Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 190730
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
330 AM EDT SUN APR 19 2015

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

.SYNOPSIS...
ISSUED AT 330 AM EDT SUN APR 19 2015

A LARGE AREA OF LOW PRESSURE WILL MOVE OVER LOWER MICHIGAN LATER
TODAY AND TONIGHT AND BRINGING RAIN TO MUCH OF THE LOWER PENINSULA.
SHOWERY WEATHER WILL BE WITH US THROUGH THURSDAY. MUCH COLDER AIR
WILL FLOW IN BEHIND THE LOW AND WE/LL SEE SOME WET SNOW MIX IN WITH
THE RAIN AT TIMES TUESDAY NIGHT THROUGH THURSDAY. MINOR SNOW
ACCUMULATIONS ARE POSSIBLE TUESDAY NIGHT ALONG US-10 INLAND FROM THE
LAKE. AFTER HIGHS TODAY IN THE 60S...TEMPERATURES WILL BECOME MUCH
COOLER WITH HIGHS IN THE MID 40S TO LOWER 50S THROUGH THE END OF THE
WEEK.

&&

.SHORT TERM...(TODAY THROUGH TUESDAY)
ISSUED AT 330 AM EDT SUN APR 19 2015

FORECAST CONCERNS REMAIN RELATED TO THE EVOLUTION OF THE LARGE AREA
OF LOW PRESSURE HEADED TOWARD THE GREAT LAKES. SHORT RANGE MODELS
ARE IN GOOD AGREEMENT AND HAVE BEEN CONSISTENT IN SHOWING RAIN
DEVELOPING AROUND NOON OVER THE SRN CWA AND THEN MOVING NORTH. THIS
SYSTEM IS A PHASE BETWEEN A LOW OVER SW ONTARIO AND A LOW MOVING
NORTH FROM THE GULF. THE GULF INFLOW WILL PROVIDE PLENTY OF MOISTURE
TO WORK WITH COURTESY OF A 60 KT LLJ. INSTABILITY IS LACKING THOUGH
SO THUNDER ISN/T MUCH OF A CONCERN. STRONG ISENTROPIC LIFT WILL
EVENTUALLY OVERCOME THE DRY LEVELS OF THE LOWER ATMOSPHERE SEEN IN
00Z SOUNDINGS BY LATE MORNING. SHOWERS WILL MOVE NORTH ACROSS THE
CWA THIS AFTERNOON AND CONTINUE TONIGHT. THIS SYSTEM TAKES ON A
LITTLE BIT OF A NEGATIVE TILT WHICH USUALLY SIGNIFIES THAT IT/S A
WET SYSTEM. IN FACT QPF OF 3/4 TO AROUND AN INCH SEEMS LIKELY
THROUGH TUESDAY AS THE SFC LOW AND THEN THE UPPER SYSTEM MOVES
THROUGH. TEMPS WILL COOL FROM FROM MONDAY INTO TUESDAY. IT/S NOT OUT
OF THE QUESTION THAT SOME WET SNOW COULD MIX IN WITH THE SHOWERS
TUESDAY NIGHT ALONG US-10...OTHERWISE JUST RAIN SHOWERS ARE EXPECTED
THROUGH TUESDAY.

.LONG TERM...(TUESDAY NIGHT THROUGH SATURDAY)
ISSUED AT 330 AM EDT SUN APR 19 2015

THE MAIN STORY CONTINUES TO BE THE UNSEASONABLY COLD WEATHER
ASSOCIATED WITH A LARGE UPPER LOW WHICH IMPACTS THE REGION MOST OF
THE COMING WEEK. HIGHS WILL ONLY BE IN THE 40S WEDNESDAY AND
THURSDAY...FOLLOWED BY SLOW MODERATION HEADING INTO NEXT WEEKEND.

THE COLD AIR ALOFT AND CYCLONIC FLOW WILL RESULT IN A GREAT DEAL OF
DIURNAL CLOUDINESS BUT WHERE SKIES MANAGE TO CLEAR AT NIGHT WE COULD
EASILY SEE SOME READINGS DOWN INTO THE 20S. WHILE SCATTERED RAIN OR
MIXED RAIN AND SNOW SHOWERS ARE EXPECTED THROUGH AT LEAST
THURSDAY... THE GFS AND ECMWF CONTINUE TO SHOW LIMITED QPF.

