Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 192303
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
703 PM EDT TUE AUG 19 2014

LATEST UPDATE...
AVIATION

.SYNOPSIS...
ISSUED AT 330 PM EDT TUE AUG 19 2014

THUNDERSTORMS WITH HEAVY RAIN AND GUSTY WINDS WILL EXIT TONIGHT AS A
COLD FRONT PASSES THROUGH BUT A FEW SCATTERED SHOWERS WILL LINGER
TONIGHT AND WEDNESDAY.

A STRONG WARM FRONT WILL APPROACH FROM THE SOUTHWEST THURSDAY AND
THURSDAY NIGHT. THIS FRONT MAY TRIGGER ANOTHER ROUND OF HEAVY
THUNDERSTORMS... FOLLOWED BY VERY WARM AND HUMID CONDITIONS FOR THE
UPCOMING WEEKEND.

&&

.SHORT TERM...(THIS EVENING THROUGH THURSDAY NIGHT)
ISSUED AT 330 PM EDT TUE AUG 19 2014

ACTIVE WEATHER WILL CONTINUE OVER THE NEXT FEW HOURS AS APPROACHING
COLD FRONT OVER ERN WI INTERACTS WITH VERY MOIST AND UNSTABLE AIR
MASS OVER SRN LWR MI. CAPES ARE 1500-2000 SOUTH OF I-96 WITH UPR 60
DEW PTS AND PWATS AROUND 1.7. THERE HAVE BEEN SOME REPORTS OF
TORRENTIAL RAIN WITH MORE THAN TWO INCHES AN HOUR... SO URBAN AND
SMALL STREAM FLOODING IS A THREAT IN ADDITION TO THE THREAT FOR
SEVERE/WX DAMAGING WINDS.

RAIN CHANCES DECREASE LATER THIS EVENING AFTER FROPA BUT AS THE
UPPER LOW OVER WRN UPR MI MOVES TO NRN LK HURON LOOK FOR SCATTERED
SHOWERS TO PERSIST. THESE MAY PERK BACK UP TO TSTMS ON WEDNESDAY
AFTERNOON WITH HEATING...PARTICULARLY OVER NRN AND ERN LWR MI. A
LAKE SHADOW WILL PROBABLY DEVELOP FOR WEDNESDAY AFTERNOON WITH NW
LOW LEVEL FLOW SO WILL FEATURE A DRY AFTERNOON FOR THE COASTAL
COUNTIES WHILE GOING WITH LIKELY POPS FOR CLARE... MT PLEASANT...
AND ALMA AREAS.

BEST POPS IN LATER PERIODS LOOKS TO BE THURSDAY NIGHT AS THE WARM
FRONT/LOW LEVEL JET SHIFT TOWARD THE AREA. GUIDANCE...ESPECIALLY THE
ECMWF...LOOKS RATHER AGGRESSIVE SO THERE COULD BE A ROUND OF STRONG
STORMS WITH HEAVY RAINFALL.

.LONG TERM...(FRIDAY THROUGH TUESDAY)
ISSUED AT 330 PM EDT TUE AUG 19 2014

IT WOULD SEEM WE DO ACTUALLY HAVE A CHANCE OF SEEING HIGHS NEAR OR
ABOVE 90 DEGREES OVER A GOOD PART OF OUR CWA THROUGH THE WEEKEND
INTO EARLY NEXT WEEK. AS THE WARM AIR SURGES IN WE WILL LIKELY HAVE
SOME SIGNIFICANT RAINFALL (STRONG THUNDERSTORMS) FRIDAY POSSIBLY
INTO SATURDAY.  THE NEXT THREAT OF THUNDERSTORMS IS MONDAY NIGHT
INTO TUESDAY AS A COLD FRONT MOVES INTO THE AREA.

THE MODELS ARE IN GOOD AGREEMENT ON THE BUILDING OF A SIGNIFICANT
UPPER LEVEL RIDGE OVER THE EAST CENTRAL SECTIONS OF THE CONUS THIS
COMING WEEKEND. THIS IS IN RESPONSE TO STRONGLY DIGGING UPPER LOW
OVER THE PACIFIC NORTHWEST IN THE SAME TIME FRAME. A SIGNIFICANT
SLIT IN THE UPPER LEVEL JET WILL KEEP THE COLD AIR NORTH JAMES BAY
THROUGH THE WEEKEND. THE ONLY REAL ISSUE WITH THE LONG RANGE
FORECAST IS HOW QUICKLY THE UPPER LOW EJECTS INTO THE PLAINS.
TYPICALLY THE MODELS DO THIS TO QUICKLY. ALREADY THE MODELS HAVE
SLOWED DOWN NEARLY A DAY WITH THE COLD FRONT COMING THROUGH.

MY FORECAST HIGHS ARE BASED ON MY 1000/925 MB THICKNESS TOOL...WHICH
ARE LARGELY 2 TO 4 DEGREES ABOVE MOST OF THE MOS NUMBERS. GIVEN
CLIMO WOULD HAVE AN IMPACT ON THOSE NUMBER... HAVING HIGHS INCREASED
SEEMS LIKE A GOOD IDEA. THAT BEING SO WE MAY SEE OUR FIRST 90+ HIGHS
SAT...SUN AND MON.  I HAVE 90 ON SAT FOR NOW BUT I WOULD THINK IT IS
MORE THAN LIKELY SUNDAY AND MONDAY TOO.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z WEDNESDAY EVENING)
ISSUED AT 702 PM EDT TUE AUG 19 2014

I EXPECT VFR CONDITIONS TO RETURN TO ALL OF THE TAF SITES BEHIND
THE BAND OF CONVECTION MOVING INTO THE US-131 AREA NOW (23Z).
LATER TONIGHT HOWEVER GIVEN ALL THE RAIN THAT FELL AND THE LIGHT
WINDS EXPECTED I BELIEVE IFR FOG SHOULD DEVELOP AT ALL OF THAT TAF
SITES BY 09Z OR SO. THIS FOG SHOULD MIX OUT BY MID MORNING
WEDNESDAY. THEN VFR SHOULD ONCE AGAIN PREVAIL. I DO NOT EXPECT ANY
SIGNIFICANT CONVECTION AT THE TAF SITES WEDNESDAY.

&&

.MARINE...
ISSUED AT 330 PM EDT TUE AUG 19 2014

GENERALLY WEAK GRADIENT EXPECTED SO WINDS AND WAVES SHOULD REMAIN
BELOW SMALL CRAFT CRITERIA. HOWEVER AREAS OF FOG WILL BE A
POSSIBILITY AS HUMID AIR INTERACTS WITH THE COOLER LK MI WATERS.


&&

.HYDROLOGY...
ISSUED AT 330 PM EDT TUE AUG 19 2014

HEAVY RAINFALL RATES OF 1-2 INCHES PER HOUR THROUGH EARLY EVENING
WILL SUPPORT A THREAT OF URBAN AND SMALL STREAM FLOODING. SCATTERED
NATURE OF THESE HEAVIER AMOUNTS SHOULD LIMIT EXTENT OF RISES ON THE
LARGER RIVERS. THE PATTERN LATER IN THE WEEK SUPPORTS ADDITIONAL
HEAVY RAINFALL EVENTS SO RIVER FLOODING COULD BECOME MORE OF A
CONCERN BY THAT TIME.

&&

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

$$

SYNOPSIS...MEADE
SHORT TERM...MEADE
LONG TERM...WDM
AVIATION...WDM
HYDROLOGY...MEADE
MARINE...MEADE





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