Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 101735
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
135 PM EDT THU APR 10 2014

LATEST UPDATE...
AVIATION

.SYNOPSIS...
ISSUED AT 329 AM EDT THU APR 10 2014

A QUICK MOVING FRONT WILL MOVE THROUGH THE AREA TODAY. THIS FRONT
WILL BRING A BRIEF PERIOD OF LIGHT RAINFALL TO MOST AREAS. SKIES
WILL CLEAR OUT LATER TODAY AND REMAIN SO THROUGH FRIDAY AND INTO
EARLY SATURDAY. TEMPERATURES WILL WARM WELL INTO THE 60S ON
FRIDAY...AND COULD APPROACH 70 AT SOME LOCATIONS ON SATURDAY. RAIN
CHANCES WILL INCREASE LATE ON SATURDAY. SIGNIFICANT AMOUNTS OF RAIN
WILL THEN BECOME POSSIBLE ON SUNDAY AND LAST INTO MONDAY ACROSS THE
AREA AS A FRONTAL SYSTEM STALLS OUT NEARBY. MUCH COOLER AIR AND A
THREAT OF SOME SNOW WILL BECOME POSSIBLE BY TUESDAY AS THE FRONT
MOVES AWAY FROM THE AREA.

&&

.UPDATE...
ISSUED AT 1036 AM EDT THU APR 10 2014

THE STRONGER SUNSHINE THIS MORNING WILL ALLOW FOR HIGHER
TEMPERATURES. VALUES WERE BUMPED UP SEVERAL DEGREES.
AS THE FRONT MOVES IN THE THOUGHT IS THAT SHOWERS WILL INCREASE
ALONG IT AS LIFT STRENGTHENS. NOT CERTAIN TO HAPPEN GIVEN THE WEAK
APPEARANCE TO THE UPSTREAM SHOWERS. WILL MAINTAIN THE RELATIVELY
HIGH POPS FOR NOW.

&&

.SHORT TERM...(TODAY THROUGH SATURDAY)
ISSUED AT 329 AM EDT THU APR 10 2014

THE TWO MAIN ITEMS OF INTEREST IN THE SHORT TERM ARE THE RAINFALL
EVENT TODAY...AND THEN THE INCREASING THREAT OF RAINFALL ON SAT
AFTER WHAT LOOKS TO BE A WARM DAY. THE FCST REMAINS MAINLY UNCHANGED
WITH NO MAJOR ADJUSTMENTS NEEDED.

WE CONTINUE TO EXPECT THAT MANY AREAS WILL SEE LIGHT AMOUNTS OF RAIN
TODAY AS THE FRONTAL SYSTEM MOVES THROUGH THE AREA RATHER QUICKLY.
THE FRONT CURRENTLY EXTENDS FROM WRN LAKE SUPERIOR THROUGH NW WI AS
OF 07Z. A FAIRLY DECENT UPPER WAVE HEADING TOWARD JAMES BAY IS
HELPING TO PUSH THIS FRONT THROUGH THE REGION. THERE IS NOT A LOT OF
RAIN CURRENTLY WITH THE FRONT.

WE DO EXPECT THE RAIN TO EXPAND A BIT AS THE FRONT MOVES THROUGH THE
CWFA. THIS OCCURS AS A SHORT WAVE COMING IN ON THE BACKSIDE OF THE
UPPER LOW ACROSS ONTARIO WILL INTERACT WITH THE FRONT. PCPN AMOUNTS
WILL GENERALLY REMAIN BELOW A QUARTER OF AN INCH. NOT MUCH HAS
CHANGED WITH THE THUNDER THREAT. THERE REMAINS A VERY LOW CHC OF
SOME THUNDER AS ELEVATED LI/S APPROACH ZERO. ONCE AGAIN...WE BELIEVE
THERE IS NOT ENOUGH INSTABILITY AT THIS TIME TO ADD THUNDER IN AS
NOTHING HAS REALLY CHANGED.

WE WILL SEE THE CLOUDS CLEAR OUT RATHER QUICKLY BEHIND THE FRONT
LATE THIS AFTERNOON AND THIS EVENING BEHIND THE FRONT. THERE IS NOT
A LOT OF UPPER RIDGING EXPECTED TO BUILD IN THE BEHIND THIS WAVE. WE
WILL SEE A WEAK AREA OF HIGH PRESSURE AT THE SFC SCOOT BY TO OUR
SOUTH WITH SOMEWHAT CONFLUENT FLOW ALOFT TAKING SHAPE. CONDITIONS
SHOULD REMAIN MAINLY DRY THROUGH EARLY SAT. THE EXCEPTION TO THIS IS
A SHORT WAVE THAT WILL BE RIDING TO THE EAST JUST SOUTH OF THE
U.S./CANADIAN BORDER. THE WAVE WILL REMAIN NORTH OF THE AREA...AND
THE ASSOCIATED SFC FRONT WILL WEAKEN AS IT TRIES TO MOVE INTO THE
AREA. THIS WILL PRODUCE A LOW CHANCE OF A SHOWER FRI EVENING ALONG
AND NORTH OF THE M-20 CORRIDOR.

WE ARE EXPECTING ONE OF THE WARMEST DAYS FOR LOWER MI DURING THE DAY
ON SAT BEFORE THE CHANCE FOR RAIN INCREASES SAT AFTERNOON. A STRONG
SRLY LOW LEVEL FLOW WILL DEVELOP ON SAT AS A STRONGER UPPER WAVE AND
ASSOCIATED INVERTED SFC LOW MOVES INTO THE UPPER PLAINS EARLY SAT.
THESE STRONG SRLY WINDS WILL ADVECT +8C OR SO AT H850 UP INTO THE
AREA. WITH SOME SUNSHINE DURING THE FIRST HALF OF THE DAY...WE WILL
SEE TEMPS APPROACH 70 BY MID AFTERNOON. THE MOISTURE TRANSPORT WILL
REALLY RAMP UP AFTER 18Z SAT...HELPING TO INCREASE THE CHCS OF RAIN
FROM NW TO SE. THE BETTER PCPN WILL HOLD OFF UNTIL AFTER SAT AS WILL
INSTABILITY FOR ANY THUNDER.

