Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 242030
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
330 PM EST WED DEC 24 2014

LATEST UPDATE...
SYNOPSIS/SHORT TERM/LONG TERM/HYDRO/MARINE

.SYNOPSIS...
ISSUED AT 330 PM EST WED DEC 24 2014

STRENGTHENING LOW PRESSURE OVER NORTHWEST OHIO WILL MOVE RAPIDLY
NORTH INTO ONTARIO TONIGHT. RAIN WILL MIX WITH OR CHANGE TO WET SNOW
THIS EVENING BEFORE ENDING OVERNIGHT. WET SLUSHY SNOW ACCUMULATIONS
MAY IMPACT TRAVEL TONIGHT... MAINLY NORTH OF INTERSTATE 96 AND EAST
OF HIGHWAY 131. TEMPERATURES WILL REMAIN MILD THROUGH SUNDAY BUT
THEN A COOL DOWN WILL TAKE PLACE NEXT WEEK.

&&

.SHORT TERM...(THIS EVENING THROUGH FRIDAY)
ISSUED AT 330 PM EST WED DEC 24 2014

HAVE MADE SOME ADDITIONAL ADJUSTMENTS TO THE WINTER WEATHER ADVISORY
TO ACCOUNT FOR THE FARTHER EAST AND WEAKER SFC LOW TRACK AS WELL AS
A QUICKER DEPARTURE OF PRECIPITATION. HAVE CANCELED THE WESTERN AND
SOUTHERN PORTIONS OF THE ADVISORY INCLUDING THE LAKE MICHIGAN
SHORELINE AND AREAS SOUTH OF GRR...BUT HAVE ADDED A FEW MORE
COUNTIES IN MID MICHIGAN TO INCLUDE THE ALMA/ST JOHNS AREAS. HAVE
ALSO SHORTENED THE EFFECTIVE TIME AND IT WILL NOW END AT MIDNIGHT.
WILL CUT BACK A TAD ON ACCUMS TOO.

PRECIPITATION REMAINS PRIMARILY RAIN AT 3 PM ALTHOUGH GUIDANCE ALL
ALONG HAS BEEN SUGGESTING THIS. AS THE UPPER TROUGH GOES NEGATIVELY
TILTED THIS EVENING AND THE UPR LOW PASSES OVERHEAD IT SEEMS
REASONABLE TO BELIEVE PRECIP WILL TREND TOWARD MOSTLY SNOW FOR A
TIME THIS EVENING DUE TO DYNAMIC COOLING ALONG WITH HEAVIER PRECIP
RATES. ALSO AS THE SFC LOW CONTINUES LIFTING NORTH AND DEEPENING...
THIS WILL DRAW SLIGHTLY COLDER AIR IN FROM THE WEST. HOWEVER ALL OF
THESE THINGS OCCUR OVER A RELATIVELY SHORT PERIOD BETWEEN ROUGHLY 5
PM AND 11 PM...BUT SOME FAIRLY HEAVY WET SNOW MAY FALL DURING THIS
TIME.

IT WAS TEMPTING TO CANCEL THE WINTER WEATHER ADVISORY ALTOGETHER AS
HAS BEEN THE TREND UPSTREAM... BUT WOULD RATHER GIVE THE FORECAST A
CHANCE TO WORK. THERE ARE SOME ENCOURAGING TRENDS CURRENTLY SUCH AS
COOLING CLOUD TOPS OVERHEAD ON THE IR SATELLITE LOOP AND INCREASING
INTENSITY OF RADAR ECHOES WITH A BANDED NATURE. ALSO THERE ARE SOME
LIGHTNING STRIKES NOW SHOWING UP OVER WRN OHIO IMPLYING THERE WILL
BE A CONVECTIVE NATURE TO THE PRECIP AS THE EVENT EVOLVES.

PRECIP TYPE WILL PROBABLY GO BACK TO A LIGHT MIX OF RAIN AND SNOW
AFTER MIDNIGHT OR END AS DEEPER MOISTURE BAILS OUT AND DGZ WILL NO
LONGER BE SATURATED. REST OF SHORT TERM PERIOD LOOKS QUIET.

.LONG TERM...(FRIDAY NIGHT THROUGH WEDNESDAY)
ISSUED AT 330 PM EST WED DEC 24 2014

THE LONG TERM PORTION OF THE FCST IS LOOKING RELATIVELY BENIGN BY
LATE DEC STANDARDS FOR LOWER MICHIGAN. WE ARE LOOKING AT A GRADUAL
TREND TOWARD MORE DEC LIKE TEMPS...HOWEVER THE ARCTIC COLD THAT HAS
BEEN SHOWN FOR THE LAST COUPLE OF DAYS LOOKS LIKE IT MAY BE DELAYED
OR TEMPERED A BIT.

WE WILL SEE THE CHC FOR PCPN INCREASE DURING THE FRI NIGHT AND SAT
TIME FRAME FOR THE AREA. A STRONG WAVE CURRENTLY MOVING ONSHORE OVER
NRN CA THIS AFTERNOON WILL DIG INTO THE FOUR CORNERS REGION AND THEN
LIFT NE FRI NIGHT/SAT. A LACK OF COLD AIR BEHIND THE ONGOING SYSTEM
AND STRENGTHENING SRLY FLOW AHEAD OF THE NEXT SYSTEM WILL ALLOW MOST
OF THE PCPN TO BE MAINLY RAIN. THERE COULD BE SOME SHORT DURATION
P-TYPE ISSUES UP NORTH FRI NIGHT WITH TEMPS MARGINAL.

