Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 041732
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
132 PM EDT SAT JUL 4 2015

LATEST UPDATE...
AVIATION

.SYNOPSIS...
ISSUED AT 329 AM EDT SAT JUL 4 2015

A NEARLY IDEAL WEATHER IS EXPECTED FOR OUR FOURTH OF JULY WEEKEND
OVER SOUTHWEST LOWER MICHIGAN. SKIES SHOULD BE MOSTLY CLEAR TODAY
AND SUNDAY HOWEVER NORTH AND EAST OF BIG RAPIDS EXPECT SCATTERED
THUNDERSTORMS DURING THE MID TO LATE AFTERNOON. IT WILL GET
WARMER EACH DAY THROUGH MONDAY. HIGHS SHOULD BE NEAR 80 AWAY FROM
THE LAKE MICHIGAN BEACHES TODAY...MID 80S SUNDAY AND UPPER 80S FOR
THE FIRST TIME THIS YEAR ON MONDAY.

A COLD FRONT WILL COME THROUGH THE AREA EARLY TUESDAY PRECEDED BY
SHOWERS AND SCATTERED THUNDERSTORMS DURING THE EARLY MORNING HOURS
OF TUESDAY. AFTER THAT EXPECT PARTLY CLOUDY SKIES WITH HIGHS FROM
THE MID 70S TO AROUND 80 THE REST OF THE WEEK.

&&

.SHORT TERM...(TODAY THROUGH MONDAY)
ISSUED AT 329 AM EDT SAT JUL 4 2015

THE THERE ARE THREE ISSUES WE ARE CONSIDERING THIS WEEKEND. FIRST
IS THE THREAT FOR SCATTERED THUNDERSTORMS OVER OUR NORTHEAST CWA
THIS AFTERNOON...SECOND IS JUST HOW WARM IT WILL GET EACH DAY AND
FINALLY THE TIMING OF THE CONVECTION WITH THE COLD FRONT LATER
MONDAY OR MONDAY NIGHT (THAT IS MOSTLY AN ISSUE FOR THE LONG
RANGE PART OF THE FORECAST).

THE BIG PICTURE SHOWS OUR POLAR JET IS ALONG THE CANADIAN BOARD
FROM WESTERN CANADA INTO THE GREAT LAKES TODAY WITH TWO MAJOR
SHORT WAVES EMBEDDED IN IT THAT WE ARE WATCHING. THE FIRST IS
TRACKING ALONG THE CANADIAN BOARDER NEAR LAKE SUPERIOR THIS
MORNING AND WILL EXIT THE GREAT LAKES SUNDAY OVER QUEBEC. THE
SECOND ONE...WHICH IS MUCH STRONGER AND HAS A CLOSED UPPER LOW
ASSOCIATED WITH IT... TRIES TO DIG INTO THE CENTRAL GREAT LAKE BY
MONDAY. HOWEVER... AND EVEN STRONG SYSTEM UPSTREAM OF THAT WILL
KEEP THIS THAT SYSTEM FROM DIGGING LIKE IT OTHERWISE WOULD HAVE
IF THE WAVE LENGTH BETWEEN THE TWO SYSTEMS HAD BEEN GREATER. THE
TRAILING MUCH DEEP SYSTEM... FORECAST OVER WESTERN CANADA BY
EARLY NEXT WEEK THAT...WILL KEEP THE REALLY COOL AIR IN CANADA
INSTEAD OF OVER US. THAT IS DUE TO THE HEIGHT RISES THAT OCCUR IN
FRONT OF DEEP SYSTEM LIKE THAT. THAT WILL ALSO WEAKEN THE FRONT
THAT COMES THROUGH MONDAY NIGHT...DIMINISHING THE RISK FOR SEVERE
STORMS.

AS FOR TODAY...THE FIRST WEAK SHORTWAVE TRACKING THROUGH SOUTHERN
ONTARIO TODAY WILL HAVE THE JET CORE NORTH OF LAKE HURON BY MID
AFTERNOON. THE RESULTING LOW LEVEL JET WILL HAVE A 15 TO 20 KNOT
SPEED MAX OVER CENTRAL LAKE HURON. CLEARLY NOT AN IDEAL SET UP FOR
THUNDERSTORMS SINCE OUR NORTHEAST CWA IS IN THE RIGHT EXIT REGION
OF THE POLAR JET ( ALOFT). MODEL SOUNDING CONFIRM THIS BY SHOWING
VERY DRY AIR ABOVE 700 MB. ANY CONVECTION THAT GETS ABOVE 700 MB
WILL HAVE TO ENTRAIN ALL THAT DRY AIR. EVEN SO WE WILL HAVE A
COLD FRONT CREATING SURFACE CONVERGENCE AND MODEL SOUNDING STILL
SHOW UP TO 500 J/KG OF MOST UNSTABLE CAPE IN OUR NE CWA LATE THIS
AFTERNOON. I WOULD IMAGINE WE WILL SEE SOME SCATTERED TO ISOLATED
STORMS NORTH AND EAST OF BIG RAPIDS BETWEEN...SAY 2 PM AND 6 PM.

ONCE THAT SYSTEM IS OUT OF THE WAY WE EARLY TONIGHT WE GET SHORT
WAVE RIDGING FOR TONIGHT THROUGH SUNDAY NIGHT. THAT LETS THE WARM
AIR COME BACK IN AND WITH WEST TO SOUTHWEST WINDS THROUGH A DEEP
LAYER. I WOULD THINK THE FOREST FIRE SMOKE PLUM WE HAVE BEEN
SEEING OVER THE NORTHER MIDWEST WILL BE OUT OF OUR AREA BY THEN
DUE TO THE WIND DIRECTION SHIFT. THAT WILL ALLOW FOR BETTER
WARMING SUNDAY. I PUT HIGHS IN THE MID 80S.

