Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 261916
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
316 PM EDT SUN JUL 26 2015

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

.SYNOPSIS...
ISSUED AT 236 PM EDT SUN JUL 26 2015

DRY WEATHER PREVAILS ALONG WITH WARM TEMPERATURES THROUGH MID WEEK
BEFORE THE NEXT CHANCE OF RAIN ARRIVES LATE TUESDAY NIGHT AND
WEDNESDAY. COOLER TEMPERATURES WILL BE FEATURED FOR THE SECOND
HALF OF THE WEEK AND WEEKEND...THOUGH 80 OR BETTER IS STILL
FORECAST.

&&

.SHORT TERM...(THIS EVENING THROUGH TUESDAY NIGHT)
ISSUED AT 236 PM EDT SUN JUL 26 2015

PRIMARY FOCUS CENTERS ON PRECIP CHANCES LATE TUESDAY NIGHT AND
WEDNESDAY. OVERALL...SOME THUNDERSTORMS WILL LIKELY IMPACT WESTERN
LOWER MI LATE TUESDAY NIGHT AND SOME ADDITIONAL SHOWERS AND
THUNDERSTORMS MAY DEVELOP ACROSS CENTRAL AND SOUTH CENTRAL LOWER
MI WEDNESDAY DURING THE DAY WEDNESDAY. SEVERE WEATHER IS NOT
EXPECTED THOUGH LOCALLY HEAVY RAIN IS POSSIBLE.

A POTENT MID LEVEL WAVE IS SHOWN BY THE NUMERICAL MODELS OVER MT
AND NORTHERN SD BY 12Z TUESDAY...WITH ASSOCIATED SFC LOW POSSIBLY
SUB 990MB NEAR THE CANADIAN BORDER. THIS STRONG SYSTEM WILL LIFT
TOWARD HUDSON BAY BUT THE COLD FRONT WILL MAKE ITS WAY THROUGH THE
GREAT LAKES BY WEDNESDAY. AHEAD OF THE FRONT...NUMEROUS SHOWERS
AND STORMS ARE EXPECTED ACROSS THE MIDWEST TUESDAY AND TUESDAY
NIGHT. HOWEVER...WEAK DEEP LAYER SHEAR WILL ACT AS A HINDRANCE TO
STRONGER STORMS...SO MAINLY DISORGANIZED MULTICELL CONVECTION IS
EXPECTED AHEAD OF AND ALONG THE FRONT.

WHAT LITTLE DEEP LAYER SHEAR IS AVAILABLE APPEARS TO BE MAXIMIZED
OVER EASTERN WISCONSIN...LAKE MICHIGAN...AND OUR FAR NW COUNTIES
LATE TUESDAY NIGHT/EARLY WEDNESDAY MORNING. THIS IS WHERE
SUSTAINED CONVECTION HAS THE BEST OPPORTUNITY TO EXIST IN THE
MIDST OF ELEVATED CAPE OF 500-1000 J/KG. THERE COULD BE A LOCAL
HAIL THREAT BUT OTHERWISE JUST GENERAL SHOWERS/THUNDERSTORMS ARE
EXPECTED ALONG WITH POTENTIALLY HEAVY RAIN (SEE BELOW).

DURING THE DAY WEDNESDAY...THE SPEED OF FROPA WILL BE IMPORTANT.
SLOWER TIMING MAY AFFORD AREAS LIKE LANSING AND JACKSON TO SEE
SOME STRONGER STORMS POP IN THE EARLY/MID AFTERNOON HOURS. GFS
BUFKIT SOUNDINGS FOR JXN AT 18Z WED REVEAL >2000 J/KG...MAXIMIZED
NEAR THE -10 TO -20C LAYER. LOCALLY LARGE HAIL IS POSSIBLE IF THIS
OCCURS...BUT DEEP LAYER SHEAR WILL ONLY BE 20-25 KTS. STILL...SFC
BASED LI VALUES LOOK REASONABLY NEGATIVE ACROSS THE SE COUNTIES SO
STILL NEED TO MENTION A THREAT FOR A FEW LOCALLY STRONG STORMS.

WITH REGARD TO QPF...MODEL AREAL AMOUNTS INDICATE 0.25-0.50"
ACROSS THE AREA...BUT THAT WILL BE TOO LOW WHERE CONVECTION
FORMS. DEW POINTS ARE EXPECTED TO SURGE INTO THE 70S AHEAD OF THE
FRONT AND THE NAM/GFS ARE BOTH SHOWING PW VALUES OF 2.00-2.30"
ACROSS THE CWA BY 12Z WED...AND THE ECMWF IS SHOWING VALUES UP TO
A WHOPPING 2.50" MOVING OVERHEAD. WHILE PROBABLY OVERDONE BY THE
MODELS...THE ATMOSPHERE WILL HAVE A GREAT CAPACITY TO DUMP LARGE
AMOUNTS OF RAIN WHERE THE CONVECTION DOES FORM. THIS WILL NEED TO
BE CLOSELY MONITORED.

