Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 220730
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
330 AM EDT FRI AUG 22 2014

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

.SYNOPSIS...
ISSUED AT 323 AM EDT FRI AUG 22 2014

A WARM WEEKEND IS IN STORE WITH MORNING FOG AND SOME SCATTERED
THUNDERSTORMS TODAY AND DRY WEATHER EXPECTED SATURDAY AND SUNDAY.
MONDAY WILL BE HOT WITH HIGHS IN THE UPPER 80S TO NEAR 90. A COLD
FRONT MOVES IN FOR MID WEEK WITH MUCH COOLER TEMPERATURES FOR THE
END OF THE WEEK AND LOWER HUMIDITY.


&&

.SHORT TERM...(TODAY THROUGH SUNDAY)
ISSUED AT 323 AM EDT FRI AUG 22 2014

PRECIP CHANCES AND FOG WILL BE THE MAIN ITEMS TO ADDRESS IN THE
SHORT TERM. OVERALL...PRECIP COVERAGE LOOKS TO BE SCATTERED TODAY
AND HAVE DROPPED POPS FOR SATURDAY AND SUNDAY ALTOGETHER...THOUGH A
FEW POP UP SHOWERS ARE NOT OUT OF THE QUESTION ON SATURDAY.

AREAS OF FOG ARE LIKELY THROUGH ABOUT 13Z TODAY GIVEN ABUNDANT LOW
LEVEL MOISTURE AND LARGELY CALM WINDS. LOW STRATUS WILL LIKELY
EXTEND INTO THE MORNING HOURS AND HAVE KEPT A RATHER CLOUDY FORECAST
IN THROUGH MID DAY. MANY AREAS WILL STAY MOSTLY CLOUDY FOR THE
ENTIRE DAY. PRECIP WISE...HAVE GONE WITH A SCATTERED WORDING TO
SHOWERS AND THUNDERSTORMS DURING THE DAY MAINLY NEAR AND SOUTH OF
I-96 WITH JUST ISOLATED ACTIVITY NORTH OF THERE. PLENTY OF
INSTABILITY IS IN PLACE NEAR/SOUTH OF I-96 WITH SB CAPE VALUES OVER
1000 J/KG AND LIFTED INDEX VALUES AROUND -3 WITH HALFWAY DECENT MID
LEVEL LAPSE RATES BETWEEN 7C/KM AND 8C/KM. DEW POINTS WILL CONTINUE
TO HOVER IN THE LOW 70S. PERHAPS SOME SOURCE OF LIFT WILL EVOLVE
DURING THE DAY WITH LIGHT EASTERLY WINDS ACROSS THE CENTRAL CWA
CONVERGING WITH LIGHT AND VARIABLE WINDS ACROSS THE LAKESHORE
COUNTIES AND LAKE MICHIGAN. BUT THIS ACTIVITY WON`T BE WIDESPREAD
AND THUS HAVE POPS NO HIGHER THAN 40% ACROSS THE FAR SOUTH INCLUDING
AZO AND JXN.

I WOULD ENVISION SATURDAY AND SUNDAY BEING COMPLETELY DRY FOR THE
CWA OUTSIDE OF A FEW POP UP SHOWERS ON SATURDAY. THIS THREAT IS
PROBABLY LOW ENOUGH TO OMIT FROM THE FORECAST. THE H500 RIDGE SHOULD
BE ALMOST DIRECTLY OVERHEAD BY 12Z SUNDAY. AS THIS PROGRESSES
IN...WE WILL BE CAPPED AND UNABLE TO FORM CONVECTION. THE HOT
TEMPERATURES WON`T ARRIVE BY SUNDAY IT APPEARS. H850 AND SFC WINDS
STAY EAST-SOUTHEASTERLY SATURDAY AND SUNDAY...PREVENTING THE REAL
WARMTH FROM GETTING INTO SW LOWER MI. MOST LOCATIONS STAY IN THE LOW
80S FOR HIGHS TODAY AND SATURDAY WHILE THE MID 80S WORK THEIR WAY IN
FOR SUNDAY.