WE WILL SEE A COUPLE OF CHCS FOR PCPN FROM THE SUN NIGHT THROUGH TUE
TIME FRAME. THE CHCS WILL NOT BE VERY GOOD CHCS OF PCPN. THERE WILL
BE AN ARCTIC FRONT TRYING TO DROP SOUTH THROUGH THE AREA SUN NIGHT
AND MON WITH A NRN STREAM WAVE MOVING ACROSS CANADA. THE FRONT LOOKS
TO GET STUCK NORTH OF THE AREA AS IT BECOMES NEARLY PARALLEL TO THE
UPPER FLOW. NOT MUCH MOISTURE ASSOCIATED WITH IT.

IN ADDITION...A WAVE MOVES OUT FROM THE ROCKIES TRYING TO BRING PCPN
ON TUE. THIS WAVE WILL DAMPEN OUT AS ANOTHER STRONG TROUGH DIGS
ACROSS THE WRN STATES AND A RIDGE BUILDS OVER OUR AREA AHEAD OF THE
WRN TROUGH. INVERSION HTS REMAIN RATHER LOW AND MOISTURE IS RATHER
SHALLOW. THIS IS IN ADDITION TO MARGINAL OVER-LAKE INSTABILITY WILL
BRING ONLY A LOW CHC OF SOME LAKE EFFECT SNOW SHOWERS ALSO.

WE WILL EVENTUALLY SEE THE WRN LOW EJECT OUT AND AFFECT THE AREA. AT
THIS TIME...IT SEEMS THAT IT WILL TAKE UNTIL AFTER THIS FCST PERIOD
FOR THE AREA TO SEE THE AFFECTS FROM IT.


&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z THURSDAY AFTERNOON)
ISSUED AT 1257 PM EST WED DEC 24 2014

MAIN CHALLENGES OF THE 18Z FCSTS ARE THE CIGS AND PRECIPITATION TYPE
TRENDS FOR EACH OF THE SITES. RAIN WITH IFR AND LOWER CONDITIONS ARE
THE DOMINANT CONDITIONS ACROSS THE AREA EARLY THIS AFTERNOON. THERE
IS A BRIEF BREAK IN THE IFR CONDITIONS AND RAIN ACTIVITY SOUTH OF
KMKG AND NEAR AND WEST OF KGRR. THE IFR CONDITIONS WILL MOVE BACK
INTO KGRR AND KMKG IN THE NEXT COUPLE OF HOURS WHILE THE OTHER SITES
REMAIN IFR AND LOWER. THE IFR WILL CONTINUE THROUGH 06-08Z WHEN PCPN
STARTS MOVING OUT. CONDITIONS WILL THEN BECOME MVFR AND LIKELY LAST
THROUGH 18Z THU.

WITH REGARDS TO THE PCPN...THE CURRENT RAIN IS EXPECTED TO DOMINATE
UNTIL ABOUT 02-03Z WHEN COLD ENOUGH AIR MOVES IN TO CHANGE
EVERYTHING OVER TO SNOW. WE ARE EXPECTING THAT AS SOME HEAVIER
BURSTS OF PCPN MOVE THROUGH...THE RAIN WILL MIX WITH OR EVEN CHANGE
OVER TO SNOW FOR A SHORT TIME PRIOR TO THE 02-03Z CHANGEOVER.

WINDS WILL BECOME GUSTY THIS EVENING FROM THE WEST WITH SOME GUSTS
UP AROUND 20-25 KNOTS LIKELY.

&&

.MARINE...
ISSUED AT 330 PM EST WED DEC 24 2014

NO CHANGES NEEDED TO THE MARINE FCST AND HEADLINES. IT APPEARS WE
WILL SEE MAX SMALL CRAFT ADVISORY CONDITIONS TONIGHT THROUGH
CHRISTMAS NIGHT. THE ADVISORY MAY BE NEEDED TO BE EXTENDED
EVENTUALLY...HOWEVER WE HAVE IT OUT THROUGH THREE PERIODS NOW WHICH
IS SUFFICIENT FOR THE TIME BEING.

&&

.HYDROLOGY...
ISSUED AT 330 PM EST WED DEC 24 2014

RIVER FLOOD ADVISORIES ARE IN EFFECT AT THE GRAND RIVER AT IONIA...
SYCAMORE CREEK AT HOLT...THE MAPLE RIVER AT MAPLE RAPIDS... AND THE
LOOKING GLASS RIVER AT EAGLE...

ALL OF THESE SITES ARE EXPECTED TO CREST JUST ABOVE BANKFULL OVER
THE NEXT COUPLE DAYS WITH MINOR LOWLAND FLOODING. THE PRECIPITATION
THAT IS DRIVING THESE RISES IS ALREADY UNDERWAY. SO FAR WE HAVE SEEN
A QUARTER TO HALF AN INCH ACROSS THE ENTIRE AREA. AS MUCH AS AN
ADDITIONAL THREE QUARTERS OF AN INCH WILL BE POSSIBLE...PARTICULARLY
ACROSS THE EASTERN GRAND AND KALAMAZOO/ST JOE RIVER BASINS.

NO SIGNIFICANT PRECIPITATION IS EXPECTED AFTER TONIGHT. THEREFORE NO
SECONDARY CRESTS ARE EXPECTED AT THIS TIME.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...WINTER WEATHER ADVISORY UNTIL MIDNIGHT EST TONIGHT FOR
     MIZ038>040-044>046-051-052-057>059.

LM...SMALL CRAFT ADVISORY UNTIL 7 AM EST FRIDAY FOR LMZ844>849.

&&

$$

SYNOPSIS...MEADE
SHORT TERM...MEADE
LONG TERM...NJJ
AVIATION...NJJ
HYDROLOGY...TJT
MARINE...MEADE








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