Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 111717
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
117 PM EDT FRI APR 11 2014

LATEST UPDATE...
AVIATION

.SYNOPSIS...
ISSUED AT 330 AM EDT FRI APR 11 2014

MOST OF THE AREA WILL SEE DRY AND MILD CONDITIONS THROUGH EARLY
SATURDAY. THERE IS A CHANCE OF A FEW LIGHT RAIN SHOWERS ACROSS
CENTRAL LOWER MICHIGAN LATER THIS AFTERNOON AND EARLY THIS EVENING
AS A WEAK WAVE OF LOW PRESSURE MOVES ACROSS CENTRAL AND NORTHERN
LOWER MICHIGAN.

THE AREA WILL ENTER INTO A WET PERIOD BEGINNING SATURDAY AFTERNOON
AND THEN LASTING INTO THE DAY ON MONDAY. A FRONTAL SYSTEM WILL MOVE
INTO THE AREA AND STALL OUT FOR A GOOD MAJORITY OF THE WEEKEND.
WAVES OF LOW PRESSURE WILL MOVE ALONG THE FRONT AND BRING WAVES OF
SHOWERS AND THUNDERSTORMS TO THE AREA. HEAVY RAINFALL AMOUNTS
THROUGH THE PERIOD WILL BE THE BIGGEST CONCERN.

&&

.UPDATE...
ISSUED AT 1200 PM EDT FRI APR 11 2014

TWO ITEMS TO KEEP AN EYE ON THIS AFTERNOON ARE THE AFFECTS OF THE
SHORTWAVE PRESSING IN FROM THE WEST AND HOW WARM WE GET IN THE SOUTH.

REGARDING THE SHORTWAVE...ITS CURRENT POSITION CAN BE SEEN EASILY
IN THE VISIBLE IMAGERY ACROSS MN/WI. SHOWERS ARE ASSOCIATED WITH
THE SHORTWAVE WITH QUITE A FEW SITES PICKING UP SOME LIGHT
ACCUMULATION ON THE ORDER OF A HUNDREDTH TO AROUND A TENTH IN
SPOTS. SOME LIGHTNING AS ALSO BEEN NOTED. FEEL THE CLOUDS WILL
THICKEN ACROSS THE NORTH THIS AFTERNOON WITH SHOWERS SPREADING
INTO THE POINTS NEAR LUDINGTON AND PENTWATER TOWARDS 400 PM. SOME
ISOLATED SHOWERS WILL BE POSSIBLE THROUGH THE EVENING GENERALLY
NORTH OF INTERSTATE 96. AT THIS POINT LEAVING OUT THUNDER GIVEN
HOW DRY WE ARE ACROSS THE AREA. MANY SURFACE RH VALUES ARE
DROPPING FROM 30 PCT TO 20 PCT AT THIS TIME. SO...IN GENERAL
PARTLY SUNNY WITH ISOLATED SHOWERS ACROSS CENTRAL LOWER MI. WE
WILL NEED TO KEEP AN EYE ON THUNDER POTENTIAL NEAR THE POINTS
TOWARDS EVENING. HRRR IS SHOWING SOME DECENT SIMULATED
REFLECTIVITY IN THE AREA TOWARDS 00Z. GIVEN THE DRY SUB CLOUD
LAYER STRONG GUSTY WINDS VIA SHOWERS ARE COMPLETELY IN THE REALM
OF POSSIBILITIES.

AS FOR THE TEMPERATURES THINK WE ARE LOOKING AT MID 60S ACROSS THE
SOUTH WITH THE POTENTIAL TO GO A BIT WARMER EVEN IF WE GO SUPER
ADIABATIC DOWN LOW.

&&

.SHORT TERM...(TODAY THROUGH SUNDAY)
ISSUED AT 330 AM EDT FRI APR 11 2014

THE MAIN FEATURE IN THE SHORT TERM IS THE STALLED OUT FRONTAL SYSTEM
AND WET PERIOD EXPECTED FROM THE LATE SAT THROUGH SUN PERIOD /AND
BEYOND/. NO REAL CHANGES HAVE BEEN MADE TO THE FCST AS THE MODEL
CONSENSUS CONTINUES TO TREND MORE TOWARD THE VERY CONSISTENT ECMWF
SOLUTION THAT WE HAVE BEEN LEANING TOWARD NOW FOR DAYS.

