Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 240429
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
1129 PM EST MON FEB 23 2015

LATEST UPDATE...
AVIATION

.SYNOPSIS...
ISSUED AT 239 PM EST MON FEB 23 2015

A FAST MOVING LOW PRESSURE SYSTEM WILL TRACK EASTWARD THROUGH
ONTARIO TONIGHT AND TUESDAY. THIS SYSTEM WILL PROVIDE THE GREAT
LAKES REGION WITH WINDY CONDITIONS AND SOME SNOW. CONSIDERABLE
DRIFTING SNOW WILL BE POSSIBLE ON TUESDAY. ANOTHER ARCTIC AIRMASS
WILL TRACK IN BEHIND THIS DEPARTING STORM AND PERSIST INTO THE
WEEKEND.

&&

.UPDATE...
ISSUED AT 902 PM EST MON FEB 23 2015

NO HEADLINE OR SIGNIFICANT FCST CHANGES ARE NECESSARY TONIGHT. A
CONSENSUS OF LATEST SHORT RANGE GUIDANCE STILL SUGGESTS THAT SNOW
AMOUNTS WITH THE SYSTEM TUESDAY WILL BE FAIRLY LIGHT OVERALL WITH
THE RELATIVELY HIGHEST AMOUNTS OF UP TO 3 TO 5 INCHES NEAR TO NW
OF A LINE FROM KMKG TO KRQB. MOST OF OUR AREA WILL ONLY GET AN
INCH OR TWO OF SNOW WITH THIS SYSTEM. HOWEVER THE COMBINATION OF
STRONG WINDS AND THE SNOW WILL RESULT IN SOME HAZARDOUS TRAVEL
CONDITIONS FROM MID TO LATE MORNING THROUGH TUESDAY EVENING.

&&

.SHORT TERM...(THIS EVENING THROUGH WEDNESDAY NIGHT)
ISSUED AT 239 PM EST MON FEB 23 2015

THE MAIN ISSUE DEALS WITH THE IMPACT OF THE LOW PRESSURE SYSTEM
THAT TRACKS THROUGH ONTARIO TONIGHT AND TUESDAY. OVERALL IT LOOKS
LIKE ENOUGH IMPACTS TO WARRANT HEADLINES FOR THE ENTIRE REGION.

I DID CHECK IN WITH A COUPLE OF ROAD COMMISSIONS AND THEY
INDICATED THAT WINDS OVER 30 MPH WILL LEAD TO CONSIDERABLE
DRIFTING OF THE SNOW...ESPECIALLY IN RURAL AREAS. EVEN SOME
HIGHWAYS COULD BE IMPACTED. THE RUC MODEL SHOWS GUSTS TOPPING 40
KNOTS FROM NEAR GRAND RAPIDS NORTHEAST THROUGH MOUNT PLEASANT AND
BETTER THAN 35 KNOTS ELSEWHERE. THERE IS A SECONDARY MAX ALONG THE
LAKESHORE NORTH OF MUSKEGON...WITH BETTER THAN 40 KNOTS POSSIBLE.
I AM NOT CERTAIN WILL SEE SUCH HIGH WINDS. HOWEVER ENOUGH RISK
THERE TO GO WITH A HEADLINE. THE MAIN WINDOW OF STRONG WINDS
RANGES FROM 09Z TO 18Z FOR LUDINGTON...13Z TO 21Z FOR GRAND RAPIDS
AND 16Z TO 23Z FOR JACKSON.

SNOW ON TUESDAY WILL BE A SECONDARY CONCERN FOR THIS SYSTEM WITH AMOUNTS
EXPECTED TO RANGE FROM 2 TO 4 INCHES OF LAKE ENHANCED SNOW UP
NORTH FROM LUDINGTON TO HARRISON. FURTHER SOUTH GRAND RAPIDS AND
MOUNT PLEASANT ROUGHLY 1 TO 3 INCHES...TO AN INCH OR LESS FOR
JACKSON AND LANSING. STILL...WITH GUSTY WINDS AND SNOW...
VISIBILITIES COULD BE REDUCED CONSIDERABLY AT TIMES. LOCATIONS
SOUTHEAST OF GRAND RAPIDS COULD START THE DAY OFF WITH SOME SUN.

WIND CHILL VALUES ON TUESDAY COULD START OFF AROUND -15 DEGREES...
WHICH IS HAZARDOUS.

TUESDAY NIGHT AFTER A LULL IN THE WIND...WE COULD SEE A RETURN OF
SNOW AND POSSIBLE IMPACTS...MAINLY AFTER MIDNIGHT. WILL NEED TO
ASSESS THIS POSSIBILITY WITH LATER FORECASTS.

.LONG TERM...(THURSDAY THROUGH MONDAY)
ISSUED AT 239 PM EST MON FEB 23 2015

THE FOCUS OF THE LONG TERM IS THE EVOLUTION OF A SOUTHERN STREAM
SYSTEM THAT BOTH THE GFS AND ECMWF HAVE LATCHED ONTO FOR A COUPLE OF
DAYS NOW. CONDITIONS LOOK PRETTY DRY...BUT COLD FROM THURSDAY
THROUGH SATURDAY...AND LIKELY MONDAY TOO. HOWEVER IT`S THE PERIOD
FROM SATURDAY NIGHT THROUGH SUNDAY NIGHT THAT PROMISES TO BE
INTERESTING.

