Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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000
FXUS63 KGRR 200725
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
325 AM EDT SAT SEP 20 2014

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

.SYNOPSIS...
ISSUED AT 324 AM EDT SAT SEP 20 2014

A STRONG STORM SYSTEM WILL BRING THUNDERSTORMS...WITH LOCALLY
HEAVY RAINFALL TO THE AREA TODAY INTO THIS EVENING. SOME STORMS
COULD BE SEVERE THIS AFTERNOON. ONCE THE COLD FRONT COMES THROUGH
EARLY TONIGHT... THE UPPER LEVEL SYSTEM WILL TRIGGER MORE SHOWERS
AN ISOLATED THUNDERSTORMS SUNDAY AFTERNOON. THE SYSTEM MOVES OUT OF
THE AREA MONDAY. THAT WILL RESULT IN A SLOW WARMING TREND THROUGH
THE REST OF THE WEEK WITH MOSTLY CLEAR CLEAR SKIES.

&&

.SHORT TERM...(TODAY THROUGH MONDAY)
ISSUED AT 324 AM EDT SAT SEP 20 2014

OF COURSE THE BIG QUESTION IS THE SEVERE WEATHER POTENTIAL FOR
THIS AFTERNOON AND EVENING. WE THEN HAVE THE ISSUE OF THE UPPER
LEVEL SYSTEM MOVING THROUGH THE AREA SUNDAY LIKELY RESULTING IN
MORE SHOWERS AND ISOLATED THUNDERSTORMS. CLEARING SHOULD FOLLOW
EARLY MONDAY AS THE SYSTEM MOVES OUT.

THIS AFTERNOON WE HAVE THE DEPARTING UPPER LEVEL JET ENTRANCE
REGION IN JUST THE CORRECT PLACE TO RESULT IN STRONG UPPER
DIVERGENCE OVER THE CENTRAL AND SOUTHERN CWA. WITH THE JET SO
CLOSE THE DEEP LAYER SHEAR IS OVER 40 KNOTS INTO TONIGHT. THE
JUXTAPOSITION OF THE UPPER LEVEL JET ENTRANCE REGION OF COURSE
WILL RESULT IN DEVELOPING LOW LEVEL JET OVER SOUTHERN AND CENTRAL
LOWER MICHIGAN EARLY TO MID AFTERNOON (SHOWN BY MOST OF THE
MODELS) AND GIVEN THE 1000 J/KG OF (MORE OR LESS) OF MU-CAPE... ONE
HAS TO BELIEVE THERE IS SOME POTENTIAL FOR SEVERE STORMS. CURRENTLY
IT SEEMS THE LINE WOULD FORM NEAR OR JUST SOUTH OF GRR EARLY TO
MID AFTERNOON AND INTENSIFY AS IT MOVES SOUTHEAST INTO OHIO AND
NORTHERN INDIANA THIS EVENING.

AS FOR THE LINE HEADING OUR WAY NOW... FROM WESTERN WISCONSIN THE
LOW LEVEL JET SUPPORTING THAT IS EXPECTED TO WEAK OVER TIME SO I
EXPECT ONLY RAIN SHOWERS TO REACH OUR NORTHWEST COUNTIES BY
SUNRISE. THIS OF COURSE WILL HAVE TO BE WATCHED CLOSELY AS THE
STORMS ARE DOING NICELY NOW.

OVERNIGHT INTO SUNDAY THE UPPER LOW MOVES THROUGH THE AREA. AFTER
10 PM OR SO WE GET THE JET EXIT REGION OF ANOTHER JET CORE. THAT
WILL LIKELY RESULT IN MORE SHOWERS AND ISOLATED THUNDERSTORMS
(NOT SEVERE SINCE THIS WILL BE LATE AT NIGHT). AS THE UPPER LEVEL
LOW MOVES OVER THE AREA SUNDAY... PLACES INLAND OF US-131 SHOULD
SEE SHOWERS AND THUNDERSTORMS INTO SUNDAY EVENING.

THE SYSTEM MOVES OF THE AREA EARLY MONDAY (JET CORE 0N THE WEST
SIDE OF THE SYSTEM MOVES OUT OF THE AREA). I EXPECT CLEARING AFTER
MIDNIGHT. WE MAY HAVE FROST HEADLINES EARLY MONDAY MORNING UP NORTH.

WITH THE SYSTEM TO OUR EAST MONDAY EXPECT MOSTLY SUNNY SKIES AND
PLEASANT TEMPERATURES FOR THIS TIME OF YEAR.


