Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 010342
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
1142 PM EDT THU JUL 31 2014

LATEST UPDATE...
AVIATION

.SYNOPSIS...
ISSUED AT 258 PM EDT THU JUL 31 2014

THE UPPER LOW THAT HAS BEEN CENTERED OVER ONTARIO THE PAST COUPLE
OF DAYS WILL SHIFT EAST. THIS WILL ALLOW FOR A MODERATING TREND TO
THE TEMPERATURES FOR THE END OF THE WEEK HERE IN MICHIGAN. A FEW MAINLY
AFTERNOON THUNDERSTORMS COULD DEVELOP FRIDAY AND SATURDAY...OTHERWISE
THE WEATHER WILL BE MAINLY DRY. THE MORE SEASONABLE TEMPERATURES
WILL PERSIST INTO EARLY NEXT WEEK.

&&

.UPDATE...
ISSUED AT 938 PM EDT THU JUL 31 2014

WE HAVE ADDED A SLIGHT CHANCE OF THUNDER TO THE NRN HALF OF THE
CWFA FOR THE NIGHT. A COUPLE OF SHOWERS AND STORMS HAVE DEVELOPED
OFFSHORE OF MUSKEGON IN THE PAST HOUR OR SO. OBVIOUSLY THESE ARE
NOT SFC BASED OVER THE COOLER WATERS OF LAKE MICHIGAN. THE SHORT
WAVE MOVING ACROSS THE NRN HALF OF WI AND LAKE MICHIGAN IS
INTERACTING WITH ELEVATED INSTABILITY WITH 925 MB BASED LI/S OF
-2. THIS SHORT WAVE IS NOT EXPECTED TO DROP SOUTH AND SHOULD ONLY
AFFECT THE NRN HALF OF THE CWFA. WITHOUT MUCH SHEAR AND WEAK
INSTABILITY...NO SEVERE WEATHER IS NOT EXPECTED.

&&

.SHORT TERM...(THIS EVENING THROUGH SATURDAY NIGHT)
ISSUED AT 258 PM EDT THU JUL 31 2014

THE MAIN CHALLENGE IN THE SHORT TERM DEALS WITH THE POTENTIAL FOR
SHOWERS AND THUNDERSTORMS EACH DAY. THE STORMS IN WISCONSIN ARE
EXPECTED TO DISSIPATE AS THEY TRY TO CROSS LAKE MICHIGAN. SURFACE
BASED PARCELS ARE STABLE WITH SHOULD CAUSE THE CONVECTION TO
WEAKEN. SATELLITE LOOPS SHOW THE CU ORGANIZING FROM NEAR BIG
RAPIDS TO LANSING AND DOWN TO BATTLE CREEK. WE COULD SEE A COUPLE
OF SHOWERS DEVELOP IN THIS REGION OVER THE NEXT HOUR OR TWO. GIVEN
THE GREATER THAN 1000 J/KG...A THUNDERSTORM CANNOT BE RULED OUT
EITHER. THE MOST LIKELY REGION FOR THIS TO HAPPEN WOULD BE EAST OF
A BIG RAPIDS TO KALAMAZOO LINE.

THE COMBINATION OF LOW LEVEL WARM AIR ADVECTION AND MID LEVEL COOL
AIR ADVECTION SUPPORT A HIGHER POTENTIAL FOR THUNDERSTORMS FRIDAY
AFTERNOON. BETTER THAN 1000 J/KG SURFACE BASED CAPE DEVELOPS. DEEP
LAYER SHEAR WILL BE WEAK. THUS ANY CONVECTION THAT DEVELOPS SHOULD
BE PULSE IN NATURE.  WILL KEEP THE THUNDER RISK GOING.

INSTABILITY DEVELOPS AGAIN ON SATURDAY. WINDS LOOK RATHER
LIGHT...SO GOOD SURFACE BASED HEATING EXPECTED. THE LAKE BREEZE
COULD BE FOCUSING MECHANISM FOR STORMS SATURDAY AFTERNOON. WILL
MAINTAIN THE LOW POP.

