Area Forecast Discussion
Issued by NWS Grand Rapids, MI

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

000
FXUS63 KGRR 202242
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
642 PM EDT SAT SEP 20 2014

LATEST UPDATE...
UPDATE

.SYNOPSIS...
ISSUED AT 319 PM EDT SAT SEP 20 2014

A COLD FRONT WILL MOVE ACROSS LOWER MICHIGAN TONIGHT TRIGGERING
SHOWERS AND THUNDERSTORMS, SOME OF WHICH MAY BE STRONG. SHOWERS WILL
LINGER INTO SUNDAY BEFORE CLEARING DEVELOPS LATE IN THE DAY. AS
SKIES CLEAR SUNDAY NIGHT PATCHY FROST MAY DEVELOP NORTH OF US-10.

&&

.UPDATE...
ISSUED AT 640 PM EDT SAT SEP 20 2014

UPDATED TO REFLECT THE SEVERE THUNDERSTORM WATCH CANCELLATION.
ALSO CLEANED UP PCPN GRIDS AND REFLECT LOWER POPS THROUGH THE
EVENING. STILL LOOKING AT PCPN MOVING BACK IN AFTER 06Z WITH THE
NEXT SHORT WAVE.

&&

.SHORT TERM...(THIS EVENING THROUGH MONDAY NIGHT)
ISSUED AT 319 PM EDT SAT SEP 20 2014

FORECAST CONCERNS DEAL WITH SEVERE POTENTIAL TONIGHT.

RADAR TRENDS SHOW STORMS CONTINUING TO DEVELOP ACROSS THE CWA.
INSTABILITY HAS INCREASED A BIT WITH LI/S NEAR -2C. HOWEVER THERE IS
STILL QUITE A BIT OF CONVECTIVE INHIBITION IN PLACE. THAT CINH
DECREASES TOWARD THE FAR SRN CWA. IF WE`RE GOING TO SEE SVR STORMS
THIS AFTERNOON THEY WILL BE OVER THE FAR SRN CWA. THIS IS ALSO WHERE
THE GREATEST SHEAR IS...NEAR 50 KTS. MID LEVEL JET MOVING IN WILL
ALSO AID IN STORM DEVELOPMENT. SPC HAS PLACED THE SRN ROW OF
COUNTIES IN A SVR WATCH INTO THE EVENING. THE SVR POTENTIAL WILL
LAST THROUGH MID TO LATE EVENING AND WIND GUSTS IN THE 50-60 MPH
RANGE ARE THE MAIN THREAT.

A WAVE DEVELOPING ON THE FRONTAL BOUNDARY IN CONJUNCTION WITH A
STRONG SHORT WAVE MOVING ACROSS THE GREAT LAKES WILL RESULT IN
SHOWERS IN THE GRIDS TONIGHT AND SUNDAY MORNING. HIGH PRESSURE
BUILDS SOUTH BY AFTERNOON SETTING THE STAGE FOR GOOD RADIATIONAL
COOLING SUNDAY NIGHT. WE HAVE SOME PATCHY FROST IN THE GRIDS OVER
THE FAR NE CWA SUNDAY NIGHT WITH LOWS THERE IN THE MID 30S.

.LONG TERM...(TUESDAY THROUGH SATURDAY)
ISSUED AT 319 PM EDT SAT SEP 20 2014

QUIET WEATHER EXPECTED IN THE EXTENDED PERIOD AS THE GREAT LAKES
REGION IS DOMINATED BY STRONG RIDGING AT THE SFC AND ALOFT. WITH DRY
SOUNDINGS AND GENERAL SUBSIDENCE WE SHOULD SEE TEMPERATURE RANGES
GREATER THAN GUIDANCE...WITH MAXES A BIT WARMER AND MINS A BIT
COOLER. MADE SOME TWEAKS IN THAT DIRECTION.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SUNDAY AFTERNOON)
ISSUED AT 145 PM EDT SAT SEP 20 2014

THUNDERSTORMS ARE EXPECTED THROUGH ABOUT 02Z TO 04Z WITH THE
HIGHEST CHANCE ACROSS SOUTHEAST LOWER MICHIGAN. THERE COULD BE
STRONG DOWNDRAFTS AND LARGE HAIL WITH A FEW OF THESE STORMS BUT
THE SPECIFICS IN TIMING AND LOCATION CANNOT BE PINNED DOWN UNTIL
THE STORMS ACTUALLY FORM. OUTSIDE OF THE STORMS...SOUTHWEST WINDS
WILL CONTINUE TO GUST TO 25 KNOTS INTO THIS EVENING.

AFTER 04Z...EXPECT MOSTLY VFR THEN SOME MVFR AND EVEN IFR
CONDITIONS BY 12Z SUNDAY AS LOW STRATUS CLOUD DECK MOVES IN.


&&

.MARINE...
ISSUED AT 347 PM EDT SAT SEP 20 2014

CONTINUED WITH THE SCA THROUGH SUNDAY NIGHT. WINDS WILL INCREASE
SUNDAY BUT REMAIN JUST BELOW GALES.


&&

.HYDROLOGY...
ISSUED AT 319 PM EDT SAT SEP 20 2014

RIVER FLOODING IS UNLIKELY GIVEN QPF OVER THE NEXT 24-48 HOURS.
HOWEVER...ANY LOCALLY PERSISTENT CONVECTION MAY LEAD TO SMALL STREAM
AND POOR DRAINAGE ISSUES. PER NCRFC ENSEMBLE QPF RIVER
SCENARIOS...SOME OF THE SMALLER STREAMS AND RIVERS IN SOUTH CENTRAL
LOWER MI MAY APPROACH BANKFULL IF RAINFALL AMOUNTS ACHIEVE THE MAX
EXPECTED /95 PERCENT CONFIDENCE INTERVAL/ QPF THRESHOLD.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LM...SMALL CRAFT ADVISORY UNTIL 8 AM EDT MONDAY FOR LMZ844>849.

&&

$$

UPDATE...93
SYNOPSIS...93
SHORT TERM...93
LONG TERM...OSTUNO
AVIATION...OSTUNO
HYDROLOGY...CAS
MARINE...93





USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.