Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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000
FXUS63 KGRR 152357
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
757 PM EDT MON SEP 15 2014

LATEST UPDATE...
UPDATE

.SYNOPSIS...
ISSUED AT 325 PM EDT MON SEP 15 2014

AFTER RAIN EXITS THE AREA THIS EVENING...HIGH TEMPERATURES IN THE
MID 60S TUESDAY WILL GRADUALLY WARM INTO THE MID 70S BY SATURDAY.
DRY AND COOL OVERNIGHT CONDITIONS MAY ALLOW PATCHY FROST TO DEVELOP
WEDNESDAY NIGHT OVER CENTRAL LOWER MICHIGAN. SHOWERS AND
THUNDERSTORMS WILL BE POSSIBLE BEGINNING LATE FRIDAY.

&&

.UPDATE...
ISSUED AT 757 PM EDT MON SEP 15 2014

I UPDATED OUR GRIDDED WEATHER FORECAST OVERNIGHT TO PUT PATCHY FOG
OVER MOST OF OUR CWA. THE LIGHT RAIN HAS IMPACTED MOST OF OUR CWA
LATE THIS AFTERNOON AND EVENING. THE RAIN IS NOW EXITING THE CWA
AND CLEARING WILL FOLLOW QUICKLY BEHIND THE ENDING OF THE RAIN.
WITH LIGHT SURFACE WINDS...I WOULD EXPECT AREA OF FOG TO DEVELOP
OVERNIGHT. THIS IS SHOWN WELL BY THE NAMDN5 SURFACE VISIBILITY
FORECAST AND CAN BE SEEN IN NAM MODEL SOUNDINGS TOO.

&&

.SHORT TERM...(THIS EVENING THROUGH WEDNESDAY NIGHT)
ISSUED AT 325 PM EDT MON SEP 15 2014

MAIN CHALLENGE IN SHORT TERM IS TIMING THE EXIT OF RAIN...MOST OF
WHICH IS BEHIND THE SURFACE COLD FRONT CURRENTLY MOVING ACROSS THE
NORTHWEST FORECAST AREA. PRECIPITATION AMOUNTS UPSTREAM OVER
WISCONSIN HAVE NOT BEEN IMPRESSIVE - ONLY A FEW HUNDREDTHS IN SPOTS.
COVERAGE HOWEVER IS INCREASING AND EXPECT THIS TO CONTINUE IN THE
SHORT TERM. EXPECT A RAPID EXIT OF PRECIPITATION TO THE SOUTHEAST
THIS EVENING AND EARLY TONIGHT.

ADDED PATCHY FROST WEDNESDAY NIGHT FOR INTERIOR PORTIONS OF NORTH
CENTRAL MICHIGAN. SURFACE HIGH PRESSURE CENTERED OVER THE AREA WILL
BE FAVORABLE FOR RADIATION COOLING...BUT THIS COULD BE OFFSET BY
SOME LOW CLOUDINESS. THANKS APX FOR COORDINATION.

.LONG TERM...(THURSDAY THROUGH MONDAY)
ISSUED AT 325 PM EDT MON SEP 15 2014

THE PRIMARY FOCUS IS ON SHOWER AND TSTM POTENTIAL OVER THE WEEKEND
AND HOW WARM IT GETS.

STRONG WARM ADVECTION KICKS IN ON FRIDAY NIGHT IN RESPONSE TO THE
DIGGING H5 WAVE OVER THE NRN PLAINS. BEST FORCING IS CURRENTLY
PROGGED TO BE ACROSS UPR MI AND NRN LWR MI ON THE NOSE OF THE LOW
LEVEL JET... BUT CHANCE POPS ARE WARRANTED IN SW LWR MI AS THE WARM
FRONT LIFTS THROUGH.

WE SHOULD BE FIRMLY IN THE WARM SECTOR ON SATURDAY WITH MOST OF THE
CONVECTION TO OUR NORTH AND WEST. H8 TEMPS AROUND 15C AND DECENT
MIXING MAY ALLOW FOR HIGHS TOUCHING 80 DEGREES INLAND FROM LAKE
MICHIGAN. HOWEVER A FASTER COLD FRONT SOLUTION AND EARLIER ARRIVAL
OF CLOUDS/SHOWERS COULD MAKE IT DIFFICULT TO GET THAT WARM.

