Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 021929 RRA
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
328 PM EDT WED SEP 2 2015

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

.SYNOPSIS...
ISSUED AT 328 PM EDT WED SEP 2 2015

A WEAK COLD FRONT WILL MOVE SOUTH ACROSS LOWER MICHIGAN DURING THE
NEXT 36 HOURS AND CHANCE FOR SHOWERS AND THUNDERSTORMS WILL INCREASE
ACCORDINGLY. TEMPERATURES WILL BE A COUPLE OF DEGREES COOLER
THURSDAY AND FRIDAY DUE TO MORE CLOUDS AND SHOWERS. TEMPERATURES
WILL CLIMB BACK TO THE UPPER 80S BY THE END OF THE WEEKEND HOWEVER.


&&

.SHORT TERM...(THIS EVENING THROUGH FRIDAY NIGHT)
ISSUED AT 328 PM EDT WED SEP 2 2015

FORECAST CONCERNS DEAL WITH CONVECTIVE POTENTIAL DURING THE PERIOD.

THE SHORT WAVE THAT WAS GENERATING CONVECTION YESTERDAY OVER
NORTHEAST NEBRASKA AND THE EASTERN DAKOTAS HAS MIGRATED TO NORTHEAST
WISCONSIN WHERE IT IS GENERATING SHOWERS/STORMS...SOME OF WHICH HAVE
BEEN SEVERE. THIS WAVE IS PROGD TO MOVE OVER NORTHERN LOWER LATER
TONIGHT AND THURSDAY. CURRENTLY WE`RE SITTING ON 4000 J/KG SBCAPE
BUT NOT MUCH SHEAR. SCATTERED STORMS HAVE DEVELOPED OVER THE FAR
NORTHEAST CWA EARLY THIS AFTERNOON BUT HAVE BEEN WELL BELOW SEVERE
LEVELS. THE STRONGER STORMS OVER WISCONSIN HAVE BEEN IN A MORE
FAVORABLE SHEAR ENVIRONMENT WITH 40KTS NOTED ACROSS NRN WISCONSIN.

SHEAR VALUES ARE PROGD TO REMAIN 15KTS OR LESS THURSDAY ACROSS THE
CWA...SO ANY STORMS THAT DEVELOP LIKELY WON/T BE SEVERE. GIVEN THE
INCREASE IN CLOUD COVER EXPECTED...INSTABILITY WILL PROBABLY BE LESS
THAN TODAY TOO. THAT SAID...MORE FORCING IN THE WAY OF THE WEAK COLD
FRONT AND THE UPPER WAVE SHOULD LEAD TO MORE PCPN COVERAGE. WE/VE
INCREASED POPS TO LIKELY DURING THE AFTERNOON. ANOTHER THING TO
WATCH FOR WILL BE TO SEE IF ANY STORMS DEVELOP ON THE CONVERGENCE OF
THE EASTWARD MOVING LAKE BREEZE AS IT INTERACTS WITH THE NE WINDS
BEHIND THE FRONT. THIS COLD FRONT ISN/T THAT STRONG SO CONVERGENCE
MAY NOT BE SIGNIFICANT.

THE UPPER WAVE WILL BE SLOW TO DEPART SO CHANCES FOR SHOWERS AND
STORMS WILL LINGER INTO FRIDAY...ALTHOUGH CHANCES WILL BE LOWER THAN
ON THURSDAY.


.LONG TERM...(SATURDAY THROUGH WEDNESDAY)
ISSUED AT 328 PM EDT WED SEP 2 2015

THE OVERALL SYNOPTIC PATTERN CHANGES LITTLE ON SATURDAY AND SUNDAY
WITH VERY WARM AND HUMID CONDITIONS CONTINUING UNDER THE UPPER
RIDGE. ISOLATED SHOWERS AND STORMS STILL CANT BE RULED OUT
ESPECIALLY DURING PEAK HEATING DUE TO THE COMBINATION OF INSTABILITY
AND POTENTIAL FOR MESOSCALE LOW LEVEL CONVERGENCE ZONES.

