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 112256
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
656 PM EDT FRI APR 11 2014

LATEST UPDATE...
AVIATION

.SYNOPSIS...
ISSUED AT 337 PM EDT FRI APR 11 2014

A WET WEEKEND LOOKS TO BE SHAPING UP AS A FRONTAL BOUNDARY WILL
SLOWLY PROGRESS THROUGH THE REGION. AREAS OF LOW PRESSURE WILL RIDE
ALONG THE BOUNDARY BRINGING PERIODS OF SHOWERS AND THUNDERSTORMS. A
FEW SHOWERS WILL MOVE THROUGH THE AREA THIS EVENING...BUT THE BULK
OF THE RAIN IS EXPECTED FROM SATURDAY AFTERNOON INTO MONDAY MORNING.
AREA RIVERS ARE ALREADY ABOVE NORMAL SO A FLOODING THREAT EXISTS.
THE RIVER FLOODING COULD PERSIST WELL INTO NEXT WEEK...AS WE COULD
SEE RAINFALL IN EXCESS OF 2 INCHES IN SPOTS. IT WILL BE MILD THROUGH
THE WEEKEND...WITH TEMPERATURES FALLING BEHIND THE FRONT BACK INTO
THE 30S MONDAY INTO MONDAY NIGHT.

&&

.SHORT TERM...(THIS EVENING THROUGH SUNDAY NIGHT)
ISSUED AT 337 PM EDT FRI APR 11 2014

FOCUS OF THE SHORT TERM HAS BEEN ON THE HEAVY RAIN THREAT FROM THIS
WEEKEND INTO MONDAY. HYDRO DISCUSSION CONTAINS THE DETAILS ON THE
FLOOD THREAT AND HYDRO CONCERNS OVERALL...BUT WILL BE ISSUING A
FLOOD WATCH FOR ESSENTIALLY THE NORTHWEST HALF OF THE FORECAST AREA.

STATIONARY BOUNDARY IS FORECAST TO SET UP ACROSS THE AREA SATURDAY
EVENING AND ESSENTIALLY REMAIN IN PLACE OR NEARBY THROUGH MONDAY
MORNING. A SOUTHWEST FLOW WILL BE IN PLACE ALOFT WITH SHORTWAVES
EJECTING OUT OF THE SOUTHWEST U.S. THE MAIN SHORTWAVE CAN BE SEEN
SPINNING OFF THE SOUTHERN CALIFORNIA COAST. IT IS FORECAST TO MOVE
THROUGH THE AREA SUNDAY NIGHT WHICH WILL LIKELY BE THE TIME FRAME OF
HEAVIEST RAIN (SUNDAY AFTERNOON INTO MONDAY MORNING). MULTIPLE
SHORTWAVES WILL INTERACT WITH THE BOUNDARY THOUGH BRINGING ROUNDS OF
RAIN. EMBEDDED THUNDER LOOKS LIKE A GOOD BET WITH 850MB LI/S
NEGATIVE MUCH OF THE TIME FRAME OF CONCERN FROM SATURDAY AFTERNOON
INTO MONDAY MORNING. THE 850MB LLJ RAMPS UP CONSIDERABLY SATURDAY
AFTERNOON AND EVENING AND AGAIN INTO SUNDAY NIGHT. AT THIS POINT NOT
THINKING WE ARE LOOKING AT A SEVERE THREAT WITH INSTABILITY THAT MAY
BE ON THE MARGINAL SIDE. DYNAMICS WILL BE STRONG HOWEVER WITH 0-6KM
SHEAR VALUES THAT WILL BE MORE THAN ADEQUATE. DAY TWO AND THREE
GENERAL THUNDER LOOKS GOOD VIA SPC.

.LONG TERM...(MONDAY THROUGH FRIDAY)
ISSUED AT 337 PM EDT FRI APR 11 2014

CONCERN REMAINS FOR RAIN CHANGING OVER TO SNOW ON THE BACK SIDE OF
THE SYSTEM MONDAY INTO EARLY TUESDAY.  EXPECT WE WILL SEE STEADY TO
SLOWLY FALLING TEMPS MONDAY AS H8 TEMPS DROP FROM AROUND -2C TO -10C
INTO MONDAY NIGHT.  THE COLDEST AIR SHOULD BE MOVING IN AS THE PCPN
IS MOVING OUT...SO AT THIS POINT NOT EXPECTING SIGNIFICANT SNOWS...
BUT AN INCH OR TWO WILL BE POSSIBLE ACROSS THE CWA.

THE MID WEEK PERIOD SHOULD BE MAINLY DRY WITH HIGH PRESSURE DRIFTING
THROUGH...BUT TEMPS SHOULD BE WELL BELOW NORMAL.  NIGHTTIME LOWS
WILL BE 25 TO 30...WITH DAYTIME HIGHS ONLY IN THE UPPER 30S TO MID
40S.

