Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 240729
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
329 AM EDT SUN MAY 24 2015

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

.SYNOPSIS...
ISSUED AT 315 AM EDT SUN MAY 24 2015

A WARM FRONT WILL LIFT NORTHWARD THROUGH LOWER MICHIGAN TODAY AND
TONIGHT. SHOWERS WILL BE ON THE INCREASE AS THIS SYSTEM TRACKS
THROUGH AND THERE COULD EVEN BE A FEW STORMS ESPECIALLY TONIGHT.
MEMORIAL DAY IS LOOKING WARM AND WINDY WITH SOME SHOWERS AND
STORMS AROUND...MAINLY EARLY. UNSETTLED WEATHER WILL CONTINUE
THROUGH TUESDAY AS THE FRONT REMAINS SITUATED IN MICHIGAN.

&&

.SHORT TERM...(TODAY THROUGH TUESDAY)
ISSUED AT 315 AM EDT SUN MAY 24 2015

THE MAIN CHALLENGE DEALS WITH THE COVERAGE AND AMOUNT OF SHOWERS
AND THUNDERSTORMS THROUGH THE PERIOD.

TO START...I BACKED OFF ON THE POPS MAINLY TODAY AND LATER
MEMORIAL DAY. THE LATEST MODEL DATA AND RADAR TRENDS SHOW WHAT
UPSTREAM SHOWER ACTIVITY WILL LIKELY WEAKEN AS IT MOVES INTO LOWER
MICHIGAN LATER THIS MORNING INTO THIS AFTERNOON. SO POPS WERE
LOWERED TODAY. AFTER 22Z SOME INSTABILITY TRIES TO MOVE INTO THE
SOUTH HAVEN REGION...SO I DID MAINTAIN A LOW RISK FOR THUNDER
THEN.

ON MEMORIAL DAY MOST MODELS ARE SHOWING A SHORTWAVE TRACKING
THROUGH BY EARLY AFTERNOON. IF THIS HAPPENS WE WILL SEE MORNING
SHOWERS AND STORMS FOLLOWED BY A CONSIDERABLE DECREASE IN THE
ACTIVITY FOR THE AFTERNOON. I DID LOWER POPS FOR WESTERN LOCATIONS
FOR THE AFTERNOON BASED ON THIS MODEL TREND. IT WILL LIKELY END UP
WINDY DURING THE AFTERNOON AS A LOW LEVEL JET COMBINES WITH BETTER
MIXING TO SUPPORT STRONGER GUSTS.


.LONG TERM...(TUESDAY NIGHT THROUGH SATURDAY)
ISSUED AT 315 AM EDT SUN MAY 24 2015

TWO MAIN OPPORTUNITIES FOR RAINFALL WILL BE CENTERED ON TUESDAY
NIGHT AND THEN AGAIN FOR FRIDAY AND SATURDAY. OUTSIDE OF THESE
PERIODS...LITTLE RAINFALL IS EXPECTED WITH PREDOMINANTLY DRY WEATHER
LIKELY.

CURRENT WV ANALYSIS WITH RAP40 H850-H300 MEAN HEIGHTS OVERLAID
REVEALS A WELL DEFINED UPPER LEVEL SHORTWAVE ACROSS SOUTHERN
CALIFORNIA...WHICH IS THE FEATURE OF INTEREST FOR TUESDAY NIGHT.
THIS IMPULSE IS FORECAST TO PHASE WITH DEEPER UPPER LEVEL TROUGHING
ACROSS THE NORTHERN PLAINS...WHICH WILL BE IN THE PROCESS OF
WEAKENING. THE GFS IS SLOWEST WITH THIS PHASING COMPARED WITH THE
ECMWF AND GEM...AND HENCE LINGERS PRECIPITATION FURTHER INTO
WEDNESDAY MORNING. ALL THE MODELS DO BRING SOME PRECIP INTO SW LOWER
MI HOWEVER...SO A WIDE AREA OF LIKELY POPS IS BEING CARRIED. SOME
INSTABILITY IS PRESENT VIA BUFKIT SOUNDINGS...SO THUNDERSTORMS WILL
BE POSSIBLE THOUGH SHOWERS MAY BE MORE THE GENERAL RULE.

