Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 160543
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
143 AM EDT TUE SEP 16 2014

LATEST UPDATE...
AVIATION

.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 1121 PM EDT MON SEP 15 2014

SEEMS THE FOG IS BECOMING EVEN MORE EXTENSIVE THAN I THROUGH WITH
MY LAST UPDATE SO I ONCE AGAIN INCREASED THE FOG IN OUR GRIDS AND
EXTENDED THE FOG TILL 8-9 AM SINCE THE SUN COMES UP LATER NOW AND
THE WIND REMAINS LIGHT OVERNIGHT INTO TUESDAY MORNING. WE MAY NEED
A DENSE FOG ADVISORY BUT I AM NOT SURE ENOUGH TO ISSUE THAT JUST
YET. OTHERWISE OUR TEMPERATURE AND WIND FORECAST IS DOING FINE.

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 06Z TAFS THROUGH 06Z TUESDAY NIGHT)
ISSUED AT 143 AM EDT TUE SEP 16 2014

THE MAIN IMPACT TO AVIATION INTERESTS WITH THE 06Z FCSTS WILL BE
THE FOG/LOW CLOUD TRENDS. SOME PATCHY IFR OCCURRED BEHIND THE AREA
OF RIN THAT MOVED THROUGH IN THE EVENING. WE HAVE SEEN A STRATUS
DECK NOW TAKE SHAPE. THE BACKEDGE OF THIS IS PROGRESSING SE...AND
NOW FOG IS DOMINATING WHERE IT HAS CLEARED OUT. WE HAVE GONE WITH
THE IDEA THAT AS THE INITIAL LOW CLOUDS MOVE OUT...THAT FOG WILL
DEVELOP AND VLIFR LOOKS QUITE POSSIBLE.

THE FOG WILL GRADUALLY MIX OUT/LIFT DURING THE LATE MORNING HOURS.
CONDITIONS SHOULD BECOME VFR AT ALL SITES BY EARLY AFTERNOON WITH
SOME CUMULUS CLOUDS DEVELOPING AS THE LOW LEVEL MOISTURE MIXES OUT.

&&

.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...NJJ
HYDROLOGY...HOVING
MARINE...TJT






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