HOWEVER NORMALLY IN THIS SYNOPTIC SET UP WE SEE A FEW DECENT
SHORTWAVES ROTATING AROUND THE UPPER LOW WHICH LEAD TO RELATIVELY
BRIEF PERIODS OF HEAVIER/CONVECTIVE SHOWERS PASSING THROUGH. SO WE
STILL CANT RULE OUT THE POSSIBILITY OF SOME LIGHT SNOW ACCUMULATIONS
TUESDAY NIGHT AND/OR WEDNESDAY NIGHT NORTH OF I-96... AND
PARTICULARLY IN THE HIGHER ELEVATIONS NORTH OF U.S. 10.

THE RISK OF SHOWERS DECREASES TOWARD THE END OF THE WEEK AS THE
UPPER LOW NUDGES EAST AND SURFACE RIDGING NOSES IN.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SUNDAY NIGHT)
ISSUED AT 1155 PM EDT SAT APR 18 2015

MAIN CHANGE WAS TO PUSH BACK THE TIMING OF PRECIPITATION BACK TO
PREDOMINANTLY SUNDAY AFTERNOON. VERY HIGH CONFIDENCE OF VFR
CONDITIONS THROUGH 12Z AND REASONABLY GOOD CONFIDENCE THROUGH 18Z.
AFTER THIS...EXPECT CONDITIONS TO DETERIORATE FAIRLY QUICKLY INTO
MVFR AND POSSIBLE FUEL ALTERNATE CIGS WITH WIDESPREAD PRECIPITATION.

IN THE SHORTER TERM...COULD SEE OCCASIONAL WIND GUSTS OVERNIGHT AT
SOME
OF THE TERMINALS...WITH GUSTINESS BECOMING FAR MORE PREVALENT
AFTER 12Z.


&&

.MARINE...
ISSUED AT 330 AM EDT SUN APR 19 2015

NO CHANGES TO THE SMALL CRAFT ADVISORY. WINDS WILL REMAIN GUSTY FROM
THE EAST TODAY AS LOW PRESSURE

&&

.HYDROLOGY...
ISSUED AT 1126 AM EDT SAT APR 18 2015

A GOOD SOAKING RAINFALL IS STILL ON TRACK TO AFFECT THE ENTIRE AREA
BEGINNING SUNDAY. THE BULK OF THE MOISTURE WILL LIKELY FALL
BETWEEN SUNDAY AFTERNOON INTO MONDAY MORNING WITH SOME GUIDANCE
HINTING AT OVER AN INCH IN SPOTS. ADDITIONAL CHANCES FOR RAIN WILL
SPAN THROUGH THE MIDDLE OF THE WEEK BUT ARE NOT EXPECTED TO BE
QUITE AS ABUNDANT WITH MOISTURE.

RIVERS WILL MAINLY RESPOND IN THE MANNER OF MINOR RISES. THIS SHOULD
MOSTLY CONSIST OF WITHIN BANK RISES. I HAVE A LITTLE MORE CONFIDENCE
IN THINKING MAPLE RAPIDS COULD FLIRT WITH ADVISORY CRITERIA ONCE
AGAIN.
THIS IS PENDING THE AMOUNT OF RAINFALL RECEIVED THROUGH EARLY MONDAY.
OTHERWISE...WE ARE LOOKING PRETTY GOOD WITH THIS NOT BEING A
CONVECTIVE
MODE OF PRECIPITATION...NO REAL SURPRISES AT THIS POINT.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LM...SMALL CRAFT ADVISORY FROM 6 AM THIS MORNING TO 6 PM EDT THIS
     EVENING FOR LMZ844>848.

&&

$$

SYNOPSIS...04
SHORT TERM...04
LONG TERM...MEADE
AVIATION...TJT
HYDROLOGY...JAM
MARINE...04








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