CURRENTLY THE SFC COLD FRONT/SHORTWAVE PASSAGE AND BEST CHANCE OF
RAIN IS PROGGED FOR SATURDAY NIGHT... FOLLOWED BY A COOL DOWN ON
SUNDAY AND MONDAY. THE NEW 12Z RUN OF THE ECMWF IS VERY AGGRESSIVE
WITH THE COLD ADVECTION NEXT MONDAY... SHOWING H8 TEMPS LESS THAN
ZERO INVADING THE STATE. THIS WOULD RESULT IN MORE IN THE WAY OF
CLOUDS AND A CHANCE OF LAKE EFFECT RAIN SHOWERS WHICH IS NOT
CURRENTLY IN THE FCST. IF THIS MODEL TREND CONTINUES THEN FUTURE
FORECASTS FOR A WEEK FROM NOW WILL NEED TO BE TRENDED MORE
PESSIMISTICALLY.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z TUESDAY EVENING)
ISSUED AT 735 PM EDT MON SEP 15 2014

THE MAIN ISSUE TONIGHT IS WHAT HAPPENS WHEN THE RAIN ENDS? THE MID
CLOUDS SHOULD CLEAR FAIRLY QUICKLY AFTER THE RAIN ENDS BUT THE
SURFACE WINDS WILL BE LIGHT AND MOST AREA HAVE GOTTEN AT LEAST A
LITTLE RAIN THIS EVENING. SO THERE WOULD BE THE THREAT OF FOG
DEVELOPING OVERNIGHT. MODEL SOUNDING FROM THE RAP AND NAM SUGGEST
FOG IS POSSIBLE. THE NAMDNG5 SHOWS EXTENSIVE FOG OVER ALL OF THE
TAF SITES BY 12Z. THE ONLY PROBLEM IS WE HAVE AIR ADVECTION
TONIGHT AND THAT TYPICALLY MIXES THE DRY AIR DOWN TO THE BOTTOM OF
THE SOUNDING. SO I DID NOT PUT FOG IN THE TAFS... BUT IT MAY WELL
BE NEEDED TO BE ADDED.

OTHERWISE ONLY A FEW CUMULUS CLOUDS WITH BASES NEAR 4000 FT AGL
ARE EXPECTED TUESDAY.


&&

.MARINE...
ISSUED AT 325 PM EDT MON SEP 15 2014

NO HEADLINES ARE EXPECTED. THERE WILL BE A BRIEF UPTICK IN WAVES
OVERNIGHT WITH A SURGE OF WIND BEHIND THE COLD FRONT PASSING
THROUGH...BUT THEY SHOULD GENERALLY STAY WELL BELOW 4 FEET.


&&

.HYDROLOGY...
ISSUED AT 325 PM EDT MON SEP 15 2014

RIVERS CONTINUE RUNNING NEAR TO ABOVE NORMAL FOR MID SEPTEMBER.
SEVERAL DRY DAYS THIS WEEK WILL ENSURE THIS TREND CONTINUES. BY LATE
IN THE WEEK AND WEEKEND THERE WILL BE A THREAT FOR SHOWERS AND
THUNDERSTORMS AS A FRONT APPROACHES. IT IS TOO EARLY TO TELL HOW
MUCH RAINFALL IS POSSIBLE WITH THIS SYSTEM BUT SIGNIFICANT AMOUNTS
ARE NOT OUT OF THE QUESTION IF THE FRONT MOVES SLOWER AND ALSO
DEPENDING ON WHERE THE REMNANTS OF HURRICANE ODILE MOVE. A CLEARER
PICTURE WILL HOPEFULLY EVOLVE OVER THE NEXT COUPLE DAYS.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LM...NONE.
&&

$$

UPDATE...WDM
SYNOPSIS...TJT
SHORT TERM...TJT
LONG TERM...MEADE
AVIATION...WDM
HYDROLOGY...HOVING
MARINE...TJT






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