Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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000
FXUS63 KGRR 191548
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
1148 AM EDT TUE AUG 19 2014

LATEST UPDATE...
MESOSCALE DISCUSSION

.MESOSCALE DISCUSSION...
ISSUED AT 1148 AM EDT TUE AUG 19 2014

NEW STORMS HAVE DEVELOPED JUST WEST AND NORTH OF GRR IN AREA OF
BEST DEEP LAYER MOISTURE FLUX CONVERGENCE. THIS ACTIVITY IS STILL
ROOTED ABOVE THE BOUNDARY LAYER ALTHOUGH SFC BASED INSTABILITY IS
QUICKLY BUILDING SOUTH AND EAST OF GRR WHERE SKIES HAVE CLEARED.

THEREFORE SUSPECT THAT THIS CONVECTION WILL INCREASE IN INTENSITY
AS IT MOVES SOUTHEAST OVER THE NEXT FEW HOURS. THE SOUTHERN END OF
THE LINE WILL PROBABLY EXPAND FARTHER SOUTHWEST... POSSIBLY CONNECTING
UP WITH THE CONVECTION CURRENTLY IN CENTRAL ILLINOIS.

ALSO... EVENTUALLY TOWARD MID AFTERNOON... A LAKE SHADOW SHOULD
DEVELOP IN THE WAKE OF THE LINE WHICH WOULD PROBABLY ENHANCE SFC
CONVERGENCE ALONG ROUGHLY AN AZO TO IONIA LINE. 0-6KM DEEP LAYER
SHEAR IS CURRENTLY NUDGING UP TO AROUND 30KTS SUGGESTING THIS
COULD ORGANIZE INTO A BKN TO SOLID LINE WITH THE POSSIBILITY OF
WIND DAMAGE AND PERHAPS SOME LARGE HAIL SOUTH AND EAST OF GRR.

&&

.SYNOPSIS...
ISSUED AT 325 AM EDT TUE AUG 19 2014

A WARMER AND MORE HUMID WEATHER PATTERN WILL CONTINUE TO DEVELOP
THIS WEEK WITH POTENTIAL FOR SEVERAL ROUNDS OF SHOWERS AND
THUNDERSTORMS. SHOWERS AND THUNDERSTORMS ARE LIKELY TODAY. MORE
SHOWERS AND STORMS ARE EXPECTED FOR LATE IN THE WEEK INTO THE
WEEKEND.

&&

.SHORT TERM...(TODAY THROUGH THURSDAY)
ISSUED AT 325 AM EDT TUE AUG 19 2014

SHOWERS AND THUNDERSTORMS ARE LIKELY TODAY AS AN UPPER LEVEL LOW
PRESSURE SYSTEM CONTINUES TO ADVANCE SE INTO OUR REGION ALONG WITH
A WEAK SFC LOW. CONVECTION OVER SE WISCONSIN SHOULD CONTINUE TO
GRADUALLY WEAKEN AS IT MOVES TOWARD OUR AREA EARLY THIS MORNING AS
SUGGESTED BY 00Z NSSL WRF GUIDANCE.

THE BEST CHANCE FOR ISOLATED SEVERE STORMS SHOULD COME MID TO LATE
AFTERNOON OVER OUR SE FCST AREA WHEN INSTABILITY WILL BE MAXIMIZED
AS SB CAPE VALUES POTENTIALLY REACH UP TO AROUND 2000 J/KG OVER THAT
AREA. THIS NOTION IS SUPPORTED BY 00Z 4KM NSSL WRF SIM Z GUIDANCE.
STRONGER STORMS WILL ALSO BE CAPABLE OF PRODUCING BRIEFLY HEAVY
RAINFALL WITH PRECIPITABLE WATER VALUES UP INTO THE 1.5 TO 1.75 INCH
RANGE THROUGH EARLY AFTERNOON.

A FEW SHOWERS AND PERHAPS AN ISOLATED STORM MAY LINGER TONIGHT
INTO WEDNESDAY BUT DRY WX SHOULD PREVAIL THE MAJORITY OF THE
TIME. DRY WX IS FORECAST FOR WEDNESDAY NIGHT FOLLOWED BY A CHANCE
OF SHOWERS AND STORMS THURSDAY IN THE VICINITY OF A WARM FRONT AND
AS A WARMER AND MORE HUMID AIRMASS ADVANCES INTO OUR AREA.

