Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 291930
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
330 PM EDT SUN MAR 29 2015

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

.SYNOPSIS...
ISSUED AT 330 PM EDT SUN MAR 29 2015

A COLD FRONT SWINGING THROUGH THE GREAT LAKES REGION WILL BRING A
MIX OF RAIN...SNOW AND EVEN A BIT OF SLEET BEFORE ENDING OVERNIGHT.
ANY SNOW ACCUMULATION IS EXPECTED TO BE MINOR. A CLIPPER SYSTEM
DIVING THROUGH THE AREA WILL BRING ANOTHER CHANCE OF RAIN AND SNOW
MONDAY NIGHT INTO TUESDAY MORNING. A WARM UP WILL OCCUR INTO MID
WEEK AHEAD OF OUR NEXT SYSTEM THAT WILL BRING RAIN WEDNESDAY NIGHT
INTO THURSDAY.

&&

.SHORT TERM...(THIS EVENING THROUGH TUESDAY NIGHT)
ISSUED AT 330 PM EDT SUN MAR 29 2015

MAIN ISSUES IN THE SHORT TERM ARE WITH THE ONGOING PRECIPITATION
EVENT AND THE NEXT ONE SET TO MOVE THROUGH MONDAY NIGHT INTO
TUESDAY.

THE ONGOING EVENT HAS CAME IN WITH A MIXTURE OF SNOW AND
SLEET...WHICH IS GRADUALLY TRYING TO CHANGE OVER TO RAIN. THE
MIXTURE OF PRECIP WILL CONTINUE AS IT WORKS EAST ACROSS THE FORECAST
AREA. THE DRY AIR IN PLACE HAS RESULTED IN COOLING OF THE PROFILE.
EXPECT THE PRECIP TO GO OVER TO MAINLY RAIN THIS EVENING AS MORE
MOIST AIR IS PULLED IN. A SECOND BATCH OF PRECIP WILL PIVOT THROUGH
THE AREA BEFORE MIDNIGHT ASSOCIATED WITH A SECOND SHORTWAVE. RAIN
AND RAIN MIXED WITH SNOW SHOULD BE THE PRIMARY P-TYPES.

AS FOR OUR MONDAY NIGHT AND TUESDAY EVENT...THE SHORTWAVE IS JUST
COMING ASHORE IN BRITISH COLUMBIA. THE MODELS HAVE STRUGGLED WITH
THE EXACT TRACK THAT IT TAKES ACROSS OUR AREA. THE ECMWF IS FURTHER
SOUTH AND WOULD PUT THE BETTER PRECIPITATION AXIS THROUGH OUR CWA.
AT THIS POINT HAVE LIKELY POPS IN MONDAY NIGHT FOR RAIN AND SNOW.
LATER FORECAST WILL BETTER DEFINE THE DETAILS AS THE TRACK ZEROS IN.

.LONG TERM...(WEDNESDAY THROUGH SUNDAY)
ISSUED AT 330 PM EDT SUN MAR 29 2015

OUR MAIN CHALLENGE IN THE LONG TERM IS DEALING WITH THE SYSTEM IN
THE WED NIGHT THROUGH THU NIGHT TIME FRAME. THE TIMING OF THE SYSTEM
WILL DETERMINE WHEN THE BEST CHC OF PCPN WILL BE...AND IF WE CAN
SNEAK IN A WARM DAY IN ON THU BEFORE THE FRONT MOVES THROUGH.

THE AREA WILL START OUT WITH A DRY AND MILD DAY ON WED. SFC RIDGING
WILL BE PASSING EAST OF THE AREA...AND THE UPPER RIDGE WILL BE
MOVING OVERHEAD. H850 TEMPS OF 4 TO 8C WILL BE ADVECTING IN DURING
THE DAY.

THE UNCERTAIN PORTION OF THE FCST THEN COMES FOR THE WED NIGHT
THROUGH THU NIGHT WHEN A COLD FRONT WILL COME THROUGH AT SOME POINT.
FASTER SOLUTIONS LIKE THE GFS RESULT FROM A NRN STREAM TROUGH
DOMINATING WITH A MORE FLAT AND FASTER FLOW ALOFT. SLOWER SOLUTIONS
LIKE THE ECMWF HAVE PHASING BETWEEN THE NRN STREAM SYSTEM AND A SRN
STREAM SYSTEM DIGGING ACROSS THE ROCKIES WITH A MORE AMPLIFIED FLOW.
THE FRONT WOULD COME THROUGH THU AFTERNOON/EVENING WITH THE SLOWER
SOLUTION.

