Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 251901
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
300 PM EDT FRI JUL 25 2014

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

.SYNOPSIS...
ISSUED AT 300 PM EDT FRI JUL 25 2014

THE ARRIVAL OF A WARMER AND MORE HUMID AIR MASS WILL BRING A THREAT
OF A FEW SHOWERS AND THUNDERSTORMS THIS WEEKEND. SATURDAY LOOKS LIKE
THE DRIER OF THE TWO DAYS... WITH THE BETTER CHANCE OF RAIN ON
SUNDAY AFTERNOON AND EVENING. THE PRIMARY RISK OF SEVERE
THUNDERSTORMS OVER THE WEEKEND WILL BE SOUTH OF MICHIGAN.

MUCH COLDER WEATHER WILL MOVE IN FOR MONDAY WITH HIGHS STRUGGLING TO
REACH 70. TEMPERATURES MOST OF NEXT WEEK WILL REMAIN BELOW NORMAL
WITH A RISK OF A SHOWER OR STORM MAINLY INLAND FROM LAKE MICHIGAN.

&&

.SHORT TERM...(THIS EVENING THROUGH SUNDAY NIGHT)
ISSUED AT 300 PM EDT FRI JUL 25 2014

THE MAIN FCST CHALLENGE IS CONVECTIVE POTENTIAL AND TIMING OVER THE
WEEKEND. THE BEST RISK IS ON SUNDAY AFTERNOON AND EVENING WITH THE
ARRIVAL OF A STRONG SHORTWAVE DROPPING DOWN FROM THE NORTHWEST.

12Z MODELS HAVE BACKED OFF A BIT ON POPS/QPF TONIGHT... LIKELY
RELATED TO THE LACK OF A FOCUSED LOW LEVEL JET AND RELATIVELY WEAK
MOISTURE TRANSPORT. WILL KEEP POPS IN THE CHANCE CATEGORY.

INSTABILITY INCREASES ON SATURDAY WITH THE ARRIVAL OF SFC DEW POINTS
IN THE MID TO UPPER 60S. SB CAPES OVER 2000 J/KG ARE PROGGED IN THE
AFTERNOON INLAND FROM LAKE MICHIGAN... WHICH COMBINED WITH DEEP
LAYER SHEAR OVER 40 KTS COULD SUPPORT SOME HEALTHY STORMS.

HOWEVER AN IMPETUS FOR CONVECTIVE INITIATION OVER SW MI ON SATURDAY
IS VERY QUESTIONABLE SINCE THE SFC FRONT SHOULD BE JUST SOUTH OF THE
MI/IN BORDER. ONLY CHC/SLGT CHC POPS SEEM WARRANTED WITH THE BEST
SFC CONVERGENCE EXPECTED TO BE LOCATED TO OUR SOUTH AND ALSO TO OUR
EAST ACROSS ERN LWR MI.

CONVECTIVE POTENTIAL ON SATURDAY NIGHT IS NOT GOOD EITHER DUE TO THE
LACK OF A LOW LEVEL JET/FORCING... DESPITE GOOD INSTABILITY WITH MU
CAPES OVER 2500 J/KG.

CONVECTIVE POTENTIAL DOES HOWEVER INCREASE ON SUNDAY AS APCHG STRONG
SHORTWAVE INDUCES A SFC LOW/TROUGH OVER LWR MI. COMBO OF H5 HEIGHT
FALLS... STRONG SFC CONVERGENCE... AND CAPES OF 1500-2000 J/KG WILL
MAKE TSTMS LIKELY. A SVR WX THREAT COULD DEVELOP SOUTH AND EAST OF
GRR WHERE BEST DEEP SHEAR OVER 35 KTS IS PROGGED. DEEP LAYER SHEAR
ON SUNDAY DECREASES FARTHER NORTH AND WEST.

.LONG TERM...(MONDAY THROUGH FRIDAY)
ISSUED AT 300 PM EDT FRI JUL 25 2014

TEMPERATURES WILL AVERAGE AT LEAST 5 TO 10 DEGREES BELOW NORMAL
EARLY NEXT WEEK AS THE UPPER LEVEL TROUGH CONTINUES TO AMPLIFY OVER
OUR REGION. SOME MAINLY DIURNALLY DRIVEN SHOWERS AND PERHAPS A FEW
STORMS ARE POSSIBLE DUE TO INSTABILITY FROM DAYTIME HEATING AND WITH
THE POOL OF COLD AIR ALOFT UNDER THE UPPER LEVEL TROUGH.

