Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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155
FXUS63 KGRR 201754
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
154 PM EDT WED MAY 20 2015

LATEST UPDATE...
AVIATION

.SYNOPSIS...
ISSUED AT 326 AM EDT WED MAY 20 2015

EXPECT BELOW NORMAL TEMPERATURES THROUGH AT LEAST SATURDAY AS A
SERIES OF CANADIAN COLD FRONTS COME THROUGH THE AREA. THE NEXT
COLD FRONT COMES THROUGH EARLY FRIDAY MORNING AND THAT WILL BE
PRECEDED BY A FEW LIGHT RAIN SHOWERS THURSDAY EVENING. A WARM UP
IS EXPECTED TOWARD MEMORIAL DAY. SHOWERS AND THUNDERSTORMS ARE
POSSIBLE SUNDAY INTO TUESDAY.

&&

.UPDATE...
ISSUED AT 1208 PM EDT WED MAY 20 2015

UPSTREAM SHORTWAVE SLIDING EAST FROM THE PLAINS WILL SPREAD CLOUDS
INTO SOUTHWEST LOWER MICHIGAN THIS AFTERNOON AND EVENING. SKIES IN
MOST AREAS WILL TURN MOSTLY CLOUDY WITH TIME. DILEMMA IS WHETHER
OR NOT WE WILL SEE PRECIPITATION INTO THE SOUTHERN PORTION OF THE
STATE. MORNING RUNS OF THE HRRR ARE TRYING TO BRING LIGHT RETURNS
INTO ABOUT THE SOUTHERN HALF OF THE GRR FORECAST AREA THIS EVENING.
AT THIS POINT HAVE DECIDED TO KEEP THE DRY FORECAST GOING AS WE
BELIEVE THE DRY AIR IS GOING TO WIN OUT. PRECIP UPSTREAM IS LIGHT
AND MAINLY FALLING OUT OF A MID DECK ON THE LEADING EDGE. IF THE
SYSTEM OVERPERFORMS IT WOULD BE IN THE FORM OF SPRINKLES ALONG
I-94 BETWEEN 800PM AND MIDNIGHT OR SO.

&&

.SHORT TERM...(TODAY THROUGH FRIDAY)
ISSUED AT 326 AM EDT WED MAY 20 2015

LITTLE QUESTION THE PRECIPITATION EVENT ASSOCIATED WITH THE NEXT
SYSTEM WILL PASS SOUTH OF LOWER MICHIGAN THIS AFTERNOON AND
EVENING. THEN... ANOTHER DIGGING POLAR JET CORE FROM NORTHERN
CANADA WILL PUSH ANOTHER COLD FRONT THROUGH THE AREA LATER
THURSDAY NIGHT OR EARLY FRIDAY. THERE IS JUST MOIST LOW TO MID
LEVEL MOISTURE TO GET A FEW RAIN SHOWERS AHEAD OF THE COLD FRONT.
BEYOND THAT A CANADIAN HIGH MOVES IN BY MID MORNING FRIDAY
ASSURING MOSTLY CLEAR SKIES BUT COOLER TEMPERATURES. SOME FROST
WILL BE POSSIBLE SATURDAY MORNING.

EARLY THIS WEDNESDAY MORNING WE HAVE A SOUTHERN STREAM SYSTEM
CAUSING AN AREA OF RAIN AND THUNDERSTORMS NEAR THE MISSISSIPPI
RIVER. IT IS CURRENTLY HEADING EASTWARD AND WOULD NORMALLY
BRING RAIN TO OUR AREA TODAY.  HOWEVER THIS TIME WE HAVE A
DIGGING NORTHERN STREAM SHORTWAVE AND ASSOCIATED  POLAR JET CORE
HEADING FOR THE WESTERN GREAT LAKES. THAT WILL FORCE THE SOUTHERN
STREAM SYSTEM SOUTH OF MICHIGAN THIS AFTERNOON AND EVENING. WE
WILL SEE CONSIDERABLE HIGH AND MID CLOUDS TODAY WITH AREAS NEAR
I-94 SEEING THE THICKER CLOUDS WHILE AREA NORTH OF I-96 WILL HAVE
CONSIDERABLE MORE SUNSHINE. EVEN SO IT WILL NOT GET ALL THAT WARM
TODAY...HIGHS SHOULD MOSTLY BE IN THE 50S. SOME CLEARING IS
EXPECTED TONIGHT WITH LIGHTER WINDS SO NORTHERN AREA COULD SEE A
LITTLE PATCHY FROST.

MEANWHILE A CLOSED...COLD CORE UPPER LOW...CURRENTLY NEAR BAFFIN`SISLAND
DROPS SOUTHWARD...REACHING SOUTHERN HUDSON BAY THURSDAY MORNING.
THIS WILL BRING ANOTHER COLD FRONT THROUGH THE AREA LATE THURSDAY
NIGHT. THERE WILL BE JUST ENOUGH LOW TO MID LEVEL MOISTURE AND
LIFT AHEAD OF THE COLD FRONT TO CREATE A LIGHT RAIN SHOWERS.
CLEARING WILL QUICKLY FOLLOW BY MID MORNING FRIDAY.

