Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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188
FXUS63 KGRR 031820
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
120 PM EST WED FEB 3 2016

LATEST UPDATE...
AVIATION

.SYNOPSIS...
ISSUED AT 921 AM EST WED FEB 3 2016

LIGHT RAIN AND SNOW SHOWERS CAN BE EXPECTED TODAY AS LOW PRESSURE
MOVES AWAY. SNOW SHOWERS AND COLDER WEATHER WILL RETURN FOR
TONIGHT AND PERSIST INTO THE WEEKEND.

&&

.UPDATE...
ISSUED AT 921 AM EST WED FEB 3 2016

DROPPED THE DENSE FOG ADVISORY AS VISIBILITIES ARE IMPROVING AS
WINDS PICK UP WITH A TIGHTENING PRESSURE GRADIENT ON THE BACK SIDE
OF THE LOW. COLDER AIR WRAPPING AROUND WILL BRING A CHANGEOVER TO
SNOW THIS AFTERNOON...AS CURRENTLY SEEN ACROSS WISCONSIN. RADAR
AND MODEL TRENDS INDICATE THAT THE BULK OF THE DEFORMATION ZONE
PRECIPITATION WILL MOVE ACROSS THE NORTHWEST THIRD OF THE FORECAST
AREA THIS AFTERNOON.

&&

.SHORT TERM...(TODAY THROUGH FRIDAY)
ISSUED AT 330 AM EST WED FEB 3 2016

WE WILL BE ISSUING A DENSE FOG ADVISORY WITH THE FCST PACKAGE THIS
MORNING. DENSE FOG HAS BECOME WIDESPREAD TO OUR SOUTH AND WEST
ALREADY THIS MORNING...AND IT IS POISED TO EXPAND INTO THE AREA
PRIOR TO DAYBREAK. A VERY MOIST LOW LEVEL ATMOSPHERE COMBINED WITH A
LULL IN THE WIND AND NO CLOUDS ABOVE THE BOUNDARY LAYER ALL POINT
TOWARD FOG DEVELOPMENT. SHORT TERM HI RES MODELS ALL SUPPORT THIS
IDEA WELL.

THE FOG WILL DISSIPATE THEN LATER THIS MORNING...JUST AS THE WINDS
PICK UP WITH THE ARRIVAL OF THE UPPER LOW/TROUGH. THE ARRIVAL WILL
ALSO START BRINGING PCPN BACK INTO THE CWFA FROM THE WEST...WITH
THE MAIN FOCUS ACROSS THE NW COUNTIES CLOSER TO THE TRACK OF THE
UPPER LEVEL TROUGH. PCPN WILL START OUT BRIEFLY AS RAIN...AND THEN
TRANSITION TO SNOW AS THE COLDER AIR WORKS BACK INTO THE AREA FROM
THE WEST. WE ARE LOOKING AT AN INCH OR SO OF SNOW ACROSS THE NW
WITH LESSER AMOUNTS TO THE SE.

SOME LAKE EFFECT SNOW SHOWERS WILL THEN DEVELOP LATE THIS AFTERNOON
AND CONTINUE THROUGH THE FIRST PART OF THU. OVERLAKE INSTABILITY
WILL INCREASE ENOUGH BY LATE WED AFTERNOON AS H850 TEMPS DROP TO
BELOW -10C. THERE IS SOME DECENT MOISTURE DEPTH LINGERING
AROUND...HOWEVER INVERSION HEIGHTS ARE RATHER LOW AROUND 5K FT WITH
THE COLD AIR MASS NOT BEING ESPECIALLY DEEP. SHORT WAVES ARE NOT
LOOKING TO MOVE DIRECTLY THROUGH THE AREA. WE WILL SEE SOME
LIGHTER ACCUMS...WITH THE FAVORED AREAS BEING THOSE IN A NW FLOW.

SNOW SHOWERS SHOULD DIMINISH TO LITTLE IF NOT NOTHING THU AFTERNOON
AND THU EVENING. WE WILL SEE SFC RIDGING MOVE THROUGH...HELPING TO
SQUASH THE CONVECTIVE DEPTH OF THE LAKE EFFECT. WE WILL SEE SNOW
SHOWERS PICK UP A BIT THU NIGHT FOR SW FLOW FAVORED AREAS AS
MOISTURE DEPTH INCREASES AHEAD OF A WEAKENING COLD FRONT SWINGING
INTO THE AREA. THE UPPER FLOW WILL BECOME MORE ANTI-CYCLONIC BY FRI
MORNING...PRODUCING A MORE HOSTILE ENVIRONMENT FOR LAKE EFFECT.

.LONG TERM...(FRIDAY NIGHT THROUGH TUESDAY)
ISSUED AT 330 AM EST WED FEB 3 2016

THERE IS SOME POTENTIAL FOR A MORE WINTRY WEATHER PATTERN AS WE
HEAD INTO SECOND WEEK OF FEBRUARY.

