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000
FXUS63 KGRR 121804
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
204 PM EDT WED JUN 12 2013

LATEST UPDATE...
UPDATE

.SYNOPSIS...
ISSUED AT 330 AM EDT WED JUN 12 2013

AS LOW PRESSURE MOVES EAST FROM THE PLAINS TOWARD NORTHERN INDIANA
TODAY SHOWERS AND THUNDERSTORMS WILL DEVELOP. SOME OF THE STORMS
COULD BE STRONG TO SEVERE ESPECIALLY SOUTH OF I-94 WITH HIGH WINDS
THE MAIN THREAT. HEAVY RAIN WILL BE POSSIBLE THIS AFTERNOON AND
EVENING TOO SOUTH OF I-96. QUIETER WEATHER WILL RETURN THURSDAY
THROUGH SATURDAY AS THE LOW MOVES EAST AND NORTH WINDS ADVECT DRIER
AIR INTO LOWER MICHIGAN.

&&

.UPDATE...
ISSUED AT 203 PM EDT WED JUN 12 2013

I HAVE ISSUED A FLASH FLOOD WATCH BASED ON THE POTENTIAL FOR HEAVY
RAIN WITH THE TROWAL FEATURE NORTH OF THE MAIN UPPER LEVEL WAVE
AS IT COMES THROUGH TONIGHT. THE SPC SREF...THE 15Z HRRR AND THE
15Z ESRL RAP MODELS ALL SHOW 2 TO 3 INCHES OF RAIN TONIGHT JUST
SOUTH OF INTERSTATE 96. GIVEN THE CONVECTIVE NATURE OF THE EVENT
IT WOULD SEEM REASONABLE THAT FLASH FLOODING IS POSSIBLE IN THIS
AREA.

IT STILL LOOKS LIKE THE STRONG THUNDERSTORMS WILL CROSS OUR AREA
AFTER 10 PM TONIGHT AND THOSE STORMS WOULD SEEM TO WANT TO TRACK
SOUTH OF INTERSTATE 94. STILL THERE WOULD BE A LARGE AREA OF HEAVY
RAIN NORTH OF THAT... MAYBE AS FAR NORTH AS INTERSTATE 96.

&&

.SHORT TERM...(TODAY THROUGH FRIDAY)
ISSUED AT 330 AM EDT WED JUN 12 2013

FORECAST CONCERNS DEAL WITH CONVECTIVE TRENDS THIS MORNING THROUGH
THIS EVENING.

LATEST REGIONAL RADAR SHOWS THAT STORMS HAVE FIRED AS EXPECTED IN
NORTHEAST NEBRASKA ON THE NOSE OF A STRONG LLJ. THESE STORMS HAVE
MOVED INTO NW IOWA. A BIT FARTHER NORTH OVER SOUTH DAKOTA ANOTHER
AREA OF STORMS IS MOVE EWD. THESE ARE ASSOCIATED WITH A SHORT WAVE
MOVING ACROSS THE NRN PLAINS. SHORT RANGE MODELS MOVE THIS SHORT
WAVE SEWD TOWARD CHICAGO BY THIS AFTERNOON AT THE SAME TIME THE SFC
LOW IN SRN NEBRASKA IS MOVING ENEWD. HRRR SHOWS BOTH CLUSTERS OF
STORMS WEAKENING AS THEY MOVE EAST WITH THE IOWA CONVECTION MOVING
TO THE WRN CWA BY NOON OR SO AS MOSTLY SHOWERS.

CONVECTION REDEVELOPS OVER NW IOWA BY EARLY AFTERNOON AS STRONG
DYNAMICS TAKE SHAPE. SBCAPE AROUND 3K J/KG COUPLED WITH STRONG
MOISTURE CONVERGENCE...60-70KTS BULK SHEAR AND LIFT FROM THE
APPROACHING SHORT WAVE SHOULD RESULT IN STRONG TO SEVERE STORMS
DEVELOPING OVER ILLINOIS AND MOVING ESE TOWARD THE SRN CWA. A 50KT
MID LEVEL JET WILL PUSH THE STORMS EWD...PERHAPS AS A DERECHO. CAN/T
ARGUE TOO MUCH WITH THE POSITION OF THE DAY ONE SLIGHT AND MODERATE
RISK AREAS. THIS ISN/T A SLAM DUNK BY ANY MEANS BUT THE HIGHEST
THREAT FOR STRONG/SVR STORMS WILL BE SOUTH OF A MUSKEGON TO LANSING
LINE. LATEST NAM ALSO PUSHES THE WARM FRONT INTO THE SRN CWA THIS
AFTERNOON. SO...WITH THE WARM FRONT IN PLACE WE CAN/T RULE OUT A
TORNADO EITHER.

THE SVR THREAT WILL END THIS EVENING AS THE LOW MOVES BY TO THE
SOUTH AND QUIETER WEATHER WILL RETURN THURSDAY AND FRIDAY.