THE RIDGE BEGINS TO GRADUALLY BREAK DOWN EARLY NEXT WEEK AND A SFC
COLD FRONT IS PROGGED TO COME THROUGH MONDAY AND MONDAY NIGHT.
HOWEVER THIS FRONT LOOKS WEAK WITH THE GOOD UPPER SUPPORT STILL WELL
OFF TO OUR NORTHWEST. GIVEN CONTINUED WEAK DEEP LAYER SHEAR BELIEVE
THAT THE SVR WEATHER THREAT ON LABOR DAY IS VERY LOW.  THE FRONT
SHOULD PROVIDE LESS HUMID CONDITIONS BEHIND IT HOWEVER FOR TUESDAY
AS IT HANGS UP JUST SOUTH AND EAST OF THE STATE.

PERHAPS A BETTER RISK OF ORGANIZED STRONG TO SEVERE STORMS WILL COME
NEXT WEDNESDAY WHEN DEEP LAYER SHEAR RAMPS UP AND MODELS SHOW THE
FRONT LIFTING BACK TO THE NORTH... WITH SOME SUGGESTION OF A WAVE
DEVELOPING/DEEPENING AS IT MOVES NORTHEAST FROM IOWA.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z THURSDAY AFTERNOON)
ISSUED AT 157 PM EDT WED SEP 2 2015

THE RISK OF SHOWERS AND TSTMS THIS AFTERNOON AND EVENING WILL BE
PRIMARILY NORTH AND EAST OF THE TERMINALS IN SW AND SC LWR MI.
EXPECT VFR CONDITIONS WITH A SCATTERED TO BROKEN CUMULUS DECK WITH
BASES AROUND 4000-5000 FT.

THE CHANCE OF SHOWERS AND TSTMS OVER SW LWR MI IS EXPECTED TO
INCREASE FROM NORTHWEST TO SOUTHEAST LATE TONIGHT AND THURSDAY.
WILL HAVE CONVECTION DEVELOPING 06Z-09Z AT MKG/GRR/AZO/BTL WHERE
CHANCES ARE HIGHEST... BUT WILL HOLD OFF AT LAN AND JXN UNTIL
AFTER DAYBREAK THURSDAY (STILL SOME FOG AT THESE SITES THOUGH).

WILL FCST PREDOMINATELY MVFR CONDITIONS IN THE SHOWERS AND
TSTMS... BUT IF STORMS PERSIST AND HEAVY RAIN
DEVELOPS... CONDITIONS COULD SETTLE INTO IFR FOR A TIME LATE
TONIGHT AND THURSDAY AT SOME OF THE TAF SITE.


&&

.MARINE...
ISSUED AT 328 PM EDT WED SEP 2 2015

OUTSIDE OF A FEW THUNDERSTORMS...MARINE CONDITIONS SHOULD BE QUIET
OVER THE NEXT 24 HRS. A LIGHT OFFSHORE WIND IS LIKELY TO DEVELOP
LATER THURSDAY AS A WEAK COLD FRONT DROPS SOUTH.

&&

.HYDROLOGY...
ISSUED AT 1147 AM EDT WED SEP 2 2015

CONFIDENCE IS INCREASING THAT OUR AREA WILL SEE AT LEAST SCATTERED
THUNDERSTORMS THURSDAY... OR PERHAPS A MORE EXPANSIVE CLUSTER. A
SLOW MOVING THUNDERSTORM OVER THE CITY OF MASON PRODUCED RAINFALL
RATES OF OVER 1 INCH PER HALF HOUR WEDNESDAY MORNING. WHILE BRIEF
HEAVY RAINFALL IS NOT MUCH OF A CONCERN IN MOST LOCATIONS... SOME
STORMS MAY PERSIST LOCALLY AND PRODUCE MORE SIGNIFICANT RAINFALL
TOTALS. THIS MAY CAUSE SOME FLOODING ISSUES IN URBAN AND POOR
DRAINAGE AREAS.

&&

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

$$

SYNOPSIS...04
SHORT TERM...04
LONG TERM...MEADE
AVIATION...MEADE
HYDROLOGY...CAS
MARINE...04


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