THE PROBLEM IS WE HAVE CONFLICTING SIGNALS. OUR STRONG EL NINO IS
HELPING THE MJO CONVECTIVE WAVE STRENGTHEN QUAD 4 DURING THE NEXT
FEW DAYS. THAT POSITION OF THE MJO CONVECTION WOULD NORMALLY BE A
VERY WARM WEATHER PATTERN FOR SOUTHWEST MICHIGAN FOR AT LEAST A
WEEK. ALSO GOING ALONG WITH THAT IDEA WE ALSO HAVE ANOTHER ONE OF
THOSE EXTEND EAST ASIAN JETS NEAR 200 KNOTS HEADING FOR THE
INTERNATIONAL DATELINE. TYPICALLY THAT JET CORE HEADS EAST INTO WEST
COST OF THE CONUS SETTING UP A TROUGH OVER THE WESTERN UNITED
STATES. ALL OF THIS WOULD MEAN RIDGING AT UPPER LEVELS OVER THE
GREAT LAKES OVER THE NEXT WEEK. HOWEVER... THE MODELS SHOW
OTHERWISE. IT SEEMS THAT JET STREAK HELPS TO KEEP A RATHER DEEP
STORM SYSTEM IN THE GULF OF ALASKA AS A SERIES OF STORMS SEEM TO
MERGE INTO THE STORM SYSTEM ALREADY THERE. THAT RESULTS IN A LARGE
WESTERN RIDGE WHICH HELPS TO FORCE A SERIES OF NORTHERN STREAM SHORT
WAVE DIG OUT A DEEP EASTERN TROUGH DURING THE FIRST HALF OF NEXT
WEEK. THIS WOULD BRING DOWN...BY FAR THE COLDEST AIR OF THE SEASON
IF IT ALL PLAYS OUT THIS WAY.

THE IMPACT ON WEST MICHIGAN WEATHER WOULD BE A WEAK SYSTEM MOVING
NORTH OF THE AREA SATURDAY CAUSING NOT MUCH MORE THERE THAN CLOUDS
AND MAYBE A FEW FLURRIES. BY MONDAY THE DIGGING NORTHERN STREAM
WOULD SEND A CLIPPER SYSTEM SHARPLY SOUTH SOUTHEAST INTO THE WESTERN
GREAT LAKES. THIS WOULD BRING SNOW SHOWERS MONDAY INTO TUESDAY. THE
REALLY COLD AIR WOULD NOT GET HERE TILL WEDNESDAY. IF THIS ALL
PLAYS OUT A GOOD PART OF NEXT WEEK COULD BE RATHER SNOWY FOR THE
LAKE SHORE AREAS. EASTERN SECTIONS WOULD SEE SNOW BUT ONLY SMALL
AMOUNTS.

WE WILL HAVE TO WATCH TO SEE HOW THIS PLAYS OUT... THE MJO
CONVECTIVE WAVE MAY YET TRUMP THIS (FORCING THE STORM NOT TO DIG SO
FAR SOUTH EARLY NEXT WEEK).  THE NEXT SEVERAL MODEL RUNS WILL HELP
SEE HOW THIS WILL PLAY OUT.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z THURSDAY AFTERNOON)
ISSUED AT 118 PM EST WED FEB 3 2016

COLDER AIR IS NOW FLOWING BACK OVER THE LAKE AND WE SHOULD SEE
SHSN DEVELOP THROUGH TONIGHT. MVFR EXPECTED THROUGH MUCH OF
THE PERIOD. HOWEVER...SOME IFR IS POSSIBLE AROUND 10Z WHEN THE
SHSN SHOULD BE HEAVIEST.

&&

.MARINE...
ISSUED AT 330 AM EST WED FEB 3 2016

WE HAVE STRETCHED THE SMALL CRAFT ADVISORY THROUGH THURSDAY MORNING.
WE ARE IN A LULL WITH REGARD TO WINDS CURRENTLY WITH THE LOW NEARBY
AND A WEAK GRADIENT IN PLACE. WE WILL SEE SW WINDS INCREASE UP TO
AROUND 30 KNOTS ONCE AGAIN ON THE BACKSIDE OF THE LOW AS IT MOVES
OUT OF THE AREA. WINDS WILL DIMINISH LATE TONIGHT...WITH WAVES
COMING DOWN TOWARD DAYBREAK ON THURSDAY.


&&

.HYDROLOGY...
ISSUED AT 235 PM EST TUE FEB 2 2016

MINOR FLOODING IS POSSIBLE LATER THIS WEEK... ESPECIALLY IN
LOWLAND AREAS NEAR RIVERS. SOME RIVERS MAY EXCEED BANKFULL DUE TO
SNOW MELT AND PRECIPITATION FROM A STORM TODAY AND TONIGHT. STORM
TOTAL PRECIPITATION OF 0.50-1.00 INCHES IS POSSIBLE. PRECIPITATION
IS STILL EXPECTED TO BE A WINTRY MIX OR PLAIN RAIN. RIVER LEVEL
RISES ARE ESPECIALLY LIKELY FROM MIDWEEK THROUGH THE WEEKEND. RIVER
FLOOD ADVISORIES HAVE BEEN ISSUED FOR SYCAMORE CREEK AT HOLT...
MAPLE RIVER AT MAPLE RAPIDS AND GRAND RIVER AT IONIA.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LM...SMALL CRAFT ADVISORY UNTIL 4 AM EST THURSDAY FOR LMZ844>849.

&&

$$

UPDATE...OSTUNO
SYNOPSIS...OSTUNO
SHORT TERM...NJJ
LONG TERM...WDM
AVIATION...04
HYDROLOGY...63
MARINE...NJJ



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