Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 291139
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
739 AM EDT FRI MAY 29 2015

LATEST UPDATE...
AVIATION

.SYNOPSIS...
ISSUED AT 327 AM EDT FRI MAY 29 2015

A SURGE OF WARM MOIST AIR INTO SOUTHWEST LOWER MICHIGAN AHEAD OF
THE COLD FRONT WILL BRING SCATTERED SHOWERS AND THUNDERSTORMS TO
THE AREA TODAY INTO THIS EVENING. IT WILL ALSO BE WARM AND HUMID
TODAY. THE COLD FRONT COMES THROUGH THE AREA SATURDAY MORNING.
THAT WILL BRING RAIN AND FALLING TEMPERATURES IN THE AFTERNOON.
ONCE THE FRONT CLEARS THE AREA SATURDAY NIGHT SKIES WILL CLEAR AND
IT WILL BE SIGNIFICANTLY COOLER SUNDAY INTO MONDAY. A SLOW WARM UP
WITH MOSTLY CLEAR SKIES IS EXPECT THROUGH THE THE MIDDLE OF NEXT
WEEK.

&&

.SHORT TERM...(TODAY THROUGH SUNDAY)
ISSUED AT 327 AM EDT FRI MAY 29 2015

THE ISSUE TODAY IS THE THREAT FOR DAY TIME CONVECTION WITH THE
SURGE OF WARM MOIST AIR INTO THE REGION FROM THE SOUTH. THE NEXT
ISSUE IS THE RAIN FOR SATURDAY AS THE COLD AIR COMES IN DURING THE
DAY. FINALLY THERE IS AN ISSUE WITH A WAVE ON THE FRONT SATURDAY
NIGHT INTO SUNDAY MORNING. THAT WILL BE FOLLOWED BY HIGH PRESSURE
AND COOLER TEMPERATURES SUNDAY.

IT IS RATHER CLEAR FROM LOOPING THE SURFACE DEW POINTS (VARIOUS
MODELS) THE PRECIPITABLE WATER VALUES AND SURFACE TO 850 MEAN DEW
POINTS A WARM FRONT DOES PUSH THROUGH THE AREA TODAY. MODEL
SOUNDINGS TO LOOK A TOUCH MOIST THIS AFTERNOON AND THE MOST
UNSTABLE CAPE VALUES EXCEED 1000 J/KG ACROSS THE AREA (EXCEPT NEAR
THE LAKE SHORE) FROM LATE MORNING INTO EARLY EVENING. THE DEEP
LAYER SHEAR IS WEAK... UNDER 25 KNOTS THROUGH (JET IS FAR TO OUR
NORTH AND WEST YET). THERE IS ALSO A SHORTWAVE THAT TRACKS THROUGH
THE AREA TODAY BUT THE BEST DYNAMICS WITH THAT GO NORTH OF OUR
CWA. MY SPIN ON THIS IS SHOWERS AND THUNDERSTORMS WILL BE AROUND
BUT THEY WILL LIKELY NOT BE SEVERE.

TONIGHT THE ACTIVITY SHOULD COME TO AN END BY MID EVENING THEN WE
WAIT FOR THE COLD FRONT TO COME THROUGH. SEEMS THE RAIN WILL
LARGELY BE BEHIND THE FRONT IN THE COLD AIR. THERE IS VERY LITTLE
ELEVATED INSTABILITY SATURDAY EVEN THROUGH THE DEEP LAYER SHEAR IS
OVER 40 KNOTS. MOSTLY THIS LOOKS MORE LIKE A COLD RAIN THAN
ANYTHING ELSE. THIS IS ONE OF THOSE... AS I LIKE TO CALL IT... JET
LIFT EVENTS (WE ARE IN THE ENTRANCE REGION OF THE UPPER JET).
TEMPEATURES COULD FALL DURING THE DAY AS THE COLD AIR COMES IN
SATURDAY.

