Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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000
FXUS63 KGRR 162319
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
719 PM EDT SAT AUG 16 2014

LATEST UPDATE...
AVIATION

.SYNOPSIS...
ISSUED AT 327 PM EDT SAT AUG 16 2014

A COLD FRONT WILL SLIP SOUTH THROUGH THE STATE TONIGHT AND BE NEAR
THE MICHIGAN INDIANA BORDER BY DAYBREAK ON SUNDAY. SCATTERED SHOWERS
AND A FEW THUNDERSTORMS WILL BE POSSIBLE AS THE FRONT TRAVERSES THE
AREA. WIDESPREAD RAINFALL IS NOT EXPECTED. SUNDAY INTO MONDAY WILL
BE MAINLY DRY AS A LOW PRESSURE SYSTEM PASS OFF TO THE SOUTH OF THE
GREAT LAKES THROUGH THE OHIO VALLEY. THERE WILL BE CLOUDS AROUND
HOWEVER WHICH WILL KEEP HIGHS MAINLY IN THE 70S FOR SUNDAY AND
MONDAY. THE REMAINDER OF THE WORK WEEK WILL FEATURE A WARMING TREND
WITH HIGHS IN THE 80S AND CHANCES FOR SHOWERS AND STORMS EACH DAY.

&&

.SHORT TERM...(THIS EVENING THROUGH MONDAY NIGHT)
ISSUED AT 327 PM EDT SAT AUG 16 2014

MAIN FOCUS IN THE SHORT TERM IS ON CONVECTIVE TRENDS THIS EVENING
AND TONIGHT. WE HAVE HAD A HARD TIME DEVELOPING ANY INSTABILITY
TODAY WITH SURFACE BASED CAPE VALUES ONLY ON THE ORDER OF 500 J/KG
ACROSS CENTRAL LOWER MI. A BREEZY WEST WIND OFF THE COOLER LAKE IS
NOT HELPING EITHER. SO...PRECIP THUS FAR HAS BEEN FAIRLY
LIGHT/SCATTERED. EXPECT SCATTERED SHOWERS AND A FEW STORMS TO
PROGRESS SOUTH TONIGHT WITH A GRADUAL DECREASE IN COVERAGE AND
INTENSITY AFTER DARK.

FEEL WE WILL BE MAINLY DRY FROM SUNDAY THROUGH MONDAY AS THE SYSTEM
OFF TO OUR SOUTH MOVES ACROSS THE OHIO VALLEY. WE SHOULD BE JUST FAR
ENOUGH NORTH OF THIS SYSTEM TO MAINLY SEE CLOUD COVER ASSOCIATED
WITH IT. HAVE VERY LOW POPS 20/30 PCT CHANCE ACROSS THE I94 ROW OF
COUNTIES THOUGH TO MATCH UP WITH NEIGHBORING OFFICES. ANTICIPATING
DRY THOUGH.

MONDAY NIGHT A SYSTEM FROM THE NORTHERN PLAINS WILL APPROACH WITH
THE POTENTIAL FOR SOME SHOWERS AND STORMS MOVING IN OVERNIGHT. WE
HAVE A 30 PCT CHANCE FOR PRECIP AT THIS POINT.

.LONG TERM...(TUESDAY THROUGH SATURDAY)
ISSUED AT 327 PM EDT SAT AUG 16 2014

THE EXTENDED PERIOD LOOKS SEASONABLY WARM WITH SEVERAL OPPORTUNITIES
FOR SHOWERS AND THUNDERSTORMS.

THE BEST CHANCE OF PCPN WILL COME AT THE BEGINNING OF THE PERIOD. AN
UPPER TROUGH IS GOING TO MOVE ACROSS THE GREAT LAKES TUESDAY. THERE
IS GOOD AGREEMENT AMONG THE MODELS ON BRINGING THE SFC LOW ACROSS
LOWER MICHIGAN. LI/S NEAR -3C AND 1K J/KG SBCAPE SHOULD RESULT IN
SOME STORMS. SHEAR VALUES ARE LOW...AROUND 20 KTS WHICH SHOULD
RESULT IN NON-SEVERE STORMS. HOWEVER THE NAM SHOWS SHEAR NEAR 50 KTS
OVER NRN INDIANA. THE OTHER MODELS ARE NOT AS BULLISH WITH
SHEAR...BUT DO SHOW HIGHER VALUES SOUTH OF THE CWA. SO WE/LL KEEP AN
EYE ON THAT.

THE LOW IS SLOW TO MOVE THROUGH WHICH WILL MEAN AN EXTENDED CHANCE
OF TSRA INTO WEDNESDAY. AFTER THAT...A PLAINS LOW IS PROGD TO PUSH A
WARM FRONT NORTH INTO THE WESTERN GREAT LAKES. WITH A SFC HIGH
SITTING OVER QUEBEC DURING THE LAST HALF OF THE WEEK GENERATING A
NORTH EAST WIND FLOW...THERE IS LESS CONFIDENCE IN SEEING PCPN FROM
THAT WARM FRONT MOVE INTO LOWER MICHIGAN AND THUS WE HAVE LOWER
POPS.

