701
FXUS63 KGRR 161717
AFDGRR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
1217 PM EST MON DEC 16 2024
KEY MESSAGES
- CLOUDY AND DAMP MONDAY
- LIGHT SNOW WEDNESDAY AND THURSDAY NIGHT TO FRIDAY
UPDATE
ISSUED AT 929 AM EST MON DEC 16 2024
THE WEBCAMS ALONG THE LAKESHORE SHOWED THICK FOG OVER LAKE
MICHIGAN. THE LATEST HIGH RES MODEL DATA INDICATES A RISK FOR FOG
INTO THE AFTERNOON WITH CONDITIONS IMPROVING BY EVENING. WE ISSUED
A MARINE DENSE FOG ADVISORY AS A RESULT.
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 /18Z TAFS THROUGH 18Z TUESDAY/
ISSUED AT 1216 PM EST MON DEC 16 2024
LIFR CONDITIONS ARE LIKELY THIS AFTERNOON AS ABUNDANT LOW-LEVEL
MOISTURE LEADS TO LOW CIGS AND AREAS OF FOG, WITH VISBYS DOWN TO
1/2 MILE AT TIMES. LIFR CONDITIONS CONTINUE THROUGH THIS EVENING
WHEN A FRONT CROSSING THE AREA CLEARS OUT SOME OF THE LOW-LEVEL
MOISTURE. FOG DISSIAPTES AND CIGS RISE TO IFR AND THEN MVFR THIS
EVENING BEHIND THE FRONT WITH MVFR CIGS AREAWIDE OVERNIGHT TONIGHT
INTO TUESDAY AFTERNOON. GUSTY WEST WINDS ARE ALSO EXPECTED WITH
10-15 KNOT WINDS GUSTING TO 15 KNOTS EXPECTED OVER THE TAF PERIOD.
GRR WATCHES/WARNINGS/ADVISORIES
MI...NONE.
MARINE...DENSE FOG ADVISORY UNTIL 7 PM EST THIS EVENING FOR LMZ844>849.
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.
UPDATE...MJS
DISCUSSION...CAS
AVIATION...THOMAS
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