112
FXUS63 KAPX 210743
AFDAPX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GAYLORD MI
243 AM EST SAT DEC 21 2024
KEY MESSAGES
- BRIEF VERY COLD SPELL TODAY INTO TONIGHT, WITH HIGHS IN THE
TEENS TODAY, AND POTENTIAL FOR SUB-ZERO LOWS TONIGHT.
- POTENTIAL IS INCREASING FOR A WIDESPREAD SNOWFALL LATE SUNDAY
NIGHT THROUGH MONDAY EVENING AS ANOTHER SYSTEM PASSES THROUGH
THE REGION.
- TRENDING WARMER AND DRIZZLY FOR THE REMAINDER OF THE FORECAST
PERIOD, INCLUDING THE CHRISTMAS HOLIDAY. SNOWPACK LIKELY
ERODES SUBSTANTIALLY AS TEMPERATURES AND DEWPOINTS BECOME
STAGNANT ABOVE FREEZING.
SHORT TERM /THROUGH TONIGHT/
ISSUED AT 240 AM EST SAT DEC 21 2024
PATTERN SYNOPSIS AND FORECAST:
LONGWAVE TROUGHING WILL SLIDE EASTWARD AS HIGH PRESSURE WITH
ARCTIC ORIGINS BUILDS IN THROUGH TONIGHT. DRIER AIR TRACKING
INTO THE REGION WILL WORK TO SCOUR OUT LOW-LEVEL MOISTURE WHILE
GRADIENTS SLACKEN TO DECREASE WINDS, PUTTING AN END TO ANY
LINGERING LAKE EFFECT SHOWERS FOR MOST BY AT LEAST THIS
AFTERNOON (HOLDS ON ACROSS THE LEELANAU PENINSULA, GRAND
TRAVERSE, AND BENZIE COUNTIES). THROUGH TODAY, CLOUDS WILL BEGIN
TO CLEAR WITH MOST HAVING PARTLY TO MOSTLY CLEAR SKIES BY
TONIGHT. EVEN THOUGH SOME MAY SEE THE SUN TODAY, DRAINAGE
NORTHERLY FLOW WILL KEEP TEMPERATURES COLD WITH HIGHS LARGELY IN
THE MID TEENS TO LOWER 20S. HEADING INTO TONIGHT, CLEARING
SKIES COMBINED WITH FRESH SNOW (FOR SOME) AND NORTH WINDS,
OVERNIGHT LOW TEMPERATURES LOOK TO DROP SUBSTANTIALLY AFTER
SUNSET, SETTING THE STAGE FOR A VERY CHILLY NIGHT WITH LOWS IN
THE SINGLE DIGITS TO NEGATIVE DOUBLE DIGITS ACROSS NORTHERN
MICHIGAN, ESPECIALLY LOOKING AT THE TYPICAL COLDER SPOTS FOR
NORTHERN LOWER (PELLSTON, GRAYLING, ATLANTA, ETC.). LOOKING AT
WIND CHILL VALUES, LOOKS LIKE SOME COULD POTENTIALLY REACH CLOSE
TO THE NEGATIVE TEENS AFTER MIDNIGHT IN THE EARLY HOURS OF
SUNDAY.