&&

.LONG TERM...(WEDNESDAY THROUGH SUNDAY)
ISSUED AT 236 PM EDT SUN JUL 26 2015

A SIGNIFICANT LARGE SCALE UPPER LEVEL PATTERN READJUSTMENT WILL BEGIN
DURING THE SECOND HALF OF THIS COMING WEEK. THIS SIGNALS A TREND
TOWARD COOLER TEMPERATURES FOR SOUTHWEST LOWER MICHIGAN. THIS
TREND WILL CONTINUE WELL BEYOND THIS FORECAST PERIOD. AFTER NEARLY
A WEEK WITH A CENTRAL CONUS UPPER RIDGE AND TROUGHS ON EACH
COAST...THE UPPER RIDGE BEGINS RETROGRADING TO THE WESTERN CONUS.
THE LONGWAVE TROUGH THAT WAS OFF THE WEST COAST PROGRESSES
EASTWARD TO CENTRAL CANADA AND INTO THE CENTRAL AND EASTERN CONUS.
THIS HAPPENS IN SEVERAL STAGES...EACH SHORTWAVE THAT MOVES ACROSS
THE CANADIAN /CONUS BOARDER WILL DEEPEN THE EASTERN TROUGH JUST A
LITTLE MORE. WHICH IN TURN MEANS COOLER TEMPERATURES. THE
ENSEMBLES OF BOTH THE GFS AND ECMWF AND OPERATIONAL MODELS ALL
HAVE BEEN FORECASTING THIS FOR OVER A WEEK NOW. DETAILS MAY CHANGE
BUT THE OVERALL PICTURE SEEMS SOLID.

THE NEGATIVE ASPECT OF THIS IS IT WOULD SEEM LITTLE IF ANY
SIGNIFICANT PRECIPITATION SEEMS LIKELY DURING THIS TIME PERIOD. ANY
SHORTWAVES COMING THROUGH THE AREA WILL BE FROM THE NORTHERN STREAM
AND HAVE LIMITED MOISTURE WITH THEM.

THE FIRST SYSTEM THAT HELPS THIS CAUSE OF AN EAST COAST TROUGH IS
THE COLD FRONT THAT COMES THROUGH WEDNESDAY... THAT IS FOLLOWED BY
SHORTWAVE RIDGING AND MODIFIED CANADIAN POLAR AIR (NEAR NORMAL
TEMPERATURES). THE NEXT SYSTEM COMES THROUGH NEXT WEEKEND. THAT WILL
BRING THE RISK OF SHOWERS AND THUNDERSTORMS BUT DO NOT LOOK FOR A
LARGE AMOUNT OF RAINFALL WITH THIS SYSTEM. WHAT WILL FOLLOW IT IS
THE COOLEST TEMPERATURES WE HAVE SEEN IN SEVERAL WEEKS.

BOTTOM LINE... WE BEGIN THE SLOW FADE TO FALL.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z MONDAY AFTERNOON)
ISSUED AT 118 PM EDT SUN JUL 26 2015

ALL TAF SITES ARE VFR AND SHOULD STAY THAT WAY THROUGH MONDAY. THE
SHOWER ACTIVITY SOUTH AND WEST OF CHICAGO IS NOT EXPECTED TO
REACH OUR TAF SITES. ONLY THE LAYERED MID AND HIGH CLOUDS FROM
THAT CONVECTION WILL IMPACT THE TAF SITES THIS AFTERNOON. THOSE
CLOUDS SHOULD CLEAR OUT EARLY THIS EVENING LEAVING SKIES CLEAR
THROUGH THEN NIGHT.

THANKS TO HIGH PRESSURE MOVING OVER THE AREA...WINDS WILL BE LIGHT
AND VARIABLE OR CALM TONIGHT. WITH THE CLEAR SKIES FOG IS NOT
TOTALLY OUT OF THE QUESTION BUT WITH DEW POINTS IN THE LOWER 60S
GETTING TEMPERATURES DOWN TO THE DEW POINT TO CREATE FOG LOOKS
MUCH LESS LIKELY THAN IT WAS LAST NIGHT.

LIGHT WINDS AND MOSTLY CLEAR SKIES ARE EXPECTED MONDAY. THE HIGH
CLOUDS FROM ANY UPSTREAM CONVECTION SHOULD STREAM MORE TO THE
SOUTH SOUTHEAST DUE TO THE BUILDING UPSTREAM UPPER LEVEL RIDGE
JUST WEST OF HERE.


&&

.MARINE...
ISSUED AT 236 PM EDT SUN JUL 26 2015

QUIET CONDITIONS OVER THE LAKE EXPECTED UNTIL TUESDAY WHEN
SOUTHERLY WINDS INCREASE AHEAD OF A COLD FRONT. EXPECT 1 TO 3
FOOTERS TUESDAY AND POSSIBLY HIGHER TUESDAY NIGHT/WEDNESDAY
MORNING AS WINDS TURN SW AND THEN W.

&&

.HYDROLOGY...
ISSUED AT 1053 AM EDT SUN JUL 26 2015

HYDRO WORLD CONTINUES TO BE UNEVENTFUL WITH NO CONCERNS UNTIL
TUESDAY NIGHT AND WEDNESDAY.

DRY WEATHER WILL CONTINUE TODAY THROUGH MUCH OF TUESDAY BEFORE
THE NEXT CHANCE OF RAIN APPROACHES TUESDAY NIGHT INTO WEDNESDAY.
THE MID-WEEK EVENT DOES NOT LOOK TOO IMPRESSIVE FOR WIDESPREAD
HEAVIER RAINFALL...BUT LOCALLY HEAVY RAIN MAY BE POSSIBLE WHEN
THE TIME COMES. STREAMS AND RIVERS ARE RUNNING WELL BELOW ANY
PRODUCT CRITERIA AND WILL BE ABLE TO HANDLE WHAT IS FORECAST.

&&

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

$$

SYNOPSIS...HOVING
SHORT TERM...HOVING
LONG TERM...WDM
AVIATION...WDM
HYDROLOGY...JAM
MARINE...HOVING


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