Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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000
FXUS63 KGRR 102321
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
721 PM EDT THU APR 10 2014

LATEST UPDATE...
AVIATION

.SYNOPSIS...
ISSUED AT 258 PM EDT THU APR 10 2014

A WEAK  HIGH PRESSURE SYSTEM WILL DRIFT ACROSS THE REGION
TONIGHT INTO SATURDAY...PROVIDING THE REGION WITH MAINLY DRY AND
MILD WEATHER. A SLOW MOVING COLD FRONT WILL CROSS THE GREAT LAKES
REGION SUNDAY INTO MONDAY. THIS SYSTEM WILL BRING WITH IT A
POTENTIAL FOR HEAVY RAIN.  COLDER WEATHER WILL ARRIVE ON MONDAY.

&&

.SHORT TERM...(THIS EVENING THROUGH SATURDAY NIGHT)
ISSUED AT 258 PM EDT THU APR 10 2014

THE MAIN CHALLENGE DEALS WITH THE RISK FOR RAIN SATURDAY INTO
SATURDAY NIGHT.

WARM AIR ADVECTION STRENGTHENS SATURDAY. FOR MUCH
OF THE REGION WITH WILL LEAD TO MILD TEMPERATURES. HOWEVER ACROSS
NORTHERN ZONES...DEEPER SATURATION OCCURS. ELEVATED INSTABILITY IS
SEEN OVER IN WISCONSIN 00Z SUN PLUS A LOW LEVEL JET WILL BE NOSING
IN AROUND THAT TIME. IN ADDITION THE RIGHT ENTRANCE REGION OF AN
UPPER LEVEL JET WILL BE PROVING UPPER LEVEL DIVERGENCE WHICH WILL
ENHANCE THE LIFT.  ALL THIS COULD LEAD TO ELEVATED SHOWERS HERE IN
MI...ESPECIALLY NORTH..,BY THE END OF THE DAY ON SATURDAY...WITH
AN INCREASING RISK FOR RAIN FOR ALL AREAS GOING INTO SATURDAY
NIGHT. THE THUNDER POTENTIAL LOOKS FAVORABLE FOR SATURDAY
NIGHT...SO WILL KEEP THE MENTION IN THE FORECAST.

TEMPERATURES WILL MODERATE FRIDAY INTO SATURDAY AS THE SOUTHERLY
FLOW STRENGTHENS. LOOKS LIKE MUCH OF THE AREA WILL SEE
TEMPERATURES APPROACHING OR EXCEEDING 70 ON SATURDAY. SOMETIMES
THOUGH...ELEVATED CLOUDS AND SHOWERS CAN LEAD TO CHALLENGES IN
THESE SITUATIONS. SATURDAY WILL BE ONE OF THOSE DAYS...SO 70S ARE
NOT A CERTAINTY.

.LONG TERM...(SUNDAY THROUGH THURSDAY)
ISSUED AT 258 PM EDT THU APR 10 2014

MUCH BETTER AGREEMENT IN THE MODELS AS THE GFS HAS TRENDED CLOSE TO
WHAT THE ECMWF HAS BEEN SHOWING OVER THE PAST COUPLE OF DAYS.

A VERY WET SYSTEM COMES TOGETHER OVER THE REGION FOR THE LATTER HALF
OF THE WEEKEND AND INTO MONDAY.  A FRONT BECOMES PARALLEL TO THE
UPPER FLOW AND THEREFORE ONLY SLOWLY SLIPS THROUGH THE CWA.  MUCH OF
SW MI COULD SEE 2 TO 3 INCHES OF RAIN SUNDAY INTO MONDAY...LEADING
TO INCREASED FLOODING CONCERNS ON THE ALREADY HIGH RIVER LEVELS.
THE FRONT SHOULD PASS THROUGH THE CWA FROM NW TO SE ON SUNDAY.  DUE
TO BETTER CONFIDENCE IN THIS OCCURRING MUCH OF THE CWA REMAINS IN
THE WARMER SECTOR FOR AT LEAST THE FIRST HALF OF SUNDAY...SO TRENDED
MAX TEMPS UPWARD.

