Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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000
FXUS63 KGRR 250725
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
325 AM EDT MON AUG 25 2014

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

.SYNOPSIS...
ISSUED AT 325 AM EDT MON AUG 25 2014

WARM AND HUMID CONDITIONS WILL CONTINUE TODAY THROUGH TUESDAY WITH
SCATTERED SHOWERS AND THUNDERSTORMS. THUNDERSTORMS THIS AFTERNOON
THROUGH TUESDAY MAY CONTAIN LOCALLY HEAVY RAINFALL. DRY AND COOLER
WEATHER WILL BRIEFLY RETURN WEDNESDAY FOLLOWED BY WARMER AND MORE
HUMID WEATHER WITH ANOTHER CHANCE OF SHOWERS AND STORMS LATE IN
THE WEEK.

&&

.SHORT TERM...(TODAY THROUGH WEDNESDAY)
ISSUED AT 325 AM EDT MON AUG 25 2014

IT WILL BE VERY WARM AND HUMID TODAY WITH MAX TEMPS REACHING WELL
INTO THE 80S AND DEW POINT VALUES UP INTO THE UPPER 60S TO LOWER
70S. SCATTERED SHOWERS AND THUNDERSTORMS WILL DEVELOP LATER TODAY
AS INSTABILITY BUILDS AND SB CAPE VALUES POTENTIALLY REACH AROUND
2000-2500 J/KG NEAR TO EAST OF US-131 THIS AFTERNOON.

SEVERE WX IS UNLIKELY MAINLY DUE TO WEAK DEEP LAYER SHEAR BUT AN
ISOLATED SEVERE STORM CANNOT BE RULED OUT THIS AFTERNOON AND EARLY
EVENING WHEN INSTABILITY WILL BE MAXIMIZED. ANY STORMS THAT DO
DEVELOP COULD PRODUCE LOCALLY RAINFALL WITH PRECIPITABLE WATER
VALUES UP IN THE 1.75 TO 2 INCH RANGE TODAY.

SCATTERED SHOWERS AND PERHAPS A FEW STORMS WILL CONTINUE INTO THIS
EVENING. THEN THE COLD FRONT WILL BRING SCATTERED SHOWERS AND
THUNDERSTORMS ON TUESDAY. THE BEST CHANCE FOR A FEW STRONG TO
POTENTIALLY SEVERE STORMS TUESDAY WOULD BE IN THE AFTERNOON OVER OUR
SE FCST AREA WHEN SB CAPE VALUES WILL POTENTIALLY REACH AROUND 3000
J/KG.

IT HAS BEEN NOTED THAT OVERALL SHORT TO MEDIUM RANGE GUIDANCE
TRENDS ARE BRINGING THE COLD FRONT THROUGH FASTER. THEREFORE WE
HAVE TRIMMED BACK POPS SIGNIFICANTLY FOR TUESDAY NIGHT AND ARE
KEEPING LINGERING LOW POPS CONFINED TO OUR SOUTHERN FORECAST AREA.
DRY WEATHER IS NOW ANTICIPATED WEDNESDAY WITH THE HIGH PRESSURE RIDGE
IN PLACE OVER THE NORTHERN GREAT LAKES REGION.

.LONG TERM...(WEDNESDAY NIGHT THROUGH SUNDAY)
ISSUED AT 325 AM EDT MON AUG 25 2014

THE LAST COUPLE NIGHTS HAVE SEEN THE GFS GUIDANCE TREND TOWARDS THE
ECMWF IN TERMS OF THE EVOLUTION OF THE PATTERN. TONIGHT...HAVE
THEREFORE FOLLOWED THE LEAD OF THE ECMWF THROUGH THE LONG TERM
FORECAST.

THE LONG TERM LOOKS TO FEATURE A DECENT ABOUT OF RAINFALL WITH A
BOUNDARY OSCILLATING THROUGH THE REGION AND NEAR NORMAL TEMPERATURES.

AS FOR THE DETAILS...THE PERIOD LOOKS TO START OFF DRY WITH SURFACE
HIGH PRESSURE SAGGING INTO THE AREA FROM THE NORTH WEDNESDAY NIGHT.
FEEL THURSDAY WILL LIKELY BE DRY AS WELL...BUT BLENDED IN WITH
NEIGHBORING OFFICES AND HAVE A 20 PCT CHANCE FOR SHOWERS/STORMS IN
THE FAR WEST.

