Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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000
FXUS63 KGRR 142305
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
705 PM EDT SUN SEP 14 2014

LATEST UPDATE...
AVIATION

.SYNOPSIS...
ISSUED AT 327 PM EDT SUN SEP 14 2014

LIGHT RAIN SHOWERS WILL MOVE INTO AREAS NORTH OF I-96 LATE
TONIGHT...THEN SPREAD INTO SOUTHERN LOWER MICHIGAN ON MONDAY AND
BECOME STEADIER.  RAIN IS EXPECTED MUCH OF MONDAY WITH THE RAIN
EXITING FROM WEST TO EAST LATE MONDAY AFTERNOON AND INTO THE
EVENING.  HIGH PRESSURE ARRIVES LATER MONDAY NIGHT GIVING THE REGION
A DRY PERIOD INTO TUESDAY NIGHT.  IT WILL REMAIN COOL WITH DAYTIME
HIGHS BOTH MONDAY AND TUESDAY ONLY 60 TO 65...WHICH IS ABOUT 10
DEGREES BELOW NORMAL.

MUCH OF THE REMAINDER OF THE WEEK APPEARS TO BE DRY...WITH THE NEXT
CHANCE OF RAIN HOLDING OFF UNTIL FRIDAY NIGHT INTO NEXT WEEKEND.
TEMPERATURES WILL MODERATE...WARMING TO 65 TO 75 FOR THE LATTER PART
OF THE WEEK.

&&

.SHORT TERM...(THIS EVENING THROUGH TUESDAY NIGHT)
ISSUED AT 327 PM EDT SUN SEP 14 2014

A STEADIER/HEAVIER RAIN IS NOW EXPECTED FOR MONDAY AS A COLD FRONT
COMES THROUGH ALONG WITH GOOD JET DYNAMICS AND FGEN FORCING.

FAVORABLE FGEN FORCING DEVELOPS OUT AHEAD OF THE COLD FRONT BY LATE
THIS EVENING.  EXPECT A SLIGHTLY QUICKER ONSET TO THE PCPN SO ADDED
POPS TO THE NW CWA STARTING THIS EVENING.  WE WILL HAVE TO OVERCOME
SOME FAIRLY DRY LOW LEVELS...SO THESE INITIAL SHOWERS SHOULD WILL BE
LIGHT.  THE LIGHT SHOWERS SHOULD SPREAD EAST AS THE FGEN EXPANDS
OVER THE AREAS NORTH OF I-96 LATE TONIGHT.

THE FGEN FORCING TONIGHT WILL PRIME THE LOW LEVELS WITH MOISTURE AND
SHOULD MAKE THE COLD FRONT THAT COMES IN ON MONDAY THAT MUCH MORE
PROFICIENT.  WE WILL ALSO SEE THE RIGHT ENTRANCE REGION OF THE UPPER
JET AND A WEAK LOW LEVEL JET COME ACROSS THE SE HALF OF THE CWA
MONDAY AFTERNOON.  INCREASED POPS ACROSS THE ENTIRE CWA TO
CATEGORICAL AND ALSO INCREASED QPF AMOUNTS TO AROUND OR SLIGHTLY
OVER
A QUARTER INCH.

THE SHOWERS WILL LIGHTEN UP AND EXIT QUICKLY MONDAY EVENING FROM
WEST TO EAST AS THE FRONT AND UPPER DYNAMICS EXIT.  SKIES SHOULD AT
LEAST PARTIALLY CLEAR AND THERE COULD BE THE RISK OF ISOLATED FROST
OVER THE INTERIOR NORTH...BUT IT DOES NOT APPEAR IT WILL BE
WIDESPREAD ENOUGH TO WARRANT A HEADLINE.

TUESDAY WILL BE QUIET AND WILL BECOME MOSTLY SUNNY.  TEMPS SHOULD
BE SLIGHTLY WARMER.  ANOTHER COLD FRONT IS PROGGED TO DROP SOUTH
INTO NORTHERN LOWER TUESDAY NIGHT.  THIS LOOKS LIKE A PRETTY WEAK
FRONT...BUT THE CLOUDS SHOULD INCREASE ACROSS THE NORTHERN CWA WITH
MAYBE SOME SPRINKLES TOWARD HIGHWAY 10.