.LONG TERM...(SATURDAY NIGHT THROUGH WEDNESDAY)
ISSUED AT 329 AM EDT THU APR 10 2014

THE PRIMARY FOCUS IN THE LONG TERM IS THE POTENTIAL FOR HEAVY RAIN
AND FLOODING AS AN ACTIVE FRONTAL BOUNDARY IMPACTS THE AREA. AS MUCH
AS 3 INCHES OF RAIN COULD FALL FROM SATURDAY NIGHT THROUGH MONDAY.
THE AXIS OF HEAVIEST RAIN AT THIS TIME IS PROGGED TO BE ACROSS THE
MUSKEGON RIVER BASIN.

IN ADDITION TO THE SFC BOUNDARY WHICH BECOMES NEARLY STATIONARY OVER
SRN LWR MI... PERSISTENT RIGHT ENTRANCE JET DYNAMICS ARE PROGGED TO
BE PRESENT AS 150 KT UPPER LEVEL JET BECOMES PARKED FROM THE
ARROWHEAD OF MN TO JAMES BAY.

GUIDANCE DEPICTS A VERY SHARP GRADIENT OF RAINFALL... WITH MOST OF
THE HEAVY RAIN FALLING ALONG AND NORTH OF THE BOUNDARY AND MUCH LESS
SOUTH OF THE FRONT. THIS MAKES THINGS TRICKY SINCE THE EXACT FRONTAL
POSITION/TIMING IS STILL SOMEWHAT UNCLEAR. THERE WILL ALSO BE SHARP
TEMPERATURE GRADIENT... WITH MILD READINGS NEAR 70 SOUTH OF THE
BOUNDARY AND READINGS PROBABLY IN THE 40S OR COLDER TO THE NORTH.

THE OTHER FCST CHALLENGE IS TIMING OF WAVES ALONG THE FRONT AND
TIMING THE INTRUSION OF THE COLD DRY AIR BEHIND THE FRONT. THIS IS
CRITICAL BECAUSE A CHANGEOVER TO SNOW OR A MIX OF RAIN AND SNOW IS
LIKELY IF THE COLD AIR ARRIVES BEFORE THE PRECIP DEPARTS. LATE
SUNDAY NIGHT AND MONDAY IS THE TIME FRAME OF CONCERN FOR WINTRY
PRECIP DEVELOPING... ESPECIALLY OVER THE NW CWFA.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z FRIDAY AFTERNOON)
ISSUED AT 135 PM EDT THU APR 10 2014

MAIN AVIATION CONCERN REMAINS THE STRONG WSW WINDS.  THEY WILL
CONTINUE TO GUST AS HIGH AS 35 KNOTS FOR A FEW HOURS PAST 18Z THU.
HOWEVER MIXING WILL BE REDUCED LATER THIS AFTERNOON AS COLD FRONT
MOVES INTO THE REGION. THE GUSTINESS IS EXPECTED TO DIMINISH MID
AFTERNOON. WITH ONLY LIGHT WINDS EXPECTED AFTER NIGHTFALL.

THE FRONT WILL BATTLE DRY LOW LEVELS AND WILL THEREFORE PRODUCE
VERY LITTLE RAIN AND CEILINGS AND VSBYS ARE EXPECTED TO REMAIN VFR.

&&

.HYDROLOGY...
ISSUED AT 1036 AM EDT THU APR 10 2014

CONFIDENCE IS INCREASING WITH REGARDS TO THE HEAVY RAINFALL
POTENTIAL SAT NIGHT INTO MON. INCREASED RISK FOR GREATER THAN 2
INCHES. SEVERAL ROUNDS OF RAIN ARE EXPECTED. THIS SYSTEM HAS A
COUPLE OF INGREDIENTS THAT COULD LEAD TO HEAVY RAIN WHICH COULD
CAUSE HYDRO IMPACTS. THEY INCLUDE A SLOW MOVING FRONT...IT WILL
CONTAIN ABUNDANT GULF MOISTURE ALONG WITH INSTABILITY. THIS OPENS
UP THE POSSIBILITY OF HEAVY RAIN SHOWERS REPEATING OVER THE SAME
AREA. IN ADDITION THE RIVER LEVELS ARE ELEVATED AND THE GROUND IS
MOIST. OVERALL FLOOD IMPACTS WILL BE DETERMINED WHETHER THESE
ROUNDS OF RAIN OCCUR OVER THE SAME AREA.

SMALL STREAMS WOULD BE IMPACTED FIRST...POSSIBLY SUNDAY...FOLLOWED
BY THE LARGER RIVERS FOR THE REMAINDER OF NEXT WEEK.

WHILE NOT CERTAIN TO HAPPEN...THIS WILL BE SOMETHING
THAT WE WILL NEED TO CLOSELY MONITOR IN THE COMING DAYS.

AS FOR TODAY...RIVERS GENERALLY TRENDING DOWNWARD. THE RAINFALL FOR TODAY
IS NOT EXPECTED TO PRODUCE ENOUGH RUNOFF TO RAISE RIVER LEVELS UP
SIGNIFICANTLY THROUGH SATURDAY.

&&

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

$$

UPDATE...MJS
SYNOPSIS...NJJ
SHORT TERM...NJJ
LONG TERM...MEADE
AVIATION...JK
HYDROLOGY...MJS






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