Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 041919
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
318 PM EDT TUE AUG 4 2015

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

.SYNOPSIS...
ISSUED AT 318 PM EDT TUE AUG 4 2015

ONCE SHOWERS ACROSS INTERIOR PORTIONS OF CENTRAL LOWER DIMINISH BY
THIS EVENING...THE AREA IS LOOKING AT A COUPLE OF DRY DAYS AS HIGH
PRESSURE MOVES OVER THE AREA. TEMPERATURES WILL BE COMFORTABLE...YET
A LITTLE BELOW AVERAGE FOR THIS TIME OF THE YEAR.

THE NEXT CHANCE OF RAIN WILL COME IN BEGINNING ON FRIDAY AND LAST
INTO THE WEEKEND AS THE NEXT SYSTEM POISED TO AFFECT THE AREA WILL
MOVE IN.

&&

.SHORT TERM...(THIS EVENING THROUGH THURSDAY NIGHT)
ISSUED AT 318 PM EDT TUE AUG 4 2015

FCST CHALLENGES/CONCERNS ARE MINIMAL WITH THIS FCST PACKAGE AS THE
AREA TENDS TO DRY OUT DURING THE PERIOD WITH HIGH PRESSURE MOVING
OVERHEAD.

A FEW SPOTTY SHOWERS HAVE DEVELOPED THIS AFTERNOON AS EXPECTED
ACROSS THE NE PORTION OF THE CWFA. THIS IS WHERE THE CYCLONIC FLOW
ALOFT REMAINS AS OF THIS AFTERNOON. THE SHOWERS WILL DISSIPATE
QUICKLY BY EARLY THIS EVENING AS WE LOSE THE HEATING OF THE DAY AND
AS THE UPPER JET CORE LIFTS NORTH OF THE AREA.

WE ARE EXPECTING NO DIURNAL SHOWERS TO POP ACROSS THE CWFA DURING
THE DAY ON WED. THE JET CORE MOVING NORTH AND RIDGING BUILDING IN
WILL PROVIDE ENOUGH SUBSIDENCE TO LIMIT VERTICAL GROWTH FOR ANY
CUMULUS DEVELOPMENT. TEMPS SHOULD BE CLOSE TO TODAY/S VALUES WITH
NOT MUCH CHANGE IN H850 VALUES.

WE ARE CONTINUING WITH A MAINLY DRY FCST FOR WED NIGHT THROUGH THU.
THE MODEL CONSENSUS YESTERDAY OF KEEPING THE NRN AND SRN STREAMS
UNPHASED IS NOW BEING ADVERTISED BY ALL OF THE MODELS. THIS WILL
KEEP LOWER MICHIGAN DRY IN BETWEEN BOTH SYSTEMS. TEMPS WILL MODERATE
SLIGHTLY WITH MORE LOCATIONS SEEING TEMPS IN THE LOWER 80S. IT LOOKS
LIKE THE NEXT CHC OF RAIN WITH THE NEXT SYSTEM WILL COME IN BEYOND
THE SHORT TERM PERIOD.

.LONG TERM...(FRIDAY THROUGH TUESDAY)
ISSUED AT 318 PM EDT TUE AUG 4 2015

UPCOMING WEEKEND LOOKS FAIR WITH A CHANCE OF SHOWERS AT ABOUT
ANYTIME AND A FEW ISOLATED A STRONG THUNDERSTORMS EITHER OF
SATURDAY OR SUNDAY AFTERNOON...BUT NOT SUBSTANTIAL RAINFALL
EXPECTED. TEMPERATURES LOOKS SEASONABLE WITH HIGHS AROUND 80 OR
BETTER WITH LOWS IN THE MID 60S AS DEWPOINTS SLOWLY INCREASE IN
SATURDAY NIGHT.

OVERALL PATTERN OF UPPER TROUGH OVER THE EAST WITH AN UPSTREAM RIDGE
OVER CENTRAL WEST AND A PACIFIC TROUGH JUST OFF THE WEST COAST WILL
CONTINUE ALTHOUGH THE VORTEX OVER HUDSON BAY WEAKENS CONSIDERABLY
RESULTING IN A MORE ZONAL FLOW ACROSS THE UPPER MIDWEST. THIS WILL
RESULT IN A GRADUAL WARMING TO SEASONAL AUGUST TEMPERATURES AND
HUMIDITY.