.LONG TERM...(WEDNESDAY THROUGH SUNDAY)
ISSUED AT 327 PM EDT SUN SEP 14 2014

VERY LITTLE IMPACTS EXPECTED DURING THIS PERIOD AS INITIALLY
NORTHWEST FLOW ALOFT GRADUALLY TRANSITIONS TO ZONAL FLOW AND WARMING
TEMPERATURES. MODELS SHOWING SOME CONSISTENCY WITH SHOWERS AND
THUNDERSTORMS SPREADING INTO THE AREA EARLY SATURDAY AND EXITING
SUNDAY. THE LATEST 12Z ECMWF SHOWS A HASTIER EXIT SUNDAY THAN THE
00Z RUN...SO TIMING THE END OF PRECIPITATION IS PROBABLY THE BIGGEST
FORECAST CHALLENGE AT THIS POINT.

AS NOTED IN THE PREVIOUS DISCUSSION...HIGHS IN THE 70S ARE EXPECTED
LATE WEEK INTO THE WEEKEND AHEAD OF THIS SYSTEM.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z MONDAY EVENING)
ISSUED AT 705 PM EDT SUN SEP 14 2014

LITTLE QUESTION SKIES WILL BE CLEAR TO MOSTLY CLEAR EARLY TONIGHT.
THIS IS BASED ON VISIBLE AND IR SATELLITE LOOPS (CLEARING OVER WI
AND LOWER MICHIGAN BETWEEN 21Z AND 23Z. I ALSO LOOKED AT RAP/NAM
MODEL SOUNDINGS WHICH SHOWED THE MOIST LAYER SUPPORTING THE
STRATOCUMULUS CLOUDS THAT WERE AROUND TODAY MIXING OUT BY 00Z.

LATER TONIGHT THE COMBINATION OF A DIGGING UPPER LEVEL JET DIVING
INTO THE DAKOTAS AND A DEPARTING JET EXITING OVER LOWER MICHIGAN
WILL RESULT IN ONE OF THOSE "JET LIFT" EVENTS OVER OUR TAF SITES
MONDAY. THE CLOUDS ARE ALREADY SEEN OVER SOUTHERN MINNESOTA...
IOWA...SOUTH DAKOTA AND NEBRASKA. THIS WILL BRING MID /HIGH
CLOUDS INTO THE TAF SITES AFTER 06Z AND LOWER CLOUDS WITH RAIN
WILL FOLLOW BETWEEN 15Z AND 18Z. THE HEAVIEST RAIN WILL LIKELY BE
NEAR AND NORTH OF MKG MONDAY AFTERNOON.


&&

.MARINE...
ISSUED AT 327 PM EDT SUN SEP 14 2014

WAVES WILL CONTINUE TO BUILD LATE THIS AFTERNOON INTO THIS EVENING
WITH A BRISK SW FLOW.  SMALL CRAFT ADVISORY CONDITIONS ARE EXPECTED
FOR THE REST OF TODAY AND LINGER INTO MID MORNING ON MONDAY NORTH OF
HOLLAND.  THEREAFTER WINDS AND WAVES LIGHTEN UP AS A COLD FRONT
COMES IN...FOLLOWED BY HIGH PRESSURE INTO TUESDAY NIGHT.


&&

.HYDROLOGY...
ISSUED AT 327 PM EDT SUN SEP 14 2014

MOST AREAS SHOULD SEE AROUND A QUARTER INCH OF RAIN FROM LATE
TONIGHT INTO MONDAY EVENING.  RIVERS ARE RUNNING A BIT HIGHER THAN
NORMAL...BUT THIS AMOUNT OF RAIN SHOULD NOT AFFECT THEM TOO MUCH.
EXPECT A MOSTLY DRY PERIOD TUESDAY THROUGH FRIDAY.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LM...SMALL CRAFT ADVISORY UNTIL 10 AM EDT MONDAY FOR LMZ846>849.

&&

$$

SYNOPSIS...JK
SHORT TERM...JK
LONG TERM...TJT
AVIATION...WDM
HYDROLOGY...JK
MARINE...JK





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