Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 250738 CCA
AFDGRR

AREA FORECAST DISCUSSION...COR TYPOS
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
330 AM EDT MON APR 25 2016

LATEST UPDATE...
SYNOPSIS/SHORT TERM/LONG TERM/MARINE

.SYNOPSIS...
ISSUED AT 330 AM EDT MON APR 25 2016

RAIN SHOWERS WILL GRADUALLY INCREASE OVER THE SOUTHWEST MICHIGAN
TODAY...ESPECIALLY ALONG AND NORTH OF I-96.  THEN ALL AREAS WILL SEE
RAIN AND A FEW RUMBLES OF THUNDER THIS EVENING...WITH THE RAIN
LETTING UP LATE TONIGHT.  MOST LOCATIONS SHOULD SEE BETWEEN A HALF
AND THREE QUARTERS OF AN INCH OF RAIN BY EARLY TUESDAY. AFTER A MILD
DAY TODAY IT WILL BE COOLER TUESDAY AND WEDNESDAY...BUT DRY WEATHER
IS EXPECTED.

ANOTHER SYSTEM SHOULD BRING RAIN WEDNESDAY NIGHT INTO THURSDAY...BUT
THEN MUCH OF THE LATTER PORTION OF THE WEEK SHOULD BE DRY.  AFTER
ANOTHER CHILLY DAY ON THURSDAY...WE SHOULD RETURN TO NEAR NORMAL
TEMPERATURES FOR FRIDAY AND THE WEEKEND.

&&

.SHORT TERM...(TODAY THROUGH WEDNESDAY)
ISSUED AT 330 AM EDT MON APR 25 2016

STILL MONITORING THE RISK FOR A FEW STRONG STORMS.  THESE APPEAR
MOST PROBABLE THIS EVENING INTO LATE TONIGHT AS SURFACE LOW PRESSURE
APPROACHES THE AREA.  QUIET AND COOL WEATHER SHOULD PREVAIL BY LATE
TUESDAY MORNING INTO WEDNESDAY.

THE SURFACE BOUNDARY HAS SAGGED SOUTH TO NEAR I-94 EARLY THIS
MORNING.  HOWEVER IT WILL DRIFT BACK NORTHWARD TODAY TO ABOUT I-96
BY THIS EVENING.  THIS WILL ALLOW SURFACE BASED INSTABILITY TO OCCUR
FROM I-96 SOUTHWARD BY EVENING AND COULD SPAWN A FEW STRONGER STORMS.

HOWEVER THERE ARE A COUPLE THINGS RUNNING AGAINST STRONGER STORMS
TOO.  THE JET DYNAMICS AND THE BEST INSTABILITY DOES NOT MOVE INTO
THE CWA UNTIL AFTER NIGHTFALL.  THIS DOES NOT FAVOR ORGANIZED
STORMS.  WE DO HAVE A COUPLED JET STRUCTURE THAT PASSES THROUGH
AROUND MIDNIGHT AND THIS IS ALSO AROUND THE TIME OF THE BEST
INSTABILITY...HOWEVER THIS ISN/T USUALLY THE BEST TIME FOR SEVERE
STORMS.  STILL LIKE THE SPC OUTLOOK FOR THE NEXT 24 HOURS...WITH
GENERALLY A MARGINAL SET UP FOR SEVERE STORMS.  BUT IF THEY WERE TO
OCCUR IT WOULD SEEM THE MOST PROBABLE WINDOW WOULD BE FROM ROUGHLY
7PM TO 3AM THIS EVENING AND TONIGHT.  WITH THE SURFACE BOUNDARY
SITTING BETWEEN I-96 AND I-94 IT IS NOT OUT OF THE QUESTION WE COULD
SEE A BRIEF TOR SPIN-UP OR TWO.

BESIDES THE OUTSIDE CHANCE OF SEVERE STORMS...WE WILL SEE A WELCOME
RAINFALL WITH PCPN COVERAGE EXPECTED TO EXPAND FROM CENTRAL LOWER BY
AFTERNOON AND INTO SOUTHERN LOWER BY EARLY EVENING.  MOST AREAS
SHOULD PICK UP A HALF TO THREE QUARTERS OF AN INCH OF RAIN...WITH
LOCALLY HIGHER AMOUNTS IN CONVECTION.

THE UPPER WAVE SLIDES BY TUESDAY MORNING AND A FEW SHOWERS MAY
LINGER NORTH OF I-96 THROUGH MID DAY.  THEN WE SHOULD DRY OUT AND
CLEAR.

TUESDAY NIGHT WILL BE COLD ENOUGH FOR FROST...BUT NE WINDS SHOULD
REMAIN UP...LIMITING ANY HARD FROST.  SO NOT EXPECTING WE WILL NEED
ANY HEADLINE AT THIS POINT.

