Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 241504
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
1104 AM EDT SUN AUG 24 2014

LATEST UPDATE...
HYDRO

.SYNOPSIS...
ISSUED AT 329 AM EDT SUN AUG 24 2014

IT WILL REMAIN VERY SUMMER-LIKE INTO TUESDAY.  HIGH TEMPERATURES
EACH DAY WILL BE IN THE 80S WITH A FEW TEMPERATURES AROUND 90 MONDAY
AND TUESDAY.  IT WILL BECOME QUITE HUMID MONDAY AND LINGER INTO
TUESDAY.  FOR THE MOST PART DRY CONDITIONS ARE EXPECTED...HOWEVER A
FEW WIDELY SCATTERED SHOWERS MAY OCCUR THIS MORNING WEST OF U.S.
131...AND A FEW SHOWERS OR STORMS ARE POSSIBLE INLAND NEAR HIGHWAY
127 EARLY THIS EVENING.  A BETTER CHANCE OF STORMS WILL COME MONDAY
NIGHT AND TUESDAY AS A COLD FRONT MOVES INTO THE REGION.

TEMPERATURES SHOULD COOL DOWN BY THURSDAY WITH DAYTIME HIGHS BACKING
DOWN INTO THE 70S.  THIS SHOULD HOLD INTO NEXT WEEKEND.  SHOWER AND
THUNDERSTORM CHANCES SHOULD CONTINUE THROUGH THURSDAY AS THE COLD
FRONT WORKS SLOWLY THROUGH THE AREA.

&&

.SHORT TERM...(TODAY THROUGH TUESDAY)
ISSUED AT 329 AM EDT SUN AUG 24 2014

A SHORT WAVE WAS WORKING SLOWLY EAST ACROSS LAKE MICHIGAN THIS
MORNING.  IT WAS RUNNING INTO THE UPPER RIDGE OVERHEAD...BUT WAS
STILL PRODUCING A FEW SHOWERS.  THE SHORT WAVE WILL CONTINUE TO
DAMPEN OUT AS THE RIDGE WORKS IT OVER...BUT I HAVE ADDED A CHANCE
FOR SHOWERS MAINLY WEST OF U.S. 131 THIS MORNING.  THE SHORT WAVE
WILL CONTINUE INLAND THROUGH THE AFTERNOON AND EVENING AND MAY WORK
WITH SOME OF THE DAYTIME INSTABILITY...SO ITS POSSIBLE A FEW SHOWERS
OR STORMS MAY DEVELOP NEAR HIGHWAY 127...BUT THESE TOO ARE EXPECTED
TO REMAIN ISOLATED.

A RATHER ILL-DEFINED WARM FRONT LIFTS NORTH THROUGH THE CWA LATE
TONIGHT.  AGAIN WE MAY SEE ISOLATED SHOWERS OR STORMS NEAR AND NORTH
OF THIS FRONT...BUT MOST AREAS SHOULD STAY DRY.

WINDS TURN TO THE SOUTH BEHIND THIS FRONT BY MONDAY AND THIS WILL
USHER IN MORE HEAT AND HUMIDITY THAT WILL LINGER INTO TUESDAY.
EXPECT MID 80S TO AROUND 90 FOR HIGHS EACH DAY.  HEAT INDEX READINGS
WILL BE IN THE 90S MONDAY...THEN MAINLY 90 TO 95 TUESDAY WITH A BIT
MORE CLOUD COVER.

A WEAKENING FRONT WILL BE CROSSING WISCONSIN ON MONDAY...LAKE
MICHIGAN MONDAY NIGHT...THEN CROSSING THE HEART OF THE CWA ON
TUESDAY.  IT GRADUALLY BECOMES MORE ALIGNED WITH THE UPPER FLOW...SO
IT WILL BE A SLOW MOVER.  SLIGHTLY BETTER CHANCES OF SHOWERS AND
STORMS WILL MOVE IN BY MONDAY NIGHT AND TUESDAY.  HOWEVER NOT SEEING
MUCH JET DYNAMICS WITH THE FRONT...SO THE PCPN SHOULD REMAIN WIDELY
SCATTERED.  LOCALIZED HEAVY RAIN WILL BE POSSIBLE AS THE MID LEVEL
STEERING WINDS REMAIN WEAK AND SOME CELLS COULD ALSO TRAIN.  HOWEVER
SEVERE POTENTIAL APPEARS LOW AT THIS POINT.

