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000
FXUS63 KGRR 121624
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
1224 PM EDT SAT APR 12 2014

LATEST UPDATE...
UPDATE/HYDRO

.SYNOPSIS...
ISSUED AT 330 AM EDT SAT APR 12 2014

AFTER A DRY MORNING THIS MORNING...A WET PERIOD IS IN STORE FOR THE
AREA FOR THE REMAINDER OF THE WEEKEND AND INTO THE DAY ON MONDAY.
WAVES OF RAIN AND THUNDERSTORMS WILL MOVE ACROSS THE AREA BEGINNING
THIS AFTERNOON...AND CONTINUE INTO MONDAY MORNING. HEAVY AMOUNTS OF
RAINFALL ARE LIKELY...WITH THE HEAVIEST RAIN EXPECTED NORTH OF THE
I-96 CORRIDOR. FLOODING IS VERY POSSIBLE ACROSS THE NORTHERN HALF OF
THE AREA. WARM AIR CAN BE EXPECTED THIS WEEKEND FOR A GOOD PORTION
OF THE AREA.

THE HEAVY RAINS WILL TRANSITION OVER TO LIGHT SNOW ON MONDAY AND
MONDAY NIGHT AS MUCH COLDER AIR MOVES IN. LIGHT SNOW ACCUMULATIONS
WILL BE POSSIBLE.

&&

.UPDATE...
ISSUED AT 1222 PM EDT SAT APR 12 2014

MAIN FOCUS HAS BEEN ON CONVECTIVE THREATS THIS AFTERNOON. STORMS
HAVE FIRED UPSTREAM IN A ZONE OF STRONG 850MB MOISTURE TRANSPORT.
THE LLJ UPSTREAM IS ON THE ORDER OF 40-45 KNOTS. THE LLJ WEAKENS
JUST A BIT THIS AFTERNOON AS IT PIVOTS EAST INTO OUR AREA.
EXPECTING SHOWERS AND STORMS TO DEVELOP/MOVE EAST INTO OUR AREA
THIS AFTERNOON. WITH DRIER AIR OVER LOWER MICHIGAN THOUGH EXPECT A
SLIGHT WEAKENING TREND. 2.00 INCH DIAMETER HAIL HAS OCCURRED THIS
MORNING IN NORTHERN ILLINOIS.

LOOKING FOR A HAIL THREAT TO CONTINUE...BUT LIKELY NOT AS
SIGNIFICANT AS UPSTREAM OVER WI/IL. A GOOD PUSH OF 850MB MOISTURE
TRANSPORT DOES OCCUR OVER SOUTHWEST LOWER THIS AFTERNOON...SO WE
WILL BE MONITORING STORMS FOR HAIL. IN ADDITION...A DRY SUB CLOUD
LAYER MAY LEAD TO ENHANCED WIND GUSTS THROUGH EVAPORATIVE COOLING
PROCESSES. STRONG WIND GUSTS MAY END UP BEING THE BIGGER THREAT
THIS AFTERNOON AND EVENING ACROSS OUR AREA GIVEN THE DRY AIR IN
PLACE IN LOW LEVELS ALONG WITH A BETTER MIXED ENVIRONMENT DUE TO
THE SUNSHINE THIS MORNING. GRADIENT WINDS ACROSS THE SOUTH HAVE
ALREADY NUDGED INTO THE 20-25 KNOT RANGE.

HIGH TEMPERATURES WILL PUSH INTO THE 70S ACROSS THE SOUTHERN HALF
OF THE FORECAST AREA. A WARM FRONT LAYING ACROSS THE I96 CORRIDOR
WILL KEEP CENTRAL LOWER MICHIGAN COOLER.

&&

.SHORT TERM...(TODAY THROUGH MONDAY)
ISSUED AT 330 AM EDT SAT APR 12 2014

MAIN CONCERNS IN THE SHORT TERM HAVE TO DO WITH THE HEAVY RAIN
POTENTIAL AND CONVECTION THREATS THROUGH THE PERIOD. WE HAVE
MAINTAINED THE FLOOD WATCH AS IS WITH GOOD RUN TO RUN CONTINUITY IN
THE MODELS. VERY LITTLE IN THE WAY OF CHANGES HAVE BEEN MADE TO THE
FCST.

