Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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000
FXUS63 KGRR 270352
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
1152 PM EDT SAT JUL 26 2014

LATEST UPDATE...
AVIATION

.SYNOPSIS...
ISSUED AT 321 PM EDT SAT JUL 26 2014

SHOWERS AND THUNDERSTORMS ARE LIKELY SUNDAY AS A LOW PRESSURE SYSTEM
TRACKS SOUTHEAST THROUGH THE GREAT LAKES REGION. NORTH WINDS BEHIND
THIS SYSTEM WILL DRIVE IN MUCH COLDER AIR TO START NEXT WEEK... WITH
HIGHS ONLY AROUND 70 ON MONDAY. TEMPERATURES WILL MODERATE BACK INTO
THE UPPER 70S BY MIDWEEK.

&&

.UPDATE...
ISSUED AT 813 PM EDT SAT JUL 26 2014

UPDATED THE NORTHEAST COUNTIES TO INCLUDE SCATTERED TSRA THIS
EVENING. A SOUTHWARD GROUP OF THUNDERSTORMS HAS REMAINED INTACT AS
IT APPROACHES THE FAR NE CWA.

&&

.SHORT TERM...(THIS EVENING THROUGH MONDAY NIGHT)
ISSUED AT 321 PM EDT SAT JUL 26 2014

FCST FOCUS IS ON STRONG TO SEVERE THUNDERSTORM POTENTIAL ON SUNDAY
AS UNSEASONABLY STRONG SHORTWAVE CURRENTLY NEAR LAKE WINNIPEG DIVES
SOUTHEAST. MAIN WINDOW/AREA OF CONCERN SUNDAY IS FROM ROUGHLY 11 AM
TO 5 PM /15Z-21Z/ SOUTH AND EAST OF GRR. THIS IS WHEN/WHERE MAX
INSTABILITY OF 2000-3000 J/KG IS PROGGED AND WILL BE WORKING IN
CONCERT WITH ABOUT 40 KTS OF 0-6KM BULK SHEAR.

FCST SOUNDINGS 15Z-18Z SUNDAY SOUTHEAST OF GRR EXHIBIT FAT
CAPE PROFILES INDICATIVE OF A LARGE HAIL THREAT. APPROACH OF THE
UPPER LOW/COLDER TEMPS ALOFT LEADS TO STEEPENING MID LEVEL LAPSE
RATES WHILE SFC DEW PTS ARE STILL 65-70F. THE HAIL THREAT WILL BE
HIGHEST WITH THE INITIAL CELLS THAT DEVELOP LATE MORNING INTO EARLY
AFTERNOON. DAMAGING WINDS ARE POSSIBLE AS WELL WITH ANY ORGANIZED
CLUSTERS OF STORMS THAT DEVELOP A COLD POOL.

THE THREAT FOR SVR WX APPEARS TO END BY LATE AFTERNOON AS BOTH CAPE
AND SHEAR VALUES ARE PROGGED TO DROP OFF. THE LOW LEVEL FLOW GOES
WEST THEN NORTHWEST IN RESPONSE TO THE SFC TROUGH BECOMING MORE
PRONOUNCED ACROSS NRN LWR MI AND THE THUMB AREA. MODELS FOCUS BEST
QPF AND MOST PERSISTENT CONVECTION ALONG THE AXIS OF THIS TROUGH...
ROUGHLY TVC TO MBS TO PT HURON. THIS INCLUDES THE CLARE/MT
PLEASANT/ALMA AREAS WHERE UP TO AN INCH OF RAIN COULD FALL.
OTHERWISE RAIN AMOUNTS EXPECTED TO GENERALLY BE 0.25 TO 0.50... WITH
CONVECTION BECOMING MUCH MORE SCATTERED LATER IN THE DAY IN THE SW
HALF OF THE CWFA AS STABILIZING WEST/NORTHWEST LOW LEVEL FLOW
DEVELOPS AND DEW PTS BEGIN TO FALL.

LINGERING SHOWERS ENDING LATE SUNDAY NIGHT FOLLOWED BY BREEZY/COOL
CONDITIONS MONDAY. CU/STRATOCU COULD BE EXTENSIVE MONDAY GIVEN
STRONG COLD ADVECTION PATTERN.

.LONG TERM...(TUESDAY THROUGH SATURDAY)
ISSUED AT 321 PM EDT SAT JUL 26 2014

THE HIGH AMPLITUDE UPPER LEVEL TROUGH WILL CONTINUE TO DOMINATE THE
WX PATTERN THROUGH MOST OF THE LONG TERM FORECAST PERIOD. TEMPS WILL
AVERAGE 5 TO 10 DEGREES BELOW NORMAL TUESDAY BEFORE MODERATING
SLIGHTLY TO CLOSER TO NORMAL FOR MID TO LATE WEEK.

