Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 231905
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
305 PM EDT SAT AUG 23 2014

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

.SYNOPSIS...
ISSUED AT 305 PM EDT SAT AUG 23 2014

WARM AND DRY WEATHER WILL PREVAIL THROUGH THE REST OF THE WEEKEND
THANKS TO HIGH PRESSURE SITUATED OVER SOUTHERN ONTARIO. A RISK OF
SHOWERS AND THUNDERSTORMS WILL DEVELOP MONDAY NIGHT OR TUESDAY THEN
LINGER THROUGH MUCH OF THE WEEK AS A FRONTAL BOUNDARY LEANS IN FROM
THE WEST THEN STALLS OVER THE REGION. MONDAY AND TUESDAY WILL BE THE
WARMEST DAYS OF THE WEEK WITH HEAT INDICES IN THE LOW TO MID 90S.

&&

.SHORT TERM...(THIS EVENING THROUGH MONDAY NIGHT)
ISSUED AT 305 PM EDT SAT AUG 23 2014

REGARDING THE APPROACHING CONVECTION ACROSS ILLINOIS AND
WISCONSIN... WHILE THIS LOOKS RATHER CONVINCING... BELIEVE THAT SOME
THICKER MID LEVEL CLOUDS AND LIGHT SHOWERS OR SPRINKLES
MAINLY WEST/SOUTHWEST OF GRR SHOULD BE ABOUT THE WORST CASE SCENARIO
LATER THIS AFTERNOON/EVENING. THIS ACTIVITY WILL BE ENCOUNTERING
MUCH MORE STABLE CONDITIONS OVER LWR MI RELATED TO EASTERLY FLOW.
ALSO THE UPR RIDGE IS BUILDING OVERHEAD AND THE UPR FLOW SHOULD
CAUSE IT TO SHEAR OUT.

WITH THE SURFACE RIDGE BECOMING BETTER ESTABLISHED WE HAVE SEEN SFC
DEW POINTS FALL A BIT IN THE EASTERLY FLOW TODAY. THE DRIER AIR MASS
SHOULD MAKE THE FOG/STRATUS THREAT SOMEWHAT LESS TONIGHT... WITH THE
HIGHEST CHANCE OF THAT PROBABLY EAST OF HIGHWAY 131 CLOSER TO THE
EFFECTS OF LAKE HURON.

SEEMS PRETTY STRAIGHTFORWARD THAT DRY WEATHER WILL PREVAIL SUNDAY
AND SUNDAY NIGHT WITH THE HIGH AMPLITUDE UPPER RIDGE IN PLACE. WILL
HAVE CHC POPS FOR SHOWERS AND TSTMS STARTING MONDAY AFTERNOON
NORTHWEST OF GRR AS THE UPR RIDGE FLATTENS OUTS AND THE SFC FRONT
LEANS IN. THEN CHC POPS AREAWIDE ON MONDAY NIGHT AS THE FRONT LAYS
OUT ACROSS THE AREA.

.LONG TERM...(TUESDAY THROUGH SATURDAY)
ISSUED AT 305 PM EDT SAT AUG 23 2014

THE LONG TERM PORTION OF THE FCST HAS BECOME MORE UNCERTAIN OVER THE
PAST COUPLE OF DAYS AS THE EVOLUTION OF AN UPPER WAVE IS IN
QUESTION. WE HAVE ADDED MORE CHCS OF PCPN TO THE PERIOD FROM THU
THROUGH SAT FOR NEXT WEEK.

NOT MUCH CHANGE IN GENERAL FOR THE TUE-WED TIME FRAME. OUR UPPER
RIDGE IN PLACE THIS WEEKEND WILL GET FLATTENED BY THE UPPER LOW THAT
IS EXPECTED TO TAKE SHAPE OVER THE WRN U.S. AS IT LIFTS NE NORTH OF
LAKE SUPERIOR. THIS WILL FORCE A COLD FRONT DOWN INTO THE AREA. THIS
WILL BRING CHCS OF SHOWERS AND STORMS WITH GRADUALLY COOLER AIR.