.LONG TERM...(MONDAY NIGHT THROUGH FRIDAY)
ISSUED AT 324 AM EDT SAT SEP 20 2014

FAIR AND TRANQUIL WEATHER IS ANTICIPATED THROUGH THE LONG RANGE
FORECAST PERIOD AS HIGH PRESSURE BUILDS IN. OVERALL MEDIUM RANGE
GUIDANCE TRENDS THE PAST SEVERAL DAYS ARE A LITTLE MILDER AND NOW
SUGGEST MAX TEMPS TUESDAY WILL REACH THE UPPER 60S TO LOWER 70S.

MAX TEMPS WEDNESDAY THROUGH FRIDAY SHOULD REACH THE 70 TO 75 DEGREE
RANGE AS SOUTHERLY FLOW GRADUALLY DEVELOPS ON THE BACK SIDE OF THE
SURFACE RIDGE. DRY WEATHER WILL LIKELY CONTINUE THROUGH NEXT WEEKEND.


&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SATURDAY NIGHT)
ISSUED AT 1145 PM EDT FRI SEP 19 2014

CHALLENGING SET OF TERMINAL FORECASTS WITH POTENTIAL FOR MULTIPLE
ROUNDS OF SHOWERS AND THUNDERSTORMS...ESPECIALLY AFTER 09Z. FIRST
ROUND OF SHOWERS SHOULD STAY MOSTLY ACROSS NORTHERN LOWER MICHIGAN
AND HAS A HIGH POTENTIAL TO RESULT IN SOME HAZARDOUS FLYING
CONDITIONS IN MUSKEGON FROM 06Z THROUGH 12Z BUT MODELS ARE
INDICATING THAT SHOWERS COULD BE EVEN NORTH OF MUSKEGON. HAVE
BACKED OFF ON VC MENTION SOUTH OF MUSKEGON AND LEFT -RA IN MKG
AFTER 09Z.

SECOND ROUND OF ACTIVITY WILL DEVELOP AFTER 15Z AND COULD RESULT
IN THUNDERSTORMS IMPACTING ALL TERMINAL FORECAST LOCATIONS ACROSS
SOUTHWEST LOWER MICHIGAN THROUGH THE END OF THIS TERMINAL FORECAST
PERIOD. CONFIDENCE REMAINS MODERATE IN THIS SECOND ROUND OF
ACTIVITY AT THIS TIME BUT ENOUGH CONFIDENCE IS THERE FOR VC AND
PROB30 MENTION OF TSRA. THUNDERSTORMS SHOULD CLEAR OUT AFTER 00Z
SUNDAY.


&&

.MARINE...
ISSUED AT 324 AM EDT SAT SEP 20 2014

LITTLE QUESTION WE NEED A SMALL CRAFT ADVISORY TODAY BUT WITH
GALES EXPECTED SUNDAY OVER THE NORTH 1/3 OF OUR NEAR SHORE IT
MADE MORE SENSE TO JUST TO CONTINUE TO THE SMALL CRAFT ADVISORY
OVERNIGHT TO KEEP THINGS SIMPLE. WINDS WILL UP AS HIGH AS 30 KNOT
FROM THE NORTH SUNDAY OVER THE ENTIRE NEAR SHORE SUNDAY NIGHT SO
I CONTINUED THE SMALL CRAFT ADVISORY INTO MONDAY MORNING.

&&

.HYDROLOGY...
ISSUED AT 324 AM EDT SAT SEP 20 2014

WHILE LOCALLY HEAVY RAINFALL IS MORE THAN POSSIBLE THIS AFTERNOON
INTO EARLY TONIGHT... MORE SO OVER THE SOUTHERN SECTIONS THAN NORTHERN
SECTIONS...RIVER LEVELS ARE LOW ENOUGH THAT LARGE SCALE FLOODING
SHOULD NOT BE AN ISSUE. THAT IS NOT TO SAY LOCALLY HEAVY RAINFALL
COULD RESULT IN LOCALIZED FLOODING AS PRECIPITABLE WATER VALUES
REACH AROUND 1.7 INCHES THIS EVENING. THAT HIGH OF A VALUE HAS A
RETURN PERIOD OF ONCE IN 2 YEARS THIS LATE IN SEPTEMBER.



&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LM...GALE WATCH FROM SUNDAY MORNING THROUGH SUNDAY EVENING FOR LM848-
     849.

     SMALL CRAFT ADVISORY UNTIL 11 AM EDT SUNDAY FOR LMZ848-849.

     SMALL CRAFT ADVISORY FROM 8 PM SUNDAY TO 8 AM EDT MONDAY FOR
     LMZ848-849.

     SMALL CRAFT ADVISORY UNTIL 8 AM EDT MONDAY FOR LMZ844>847.

&&

$$

SYNOPSIS...WDM
SHORT TERM...WDM
LONG TERM...LAURENS
AVIATION...MACZKO
HYDROLOGY...WDM
MARINE...WDM





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