Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 301842
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
242 PM EDT SAT AUG 30 2014

LATEST UPDATE...
SYNOPSIS/SHORT TERM/LONG TERM/HYDRO/MARINE

.SYNOPSIS...
ISSUED AT 220 PM EDT SAT AUG 30 2014

AN AREA OF LOW PRESSURE WILL TRACK NORTHEAST THROUGH THE GREAT
LAKES REGION THIS EVENING PRODUCING SCATTERED SHOWERS AND
THUNDERSTORMS. A WEAK AREA OF HIGH PRESSURE WILL MOVE IN FOR
SUNDAY WITH MAINLY A DRY AND WARM DAY EXPECTED. A COLD FRONT
PUSHES IN FROM THE WEST ON MONDAY. THIS SYSTEM COULD TRIGGER
STRONG TO SEVERE THUNDERSTORMS THAT WOULD PERSIST INTO THE EVENING.

&&

.SHORT TERM...(THIS EVENING THROUGH MONDAY NIGHT)
ISSUED AT 220 PM EDT SAT AUG 30 2014

THE MAIN CONCERN DEALS WITH THE POTENTIAL FOR SEVERE WEATHER
THIS AFTERNOON AND EVENING ALONG WITH ON MONDAY. SPC MESO PAGE
SHOWS SURFACE BASED CAPE VALUES AROUND 2000 J/KG AND MLCAPE VALUES
OF AROUND 1000 J/KG. ENOUGH INSTABILITY FOR STORMS TO DEVELOP
AIDED BY THE LIFT FROM AN APPROACHING MID LEVEL WAVE. EFFECTIVE
BULK SHEAR AROUND 35 KNOTS AND 0 TO 1 KM SHEAR AROUND 15 KNOTS.
SO A RISK FOR SEVERE WEATHER EXISTS WITH DAMAGING WINDS THE
PRIMARY RISKS...ALONG WITH A SMALL RISK FOR A TORNADO. SO FAR THE
CELLS HAVE STRUGGLED TO KEEP PERSISTENT UPDRAFTS...BUT THAT COULD CHANGE.
SLIGHT RISK CONTINUES.

STORMS WILL WEAKEN BY MIDNIGHT. LESS IN THE WAY OF CONVECTION
EXPECTED LATER TONIGHT THROUGH SUNDAY WITH NO REAL FORCING AROUND.
STILL SOME DAYTIME STORMS COULD POP UP ON SUNDAY GIVEN THE DECENT
HEATING.

STRONG TO SEVERE STORMS ARE A POSSIBILITY ON MONDAY. RIGHT
ENTRANCE REGION OF AN UPPER JET MOVES IN DURING THE DAY WITH
STRONGER INSTABILITY PRESENT. MODELS SHOW THE STRONGER DEEP LAYER
SHEAR ARRIVING IN THE EVENING. ITS POSSIBLE WE COULD SEE SCATTERED
TO NUMEROUS AFTERNOON STORMS DEVELOPING WITH A FEW SEVERE IN THE
AFTERNOON FOLLOWED BY THE ARRIVAL OF A WEAKENING SQUALL LINE
MOVING IN FROM WISCONSIN IN THE EVENING. TIMING WILL LIKELY
DETERMINE HOW MUCH IF ANY SEVERE WEATHER OCCURS. SLIGHT RISK FOR
PARTS OF THE REGION CONTINUES.



.LONG TERM...(TUESDAY THROUGH SATURDAY)
ISSUED AT 220 PM EDT SAT AUG 30 2014

MORE OF A ZONAL FLOW ARRIVES FOR THE MIDDLE OF NEXT WEEK. THIS
WILL SUPPORT WARMER TEMPERATURES. IT COULD BE UNSETTLED AS WELL
ESPECIALLY WEDNESDAY NIGHT INTO THURSDAY. HARD TO TIME INDIVIDUAL
SHORTWAVES GIVEN THE FAST FLOW THAT WILL BE PRESENT. WILL KEEP THE
RISK FOR SOME STORMS GOING THEN.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SUNDAY AFTERNOON)
ISSUED AT 145 PM EDT SAT AUG 30 2014

SCATTERED THUNDERSTORMS ARE EXPECTED...ESPECIALLY LATE THIS
AFTERNOON AND EARLY EVENING. THEN THE THREAT OF STORMS WILL BE
EXITING AROUND MIDNIGHT LOCAL TIME.

CONFIDENCE IN WIDESPREAD IFR LATE TONIGHT IN FOG WAS DIMINISHING
DUE TO THE ABUNDANT LOW CLOUDS THAT ARE EXPECTED TO REMAIN OVER
THE AREA. KEPT SOME IFR AROUND...BUT DID NOT HIT IT AS HARD. ANY
IFR SHOULD BE LIFTING OUT OF THE AREA BY LATE SUNDAY MORNING.


&&

.MARINE...
ISSUED AT 220 PM EDT SAT AUG 30 2014

BEACH HAZARDS AND SMALL CRAFT ADVISORIES CONTINUE. SOME GUSTS OVER
25 KNOTS ON THE LAKESHORE. WAVES STILL RUNNING 3 TO 5 FEET BUT
THEY WILL DIMINISH AS WITH WINDS SETTLE DOWN THIS EVENING.

&&

.HYDROLOGY...
ISSUED AT 220 PM EDT SAT AUG 30 2014

PWAT VALUES OVER 1.75 INCHES SUPPORT LOCALLY HEAVY RAIN. STORMS
HAVE BEEN MOVING QUICKLY AND THUS THE DURATION HAS BEEN LIMITED.
WITH SEVERAL ROUNDS OF STORMS POSSIBLE MONDAY INTO MONDAY
NIGHT...WILL NEED TO MONITOR THE HEAVY RAIN POTENTIAL ESPECIALLY
WITH PWAT VALUES UNSEASONABLY HIGH AND STRONGER FORCING MOVING IN.
ELEVATED RISK FOR LOCALLY EXCESSIVE RAIN EXISTS.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...BEACH HAZARDS STATEMENT UNTIL 11 PM EDT THIS EVENING FOR MIZ037-
     043-050-056-064-071.

LM...SMALL CRAFT ADVISORY UNTIL 11 PM EDT THIS EVENING FOR LMZ844>849.

&&

$$

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






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