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000
FXUS63 KGRR 130609
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
209 AM EDT SUN JUL 13 2014

LATEST UPDATE...
MESOSCALE DISCUSSION

.MESOSCALE DISCUSSION...
ISSUED AT 209 AM EDT SUN JUL 13 2014

THE THREAT FOR SEVERE WEATHER IS DIMINISHING STEADILY AS OF 06Z
THIS MORNING. RADAR SIGNATURES ARE BECOMING LESS ORGANIZED WITH AN
ALMOST STRATIFORM RAIN NOW WITH EMBEDDED THUNDER. CLOUD TOPS ON IR
IMAGERY ARE WARMING ALSO...INDICATIVE OF THE STORMS WEAKENING. LLJ
IS STILL ONGOING BUT WILL NOW SHIFT TO THE EAST. INSTABILITY
UPSTREAM AVAILABLE TO ADVECT IN IS DIMINISHING WITH ABOUT 2000
J/KG OF CAPE NOW TO OUR S...AND 1000 J/KG OF CAPE ACROSS OUR SRN
COUNTIES. THIS WILL ONLY CONTINUE TO DIMINISH THROUGH THE
REMAINDER OF THE NIGHT AS ANY HEATING LEFT OVER FROM THE DAY IS
GONE.

&&

.SYNOPSIS...
ISSUED AT 231 PM EDT SAT JUL 12 2014

A COLD FRONT WILL PUSH THROUGH THE REGION LATE TONIGHT INTO SUNDAY
MORNING. THIS SYSTEM WILL TRIGGER THUNDERSTORMS. SOME OF THE
STORMS WILL CONTAIN HEAVY RAIN AND A FEW COULD TURN SEVERE. A
DRIER AIRMASS WILL FILTER IN FROM THE NORTHWEST ON SUNDAY. A COOL
CANADIAN AIRMASS ARRIVES FOR EARLY NEXT WEEK.

&&

.SHORT TERM...(THIS EVENING THROUGH MONDAY NIGHT)
ISSUED AT 231 PM EDT SAT JUL 12 2014

CHALLENGE IN THE SHORT TERM DEALS WITH THE SEVERE POTENTIAL
TONIGHT. LOOKS LIKE AN INCREASED POTENTIAL FOR SEVERE WEATHER WILL
EXIST.

THE FORCING FROM AN APPROACHING MID LEVEL WAVE COMBINES WITH THE
INSTABILITY AND A LOW LEVEL JET TO TRIGGER THUNDERSTORMS TONIGHT.
GOOD DIFFLUENCE WAS NOTED AT THE TROP.  THE MAIN TIMEFRAME LOOKS
TO BE 03Z TO 08Z. DAMAGING WINDS SEEMS LIKE THE MAIN THREAT WITH A
50 KNOT LOW LEVEL JET. GIVEN THE HIGH 0 TO 1 KM SHEAR...LOW LCL
AND LOW LEVEL CAPE...WOULD NOT RULE OUT A TORNADO AS WELL. THIS
RISK SEEMS HIGHEST AROUND INTERSTATE 94 GIVEN THE FORECASTED LOW
LEVEL JET LOCATION. HAZARDS WERE UPDATED IN THE HWO AND SOCIAL
MEDIA POSTS. HIGH POPS ALL ZONES. BY 09Z NORTHWEST COUNTIES SHOULD
SEE A DIMINISHING TREND TO THE PRECIPITATION.

FORECAST SOUNDINGS FOR SUNDAY AFTERNOON INTO SUNDAY NIGHT SHOULD A
LIMITED RISK FOR PRECIPITATION. WITH MOST LOCATIONS TO REMAIN
DRY...I LOWERED POPS.

THE UPPER LOW PIVOTS THROUGH THE REGION ON MONDAY. THIS WILL ACT
TO KEEP IT COOL WITH A RISK FOR A THUNDERSTORM...ESPECIALLY IN THE
AFTERNOON.