.LONG TERM...(TUESDAY NIGHT THROUGH SATURDAY)
ISSUED AT 329 AM EDT SUN AUG 24 2014

STILL QUITE A BIT OF MODEL DISPARITY IN THE LONG TERM PERIOD...WHICH
LEADS TO A LOW CONFIDENCE FORECAST. FORECAST DETAILS HINGE ON THE
EVOLUTION OF THE PATTERN...WHICH WILL BE DRIVEN BY THE SHORTWAVE
DIVING SOUTH ALONG THE BRITISH COLUMBIA COAST INTO THE WESTERN
TROUGH THIS MORNING. THE GFS HOLDS ONTO THIS ENERGY A BIT MORE AND
BRINGS A DECENT TROUGH INTO THE AREA LATER THIS WEEK. THE ECMWF IS
WEAKER AND SLOWER WITH THIS FEATURE.

THE GFS IS SOMEWHAT OF AN ODD MODEL OUT IN THE DEEPER TROUGH AS
THE CANADIAN GEM LENDS CREDENCE TO THE ECMWF. THAT SAID...AS STATED
ABOVE THIS IS LOW CONFIDENCE AND HAVE SOME BROAD BRUSHED LOW POPS
(20-30 PCT) THROUGH MOST OF THE LONG TERM PERIOD. CHANCES ARE
THERE...JUST DIFFICULT TO PIN DOWN THE DETAILS. FEEL THE BEST
CHANCES FOR PRECIP WILL LIKELY BE TUESDAY NIGHT AS THE BOUNDARY
TRIES TO SHIFT THROUGH THE AREA AND AGAIN TOWARDS THE END OF THE
WEEK...FRIDAY INTO SATURDAY.

HIGH TEMPERATURES THROUGH THE PERIOD SHOULD BE FAIRLY CLOSE TO
NORMAL IN THE UPPER 70S EACH DAY.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z MONDAY MORNING)
ISSUED AT 747 AM EDT SUN AUG 24 2014

AT 12Z CONDITIONS RANGE FROM IFR AT THE EASTERN TAF SITES (KJXN
AND KLAN) TO VFR AT KMKG. EXPECT A SLOW TREND UP IN CONDITIONS THIS
MORNING WITH MOST SITES LIKELY TO BE VFR BY EARLY AFTERNOON. SOME
MVFR CEILINGS MAY TRY TO HANG ON THOUGH. SCATTERED SHOWERS AND
EVEN AN ISOLATED THUNDERSTORM WILL BE POSSIBLE TODAY...ALTHOUGH
ONLY FELT CONFIDENT ENOUGH TO INCLUDE VCSH WORDING IN THE TAFS AT
THIS POINT.

THE MOIST LOW LEVEL SOUTHEAST FLOW WILL CONTINUE TONIGHT AND
INCLUDED MVFR CONDITIONS DEVELOPING ONCE AGAIN...BOTH CEILINGS AND
VSBY/S. OVERALL CONFIDENCE IS LOW IN THE FORECAST GIVEN THE VERY
CHANGEABLE CONDITIONS.


&&

.MARINE...
ISSUED AT 329 AM EDT SUN AUG 24 2014

RATHER QUIET CONDITIONS ARE EXPECTED OVER THE NEARSHORE WATERS.
OFFSHORE EAST OR SOUTHEAST FLOW WILL PREVAIL FOR THE NEXT 24
HOURS.  WINDS WILL TURN TO THE SOUTH AND SOUTHWEST MONDAY AND
TUESDAY BUT SHOULD REMAIN LIGHT ENOUGH TO WAVES 2 FEET OR LESS.


&&

.HYDROLOGY...
ISSUED AT 1104 AM EDT SUN AUG 24 2014

BEST CHANCE FOR SIGNIFICANT RAINFALL WOULD BE MONDAY NIGHT THROUGH
WEDNESDAY WITH A SLOW MOVING COLD FRONT. THIS IS NOT A GUARANTEE
AS THE LLJ IS FORECAST TO BE QUITE WEAK. NEVERTHELESS...A VERY
MOIST ATMOSPHERE COMBINED WITH FORCING VIA THE COLD FRONT AND SLOW
CELL MOVEMENT COULD RESULT IN SOME SIGNIFICANT RAINFALL IF STORMS
DEVELOP OVER OUR AREA. PW VALUES WILL LIKELY BE AROUND 1.75"
MONDAY NIGHT AND TUESDAY. MODEL GUIDANCE IS MIXED REGARDING HOW
LONG THE FRONT MAY HANG UP...SO IT IS UNCLEAR WHEN THE THREAT FOR
SIGNIFICANT RAINFALL WOULD END.


&&

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

$$

SYNOPSIS...JK
SHORT TERM...JK
LONG TERM...DUKE
AVIATION...DUKE
HYDROLOGY...HOVING
MARINE...JK





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