THE UNCERTAINTY COMES DURING THE THU THROUGH SAT TIME FRAME. A
COUPLE OF DAYS AGO...IT LOOKED LIKE THE FRONT WOULD MOVE THROUGH AND
CLEAR THINGS OUT FOR THE AREA. NOW...ADDITIONAL JET ENERGY COMING IN
BEHIND THE LOW LIFTING INTO CANADA WILL INTERACT WITH STALLED OUT
FRONT AND KEEP THE THREAT FOR PCPN IN LONGER. WE ARE NOT SURE WHERE
THE FRONT WILL SETTLE IN AND THEN WHERE THE BEST THREAT OF PCPN WILL
END UP. THIS DEPENDS ON THE SECONDARY TROUGH AND HOW STRONG/
PROGRESSIVE IT ENDS UP.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SUNDAY AFTERNOON)
ISSUED AT 142 PM EDT SAT AUG 23 2014

MAIN CONCERN FOR THE 18Z FCSTS IS LOW CLOUDS AND FOG TRENDS. WE
ARE ALSO WATCHING CONVECTION WELL WEST OF THE AREA ACROSS WRN IL
AND SW WI.

SOME FOG EARLIER THIS MORNING HAS DISSIPATED. STRATUS DID MOVE SW
AND IMPACTED KAZO AND KBTL...BUT IS NOW ON ITS WAY OUT. WE EXPECT
SOME DIURNAL CUMULUS CLOUD COVER...BUT IT SHOULD BE MAINLY VFR
EXCEPT SW OF KAZO.

LINE OF STORMS CURRENTLY WEST OF KORD ARE SLOWLY ADVANCING TO THE
E AND SE. THEY ARE STARTING TO SHOW SIGNS OF WEAKENING...AND WE
EXPECT THAT MOST OF THIS SHOULD REMAIN WEST OF OUR AREA TOWARD THE
BETTER INSTABILITY...AND IN FACT START MOVING TO THE SE WITH NW
FLOW ALOFT STILL IN PLACE. WE WILL CONTINUE TO MONITOR THE LINE IN
CASE IT TRIES TO MAKE IT FURTHER EAST THAN EXPECTED.

FOG AND LOW CLOUDS HAVE TO BE CONSIDERED AGAIN TONIGHT. MOST OF
THE STRATUS THIS MORNING WAS ASSOCIATED WITH MOISTURE COMING FROM
LAKE HURON WITH A NE LOW LEVEL FLOW. THE FLOW SHOULD BE MORE ERLY
TONIGHT...SO THE EFFECTS FROM LAKE HURON SHOULD NOT BE AS MUCH OF
AN ISSUE. WE DO HAVE FEW004 TO ACCOUNT FOR SOME POSSIBLE STRATUS
FLOATING AROUND. IF AND WHEN WE ARE MORE CONFIDENT OF IT
OCCURRING...WE WILL ADJUST THE FCST ACCORDINGLY.

&&

.MARINE...
ISSUED AT 305 PM EDT SAT AUG 23 2014

THE THREAT OF MARINE FOG HAS DIMINISHED OVER THE NEARSHORE WATERS
AND SHIFTED OVER TO THE OTHER SIDE OF THE LAKE DUE TO OFFSHORE FLOW.
ALSO WARMER WATER TEMPERATURES NEAR 70 ARE NOW PRESENT. THE FOG
THREAT COULD RETURN AGAIN MONDAY AND TUESDAY AS WINDS COME AROUND TO
THE SOUTHWEST ALTHOUGH THE WARMER WATER TEMPS MAY MAKE IT LESS
LIKELY THAN WITH PREVIOUS FOG EVENTS WHICH OCCURRED AFTER UPWELLING
COOL DOWNS.

&&

.HYDROLOGY...
ISSUED AT 305 PM EDT SAT AUG 23 2014

THERE ARE NO HYDRO CONCERNS IN THE SHORT TERM BUT A RISK OF HEAVY
RAINFALL COULD DEVELOP FOR TUESDAY THROUGH THURSDAY AS A FRONTAL
BOUNDARY STALLS IN THE AREA WITH PWATS NEAR 2 INCHES. THERE COULD BE
SEVERAL ROUNDS OF SHOWERS AND TSTMS DURING THIS TIMEFRAME.

&&

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

$$

SYNOPSIS...MEADE
SHORT TERM...MEADE
LONG TERM...NJJ
AVIATION...DUKE
HYDROLOGY...MEADE
MARINE...MEADE









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