.LONG TERM...(FRIDAY NIGHT THROUGH TUESDAY)
ISSUED AT 330 AM EDT WED JUN 12 2013

UPPER RIDGING WILL EXTEND FROM THE GULF COAST NORTH INTO THE UPPER
MID WEST FRIDAY NIGHT. THE RIDGING WILL BE FLATTENED THROUGH THE
LONG TERM AS A SERIES OF SHORTWAVE/S CREST THE RIDGE AND MOVE
THROUGH THE GREAT LAKES REGION. THE FIRST OF WHICH MOVES INTO THE
AREA ON SATURDAY. THE SECOND AND MORE SUBSTANTIAL WAVE DIGS INTO THE
GREAT LAKES REGION SUNDAY INTO MONDAY.

AT THE SURFACE RIDGING WILL BE IN PLACE FRIDAY NIGHT AND BRING DRY
WEATHER. THE HIGH SLIPS EAST QUICKLY ON SATURDAY WHICH SHOULD ALLOW
CHANCES FOR SHOWERS AND STORMS DURING THE AFTERNOON AHEAD OF THE
UPPER SHORTWAVE. THE CHANCES WILL CONTINUE INTO SATURDAY NIGHT AS A
WAVE OF LOW PRESSURE SLIDES THROUGH THE AREA AT THE SURFACE.

SUNDAY INTO MONDAY CHANCES FOR SHOWERS AND STORMS WILL CONTINUE AS
THE SECOND MORE POTENT UPPER TROUGH DIGS INTO THE GREAT LAKES.
SURFACE FEATURES ARE BIT MORE HARD TO DISCERN IN THIS TIME FRAME AS
THE GFS IS FURTHER NORTH AND DEEPER WITH THE SURFACE WAVE. FOLLOWED
THE GFS CLOSER HERE AS IT MAKES MORE SENSE TO HAVE A DEEPER FARTHER
NORTH WAVE GIVEN THE UPPER PATTERN. WE LOOK TO DRY OUT MONDAY NIGHT
INTO TUESDAY AS HIGH PRESSURE BUILDS IN.

TEMPERATURES THROUGH THE PERIOD SHOULD BE SEASONABLE DESPITE THE
RIDGING DAMPENING OUT. HEIGHTS ARE STILL FAIRLY HIGH AND 850MB TEMPS
ARE FORECAST TO BE IN THE TEENS C. HIGHS SHOULD BE IN THE UPPER 70S
TO AROUND 80 EACH DAY.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z THURSDAY)
ISSUED AT 100 PM EDT WED JUN 12 2013

VFR CONDITIONS SHOULD CONTINUE AT ALL THE TERMINALS THIS AFTERNOON
WITH FAIRLY EXTENSIVE MID CLOUD COVER AND A FEW SHOWERS.

PRIMARY AVIATION CONCERN IS ON SEVERE THUNDERSTORMS THAT WILL LIKELY
IMPACT KAZO... KBTL AND KJXN DURING THE MID TO LATE EVENING HOURS. A
FAST MOVING COMPLEX OF SEVERE STORMS IS LIKELY TO IMPACT THESE
TERMINALS FROM 01Z THROUGH 06Z WITH POTENTIAL FOR VERY SIGNIFICANT
WIND GUSTS IN ADDITION TO FREQUENT LIGHTNING... HEAVY RAIN AND HAIL.

NORTHERLY WINDS WILL DEVELOP TONIGHT IN THE WAKE OF THE STORMS WITH
MVFR CEILINGS AND POSSIBLY VSBY/S (FOG) DEVELOPING.


&&

.MARINE...
ISSUED AT 330 AM EDT WED JUN 12 2013

FAIRLY LIGHT WINDS WILL CONTINUE OVER THE LAKE RESULTING IN LOW WAVE
HEIGHTS. PATCHY DENSE FOG IS POSSIBLE DUE TO HIGH DEWPOINTS OVER THE
COLDER WATER SFC. NORTH WINDS WILL DEVELOP THURSDAY AND A SMALL
CRAFT ADVISORY MAY BE NEEDED.


&&

.HYDROLOGY...
ISSUED AT 330 AM EDT WED JUN 12 2013

THE MAIN PERIOD OF CONCERN IS THIS AFTERNOON AND EVENING. HEAVY
RAINFALL WILL BE POSSIBLE ACROSS THE SRN HALF OF THE CWA DURING THIS
TIME. AN INCH TO TWO INCHES SEEMS PLAUSIBLE ESPECIALLY SOUTH OF
I-94. THIS MAY LEAD TO LOCALIZED FLOODING.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...FLASH FLOOD WATCH FROM 8 PM EDT THIS EVENING THROUGH THURSDAY
     MORNING FOR MIZ064>067-071>074.

LM...NONE.
&&

$$

UPDATE...WDM
SYNOPSIS...93
SHORT TERM...93
LONG TERM...DUKE
AVIATION...LAURENS
HYDROLOGY...93
MARINE...93