154
FXUS63 KGRR 161120
AFDGRR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
620 AM EST MON DEC 16 2024
KEY MESSAGES
- CLOUDY AND DAMP MONDAY
- LIGHT SNOW WEDNESDAY AND THURSDAY NIGHT TO FRIDAY
DISCUSSION
ISSUED AT 320 AM EST MON DEC 16 2024
- CLOUDY AND DAMP MONDAY
INCREASING WINDS AT 1000 TO 2000 FEET HAVE MIXED AWAY THE DENSE
FOG IN MOST AREAS BUT LOW STRATUS CLOUDS REMAIN. THERE IS A HIGH
LIKELIHOOD OF LIGHT RAIN SHOWERS FOR SEVERAL HOURS AFTER 7 AM WITH
MIDLEVEL MOISTURE ADVECTION AND ISENTROPIC ASCENT OCCURRING AHEAD
OF THE NEXT LOW PRESSURE SYSTEM NEAR THE BOUNDARY WATERS OF
NORTHERN MINNESOTA. MEDIUM RANGE GUIDANCE IS UNANIMOUS THAT TODAY
WILL BE THE MILDEST DAY FOR THE REST OF THE WEEK. THERE MAY BE A
PERIOD OF FOG AND DRIZZLE AGAIN THIS AFTERNOON AS THE MIDLEVELS
DRY OUT AND WINDS BELOW 2000 FEET RELAX SOMEWHAT. ANY FOG SHOULD
MIX OUT LATER IN THE EVENING AFTER COLD FRONTAL PASSAGE, BUT VERY
LIGHT RAIN SHOWERS MAY CONTINUE THROUGH THE NIGHT, POSSIBLY
CHANGING TO SNOW IN CENTRAL MICHIGAN.
- LIGHT SNOW WEDNESDAY AND THURSDAY NIGHT TO FRIDAY
THE WEATHER REMAINS RATHER UNSETTLED THROUGH THE WEEK AS A SERIES
OF SHORTWAVE TROUGHS CONTINUES ITS PROGRESSION ACROSS THE
NORTHERN US. ON WEDNESDAY THERE MAY BE LIGHT SNOW ACCUMULATION,
THOUGH THE DEGREE OF PHASING BETWEEN THE TWO RESPONSIBLE WAVES
(ONE FROM NEAR THE WASHINGTON COAST, THE OTHER FROM NEAR THE
NORTHWEST CANADIAN TERRITORIES) IS THE DIFFERENCE BETWEEN A
DUSTING AND A COUPLE INCHES OF SNOW. TEMPERATURES MAY BE ON THE
MARGINALLY WARM SIDE ALSO, ESPECIALLY IN SOUTHERN MICHIGAN.
THERE IS A LITTLE HIGHER POTENTIAL FOR MINOR IMPACTS FROM
ACCUMULATING SNOW LATE THURSDAY INTO FRIDAY, AS THE NEXT UPPER-
LEVEL SHORTWAVE AND A BETTER DEVELOPED LOW-LEVEL CIRCULATION MOVE
THROUGH. THE MAJORITY OF ENSEMBLE MEMBERS PROVIDE AREAS NEAR AND
NORTH OF GRAND RAPIDS WITH AT LEAST AN INCH OF SNOW, AND A FEW
INCHES IS PLAUSIBLE. A MORE AMPLIFIED WAVE PATTERN LATER IN THE
WEEK IS FAVORED TO SEND A BRIEF SHOT OR GLANCING BLOW OF MODIFIED
ARCTIC AIR THROUGH THE GREAT LAKES OVER THE WEEKEND, WHICH WOULD
FAVOR LAKE EFFECT SNOW TO LINGER THROUGH THE WEEKEND IN AREAS NEAR
THE SHORE.
AVIATION /12Z TAFS THROUGH 12Z TUESDAY/
ISSUED AT 620 AM EST MON DEC 16 2024
LIFR TO IFR CONDITIONS WILL REMAIN THROUGHOUT THE DAY. RAIN IS
EXPECTED THIS MORNING WITH SOME DRIZZLE POSSIBLE DURING THE
AFTERNOON. CEILINGS AND VISIBILITIES SHOULD IMPROVE THIS EVENING
BEHIND THE FRONT AT LEAST TO MVFR VALUES.
GRR WATCHES/WARNINGS/ADVISORIES
MI...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 4 PM THIS AFTERNOON TO 7 PM EST
TUESDAY FOR LMZ844>847.
SMALL CRAFT ADVISORY UNTIL 7 PM EST TUESDAY FOR LMZ848-849.
DISCUSSION...CAS
AVIATION...RAH
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