FAIRLY QUIET WEATHER IS EXPECTED FOR THE FIRST 24-36 HOURS OF THE
FCST INTO SAT MORNING. WEAK RIDGING AT THE SFC IS IN PLACE RESULTING
FROM SOMEWHAT CONFLUENT FLOW ALOFT. A GOOD DEAL OF MID AND HIGH
CLOUD COVER WILL BE MAKING ITS WAY TOWARD THE AREA TODAY AS AN UPPER
WAVE NEAR THE DAKOTAS/MN BORDER MOVES EAST. THIS WAVE HAS TRENDED
TOWARD A QUICKER ARRIVAL FOR THE NRN PORTION OF THE CWFA. THE WAVE
HAS ONLY A FEW SHOWERS WITH IT NOW...AND IT WILL CONTINUE TO
ENCOUNTER A DRY AIR MASS AS IT MOVES TO THE EAST. THE CHCS OF
MEASURABLE PCPN UP NORTH ARE FAIRLY LOW...WITH THE INITIAL LACK OF
MOISTURE AND THE LACK OF MOISTURE TRANSPORT THAT WILL OCCUR AHEAD OF
THE WAVE. ANY RAIN CHCS SHOULD END JUST AFTER 06Z TONIGHT.

WE WILL SEE THE RAIN SHOWER CHCS INCREASE THEN DURING THE AFTERNOON
HOURS ON SAT. THE FRONT THAT WILL SLIP JUST SOUTH OF THE AREA
TONIGHT IN THE WAKE OF THE WAVE WILL MAKE A RUN BACK NORTH AS A WARM
FRONT. THIS OCCURS AS ANOTHER SHORT WAVE COMES IN FROM THE WEST.
THIS WAVE WILL BE A BIT STRONGER AND RESULT IN BETTER INFLOW FROM
THE GULF OF MEXICO. THE BETTER MOISTURE TRANSPORT SPREADS IN FROM
THE WEST JUST AFTER 18Z ON SAT AND IS FOCUSED ACROSS THE NRN HALF OF
THE CWFA. WE SHOULD SEE TEMPS WARM QUICKLY ON SAT WELL INTO THE 60S
AND LOWER 70S BEFORE CLOUDS THICKEN TOO MUCH AND RAIN STARTS
FALLING.

THE SET UP FOR THE WET PERIOD THEN REALLY STARTS TAKING SHAPE SAT
NIGHT AND MORE SO ON SUN. THE SAT WAVE WILL MOVE THROUGH...HOWEVER
AS IT DOES SO ANOTHER STRONGER LONG WAVE TROUGH DIGS ACROSS THE WRN
PORTION OF THE COUNTRY. THIS SHIFTS THE UPPER FLOW TO MORE OF A SW
FLOW...AND IT BECOMES PARALLEL WITH THE FRONT. WE WILL THEN SEE
WAVES BE EJECTED FROM THE WRN TROUGH RIGHT ALONG THE FRONT. VERY
MOIST AIR /PWATS OF AROUND 1-1.33 INCHES/ SOUTH OF THE FRONT WILL
CONTINUE TO OVERRIDE A TIGHTENING LOW LEVEL THERMAL GRADIENT AS COLD
AIR IS ALSO DRAWN FROM THE NORTH.

THE FAVORED AREA FOR HEAVIER RAIN TOTALS WILL BE ACROSS THE NRN HALF
OF THE CWFA. THE FRONT WILL SINK SOUTH A LITTLE SUN MORNING BEHIND
THE SAT WAVE...BRINGING MORE RAIN SHOWERS INTO PLAY FOR THE SRN
AREAS. THIS WILL SHIFT BACK NORTH AS THE NEXT WAVE MOVES IN LATER ON
SUN.

THUNDER LOOKS LIKE A GOOD BET ACROSS THE AREA WITH THE VERY MOIST
AIR BEING ADVECTED IN ON A 40-50M KNOT LLJ. WE WILL ALSO SEE A
PORTION OF THE AREA BEING IN THE WARM SECTOR WITH FAIRLY WARM AND
MOIST CONDITIONS EXPECTED TO BE IN PLACE. THE MAGNITUDE OF THE
INSTABILITY IS NOT THAT IMPRESSIVE...WHICH LOOKS TO LIMIT THE SEVERE
POTENTIAL FOR THE AREA. DEEP LAYER SHEAR IS SUFFICIENT /40-50 KNOTS/
TO HELP THE POTENTIAL OF ORGANIZING SOME STORMS WITH THE UPPER JET
NEARBY.

