Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 020725
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
325 AM EDT WED SEP 2 2015

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

.SYNOPSIS...
ISSUED AT 306 AM EDT WED SEP 2 2015

HIGH PRESSURE OVER THE LOWER OHIO VALLEY WILL CONTINUE TO DRAW AND
UNSEASONABLY WARM AIRMASS INTO THE GREAT LAKES REGION INTO
THURSDAY. A WEAK COLD FRONT WILL DROP DOWN FROM ONTARIO THURSDAY
INTO FRIDAY. AS A RESULT SHOWERS AND THUNDERSTORMS WILL INCREASE
ACROSS THE REGION LATER TONIGHT AND INTO THURSDAY.

&&

.SHORT TERM...(TODAY THROUGH FRIDAY)
ISSUED AT 306 AM EDT WED SEP 2 2015

SOME CONCERN THAT WE COULD SEE MORE WIDESPREAD SHOWER AND
THUNDERSTORM ACTIVITY LATER TONIGHT INTO THURSDAY. A MID LEVEL
SHORTWAVE MOVES IN FROM THE WEST NORTHWEST TONIGHT INTO THURSDAY.
AT THE SURFACE A BACKDOOR COLD FRONT DROPS DOWN. THE ATMOSPHERE IS
UNSTABLE AND REMAINS THAT WAY THROUGH THE PASSAGE OF THESE
FEATURES. GIVEN THE SHOWERS THAT POPPED UP RECENTLY TELLS ME THAT
THERE IS NOT MUCH HOLDING BACK THE CONVECTION IN THIS UNSEASONABLY
WARM AIRMASS. SO I RAISED POPS AND QPF FOR TONIGHT INTO THURSDAY.

WILL NEED TO MONITOR TEMPERATURE FORECASTS AS WELL. IF WE DO END
UP WITH A CONVECTIVE COMPLEX LATE TONIGHT INTO THURSDAY...OUR VERY
WARM TEMPERATURE FORECAST FOR THURSDAY COULD TOO HIGH.



.LONG TERM...(FRIDAY NIGHT THROUGH TUESDAY)
ISSUED AT 306 AM EDT WED SEP 2 2015

A CONSENSUS OF LATEST MEDIUM RANGE GUIDANCE CONTINUES TO SUGGEST
THAT VERY WARM AND HUMID WEATHER WILL CONTINUE THROUGH THE HOLIDAY
WEEKEND. MAX TEMPS DAILY WILL REACH THE 85 TO 90 DEGREE RANGE WITH
MIN TEMPS IN THE 60S. HUMIDITY LEVELS WILL REMAIN HIGH WITH DEW
POINT VALUES WELL INTO THE 60S TO AROUND 70 DEGREES.

MAINLY DRY WX IS ANTICIPATED FRIDAY NIGHT THROUGH SUNDAY WITH THE
UPPER LEVEL RIDGE IN PLACE. HOWEVER ISOLATED SHOWERS AND NON SEVERE
STORMS ARE POSSIBLE FROM TIME TO TIME AS SEVERAL WEAK UPPER LEVEL
DISTURBANCES MOVE THROUGH. THIS IN CONJUNCTION WITH SOME INSTABILITY
AND FORCING FROM MESOSCALE BOUNDARIES SUCH AS LAKE BREEZE
CONVERGENCE MAY BE SUFFICIENT ENOUGH TO CAUSE DEVELOPMENT OF
ISOLATED SHOWERS OR STORMS.

A COLD FRONT WILL BRING A RELATIVELY BETTER CHANCE FOR MORE
ORGANIZED SHOWERS AND STORMS LATE MONDAY THROUGH MONDAY NIGHT INTO
TUESDAY. HOWEVER THERE IS STILL SOME UNCERTAINTY AS TO TIMING AND
STRENGTH OF THAT FRONT. A SOMEWHAT COOLER AND LESS HUMID AIRMASS
SHOULD FINALLY MOVE IN FOR THE MIDDLE OF NEXT WEEK.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z WEDNESDAY NIGHT)
ISSUED AT 1154 PM EDT TUE SEP 1 2015

CONDITIONS WILL GRADUALLY DETERIORATE TO A MIX OF MVFR/IFR DURING
THE EARLY TO MID MORNING HOURS DUE TO DEVELOPMENT OF PATCHY FOG.
FOG WILL DISSIPATE DURING THE MID TO LATE MORNING HOURS WHEN
CONDITIONS WILL GRADUALLY IMPROVE TO MVFR THEN VFR FOR WEDNESDAY
AFTERNOON.

A FEW SHOWERS AND THUNDERSTORMS MAY DEVELOP FROM MID AFTERNOON
WEDNESDAY THROUGH WEDNESDAY EVENING. HOWEVER THERE IS NOT ENOUGH
POTENTIAL FOR RAIN OR THUNDERSTORMS TO WARRANT INCLUSION IN ANY OF
THE TERMINAL FORECASTS AT THIS TIME.


&&

.MARINE...
ISSUED AT 306 AM EDT WED SEP 2 2015

WINDS AND WAVES WILL REMAIN ON THE LOW SIDE DUE TO THE WEAK
PRESSURE GRADIENT THAT WILL BE IN PLACE. AN OFFSHORE FLOW DEVELOPS
ON THE BACKSIDE OF THE BACKDOOR COLD FRONT BY FRIDAY. THIS WILL
ACT TO KEEP THE WAVES LOW FOR OUR NEARSHORE WATERS. FOG COULD
BECOME AN ISSUE...AND LOCALLY HIGHER WINDS COULD ACCOMPANY THE
THUNDERSTORMS.

&&

.HYDROLOGY...
ISSUED AT 306 AM EDT WED SEP 2 2015

WILL NEED TO MONITOR THE QPF OVER THE NEXT FEW DAYS. THUNDERSTORMS
COULD LEAD TO LOCALLY HEAVY RAINFALL AS THE ATMOSPHERE WILL BE
UNSEASONABLY MOIST. SUCH RAINFALL COULD IMPACT SMALL STREAMS AND
POOR DRAINAGE AREAS.  IT WILL TAKE A LARGER COMPLEX OF STORMS TO
CAUSE THE RIVERS TO SEE STEADY RISES. THIS IS POSSIBLE LATER
TONIGHT INTO THURSDAY.

&&

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

$$

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



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