Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 261525
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
1125 AM EDT FRI JUN 26 2015

LATEST UPDATE...
UPDATE

.SYNOPSIS...
ISSUED AT 328 AM EDT FRI JUN 26 2015

A FALL LIKE STORM WILL TRACK SOUTH MICHIGAN TODAY THEN TURN
NORTHWARD INTO THE EASTERN AND CENTRAL GREAT LAKES TONIGHT INTO
SATURDAY. THIS WILL MEAN CONSIDERABLE CLOUDINESS TODAY INTO
TONIGHT WITH SEASONABLY COOL TEMPERATURES. THE NEXT SYSTEM WILL
COME INTO THE PICTURE LATER SUNDAY WITH A CHANCE OF SHOWERS AND
THUNDERSTORMS. THOSE WILL CONTINUE INTO MONDAY.

&&

.UPDATE...
ISSUED AT 1125 AM EDT FRI JUN 26 2015

INCREASED POPS A BIT...ESPECIALLY OVER THE SW PORTION OF THE CWA.
LIGHT SHOWERS WERE CROSSING NORTHERN IL THIS MORNING AND THESE
SHOULD REACH THE SW CORNER OF MICHIGAN THIS AFTERNOON. INSTABILITY
WILL INCREASE TOO SO A FEW THUNDERSTORMS WILL BE POSSIBLE. EXPECT
MOST OF THE PCPN WILL STAY SW OF A WHITEHALL-GRR-JXN LINE. NE OF
THIS LINE THE DRIER AND MORE STABLE NE FLOW SHOULD KEEP IT MOSTLY
DRY TODAY.

&&

.SHORT TERM...(TODAY THROUGH SUNDAY)
ISSUED AT 328 AM EDT FRI JUN 26 2015

WE WILL BE WATCHING TWO CONCERNS TODAY. FIRST IS THE POTENTIAL
FOR LATE DAY SHOWERS AND ISOLATED THUNDERSTORMS ON THE LAKE
BREEZE BOUNDARY. SECOND IS THE TRACK OF THE FALL LIKE STORM THAT
IS FORECAST TO TRACK ACROSS LAKE ERIE SATURDAY EVENING.

AN UNUSUALLY AMPLIFIED UPPER AIR PATTERN FOR LATE JUNE IS
FORECAST AS A DIGGING NORTHERN STREAM WAVE CURVES OUT A DEEP UPPER
LEVEL TROUGH OVER THE GREAT LAKES SATURDAY THAT IS FORECAST TO
CONTINUE WELL INTO NEXT WEEK.

TYPICAL OF THESE TYPE OF DEEPENING SYSTEMS...THE TRACK IS THE KEY
TO KNOWING HOW FAR WEST THE PRECIPITATION WILL BE. THE LATEST RUN
OF THE GFS AND NAM SHOW THE SYSTEM FARTHER EAST. HOWEVER IT SHOULD
BE NOTED THE LATEST ECMWF IS NOW SIGNIFICANTLY FARTHER WEST WITH
THE TRACK AND PRECIPITATION ASSOCIATED WITH THE SYSTEM. SINCE WE
HAVE A TRAILING SHORTWAVE TO HELP FARTHER DEEPEN THE TROUGH
(COMES INTO THE GREAT LAKES LATE IN THE WEEKEND AND EARLY NEXT
WEEK) ONE HAS TO WOUNDER OF THE SECOND SYSTEM WILL FORCE A MORE
WESTERLY TRACK WITH THE LEAD SYSTEM. FOR NOW I WENT WITH THE
LATEST GFS/NAM RUNS BUT I AM CONCERNED THEY ARE TO FAR EAST WITH
THE WEST EDGE OF THE SIGNIFICANT RAIN TONIGHT INTO SATURDAY.

THE OTHER ISSUE IS LAKE BREEZE CONVECTION THIS AFTERNOON. THERE IS
ENOUGH INSTABILITY FOR SCATTERED LATE DAY CONVECTION THIS
AFTERNOON ON THE LAKE BREEZE. THE ONLY REAL QUESTION IS WILL THE
EASTERLY LOW LEVEL FROM THE DEVELOPING SYSTEM BE TO STRONG FOR A
LAKE BREEZE TO EVEN DEVELOP. JUST IN CASE I HAVE LOW CHANCE POPS
OVER OR WESTERN CWA THIS AFTERNOON AND EARLY EVENING.

AS FOR SUNDAY... I BELIEVE THE NAM IS TO FAST WITH BRINGING THE
NEXT SYSTEM INTO OUR STATE.... SO I WENT WITH THE GFS/ECMWF TIMING
...WHICH KEEPS IT DRY HERE TILL SUNDAY NIGHT.

.LONG TERM...(SUNDAY NIGHT THROUGH THURSDAY)
ISSUED AT 328 AM EDT FRI JUN 26 2015

THE ANTICIPATED UPPER AIR PATTERN CHANGE IS EXPECTED TO BE IN PLACE
BY THE BEGINNING OF THE LONG TERM ON SUN NIGHT. WE WILL HAVE SEEN
THE STRONG DEVELOPING SYSTEM EARLY IN THE WEEKEND SHIFT NORTH AND
EAST BY SUN NIGHT...LEAVING A BROAD TROUGH IN PLACE WITH THE FLOW
GENERALLY FROM THE NW.

