BE GUSTY WINDS GIVEN THE INVERTED V LOW
LEVEL PROFILE. THESE SHOULD DISSIPATE AS WE GO THROUGH THE
EVENING. THE MAIN AREA WILL GENERALLY BE SOUTHEAST OF A ALMA TO
GRAND RAPIDS LINE.

MODELS ARE TRYING TO DEVELOP A WAVE OF LOW PRESSURE THU NIGHT INTO
FRI ACROSS THE REGION. THE MID LEVEL TROUGH SHARPENS UP OVERHEAD
AND SATURATION DEEPENS CLOSE TO THE DGZ. THUS I BUMPED UP POPS TO
ACCOUNT FOR THIS POTENTIAL SYSTEM.

I DID ADD FOG TO THE AREA SOUTH OF HOLLAND THIS EVENING GIVEN THE
VISIBLE SATELLITE IMAGERY SHOWING THE MARINE FOG MOVING ONSHORE.

.LONG TERM...(SATURDAY THROUGH WEDNESDAY)
ISSUED AT 300 PM EDT WED JUL 30 2014

THERE IS STILL A CHANCE OF DIURNALLY DRIVEN SHOWERS AND PERHAPS A
FEW STORMS SATURDAY WITH THE UPPER TROUGH AXIS AND ASSOCIATED POOL
OF COOLER AIR ALOFT OVERHEAD. THE TROUGH AXIS SHOULD FINALLY MOVE
EAST OF OUR REGION SUNDAY. TEMPS THROUGH THE WEEKEND WILL AVERAGE
QUITE CLOSE TO NORMAL.

A COLD FRONT WILL DROP DOWN FROM THE NW ON MONDAY BRINGING A CHANCE
OF SHOWERS AND THUNDERSTORMS. THE BOUNDARY WILL THEN LIKELY SLOW
DOWN AND POTENTIALLY STALL OUT ACROSS THE LOWER GREAT LAKES REGION
TUESDAY AND BRING A CONTINUED CHANCE OF SHOWERS AND STORMS TO OUR
AREA.

IN FACT THE CHANCE OF SHOWERS AND STORMS REMAINS IN THE
FORECAST THROUGH THE MIDDLE OF NEXT WEEK WITH THAT FRONTAL BOUNDARY
OVER OUR REGION AND WITH LOW PRESSURE EXPECTED TO GRADUALLY APPROACH
FROM THE WEST LATE NEXT WEEK. TEMPS SHOULD CONTINUE TO AVERAGE
RATHER CLOSE TO NORMAL NEXT WEEK. THERE IS STILL A CHANCE OF
DIURNALLY DRIVEN SHOWERS AND PERHAPS A FEW STORMS SATURDAY WITH
THE UPPER TROUGH AXIS AND ASSOCIATED POOL OF COOLER AIR ALOFT
OVERHEAD. THE TROUGH AXIS SHOULD FINALLY MOVE EAST OF OUR REGION
SUNDAY. TEMPS THROUGH THE WEEKEND WILL AVERAGE QUITE CLOSE TO
NORMAL.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z THURSDAY NIGHT)
ISSUED AT 1136 PM EDT WED JUL 30 2014

VFR CONDITIONS EXPECTED THROUGH THE PERIOD AT ALL TERMINAL
LOCATIONS. A STRAY SHOWER COULD MOVE FROM WISCONSIN THROUGH LOWER
MICHIGAN IN THE FIRST THREE HOURS OF THE TAF PERIOD...BUT
CONFIDENCE IS VERY LOW IN THIS OCCURRING AND WILL NOT MENTION IN
THE TAFS. AFTERNOON/EVENING ISOLATED SHOWERS AND MAYBE A FEW
LIGHTNING STRIKES POSSIBLE GENERALLY 16Z THURSDAY THROUGH 00Z
FRIDAY.

&&

.MARINE...
ISSUED AT 742 PM EDT WED JUL 30 2014

WE HAVE EXTENDED THE MARINE DENSE FOG ADVISORY THE WAS SET TO
EXPIRE AT 8 PM FOR AREAS SOUTH OF GRAND HAVEN THROUGH 11 AM THU
MORNING. LATEST VISIBLE SATELLITE IMAGERY INDICATES THAT THE FOG
IS SHRINKING A BIT IN COVERAGE AND THINNING OUT A BIT THIS
EVENING. HOWEVER THE WEBCAM OVERLOOKING THE HOLLAND PIER INDICATES
THAT VISIBILITY IS NEAR ZERO STILL IN THE FOG. WITH WINDS
EXPECTING TO BECOME LIGHT AND NO SIGNIFICANT DRY AIR MOVING IN AT
THE SFC...THE FOG IS EXPECTED TO THICKEN UP ONCE AGAIN AND EXPAND
A BIT IN COVERAGE.


&&

.HYDROLOGY...
ISSUED AT 300 PM EDT WED JUL 30 2014

NO MAJOR HYDROLOGY ISSUES EXPECTED. THE PRECIPITATION IS FORECASTED
TO BE SCATTERED.  AS A RESULT NOT MUCH BASIN AVERAGE RAINFALL
PREDICTED. WILL NEED TO MONITOR THE POSSIBLE WAVE FOR THU NIGHT
INTO FRI. TRENDS COULD SUPPORT A STEADIER RAIN EVENT.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LM...DENSE FOG ADVISORY UNTIL 11 AM EDT THURSDAY FOR LMZ844>846.

&&

$$

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






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