Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 260728
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
325 AM EDT TUE AUG 26 2014

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

.SYNOPSIS...
ISSUED AT 325 AM EDT TUE AUG 26 2014

WARM AND HUMID CONDITIONS WILL CONTINUE TODAY WITH A CHANCE OF
SHOWERS AND THUNDERSTORMS. THE BEST CHANCE OF THUNDERSTORMS WILL
COME LATE THIS MORNING AND AFTERNOON NEAR TO SOUTHEAST OF A LINE
FROM HOLLAND TO LANSING. A COOLER AND DRIER AIRMASS WILL MOVE IN
TONIGHT THROUGH THURSDAY. HOWEVER IT WILL TURN WARMER AND MORE
HUMID VERY LATE IN THE WEEK INTO NEXT WEEKEND WITH SCATTERED
SHOWERS AND THUNDERSTORMS.

&&

.SHORT TERM...(TODAY THROUGH THURSDAY)
ISSUED AT 325 AM EDT TUE AUG 26 2014

PRIMARY SHORT TERM FORECAST CONCERNS INVOLVE DETERMINING
CONVECTIVE POTENTIAL TODAY.

THE COLD FRONT WILL MOVE THROUGH OUR FCST AREA FROM NW TO SE THIS
MORNING AND AFTERNOON. SCATTERED SHOWERS AND THUNDERSTORMS WILL
DEVELOP ALONG AND JUST AHEAD OF THE FRONT MAINLY THIS AFTERNOON.
GIVEN THE FRONTAL TIMING THE BEST CHANCE FOR SCATTERED SHOWERS AND
STORMS WILL COME LATE THIS MORNING AND AFTERNOON OVER OUR SE FCST
AREA NEAR TO MAINLY JUST SE OF KGRR OVER TOWARD LAN... BTL... AND
JXN. THIS IS WHERE THERE IS POTENTIAL FOR SB CAPE VALUES TO REACH
2500-3000 J/KG BY EARLY AFTERNOON AS SUGGESTED BY 00Z NAM/GFS
GUIDANCE.

THE SEVERE WX THREAT TODAY IS FAIRLY LOW IN SPITE OF THE
POTENTIALLY MODERATE TO STRONG INSTABILITY MAINLY BECAUSE OF WEAK
DEEP LAYER SHEAR AND LACK OF STRONGER FORCING FROM THE FRONT. EVEN
SO CANNOT RULE OUT ISOLATE SEVERE STORMS OVER OUR SE FCST AREA
THIS AFTERNOON GIVEN POTENTIAL FOR STRONG INSTABILITY JUST AHEAD
OF THE FRONT.

A COOLER AND DRIER AIRMASS WILL ADVECT IN BEHIND THE FRONT TONIGHT
THROUGH MIDWEEK. HAVE TRENDED THE FORECAST DRY FOR TONIGHT AFTER
FROPA WITH DRY WX ANTICIPATED WEDNESDAY THROUGH THURSDAY AS A HIGH
PRESSURE RIDGE BUILDS IN. PCPN TIED TO THE NEXT SYSTEM APPROACHING
FROM THE WEST SHOULD HOLD OFF UNTIL THURSDAY NIGHT.


.LONG TERM...(THURSDAY NIGHT THROUGH MONDAY)
ISSUED AT 325 AM EDT TUE AUG 26 2014

OVERALL MODEL CONTINUITY IS FAIRLY GOOD TONIGHT BETWEEN THE GFS AND
THE ECMWF. THERE IS SOME DIVERGENCE IS SOLUTIONS OUT ON SUNDAY AND
MONDAY THOUGH. HAVE OPTED TO CONTINUE TO FOLLOW THE ECMWF HAS IT HAS
HAD MUCH BETTER RUN TO RUN CONSISTENCY LATELY. ALSO THE GFS HAS BEEN
CONVERGING TOWARDS ITS SOLUTIONS. FORECAST CONFIDENCE IS ONLY MEDIUM
THOUGH GIVEN THE DISPARITY BETWEEN THE MODELS.