WHILE MEDIUM RANGE GUIDANCE GENERALLY AGREES WITH LARGE SCALE
DETAILS...SIGNIFICANT DIFFERENCE DEVELOP EARLY IN THE WEEKEND
CONCERNING SHORTWAVE INTERACTIONS AND RESULTING SURFACE FRONTAL
POSITIONS.  GFS/ECM/FIM ALL SHOW WEAKENING SHORTWAVE MOVING ESE INTO
AREA FRIDAY NIGHT WITH WEAK SURFACE WARM FRONT.  LIKELY TO SEE
REMAINS OF DYING MCS APPROACH ON AREA FRIDAY WITH INCREASING
HIGH/MID CLOUDS BUT BEST LIFT STAY NORTH SO JUST A FEW SHOWERS
POSSIBLE SUPPORTED BY WAA LIFT AND MOIST FLUX CONVERGENCE ON NOSE OF
MODEST WSW LOW LEVEL JET.

A SECOND SHORTWAVE APPROACHES ON SUNDAY WITH ECM/FIM TRACK ACROSS MI
WITH A BIT OF FRONTOGENESIS A DEVELOPING COLD FRONT BEGINS TO MOVE
NORTH TO SOUTH. MODERATE INSTABILITY AND SHEAR COULD SUPPORT SOME
ISOLATED STRONG STORMS ALONG AND AHEAD OF THE FRONT SUNDAY. THE GFS
HOWEVER IS FURTHER NORTH WITH THIS SHORTWAVE AND INSTEAD ITS
SOLUTION HAS A SUBSEQUENT 3RD SHORTWAVE DEVELOP AND PUSH FRONT INTO
THE AREA LATE MONDAY INTO TUESDAY.

LOOKING FARTHER INTO NEXT WEEK...THE STORY LOOKS SIMILAR WITH
CONTINUED DRY WEATHER PATTERN AND ANOTHER SEASONABLY COOL AND DRY
CANADIAN AIRMASS AS UPPER TROUGH DEEPENS AGAIN BY MIDWEEK. THAT
LOOKS TO BE FOLLOWED BY ANOTHER SHOT OF WARM AIR AND POTENTIAL WET
WEATHER AS PERHAPS SOME STRONGER PACIFIC SHORTWAVES CRASH THE
WESTERN RIDGE...RESULTING IN A MORE PROGRESSIVE PATTERN.

THIS WILL ALL DEPEND SOMEWHAT ON THE PURGES OF SEVERAL TROPICAL
PACIFIC SYSTEMS AND THEIR INTERACTION WITH WESTERLIES.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z WEDNESDAY MORNING)
ISSUED AT 130 PM EDT TUE AUG 4 2015

VFR CONDITIONS WITH AREAS OF BKN060 THROUGH THIS AFTERNOON. CIGS AND
VIS UNLIMITED (CAVU) FROM THIS EVENING THROUGH WEDNESDAY. LAKE
BREEZE WIND GUSTS OF 25KTS ALONG ROUTE 131 WILL CONTINUE TO SLOWLY
PUSH FURTHER EAST (INLAND) AND THEN WILL DIMINISH TOWARDS SUNSET.
EXPECT VERY LIGHT NORTHWEST OR LIGHT AND VARIABLE WINDS OVERNIGHT
INTO EARLY AFTERNOON WEDNESDAY. ALSO COULD BE SOME SHALLOW
LAKE...RIVER...OR VALLEY FOG AROUND DAYBREAK WEDNESDAY.

OUTLOOK...VFR WITH LIGHT WINDS INTO THURSDAY...CHANCE OF SHOWERS
WITH PATCHY MVFR FRIDAY NIGHT.

&&

.MARINE...
ISSUED AT 318 PM EDT TUE AUG 4 2015

LINGERING SLIGHTLY GUSTY WINDS AND WAVES OF 1 TO 3 FEET WILL
DIMINISH THIS EVENING AND TONIGHT AS HIGH PRESSURE BUILDS OVERHEAD
AND THE GRADIENT BECOMES LIGHT. WE SHOULD SEE WINDS GENERALLY REMAIN
AT OR BELOW 15 KNOTS THEN THROUGH THE REMAINDER OF THE WORK WEEK.
THE FLOW WILL BECOME OFFSHORE BY THU...SO WATER TEMPERATURES WILL
LIKELY DROP A BIT WITH UPWELLING POTENTIALLY OCCURRING.

&&

.HYDROLOGY...
ISSUED AT 1233 PM EDT TUE AUG 4 2015

NO FLOODING ISSUES ARE EXPECTED AS A RELATIVELY DRY PATTERN SETS
UP OVER LOWER MICHIGAN. SOME SHOWERS WILL BE POSSIBLE OFF AND
ON THROUGH THE WEEKEND...BUT NO SIGNIFICANT RAINFALL EVENTS ARE
EXPECTED AT THIS TIME.

&&

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

$$

SYNOPSIS...NJJ
SHORT TERM...NJJ
LONG TERM...COBB
AVIATION...COBB
HYDROLOGY...MACZKO
MARINE...NJJ


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