Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 290002
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
802 PM EDT TUE JUL 28 2015

LATEST UPDATE...
AVIATION

.SYNOPSIS...
ISSUED AT 320 PM EDT TUE JUL 28 2015

A COLD FRONT MOVING ACROSS WISCONSIN THIS AFTERNOON WILL MOVE OVER
LOWER MICHIGAN WEDNESDAY MORNING. SCATTERED SHOWERS AND PERHAPS A
THUNDERSTORM ARE POSSIBLE WITH THIS FRONTAL PASSAGE...BUT
SIGNIFICANT RAIN IS UNLIKELY. HIGHS WILL BE A COUPLE OF DEGREES
COOLER WEDNESDAY AND THURSDAY BUT REMAIN NEAR NORMAL.

&&

.SHORT TERM...(THIS EVENING THROUGH THURSDAY NIGHT)
ISSUED AT 320 PM EDT TUE JUL 28 2015

FORECAST CONCERNS DEAL WITH A COLD FRONTAL PASSAGE EARLY WEDNESDAY
AND THE PCPN ASSOCIATED WITH IT.

OVERALL...THIS SYSTEM DOESN`T IMPRESS ME. CONVECTION AHEAD OF THE
FRONT IN WISCONSIN HAS DIMINISHED QUITE A BIT THIS
AFTERNOON...PROBABLY DUE TO ITS MOVING INTO THE UPPER RIDGE THAT IS
OVER LOWER MICHIGAN ATTM.

THE CORE OF THE DYNAMICS WITH THIS SYSTEM ARE WELL NORTH IN WESTERN
ONTARIO AND THAT WILL RESULT IN NOT MUCH MORE THAN SCATTERED SHOWERS
AND ISOLATED THUNDERSTORMS WEDNESDAY. DESPITE SBCAPE AROUND 1200
J/KG...LI`S ARE NOT IMPRESSIVE AND THE CWA WILL BE IN THE RIGHT EXIT
REGION OF THE UPPER JET...ALSO NOT CONDUCIVE FOR STRONGER STORMS.
THERE ISN`T MUCH OF A LLJ EITHER. THE ONE THING THAT THE SYSTEM DOES
HAVE GOING FOR IT IS HIGH PRECIPITABLE WATER VALUES NEAR 2.35
INCHES. SO WE MAY HAVE A LOW TOPPED SHOWER SCENARIO WITH BURSTS OF
HEAVIER RAIN. PCPN SHOULD WIND DOWN BY AFTERNOON AFTER WHICH HIGH
PRESSURE WILL BUILD BACK INTO THE GREAT LAKES.

.LONG TERM...(FRIDAY THROUGH TUESDAY)
ISSUED AT 320 PM EDT TUE JUL 28 2015

I AM GOING TO CONTINUE TO SAY WHAT I HAVE BEEN SAYING...THE TREND IS
TOWARD COOLER AND WITH PERIODS OF SHOWERS (NOT SO MUCH THUNDERSTORMS
EITHER).

IT LOOKS VERY GOOD FOR A UNSUALLY DEEP UPPER LOW TO DEVELOP AND
STALL OVER SOUTHERN HUDSON BAY. THIS IS A RATHER UNUSUAL WEATHER
PATTERN FOR LATE JULY OR EARLY AUGUST. THE NAERFS SHOWS THE RETURN
PERIOD OF SUCH AN EVENT (DEEP UPPER LOW OVER HUDSON BAY) TO BE ONE
DAY IN 10 YEARS. THE LARGE SCALE PATTERN FORECAST LOOKS GOOD AND CAN
BE RELIED ON... WHAT IS QUESTIONABLE IS THE DETAILED SURFACE WEATHER
WE WILL SEE FROM THIS UNUSAL PATTERN. TYPICALLY THE MODELS DO NOT DO
WELL IN FORECASTING SUCH USUSUAL PATTERNS. ONE CAN CLEARLY SEE THIS
IN HOW EACH MODEL RUN SEEMS TO HAVE A DIFFERENT SOLUTION THAN THE
RUN BEFORE. FROM MODEL TO MODEL THERE ARE SIGNIFCANT DIFFERENCES IN
THE TIMING OF THE SHORTWAVES AND THE STRENGHT OF THOSE SHORTWAVES
TOO.