WE SHOULD MODERATE TEMPS SLIGHTLY INTO THURSDAY AND FRIDAY AS WE GET
ON THE BACKSIDE OF THE HIGH...ALTHOUGH WE SHOULD STILL REMAIN BELOW
NORMAL.  THE MEDIUM RANGE MODELS SHOW A FRONT COMING THROUGH
THURSDAY NIGHT OR FRIDAY...SO WILL CARRY LOW POPS FOR THIS.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z SATURDAY EVENING)
ISSUED AT 656 PM EDT FRI APR 11 2014

VFR CONDITIONS ARE EXPECTED INTO MID AFTERNOON SATURDAY. DURING THE
LATE AFTERNOON A SURGE OF WARMER AND MORE MOIST AIR WILL LIKELY
SET OFF SOME THUNDERSTORMS AND HAVE A GOOD CHANCE OF IMPACTING THE
MKG AND GRR TAF SITES AFTER 21Z. WINDS WILL BECOME SOUTHERLY AND INCREASE
TO 15 TO 25 KNOTS SATURDAY AFTERNOON ONCE THE WARM FRONT MOVES
NORTH OF THE TAF SITES EARLY IN THE AFTERNOON.

&&

.FIRE WEATHER...
ISSUED AT 337 PM EDT FRI APR 11 2014

VERY DRY AIR EXISTS THIS AFTERNOON...WITH RH VALUES DIPPING BELOW 25
PERCENT AND SOME WIND GUSTS UP AROUND 20 MPH. TEMPERATURES ARE STILL
ON THE COOL SIDE THROUGH FOR FIRE WX CONCERNS...HOLDING IN THE 60S.

AN ELEVATED FIRE DANGER MAY COME TOGETHER SATURDAY MORNING INTO
SATURDAY AFTERNOON AS SOME OF THE DRY AIR WILL LINGER FOR A TIME
BEFORE WE MOISTEN UP AND BRING RAIN INTO THE AREA. TEMPERATURES WILL
MAKE A RUN INTO THE LOWER 70S SATURDAY AFTERNOON ACROSS SOUTHERN
LOWER MICHIGAN...TOWARDS I94. RH VALUES WILL AT LEAST DIP INTO THE
30-40 PCT RANGE IF NOT LOWER. GUSTY SOUTH WINDS OF 15-25 MPH MAY BE
IN PLACE FOR A GOOD PORTION OF THE MID MORNING TO LATE AFTERNOON
HOURS. SO...WE WILL NEED TO KEEP A CLOSE EYE ON METEOROLOGICAL
CONDITIONS AS WE MAY COME CLOSE TO RED FLAG CONDITIONS. THE MAIN
AREA OF CONCERN WOULD BE FROM INTERSTATE 96 TO THE SOUTH ON
SATURDAY. THAT SAID...ALL AREAS HAVE FINE FUEL MOISTURE CODE VALUES
THAT ARE A CONCERN AROUND 90 TO THE LOWER 90S. HIGH PROBABILITIES OF
SPOT FIRES START AROUND 90 WITH EXTREME FIRE BEHAVIOR STARTING AT
91.

&&

.HYDROLOGY...
ISSUED AT 337 PM EDT FRI APR 11 2014

HAVE OPTED TO ISSUE A FLOOD WATCH FOR ESSENTIALLY THE NORTHWEST HALF
OF THE FORECAST AREA...OR FROM ALLEGAN...KENT...IONIA AND GRATIOT
COUNTIES NORTHWARD. CONFIDENCE IS INCREASING IN A HEAVY RAIN EVENT
AT LEAST ACROSS THE NORTHWEST WEST HALF OF THE CWA. THE HEAVIEST
RAIN WILL LIKELY FALL ACROSS CENTRAL LOWER MICHIGAN...BUT THERE IS
STILL SOME ZEROING IN THAT WILL LIKELY OCCUR OVER THE COURSE OF THE
NEXT FEW SHIFTS. DECIDED THERE WAS ENOUGH CONFIDENCE TO GO WITH A
WATCH GIVEN MULTIPLE RUNS FROM MULTIPLE MODELS INDICATING 2 PLUS
INCHES OF RAIN ACROSS OUR NORTHERN CWA.

SETUP FOR HEAVY RAIN INCLUDES A STATIONARY BOUNDARY THAT LOOKS TO
SET UP ACROSS THE CWA WITH WAVES OF LOW PRESSURE AND UPPER LEVEL
DISTURBANCES RUNNING ALONG IT. THIS WILL BE OUR FIRST EVENT OF THE
YEAR THAT WILL LIKELY CONTAIN EMBEDDED THUNDERSTORMS AS WELL.
PRECIPITABLE WATER VALUES ARE ON THE ORDER OF 1.3 INCHES NEAR THE
FRONTAL ZONE WHICH IS RUNNING NEAR THE 99TH PERCENTILE. EXPECTING
REPEATED ROUNDS OF SHOWERS AND EMBEDDED STORMS FROM SATURDAY
AFTERNOON RIGHT INTO MONDAY. THE HEAVIEST MAY FALL SUNDAY AFTERNOON
INTO SUNDAY NIGHT AS THE MAIN UPPER DISTURBANCE MOVES THROUGH THE
AREA.

ANTECEDENT CONDITIONS ARE RIPE FOR FLOODING WITH GROUND MOISTURE
BEING HIGH WHICH WILL LEAD TO EFFICIENT RUN OFF. EARLIER RAINS AND
SNOWMELT HAVE AREA RIVERS RUNNING ABOVE NORMAL FOR THIS TIME OF
YEAR.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...FLOOD WATCH FROM SATURDAY AFTERNOON THROUGH MONDAY MORNING FOR
     MIZ037>040-043>046-050>052-056>058-064.

LM...NONE.
&&

$$

SYNOPSIS...DUKE
SHORT TERM...DUKE
LONG TERM...JK
AVIATION...WDM
FIRE WEATHER...DUKE
HYDROLOGY...DUKE






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