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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS63 KGRR 252029
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
329 PM EST SUN JAN 25 2015

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

.SYNOPSIS...
ISSUED AT 328 PM EST SUN JAN 25 2015

FAIR WEATHER WILL PREVAIL THROUGH MONDAY. SOME LIGHT SNOW IS
POSSIBLE MONDAY NIGHT AND TUESDAY BUT SHOULD NOT AMOUNT TO MUCH.
A CLIPPER WILL BRING A CHANCE OF SNOW OR MIXED PRECIPITATION
WEDNESDAY NIGHT AND THURSDAY.

&&

.SHORT TERM...(THIS EVENING THROUGH TUESDAY NIGHT)
ISSUED AT 328 PM EST SUN JAN 25 2015

ONLY FORECAST ISSUES IN THE NEAR TERM ARE FOR THE EXTENT OF LIGHT
SNOW MONDAY NIGHT AND P TYPE ISSUES WEDNESDAY NIGHT.

SHALLOW ARCTIC AIR MASS WILL BE IN PLACE TONIGHT AND EXPECT
CLEARING TO WORK SOUTH THIS EVENING AS STRONG CAA CONTINUES, DEW
POINTS ARE NEAR ZERO ACROSS NORTHERN LOWER MICHIGAN THIS AFTERNOON
AND THIS VERY DRY AIR WILL BE MOVING SOUTH. EXPECT LOWS IN THE
SINGLE NUMBERS BY DAYBREAK IN MOST PLACES.

UPPER TROUGH AMPLIFIES AND GOES NEGATIVE TILT TONIGHT THEN CLOSES
OFF ON MONDAY AS BIG NOREASTER HITS NEW ENGLAND. A COUPLE OF QUICK
MOVING VORT MAXES ARE PROGGED TO MOVE ACROSS LOWER MICHIGAN MONDAY
NIGHT AS WEAK SHORTWAVE TROUGHS HELP FURTHER ENERGIZE THE LARGER
SCALE TROUGH. THESE COULD PROVIDE ENOUGH LIFT TO PRODUCE SOME
LIGHT SNOW...BUT IT SHOULD BE FAIRLY LIGHT AS SYNOPTIC FORCING IS
WEAK.

THE NEXT CLIPPER ARRIVES WEDNESDAY NIGHT. THERE IS GOOD AGREEMENT
WITH TRACK AND TIMING IN THE 12Z GUIDANCE...THOUGH THE ECMWF IS A
BIT WARMER THAN THE GFS. LOOKS LIKE MIXED PRECIP TO START OFF WITH
WEDNESDAY EVENING ACROSS THE SOUTHERN HALF OF THE FORECAST AREA
GOING OVER TO MORE SNOW LATER WEDNESDAY NIGHT PER THICKNESS TOOLS
AND MODEL SOUNDINGS.

.LONG TERM...(WEDNESDAY THROUGH SUNDAY)
ISSUED AT 328 PM EST SUN JAN 25 2015

THE FOCUS OF THE LONG TERM PORTION OF THE FCST IS ON A COUPLE OF
CLIPPER SYSTEMS CENTERED AROUND WED NIGHT/THU AND ON SAT. THESE
COULD EACH BRING SOME ACCUMULATING SNOW TO THE AREA. THE SAT CLIPPER
COULD END UP USHERING IN A PRETTY GOOD SURGE OF ARCTIC AIR ACROSS
THE AREA.

THE FIRST CHC OF PCPN WILL COME IN WED NIGHT AND THU WITH A CLIPPER
SYSTEM EXPECTED TO MOVE ACROSS THE REGION. WE WILL SEE THE LONG WAVE
RIDGE SET UP ACROSS THE WRN STATES AND WE WILL BE UNDER THE
INFLUENCE OF THE LONG WAVE TROUGH ESTABLISHED ACROSS THE EAST. ONE
OF THE WAVES RIDING IN IS EXPECTED TO GO JUST SOUTH OF THE STATE.
THIS LOOKS LIKE MAINLY LIGHT SNOW WITH SOME ACCUMULATIONS. HOWEVER
IF THE SYSTEM TRACKS MUCH FURTHER NORTH...WE COULD SEE A WINTRY MIX
WITH WARM ENOUGH ALOFT COMING IN.

WE WILL SEE A BREAK IN THE WEATHER THEN FOR THU NIGHT THROUGH FRI
NIGHT AS SOME SHORT WAVE RIDGING BUILDS IN ACROSS THE AREA. SOME
LAKE EFFECT SNOW SHOWERS WILL BE POSSIBLE FOR NNW FLOW AREAS.
HOWEVER THE RIDGE WILL LIMIT THE DEPTH OF THE INVERSION AND
MOISTURE...SO NO SIGNIFICANT LAKE EFFECT IS EXPECTED THEN.

THE NEXT SYSTEM WILL THEN BRING THE NEXT CHC OF SNOW TO THE AREA
DURING THE DAY ON SAT. THE MODELS HAVE GENERALLY SHOWN THIS WAVE
COMING THROUGH ON SAT AND DRAGGING A NICE CHUNK OF ARCTIC AIR BEHIND
IT. WE WILL CONTINUE WITH THIS THOUGHT EVEN WITH AN OUTLIER
APPEARING IN THE 12Z MODEL SUITE BRINGING WARMER AIR TO THE AREA. WE
ARE BEING SOMEWHAT CONSERVATIVE WITH THE COLD AIR BEHIND THE SYSTEM
AT THIS TIME.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z MONDAY AFTERNOON)
ISSUED AT 1236 PM EST SUN JAN 25 2015

LIGHT SNOW THAT HAS BEEN AFFECTING THE I-94 TERMINALS THIS MORNING
AND EARLY AFTERNOON WILL GRADUALLY MOVE OUT THIS AFTERNOON AND
CONDITIONS WILL GENERALLY IMPROVE. WE EXPECT MAINLY MVFR
CONDITIONS WITH SOME PATCHY IFR EMBEDDED IN THE LIGHT SNOW.

OTHERWISE...NRN AREAS ARE MAINLY VFR RIGHT NOW. SOME LAKE EFFECT
CLOUD COVER FROM LAKE HURON BASED AROUND 2000-2500 FT IS AFFECTING
KLAN AND KAMN AREAS. KGRR RADAR IS SHOWING SOME OF THIS
APPROACHING THE KGRR TERMINAL. THIS MVFR DECK WILL LINGER AROUND
AT KLAN AND KGRR THROUGH MOST OF THE AFTERNOON BEFORE IT
DIMINISHES AS WINDS DIMINISH THIS EVENING.

ONCE THE MVFR CONDITIONS MOVE OUT THIS EVENING...WE ONLY EXPECT
SOME MID/HIGH CLOUD COVER THEN THROUGH THE END OF THE FCST PERIOD.


&&

.HYDROLOGY...
ISSUED AT 328 PM EST SUN JAN 25 2015

MOST RIVERS ARE HOLDING STEADY OR DROPPING. COLD TEMPERATURES
FOR THE COMING WEEK WILL KEEP THE ICE LOCKED UP. CURRENTLY NO
SUSPECTED ICE JAMS IN THE AREA... BUT WILL CONTINUE MONITORING FOR
ANY THAT DO DEVELOP. SERIOUS ICE JAMS AND FLOODING CONCERNS ARE
UNLIKELY UNTIL A SIGNIFICANT WARM UP AND RAINFALL.

&&

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

$$

SYNOPSIS...OSTUNO
SHORT TERM...OSTUNO
LONG TERM...NJJ
AVIATION...NJJ
HYDROLOGY...CAS