Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 131140
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
740 AM EDT SUN JUL 13 2014

LATEST UPDATE...
AVIATION

.SYNOPSIS...
ISSUED AT 321 AM EDT SUN JUL 13 2014

A FRONTAL SYSTEM MOVING THROUGH EARLY THIS MORNING WILL BRING AN END
TO THE WIDESPREAD SHOWER AND STORM ACTIVITY FOR THE AREA. MILD AIR
WILL REMAIN IN PLACE FOR THE DAY TODAY. DRIER AIR WILL BEGIN TO
FILTER IN. ANOTHER FRONTAL SYSTEM WILL MOVE IN DURING THE DAY ON
MONDAY. THE BEST CHANCE FOR SHOWERS AND STORMS WILL BE ACROSS THE SE
PORTION OF THE STATE AS A WAVE OF LOW PRESSURE RIDES ALONG THE
FRONT. BEHIND THE MONDAY FRONT...MUCH COOLER AND A FEW SHOWERS CAN
BE EXPECTED FOR TUESDAY AND INTO WEDNESDAY.

&&

.SHORT TERM...(TODAY THROUGH TUESDAY)
ISSUED AT 321 AM EDT SUN JUL 13 2014

THE MAIN FOCUS OF THE FCST IS DETERMINING PCPN CHCS THROUGH THE
PERIOD AS A SERIES OF FRONTS MOVE THROUGH...AND EVENTUALLY THE UPPER
LOW DROPS DOWN INTO THE AREA.

THUNDERSTORM COVERAGE IS DWINDLING BY THE MINUTE THIS MORNING WITH
MOST OF THE PCPN IN THE FORM OF STRATIFORM RAINFALL. THE LLJ THAT
WAS INITIALLY HELPING TO FIRE THIS PCPN IS NOW SHIFTING EAST OF THE
AREA AND THE INSTABILITY IS WANING WITH TIME. WE EXPECT THAT ALL
RAINFALL WILL EXIT THE CWFA TO THE SE BY 12Z THIS MORNING.

SOME FOG AND LOW CLOUDS WILL BE POSSIBLE THIS MORNING IN THE WAKE OF
THE PCPN. WE EXPECT TO SEE A DECREASE IN CLOUD COVER AND A DECENT
AMOUNT OF SUNSHINE THIS AFTERNOON. THE THREAT OF A FEW
SPRINKLES/LIGHT SHOWERS IS NOT ZERO AS ANOTHER FRONT DROPS SOUTH.
FCST SOUNDINGS GENERALLY SHOW THE VERTICAL DEPTH OF THE CLOUD LAYER
LESS THAN 5K FT WITH DRIER AIR MOVING IN. ALSO...THERE IS NO SHORT
WAVE TO SPEAK OF THIS FAR SOUTH.

THE CHANCE OF RAIN WILL INCREASE A BIT ON MONDAY AFTERNOON...
ESPECIALLY ACROSS THE SE. ANOTHER FRONT WILL DROP DOWN THROUGH THE
AREA DURING THE DAY ON MONDAY. AS IS THE CASE ON SUN...THE FRONT
WILL NOT HAVE MUCH SUPPORT FOR IT AS IT MOVES THROUGH THE NW HALF OF
THE CWFA. WE EXPECT THAT SOME INCREASE IN PCPN WILL OCCUR ACROSS THE
SE CORNER OF THE CWFA MON AFTERNOON AS SOME MOISTURE TRANSPORT TAKES
PLACE AS THE UPPER LOW STARTS DIGGING ACROSS THE UPPER MIDWEST.
SUFFICIENT INSTABILITY WILL DEVELOP ACROSS THE FAR SE CORNER OF THE
CWFA MON AFTERNOON FOR THUNDER. IF THUNDER DOES DEVELOP...THERE IS
VERY IMPRESSIVE SHEAR OF 45 TO 55 KNOTS THAT COULD ORGANIZE SOME
STORMS.

