Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 051203
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
703 AM EST FRI FEB 5 2016

LATEST UPDATE...
AVIATION

.SYNOPSIS...
ISSUED AT 326 AM EST FRI FEB 5 2016

A FEW LIGHT SNOW SHOWERS AND FLURRIES WILL LINGER TODAY AND AGAIN
FOR SATURDAY. A CLIPPER SYSTEM WILL BRING MIXED RAIN AND SNOW
SHOWERS SUNDAY FOLLOWED BY SNOW SHOWERS SUNDAY NIGHT THROUGH EARLY
TO MID NEXT WEEK. TEMPERATURES WILL AVERAGE ABOVE NORMAL THIS
WEEKEND AND MONDAY BEFORE COOLING TO BELOW NORMAL BY MID TO LATE
WEEK.

&&

.SHORT TERM...(TODAY THROUGH SUNDAY)
ISSUED AT 326 AM EST FRI FEB 5 2016

A SFC TROF WILL BRING POTENTIAL FOR A FEW MORE LIGHT SNOW SHOWERS
AND FLURRIES THIS MORNING. AFTER PASSAGE OF THE SFC TROF BY MIDDAY
A FEW MORE LIGHT SNOW SHOWERS AND FLURRIES WILL DEVELOP AS
THETA E DECREASES WITH HEIGHT RESULTING IN A LITTLE BIT OF
INSTABILITY. HOWEVER VERY LITTLE (UNDER AN INCH) TO NO SNOW
ACCUMULATION IS ANTICIPATED TODAY.

FAIR WX IS ANTICIPATED THIS EVENING FOLLOWED BY DEVELOPMENT OF A
FEW MORE LIGHT SNOW SHOWERS AND FLURRIES OVER OUR FAR NW FCST AREA
TOWARD DAYBREAK SATURDAY AS THE NEXT LOW PRESSURE SYSTEM CONTINUES
TO MOVE EAST ACROSS THE LAKE SUPERIOR REGION. THIS SYSTEM WILL
BRING POTENTIAL FOR A FEW LIGHT SNOW SHOWERS AND FLURRIES SATURDAY
MORNING AND AFTERNOON BUT ONCE AGAIN WITH VERY LITTLE TO NO SNOW
ACCUMULATION.

DRY WX RETURNS SATURDAY NIGHT BEFORE A CLIPPER SYSTEM BRINGS
POTENTIAL FOR A MIX OF RAIN AND SNOW SHOWERS SUNDAY AS THERMAL
PROFILES MODERATE IN SW FLOW WAA IN ADVANCE OF THE CLIPPER. HIGH
TEMPS SUNDAY WILL REACH THE UPPER 30S UP NORTH TO THE LOWER 40S
SOUTH.

.LONG TERM...(SUNDAY NIGHT THROUGH THURSDAY)
ISSUED AT 326 AM EST FRI FEB 5 2016

THERE IS LITTLE QUESTION THIS COMING WEEK WILL START OUT WARMER THAN
NORMAL BUT A SURGE OF ARCTIC AIR WILL BRING TEMPERATURES BELOW
NORMAL FOR WEDNESDAY AND THURSDAY. THERE IS ALSO LITTLE QUESTION
THERE WILL BE SNOW NEARLY EVERY DAY THIS COMING WEEK. THE MAIN
QUESTION IS HOW MUCH SNOW?

THE MODELS CONTINUE TO COME INTO BETTER AGREEMENT AS TO HOW THAT
LARGE SYSTEM THE CLOSES OFF AT UPPER LEVEL LOW OVER THE GREAT LAKES
WILL PLAY OUT IN TIME. OVERALL OUR TWO EAST ASIAN JET
STREAKS...BOTH OVER 180 KNOTS HELP TO DEVELOP A LARGE WEST COAST
UPPER LEVEL RIDGE. THAT HELPS THE SYSTEM NOW MOVING ON SHORE OVER
WESTERN CANADA AND THE PACIFIC NORTHWEST TO DIG STRONGLY TO THE
SOUTHEAST. SEEMS SOME OF THAT JET ENERGY MAKES IT UP THE EAST SIDE
OF THE SYSTEM OVER THE GULF OF ALASKA LEADING TO A 170 KNOT JET
CORE HEADING TOWARD THE EXTREME SOUTHEASTER PART OF ALASKA ON
SUNDAY. THAT ONLY HELPS BUILD THE UPPER RIDGE EVEN MORE SO. WE
THEN HAVE A 150 KNOT JET CORE DIVING DOWN THE WEST SIDE OF THE
DEEPENING CENTRAL CONUS TROUGH. BY MONDAY MORNING A LARGE UPPER
LOW DEVELOPS OVER MICHIGAN AND REMAINS NEAR MICHIGAN INTO TUESDAY.
OUR SECOND EAST ASIAN JET CORE REACHES THE DATELINE BY MONDAY
NIGHT... FORCING SOME OF THE ENERGY FROM THE STORM IN THE GULF OF
ALASKA OVER THE WESTERN RIDGE. THAT FINALLY PUSHES THE UPPER LOW
OVER MICHIGAN TO THE EAST IN THE WEDNESDAY TIME FRAME.

