Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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000
FXUS63 KGRR 121746
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
146 PM EDT FRI SEP 12 2014

LATEST UPDATE...
AVIATION

.SYNOPSIS...
ISSUED AT 324 AM EDT FRI SEP 12 2014

COOL WEATHER WILL CONTINUE INTO THE WEEKEND. WEAK LOW PRESSURE
WILL BRING SOME SHOWERS LATE TODAY THROUGH TONIGHT. THE HIGH
PRESSURE BUILDS IN FOR SATURDAY AND SUNDAY. SOME FROST IS EXPECTED
NORTH OF GRAND RAPIDS SATURDAY NIGHT.

&&

.SHORT TERM...(THIS AFTERNOON THROUGH SUNDAY EVENING)
ISSUED AT 1121 AM EDT FRI SEP 12 2014

LITTLE QUESTION THERE WILL BE RAIN ACROSS THE CWA TONIGHT THANKS A
CLOSING OFF UPPER LOW. THE BEST DYNAMICS ARE OVER CENTRAL AND
NORTHERN LOWER MICHIGAN... SO THAT IS WHERE IT BELIEVE THE HEAVIEST
RAIN WILL BE. NEARLY ALL OF OUR CWA WILL GET RAIN FROM THIS
SYSTEM. BASED ON THE LATEST HRRR AND LOOKING AT CONDENSATION
PRESSURE DEFICITS FROM THE NAM 12Z RUN... IT WOULD SEEM THE RAIN
MAY START AS EARLY AS 3-4 PM NEAR ROUTE 10 BUT NOT REACH I-96 TILL
NEAR US-131 BY 8-9 PM. I UPDATED THE GRIDS TO REFLECT THIS TIMING.

AS A SIDE NOTE SEEMS WE WILL GET A NORTH TO SOUTH MID LAKE
ENHANCED PRECIPITATION BAND BUT THAT SHOULD STAY OFF SHORE THROUGH
THE NIGHT DUE TO THE NORTH WINDS DURING THE EVENT TONIGHT. HOWEVER
THE BAND MAY TOUCH PARTS OF EXTREME WESTERN MASON COUNTY TOWARD
MORNING. IF IT DOES EXPECT A PERIOD OF HEAVIER RAIN SHOWERS.

.LONG TERM...(SUNDAY NIGHT THROUGH THURSDAY)
ISSUED AT 324 AM EDT FRI SEP 12 2014

THE FOCUS OF THE LONG TERM IS CENTERED ON THE MON/MON NIGHT TIME
FRAME WHEN OUR BEST CHC FOR PCPN WILL BE.

THE DRY WEATHER FOR THE LATTER HALF OF THE UPCOMING WEEKEND WILL
GRADUALLY COME TO AN END LATE SUN NIGHT AND MON ACROSS THE AREA. WE
WILL SEE A COLD FRONT DROP INTO THE AREA AT THAT TIME AS A LONG WAVE
TROUGH ACROSS CENTRAL AND EASTERN CANADA SLIPS SOUTH INTO THE AREA.
PCPN ALONG THE FRONT IS INITIALLY A BIT SPARSE...HOWEVER THIS LOOKS
TO CHANGE AS A STRONG SHORT WAVE ROUNDING THE BASE OF THE LONG WAVE
TROUGH WILL INTERACT WITH THE FRONT ON MON AND MON EVENING.

RAIN WILL COME TO AN END ACROSS THE ENTIRE AREA BY 12Z TUE AS THE
SHORT WAVE TROUGH AXIS MOVES EAST OF THE CWFA. DRY WEATHER IS THEN
LIKELY TO HOLD FOR THE REMAINDER OF THE WEEK. WE WILL SEE A COOL NW
FLOW HOLD IN ACROSS THE AREA FOR THE REMAINDER OF THE WEEK. THE GOOD
THING IS THAT WE WILL BE IMMEDIATELY DOWNSTREAM FROM THE LONG WAVE
UPPER RIDGE AXIS ACROSS THE ROCKIES. THE SUBSIDENCE DOWNSTREAM FROM
THE RIDGE WILL KEEP THE WEATHER QUIET AND COOL. THE RIDGE GETS
FLATTENED A BIT BY THE END OF THE PERIOD AS ENERGY DIVING SOUTH FROM
CANADA TRIES TO MOVE IN. THE UPPER JET WILL REMAIN NORTH OF THE AREA
AND WILL HOLD A COLD FRONT ACROSS LAKE SUPERIOR UP THERE.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SATURDAY AFTERNOON)
ISSUED AT 146 PM EDT FRI SEP 12 2014

AS MENTIONED IN THE PREVIOUS DISCUSSION...EXPECT MVFR CIGS TO
SPREAD SOUTHEAST THIS AFTERNOON AND TONIGHT WITH AN AREA OF MOSTLY
LIGHT RAIN. ALTHOUGH NOT ADVERTISED AT ALL OF THE TERMINALS...
CEILINGS COULD DROP BELOW THE FUEL ALTERNATE THRESHOLD OF 2000 FT
AGL. IFR CEILINGS ARE ALSO NOT OUT OF THE QUESTION AT MKG AFTER
06Z. OVERALL...THERE ARE FEWER CONCERNS ABOUT RESTRICTIONS TO
VISIBILITY.

&&

.MARINE...
ISSUED AT 1121 AM EDT FRI SEP 12 2014

I ADDED WATER SPOUTS TO THE NEAR SHORE FORECAST FROM LATE
AFTERNOON INTO MID MORNING SATURDAY BASED ON THE CONVECTIVE DEPTH
BEING BETWEEN 10000 FT AND 15000 FT AT MID LAKE... USING LAKE
TEMP TO 850 TEMP DIFFERENCES BETWEEN 15C AND 18C. WINDS WILL NOT BE
STRONG ENOUGH FOR SCA. IN SUPPORT OF THAT...BEACH CAMS AT 11 AM SHOW
LITTLE IN THE WAY OF SIGNIFICANT WAVE ACTION. THE PORT SHELDON HAS
SHOWN 1 TO 1.3 FOOT WAVES OVER THE PAST SEVERAL HOURS.


&&

.HYDROLOGY...
ISSUED AT 324 AM EDT FRI SEP 12 2014

NO HYDRO ISSUES EXPECTED.

&&

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

$$

SYNOPSIS...OSTUNO
SHORT TERM...WDM
LONG TERM...NJJ
AVIATION...TJT
HYDROLOGY...OSTUNO
MARINE...WDM



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