Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 061506
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
1106 AM EDT SUN JUL 6 2014

LATEST UPDATE...
UPDATE/MARINE

.SYNOPSIS...
ISSUED AT 325 AM EDT SUN JUL 6 2014

SHOWERS AND THUNDERSTORMS WILL BECOME LIKELY THIS EVENING ACROSS THE
ENTIRE AREA AFTER A RELATIVELY QUIET AND MAINLY DRY DAY TODAY. THE
SHOWERS AND STORMS COULD BECOME LOCALLY STRONG TO SEVERE TONIGHT
WITH HAIL THE MAIN THREAT AND DAMAGING WINDS POSSIBLE. RAIN WILL
DIMINISH ON MONDAY MORNING WITH SOME SUN AND SEASONABLE TEMPERATURES
MONDAY AFTERNOON. ANOTHER SYSTEM WILL MOVE THROUGH LATER MONDAY
NIGHT AND AT LEAST THE FIRST PORTION OF TUESDAY. SOME STRONGER
STORMS WILL BE POSSIBLE ONCE AGAIN.

&&

.UPDATE...
ISSUED AT 1106 AM EDT SUN JUL 6 2014

THINKING HAS NOT CHANGED MUCH FROM THE OVERNIGHT SHIFT. UPSTREAM
COLD FRONT IS LOCATED WELL WEST OF THE AREA ACROSS MINNESOTA AT
THIS TIME. WIDESPREAD LOWER CLOUD IS IN PLACE AHEAD OF THE FRONT
ACROSS IA/MN/WI. THIS WILL LIKELY ACT TO DELAY THUNDERSTORM
DEVELOPMENT AND PUSH THE TIMING FOR UPSTREAM INITIATION INTO THE
LATE AFTERNOON OR EARLY EVENING. THESE STORMS WOULD THEN PUSH INTO
SOUTHWEST LOWER MICHIGAN AFTER 8PM. FEEL THE BEST CHANCES WILL
OCCUR IN THE WINDOW FROM ABOUT 8PM THROUGH 5AM. PROBABILITIES
BEGIN TO INCREASE THOUGH AFTER 5PM THIS EVENING AS THE LLJ RAMPS UP.

A TREND IN MODEL GUIDANCE...VIA THE NEW NAM AND THE LATEST RUC
DATA IS FOR THE CORE OF THE 850MB LLJ AND HENCE THE STRONG
MOISTURE TRANSPORT TO BE SHIFTED SOUTH ACROSS THE FORECAST AREA
JUST A BIT. IT SEEMS TO BE FOCUSED MORE INTO THE SOUTHERN HALF OF
THE AREA NOW VERSUS EARLIER RUNS THAT HAD THE CORE RIGHT IN THE
HEART OF THE AREA.

FEEL DYNAMICS ASSOCIATED WITH THE UPPER WAVE SEEN DROPPING
SOUTHEAST ACROSS NORTHERN MINNESOTA AT THIS TIME THOUGH WILL BRING
STORMS TO ALL AREAS. THE DELAY IN UPSTREAM TIMING VIA THE LOW
CLOUDS MAY BRING INITIATION CLOSER TO OUR AREA OVER EASTERN
WISCONSIN OR EVEN LAKE MICHIGAN WHICH IS WHAT THE LATEST (12Z) HRRR
SIMULATED REFLECTIVITY GUIDANCE IS SHOWING. THIS MAY ALLOW FOR
MORE CELLULAR/DISCRETE STORMS INITIALLY MOVING INTO SOUTHWEST
LOWER BEFORE BECOMING LINEAR. STILL THINKING THE MAIN THREATS
WILL BE HAIL/WIND. DEGREE OF INSTABILITY WILL DICTATE WHETHER OR
NOT WE SEE SEVERE STORMS. AT THIS POINT IT APPEARS THE BEST
MOISTURE RETURN AND STRONGEST INSTABILITY WILL BE LOCATED WEST AND
SOUTHWEST OF LAKE MICHIGAN THIS AFTERNOON AND EVENING. STRONG
STORMS APPEAR LIKELY...WITH THE SEVERE THREAT BEING A TOUGHER
CALL. CANNOT RULE OUT A FEW SEVERE STORMS HOWEVER GIVEN THE
STRENGTH OF THE LLJ AND THE MID LEVEL SHORTWAVE.

