393
FXUS63 KGRR 180535
AFDGRR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
1235 AM EST WED DEC 18 2024
KEY MESSAGES
- A PERIOD OF LIGHT SNOW/RAIN FOR LATER TONIGHT INTO WEDNESDAY
MORNING
- INCREASING RISK FOR IMPACTS THURSDAY AFTERNOON INTO FRIDAY MORNING
- VERY COLD OVER THE WEEKEND
UPDATE
ISSUED AT 1000 PM EST TUE DEC 17 2024
SOUTHWEST LOWER MICHIGAN WILL BE IN A WEAK PRESSURE GRADIENT
TONIGHT WITH A COL LOCATED DIRECTLY OVER THE AREA. SO, MUCH
LIGHTER WINDS TONIGHT AS COMPARED TO LAST NIGHT. ALOFT, A
SHORTWAVE WILL APPROACH THE AREA FROM THE WEST TONIGHT. THIS WAVE
IS ALSO ASSOCIATED WITH A UPPER LEVEL JET STREAK WHICH WILL
PROVIDE SOME RIGHT ENTRANCE REGION LIFT OVERNIGHT. PRECIPITATION
IS OCCURRING UPSTREAM OVER MINNESOTA AND IOWA ASSOCIATED WITH THE
UPPER WAVE AND JET STREAK. THE FORCING AND PRECIPITATION WILL
SLIDE EAST INTO SOUTHERN LOWER MICHIGAN OVERNIGHT. TEMPERATURES
WILL BE MARGINAL (32F TO 33F) WITH SOME LIGHT RAIN AND SNOW
DEVELOPING OVERNIGHT. AT THIS POINT WE FEEL ANY SNOW ACCUMULATION
WILL BE LIGHT THROUGH DAYBREAK. A NARROW BAND OF LIGHT SNOW IS
POSSIBLE FROM HOLLAND AND SOUTH HAVEN EAST INTO GRAND RAPIDS AND
HASTINGS. ACCUMULATIONS THROUGH THE MORNING COMMUTE SHOULD BE A
COUPLE OF A TENTHS OF AN INCH OR LESS.
DISCUSSION
ISSUED AT 238 PM EST TUE DEC 17 2024
- A PERIOD OF LIGHT SNOW/RAIN FOR LATER TONIGHT INTO WEDNESDAY
MORNING
THE MID LEVEL WAVE IN THE UPPER PLAINS MOVES INTO THE CWA LATER
TONIGHT. AT THE SAME TIME A SURFACE WAVE WILL BE TRACKING UP THE OH
VALLEY. MOISTURE PROFILES SHOW THE DGZ MOISTENING UP LATER TONIGHT BUT
THE LOW LEVELS WILL INITIALLY BE DRY. THEN AS THE LOW LEVELS
MOISTEN UP, THE DGZ STARTS TO DRY OUT. THE LIFT THROUGH THE
COLUMN IS SHOWN TO BE RELATIVELY WEAK. AS A RESULT, WE WILL CARRY
HIGH POPS FOR THIS SHORT DURATION EVENT, BUT AT THIS TIME IT
APPEARS THAT QPF WILL BE LIGHT. ALSO, SURFACE TEMPERATURES MAY
STRUGGLE TO FALL BELOW FREEZING, ESPECIALLY AS INDICATED BY THE
HRRR. BASED ON THIS, AT THIS TIME, ANY IMPACTS SHOULD REMAIN
LIMITED. NO HEADLINES FOR THIS EVENT.
- INCREASING RISK FOR IMPACTS THURSDAY AFTERNOON INTO FRIDAY MORNING
THE NEXT MID LEVEL WAVE WILL BE DIGGING INTO THE GREAT LAKES REGION
FROM THE CANADIAN PRAIRIES DURING THIS TIME. FGEN WAS NOTED IN THE
700-600 MB LEVEL, ESPECIALLY OVER CENTRAL/SOUTHERN PARTS OF THE
CWA. MID LEVEL LAPSE RATES DO STEEPEN UP AS WELL. MOISTURE
PROFILES REFLECT DEEP MOISTURE FROM ABOUT MID AFTERNOON THURSDAY
INTO FRIDAY MORNING. INITIALLY THE LOW LEVELS ARE SHOWN TO BE DRY
BUT THAT LEVEL SATURATES FAIRLY QUICKLY. AS A RESULT, THE REGION
IS LOOKING AT AN EXTENDED PERIOD OF SNOW. THIS SYSTEM WILL BE
COLDER SO, MUCH OF THE EVENT WILL FEATURE SURFACE TEMPS AT OR
BELOW FREEZING. BASED ON ALL THIS, IMPACTS WILL BE GREATER WITH
THIS SECOND SYSTEM AND THEY COULD RISE TO A HEADLINE LEVEL.
HOWEVER, ENSEMBLE MEAN SNOW AMOUNTS SUGGEST MOST LOCATION WILL END
UP WITH AN INCH OR TWO DURING THIS PERIOD FOR MOST OF THE CWA. IT
SHOULD BE NOTED THAT THERE IS STILL A LOT OF SPREADS AMONGST THE
MEMBERS, SO THERE STILL EXISTS A DECENT AMOUNT OF UNCERTAINTY WITH
THE SNOW AMOUNTS.
- VERY COLD OVER THE WEEKEND
AN ARCTIC HIGH PRESSURE SYSTEM GRADUALLY BUILDS IN FROM THE
NORTHWEST OVER THE WEEKEND. MOST OF THE TIME AN OFFSHORE COMPONENT
TO THE FLOW WILL BE PRESENT AND THAT WILL FOCUS THE BULK OF LAKE
EFFECT SNOW WEST OF THE CWA. SOME INLAND CLEARING IS LOOKING
LIKELY SATURDAY NIGHT AS THE COLDER AIR DRAINS TOWARDS LAKE MI.
THE COMBINATION OF CLEARING SKIES, WEAKER WINDS AND ARCTIC AIR
MASS IN PLACE AND FRESH SNOW COVER, SUPPORTS VERY COLD LOW
TEMPERATURES SATURDAY NIGHT, AND POSSIBLY SUNDAY NIGHT.
CONSERVATIVE ESTIMATES ARE FOR THE SINGLE DIGITS AND THEY COULD GO
LOWER AS WE GET CLOSER TO THAT TIME.
AVIATION /06Z TAFS THROUGH 06Z THURSDAY/
ISSUED AT 1235 AM EST WED DEC 18 2024
MVFR CONDITIONS CONTINUE WITH LIGHT SNOW MOVING INTO THE AREA
MAINLY AFTER 9Z AND LINGERING UNTIL AROUND 15Z. MKG MAY BE ON THE
EDGE OF THE MORNING SNOW, WITH AMOUNTS AT THE OTHER TAF SITES
AROUND A HALF AN INCH THROUGH THE MORNING HOURS. IFR VISIBILITIES
AND CEILINGS ARE POSSIBLE WITHIN THE MORNING SNOW. WITH THE COLD
FRONT MOVING THROUGH THIS MORNING, WINDS WILL BECOME MORE
NORTHWESTERLY WITH ADDITIONAL LIGHT SNOW SHOWERS POSSIBLE DURING
THE EVENING. WIND GUSTS AROUND 20 KNOTS WILL ALSO BE POSSIBLE
DURING THE LATE AFTERNOON AND EVENING.
GRR WATCHES/WARNINGS/ADVISORIES
MI...NONE.
MARINE...NONE.
UPDATE...DUKE
DISCUSSION...MJS
AVIATION...RAH
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