CHANCES FOR SHOWERS AND STORMS THEN LOOK TO BE POSSIBLE IN THE
REMAINDER OF THE FORECAST PERIOD...THURSDAY NIGHT THROUGH SUNDAY.
MOISTURE COMES SURGING BACK IN THURSDAY NIGHT ESPECIALLY ALOFT. THE
ECMWF HAS A WARM FRONT OR A STATIONARY BOUNDARY NEARBY FRI-SUN. HAVE
CHANCE POPS ESSENTIALLY BLANKETED THROUGHOUT THIS PERIOD OF THE
FORECAST. THE DAYS 4-5 AND 6-7 QPF PROGS FROM WPC ALSO BEAR THIS
OUT. THEY SHOW RAINFALL TOTALS AROUND AN INCH FOR MOST AREAS...WHICH
SEEMS REASONABLE.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z MONDAY NIGHT)
ISSUED AT 1120 PM EDT SUN AUG 24 2014

IT WOULD SEEM FOG IS BECOMING LESS LIKELY OVERNIGHT. AS I WROTE
FOR THE 00Z TAF SET...THE WINDS IN THE BOUNDARY LAYER OF BETWEEN
15 AND 25 KNOTS ARE ENOUGH TO KEEP SURFACE FOG FROM BECOMING MUCH
OF AN ISSUE TONIGHT. INSTEAD THE IR-FOG LOOP SHOWS PATCHY LOW CLOUDS
(MVFR CIGS) DEVELOPING NEAR AND SOUTH OF I-96. AS THE AIR
CONTINUES TO COOL OVERNIGHT THE LOW CLOUDS SHOULD BECOME MORE
EXTENSIVE AND CIGS SHOULD LOWER SOME. SO I HAVE ONLY MVFR CIGS/VSBY
AT ALL TAF SITES.

THE CONVECTION FOR MONDAY STILL SEEMS POSSIBLE. THE LATEST VERSION
OF THE RAP MODEL AND THE NAM12 SHOW LATE MORNING AND AFTERNOON
CONVECTION. SO...I NOW HAVE VCTS AFTER 15Z FOR THAT. I WOULD
EXPECT ONCE THE SUN SETS MONDAY EVENING THE CONVECTION WILL BE
DONE. THERE SHOULD BE ENOUGH WIND TOMORROW NIGHT TO KEEP FOG FROM
BECOMING AN ISSUE.


&&

.MARINE...
ISSUED AT 325 AM EDT MON AUG 25 2014

MINIMAL WIND AND WAVE ACTION IS ANTICIPATED TODAY THROUGH TONIGHT
INTO TUESDAY. HOWEVER PATCHY FOG WILL POSE A HAZARD TO MARINERS.

&&

.HYDROLOGY...
ISSUED AT 1104 AM EDT SUN AUG 24 2014

BEST CHANCE FOR SIGNIFICANT RAINFALL WOULD BE MONDAY NIGHT THROUGH
WEDNESDAY WITH A SLOW MOVING COLD FRONT. THIS IS NOT A GUARANTEE
AS THE LLJ IS FORECAST TO BE QUITE WEAK. NEVERTHELESS...A VERY
MOIST ATMOSPHERE COMBINED WITH FORCING VIA THE COLD FRONT AND SLOW
CELL MOVEMENT COULD RESULT IN SOME SIGNIFICANT RAINFALL IF STORMS
DEVELOP OVER OUR AREA. PW VALUES WILL LIKELY BE AROUND 1.75"
MONDAY NIGHT AND TUESDAY. MODEL GUIDANCE IS MIXED REGARDING HOW
LONG THE FRONT MAY HANG UP...SO IT IS UNCLEAR WHEN THE THREAT FOR
SIGNIFICANT RAINFALL WOULD END.

&&

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

$$

SYNOPSIS...LAURENS
SHORT TERM...LAURENS
LONG TERM...DUKE
AVIATION...WDM
HYDROLOGY...HOVING
MARINE...LAURENS









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