.LONG TERM...(SUNDAY NIGHT THROUGH THURSDAY)
ISSUED AT 330 AM EDT FRI APR 11 2014

SUNDAY NIGHT AND MONDAY MORNING LOOKS LIKE A VERY WET PERIOD AS THE
MAIN/FINAL WAVE TRACKS NORTHEAST ALONG THE SFC FRONTAL BOUNDARY...
PASSING OVER SOUTHEAST LOWER MICHIGAN. OVER AN INCH OF RAIN COULD
FALL DURING THIS TIME WITH A FEW TSTMS STILL POSSIBLE OVER THE SRN
CWFA THROUGH 12Z MONDAY.

URBAN AND SMALL STREAM FLOODING WILL BE A POSSIBILITY SUNDAY NIGHT
AND MONDAY MORNING... AND RIVER FLOODING COULD PERSIST WELL INTO
NEXT WEEK DEPENDING ON TOTAL RAIN AMOUNTS AND HEAVY RAIN COVERAGE.
GUIDANCE STILL SUGGESTS STORM TOTALS OF 2-3 INCHES MAY OCCUR...
ESPECIALLY OVER THE MUSKEGON RIVER BASIN.

PRECIP TYPE BECOMES VERY CHALLENGING LATE SUNDAY NIGHT INTO MONDAY
AS TEMPERATURE GRADIENT SHARPENS ALONG THE SFC FRONT AND COLD DRY
AIR BEGINS TO POUR IN FROM THE NORTH. SFC TEMPS AT 12Z MONDAY ARE
EXPECTED TO RANGE FROM AROUND 60 NEAR JXN IN THE WARM SECTOR TO THE
LOWER 30S AT LUDINGTON WHICH SHOULD BE FIRMLY IN THE COLD AIR ON THE
OTHER SIDE OF THE FRONT. ACCUMULATIONS OF WET SNOW CANNOT BE RULED
OUT IN THE NW CWFA LATE SUNDAY SUNDAY NIGHT AND MONDAY MORNING.

FALLING TEMPERATURES ARE ANTICIPATED AREA-WIDE MONDAY AS THE COLD AIR
FLOWS IN BEHIND THE DEPARTING WAVE... WITH MOST LOCATIONS IN THE 30S
BY THE END OF THE DAY. RAIN MAY CHANGE TO A FEW WET SNOWFLAKES
BEFORE ENDING.

TUESDAY THROUGH THURSDAY IS LOOKING RELATIVELY BENIGN WITH SLIGHT
CHANCE OF ISOLATED TO SCATTERED INSTABILITY SHOWERS OF RAIN/SNOW
DUE TO THERMAL TROUGHING ALOFT. MODERATING TEMPS EXPECTED TOWARD THE
END OF THE WEEK.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SATURDAY AFTERNOON)
ISSUED AT 117 PM EDT FRI APR 11 2014

VFR CONDITIONS ARE EXPECTED THROUGH THE NEXT 24 HOURS. CLOUDS WILL
INCREASE SATURDAY MORNING AND THERE COULD BE A FEW RAIN SHOWERS
MOVING INTO FAR WESTERN LOWER MICHIGAN TOWARD NOON...BUT VFR IS
STILL EXPECTED TO CONTINUE.

UNTIL THEN WESTERLY WINDS WILL CONTINUE AT 10 TO 15 KNOTS THIS
AFTERNOON...DROPPING OFF BY EARLY THIS EVENING.

&&

.FIRE WEATHER...
ISSUED AT 427 AM EDT FRI APR 11 2014

THE AREA WILL POTENTIALLY SEE SOME OF THE HIGHEST FIRE DANGER
THUS FAR THIS SPRING ON SATURDAY BEFORE THE RAINS START TO MOVE
IN. TEMPS ARE EXPECTED TO APPROACH THE LOWER 70S ON SAT...AND
WINDS WILL BE INCREASING IN THE AFTERNOON. RIGHT NOW...MIN RH/S
LOOK TO STAY UP SOME AROUND 30 PCT WITH DEW POINTS EXPECTED TO
INCREASE AHEAD OF THE INCOMING SYSTEM. IT IS POSSIBLE THAT WE END
UP DRIER THAN EXPECTED AS DRIER AIR MIXES DOWN...AND THE FIRE
DANGER ENDS UP A LITTLE HIGHER.

&&

.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.
&&

$$

UPDATE...DUKE
SYNOPSIS...NJJ
SHORT TERM...NJJ
LONG TERM...MEADE
AVIATION...JK
FIRE WEATHER...NJJ
HYDROLOGY...MJS






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