I WOULD TOTALLY NOT RELAY ON OUR FORECAST POPS FOR THIS WEEKEND. I
REALLY THINK THERE IS A CHANCE OF SHOWERS EACH DAY DEPENDING ON THE
TIMING OF THOSE SHORTWAVES AND THE STRENGTH THEREOF. WE HAVE THE
HIGHEST POPS SUNDAY INTO MONDAY... BUT THERE IS A SYSTEM COMING
THROUGH ON FRIDAY AND IT MAY WELL HAVE SHOWERS WITH IT. IN FACT I
WOULD EXPECT OUR POPS TO INCREASE SIGNIFCANTLY FOR FRIDAY OVER TIME.
SIMILARLY FOR SATURDAY TOO...BUT THAT COULD BE DELAYED UNTIL
SUNDAY... JUST DEPENDS ON THE TIMING OF THE SHORTWAVES.

ALSO LIKE I HAVE BEEN SAYING I THINK BY THE MIDDLE OF NEXT WEEK WE
WILL BE SEEING HIGHS IN THE 70S AND LOWS IN THE 50S. WITH AN UPPER
LOW THAT DEEP SO CLOSE TO US IT IS HARD TO IMAINGE SOME OF THAT COLD
AIR WOULD NOT FINALLY MAKE IT THIS FAR SOUTH. ACTUALLY THE LATEST
GFS AND ECWMF ARE NOW SHOWING THIS BUT THE 00Z RUN OF THE ECMWF DID
NOT SHOW THIS...WHILE THE 12Z RUN FROM YESTERDAY DID.

BOTTOM LINE THINK...COOLER WITH PERIODS OF SHOWERS.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z WEDNESDAY EVENING)
ISSUED AT 802 PM EDT TUE JUL 28 2015

AN AREA OF SCATTERED SHOWERS WITH PERHAPS ISOLATED THUNDER IS
EXPECTED TO CROSS LAKE MICHIGAN BETWEEN 09-12Z WED. ANY
STORMS/HEAVIER SHOWERS SHOULD WEAKEN AS THEY CROSS LAKE MICHIGAN
AND APPROACH KMKG AFTER 09Z WED. THE COLD FRONT WILL SWEEP ACROSS
SOUTHWEST LOWER MICHIGAN BETWEEN 12Z-18Z WEDNESDAY. AS SCATTERED
RAIN SHOWERS MOVE EAST ACROSS THE AREA...SOME INTENSIFICATION IS
POSSIBLE AFTER 15Z TOWARD KLAN AND KJXN. THE ENVIRONMENT WILL BE
SUPPORTIVE OF A FEW STORMS CAPABLE OF LOCALLY HEAVY RAINFALL.
BRIEF MVFR CONDITIONS WILL BE POSSIBLE AT ALL TAF SITES. VERY
BRIEF IFR IS EVEN POSSIBLE PRIMARILY BETWEEN 15-18Z. BUT FORECAST
CONFIDENCE IN COVERAGE OF SHOWERS AND ANY HEAVIER RAIN SHOWERS IS
LOW AT THIS TIME. PREVAILING CONDITIONS SHOULD REMAIN VFR. SKIES
WILL CLEAR OUT FROM WEST TO EAST BETWEEN 18-00Z WEDNESDAY.

WINDS WILL VEER WESTERLY BEHIND THE COLD FRONT AND INCREASE TO
10-15 KTS FROM LATE WEDNESDAY MORNING THROUGH THE AFTERNOON.

&&

.MARINE...
ISSUED AT 320 PM EDT TUE JUL 28 2015

AFTER THE COLD FRONT PASSES THROUGH WEDNESDAY WEST WINDS WILL BOOST
WAVE HEIGHTS TO AROUND 2 FEET. THUS NO HAZARDS IN THE SHORT TERM.


&&

.HYDROLOGY...
ISSUED AT 1250 PM EDT TUE JUL 28 2015

RIVER LEVELS ARE FALLING AND WELL BELOW BANKFULL. WITH UNDER A
HALF INCH OF PRECIPITATION EXPECTED INTO NEXT WEEK... THESE
CONDITIONS SHOULD CONTINUE.

&&

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

$$

SYNOPSIS...04
SHORT TERM...04
LONG TERM...WDM
AVIATION...EBW
HYDROLOGY...63
MARINE...04


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