.LONG TERM...(TUESDAY THROUGH SATURDAY)
ISSUED AT 231 PM EDT SAT JUL 12 2014

THE LONG TERM PERIOD WILL SEE A STEADY MODERATING TREND AS THE DEEP
UPPER TROUGH MOVES SLOWLY EASTWARD. VERY COLD H5 TEMPS NEAR -19C
WILL RESULT IN UNSTABLE CONDITIONS. THIS TIME OF YEAR THAT USUALLY
MEANS PM STORMS WITH SMALL HAIL. TRENDED CLOUD COVER UPWARD DURING
THE AFTERNOON TUESDAY OVER INLAND AREAS. INCLUDED A THUNDER MENTION
TUESDAY AFTERNOON AND WEDNESDAY AFTERNOON. BY THURSDAY THE UPPER LOW
WILL BE EAST OF THE CWA AND THE PCPN THREAT WILL BE GREATLY
DIMINISHED. A VERY CHILLY DAY IS EXPECTED TUESDAY WITH HIGHS IN THE
MID 60S. HOWEVER...BY THE WEEKEND TEMPS WILL BE BACK TO AROUND 80.
THE LAST HALF OF THE PERIOD LOOKS DRY AS SFC HIGH PRESSURE WILL
DEVELOP OVER LOWER MICHIGAN.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SUNDAY NIGHT)
ISSUED AT 1237 AM EDT SUN JUL 13 2014

MAIN ISSUE FOR AVIATION INTERESTS WITH THE 06Z FCSTS WILL BE
ONGOING CONVECTION AND RESIDUAL FOG/STRATUS THROUGH SUN MORNING.
THE MAIN AREA OF CONVECTION WILL MOVE INTO ALL OF THE TERMINALS BY
06Z. HEAVY RAIN AND A MOIST ATMOSPHERE ARE ALMOST SURE TO PRODUCE
IFR CONDITIONS OR WORSE. WE EXPECT THAT SHOWERS AND STORMS WILL
START COMING TO AN END AROUND 08Z AT KMKG AND THEN BY 11-12Z AT
KJXN. WE DO EXPECT FOG/STRATUS TO HANG AROUND AFTER THE END OF THE RAIN.

CONDITIONS WILL THEN GRADUALLY IMPROVE SUN MORNING AS CIGS LIFT
AND ANY FOG DISSIPATES. WE EXPECT THAT MOST SITES SHOULD BECOME
VFR TOWARD 16Z OR SO WITH SOME SCT CUMULUS/STRATOCUMULUS HANGING
AROUND. GUSTY WINDS TO AROUND 20-25 KNOTS WILL DEVELOP IN THE
AFTERNOON...AND THEN END AROUND 00-01Z.


&&

.MARINE...
ISSUED AT 231 PM EDT SAT JUL 12 2014

OVERALL CONDITIONS ARE EXPECTED TO REMAIN BELOW CRITERIA FOR
HEADLINES. CONVECTION COULD LEAD TO BRIEF PERIOD OF STRONGER WINDS
AND HIGHER WAVES.


&&

.HYDROLOGY...
ISSUED AT 231 PM EDT SAT JUL 12 2014

AT THIS TIME NO WATCH FOR FLOODING. THE THOUGHT IS THAT THE STORMS
WILL TRACK STEADILY EAST...ROUGHLY 03Z TO 08Z. MOST LOCATIONS WILL
SEE A STORM THAT LASTS FOR AN HOUR OR PERHAPS TWO. GENERALLY AN
INCH OF RAIN WILL ACCOMPANY THE STORMS...BUT LOCAL AMOUNTS COULD
TOP 2 INCHES. URBAN AND POOR DRAINAGE FLOODING APPEARS TO BE THE
MAIN RISK FROM THESE STORMS. PWAT VALUES OVER 2 INCHES AND GOOD
FORCING SUPPORT MOST LOCATIONS SEEING THESE HEAVY DOWNPOURS.

&&

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

$$

MESOSCALE...NJJ
SYNOPSIS...MJS
SHORT TERM...MJS
LONG TERM...93
AVIATION...NJJ
HYDROLOGY...MJS
MARINE...MJS