THE QUIETEST PERIOD OF THE SHORT TERM WILL BE THE FIRST FEW HOURS OF
THE FCST THIS MORNING. A SMALL AREA OF HIGH PRESSURE IS CURRENTLY
MOVING EAST ACROSS THE CWFA EARLY THIS MORNING. LURKING TO OUR SW
HOWEVER IS A DEVELOPING WARM FRONT FROM NEAR CHICAGO AND BACK TO THE
WEST. THIS WARM FRONT WILL MAKE A MOVE INTO THE AREA AFTER 12Z THIS
MORNING AS LOW PRESSURE ACROSS THE PLAINS MOVES TOWARD THE AREA. WE
EXPECT A QUICK WARMUP THIS MORNING...ESPECIALLY ACROSS THE SRN HALF
OF THE CWFA...ALONG WITH WINDS PICKING UP FROM THE SOUTH.

WE ARE EXPECTING SHOWERS AND STORMS TO MOVE INTO THE NW PORTION OF
THE CWFA DURING THE AFTERNOON HOURS TODAY. THE WARM FRONT WILL
INITIALLY REMAIN DRY THIS MORNING IN OUR AREA. WE EXPECT IT TO
BECOME MORE ACTIVE THIS AFTERNOON AS THE LLJ FEEDING SHOWERS AND
STORMS ACROSS SE SOUTH DAKOTA AT 07Z THIS MORNING WILL TRANSLATE
EAST INTO THE AREA TOWARD 18Z THIS AFTERNOON. WE EXPECT THE BEST
COVERAGE OF RAIN TO OCCUR ALONG AND NORTH OF THE WARM FRONT WHICH
WILL BE NEAR I-96 THIS AFTERNOON. WE EXPECT ANY CONVECTION TO BE
MAINLY ELEVATED IN NATURE BEING NORTH OF THE FRONT. FCST SOUNDINGS
INDICATE RATHER THIN CAPE. SEVERE THREAT DOES NOT LOOK REALLY
GOOD...SOME MICROBURSTS WILL BE POSSIBLE WITH SOME DRY AIR IN THE
LOWER LEVELS INITIALLY.

WE WILL SEE THE AFTERNOON CONVECTION MOVE E/NE OF THE AREA BY THIS
EVENING...ONLY TO BE REPLACED BY ANOTHER LLJ WHICH WILL FIRE MORE
SHOWERS AND STORMS FOR THE TONIGHT PERIOD. AGAIN...WE ARE THINKING
THAT MOST OF THE PCPN WILL BE ALONG AND NORTH OF THE FRONT WHICH
WILL BE ACROSS THE NRN COUNTIES ONCE AGAIN. ONCE THE SECOND LLJ
MOVES EAST BY SUN MORNING...WE SHOULD SEE RESIDUAL PCPN SWING SE
THROUGH THE AREA AND DIMINISH IN COVERAGE FOR A SHORT TIME SUN
MORNING. THE FRONT MAY DRIFT A LITTLE FURTHER SE BRIEFLY.

THE PERIOD OF HEAVIEST RAIN STILL LOOKS TO COME BEGINNING SUN
AFTERNOON AND LAST THROUGH AROUND DAYBREAK ON MON. THIS IS WHEN THE
MAIN SFC LOW LIFTS OUT FROM THE SW AND MOVES ACROSS SOUTH
CENTRAL/SOUTHEAST LOWER. A 60 KNOT LLJ WILL RIDE OUT AHEAD OF THIS
LOW AND BRING COPIOUS AMOUNTS OF MOISTURE INTO THE AREA AND OVER THE
FRONT. THUNDER WILL REMAIN LIKELY UNTIL THIS LLJ PASSES EAST OF THE
AREA ON MON MORNING. COLDER AIR WILL THEN WRAP IN FROM THE NW DURING
THE DAY ON MON. THERE LOOKS TO BE A SHORT PERIOD OF SNOW ACROSS THE
NW HALF OF THE CWFA BEFORE THE PCPN ENDS MON AFTERNOON.

.LONG TERM...(MONDAY NIGHT THROUGH FRIDAY)
ISSUED AT 330 AM EDT SAT APR 12 2014

STILL CANT RULE OUT THE POSSIBILITY OF A COUPLE INCHES OF WET SNOW
MONDAY NIGHT ON THE BACK SIDE OF THIS SYSTEM. THE PREVIOUS RUN OF
THE ECMWF... AND NOW THE LATEST RUN OF THE NAM... SHOW A QUARTER
INCH OR MORE OF QPF IN THE COLD AIR AND SUGGEST SOME ACCUMULATIONS
COULD OCCUR ESPECIALLY FROM GRR TO THE SOUTH AND EAST.

EVEN IF WE DO NOT SEE MUCH IN THE WAY OF SNOW ACCUMULATION MONDAY
NIGHT... THE TUESDAY MORNING COMMUTE COULD STILL BE IMPACTED BY
SLICK ROADS AS TEMPERATURES PLUNGE DOWN INTO THE MID 20S CAUSING ANY
RESIDUAL MOISTURE TO FREEZE UP. THIS MAY LEAD TO PATCHES OF BLACK
ICE.

