Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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000
FXUS63 KGRR 121611
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
1211 PM EDT SAT JUL 12 2014

LATEST UPDATE...
MARINE

.SYNOPSIS...
ISSUED AT 313 AM EDT SAT JUL 12 2014

SHOWERS AND THUNDERSTORMS WILL BE POSSIBLE TODAY...BUT THE BULK OF
THEM SHOULD HOLD UNTIL LATE THIS AFTERNOON.  THE SHOWERS AND STORMS
WILL THEN CONTINUE INTO TONIGHT...BEFORE DIMINISHING SUNDAY
MORNING.  PERIODS OF HEAVY RAIN WILL BE POSSIBLE TONIGHT INTO EARLY
SUNDAY MORNING MAINLY ALONG AND SOUTH OF I-96.  THERE IS ALSO THE
SLIGHT RISK FOR SEVERE STORMS TONIGHT...MAINLY SOUTHWEST OF GRAND
RAPIDS.  WE WILL GRADUALLY DRY OUT SUNDAY AFTERNOON AND SUNDAY
NIGHT.  THEN MORE SHOWERS AND A FEW THUNDERSTORMS WILL BE POSSIBLE
AGAIN ON MONDAY...MAINLY NORTH OF I-96.  DAYTIME TEMPERATURES WILL
BE AROUND 80 TODAY AND SUNDAY...THEN COOL TO 70 TO 75 BY MONDAY.

THE SHOWERS ARE EXPECTED TO MOVE OUT OF THE AREA MONDAY NIGHT WITH
COOLER AIR FILTERING IN.  HIGHS ON TUESDAY AND WEDNESDAY SHOULD ONLY
BE AROUND 70...BUT THEN WARM TO AROUND 80 FOR THURSDAY AND FRIDAY.

&&

.SHORT TERM...(TODAY THROUGH MONDAY)
ISSUED AT 313 AM EDT SAT JUL 12 2014

A COLD FRONT WAS JUST MOVING ACROSS THE MS RIVER EARLY THIS
MORNING...ALONG THE MN/WI BORDER.  MAIN MOISTURE FLUX AND LIFT WILL
STILL REMAIN TO OUR WEST MUCH OF THE DAY.  THEREFORE WILL LOWER POPS
AS THE MAIN FORCING DOES NOT ARRIVE UNTIL LATE AFTERNOON AND INTO
THIS EVENING.  WILL CARRY CHANCE POPS THROUGH MID AFTERNOON...THEN
RAMP THEM UP TO LIKELY AFTER 5 PM AS THE FRONT REACHES EASTERN
WISCONSIN BY THE END OF THE DAY.

TONIGHT CONTINUES TO LOOKS QUITE WET...ESPECIALLY ALONG AND SOUTH OF
I-96 WHERE DEEP MOISTURE POOLS AHEAD OF THE FRONT AND PERSISTS THERE
THROUGHOUT THE NIGHT.  PRECIPITABLE WATER VALUES CONTINUE TO BE NEAR
OR SLIGHTLY OVER 2 INCHES.  THOUGHT ABOUT ISSUING A FLOOD WATCH...
BUT NOT SURE HOW WIDESPREAD THE HEAVY RAIN WILL BE OR IF WE WILL
JUST SEE POCKETS OF HEAVY RAINS.  CONFIDENCE WAS NOT STRONG ENOUGH
AT THIS POINT.

THE RISK OF SEVERE STORMS APPEARS A BIT LESSEN NOW THAT THE LOW
LEVEL JET SEEMS TO ARRIVE AFTER 06Z...DURING AN INSTABILITY DOWNWARD
TREND BY THAT HOUR.  CAN NOT RULE OUT THAT A STRONGER STORM OR TWO
MAY MOVE ACROSS THE LAKE AND IMPACT AREAS ALONG AND SOUTH OF I-96.

THE FRONT AND THE BULK OF THE PCPN SHOULD MOVE OUT SUNDAY MORNING.
THERE IS A SECONDARY SURFACE TROUGH THAT PASSES THROUGH DURING THE
AFTERNOON AND MAY PRODUCE A FEW SHOWERS AND STORMS...PARTICULARLY SE
OF GRR.  THEN BY MONDAY AN UPPER LOW DROPS OVER THE U.P. THE
SOUTHERN CWA MAY BE DRY SLOTTED MUCH OF THE DAY...BUT WILL CARRY CHC
POPS ACROSS THE NORTH.  AFTER HIGHS AROUND 80 TODAY AND SUNDAY...
TEMPS WILL COOL TO 70 TO 75 MONDAY.

.LONG TERM...(MONDAY NIGHT THROUGH FRIDAY)
ISSUED AT 313 AM EDT SAT JUL 12 2014

AN UNUSUALLY CHILLY PERIOD OF WEATHER FOR MID JULY... IN SOUTHWEST
LOWER MICHIGAN... IS LOOKING MORE AND MORE LIKE WITH EACH MODEL RUN
THROUGH MOST OF THIS FORECAST TIME FRAME.  EXPECT AFTERNOON
INSTABILITY SHOWERS AND ISOLATED THUNDERSTORMS... MOSTLY INLAND OF
US-131 TUESDAY AND WEDNESDAY. A FEW ISOLATED SHOWERS REMAIN POSSIBLE
THURSDAY AFTERNOON TOO. THEN DRY WEATHER WITH A SLOW WARM UP WILL
COMMENCE.