ALL OF THIS MOVES EAST OF THE AREA SATURDAY NIGHT SO SKIES SHOULD
CLEAR AND IT WILL GET CHILLY. WE MAY EVEN SEE FROST IN OUR
NORTHERN COUNTIES (I DID NOT ADD THIS TO THE GRIDS AS I WAS NOT
SURE OF THIS JUST YET). THE GLITCH THOUGH TO WATCH WITH SATURDAY
NIGHT INTO SUNDAY MORNING IS WE HAVE A SHEARING OUT SOUTHERN
STREAM WAVE COMING THROUGH. IF THE MODELS ARE JUST A TOUCH TO FAST
AND NOT DEEP ENOUGH (TYPICAL ERROR FOR THIS SORT OF THING) WE MAY
SEE THE SHOWERS LINGER INTO SUNDAY MORNING. NO MATTER WHAT SKIES
SHOULD CLEAR BY MIDDAY SUNDAY.

.LONG TERM...(SUNDAY NIGHT THROUGH THURSDAY)
ISSUED AT 327 AM EDT FRI MAY 29 2015

A HIGH PRESSURE RIDGE WILL CONTINUE TO BUILD IN SUNDAY NIGHT INTO
EARLY NEXT WEEK AND PRODUCE FAIR BUT COOL WEATHER. SOME PATCHY FROST
IS POSSIBLE ACROSS OUR NNE FCST AREA DURING THE EARLY MORNING HOURS
MONDAY.

TEMPERATURES WILL UNDERGO A GRADUAL MODERATING TREND TUESDAY AND
ESPECIALLY BY WEDNESDAY AS SOUTHERLY RETURN FLOW DEVELOPS ON THE
BACK SIDE OF THE DEPARTING RIDGE.

AN OVERALL MEDIUM RANGE GUIDANCE CONSENSUS AND GUIDANCE TRENDS
SUGGEST THAT DRY WX SHOULD CONTINUE THROUGH WEDNESDAY WITH THE NEXT
CHANCE FOR PRECIPITATION NOT COMING UNTIL LATE NEXT WEEK AS
CONTINUED SOUTHERLY FLOW RESULTS IN INCREASING MOISTURE IN
CONJUNCTION WITH SOME WEAK ISENTROPIC UPGLIDE.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z SATURDAY MORNING)
ISSUED AT 739 AM EDT FRI MAY 29 2015

WHILE I DO EXPECT SCATTERED SHOWERS AND THUNDERSTORMS TO BE AROUND
TODAY INTO EARLY THIS EVENING THE COVERAGE WILL NOT BE ENOUGH TO
PUT MORE THAN VCTS IN THE TAFS. THE SOLID RAIN AND IFR CIGS WILL
NOT MOVE INTO OUR TAF SITES UNTIL WELL AFTER 12Z SATURDAY. FOR THE
MOST PART EXPECT VFR CONDITIONS THROUGH TONIGHT.

&&

.MARINE...
ISSUED AT 327 AM EDT FRI MAY 29 2015

SEEMS LIKELY WE WILL NEED SOME SORT OF MARINE HEADLINES FOR
SATURDAY AS THE COLD AIR COMES IN AND BUILD LARGE WAVES WITH GUSTY
NORTH WINDS.


&&

.HYDROLOGY...
ISSUED AT 1220 PM EDT THU MAY 28 2015

TOTAL QPF FRIDAY THROUGH SATURDAY WITH THE NEXT ROUND OF SHOWERS
AND THUNDERSTORMS CONTINUES TO TREND DOWNWARD AT AROUND AN INCH
OR LESS. GIVEN THAT BASE FLOWS ARE NEAR NORMAL IN THE GRAND RIVER
BASIN AND BELOW NORMAL IN THE KALAMAZOO BASIN...WE EXPECT MODEST
RISES WITH SOME SITES PERHAPS REACHING BANKFULL BUT NOTHING OF
GREAT SIGNIFICANCE. THE COMING WEEK LOOKS DRY WHICH SHOULD ALLOW
LEVELS TO FALL ONCE AGAIN.

&&

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

$$

SYNOPSIS...WDM
SHORT TERM...WDM
LONG TERM...LAURENS
AVIATION...WDM
HYDROLOGY...TJT
MARINE...WDM


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