Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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000
FXUS63 KGRR 191818
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
218 PM EDT FRI SEP 19 2014

LATEST UPDATE...
AVIATION

.SYNOPSIS...
ISSUED AT 312 AM EDT FRI SEP 19 2014

HIGH PRESSURE OVER NEW ENGLAND WILL TRACK SLOWLY EAST TODAY.
SOUTHWEST WINDS AROUND THIS FAIR WEATHER SYSTEM WILL DRAW UP A
MILDER AIRMASS INTO MICHIGAN THROUGH TODAY. A COLD FRONT IN THE
UPPER PLAINS WILL TRACK THROUGH MICHIGAN SATURDAY INTO SATURDAY
NIGHT. THIS SYSTEM WILL BRING WITH IT A ROUND OF POTENTIALLY
STRONG THUNDERSTORMS. A COOLER AIRMASS WILL FILTER IN BEHIND THIS
COLD FRONT FOR SUNDAY.

&&

.SHORT TERM...(TODAY THROUGH SUNDAY)
ISSUED AT 312 AM EDT FRI SEP 19 2014

THE MAIN CHALLENGE IN THE SHORT TERM DEALS WITH THE POTENTIAL FOR
SEVERE WEATHER ON SATURDAY. OVERALL...CONFIDENCE IS HIGHER THAT WE
WILL SEE SOME SEVERE WEATHER.

DEEP LAYER SHEAR STRENGTHENS AS THE COLD FRONT PUSHES IN FROM THE
WEST SATURDAY AFTERNOON AND EVENING. THE SYSTEM RESPONSIBLE FOR
THE INCREASING WIND FIELDS WAS MOVING ONSHORE IN WESTERN CANADA
AND THE NW U.S. MODELS ARE FAIRLY SIMILAR IN TRACKING THIS SYSTEM
INTO THE GREAT LAKES REGION DURING THIS TIMEFRAME. THIS
STRENGTHENING SHEAR WILL ALLOW FOR ORGANIZED STORMS TO DEVELOP WITH
A POTENTIAL FOR DAMAGING WINDS AND LARGE HAIL. SOME UNCERTAINTY
EXISTS IN HOW MUCH INSTABILITY WE DEVELOP HERE IN SW MICHIGAN...OVERALL
THOUGH IT LOOKS LIKE THAT WILL END UP SUFFICIENT AS WELL. THE 0 TO
1 KM SHEAR AND HELICITY DO SUPPORT AND ELEVATED RISK FOR TORNADOES.
FORECAST SOUNDINGS FAVORED THE 18Z TO 02Z TIMEFRAME FOR THE
POTENTIAL SEVERE WEATHER. OVERALL I KEPT THE HIGH POPS GOING.

.LONG TERM...(SUNDAY NIGHT THROUGH THURSDAY)
ISSUED AT 312 AM EDT FRI SEP 19 2014

FAIR AND TRANQUIL WEATHER IS ANTICIPATED THROUGH THE LONG RANGE
FORECAST PERIOD AS A LARGE SFC HIGH PRESSURE RIDGE BUILDS IN. ANY
LINGERING SHOWERS ON SUNDAY SHOULD EXIT OUR AREA BY SUNDAY NIGHT AS
THE UPPER TROUGH AXIS MOVES FURTHER EAST.

TEMPERATURES WILL AVERAGE RATHER CLOSE TO NORMAL SUNDAY NIGHT
THROUGH MIDWEEK BEFORE UNDERGOING A GRADUAL MODERATING TREND LATE
NEXT WEEK.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SATURDAY AFTERNOON)
ISSUED AT 218 PM EDT FRI SEP 19 2014

SOUTH WINDS WILL BE PICKING UP THIS AFTERNOON WITH SOME GUSTS TO
20 KNOTS AT MKG THIS EVENING. VFR CONDITIONS SHOULD PREVAIL
OVERNIGHT AS WINDS WILL PREVENT FOG FROM FORMING. SOME SHOWERS OR
THUNDERSTORMS MAY ARRIVE FROM THE WEST SATURDAY MORNING BUT THE
STRONGER STORMS ARE EXPECTED TO ARRIVE AFTER 18Z.

&&

.MARINE...
ISSUED AT 312 AM EDT FRI SEP 19 2014

WILL ISSUE A SMALL CRAFT ADVISORY WITH THIS PACKAGE. WINDS AND
WAVES WILL INCREASE ESPECIALLY THIS AFTERNOON AND EVENING. BY
MIDNIGHT ALL ZONES WILL SEE SMALL CRAFT CONDITIONS. THE SOUTHERLY
FLOW SUPPORTS THE HIGHEST WAVES UP NORTH. THE GRADIENT WEAKENS
LATER SATURDAY AS THE LOW LEVEL JET PULLS AWAY. BY 00Z MOST
LOCATIONS SHOULD SEE CONDITIONS UNDER SMALL CRAFT CRITERIA.


&&

.HYDROLOGY...
ISSUED AT 312 AM EDT FRI SEP 19 2014

LOCALLY HEAVY RAIN WILL ACCOMPANY THE THUNDERSTORMS ESPECIALLY
SATURDAY AFTERNOON INTO THE EVENING. IT DOES NOT LOOK LIKE THE
STORMS WILL STALL OUT...THUS 1 TO 2 HR HEAVY RAIN DURATION IS THE
MOST LIKELY SCENARIO. THIS TYPICALLY LEADS TO URBAN AND POOR
DRAINAGE ISSUES IF ANY.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LM...SMALL CRAFT ADVISORY UNTIL 8 PM EDT SATURDAY FOR LMZ847>849.

     SMALL CRAFT ADVISORY FROM 11 PM THIS EVENING TO 8 PM EDT
     SATURDAY FOR LMZ844>846.

&&

$$

SYNOPSIS...MJS
SHORT TERM...MJS
LONG TERM...LAURENS
AVIATION...OSTUNO
HYDROLOGY...MJS
MARINE...MJS




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