LONG TERM /SUNDAY THROUGH FRIDAY/
ISSUED AT 240 AM EST SAT DEC 21 2024
PATTERN SYNOPSIS / FORECAST:
RIDGING AMPLIFYING OVER THE CENTRAL PLAINS WILL BE IN THE
PROCESS OF FORCING A DEEP LONGWAVE TROUGH EASTWARD, USHERING IN
WARM AND MOIST ADVECTION VIA SOUTHERLY FLOW INTO THE REGION AS
AN ARCTIC BORNE SURFACE HIGH MOVES EASTWARD INTO NEW ENGLAND. A
STRONG PACIFIC JET (180-200KTS) WILL LEAD TO A SUBTLE SHORTWAVE
TROUGH MOVING EASTWARD ACROSS THE PLAINS AND INTO THE GREAT
LAKES LATE SUNDAY NIGHT INTO MONDAY. FAVORABLE JET DYNAMICS
SHOULD SUPPORT CYCLOGENESIS AND SURFACE PRESSURE FALLS OVER THE
GREAT LAKES THROUGH MONDAY... AND COUPLED WITH AN AMPLE
SOUTHERLY WAA TAP (POTENTIALLY ORIGINATING IN THE WESTERN GULF)
COLLIDING INTO THE HIND END OF THE DEPARTING ARCTIC AIRMASS
SHOULD LEAD TO PLENTIFUL LIFT TO SUPPORT A WIDESPREAD SNOWFALL
ACROSS MUCH OF THE AREA LATE SUNDAY NIGHT THROUGH EARLY MONDAY
NIGHT. EVENTUALLY, THE AFOREMENTIONED PACIFIC JET WILL REALLY
FLEX ITS MUSCLES AS IT BELCHES A MILDER AND DRIZZLY REGIME INTO
THE REGION JUST IN TIME FOR THE CHRISTMAS HOLIDAY, LIKELY
LASTING THROUGH THE REMAINDER OF THE FORECAST PERIOD.
PRIMARY FORECAST CONCERNS:
SUNDAY THROUGH MONDAY NIGHT: SOUTHERLY RETURN FLOW SHOULD BE IN
FULL SWING AS WE HEAD THROUGH THE DAY SUNDAY, QUICKLY
OVERWHELMING THE VERY COLD START EXPECTED (SEE SHORT TERM FOR
SATURDAY NIGHT COLD). GUIDANCE SEEMS RATHER BULLISH ON MOISTURE
RETURN INTERACTING WITH THOSE STILL QUITE WARM GREAT LAKES... SO
WHILE NOT QUITE LOOKING TO BE YOUR TYPICAL SYSTEM PREDECESSOR
SSW FLOW LAKE EFFECT EVENT IS ANTICIPATED, SOME PRECIP IS
ANTICIPATED OVER WESTERN MACKINAC COUNTY THROUGH THE DAY ON
SUNDAY. LATEST GUIDANCE HAS JUST ENOUGH SATURATION WITHIN THE
DGZ TO MAKE ME LEAN TO LIGHT SNOW AND ELIMINATE FREEZING
DRIZZLE, BUT IT'S CLOSE. CONSIDERING TEMPS WILL BE IN THE 20S,
THIS SHOULD BE MONITORED CLOSELY.
EVENTUALLY, THE LARGER SYSTEM MOVES INTO THE REGION, AND SHOULD
BRING A MUCH MORE IMPRESSIVE SATURATION LAYER (PWATS BALLOON AS
HIGH AS 0.50", AND SATURATION STRETCHES TO DADGUM NEAR
300MB...). WITH NORTHERN MICHIGAN PRECARIOUSLY PLACED IN THE
DIVERGENT QUADRANTS OF TWO JET STREAKS, EXPECTATION IS THAT THIS
SYSTEM PROBABLY REALLY BLOSSOMS RIGHT OVER THE TOP OF US. IN
ADDITION, WITH THAT IMPRESSIVE 850MB FLOW, STRONG THETA-E
ADVECTION CLASHING WITH THE DEPARTING ARCTIC AIRMASS COULD LEAD
TO A NARROW BAND OF HEAVIER SNOWFALL VIA FRONTOGENESIS. THIS
SIGNATURE SHOWS UP WELL ON CURRENT LONG TERM GUIDANCE... MOST
SPOTS HAVE ANYWHERE FROM 0.15-0.25" OF QPF FROM THIS SYSTEM,
WITH A NARROW SIGNATURE SHOWING 0.45"+ OF QPF. CONSIDERING THE
TIMING OF THIS SYSTEM (LIKELY OVERLAPS THE MONDAY MORNING
COMMUTE) AND THE CONSISTENCY OF THE SNOW (VERY WET / SLOPPY),
THIS COULD BE A MORE IMPACTFUL EVENT FOR THE REGION EVEN THOUGH
MOST PLACES GET PROBABLY A FEW INCHES OF SNOW (WHERE THAT BAND
SETS UP COULD CERTAINLY SEE A BIT MORE... POTENTIALLY IN THE
REALM OF 5-7"+ IF EVERYTHING COMES TOGETHER PERFECTLY). THIS
ACTIVITY WILL TAPER LATER IN THE DAY MONDAY... AND WITH
CONTINUED WARM AIR ADVECTION, NOT ANTICIPATING A LAKE EFFECT
RESPONSE ON THE BACKSIDE OF THE SYSTEM.