.LONG TERM...(THURSDAY NIGHT THROUGH MONDAY)
ISSUED AT 325 AM EDT TUE AUG 19 2014

BEST CHANE FOR RAIN IN THE EXTENDED WILL BE ON THURSDAY NIGHT AND
FRIDAY AS ISENTROPIC ASCENT NORTH OF THE SFC WARM FRONT WILL FOCUS
SHOWERS AND THUNDERSTORMS. THESE WILL MOSTLY BE ACROSS THE SOUTHERN
FORECAST AREA THURSDAY NIGHT AND SPREAD NORTH ON FRIDAY.

UPPER RIDGING BUILDS IN BY SATURDAY WHICH WILL CAP SHOWER AND
THUNDERSTORMS EVEN THOUGH ISENTROPIC ASCENT PERSISTS AND INSTABILITY
IS PRESENT WITH LIFTED INDICES AROUND MINUS 6 SATURDAY AFTERNOON.
WENT WITH LOW CHANCE POPS. THE GFS BRINGS IN HEIGHT FALLS ON SUNDAY
WITH A MORE PROGRESSIVE  NORTHERN STREAM THAN THE ECMWF. WILL GO
WITH CHANCE POPS ON SUNDAY AS WELL...BUT A SLOWER SOLUTION LIKE THE
ECMWF IS ALSO POSSIBLE MEANING MONDAY COULD SEE HIGHER POPS THAN THE
GOING FORECAST.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z WEDNESDAY MORNING)
ISSUED AT 741 AM EDT TUE AUG 19 2014

LINE OF SHOWERS AND THUNDERSTORMS WILL MOVE THROUGH EARLY THIS
MORNING WITH BRIEF WIND GUSTS 20 TO 30 KNOTS AND AREAS OF MVFR AND
PATCHY IFR. THESE CONDITIONS WILL LAST AN HOUR OR LESS WITH
GENERALLY VFR BY LATER THIS MORNING.

WE WILL HAVE TO WATCH FOR MORE THUNDERSTORMS DEVELOPING ACROSS
SOUTHERN LOWER MICHIGAN BY 18Z AS INSTABILITY INCREASES. BEST
CHANCE FOR THIS WILL BE NEAR JXN...WHERE PATCHY IFR IS POSSIBLE IN
HEAVY DOWNPOURS FROM 17Z TO 21Z.


&&

.MARINE...
ISSUED AT 325 AM EDT TUE AUG 19 2014

SOUTHEAST WINDS WILL GRADUALLY VEER TO THE SOUTH TO SOUTHWEST AND
INCREASE LATER TODAY RESULTING IN WAVE HEIGHTS OF UP TO 2 TO 4
FEET NORTH OF HOLLAND. FAIRLY MINIMAL WIND AND WAVE ACTION IS
ANTICIPATED TONIGHT THROUGH MIDWEEK.


&&

.HYDROLOGY...
ISSUED AT 139 PM EDT MON AUG 18 2014

RIVERS ARE RUNNING A LITTLE ABOVE NORMAL... BUT ARE STILL FAR BELOW
BANK FULL. PRECIPITATION THIS EVENING THROUGH WEDNESDAY IS EXPECTED
TO TOTAL AROUND HALF AN INCH. THIS SHOULD LEAD TO SLOW RISES ON AREA
RIVERS WITH PEAK LEVELS WELL BELOW FLOOD STAGE OCCURRING BY THE END
OF THE WEEK. LOCALLY HEAVY RAINFALL IS POSSIBLE AND COULD LEAD TO
BRIEFLY HIGHER FLOWS.

LOOKING AHEAD...IT APPEARS TO BE A RATHER ACTIVE SECOND HALF OF
AUGUST WHICH MAY HELP BRING MANY RIVERS TO ABOVE NORMAL FLOWS.
WITH AN UPPER LEVEL RIDGE DEVELOPING TO THE SOUTH OF THE GREAT
LAKES OVER THE NEXT WEEK OR SO...IT WILL PLACE MICHIGAN IN AN
ACTIVE WEATHER PATTERN WITH NUMEROUS OPPORTUNITIES FOR RAIN.

&&

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

$$

MESOSCALE...MEADE
SYNOPSIS...LAURENS
SHORT TERM...LAURENS
LONG TERM...OSTUNO
AVIATION...OSTUNO
HYDROLOGY...63
MARINE...LAURENS






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