&&

.SHORT TERM...(TODAY THROUGH TUESDAY)
ISSUED AT 325 AM EDT SUN JUL 6 2014

THE MAIN FOCUS OF THE SHORT TERM IS ON THE SEVERE POTENTIAL FOR
TONIGHT AND AGAIN LATE MON NIGHT AND ON TUE. WE DO EXPECT STRONGER
STORMS TONIGHT WITH SOME LOCALLY SEVERE STORMS POSSIBLE ACROSS THE
AREA ALONG WITH LOCALLY HEAVY RAIN POTENTIAL. THE SEVERE THREAT ON
TUE IS NOT CERTAIN RIGHT NOW...BUT IT WILL BE POSSIBLE.

TODAY IS EXPECTED TO START OUT QUIET. THERE ARE A COUPLE OF SHORT
WAVES/REMNANT MCV/S FLOATING THROUGH THE REGION THIS MORNING. ONE IS
JUST MOVING OVERHEAD RIGHT NOW FROM THE WEST AND IS NOT DOING
ANYTHING. ANOTHER IS SOUTH OF THE AREA AND SHOULD NOT BOTHER THE
AREA. WE WILL SEE SHORT WAVE RIDGING BUILD IN FOR THE FIRST HALF OF
THE DAY. A RESULT OF THIS WILL BE SOME CAPPING EXPECTED TO TAKE
PLACE PER FCST SOUNDINGS. WE CAN NOT RULE OUT A SHOWER/STORM POPPING
ALONG THE LAKE SHADOW THROUGH MID AFTERNOON WHERE SOME LOCALIZED
CONVERGENCE INLAND WILL TAKE SHAPE.

THE CHANCES OF CONVECTION WILL INCREASE GREATLY STARTING AROUND 00Z
AND PEAKING BY 06Z OR SO. WE WILL SEE A SHORT WAVE IN THE UPPER FLOW
APPROACH THE AREA AT THAT TIME. OUT AHEAD OF IT...A 40+ KNOT LLJ
WILL RAMP UP AND BRING A GREAT DEAL OF MOISTURE TRANSPORT INTO THE
AREA. MODELS SEEM TO BE FOCUSING A GOOD DEAL OF DEVELOPMENT OVER THE
WEST...POSSIBLY WHERE SOME SEMBLANCE OF THE SFC CONVERGENCE MAY BE
LEFT AND CO-LOCATED WITH THE BETTER MOISTURE TRANSPORT ABOVE THE
SFC. INSTABILITY PEAKS AROUND 1000-1500 J/KG AROUND 00Z ACROSS THE
SW BEFORE WANING SOME AS WE LOSE THE DIURNAL COMPONENT. THE CAP
ALOFT WILL BE ERASED BY THIS TIME. SEVERE WX IS POSSIBLE WITH THE
STRONG LLJ THAT WILL BE OVERHEAD...AND WITH DECENT CAPE ALOFT IN THE
HAIL GENERATION LAYER. HAIL LOOKS TO BE THE BIGGEST THREAT AS THERE
IS A DECENT INVERSION THAT DEVELOPS IN THE LOWEST 2K FT THAT COULD
PREVENT WINDS FROM BEING A WIDESPREAD THREAT. HEAVY RAIN WILL ALSO
BE POSSIBLE WITH PWATS JUST UNDER 2 INCHES.