IN THIS NW FLOW ALOFT...WE WILL SEE OCCASIONAL SHORT WAVES MOVING
THROUGH THE AREA BRINGING CHCS OF PCPN ALONG WITH COOLER WEATHER.
THE FIRST OF THESE WAVES WILL BE DIVING SE JUST WEST OF THE AREA SUN
NIGHT. THIS THEN LOOKS TO HEAD EAST ON MON. WE WILL BE CLOSE ENOUGH
TO THIS DECENT WAVE AND ASSOCIATED SFC LOW THAT SHOWERS AND A FEW
STORMS WILL BE PRESENT ACROSS THE AREA.

THE SHOWER CHCS WILL REMAIN INTO TUE...BUT WILL TEND TO TAPER OFF IN
COVERAGE DURING THE DAY ON TUE. THE SUN NIGHT/MON SYSTEM WILL SHIFT
EAST OF THE AREA WITH SHORT WAVE RIDGING BUILDING IN FOR A SHORT
TIME. TUE LOOKS LIKE THE PCPN CHCS WILL BE MORE OF THE POP UP/
DIURNALLY DRIVEN KIND.

THE TREND FOR PCPN CHCS SEEM TO BE TRENDING LOWER FOR THE WED-THU
TIME FRAME. WE WILL REMAIN IN THE NW FLOW ALOFT...WITH THE POTENTIAL
OF WEAK SHORT WAVES MOVING ACROSS THE AREA BRINGING A FEW
SHOWERS/STORMS. PREVIOUS MODEL RUNS...ESPECIALLY OF THE ECMWF HAD A
FRONTAL SYSTEM STALLED OUT OVER THE AREA WITH SOME HEALTHY RAINS
POSSIBLE. THE TREND HAS BEEN FOR THE CONSENSUS OF MODEL DATA TO PUSH
THE FRONT FURTHER SOUTH...AND KEEP THE RICHER MOISTURE AND
HEAVIER PCPN FURTHER SOUTH.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z SATURDAY MORNING)
ISSUED AT 719 AM EDT FRI JUN 26 2015

EXCEPT FOR JXN...ALL TAF SITES ARE CURRENTLY VFR. JXN IS LIFR IN
DENSE FOG. THE FOG SHOULD QUICKLY LIFT AT JXN AND THUS ALL TAF
SITES SHOULD BE VFR TODAY AND TONIGHT. ISOLATED LAKE BREEZE
CONVERGENCE SHOWERS AND THUNDERSTORMS ARE POSSIBLE THIS AFTERNOON
AT MKG...GRR AND AZO.

ON SATURDAY...IF THAT BIG STORM TRACKS A TOUCH FATHER WEST...THE
I-96 TAF SITES MAY YET SEE RAIN TOMORROW WITH MVFR/IFR CIGS.


&&

.MARINE...
ISSUED AT 328 AM EDT FRI JUN 26 2015

WE WILL HAVE TO WATCH JUST HOW FAR WEST THAT SYSTEM GETS SATURDAY.
IF IT DOES GO FARTHER WEST WE MAY NEED MARINE HEADLINES.


&&

.HYDROLOGY...
ISSUED AT 321 PM EDT WED JUN 24 2015

SEVERAL RIVER FLOOD ADVISORIES REMAIN IN EFFECT AS RUNOFF FROM HEAVY
RAIN ON MONDAY MAKES ITS WAY THROUGH THE RIVER SYSTEM. OFF AND ON
RAIN CHANCES ARE POSSIBLE THROUGH THE WEEKEND. SCATTERED SHOWERS ARE
ONGOING THIS AFTERNOON AND WILL REMAIN POSSIBLE THROUGH EVENING.
SOME ISOLATED STORMS WILL BE POSSIBLE OVER THE NEXT FEW
HOURS...WHICH COULD ENHANCE RAINFALL LOCALLY. HOWEVER...MAINLY
LIGHTER AMOUNTS CAN BE EXPECTED THROUGH TONIGHT...MAINLY AN
ADDITIONAL 0.10 TO 0.25 INCHES FROM THE SCATTERED RAIN SHOWERS.

ADDITIONAL RAINFALL WILL BE POSSIBLE MAINLY ACROSS THE SOUTHEAST
PORTION OF THE FORECAST AREA FRIDAY NIGHT THROUGH SATURDAY.
SIGNIFICANT FLOODING IS NOT EXPECTED. MINOR FLOODING ALONG RIVERS
AND IN LOW-LYING AREAS MAY PERSIST THROUGH THE WEEKEND.

&&

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

$$

UPDATE...JK
SYNOPSIS...WDM
SHORT TERM...WDM
LONG TERM...NJJ
AVIATION...WDM
HYDROLOGY...EBW
MARINE...WDM


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