REST OF THE PERIOD: MINIMAL PRESSURE GRADIENT LIKELY LEADS TO A
STAGNANT AIRMASS ON THE HEELS OF THE SYSTEM... WILL HAVE TO
WATCH FOR ANY LINGERING MOISTURE TO PRESENT A DRIZZLE THREAT,
AND WE MAY HAVE TO WATCH THOSE TEMPERATURES MONDAY NIGHT INTO
TUESDAY. LATEST GUIDANCE HAS LOWS MONDAY NIGHT INTO THE 20S,
WHICH, IF THERE'S DRIZZLE, PRESENTS ICING CONCERNS. EVENTUALLY,
THE WARM AIR ADVECTION REGIME REALLY KICKS INTO GEAR... HIGHS
TUESDAY PEAK NEAR FREEZING TO THE MID 30S, AND INCREASING INTO
THE UPPER 30S TO MID 40S BY THURSDAY (THE DAY AFTER CHRISTMAS)
THROUGH THE REMAINDER OF THE FORECAST PERIOD. CONSIDERING THE
MOIST NATURE OF THE AIRMASS, NOT EXPECTING MUCH OF A FALL IN
TEMPERATURES OVERNIGHT ONCE THIS REGIME LOCKS INTO PLACE...
WHICH, WITH CONTINUOUS TEMPERATURES AND DEWPOINTS REMAINING OVER
FREEZING, WILL BE INCREDIBLY DETRIMENTAL TO THE EXISTING
SNOWPACK... AND IF THESE TRENDS HOLD, COULD MEAN THAT MUCH OF
THE AREA PROBABLY SEES BARE GROUND A FEW DAYS AFTER CHRISTMAS...
WHICH IS VERY UNFORTUNATE CONSIDERING THE ECONOMIC DRAW THAT
THE HOLIDAY WEEK BRINGS FOR WINTER ACTIVITIES ACROSS THE REGION.
AVIATION /06Z TAFS THROUGH 06Z SUNDAY/
ISSUED AT 1043 PM EST FRI DEC 20 2024
LAKE EFFECT SNOW SHOWERS HAVE CONTINUED TO PEPPER THE TAF SITES
AT TIMES OVER THE LAST SEVERAL HOURS. ACTIVITY SHOULD SETTLE
DOWN EARLY SATURDAY BUT POSSIBLY TARGET KTVC WITH POTENTIALLY
STEADIER SNOW SHOWERS AT TIMES. CIGS SHOULD REMAIN ON THE BORDER
OF MVFR AND LOW END VFR EARLY SATURDAY BUT BRIEFLY FALL TO IFR
IN SNOW SHOWERS. MAINLY VFR CIGS DEVELOP DURING THE DAY SATURDAY
AS HIGH PRESSURE BUILDS IN FROM THE NORTHWEST.
APX WATCHES/WARNINGS/ADVISORIES
MI...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 7 AM EST THIS MORNING FOR
LHZ347>349.
SMALL CRAFT ADVISORY UNTIL 7 AM EST THIS MORNING FOR LMZ323-
342-344>346.
SMALL CRAFT ADVISORY UNTIL 7 AM EST THIS MORNING FOR LSZ321.
SHORT TERM...NSC
LONG TERM...HAD
AVIATION...AJS
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