THE LONG TERM STILL LOOKS LIKE A WET PERIOD AS A SURFACE BOUNDARY
WILL BE OSCILLATING THROUGH THE AREA ALMOST THE ENTIRE TIME. A WARM
FRONT SURGES NORTH THURSDAY NIGHT INTO FRIDAY...WITH THE ASSOCIATED
COOL FRONT STALLING OUT OVER THE AREA SATURDAY INTO SUNDAY. THE
ECMWF THEN PIVOTS A LOW THROUGH THE SOUTHERN GREAT LAKES INTO
MONDAY. HAVE MAINLY CHANCE POPS RIGHT THROUGH THE LONG TERM PERIOD
FOR SHOWERS AND STORMS. HEAVY RAINS ARE A DEFINITE POTENTIAL GIVEN
THE REPEATED ROUNDS OF CONVECTION. WPC QFF FOR THE LONG TERM IS ON
THE ORDER OF 1 TO 2 INCHES.

TEMPERATURES THROUGH THE PERIOD SHOULD BE SEASONABLE...IN THE UPPER
70S TO NEAR 80 ON MOST DAYS FOR HIGHS.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z TUESDAY NIGHT)
ISSUED AT 1222 AM EDT TUE AUG 26 2014

GOOD POTENTIAL EXISTS FOR IFR/LIFR FOG AND STRATUS TO DEVELOP
OVERNIGHT INTO EARLY TUESDAY MORNING. AIR MASS REMAINS VERY MOIST
WITH SFC DEW PTS AROUND 70 AND THE HIGH CLOUDINESS WHICH HAS BEEN
IN PLACE ALL EVENING IS NOW STARTING TO THIN WITH A BACK EDGE ALSO
MOVING EAST ACROSS LK MI. LOWEST CIGS/VSBYS EXPECTED TO BE FROM
ROUGHLY 10Z TO 13Z ALTHOUGH MKG MAY BE SPARED FROM IFR SINCE THE
SFC COLD FRONT WILL BE COMING THROUGH AROUND THAT TIME.

THE THREAT FOR ANY TSTMS WITH THE APPROACHING COLD FRONT IS MAINLY
EAST OF GRR AFTER 18Z TUESDAY AT LAN AND JXN. WINDS SHIFT TO THE
WEST/NORTHWEST WITH THE FROPA WHICH SENDS IN DRIER AIR AS WELL AS
STABLE MARINE AIR OFF LK MI. THAT SHOULD LEAD TO VFR CONDITIONS
DEVELOPING FROM WEST TO EAST BETWEEN 15Z AND 18Z.


&&

.MARINE...
ISSUED AT 325 AM EDT TUE AUG 26 2014

WINDS AND WAVES WILL BE RELATIVELY LIGHT TODAY THROUGH MIDWEEK.
HOWEVER PATCHY FOG WILL POSE A HAZARD TO MARINERS TODAY BEFORE A
DRIER AIRMASS MOVES IN TONIGHT THROUGH MIDWEEK.

&&

.HYDROLOGY...
ISSUED AT 1101 PM EDT MON AUG 25 2014

A FEW THUNDERSTORMS COULD REDEVELOP OVERNIGHT...AND THUNDERSTORMS
ARE ALSO POSSIBLE ON TUESDAY PRIMARILY EAST OF US-131. THESE
STORMS WILL REMAIN ISOLATED TO SCATTERED IN NATURE AND WIDESPREAD
HYDRO IMPACTS ARE NOT EXPECTED. STORMS COULD PRODUCE LOCALLY HEAVY
RAINFALL. DRIER AIR MOVES IN LATE TUESDAY INTO WEDNESDAY.

&&

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

$$

SYNOPSIS...LAURENS
SHORT TERM...LAURENS
LONG TERM...DUKE
AVIATION...MEADE
HYDROLOGY...EBW
MARINE...LAURENS







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