IT/S LOOKING INCREASINGLY LIKELY THAT PCPN WILL DEVELOP OVER THE SW
CWA SATURDAY EVENING...LIKELY AS SNOW...AND CONTINUE THROUGH SUNDAY.
THE GULF IS WIDE OPEN DUE TO HIGH PRESSURE NEAR THE EAST COAST AND
SO THERE WILL BE A STRONG INFLUX OF MOISTURE. DESPITE THE MOISTURE
CONTENT OF THIS SYSTEM...IT STILL HAS SOME ISSUES. ECMWF AND GFS
BOTH SHOW THIS BEGINNING AS AN INVERTED TROUGH AND THEN PHASING WITH
A NORTHERN STREAM CLIPPER AS IT PUSHES A COLD FRONT THROUGH THE CWA.
THIS ISN/T THE CLASSIC STRENGTHENING CLOSED LOW THAT MOVES FROM THE
SOUTHERN PLAINS NEWD. AT LEAST NOT YET. QPF WITH THE SYSTEM IS PROGD
IN THE 2/3 TO 3/4 INCH RANGE...WHICH IF ALL SNOW WOULD CERTAINLY BE
PLOWABLE. THE WARMER ECMWF WOULD LIKELY TURN PCPN TO MIXED RAIN AND
SNOW ACROSS THE SOUTHERN CWA. FOR CONTINUITY SAKE WE KEPT THE PCPN
AS SNOW IN THE GRIDS FOR NOW.

ALL OF THE PCPN WILL LIKELY END MONDAY AS THE SYSTEM MOVES EAST AND
ANOTHER SHOT OF COLD AIR MOVES SOUTH.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z TUESDAY NIGHT)
ISSUED AT 1122 PM EST MON FEB 23 2015

THE MAIN AVIATION ISSUE OVER THE NEXT 24 HOURS IS THE WINDS.
SOUTHWEST WINDS WILL INCREASE OVERNIGHT TO 15 TO 25 KNOTS AND
AFTER DAYBREAK TO 20 TO 30 KNOTS WITH SOME GUSTS AS HIGH AS 40
KNOTS. THE HIGHEST WINDS APPEAR TO OCCUR BETWEEN 12Z AND 18Z.

THE STRONG WINDS WILL RESULT IN AREAS OF BLOWING SNOW DEVELOPING
BEFORE THE SNOW MOVES IN WHICH COULD LEAD TO REDUCE VSBYS AND
SLICK RUNWAY CONDITIONS FOR THE MORNING RUSH.

THE FALLING SNOW WILL SPREAD INTO THE REGION FROM NORTHWEST TO
SOUTHEAST... REACHING MKG AROUND 15Z AND LAN/JXN AROUND 19Z. THE
HEAVIEST SNOW AND LOWEST VSBYS WILL BE AT MKG AND GRR SO WILL KEEP
PREDOMINATELY IFR VSBYS TUESDAY AFTERNOON AT THESE TWO SITES AND
MOSTLY MVFR VSBYS AT THE OTHER TERMINALS. THERE IS A POTENTIAL
HOWEVER FOR IFR TO DEVELOP AT ALL THE TERMINALS DEPENDING ON THE
EXTENT OF THE BLOWING SNOW.

WINDS DIMINISHING AFTER 00Z WED BUT STILL 10 TO 20 KTS... AND
CIGS/VSBYS REMAINING PREDOMINATELY MVFR. CANT RULE OUT SOME IFR
VSBYS IN SNOW SHOWERS PERSISTING BEYOND 00Z WED BUT WAS NOT
CONFIDENT ENOUGH TO HAVE IN THE TAFS.


&&

.HYDROLOGY...
ISSUED AT 239 PM EST MON FEB 23 2015

WITH NO MAJOR WARM UPS OR RAINFALL HEADED OUR WAY IN THE NEAR
FUTURE...RUNOFF WILL BE LIMITED. SERIOUS ICE JAMS AND FLOODING
CONCERNS ARE UNLIKELY UNTIL A SIGNIFICANT WARM UP AND RAINFALL
OCCUR.  CONSIDERABLE ICE DOES EXIST IN THE RIVERS SO WE WILL NEED
TO MONITOR TRENDS CLOSELY. FOR NOW WITH CONDITIONS STABLE DUE TO
THE ARCTIC AIRMASS IN PLACE...THE RISK IS SOMEWHAT LIMITED FOR
FLOODING.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...WINTER WEATHER ADVISORY FROM 4 AM TO 7 PM EST TUESDAY FOR
     MIZ037>040-043>046-050>052-056>059-064>067-071>074.

LM...NONE.
&&

$$

UPDATE...LAURENS
SYNOPSIS...MJS
SHORT TERM...MJS
LONG TERM...04
AVIATION...MEADE
HYDROLOGY...MJS





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