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241
FXUS63 KGRR 170328
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
1130 PM EDT TUE SEP 16 2014

LATEST UPDATE...
AVIATION

.SYNOPSIS...
ISSUED AT 312 PM EDT TUE SEP 16 2014

PLEASANT BUT COOL WEATHER WILL CONTINUE THROUGH THE MID WEEK
PERIOD.  DAYTIME HIGHS WILL BE IN THE 60S ON WEDNESDAY...THEN COOL
SLIGHTLY INTO THE UPPER 50S TO MID 60S ON THURSDAY.  NIGHTTIME LOWS
WILL BE IN THE UPPER 30S TO MID 40S...BUT IT WILL REMAIN WARMER NEAR
THE LAKE.  THERE COULD BE PATCHY FROST THURSDAY NIGHT OVER INLAND
AREAS AND NORTH OF I-94.

THE NEXT CHANCE OF RAIN SHOULD HOLD OFF UNTIL FRIDAY NIGHT THROUGH
SUNDAY AS A COLD FRONT COMES THROUGH.  TEMPERATURES SHOULD WARM INTO
THE 70S FRIDAY THROUGH SUNDAY...THEN COOL BACK DOWN INTO THE UPPER
50S TO MID 60S AGAIN FOR MONDAY AND TUESDAY.

&&

.SHORT TERM...(THIS EVENING THROUGH THURSDAY NIGHT)
ISSUED AT 312 PM EDT TUE SEP 16 2014

VERY FEW FORECAST CONCERNS THROUGH THE SHORT TERM.  PLEASANT BUT
COOL WEATHER WILL CONTINUE.

HIGH PRESSURE WILL REMAIN OVER THE REGION FOR THE NEXT 24 HOURS.
THIS WILL GIVE US MAINLY CLEAR SKIES.  I LOWERED TONIGHT/S LOW TEMPS
SLIGHTLY AS WINDS GO LIGHT...MOST AREAS WILL DROP TO AROUND 40 OR
THE LOWER 40S...BUT IT WILL STAY A BIT WARMER NEAR THE LAKE.  THERE
COULD BE SOME PATCHY FOG OVER THE NORTHERN CWA...BUT IT WILL BE MUCH
LESS THAN THIS MORNING WITH THE DRYING THAT HAS TAKEN PLACE TODAY.
SLIGHTLY WARMER WED WITH HIGHS IN THE 60S.

A WEAK COLD FRONT...NOW JUST DROPPING SOUTH OVER NORTHERN LAKE
SUPERIOR...WILL PRESS INTO THE CWA LATE WED AFTERNOON.  IT WILL
CONTINUE SOUTH AND WASH OUT OVER THE AREA WEDNESDAY NIGHT.  LIMITED
MOISTURE AND LIFT WITH THE FRONT...SO ONLY EXPECT TO SEE SOME LOW
CLOUDS FROM ROUGHLY MIDNIGHT WEDNESDAY NIGHT TO NOON THURSDAY.

SKIES WILL CLEAR THURSDAY AFTERNOON...BUT WE WILL SEE DECENT COLD
ADVECTION BEHIND THE FRONT WITH H8 TEMPS DROPPING TO AROUND +4C.
HAVE LOWERED MAX TEMPS FOR THURSDAY WITH HIGHS ONLY IN THE UPPER 50S
TO MID 60S.  ALSO LOWERED MINS SLIGHTLY FOR THURSDAY NIGHT.  THERE
WILL BE PATCHY FROST POSSIBLE FOR INLAND AREAS.  BUT AT THIS POINT
IT DOES NOT APPEAR TO BE TOO LASTING OR WIDESPREAD TO WARRANT
HEADLINES.

.LONG TERM...(FRIDAY THROUGH TUESDAY)
ISSUED AT 312 PM EDT TUE SEP 16 2014

NEXT SIGNIFICANT WEATHER SYSTEM WILL BRING SHOWERS AND A FEW STRONG
THUNDERSTORMS TO THE AREA SATURDAY NIGHT. WARMER TEMPERATURES IN
THE 70S STILL LOOKING GOOD FOR FRIDAY AND SATURDAY AHEAD OF THE
FRONT WITH A RETURN TO BELOW NORMAL TEMPERATURES MONDAY AND TUESDAY.

