Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 211640
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
1240 PM EDT THU MAY 21 2015

LATEST UPDATE...
HYDRO

.SYNOPSIS...
ISSUED AT 259 AM EDT THU MAY 21 2015

SCATTERED SHOWERS MAY DRIFT FROM NORTH TO SOUTH LATE THIS
AFTERNOON INTO TONIGHT AS A COLD FRONT APPROACHES. AFTER A MILD
DAY WITH HIGHS IN THE 60S...TEMPS WILL BE SEVERAL DEGREES COOLER
ON FRIDAY. AREAS OF FROST ARE ONCE AGAIN POSSIBLE FRIDAY MORNING
AND SATURDAY MORNING...ESPECIALLY FOR CENTRAL LOWER MICHIGAN. A
WARMER AND MORE HUMID PATTERN LOOKS TO TAKE SHAPE FOR EARLY NEXT
WEEK WITH RAIN CHANCES RETURNING.

&&

.SHORT TERM...(TODAY THROUGH SATURDAY)
ISSUED AT 259 AM EDT THU MAY 21 2015

PRIMARY FOCUS IS ON SHOWER POTENTIAL LATER TODAY ALONG WITH FROST
POTENTIAL FRIDAY AND SATURDAY MORNINGS. SFC COLD FRONT IS FORECAST
TO REACH NORTHERN WISCONSIN AND INTO THE STRAITS AREA BY 18Z
TODAY. THE ONLY MOISTURE AVAILABLE IS IN THE MID LEVELS...H500 TO
H800...WITH BUFKIT SOUNDINGS INDICATING AN INVERTED V SHAPE.

WHILE ANY SFC BASED INSTABILITY WILL BE CONFINED TO WISCONSIN...SOME
OF THESE DIURNALLY DRIVEN SHOWERS MAY SURVIVE THE NIGHTTIME HOURS
AS THEY PROGRESS ALONG THE FRONT...REACHING LDM BETWEEN 21Z-00Z
AND GRR BY 03Z OR SO. GIVEN THE NEARLY DRY ADIABATIC LAPSE RATES
DOWN LOW...SOME GUSTY WINDS OF 30 TO 40 MPH ARE POSSIBLE WITH THE
SHOWERS...ALTHOUGH COVERAGE WILL BE SCATTERED IT APPEARS. THE HI
RES CAMS SUGGEST THE ACTIVITY FIZZLES AFTER 06Z FRIDAY.

FRIDAY MORNING FROST POTENTIAL LOOKS BETTER THAN THIS MORNING FOR
CENTRAL LOWER. CLOUD COVER SHOULD BE LESS OF AN ISSUE AND WITH CAA
UNDERWAY THERE COULD CERTAINLY BE AREAS OF FROST MAINLY FOR THE
ROUTE 10 CORRIDOR. SATURDAY MORNING MAY FEATURE A MORE SIGNIFICANT
FROST UNFORTUNATELY FOR AREAS NEAR/NORTH OF A BIG RAPIDS TO MOUNT
PLEASANT LINE.

.LONG TERM...(SATURDAY NIGHT THROUGH WEDNESDAY)
ISSUED AT 259 AM EDT THU MAY 21 2015

RETURN FLOW SETS UP SATURDAY NIGHT BUT PRECIP SHOULD HOLD OFF UNTIL
SUNDAY WHEN AN AREA OF ISENTROPIC ASCENT NORTH OF THE SFC WARM FRONT
BRINGS SHOWERS AND A POSSIBLY A RUMBLE OF THUNDER. THE WARM FRONT
MOVES NORTH SUNDAY NIGHT WITH THE HEAVIER SHOWERS LIFTING NORTH WITH
IT...BUT A DEEP SOUTHERLY FLOW OF GULF MOISTURE CONTINUES THROUGH
MONDAY. INSTABILITY IS FAIRLY WEAK SO THUNDER THREAT IS LIMITED.

COVERAGE OF SHOWERS SHOULD DECREASE TUESDAY AND WEDNESDAY AS THE
STRONGER MOISTURE TRANSPORT MOVES EAST. GIVEN THERMAL PROFILES THE
MAX TEMPS IN THE 70S FOR TUESDAY AND WEDNESDAY MAY BE UNDERDONE BUT
WERE LEFT ALONE FOR NOW WITH THE POSSIBILITY THAT CLOUDS AND SHOWERS
THOSE DAYS COULD BE WIDESPREAD.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z FRIDAY MORNING)
ISSUED AT 711 AM EDT THU MAY 21 2015

VFR CONDITIONS THROUGH TONIGHT...WITH SOME SCATTERED SHOWERS
POSSIBLE THIS EVENING. WINDS WILL BE WEST AROUND 10 KNOTS TODAY
WITH SOME GUSTS TO 20 KNOTS THIS AFTERNOON.


&&

.MARINE...
ISSUED AT 259 AM EDT THU MAY 21 2015

NO SIGNIFICANT WAVE ACTION NOR FOG IS ON THE HORIZON FOR THE
NEARSHORE WATERS. SOME WAVES COULD APPROACH 2 TO 3 FEET AT TIMES
TODAY BUT REMAIN BELOW SMALL CRAFT ADVISORY CRITERIA.

&&

.HYDROLOGY...
ISSUED AT 1240 PM EDT THU MAY 21 2015

NO CONCERNS THROUGH THE WEEKEND. PRECIPITATION THAT COULD AFFECT
MAINSTEM RIVERS IS NOT EXPECTED UNTIL LATE SUNDAY...WHICH MARKS THE
START OF A WETTER PATTERN LASTING WELL INTO THE COMING WORK WEEK.
NATIONAL GUIDANCE ADVERTISES UNIFORM RAINFALL TOTALS OF 1-1.5
INCHES ACROSS THE AREA THROUGH THURSDAY MORNING. GIVEN THAT BASE
FLOWS ARE NEAR OR BELOW NORMAL AND THAT RAIN SHOULD BE SPREAD OUT
OVER TIME...WE EXPECT FAIRLY GENTLE RISES WILL BE UNDERWAY BY THE
MIDDLE OF NEXT WEEK.

THAT SAID...FORECASTING CONVECTIVE RAINFALL THIS FAR OUT IS
HIGHLY UNCERTAIN SO THERE STILL REMAINS A FAIRLY WIDE RANGE OF
POSSIBILITIES FOR RAINFALL AND RIVER RESPONSES AT THIS POINT.

&&

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

$$

SYNOPSIS...HOVING
SHORT TERM...HOVING
LONG TERM...OSTUNO
AVIATION...OSTUNO
HYDROLOGY...TJT
MARINE...HOVING


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