TEMPS MAY MODERATE JUST A BIT TOWARD MID TO LATE NEXT WEEK BUT WILL
CONTINUE TO AVERAGE A LITTLE BELOW NORMAL AS THE UPPER LEVEL TROUGH
REMAINS FIRMLY ENTRENCHED OVER THE GREAT LAKES REGION. THERE IS A
CONTINUED CHANCE OF A FEW SHOWERS MAINLY NEAR TO EAST OF US-131
MAINLY DURING THE AFTERNOON/EARLY EVENING HOURS DAILY.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SATURDAY)
ISSUED AT 1215 PM EDT FRI JUL 25 2014

VFR CONDITIONS WILL CONTINUE THIS AFTERNOON AND EVENING. SCATTERED
SHOWERS AND PERHAPS AN ISOLATED THUNDERSTORM WILL DEVELOP LATE THIS
EVENING AND OVERNIGHT. CONDITIONS WILL GRADUALLY DETERIORATE FROM
VFR TO MVFR DURING THE EARLY MORNING HOURS SATURDAY AS LOWER CLOUDS
AND STEADIER SHOWERS MOVE IN.

SHOWERS SHOULD GRADUALLY TAPER OFF DURING THE MID TO LATE MORNING
HOURS SATURDAY BUT CONDITIONS WILL LIKELY REMAIN MVFR THROUGH AT
LEAST MIDDAY SATURDAY DUE TO LOW CLOUDS.

&&

.MARINE...
ISSUED AT 300 PM EDT FRI JUL 25 2014

GUIDANCE HAS NOT BEEN CONSISTENT OR IN GOOD AGREEMENT REGARDING THE
POTENTIAL FOR STRONG SOUTH WINDS OVER LK MI TONIGHT AND SATURDAY
MORNING. THE LATEST 12Z GUIDANCE IS NOT AS AGGRESSIVE AS THE 00Z
GUIDANCE... SO WILL TONE DOWN WINDS AND WAVES A BIT FOR TONIGHT.

THERE IS VERY HIGH CONFIDENCE IN A STRONG NORTH FLOW EVENT OVER LK
MI ON SUNDAY NIGHT AND MONDAY WHICH WILL REQUIRE SMALL CRAFT
ADVISORIES AND BEACH HAZARD STATEMENTS.

&&

.HYDROLOGY...
ISSUED AT 1206 AM EDT FRI JUL 25 2014

AFTER A STRETCH OF MAINLY DRY CONDITIONS FOR THE MAJORITY OF THE AREA
WE WILL SEE MULTIPLE CHANCES OF RAIN OVER THE NEXT SEVERAL DAYS.
ONE ROUND WILL DEVELOP AND MOVE THROUGH LATE TONIGHT AND INTO
SATURDAY MORNING WHILE THE ANOTHER ROUND WILL DEVELOP SUNDAY
AFTERNOON AND EVENING. AREA WIDE...TOTALS SHOULD AVERAGE OUT
AROUND ONE-QUARTER TO ONE-HALF INCH THROUGH SUNDAY. LOCALIZED HEAVIER
RAINFALL IS EXPECTED IN AND AROUND THUNDERSTORMS WHERE AMOUNTS ARE
LIKELY BE BE HIGHER.

ADDITIONAL CHANCES FOR RAIN EXIST GOING INTO NEXT WEEK. AT THIS
POINT LONG TERM 5-7 DAY TOTALS ARE MORE ON THE BENEFICIAL SIDE
WITH RECENT DRY WEATHER. OVERALL...RIVER FLOODING DOES NOT LOOK
LIKELY. ANTICIPATED RAINFALL SHOULD ONLY RESULT IN MINOR RISES.

&&

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

$$

SYNOPSIS...MEADE
SHORT TERM...MEADE
LONG TERM...LAURENS
AVIATION...LAURENS
HYDROLOGY...JAM
MARINE...MEADE








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