Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 140705
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
305 AM EDT MON JUL 14 2014

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

.SYNOPSIS...
ISSUED AT 305 AM EDT MON JUL 14 2014

WE WILL SEE ONE MORE MILD DAY WITH A LOW CHANCE OF A FEW SHOWERS AND
STORMS ACROSS THE AREA. A COLD FRONT AND WAVE OF LOW PRESSURE WILL
USHER IN MUCH COOLER TEMPERATURES ACROSS THE AREA. THIS WILL ALSO
BRING A GOOD CHANCE OF RAIN SHOWERS WITH SOME EMBEDDED THUNDER...
ESPECIALLY FURTHER NORTH CLOSER TO THE LOW. THE COLD AIR COMING IN
OFF OF LAKE MICHIGAN WILL ALSO HELP TO ENHANCE THE SHOWER ACTIVITY.
SHOWERS WILL REMAIN POSSIBLE THROUGH WEDNESDAY BEFORE THE WEATHER
QUIETS DOWN FOR THE END OF THE WEEK.

&&

.SHORT TERM...(TODAY THROUGH WEDNESDAY)
ISSUED AT 305 AM EDT MON JUL 14 2014

MAIN FOCUS IS PCPN CHCS/CONMVECTION CHCS THROUGH THE PERIOD AS WE
SEE AN UPPER LOW DIG SE OVER THE AREA CENTERED AROUND OVERNIGHT
TONIGHT AND ON TUE.

PESKY SHOWERS CONTINUE TO SURVIVE ALONG THE I-94 CORRIDOR EARLY THIS
MORNING AS THEY HEAD EAST TO SE LOWER. THESE SHOWERS ARE ALONG AND
JUST OUT AHEAD OF A SFC FRONT IN THE VICINITY. ALSO AIDING TO THE
SHOWERS HOLDING TOGETHER IS THE RRQ OF AN UPPER JET STREAK NNE OF
THE AREA EARLY THIS MORNING. WE EXPECT THE FRONT AND RRQ DYNAMICS
MOVE OUT IN THE NEXT COUPLE OF HOURS...AND LEAVE A SHORT BREAK IN
THE PCPN CHCS.

A CHC OF SHOWERS AND EVEN A STORM WILL BECOME POSSIBLE ONCE AGAIN BY
THIS AFTERNOON AS ANOTHER FRONT ACROSS WI PRESSES INTO THE AREA. THE
CHC OF PCPN TODAY WILL BE LIMITED GREATLY BY THE ENTRANCE REGION TO
ANOTHER STRENGTHENING JET STREAK MOVING OVERHEAD AND PROVIDING
SUBSIDENCE TO THE AREA. ALSO...A SOMEWHAT STABILIZING FLOW OFF OF
LAKE MICHIGAN WILL LIMIT THE INSTABILITY A BIT.

THE BETTER CHC OF SHOWERS AND A STORM WILL INCREASE THIS EVENING AND
CONTINUE THROUGH A GOOD PORTION OF THE DAY ON TUE. THIS IS WHEN THE
MAIN UPPER LOW NOW MOVING INTO MN MOVES RIGHT OVER THE CWFA. PLENTY
OF COOL AIR ALOFT WITH THIS FEATURE ALONG WITH A STRONG VORT/PV
ANOMALY. THE COOLER AIR COMING IN OVER LAKE MICHIGAN WILL PRODUCE
DELTA T/S OF MID TEENS C OVER THE LAKE...CHANGING TOTALLY FROM THE
STABILIZING EFFECTS ON MON AFTERNOON. THIS WILL ONLY HELP TO ENHANCE
THE PCPN OVER THE AREA...ESPECIALLY UP NORTH CLOSER TO THE LOW AND
WRAP AROUND MOISTURE.

THE BEST AND MORE CONCERNTRATED MOISTURE AND PCPN WILL MOVE OUT
LATER ON TUE WITH THE UPPER LOW...LEAVING ONLY A SMALL CHC OF A POP
UP SHOWER OVER THE AREA ON TUE NIGHT. SHOWER CHCS WILL INCREASE A
LITTLE WED AFTERNOON COMPARED TO TUE NIGHT AS THE AREA REMAINS UNDER
CYCLONIC FLOW ALOFT AND SOME DIURNAL INSTABILITY CAN BUILD WITH A
LITTLE BIT OF SUN. FCST SOUNDINGS SHOW A RELATIVELY SHALLOW
INVERSION WITH THE COOL AIR ALOFT MOVING EAST THAT WILL LIMIT PCPN
TO JUST SHOWERS VS. A POSSIBLE STORM.