ECMWF/GFS/FIM ALL IN GOOD AGREEMENT WITH THE GROSS DETAILS OF NEXT
SYSTEM. SURFACE LOW CENTER WILL MOVE ALONG CANADIAN BORDER AND OVER
LAKE SUPERIOR. MAY SEE SOME SHOWER ACTIVITY NORTH OF A MUSKEGON - MT
PLEASANT LINE SATURDAY MORNING AS LEADING EDGE OF WARMER AIR PUSHES
INTO THE REGION...BUT MAIN PRECIPITATION CHANCE WILL BE SATURDAY
NIGHT WITH THE COLD FRONTAL PASSAGE. OVERALL... EXPECT AVERAGE QPF
VALUES TO FALL BETWEEN /0.25 - 0.75/ INCHES.

DETAIL WISE THERE HAS BEEN CONSIDERABLE RUN-TO-RUN DIFFERENCES WITH
AMPLITUDE OF DIGGER UPPER TROUGH. 00Z ECMWF WAS TRENDING DEEPER /
SLOWER AS DID THE 12Z GFS BUT NOW THE 12Z ECMWF IS WEAKER / FASTER
SIMILAR TO 00Z FIM. MY GUESS IS THAT IT WILL END UP BEING MORE
PROGRESSIVE THAN NOT AT THIS POINT WHICH WILL BRING BEST COLD
FRONTAL POPS SATURDAY EVENING.

COLD FRONTAL SHOWERS WILL BE SUPPORTED BOTH BY LOW LEVEL MOIST FLUX
FRONTAL CONVERGENCE ASSOCIATED WITH 30 KT LOW LEVEL JET AND BY UPPER
DIVERGENCE ASSOCIATED WITH DIGGING H5-H3 SHORTWAVE TROUGH AND
ASSOCIATED ROTATIONAL COMPONENT OF THE F-GEN VECTOR. THE MAGNITUDE
OF WHICH WILL DEPEND ON HOW MUCH THE LEADING UPPER JETLET DIGS INTO
THE UPPER SHORTWAVE SATURDAY. A FEW STRONG STORMS ARE ALSO FAVORED
WITH CAPE VALUES OF 500 J/KG AND 0-6KM BULK SHEAR APPROACHING 40KTS.

LAKE EFFECT SHOWERS WOULD BE POSSIBLE SUNDAY INTO MONDAY WITH DEEP
CYCLONIC FLOW / CONVERGENCE AND H85 TEMPS NEAR ZERO CELSIUS IF THE
DEEPER SOLUTIONS WERE TO PLAY OUT.

&&

.AVIATION...(FOR THE 060Z TAFS THROUGH 06Z THURSDAY)
ISSUED AT 1130 PM EDT TUE SEP 16 2014

VFR CONDITIONS WILL CONTINUE THROUGH 06Z THURSDAY. SKIES WILL REMAIN
CLEAR OVERNIGHT. SOME SCT FAIR WX CUMULUS WILL DEVELOP LATE
WEDNESDAY MORNING THROUGH WEDNESDAY AFTERNOON. WIND SPEEDS WILL
REMAIN AOB 10 KTS THROUGH WEDNESDAY EVENING.

&&

.MARINE...
ISSUED AT 312 PM EDT TUE SEP 16 2014

FAIRLY QUIET ON THE LAKE THROUGH MOST OF THE SHORT TERM.  HOWEVER
THERE WILL BE BRISK NORTH WINDS BEHIND THE COLD FRONT WEDNESDAY
NIGHT.  THIS COULD PUSH WAVES TO SMALL CRAFT ADVISORY LEVELS LATE
WEDNESDAY NIGHT INTO THURSDAY MORNING AROUND THE POINTS REGION.  THE
WINDS WILL GRADUALLY TURN MORE NE/OFFSHORE BY LATE THURSDAY MORNING
AND WAVES SHOULD DIMINISH ONCE AGAIN.


&&

.HYDROLOGY...
ISSUED AT 312 PM EDT TUE SEP 16 2014

NO HYDRO ISSUES.  NO RAIN IS ANTICIPATED UNTIL FRIDAY NIGHT OR
SATURDAY.

&&

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

$$

SYNOPSIS...JK
SHORT TERM...JK
LONG TERM...COBB
AVIATION...LAURENS
HYDROLOGY...JK
MARINE...JK










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