ON MONDAY WE HAVE THAT NEXT SHORTWAVE HEADING OUR WAY. THE MODELS
ARE ALL SHOWING THE PRECIPITATION BAND COMING INTO OUR AREA AFTER
MIDNIGHT MONDAY NIGHT. SO MONDAY WILL SEE DEEP MIXING (SOUNDING
SUGGEST TO NEAR 725 MB) AND ABUNDANT SUNSHINE. ADD TO THAT A SOUTH
WIND... NOT A SOUTHWEST SURFACE WIND SO THE WINDS WILL NOT BE OFF
LAKE MICHIGAN... AND I WOULD THINK HIGHS WILL BE PUSHING 90 BY
MID AFTERNOON. I PUT UPPER 80S IN THE GRIDS.

BOTTOM LINE...MOSTLY CLEAR SKIES AND WARMER TEMPERATURES TODAY
THROUGH MOST OF MONDAY (ISOLATED THUNDERSTORMS NORTHEAST CWA THIS
AFTERNOON AND EARLY EVENING).

.LONG TERM...(MONDAY NIGHT THROUGH FRIDAY)
ISSUED AT 329 AM EDT SAT JUL 4 2015

SLIGHT DIFFERENCES IN THE MODELS ON THE TIMING OF A COLD FRONT...BUT
IT APPEARS TO COME THROUGH LATE MONDAY NIGHT/EARLY TUESDAY.  THIS
WILL BE DURING A MIN OF INSTABILITY...SO DESPITE BEING UNDER THE
RIGHT ENTRANCE REGION OF THE UPPER JET...SEVERE STORM CHANCES LOOK
MINIMAL AT THIS POINT.  THERE DOES APPEAR TO BE SOME ELEVATED
INSTABILITY...SO SOME OF THE STRONGER STORMS MAY PRODUCE HAIL.
STILL...THERE APPEARS TO BE FAVORABLE MOISTURE POOLING ALONG THE
FRONT...SO WILL MAINTAIN THE LIKELY POPS MONDAY NIGHT.  THE SHOWER
AND STORM COVERAGE SHOULD TREND DOWNWARD INTO TUESDAY AFTERNOON AS
THE FRONT DEPARTS.

IT WILL BE COOLER FOR MID WEEK WITH HIGHS BACK IN THE 70S.  DRY
WEATHER IS EXPECTED WEDNESDAY/WEDNESDAY NIGHT WITH HIGH PRESSURE
PASSING THROUGH.  THE MODELS SUGGEST A SHORT WAVE COMING THROUGH IN
THE THURSDAY/THURSDAY NIGHT TIME FRAME.  THE FLOW APPEARS RATHER
PROGRESSIVE...SO THE TIMING OF THIS WAVE IS SUBJECT TO CHANGE.  HAVE
20/30 POPS TO COVER THE WAVE.  SLIGHTLY WARMER AIR RETURNS THURSDAY
NIGHT INTO FRIDAY.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SUNDAY AFTERNOON)
ISSUED AT 132 PM EDT SAT JUL 4 2015

MOSTLY LIGHT RAIN SHOWERS ARE POSSIBLE THIS AFTERNOON OVER
CENTRAL LOWER MICHIGAN...MOST LIKELY AFFECTING THE GRR AND LAN
TERMINALS. THUNDERSTORMS ARE NOT ANTICIPATED.

AS NOTED ALREADY...WE EXPECT A RETURN TO MVFR VSBY AT MOST TERMINALS
EARLY SUNDAY MORNING. DISSIPATION SHOULD BE RAPID...MOST LIKELY
AROUND 12Z.

&&

.MARINE...
ISSUED AT 329 AM EDT SAT JUL 4 2015

HIGH PRESSURE MEANS NO HEADLINES NEEDED THROUGH SUNDAY NIGHT.
ONCE THE WINDS BECOME MORE WESTERLY OVER LAKE MICHIGAN THE WATER
TEMPERATURES WILL RISE BACK INTO THE 60S OVER THE BEACHES...THAT
WILL RESULT IN MORE PLEASANT BEACH WEATHER SUNDAY INTO MONDAY
(STORMS COME IN AFTER DARK)


&&

.HYDROLOGY...
ISSUED AT 1124 AM EDT SAT JUL 4 2015

THERE ARE NO EXISTING ADVISORIES ON AREA RIVERS. IMPROVEMENT IS
EXPECTED TO CONTINUE AT LEAST THROUGH THE WEEKEND.

OVERALL...DRY CONDITIONS WILL DOMINATE THE PATTERN THROUGH THE
FIRST HALF OF MONDAY. THERE IS A SLIGHT CHANCE OF AN ISOLATED
STORM THIS AFTERNOON THROUGH INTERIOR PORTIONS OF LOWER MICHIGAN.
BETTER CHANCES OF RAIN EXIST LATE MONDAY INTO EARLY TUESDAY WHEN A
COLD FRONT SWEEPS THROUGH THE AREA. A DECENT RAINFALL IS POSSIBLE
MONDAY BUT GIVEN THE RECENT PERIOD OF DRY WEATHER THIS SHOULD NOT
BE MUCH OF A CONCERN. AMOUNTS IN THE REALM OF ONE- HALF TO THREE-
QUARTERS OF AN INCH ARE POSSIBLE. AMOUNTS MAY VARY IN OR NEAR
THUNDERSTORMS.

&&

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

$$

SYNOPSIS...WDM
SHORT TERM...WDM
LONG TERM...JK
AVIATION...TJT
HYDROLOGY...JAM
MARINE...WDM


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