WE EXPECT TO SEE CONVECTION THEN GRADUALLY MOVE OUT AFTER 06Z...AND
IT SHOULD LIKELY EXIT THE ENTIRE AREA JUST AFTER 12Z MON. SHORT WAVE
RIDGING IS EXPECTED TO BUILD IN THEN FOR THE REST OF THE DAY ON
MON...BRINGING SUNSHINE BACK AND ALLOWING TEMPS TO WARM INTO THE
LOWER 80S.

WE EXPECT ANOTHER ROUND OF CONVECTION SOMETIME VERY LATE MON NIGHT
INTO EARLY TUE AFTERNOON. ANOTHER SHORT WAVE WILL BE DROPPING SE
AROUND THE LONG WAVE TROUGH EXTENDING FROM HUDSON BAY DOWN THROUGH
THE GREAT LAKES...AND ALMOST TO THE MASON-DIXON LINE. THE TRACK OF
THE SFC LOW IS A BIT UNCERTAIN AT THIS TIME...WITH SOLUTIONS RANGING
FROM IT REMAINING SOUTH OF THE AREA...TO NORTH OF THE AREA. THIS HAS
BIG IMPLICATIONS WITH REGARD TO POTENTIAL INSTABILITY. IF IT DOES GO
MORE NORTHERLY LIKE THE EURO AND WE ARE ABLE TO GENERATE SOME
DIURNAL INSTABILITY...WE COULD BE LOOKING AT DECENT SEVERE WX
POTENTIAL ON TUE AS DEEP LAYER SHEAR IS HEALTHY AT 40+ KNOTS. THE
FURTHER EAST YOU GO LOOKS LIKE A BETTER POTENTIAL DUE TO THE EARLY
AFTERNOON TIMING OF THE COLD FRONT/UPPER WAVE THROUGH THE AREA.

.LONG TERM...(TUESDAY NIGHT THROUGH SATURDAY)
ISSUED AT 325 AM EDT SUN JUL 6 2014

FORECAST CHALLENGES DEAL WITH THE TIMING AND STRENGTH OF THE
THUNDERSTORMS.  OVERALL LOOKS LIKE CHANCES ARE LOW FOR THUNDERSTORMS
TO START THE PERIOD...BUT A POTENTIALLY ACTIVE PERIOD EXISTS FOR
NEXT WEEKEND.

THE UPPER TROUGH PASSES THROUGH LOWER MI WED SUPPORTING A POSSIBLE
THUNDERSTORM OR TWO ESPECIALLY DURING PEAK HEATING.  FOR THIS
REASON...WILL KEEP A LOW RISK GOING FOR THUNDERSTORMS THROUGH WED.
HIGH PRESSURE MOVES IN AND MID LEVEL HEIGHTS WARM THU AND FRI...SO
IT LOOKS DRY THEN.

FOR NEXT SAT MODELS ARE NOT IN GOOD AGREEMENT SO CONFIDENCE IS LOWER
THAN NORMAL.  GFS TRACKS A WEAKENING MID LEVEL WAVE EASTWARD THROUGH
ONTARIO FRI NIGHT THROUGH SAT.  HIGH RES EURO DEEPENS THIS FEATURE
AND ENDS UP AS A CLOSED UPPER LOW JUST NORTH OF LAKE SUPERIOR
SUNDAY.  THE MUCH STRONGER HIGH RES EURO SCENARIO ALLOWS FOR MORE
WIDESPREAD CONVECTION AND A SMALL RISK FOR SEVERE STORMS.  I WILL
FAVOR THE HIGH RES EURO AS THIS HAS BEEN THE PATTERN WE HAVE BEEN IN
LATELY.  WILL KEEP THE HIGHER THAN NORMAL POPS GOING FOR NEXT SAT.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z MONDAY MORNING)
ISSUED AT 619 AM EDT SUN JUL 6 2014

