Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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000
FXUS63 KGRR 132352
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
752 PM EDT SUN JUL 13 2014

LATEST UPDATE...
AVIATION

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

AN UNSEASONABLY STRONG LOW PRESSURE SYSTEM OVER ONTARIO REMAINS
NEARLY STATIONARY THROUGH TUESDAY. THIS SYSTEM WILL KEEP OUR WEATHER
MUCH COOLER THAN NORMAL AND UNSETTLED. THERE COULD BE A FEW
THUNDERSTORMS...MAINLY ON MONDAY. A WARMING TREND WILL DEVELOP FOR
THE END OF THE WEEK. TEMPERATURES WILL RETURN TO NEAR NORMAL BY
NEXT WEEKEND.

&&

.SHORT TERM...(THIS EVENING THROUGH TUESDAY NIGHT)
ISSUED AT 306 PM EDT SUN JUL 13 2014

THE MAIN CHALLENGE DEALS WITH THE CHANCES AND AMOUNT OF RAIN WITH
THIS LOW PRESSURE SYSTEM. OVERALL I THINK IT WILL END UP WETTER
THAN MOST MODELS ARE PREDICTING.

DEEPER MOISTURE THROUGH THE DGZ ALONG WITH SOME LIFT ARRIVES
MONDAY NIGHT AND PERSISTS INTO TUESDAY. THE NEW HIGH RES EURO
SHOWS A SECONDARY WAVE DEVELOPING OVER THE RELATIVELY WARM GREAT
LAKES. WRAP AROUND MOISTURE MOVES IN. ALSO...MOISTURE FROM THE
LAKES WILL BE ADDED TO THIS UNSEASONABLY DEEP UPPER LOW LEADING TO
MORE RAIN. CURRENTLY IT LOOKS LIKE NORTHERN ZONES WILL SEE THE
MOST RAIN. HOWEVER...COASTAL LOCATIONS FAVORED BY NORTHWEST FLOW
MAY VERY WELL SEE RATHER WET CONDITIONS MONDAY NIGHT INTO TUESDAY.
WHAT I DID WAS TO INCREASE POPS DURING THIS TIMEFRAME. STILL NEED
TO MONITOR THE THUNDER RISK ON TUESDAY. LIFTED PARCELS FROM THE
MODELS DO NOT APPEAR TO REACH THE FREEZING LEVEL...SO IT LOOKS
LIKE THE THREAT IS MINIMAL. THAT COULD CHANGE DEPENDING ON HOW
MUCH MOISTURE IS ADDED FROM THE LAKE. LOCAL QPF VALUES COULD
APPROACH A HALF INCH.

AS FOR MONDAY...BIG DIFFERENCES IN THE MODELS EXIST. THE NAM
DEVELOPS A WAVE OVER LOWER MI DURING THE DAY. THIS LEADS TO AN
ENHANCED AREA OF SHOWERS AND THUNDERSTORMS STARTING LATE MORNING.
GFS AND HIGH RES EURO ARE MUCH DRIER AND KEEP THIS WAVE SOUTH
THROUGH THE DAY. I WILL KEEP THE THUNDER GOING FOR MONDAY AT THIS
POINT.

WATCHING A FEW SHOWERS TRACKING EAST THROUGH LAKE MI ATTM. WILL
ADD AN ISOLATED SHOWER TO THE LATE AFTN FORECAST GIVEN THE HRRR
SHOWING A FEW SHOWERS PERSISTING INTO NIGHTFALL.

.LONG TERM...(WEDNESDAY THROUGH SUNDAY)
ISSUED AT 306 PM EDT SUN JUL 13 2014

STILL AN OUTSIDE CHANCE FOR A FEW SHOWERS ON WED AS THE LAST UPPER
TROUGH ASSOCIATED WITH THE UPPER LOW SWINGS THROUGH AROUND MID DAY.
THERE WILL LIKELY BE A LAKE SHADOW HOWEVER...SO WILL KEEP MOST
WESTERN AREAS DRY...WITH A 20 POP INLAND.

SURFACE HIGH PRESSURE MOVES IN FOR THE LATTER HALF OF THE WEEK.
NORTHWEST UPPER FLOW GRADUALLY RELAXES AND WE WILL SEE A SLOW WARMUP
WITH RETURN FLOW AT THE SURFACE STARTING THURSDAY NIGHT.  DAYTIME
HIGHS SHOULD RETURN TO NEAR NORMAL VALUES BY FRIDAY AND CONTINUE
INTO THE WEEKEND.

THE NEXT CHANCE OF RAIN SHOULD HOLD OFF UNTIL SUNDAY...AND MAYBE NOT
UNTIL AFTER THIS FORECAST PERIOD.  A SHORT WAVE IS SHOWN TO COME IN
LATE ON SUNDAY ON THE EURO...BUT THE GFS IS SLOWER.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z MONDAY EVENING)
ISSUED AT 752 PM 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 MONDAY AFTERNOON AND EVENING... WHICH
COULD LEAD TO BRIEF PERIODS OF MVFR CIGS/VSBYS AND GUSTY SFC
WINDS.

&&

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

CONFIDENCE IS INCREASING ON A SMALL CRAFT/BEACH HAZARDS DAY LATER
MONDAY NIGHT INTO TUESDAY. FORECASTS WILL FEATURE 4 FOOTERS. THE
LAKE BECOMES UNSTABLE AND NORTHWEST WINDS WILL BE GUSTY GIVEN THE
TIGHT PRESSURE GRADIENT. WAVES COULD EASILY GO HIGHER.


&&

.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...NONE.
&&

$$

SYNOPSIS...MJS
SHORT TERM...MJS
LONG TERM...JK
AVIATION...MEADE
HYDROLOGY...MJS
MARINE...MJS






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