.LONG TERM...(WEDNESDAY NIGHT THROUGH SUNDAY)
ISSUED AT 305 AM EDT MON JUL 14 2014

LITTLE CHANGE TO THE FORECAST. CERTAINTY IS HIGH FOR DRY CONDITIONS
THURSDAY AND FRIDAY WITH WARMING TEMPERATURES.

A BIT LESS CERTAINTY EXISTS SATURDAY DUE TO DIFFERING MODEL
SOLUTIONS. DECIDED TO KEEP IT DRY IN LINE WITH THE 14/00Z ECMWF AND
13/12Z FIM RUNS. DISCOUNTED THE WETTER 14/00Z GFS WHICH IS THE MOST
AGGRESSIVE WITH LIFTING A SOUTHERN STREAM CUTOFF LOW AND ATTENDANT
MOISTURE INTO THE REGION.

IMPROVING CONFIDENCE FOR SCATTERED SHOWERS AND THUNDERSTORMS SUNDAY
AFTERNOON . THIS IS DUE TO BETTER AGREEMENT BETWEEN THE 14/00Z RUNS
OF THE ECMWF AND GFS. BOTH MODELS BRING DEEPER MOISTURE AND
ATTENDANT PRECIPITATION INTO MICHIGAN LATE IN THE DAY AND THIS COULD
SPILL OVER INTO SUNDAY NIGHT AND MONDAY.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z MONDAY NIGHT)
ISSUED AT 1207 AM EDT SUN JUL 13 2014

VFR CONDITIONS ARE EXPECTED TO PREVAIL OVER THE NEXT 24 HOURS BUT
IT WILL NOT BE CLOUD FREE. THERE WILL BE PERIODS OF CLOUDS WITH
BASES OF 4000-6000 FT AND ISOLATED TO SCATTERED RAIN SHOWERS. SOME
TSTMS ARE ALSO POSSIBLE LATE MONDAY AFTERNOON AND EVENING WITH THE
ARRIVAL OF THE UPPER LOW/COLD POOL ALOFT FROM THE NORTHWEST...
WHICH COULD LEAD TO BRIEF PERIODS OF MVFR CIGS/VSBYS AND GUSTY SFC
WINDS.

&&

.MARINE...
ISSUED AT 305 AM EDT MON JUL 14 2014

WE WILL BE ISSUING BEACH HAZARD HEADLINES AND A SMALL CRAFT ADVISORY
FOR TONIGHT THROUGH TUESDAY. WE ARE ALSO ADDING WATERSPOUTS TO THE
FCST FOR THE SAME TIME FRAME.

MODELS ARE IN GOOD AGREEMENT IN BRINGING A PRETTY BRISK GRADIENT IN
ACROSS THE NEARSHORE WATERS OVERNIGHT TONIGHT THROUGH TUE BEHIND THE
DEPARTING SFC LOW. GOOD COLD AIR ADVECTION INTO THE AREA WILL HELP
TO BUILD THE WAVES EFFICIENTLY.

WATERSPOUT POTENTIAL LOOKS GOOD ENOUGH FROM OVERNIGHT TONIGHT INTO
TUE TO WARRANT A MENTION IN THE FCST. THE WATERSPOUT NOMOGRAM SHOWS
WATERSPOUTS WILL BE POSSIBLE WITH DELTA T/S AROUND 13 TO 15C AND A
CONVECTIVE CLOUD LAYER OF 15-20K FT OVER THE WATERS. THE UPPER AIR
PATTERN WITH A STRONG UPPER LOW DROPPING IN OVER THE GREAT LAKES IS
ALSO TYPICALLY CONDUCIVE FOR WATERSPOUTS AT THIS TIME OF THE YEAR.

&&

.HYDROLOGY...
ISSUED AT 306 PM EDT SUN JUL 13 2014

QPF VALUES AT THIS POINT DO NOT LOOK LIKE THEY WILL ADD MUCH TO
THE ONGOING RUNOFF. SO RIVER LEVELS SHOULD NOT REFLECT THE
FORECASTED MINIMAL CONTRIBUTION FROM THE MON TO TUE EVENT. WILL
NEED TO MONITOR IT THOUGH AS THE LAKE WILL ADD SOME MOISTURE TO
THIS SYSTEM...WHICH COULD ENHANCE THE QPF.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LM...SMALL CRAFT ADVISORY FROM MIDNIGHT TONIGHT TO 8 PM EDT TUESDAY
     FOR LMZ844>849.

&&

$$

SYNOPSIS...NJJ
SHORT TERM...NJJ
LONG TERM...TJT
AVIATION...MEADE
HYDROLOGY...MJS
MARINE...NJJ





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