&&

.LONG TERM...(SUNDAY NIGHT THROUGH THURSDAY)
ISSUED AT 323 AM EDT FRI AUG 22 2014

LONG TERM BEGINS WITH A VERY MID SUMMER LOOKING UPPER RIDGE
OVERHEAD. THE RIDGE BREAKS DOWN INTO MID WEEK AS THE SYSTEM LIFTING
NORTHEAST THROUGH THE PLAINS IN THE SHORT TERM CRESTS THE RIDGE AND
DAMPENS IT WITH TIME. WHAT THIS MEANS FOR US...IS HOT AND HUMID TO
BEGIN THE LONG TERM SUNDAY NIGHT INTO TUESDAY...WITH THE WEATHER
BECOMING MORE ACTIVE MID NEXT WEEK. AROUND 90 LOOKS PLAUSIBLE FOR
HIGHS BOTH MONDAY AND TUESDAY.

SHOWERS AND STORMS WILL BE MOST NUMEROUS FROM TUESDAY NIGHT THROUGH
WEDNESDAY NIGHT WHEN A FRONTAL BOUNDARY IS FORECAST TO MOVE THROUGH
THE AREA. SOME OF THE PRECIPITATION MAY LINGER INTO THURSDAY AS THE
BOUNDARY SLIDES SOUTH OF THE AREA.

DO NOT SEE MUCH IN THE WAY OF PRECIPITATION SUNDAY NIGHT INTO MONDAY
WITH THE MEAN RIDGE POSITION OVERHEAD. CHANCES FOR SHOWERS AND
STORMS (20/30 PCT) WILL CREEP IN FROM THE NORTHWEST MONDAY NIGHT
INTO TUESDAY...BUT FEEL THE BETTER CHANCES WILL HOLD OFF INTO MID
WEEK.

THE GFS IS MORE AMBITIOUS IN BRINGING TROUGHING INTO THE AREA
TOWARDS THE END OF THE FORECAST PERIOD AND THEREFORE COOLING THINGS
DOWN QUITE A BIT. AM A BIT MORE IN FAVOR OF THE LESS AMPLIFIED ECMWF
OUT AT THIS RANGE IN THE FORECAST.


&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z FRIDAY NIGHT)
ISSUED AT 1138 PM EDT THU AUG 21 2014

THE MAIN ISSUE FOR EARLY FRIDAY MORNING IS FOG AND LOW CLOUDS. THE
RAP MODEL SHOWS EXTENSIVE LOW CLOUDS FORMING BETWEEN 06Z AND 09Z
ACROSS ALL OF THE TAF SITES AS SURFACE EAST WINDS ARE OVERRUN BY
SOUTH WINDS ABOVE 4000 FT ALG. THAT WILL BRING MORE MOIST AIR OVER
THE SHALLOW COLDER LAYER AND RESULT AN EXTENSIVE LAYER OF LOW
CLOUDS. THE QUESTION IS WILL THERE BE DENSE FOG? WHILE NOT OUT OF
THE QUESTION THE AREA OF MID CLOUDS OVERHEAD TONIGHT WITH THE
LIKELY HOOD OF LOW CLOUD DECK WOULD SEEM TO MITIGATE DENSE FOG...
STILL IFR FOG WOULD STILL BE POSSIBLE. SINCE THE LOW AND MID LEVEL
WINDS DO NOT BECOME IN SINK UNTIL MIDDAY THE LOW CLOUDS COULD LAST
INTO THE AFTERNOON. SOME CLEARING OF THE LOW CLOUDS SHOULD MOVE
FROM EAST TO WEST AS THE THINNER CLOUDS MIX OUT FIRST. I WOULD
EXPECT VFR CONDITIONS MOST OF THE TAF SITES BY 18Z TO 21Z.


&&

.MARINE...
ISSUED AT 323 AM EDT FRI AUG 22 2014

MARINE FOG WILL BE THE PRIMARY PROBLEM FOR MARINERS NOW THROUGH
THE WEEKEND IT APPEARS. VERY HUMID CONDITIONS OVER A STILL COOL
LAKE MICHIGAN ALONG WITH MAINLY LIGHT WINDS WILL BE CONDUCIVE TO
AREAS OF FOG. WAVE ACTION WILL BE MINIMAL THROUGH THE WEEKEND.


&&

.HYDROLOGY...
ISSUED AT 323 AM EDT FRI AUG 22 2014

SIGNIFICANT PRECIPITATION IS NOT EXPECTED FOR THE NEXT SEVERAL
DAYS. SCATTERED THUNDERSTORMS TODAY ARE NOT ANTICIPATED TO PRODUCE
HEAVY RAINFALL AMOUNTS ON AVERAGE.


&&

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

$$

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






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