.LONG TERM...(WEDNESDAY NIGHT THROUGH SUNDAY)
ISSUED AT 330 AM EDT MON APR 25 2016

UPPER PATTERN RECENTLY HAS REVOLVED AROUND A BLOCKING HIGH OVER
GREENLAND WITH AN UPPER VORTEX SPINNING OVER EASTERN CANADA. WHAT
THIS HAS MEANT FOR US IN THE GREAT LAKES...IS SYSTEMS SPINNING OUT
OF THE WEST AND LOSING PUNCH AS THEY MOVE INTO CONFLUENT FLOW. THE
BLOCKING PATTERN BREAKS DOWN OVER TIME IN THE LONG TERM...BUT WE
WILL SEE A COUPLE SIMILAR SYSTEMS AFFECT US BEFORE THEN.

THE FIRST SYSTEM IN THE LONG TERM IS CURRENTLY SEEN IN WATER VAPOR
PLOWING THROUGH CALIFORNIA. IT LIFTS INTO THE PLAINS ON TUESDAY AND
MOVES TOWARD US ON WEDNESDAY. SHOWERS ARE EXPECTED WITH THIS SYSTEM
FROM WEDNESDAY NIGHT THROUGH THURSDAY EVENING...BUT AGAIN THE SYSTEM
WILL BE LOSING ENERGY AS IT DE-AMPLIFIES. EVERYONE WILL SEE
RAIN...BUT AMOUNTS DO NOT LOOK TOO SIGNIFICANT. THERE MAY BE A
LITTLE THUNDER WITH THIS SYSTEM IN THE FAR SOUTH NEAR I-94 AS 850MB
LI VALUES DIP TO AROUND -1C.

WE DRY OUT FOR FRIDAY AND THEN THE FORECAST BECOMES A BIT MORE
UNCERTAIN OVER THE WEEKEND. THE GFS KEEPS US MUCH DRIER WHEREAS THE
ECMWF LIFTS THE NEXT LOW CLOSER TO THE GREAT LAKES ACROSS NORTHERN
INDIANA. BY THIS TIME THE BLOCKING DOWNSTREAM PATTERN WILL HAVE
SHIFTED AND THE FURTHER NORTH LOW COULD VERIFY. THAT SAID...GFS
ENSEMBLE MEANS HAVE A PRETTY STOUT SURFACE HIGH SITUATED ACROSS THE
GREAT LAKES THIS WEEKEND. TRIED TO TREND POPS DOWN THIS WEEKEND IN
OUR GRIDDED DATABASE. AT THIS POINT JUST HAVE CHANCE POPS (30-50PCT)
IN OVER THE WEEKEND AND WE WILL WATCH WHICH WAY THE TRENDS LEAD US.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z MONDAY NIGHT)
ISSUED AT 1158 PM EDT SUN APR 24 2016

VFR WEATHER WILL CONTINUE OVERNIGHT AND MONDAY WITH CLOUD BASES
AOA 5000 FT. TONIGHT AND EARLY MONDAY WILL BE PREDOMINATELY DRY...
WITH SCATTERED SHOWERS DEVELOPING BY MONDAY AFTERNOON. WHILE A
TSTM IS POSSIBLE AFTER 18Z MONDAY... THE MAIN CHANCE FOR
THUNDERSTORMS SHOULD HOLD OFF UNTIL AFTER 00Z TUESDAY WHEN THE
SFC LOW APPROACHES FROM SRN WISCONSIN.

&&

.MARINE...
ISSUED AT 330 AM EDT MON APR 25 2016

SSE FLOW WILL KEEP WAVES IN CHECK TODAY AND MOST OF TONIGHT. HOWEVER
AS THE SURFACE LOW PASSES LATE TONIGHT NORTHERLY FLOW WILL TAKE
OVER.  WE MAY NEED A SMALL CRAFT ADVISORY TOWARD DAYBREAK TUESDAY
AND LAST THROUGH MUCH OF THE DAY BEFORE WE SEE A DIMINISHING TREND.

&&

.HYDROLOGY...
ISSUED AT 1255 PM EDT SUN APR 24 2016

MOST OF THE RAINFALL OVER THE NEXT COUPLE OF DAYS IS EXPECTED MONDAY
AFTERNOON THROUGH MONDAY NIGHT. HEAVIER SHOWERS AND SOME STRONG
STORMS WILL BE CAPABLE OF PRODUCING LOCALLY HEAVY RAINFALL...
ESPECIALLY MONDAY EVENING AND MONDAY NIGHT. MOST BASINS WILL SEE
OVER A HALF INCH OF RAIN... WHILE STRONG THUNDERSTORMS AND TRAINING
OVER THE SAME AREAS COULD PRODUCE OVER AN INCH LOCALLY. EXPECT
PONDING OF WATER/LOCALIZED MINOR FLOODING IN POOR DRAINAGE AREAS IF
THIS OCCURS.

RIVER RISES ARE LIKELY... AND SOME RIVERS MAY RISE ABOVE BANKFULL
THIS WEEK. THE MAIN IMPACT WILL BE NUISANCE FLOODING NEAR RIVER
BANKS.

&&

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

$$

SYNOPSIS...JK
SHORT TERM...JK
LONG TERM...DUKE
AVIATION...MEADE
HYDROLOGY...EBW
MARINE...JK



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