WE HAVE FOCUSED THE PCPN CHCS ON THU AS THIS SEEMS TO BE THE CORE OF
THE PCPN POTENTIAL. IT COULD BE EARLY OR LATE...BUT THU LOOKS LIKE
THE BEST BET. WE HAVE ALSO ALLOWED FOR TEMPS WELL INTO THE 60S AS A
MIDDLE OF THE ROAD APPROACH. IF THE EURO IS CORRECT WITH A LATER
TIMING...70 STILL SEEMS POSSIBLE.

WE EXPECT THAT THE FRONT AND PCPN WILL NOW CLEAR THE AREA THU
NIGHT...AND ALLOW FOR A DRY AND COOL DAY ON FRI. THE NEXT SHORT WAVE
DIVING IN FROM THE NW WILL THEN COME IN ON SAT. THIS WILL BRING A
CHC OF PCPN...WHICH COULD BE RAIN OR SNOW DEPENDING ON THE TIME OF
THE DAY DUE TO WARMING. A WARM FRONT WILL MOVE BACK NORTH ON SUN
BRINGING A SMALL CHC OF PCPN AND WARMER TEMPS BACK.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z MONDAY AFTERNOON)
ISSUED AT 144 PM EDT SUN MAR 29 2015

THE MAIN PERIOD OF CONCERN WITH THE 18Z FCSTS WILL BE THE FIRST 12
HOURS OR SO WITH LOWER CONDITIONS WITH PCPN EXPECTED. THE LEADING
EDGE OF THE INITIAL BAND OF PCPN HAS REACHED KMKG AS OF 1740Z.
THIS STARTED AS RAIN AND SLEET/PL AT KMKE AND WE EXPECT THE SAME
HERE. GENERALLY MVFR CONDITIONS ARE EXPECTED.

WE EXPECT THAT SOME SNOW MAY MIX IN AT KMKG AND KGRR FOR AN HOUR
OR TWO AS THE AIR COOLS OFF WHILE MOISTENING UP. FURTHER SOUTH A
SUFFICIENT WARM LAYER AT THE SFC SHOULD KEEP MOST PCPN RAIN. PCPN
MAY DIMINISH TO DRIZZLE BEHIND THE FIRST BAND...AND AHEAD OF A
SECONDARY BAND THAT WILL COME THROUGH. THE SECONDARY BAND SHOULD
BE ALL RAIN FOR ALL OF THE TERMINALS.

PCPN SHOULD END LATE IN THE EVENING OR VERY EARLY IN THE OVERNIGHT
PERIOD. MVFR CLOUDS WILL LINGER INTO THE OVERNIGHT HOURS BEFORE
SKIES SHOULD CLEAR.

WIND GUSTS WILL REMAIN UP INTO THE 30 KNOT RANGE INTO 02-04Z. WIND
GUSTS WILL DIMINISH A LITTLE...WITH GUSTS AROUND 20-25 KNOTS
EXPECTED THROUGH THE END OF THE FCST PERIOD.

&&

.MARINE...
ISSUED AT 741 AM EDT SUN MAR 29 2015

NEARSHORE MARINE FORECASTS BETWEEN ST. JOSEPH AND MANISTEE WILL
BEGIN TOMORROW...MONDAY MARCH 30TH. THE MARINE SECTION OF THE AREA
FORECAST DISCUSSION WILL START UP THEN AS WELL.

&&

.HYDROLOGY...
ISSUED AT 330 PM EDT SUN MAR 29 2015

RIVERS REMAIN BELOW BANKFULL AND ARE HOLDING STEADY OR SLOWLY
FALLING. PRECIPITATION AMOUNTING UP TO SEVERAL TENTHS OF AN
INCH OVER THE NEXT SEVERAL DAYS IS NOT EXPECTED TO CAUSE A
SIGNIFICANT RISE IN RIVER LEVELS.

&&

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

$$

SYNOPSIS...DUKE
SHORT TERM...DUKE
LONG TERM...NJJ
AVIATION...NJJ
HYDROLOGY...CAS
MARINE...99






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