A NICE CHUNK OF THE CORE OF THE COLD AIR ALOFT WILL THEN DROP DOWN
OVER THE AREA MON NIGHT AND REMAIN OVERHEAD INTO TUE. THE UPPER LOW
SW OF HUDSON BAY THIS MORNING IS EXPECTED TO ROTATE DOWN MON NIGHT
AS ANOTHER UPPER LOW DEVELOPS NEAR JAMES BAY. WE WILL SEE SHOWERS
MOVE IN MON NIGHT WITH THE LOW DROPPING DOWN. WE WILL THEN SEE
MAINLY DIURNAL SHOWERS POP UP ON TUE WITH THE HEATING OF THE DAY. WE
CAN NOT RULE OUT AN ISOLATED RUMBLE OF THUNDER WITH THE COLD POOL
OVERHEAD. INDICATIONS ARE THOUGH THE THE INSTABILITY WILL BE LIMITED
ENOUGH TO LEAVE THUNDER OUT FOR NOW.

.LONG TERM...(TUESDAY NIGHT THROUGH SATURDAY)
ISSUED AT 321 AM EDT SUN JUL 13 2014

NO SIGNIFICANT CHANGES TO THE INHERITED FORECAST. SCATTERED SHOWERS
AND THUNDERSTORMS ARE POSSIBLE WEDNESDAY AFTERNOON WHEN SURFACE
DIURNAL HEATING WILL COINCIDE WITH COLD TEMPERATURES AND POSSIBLE
WEAK PV FORCING ALOFT. THE REST OF THE FORECAST LOOKS DRY WITH
PERSISTENT SURFACE HIGH PRESSURE CENTERED NEAR THE REGION.
TEMPERATURES WILL GRADUALLY MODERATE TO NEAR NORMAL BY THIS WEEKEND.
PRECIPITATION CHANCES APPEAR TO INCREASE SUNDAY JUST BEYOND THE
VALID PERIOD OF THIS FORECAST.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z MONDAY MORNING)
ISSUED AT 740 AM EDT SUN JUL 13 2014

WITH PRECIPITATION AND LOW CLOUDS RAPIDLY EXITING TO THE EAST OVER
SOUTHERN LOWER MICHIGAN...EXPECT BRIEF LINGERING IFR CONDITIONS
AT MOST TERMINALS MAINLY BETWEEN 12-13Z FOLLOWED BY VFR CONDITIONS
THE REST OF THE VALID PERIOD. CONFIDENCE IS HIGH ON HAVING VFR
CONDITIONS AREAWIDE BY 15Z.

&&

.MARINE...
ISSUED AT 321 AM EDT SUN JUL 13 2014

WE WILL NOT BE ISSUING ANY HEADLINES WITH THIS FCST PACKAGE. WE DO
EXPECT SOME WINDS UP TO 20 KNOTS TODAY. THIS WILL CREATE SOME CHOPPY
CONDITIONS INITIALLY BEFORE WINDS DIMINISH A BIT THIS AFTERNOON OVER
THE WATERS. A MODERATE RISK OF SWIM HAZARDS WILL BE FOUND EARLY ON
BEFORE CONDITIONS IMPROVE.

WE WILL NEED TO KEEP AN EYE ON THE POTENTIAL FOR SOME WATERSPOUTS
MID WEEK WITH THE UPPER LOW NEARBY.


&&

.HYDROLOGY...
ISSUED AT 321 AM EDT SUN JUL 13 2014

THE HEAVY RAIN THREAT IS ENDING FOR THE AREA EARLY THIS MORNING. THE
FRONTAL SYSTEM THAT IS MOVING THROUGH WILL SWEEP ALL OF THE DEEP AND
RICH MOISTURE OUT OF THE AREA. SOME LOCALES ACROSS OTTAWA COUNTY SAW
SOME LOCALLY HEAVY RAINFALL OF 3 TO 4 INCHES. NO SIGNIFICANT ISSUES
HAVE BEEN REPORTED BY LAW ENFORCEMENT YET.

A THREAT FOR RAIN WILL COME BACK FOR MONDAY THROUGH MID
WEEK...HOWEVER IT IS NOT EXPECTED TO BE WIDESPREAD. HEAVY DOWNPOURS
ARE NOT EXPECTED WITH PRECIPITABLE WATER VALUES EXPECTED TO BE UNDER
AN INCH WHICH IS BELOW AVERAGE FOR THIS TIME OF YEAR.

&&

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

$$

SYNOPSIS...NJJ
SHORT TERM...NJJ
LONG TERM...TJT
AVIATION...TJT
HYDROLOGY...NJJ
MARINE...NJJ





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