Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 201742
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
142 PM EDT WED AUG 20 2014

LATEST UPDATE...
AVIATION

.SYNOPSIS...
ISSUED AT 320 AM EDT WED AUG 20 2014

SKIES WILL BE PARTLY SUNNY TODAY AFTER AREAS OF DENSE FOG THIS
MORNING. THERE IS A CHANCE OF SHOWERS AND THUNDERSTORMS LATER
TODAY MAINLY EAST OF HIGHWAY 131. A STRONG WARM FRONT WILL BRING
POTENTIAL FOR THUNDERSTORMS THURSDAY NIGHT WITH VERY WARM AND
HUMID CONDITIONS AND SCATTERED SHOWERS AND STORMS EXPECTED
FRIDAY THROUGH THE WEEKEND.

&&

.SHORT TERM...(TODAY THROUGH FRIDAY)
ISSUED AT 320 AM EDT WED AUG 20 2014

AREAS OF DENSE FOG WILL GRADUALLY DEVELOP THROUGH THE EARLY MORNING
HOURS DUE TO GRADUAL CLEARING... LIGHT BOUNDARY LAYER WINDS AND
AMPLE LINGERING LOW LEVEL MOISTURE FROM THE RAINFALL YESTERDAY.

THE FOG IS NOT DENSE OR WIDESPREAD YET. HOWEVER GIVEN THESE
EXPECTATIONS FOR FOG TO BECOME MORE PREVALENT AND DENSER THROUGH
DAYBREAK WE WILL GO AHEAD AND HOIST A DENSE FOG ADVISORY FOR OUR
ENTIRE FCST AREA UNTIL 15Z. AFTER FOG GRADUALLY DISSIPATES DURING
THE MID TO LATE MORNING HOURS SKIES WILL BE PARTLY SUNNY WITH A
CHANCE OF SHOWERS AND THUNDERSTORMS MAINLY EAST OF US-131 THIS
AFTERNOON.

DRY WX IS ANTICIPATED TONIGHT ALTHOUGH THERE IS POTENTIAL FOR A
FEW SHOWERS OR ISOLATED STORMS TO MOVE INTO OUR FAR SW FCST AREA
TOWARD DAYBREAK THURSDAY. THERE IS A CHANCE FOR A FEW SHOWERS AND
STORMS THROUGH THE DAY THURSDAY BUT THE BETTER CHANCE FOR
CONVECTION WILL HOLD OFF UNTIL THURSDAY NIGHT DUE TO A STRONG WARM
FRONT AND FORCING FROM A 25 TO 35 KT LLJ. 1000-850 MB MOISTURE
TRANSPORT ALSO RAMPS UP THURSDAY NIGHT AND THERE IS POTENTIAL FOR
SOME HEAVY RAINFALL.

THERE IS STILL A CHANCE FOR A FEW LINGERING SHOWERS AND STORMS
INTO FRIDAY BUT A CONSENSUS OF LATEST SHORT RANGE GUIDANCE
SUGGESTS MOST OF THE DAY SHOULD BE DRY BUT VERY WARM AND HUMID.

.LONG TERM...(FRIDAY NIGHT THROUGH TUESDAY)
ISSUED AT 320 AM EDT WED AUG 20 2014

00Z MODEL GUIDANCE IS IN BETTER AGREEMENT TONIGHT AND SHOW UPPER
RIDGING ACROSS THE GREAT LAKES DURING THE PERIOD...WHICH WOULD LIMIT
SHOWER AND THUNDERSTORM ACTIVITY DESPITE PRESENCE OF INSTABILITY AND
SOME ISENTROPIC ASCENT. WENT WITH LOW OR SLIGHT POPS EVERY PERIOD
ALTHOUGH CHANCES COULD INCREASE TOWARDS THE END OF THE PERIOD WITH
HEIGHT FALLS AS THE RIDGING BEGINS TO FLATTEN AND THE WESTERN TROUGH
MOVES EAST.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z THURSDAY AFTERNOON)
ISSUED AT 142 PM EDT WED AUG 20 2014

LOWER CIGS AND VSBYS FROM EARLIER THIS MORNING HAVE LIFTED INTO
THE VFR CATEGORY EARLY THIS AFTERNOON. A FEW DIURNAL SHOWERS HAVE
POPPED MAINLY NE OF THE TERMINALS...CLOSEST TO KLAN. THESE WILL BE
POSSIBLE MAINLY AT KLAN THROUGH 20-22Z BEFORE THEY SHIFT EAST OF
THE AREA WITH THE WAVE THAT IS HELPING TO PRODUCE THEM.

LIGHT WINDS AND AT LEAST PARTLY CLOUDY SKIES ALONG WITH A MOIST
AIR MASS REMAINING WILL LEAD TO SOME POTENTIAL FOG ONCE AGAIN.
TOUGH TO TELL HOW DENSE IT WILL BE...HOWEVER MVFR SEEMS LIKELY
WITH IFR AND LOWER CONDITIONS POSSIBLE.

WE CAN NOT RULE OUT A SHOWER DEVELOPING OVERNIGHT TONIGHT AS WARM
AND MOIST AIR TRIES TO MAKE A RETURN. THE BETTER CHANCE WILL COME
ON THU...WHICH IS WHEN WE STARTED A VCSH MENTION.

&&

.MARINE...
ISSUED AT 320 AM EDT WED AUG 20 2014

MINIMAL WIND AND WAVE ACTION IS ANTICIPATED TODAY BUT AREAS OF FOG
WILL POSE A HAZARD TO MARINERS. VERY LITTLE WAVE ACTION IS
ANTICIPATED THROUGH THE END OF THE WEEK BUT AREAS OF FOG WILL
REMAIN A POSSIBILITY.


&&

.HYDROLOGY...
ISSUED AT 330 PM EDT TUE AUG 19 2014

HEAVY RAINFALL RATES OF 1-2 INCHES PER HOUR THROUGH EARLY EVENING
WILL SUPPORT A THREAT OF URBAN AND SMALL STREAM FLOODING. SCATTERED
NATURE OF THESE HEAVIER AMOUNTS SHOULD LIMIT EXTENT OF RISES ON THE
LARGER RIVERS. THE PATTERN LATER IN THE WEEK SUPPORTS ADDITIONAL
HEAVY RAINFALL EVENTS SO RIVER FLOODING COULD BECOME MORE OF A
CONCERN BY THAT TIME.

&&

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

$$

SYNOPSIS...LAURENS
SHORT TERM...LAURENS
LONG TERM...OSTUNO
AVIATION...NJJ
HYDROLOGY...MEADE
MARINE...LAURENS






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