OVERALL....WE/LL SEE HIGHS NEAR TO SLIGHTLY ABOVE NORMAL WITH
CHANCES FOR PCPN THROUGH LATE WEEK.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z SUNDAY EVENING)
ISSUED AT 719 PM EDT SAT AUG 16 2014

IT WOULD SEEM IFR CONDITIONS WILL OVERSPREAD THE TAF SITES BTW 03Z
AND 06Z AS THE FRONTAL BAND AREA OF LOW CLOUDS...ALREADY PRESENT
OVER CENTRAL LOWER MICHIGAN MOVES SOUTH INTO THE I-96 TO I-94
AREA. TO COMPLICATE THINGS...A WAVE ON THE FRONT MAY CAUSED AN
ENHANCED AREA OF SHOWERS TO MOVE THROUGH THE TAF SITES IN THE 03Z
TO 09Z TIME FRAME. I PUT VCSH FOR THIS NOW AS IT IS QUESTIONABLE
JUST WHERE THESE SHOWERS WILL GO TONIGHT. I DID PUT A SHOWER INTO
THE MKG TAF AT 01Z THROUGH AS AN AREA OF SHOWERS SEEMS TO BE
HOLDING TOGETHER ENOUGH TO REACH THE MKG TAF SITE BY 01Z. IF THESE
SHOWERS DO MOVE THROUGH THE TAF SITES TONIGHT THERE MAY BE LIFR
FOG BY 10Z-12Z. WE WILL HAVE TO MONITOR THIS... FOR NOW I HAVE
1-2SM VSBY IN MIST. ONCE THE FRONT MOVES A LITTLE FARTHER SOUTH
SKIES SHOULD CLEAR ACROSS THE TAF SITES BY 18Z OR SO SUNDAY.

&&

.MARINE...
ISSUED AT 327 PM EDT SAT AUG 16 2014

HAVE OPTED TO KEEP AREAS OF FOG GOING IN THE NEARSHORE AND NOT HOIST
A MARINE DENSE FOG ADVISORY. THE DENSE FOG AT MUSKEGON STILL LOOKS
TO BE QUITE LOCALIZED. THE GRAND HAVEN...MONA LAKE AND PENTWATER
CAMS ALL SHOW DECENT VISIBILITY. WE WILL MONITOR THE CAMS THIS
EVENING AND INTO TONIGHT. IF THE FOG EXPANDS A MARINE DENSE FOG
ADVISORY MAY BE NEEDED. THE DRIER AIR ADVECTION IN FROM THE NORTH
AND NORTHEAST SHOULD EASE THE FOG THREAT LATE TONIGHT AND SUNDAY
MORNING.

WAVES HAVE REMAINED IN THE 1-3 FOOT RANGE ALL DAY. THE GRADIENT
BECOMES BAGGY THIS EVENING FOR A TIME SO NOT SWIM/BOATING ISSUES
ANTICIPATED THROUGH SUNSET. NORTHERLY WINDS WILL RAMP UP TONIGHT AND
SHIFT NORTHEAST. THE FRONT IS ALREADY MAKING ITS WAS SOUTH THROUGH
THE NORTHERN QUARTER OF LAKE MI. GIVEN THE SLIGHT OFFSHORE COMPONENT
THINKING THE HIGHER WAVES WILL REMAIN OUT OF THE NEARSHORE ZONES.
SO...NO MARINE ISSUES THE REMAINDER OF THE WEEKEND ONCE WE GET BY
THE PATCHY FOG TONIGHT WHICH IS OCCURRING DUE TO THE COLD WATER/HIGH
DEW POINT COMBINATION.


&&

.HYDROLOGY...
ISSUED AT 327 PM EDT SAT AUG 16 2014

HYDRO ISSUES ARE NOT ANTICIPATED THE NEXT FEW DAYS. RAINFALL SO FAR
TODAY ACROSS THE GRR FORECAST AREA HAS BEEN SPOTTY AND SOMEWHAT
LIGHT AS EXPECTED ACROSS CENTRAL LOWER. SCATTERED SHOWERS AND A FEW
EMBEDDED STORMS WILL SLIDE SOUTH THROUGH THE AREA TONIGHT. WHILE
SOME LOCALLY HEAVY RAIN MAY BE POSSIBLE THIS EVENING...NOT EXPECTING
ANYTHING WIDESPREAD. RIVERS WILL EASILY BE ABLE TO ABSORB TONIGHT/S
SCATTERED RAIN WITHOUT ANY PROBLEMS.

&&

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

$$

SYNOPSIS...DUKE
SHORT TERM...DUKE
LONG TERM...93
AVIATION...WDM
HYDROLOGY...DUKE
MARINE...DUKE






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