SCATTERED DIURNALLY DRIVEN AFTERNOON AND EARLY EVENING SHOWERS AND
PERHAPS A FEW STORMS ARE POSSIBLE MID TO LATE WEEK. HOWEVER
PREDOMINANTLY DRY WX SHOULD PREVAIL THROUGH MOST OF THE LONG RANGE
FCST PERIOD.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SUNDAY NIGHT)
ISSUED AT 1152 PM EDT SAT JUL 26 2014

MY THINKING HAS NOT CHANGED MUCH FROM THE 00Z TAFS...FOG WITH IFR
CONDITIONS AT ALL TAF SITES BY 12Z. THEN SHOWERS AND THUNDERSTORMS
DEVELOPING BY LATE MORNING AND CONTINUING INTO LATE AFTERNOON
BEFORE THE COLD FRONT COMES THROUGH TO CLEAR THEM OUT.

SKIES HAVE CLEARED AS I THROUGH THEY WOULD. NOW FOG IS
DEVELOPING... BIV IS ALREADY 2 MILES IN FOG. MANY OTHER LOCATIONS
HAVE MVFR VISIBILITIES. WITH DEW POINTS EXPECTED TO INCREASE TOWARD
MORNING THIS IS A GOOD SET OF FOR FOG AND LOW CLOUDS. THE RAP
MODEL SHOW MOST AREAS NEAR AND SOUTH OF I-96 WITH FOG BY 12Z.

AS FOR THE CONVECTION...WITH SUCH A DYNAMIC UPPER LEVEL SYSTEM
MOVING THROUGH THE LOWER MICHIGAN SUNDAY AND CONSIDERING THERE IS
ALREADY CONVECTION OVER NW WI...NORTH INTO ONTARIO AHEAD OF THE
UPPER LOW IT WOULD SEEM THERE IS LITTLE QUESTION THERE WILL BE
PRECIPITATION AT ALL TAF SITES SUNDAY. I TIMED THE SHOWER FROM WEST
TO EAST. I WOULD THINK THE FOG SHOULD MIX OUT QUICKLY BY MID
MORNING AT THE SYSTEM INCREASES MIXING.

&&

.MARINE...
ISSUED AT 321 PM EDT SAT JUL 26 2014

SMALL CRAFT ADVISORIES/BEACH HAZARD STATEMENTS WILL BE NEEDED FOR
SUNDAY NIGHT INTO MONDAY DUE TO STRONG NORTH WINDS TO 30 KTS. WAVES
OF 4 TO 7 FT EXPECTED... HIGHEST SOUTH OF HOLLAND.

PATCHY FOG/HAZE POSSIBLE OVER THE LK MI NEARSHORE TONIGHT INTO
SUNDAY AS DEW POINTS IN THE MID TO UPPER 60S MOVE OVER COLD WATER
TEMPS IN THE 50S NEAR THE COAST.


&&

.HYDROLOGY...
ISSUED AT 1207 PM EDT SAT JUL 26 2014

THE MAIN PRECIPITATION THREAT WILL BE SUNDAY AS MOISTURE EDGES UP
INTO THE AREA. PWAT VALUES PUSH BETWEEN 1.0 TO 1.5 INCHES DURING
THE AFTERNOON. THIS MAY RESULT IN LOCALIZED HEAVY RAINFALL IN AND
AROUND THUNDERSTORMS. HOWEVER...AREA AVERAGES ARE MORE LIKELY TO
RANGE FROM ONE-QUARTER TO ONE-HALF AN INCH. PRECIPITATION THEN
SEEMS TO LINGER INTO MONDAY BUT SHOULD NOT BE OF ANY GREAT
SIGNIFICANCE IN THE MONDAY MORNING TIME FRAME.

ASIDE FROM SUNDAYS FOCUS...WE WILL SEE MAINLY DRY CONDITIONS TODAY.
ADDITIONAL CHANCES FOR LIGHT RAIN EXIST AS WE HEAD THROUGH THE NEW
WORK WEEK. NO HIGH END PRECIPITATION EVENTS ARE ANTICIPATED TO AFFECT
THE AREA. RIVERS CONTINUE TO RUN WELL BELOW ACTION STAGE...SO NO
CONCERN FOR RIVER FLOODING AT THIS TIME.

&&

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

$$

UPDATE...93
SYNOPSIS...MEADE
SHORT TERM...MEADE
LONG TERM...LAURENS
AVIATION...WDM
HYDROLOGY...JAM
MARINE...MEADE





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