HIGH PRESSURE BUILDING IN ON TUESDAY SHOULD END ANY LINGERING SNOW
SHOWERS BY AFTERNOON... FOLLOWED BY A VERY COLD NIGHT TUESDAY NIGHT
WITH LOWS AROUND 20. THE MID TO LATE WEEK PERIOD WILL FEATURE
RELATIVELY QUIET WEATHER WITH TEMPERATURES MODERATING BACK TO CLOSER
TO NORMAL VALUES.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z SUNDAY MORNING)
ISSUED AT 754 AM EDT SAT APR 12 2014

THE PRIMARY AVIATION CONCERN IS THE TSTM POTENTIAL FOR THIS
AFTERNOON AND TONIGHT. CONFIDENCE IS GROWING THAT NUMEROUS TSTMS
NOW FORMING OVER SRN MN AND NRN IA WILL TRACK INTO SRN LWR MI
AFTER 18Z AND IMPACT MUCH OF THE AREA THROUGH EARLY EVENING.

AFTER MIDNIGHT TONIGHT THE COVERAGE OF STORMS SHOULD DECREASE OVER
SRN LWR MI WHILE BECOMING MORE CONCENTRATED FARTHER NORTH OVER
CENTRAL AND NRN LWR MI. GRR AND MKG WILL PROBABLY CONTINUE TO BE
CLIPPED BY THESE STORMS OVERNIGHT WHILE THE TERMINALS SOUTH AND
EAST OF GRR STAY PREDOMINATELY DRY.

CLOUD BASES TODAY AND THIS EVENING ARE EXPECTED TO MOSTLY AT OR
ABOVE 7K FEET BUT CIGS SHOULD LOWER INTO THE MVFR OR EVEN IFR
CATEGORY LATE TONIGHT AS SFC DEW POINTS RISE INTO THE LOWER 50S.


&&

.FIRE WEATHER...
ISSUED AT 353 AM EDT SAT APR 12 2014

WE CONTINUE TO EXPECT AN ELEVATED FIRE DANGER WILL EXIST TODAY...
MAINLY ACROSS THE SRN HALF OF THE AREA WHICH WILL SEE MORE
SUNSHINE...BETTER WARMING AND STRONGER WINDS AS THE WARM FRONT
MOVES TO AROUND I-96 THIS AFTERNOON. DEW POINTS ARE EXPECTED TO
SLOWLY INCREASE WHICH SHOULD LIMIT THE FIRE DANGER A BIT. WE
BELIEVE THAT THE AREA SHOULD REMAIN UNDER WARNING CRITERIA...
ESPECIALLY WITH CLOUDS AND PCPN MOVING IN DURING THE AFTERNOON.

&&

.HYDROLOGY...
ISSUED AT 1222 PM EDT SAT APR 12 2014

RIVER FORECASTS THIS MORNING INCORPORATED 48 HOURS OF FORECAST
RAINFALL VS THE TYPICAL 24 HOURS. INCREASED CONFIDENCE IN THE RAIN
MADE THIS DECISION AS NEW MODEL RUNS CONTINUE TO SHOW HEAVY RAIN
CENTERED OVER OUR AREA. WE HAVE SENT OUT 6 NEW RIVER WARNINGS THIS
MORNING BASED ON THE RAINFALL FORECAST AS WELL AS 7 RIVER
ADVISORIES. MORE WARNINGS AND ADVISORIES ARE POSSIBLE AS WE MOVE
FORWARD.

A FLOOD WATCH REMAINS IN EFFECT THROUGH MONDAY MORNING. FORECAST
RAINFALL EVEN WITH NEW MODEL RUNS THIS MORNING CONTINUES TO LOOK
LIKE AROUND AN INCH FOR THE FAR SOUTHEAST TO POTENTIALLY 3 PLUS
INCHES OVER CENTRAL LOWER MICHIGAN. WPC GUIDANCE IS EVEN HIGHER
WHICH IS IN THE REALM OF POSSIBILITIES.

HYDRO REMAINS THE MAIN CONCERN THE NEXT COUPLE OF DAYS AS THE
PRECIP FALLS AND INTO NEXT WEEK AS IT ROUTES DOWN RIVERS AND
STREAMS.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...FLOOD WATCH THROUGH MONDAY MORNING FOR MIZ037>040-043>046-
     050>052-056>058-064.

LM...NONE.
&&

$$

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