THE ECMWF CONTINUES TO BE PREFERRED TO THE GFS SINCE THE CONTINUITY
OF THE ECMWF REMAINS SUPERIOR TO THE GFS.  THIS IS ESPECIALLY TRUE
IN THE MID LEVELS LIKE 700...500 AND 300 MB... THROUGH THIS FORECAST
PERIOD. THE ECMWF IS SLOWER TO EJECT THE UPPER LOW OVER THE GREAT
LAKES COMPARED TO THE GFS AND ECMWF CONTINUES TO BE SIGNIFICANTLY
FARTHER SOUTH WITH CENTER OF THE UPPER LEVEL LOW AS WELL.  IT SHOULD
BE POINTED OUT THE CANADIAN GEM IS SIMILAR TO THE ECMWF IN TERMS OF
THE DEVELOPMENT AND MOVEMENT OF THE DEEP 500 MB LOW OVER LOWER
MICHIGAN TUESDAY INTO WEDNESDAY.

WITH THE COLD POOL OF AIR ASSOCIATED WITH THE UPPER LOW REMAINING IN
PLACE TUESDAY INTO WEDNESDAY...AND LOOKING AT MODEL SOUNDING IT SURE
LOOKS TO ME LIKE THERE WOULD BE SCATTERED SHOWERS AND THUNDERSTORMS
AROUND THE AREA. TYPICAL OF THIS SORT OF SET UP IN THE SUMMER
TIME... SMALL HAIL IS CLASSIC CHARACTERISTIC OF THIS SORT OF
SCENARIO. ECMWF MODEL SOUNDING WOULD ALSO SUPPORT THIS (INTO
WEDNESDAY EVENING). BEYOND THAT THE UPPER LOW SLOWER MOVES EAST OF
THE AREA AND BY THURSDAY AFTERNOON THE BACK EDGE OF THE UPPER LEVEL
JET IS OVER LAKE MICHIGAN (ECMWF). SO I KEEP THE CHANCE OF SHOWERS
GOING INTO THURSDAY AFTERNOON SINCE WE WOULD STILL HAVE ENOUGH COLD
AIR ALOFT TO SPARK CONVECTION. I DID TREND THE POP DOWN EACH
AFTERNOON AS THAT IS ALSO TYPICAL OF THIS SORT OF EVENT. WATER
SPOUTS MAY BE POSSIBLE GIVEN HOW COLD THE AIR WILL BE AT MID LEVELS.

TEMPERATURES WILL RUN WELL BELOW NORMAL... AS MUCH AS 10 TO 15
DEGREES BELOW NORMAL FOR TUE AND WEDNESDAY. IT WOULD NOT BE OUT OF
THE QUESTION AREAS EAST OF REED CITY ALONG ROUTE 10 COULD SEE SOME
PATCHY FROST WED NIGHT AND THURSDAY NIGHT.  BY FRIDAY TEMPERATURES
WILL HAVE WARMED TO WITHING 5 DEGREES OF NORMAL.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z SUNDAY MORNING)
ISSUED AT 746 AM EDT SAT JUL 12 2014

CURRENTLY ALL TAF SITES ARE VFR AND SHOULD REMAIN SO THROUGH MID
AFTERNOON. CONDITIONS SHOULD DETERIORATE EARLY TONIGHT AND I WOULD
EXPECT LARGELY IFR/MVFR CONDITIONS AFTER 06Z AT ALL TAF SITES.

BASED ON BOTH THE HRRR IN COMBINATION WITH NAMDNG5 IT SEEMS THE
BULK OF THE THUNDERSTORMS ACTIVITY WILL BE IN THE 03Z TO 09Z TIME
FRAME. WHILE A FEW SCATTERED SHOWERS/THUNDERSTORMS (HRRR) COULD
IMPACT THE TAF SITES BY LATE AFTERNOON... THE UPPER DYNAMICS IN
COMBINATION WITH THE LOW LEVEL JET SUGGEST THE BULK OF THE STORM
ACTIVITY WILL BE AFTER 03Z SO ALL THE TAFS WERE WRITING TO SHOW
THE THUNDERSTORM ACTIVITY MOSTLY IN THAT TIME RANGE. SEEMS THESE
WILL BE TRAINING STORMS SO ONCE OVER THE TAF SITES THEY SHOULD NOT
BE QUICK TO LEAVE. IT IS AT THAT TIME THE CEILINGS/VSBY WILL
LIKELY GO MVFR/IFR. THE LOW CEILING/VSBY SHOULD CONTINUE THROUGH
12Z SUNDAY EVEN IF THE RAIN HAS ENDED BY THEN.


&&

.MARINE...
ISSUED AT 1206 PM EDT SAT JUL 12 2014

THE SOUTHERLY FLOW WILL KEEP THE WAVES GENERALLY IN THE 1 TO 3
FOOT RANGE WITH SOME VALUES UP NEAR 4 FEET BY THE TIME YOU GET TO
BIG SABLE POINT. OVERALL THE WINDS DO NOT STRENGTHEN...SO NO
HEADLINES AT THIS TIME. NEAR ANY THUNDERSTORMS...WINDS AND WAVES
COULD BE HIGHER.

&&

.HYDROLOGY...
ISSUED AT 249 PM EDT FRI JUL 11 2014

MAY NEED TO CONSIDER A FLOOD WATCH FOR SATURDAY AFTERNOON THROUGH
SUNDAY NIGHT. LOW LCLS...DEEP CAPE AND A DEEP WARM CLOUD LAYER
SUPPORT EFFICIENT RAINFALL PROCESS. LOCAL AMOUNTS WELL OVER 2 INCHES
POSSIBLE...ESPECIALLY IF THE STORMS TRAIN. CORFIDI DO BECOME SMALL
SAT NIGHT. THE OVERALL RISK WILL DEPEND ON HOW THE CONVECTION
UNFOLDS.

&&

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

$$

SYNOPSIS...JK
SHORT TERM...JK
LONG TERM...WDM
AVIATION...WDM
HYDROLOGY...MJS
MARINE...MJS






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