HARSHLY COLDER AIR FOLLOWS FOR MONDAY AND LINGERS INTO MID WEEK.  H8
TEMPS GO FROM AROUND +9C ON SUNDAY...AND DROPS TO AROUND -10C BY
TUESDAY NIGHT.  A WAVE OF LOW PRESSURE IS EXPECTED TO CROSS SE LOWER
MI SUNDAY NIGHT AND WILL START TO DRAG THIS COLDER AIR INTO THE
AREA.  THE RAIN COULD CHANGE TO SNOW FROM NW TO SE STARTING LATE
SUNDAY NIGHT NW...TO LATE MONDAY AFTERNOON SE.  SNOW ACCUMULATION
CHANCES APPEAR HIGHEST OVER THE NW CWA WHERE 1 TO 4 INCHES WILL BE
POSSIBLE.  ELSEWHERE IT WILL COME DOWN TO HOW QUICKLY WE COOL DOWN
AND HOW SOON THE PCPN MOVES OUT OF THE AREA MONDAY/MONDAY EVENING.

TUESDAY THROUGH THURSDAY WILL BE WELL BELOW NORMAL.  HIGH PRESSURE
SHOULD SUPPRESS MOST PCPN...HOWEVER THERE COULD BE A FEW SNOW
SHOWERS OR RAIN/SNOW SHOWERS WITH THE UNSTABLE COLD AIR ALOFT OVER
THE AREA.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z FRIDAY EVENING)
ISSUED AT 720 PM EDT THU APR 10 2014

EXPECT VFR CIGS/VSBY THROUGH FRIDAY. WINDS WILL BECOME LIGHT AND
VARIABLE BY MIDNIGHT A SURFACE HIGH PRESSURE SYSTEM MOVES OVER
MICHIGAN. AS THE HIGH MOVES TO THE EAST OF MICHIGAN BY LATE
MORNING FRIDAY WINDS WILL INCREASE OUT OF THE SOUTH. SKIES SHOULD
REMAIN CLEAR BELOW 10000 FT AGL THROUGH THE DAY.

&&

.HYDROLOGY...
ISSUED AT 1036 AM EDT THU APR 10 2014

CONFIDENCE IS INCREASING WITH REGARDS TO THE HEAVY RAINFALL
POTENTIAL SAT NIGHT INTO MON. INCREASED RISK FOR GREATER THAN 2
INCHES. SEVERAL ROUNDS OF RAIN ARE EXPECTED. THIS SYSTEM HAS A
COUPLE OF INGREDIENTS THAT COULD LEAD TO HEAVY RAIN WHICH COULD
CAUSE HYDRO IMPACTS. THEY INCLUDE A SLOW MOVING FRONT...IT WILL
CONTAIN ABUNDANT GULF MOISTURE ALONG WITH INSTABILITY. THIS OPENS
UP THE POSSIBILITY OF HEAVY RAIN SHOWERS REPEATING OVER THE SAME
AREA. IN ADDITION THE RIVER LEVELS ARE ELEVATED AND THE GROUND IS
MOIST. OVERALL FLOOD IMPACTS WILL BE DETERMINED WHETHER THESE
ROUNDS OF RAIN OCCUR OVER THE SAME AREA.

SMALL STREAMS WOULD BE IMPACTED FIRST...POSSIBLY SUNDAY...FOLLOWED
BY THE LARGER RIVERS FOR THE REMAINDER OF NEXT WEEK.

WHILE NOT CERTAIN TO HAPPEN...THIS WILL BE SOMETHING
THAT WE WILL NEED TO CLOSELY MONITOR IN THE COMING DAYS.

AS FOR TODAY...RIVERS GENERALLY TRENDING DOWNWARD. THE RAINFALL FOR TODAY
IS NOT EXPECTED TO PRODUCE ENOUGH RUNOFF TO RAISE RIVER LEVELS UP
SIGNIFICANTLY THROUGH SATURDAY.

&&

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

$$

SYNOPSIS...MJS
SHORT TERM...MJS
LONG TERM...JK
AVIATION...WDM
HYDROLOGY...MJS






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