Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 040508
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
108 AM EDT TUE AUG 4 2015

LATEST UPDATE...
AVIATION

.SYNOPSIS...
ISSUED AT 318 PM EDT MON AUG 3 2015

COOLER AIR HAS SETTLED BACK IN ACROSS THE AREA TODAY...AND WILL
REMAIN THROUGH MOST OF THE REST OF THE WEEK. MOST OF THE REMAINDER
OF THE WEEK WILL REMAIN DRY...EXCEPT FOR A CHANCE OF A RAIN SHOWER
ON TUESDAY AFTERNOON ACROSS INTERIOR PORTIONS OF CENTRAL LOWER
MICHIGAN TUESDAY. THERE IS ALSO A SLIGHT CHANCE OF A RAIN SHOWER ON
THURSDAY.

&&

.SHORT TERM...(THIS EVENING THROUGH WEDNESDAY NIGHT)
ISSUED AT 318 PM EDT MON AUG 3 2015

THE ONLY REAL CHALLENGES OF THE FCST ARE DETERMINING RAIN CHCS FOR
TUE...AND THEN AGAIN ON WED NIGHT.

WE WILL BE STARTING OUT WITH A DRY FCST FOR THIS EVENING. A FEW
SHOWERS...AND EVEN AN ISOLATED LIGHTNING STRIKE OCCURRED EARLIER
ACROSS THE ERN COUNTIES. THIS WAS ASSOCIATED WITH A SHORT WAVE THAT
WAS MOVING THROUGH...AND IS NOW EAST OF THE AREA. ANOTHER SHORT WAVE
WILL APPROACH FROM THE NW LATE TONIGHT ACROSS THE NORTH...BUT THIS
WILL NOT HAVE ANY DIURNAL INSTABILITY TO WORK WITH.

WE HAVE LEFT THE CHC OF RAIN SHOWERS ACROSS THE NE COUNTIES FOR THE
AFTERNOON HOURS ON TUE. WE WILL HAVE ONE MORE SHORT WAVE CLIP THE NE
CORNER OF THE CWFA WHILE THE JET CORE IS STILL IN OUR AREA. MID
LEVEL TEMPS WILL BE WARM ENOUGH TO LIMIT CLOUD DEPTH AND THUS
THUNDER POTENTIAL. THIS WAVE WILL PASS EAST OF THE AREA BY 00Z WED.

TUE NIGHT AND WED ARE LOOKING DRY...AND WE THINK THERE IS A GOOD CHC
THAT WED NIGHT WILL REMAIN DRY ALSO. SHORT WAVE RIDGING WILL BE IN
CONTROL FOR MOST OF THAT TIME FRAME. WED NIGHT THE GFS IS PHASING
NRN AND SRN STREAM ENERGY AND BRINGING A STRONGER SYSTEM THROUGH THE
STATE. WE BELIEVE THAT THE SYSTEMS WILL REMAIN UNPHASED...AND THE
BULK OF ANY PCPN WILL REMAIN WELL SOUTH OF THE AREA WED NIGHT. WE
HAVE HELD ON TO A SLIGHT CHC OF RAIN ALONG I-94 JUST IN CASE.

DAY TIME TEMPS WILL BE WELL INTO THE 70S WITH H850 TEMPS IN THE LOW
TO MID TEENS C. NIGHT TIME LOWS WILL BE MAINLY IN THE 50S WITH A
COOL AND DRY AIR MASS IN PLACE.

.LONG TERM...(THURSDAY THROUGH MONDAY)
ISSUED AT 318 PM EDT MON AUG 3 2015

MAIN CONCERN CONTINUES TO BE PRECIPITATION CHANCES ON THURSDAY.
SEVERAL MEDIUM RANGE MODELS AGREE THERE WILL BE AN UPPER POTENTIAL
VORTICITY MAXIMUM AND ASSOCIATED SURFACE LOW PRESSURE WAVE
TRAVERSING THE GREAT LAKES / OHIO VALLEY REGION DURING THIS TIME.

DIFFERENCES EXIST AMONG THE MODELS WITH THE TRACK OF THE WAVE AND
ASSOCIATED PRECIPITATION. THE 12Z ECMWF SHOWS PRECIPITATION
REMAINING MUCH FARTHER SOUTH OF THE AREA THAN THE 00Z RUN DID.
MEANWHILE THE GFS AND FIM SHOW THE FOCUS MUCH MORE CENTERED OVER THE
FORECAST AREA. FOR NOW...WE WILL USE A CONSENSUS FORECAST OF CHANCE
POPS FROM I-94 SOUTH. CERTAINTY REMAINS LOW EVEN INTO FRIDAY DUE TO
CONTINUED PHASING AND TIMING DIFFERENCES AMONG MODELS.

WHAT IS MORE CERTAIN IS DRY CONDITIONS THIS WEEKEND. AN UPPER RIDGE
JUST UPSTREAM OF THE FORECAST AREA SHOULD AMPLIFY AND BRING
TEMPERATURES BACK UP TO MORE SEASONAL VALUES.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z TUESDAY NIGHT)
ISSUED AT 108 AM EDT TUE AUG 4 2015

VFR CONDITIONS WILL CONTINUE THROUGH THE NEXT 24 HOURS. THERE WILL
BE OCCASIONAL MID CLOUDS WITH BASES OF 5-10K FT...BUT VSBYS ARE
EXPECTED TO REMAIN UNRESTRICTED.

MAIN AVIATION CONCERN SHOULD BE THE WESTERLY WINDS WHICH WILL
INCREASE TO 10-15 KNOTS BY ABOUT 16Z...THEN DIMINISH QUICKLY
AROUND 00Z.

&&

.MARINE...
ISSUED AT 318 PM EDT MON AUG 3 2015

WE ARE ANTICIPATING NO HEADLINES BEING NEEDED FOR THE NEXT FEW DAYS.
WINDS MAY PICK UP ONCE AGAIN A LITTLE BIT ON TUE...HOWEVER WE DO NOT
EXPECT THAT IT WILL BE ENOUGH TO WARRANT HEADLINES. BY WED...WINDS
WILL GO BACK TO BEING 15 KNOTS OR LESS WITH HIGH PRESSURE IN THE
AREA.


&&

.HYDROLOGY...
ISSUED AT 318 PM EDT MON AUG 3 2015

WE HAVE SEEN RIVERS AND STREAMS RISE A BIT TODAY AFTER THE
BENEFICIAL RAIN FELL LAST NIGHT ACROSS THE ENTIRE AREA. NO ISSUES
ARE NOTED WITH ALL RIVERS EXPECTED TO REMAIN WITHIN BANKFULL VALUES.
VERY LITTLE RAIN IS EXPECTED OVER THE NEXT FEW DAYS WITH A DRIER
PATTERN EXPECTED ONCE AGAIN.

&&

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

$$

SYNOPSIS...NJJ
SHORT TERM...NJJ
LONG TERM...TJT
AVIATION...JK
HYDROLOGY...NJJ
MARINE...NJJ


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