LOOKS LIKE VFR WEATHER TO PREVAIL INTO THE AFTERNOON...WHEN A FEW
THUNDERSTORMS COULD START TO DEVELOP. ANTICIPATED COVERAGE OF THE
STORMS IS TOO LOW TO INCLUDE THEM IN THE FORECAST...HOWEVER THIS
WILL NEED TO BE MONITORED CLOSELY. A HIGHER RISK FOR STORMS AND
IMPACTS IS TONIGHT...WHEN UPSTREAM CONVECTION IN WISCONSIN PUSHES
EAST INTO WRN MI. I DID INCLUDE VCTS FOR THE TAFS...GENERALLY
AFTER 00Z. LOCALIZED IMPACTS WITH THE STORMS INCLUDES IFR AND
LOWER CONDITIONS.  WIND GUSTS THIS AFTERNOON COULD TOP 25 KNOTS.


&&

.MARINE...
ISSUED AT 1106 AM EDT SUN JUL 6 2014

SUFFICE IT TO SAY IT WILL BE A HAZARDOUS DAY FOR SMALLER WATER CRAFT
AND BEACH GOERS. THE BEACH HAZARDS STATEMENT AND SMALL CRAFT
ADVISORY REMAIN IN EFFECT THROUGH TONIGHT.

WINDS AND WAVES CONTINUE TO RAMP UP THIS MORNING AS WE PRESS INTO
THE HEART OF THE BEACH/BOATING DAY. LUDINGTON IS INDICATING 4
FOOT WAVES WITH PORT SHELDON AT 3.3 FEET CURRENTLY. MOST COASTAL
MARINE SHORE OBS HAVE WINDS GUSTING OVER 20 KNOTS...WITH MANISTEE
GUSTING TOWARDS 30 KNOTS. WAVES SHOULD PUSH SOLIDLY INTO THE RANGE
WHERE BEACH HAZARDS BECOME A LARGE CONCERN...3-5 FEET. CANNOT RULE
OUT...AS WAS MENTIONED YESTERDAY SOME 4-7 FOOTERS NORTH OF
HOLLAND. IT WILL BE A ROUGH DAY WITH DANGEROUS SWIMMING
CONDITIONS. STRUCTURAL CURRENTS CAN BE EXPECTED ON THE SOUTH SIDES
OF SOUTH PIERS WITH LONGSHORE CURRENTS SWEEPING UP THE BEACH INTO
THE STRUCTURES.

WINDS AND WAVES WILL DIMINISH/SUBSIDE INTO MONDAY.

&&

.HYDROLOGY...
ISSUED AT 329 PM EDT SAT JUL 5 2014

RIVER LEVELS REMAIN ELEVATED ACROSS THE AREA COMPARED TO NORMAL FOR
THIS TIME OF YEAR. MOST SITES HAVE A COUPLE FEET BEFORE THEY WOULD
REACH BANKFULL/ADVISORY STAGE HOWEVER.

MOST CONCENTRATED PERIOD OF SHOWERS AND STORMS ACROSS THE AREA IN
THE NEXT COUPLE DAYS WILL COME SUNDAY EVENING AND SUNDAY NIGHT. THE
RAIN WILL COME VIA THUNDERSTORMS ALONG AN ADVANCING COLD FRONT. AT
THIS POINT BASIN AVERAGE PRECIPITATION WOULD BE ON THE ORDER OF A
HALF INCH TO AN INCH AT MOST...SO NOT EXPECTING BIG RIVER ISSUES
THROUGH MONDAY. ADDITIONAL RAIN INTO TUESDAY COULD PRODUCE FURTHER
RISES.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...BEACH HAZARDS STATEMENT THROUGH MONDAY MORNING FOR MIZ037-043-
     050-056-064-071.

LM...SMALL CRAFT ADVISORY UNTIL 8 AM EDT MONDAY FOR LMZ844>849.

&&

$$

UPDATE...DUKE
SYNOPSIS...NJJ
SHORT TERM...NJJ
LONG TERM...MJS
AVIATION...MJS
HYDROLOGY...DUKE
MARINE...DUKE






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