.LONG TERM...(FRIDAY NIGHT THROUGH TUESDAY)
ISSUED AT 326 AM EDT WED MAY 20 2015

TWO MAIN CONCERNS IN THE EXTENDED...FIRST IS THE FROST THREAT ON
FRIDAY NIGHT AND THEN STORMY WEATHER FROM SUNDAY THROUGH TUESDAY.

SFC HIGH MOVES EAST BY 12Z SATURDAY...BUT RETURN FLOW MAY NOT BE
STRONG ENOUGH TO PREVENT FREEZING TEMPS UP NORTH AND SOME FROST
ESPECIALLY ACROSS EASTERN ZONES.

ONCE THE HIGH DEPARTS SATURDAY NIGHT...RETURN FLOW STRENGTHENS
WITH WARMER AND MORE HUMID AIR RETURNING BY MONDAY. ISENTROPIC
ASCENT NORTH OF THE SFC WARM FRONT SHOULD BRING SHOWERS BY SUNDAY
MORNING AND A SERIES OF WEAK WAVES MOVING ALONG STALLED FRONT
WILL CONTINUE INTO TUESDAY. CONFIDENCE IS HIGH ON THE OVERALL
PATTERN ALTHOUGH THERE ARE THE USUAL DIFFERENCES IN THE DETAILS.
OVERALL THERE IS A HIGH CONFIDENCE OF SHOWERS AND A FEW
THUNDERSTORMS THROUGH THE PERIOD FROM SUNDAY TO TUESDAY.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z THURSDAY AFTERNOON)
ISSUED AT 154 PM EDT WED MAY 20 2015

VFR CONDITIONS ARE EXPECTED TO PERSIST THROUGH THURSDAY AFTERNOON.
HIGH CLOUDS WILL CONTINUE TO STREAM IN FROM THE WEST THIS
AFTERNOON AS AN UPPER WAVE OF LOW PRESSURE SWINGS INTO THE WESTERN
GREAT LAKES. CONSIDERABLE MID CLOUDS CAN BE EXPECTED AFTER 23Z
THIS EVENING...BASED BETWEEN 5 KFT AND 7KFT. SCATTERED CLOUDS
BELOW 5 KFT ARE POSSIBLE AFTER 00Z AT AZO/BTL/JXN.

IN ADDITION...A BAND OF LIGHT RAIN IS EXPECTED TO MOVE ACROSS
SOUTHERN LOWER MICHIGAN MAINLY BETWEEN 23Z AND 04Z THIS EVENING.
RAIN SHOWERS ARE EXPECTED TO ERODE SOMEWHAT AS THEY MOVE EAST INTO
LOWER MICHIGAN. FAIR AMOUNT OF UNCERTAINTY...SO INCLUDED VCSH AT
AZO/BTL. BOTTOM LINE...LIGHT RAIN SHOWERS ARE A POSSIBILITY AT
AZO/BTL/JXN AFTER 23Z...BUT CIGS AND VSBYS ARE EXPECTED TO REMAIN
VFR.

&&

.MARINE...
ISSUED AT 1208 PM EDT WED MAY 20 2015

WE WILL BE KEEPING AN EYE ON A CORE OF WIND THAT THE HRRR IS
TRYING TO DEVELOP DOWN THE SHORELINE SOUTH OF HOLLAND LATE THIS
AFTERNOON AND EVENING. CHANNELING/FUNNELING DOWN THE SHORELINE
BLUFFS ARE LIKELY THE REASON FOR THE WIND THAT IS SHOWING UP IN
THE MODELS. NORTHWEST WINDS OF 15-20 KNOTS OR SO DEVELOP WHICH
WILL LIKELY KICK THE WAVE FIELD UP A BIT. THINKING WE WILL STAY
BELOW SCA CRITERIA...BUT WORTH WATCHING THE SOUTH HAVEN PIER AND
BUOY OBS BETWEEN 300PM AND 900PM OR SO.


&&

.HYDROLOGY...
ISSUED AT 1139 AM EDT WED MAY 20 2015

NO REAL IMPACTS ARE EXPECTED IN THE NEAR FUTURE. RIVERS ARE STABLE
OR SLOWLY FALLING. ONLY SLIGHT CHANCES OF RAIN EXIST LATE THURSDAY
INTO EARLY FRIDAY. ANY MEANINGFUL PRECIPITATION IS EXPECTED TO
HOLD OFF UNTIL AT LEAST SUNDAY.

BY SUNDAY...CHANCES FOR PRECIPITATION WILL INCREASE AS A WARM
FRONT LIFTS NORTH AND BECOMES STATIONARY SOMEWHERE OVER THE GREAT
LAKES REGION. THE PLACEMENT OF THIS BOUNDARY...AND THE POSSIBILITY
OF IT MEANDERING A BIT...MAY PROVIDE MULTIPLE CHANCES FOR RAIN
THROUGH MUCH OF NEXT WEEK. THIS WILL BE SOMETHING TO MONITOR AND
UPDATES WILL BE PROVIDED AS WE GET CLOSER TO THE WEEKEND.

&&

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

$$

UPDATE...DUKE
SYNOPSIS...WDM
SHORT TERM...WDM
LONG TERM...OSTUNO
AVIATION...EBW
HYDROLOGY...JAM
MARINE...DUKE



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