.LONG TERM...(SUNDAY THROUGH THURSDAY)
ISSUED AT 258 PM EDT THU JUL 31 2014

FORECAST CONCERNS CONTINUE TO CENTER AROUND THE MIDDLE OF NEXT WEEK.
A WEAK COLD FRONT WILL SLIP SOUTH ACROSS LAKE SUPERIOR MONDAY. A
WEAK WAVE OF LOW PRESSURE WILL MAY GENERATE A SHOWER OR STORM MID
DAY MONDAY. THE MAIN ISSUE WITH THE FRONT IS THAT IT IS PROGD TO
STALL OVER THE MIDDLE OF THE CWA MONDAY AFTERNOON DUE TO  A DEEPER
DEVELOPING LOW OVER THE NORTHERN PLAINS PUSHING WARMER AIR NORTHWARD
ON THE WEST END OF THE FRONT. SEVERAL SHORT WAVES ARE PROGD TO MOVE
ALONG THE BOUNDARY IN GENERAL NW FLOW ALOFT AND EACH WAVE WILL BRING
A CHANCE OF PCPN. AS THE MAIN LOW MOVES EAST WED-THU...HEAVIER RAIN
IS POSSIBLE ACROSS WISCONSIN AND CENTRAL LOWER MI. BOTH THE GFS AND
ECMWF HAVE BEEN SHOWING THIS SIGNAL FOR A FEW RUNS NOW. LLJ RAMPS UP
ACROSS WISCONSIN LATE WEDNESDAY AHEAD OF THE LOW AND AS A
RESULT...SHEAR VALUES INCREASE SUBSTANTIALLY. MAIN OPPORTUNITY FOR
SVR WX LOOKS TO BE IN THE WED/THU TIME FRAME.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z FRIDAY NIGHT)
ISSUED AT 1142 PM EDT THU JUL 31 2014

VFR CONDITIONS EXPECTED TO PREVAIL FOR MOST OF THE TAF PERIOD. A
FEW SHOWERS/THUNDERSTORMS TONIGHT ACROSS LOWER MICHIGAN. THEY
SHOULD CONTINUE TO TRACK NORTH OF MUSKEGON...GRAND RAPIDS AND
LANSING AND WILL LEAVE VICINITY MENTION OUT. FOG SHOULD BUILD AGAIN
INTO KMKG FRIDAY MORNING THOUGH VISIBILITIES SHOULD BE SLIGHTLY
BETTER THAN WHAT WAS EXPERIENCED THURSDAY MORNING WHEN BELOW 1
MILE VISIBILITIES WERE OBSERVED. OTHERWISE...SOME AFTERNOON AND
EVENING ISOLATED SHOWERS AND THUNDERSTORMS WILL BE POSSIBLE ESPECIALLY
KGRR TO KAZO AND POINTS TO THE EAST.

&&

.MARINE...
ISSUED AT 824 PM EDT THU JUL 31 2014

WE WENT AHEAD AND CANCELLED THE MARINE DENSE FOG ADVISORY A LITTLE
EARLY. WEB CAMS ON THE BUOYS AND ALONG THE COAST...ALONG WITH A
LACK OF SOLID FOG INDICATED ON THE VIS SATELLITE IMAGERY JUSTIFIED
THE CANCELLATION. SOME FOG WILL REMAIN POSSIBLE...HOWEVER WE ARE
NOT ANTICIPATING IT TO BECOME A SIGNIFICANT IMPACT AT THIS TIME.


&&

.HYDROLOGY...
ISSUED AT 258 PM EDT THU JUL 31 2014

BASIN AVERAGE QPF STAYS MINIMAL THROUGH THE END OF THE WEEK. THUS
NOT SIGNIFICANT RIVER RISES EXPECTED. ISOLATED STORMS COULD
LOCALLY PRODUCE UP TO A HALF INCH OF RAIN.

&&

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

$$

UPDATE...NJJ
SYNOPSIS...MJS
SHORT TERM...MJS
LONG TERM...93
AVIATION...MACZKO
HYDROLOGY...MJS
MARINE...NJJ





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