SINCE THE SYSTEM STALLS OVER MICHIGAN MONDAY...IT TAKES TILL TUESDAY
FOR THE ARCTIC AIR TO START TO MOVE INTO MICHIGAN. MEANWHILE WHAT WE
WILL HAVE TO WATCH IS WILL THE ECMWF BE CORRECT OR THE GFS IN TERMS
OF WHAT THE 700 MB LOW DOES.  THE GFS OPENS IT UP QUICKLY AND SO ON
MONDAY THE DEEP MOISTURE IS OVER LAKE MICHIGAN AND LAKE HURON.
MEANWHILE THE ECMWF IS MUCH SLOWER TO OPEN UP THE 700 MB LOW SO WE
REMAIN IN THE DEEP MOISTURE INTO TUESDAY. I WENT WITH THAT IDEA AS
THE GFS TYPICALLY OPENS THESE SYSTEM TO QUICKLY. WITH THE ECMWF IDEA
WE WOULD HAVE A STEADY SNOW EVENT MONDAY INTO TUESDAY MORNING BEFORE
THE LAKE EFFECT KICKS IN.

BOTH MODELS SHOW THE LAKE EFFECT KICKING IN TUESDAY AND LASTING
THROUGH THURSDAY. THIS WILL BE A NORTHWEST FLOW TYPE EVENT AND WITH
850 TEMPS GETTING TO NEAR -20C... THE DGZ WILL BE NEAR THE GROUND...
SO SNOW FLAKE SIZE WILL BE SMALL. STILL IT WOULD BE PROLONGED EVENT
SO WE COULD SEE OVER A FOOT OF SNOW I LAKE SHORE AREAS BY THE END OF
THE WEEK. I HAVE HIGH POPS WEST OF US-131 TUE THROUGH THURSDAY FOR
THIS.

.WEEK TWO OUTLOOK...

THE NEXT THING TO WATCH IS A SECOND PUSH OF EVEN COLDER AIR... IF
THIS AIR CAN REACH US...EARLY IN THE FOLLOWING WEEK IT WOULD BY FAR
BE THE COLDEST AIR OF THE SEASON. 850 MB TEMPS ARE NEAR -30C WITH
THIS EVENT. THERE COULD BE A VALENTINES DAY SNOWSTORM WITH THIS TOO.
IT WILL DEPEND ON HOW MUCH THE MJO CAN KEEP A SECOND DEEP EASTERN
TROUGH FROM FORMING.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z SATURDAY MORNING)
ISSUED AT 702 AM EST FRI FEB 5 2016

FOR THE MOST PART THERE IS VFR CONDITIONS ACROSS THE TAF SITES AT
1130Z. HOWEVER THERE IS AN AREA OF SNOW SHOWERS CURRENTLY CROSSING
LAKE MICHIGAN. BEHIND THAT IS A LARGE AREA OF MVFR CIGS. THE MVFR
CIGS WILL SPREAD ACROSS THE TAF SITES INTO THIS AFTERNOON BEHIND
THE LINE OF SHOWERS. IT MAY TAKE UNTIL EARLY AFTERNOON FOR THESE
CIGS TO REACH GRR AND LATE AFTERNOON FOR THE I-69 TAF SITES.

ANOTHER ISSUE TO BE AWARE OF IS CONVECTIVE SNOW SHOWERS TODAY. THE
MODELS INDICATE WE HAVE SOME WEAK INSTABILITY OVER CENTRAL AND
SOUTHERN LOWER MICHIGAN THIS AFTERNOON. I EXPECT SOME SCATTERED
SNOW SHOWERS TO DEVELOP AND MOVE EAST WITH TIME JUST AHEAD OF THE
COLD FRONT MOVING THROUGH THE AREA. AHEAD OF THE FRONT WE HAVE
WINDS FROM THE SOUTH SOUTHWEST...WHILE BEHIND THE FRONT WINDS AREA
MORE WEST OR WEST NORTHWEST. WERE THESE AIR STREAMS MEET IS WHERE
THE SHOWERS ARE EXPECTED TO DEVELOP. MOST OF THE SNOW SHOWERS
WILL BE DURING THE LATE MORNING INTO THE LATE AFTERNOON. I DID NOT
PUT THESE IN THAT TAFS SINCE THE SHOWERS WILL BE SCATTERED.
HOWEVER... GIVEN IT IS CONVECTIVE ANY OF THESE SHOWERS WILL HAVE
LOCAL IFR WITH THEM.

&&

.MARINE...
ISSUED AT 326 AM EST FRI FEB 5 2016

WINDS AND WAVES WILL REMAIN RELATIVELY LIGHT THROUGH TONIGHT. SW
WINDS WILL INCREASE A BIT SATURDAY.


&&

.HYDROLOGY...
ISSUED AT 258 PM EST WED FEB 3 2016

MINOR FLOODING IS POSSIBLE THIS WEEK... ESPECIALLY IN LOWLAND AREAS
NEAR RIVERS. SOME RIVERS MAY EXCEED BANKFULL DUE TO SNOW MELT AND
PRECIPITATION FROM THE LAST STORM. TOTAL PRECIPITATION OF ONE TO
AROUND ONE AND A HALF INCHES FELL. RIVER FLOOD ADVISORIES HAVE BEEN
ISSUED FOR SYCAMORE CREEK AT HOLT... FLAT RIVER AT SMYRNA... ROGUE
RIVER AT ROCKFORD... MAPLE RIVER AT MAPLE RAPIDS AND GRAND RIVER AT
IONIA.

&&

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

$$

SYNOPSIS...LAURENS
SHORT TERM...LAURENS
LONG TERM...WDM
AVIATION...WDM
HYDROLOGY...63
MARINE...LAURENS


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