WEDNESDAY WILL LARGELY BE DRY OUTSIDE OF A FEW SCATTERED SHOWERS OR
STORMS...MAINLY DUE TO A WEAK FRONTAL BOUNDARY SLATED TO MOVE
THROUGH BETWEEN 12Z AND 18Z. ONCE THAT PASSES...THINGS SHOULD DRY
OUT. THURSDAY LOOKS WARM AND PLEASANT WITH DRY CONDITIONS OUTSIDE OF
VERY ISOLATED SHOWERS OR T-STORMS TOWARD EXTREME SOUTHERN MI.

FOR FRIDAY AND SATURDAY...A BAROCLINIC ZONE LOOKS TO SET UP ACROSS
THE MIDWEST WITH MOIST SOUTHERLY FLOW AHEAD OF IT. THE GFS AND ECMWF
HAVE A RATHER LARGE AMOUNT OF SFC BASED CAPE INDICATED FOR FRIDAY
ACROSS OUR REGION (2000+ J/KG)...AND WITH AN INCREASINGLY HUMID
AIRMASS WITH PWATS OF 1.5-1.75" THERE COULD BE A FAIR AMOUNT OF
THUNDERSTORMS PRESENT WITH EITHER THE GFS OR ECMWF SOLUTIONS
VERIFYING. SOME HEAVIER RAINFALL WOULD CERTAINLY BE A POSSIBILITY AS
WELL.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SUNDAY NIGHT)
ISSUED AT 121 AM EDT SUN MAY 24 2015

QUIET CONDITIONS THROUGH AT LEAST THE LATE MORNING PERIOD BEFORE
MID LEVEL CLOUDS THICKEN UP AND A FEW SHOWERS DEVELOP DURING THE
AFTERNOON PERIOD. COVERAGE CURRENTLY LOOKS LOW DURING THE EARLY
AFTERNOON HOURS WITH STEADIER PRECIP DEVELOPING FOR MKG AND GRR
CLOSER TO 00Z. LOCATIONS LIKE AZO...BTL...AND JXN MAY ESCAPE THIS
TAF PERIOD WITH LITTLE TO NO RAINFALL IT APPEARS BASED ON 00Z
MODEL GUIDANCE. REGARDLESS...MVFR CONDITIONS WILL BE PREDOMINANT.


&&

.MARINE...
ISSUED AT 315 AM EDT SUN MAY 24 2015

WE WILL LIKELY NEED SMALL CRAFT ADVISORIES MEMORIAL DAY. A
STRONGER PRESSURE GRADIENT SETS UP AND THE FETCH IS FAVORABLE FOR
BIGGER WAVES DESPITE THE STABLE LAKE CONDITIONS. ANY SWIMMING WILL
LIKELY BE HAZARDOUS AS WELL.

FOG WILL LIKELY INCREASE AS WELL AS GULF MOISTURE ADVECTS OVER THE
RELATIVELY COLD LAKE MI WATERS.

&&

.HYDROLOGY...
ISSUED AT 315 AM EDT SUN MAY 24 2015

WITH SEVERAL ROUNDS OF STORMS LIKELY THROUGH TUESDAY...RAINFALL
COULD END UP BEING HEAVY IN PLACES. HOW MUCH IF ANY FLOODING WILL
LIKELY BE DETERMINED IF THE STORMS REPEAT OVER THE SAME REGION. AT
THIS POINT NOT ENOUGH CONFIDENCE THERE TO GO VERY HIGH WITH THE
FLOOD RISK. HOWEVER WITH THE GULF OPENING UP AND SEVERAL LOW LEVEL
JETS HEADED OUR WAY...SOME RISK EXISTS.

&&

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

$$

SYNOPSIS...MJS
SHORT TERM...MJS
LONG TERM...HOVING
AVIATION...HOVING
HYDROLOGY...MJS
MARINE...MJS



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