738
FXUS63 KAPX 181520
AFDAPX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GAYLORD MI
1020 AM EST SAT JAN 18 2025
KEY MESSAGES
- BITTERLY COLD TEMPERATURES/WIND CHILLS THROUGH TUESDAY.
- PERIODS OF LAKE EFFECT SNOW THROUGH TUESDAY NIGHT WITH SOME
BLOWING/DRIFTING AND SIGNIFICANTLY REDUCED VISIBILITY AT
TIMES.
UPDATE
ISSUED AT 1013 AM EST SAT JAN 18 2025
INVASION OF ARCTIC AIR HAS BEGUN BEHIND DEPARTING COLD FRONT
THIS MORNING. TEMPERATURES ALREADY DROPPING INTO THE TEENS
ACROSS PARTS OF THE AREA, AND EXPECT THIS TREND TO CONTINUE FOR
THE REMAINDER OF THE DAY. GUSTY NORTHWEST WINDS WILL OF COURSE
MAKE IT FEEL CONSIDERABLY COLDER, WITH WIDESPREAD WIND CHILL
VALES IN THE SINGLE DIGITS ABOVE AND BELOW ZERO BY LATER THIS
AFTERNOON. THAT COLD AIR WILL OF COURSE CONTINUE TO DRIVE LAKE
SNOWS INTO OUR TRADITIONAL SNOW BELT LOCATIONS. EXPECTING JUST
MINOR ADDITIONAL SNOW ACCUMULATIONS ACROSS NORTHWEST LOWER
MICHIGAN GIVEN LOSS OF ANY SYNOPTIC MOISTURE CONTRIBUTION. LONG
LAKE SUPERIOR FETCH WILL DEFINITELY HELP THE SNOW-PRODUCING
CAUSE OFF THAT BIG BODY OF WATER. HAVE ALREADY SEEN BRIEF
PERIODS OF SUB 1/2 MILE VISIBILITIES IN PASSING SNOW SHOWERS UP
IN THE SNOW BELTS OF CHIPPEWA COUNTY. SNOW SHOWERS, AT TIMES
HEAVY, WILL CONTINUE TO IMPACT NORTHWEST CHIPPEWA COUNTY THROUGH
TONIGHT...BRINGING SEVERAL INCHES OF ADDITIONAL SNOW
ACCUMULATIONS TO THAT AREA. HAVE ISSUED A WINTER WEATHER
ADVISORY TO ACCOUNT FOR SUCH.
SHORT TERM /THROUGH TONIGHT/
ISSUED AT 317 AM EST SAT JAN 18 2025
TURNING MUCH COLDER WITH LAKE EFFECT SNOW SHOWERS TODAY AND
TONIGHT...
DEEP LOW PRESSURE CURRENTLY CENTERED OVER EASTERN ONTARIO CONTINUES
TO SLOWLY PUSH EASTWARD EARLY THIS MORNING. ASSOCIATED STRONG COLD
FRONT EXTENDS FROM THE LOW THRU OUR NW CWA INTO NW ILLINOIS AND
CENTRAL MISSOURI. NARROW BAND OF LIGHT SYNOPTIC MIXED RAIN/SNOW IS
BISECTING NORTHERN LOWER MICHIGAN ATTM...MAKING VERY SLOW EASTWARD
PROGRESS OUT OF OUR CWA. STRONG CAA HAS BEGUN IMMEDIATELY BEHIND
THIS COLD FRONT...WITH TEMPS NOW BELOW FREEZING ACROSS EASTERN UPPER
MICHIGAN AND QUICKLY DROPPING ACROSS NW LOWER MICHIGAN.
COLD FRONT SHOULD CLEAR OUR CWA BY AROUND DAYBREAK THIS MORNING...
WITH CAA CONTINUING TO STRENGTHEN OVER THE NEXT 24 HOURS (AT LEAST).
850 MB TEMPS WILL DROP FROM THE NEGATIVE SINGLE DIGITS (C) EARLY
THIS MORNING TO THE NEGATIVE TEENS BY THIS AFTERNOON...FURTHER
PLUMMETING INTO THE NEGATIVE LOW 20S TONIGHT. OVER-LAKE INSTABILITY
WILL QUICKLY INCREASE...RESULTING IN THE DEVELOPMENT OF NW FLOW LAKE
EFFECT SNOW SHOWER BANDS. A LOOK AT UPSTREAM KMQT BASE REF TRENDS
ALREADY SHOWS RAPID DEVELOPMENT OF NW FLOW LAKE EFFECT SNOW SHOWERS
ACROSS UPPER MICHIGAN. WHILE A PROLONGED PERIOD OF NW FLOW LAKE
EFFECT SNOW SHOWER ACTIVITY IS DECIDEDLY SETTING UP FOR THE WEEKEND
INTO EARLY NEXT WEEK...ARRIVAL OF ARCTIC AIRMASS WITH EXTREMELY COLD
TEMPS WILL CERTAINLY LIMIT SNOWFLAKE SIZE AND THUS SNOWFALL
ACCUMULATION POTENTIAL. SMALL FLAKES WILL BE EFFICIENT AT REDUCING
VSBYS...BUT WILL LEND TO A GENERAL DIMINISH IN THE POTENTIAL FOR
SIGNIFICANT ACCUMULATIONS.
EXPECT A GENERAL 1 TO 2 INCHES OF NEW SNOW TODAY FOR OUR SNOWBELT
AREAS...WITH ANOTHER INCH OR TWO TONIGHT. THE EXCEPTION MAY BE
AROUND WHITEFISH POINT...WHERE SNOW ACCUMULATIONS MAY REACHING INTO
ADVISORY CRITERIA TONIGHT. WILL HOLD OFF ON ISSUANCE OF ANY
HEADLINES FOR THIS AREA FOR NOW TO SEE IF THIS EXPECTATION HOLDS.
TEMPS WILL FALL THRU THE 20S AND INTO THE TEENS THROUGHOUT TODAY...
CONTINUING TO PLUMMET TONIGHT INTO THE SINGLE DIGITS ABOVE ZERO FOR
OVERNIGHT LOWS TONIGHT.
LONG TERM /SUNDAY THROUGH FRIDAY/
ISSUED AT 317 AM EST SAT JAN 18 2025
PATTERN SYNOPSIS/FORECAST:
LONGWAVE TROUGH AXIS STRETCHES FROM OK/TX UP INTO JAMES/HUDSON BAY;
AHEAD OF THIS, MOIST AND MILD WITH SOUTHWESTERLY FLOW. BEHIND THIS,
MUCH COLDER AIR POURING INTO CENTRAL CANADA AS STRENGTHENING RIDGE
OVER ALASKA AND STEADFAST UPPER LOW NEAR GREENLAND ALLOW FOR
EXCELLENT FLOW OFF THE NORTH POLE. SURFACE TEMPS IN THE -20F AND
COLDER RANGE ALREADY FLOODING INTO CENTRAL CANADA IN THE WAKE OF THE
TROUGH AXIS AND ATTENDANT SURFACE FRONTS...PRIMARY 984MB SURFACE LOW
HEADED FOR JAMES BAY AS OF 2Z, AND ATTENDANT SURFACE FRONT STRETCHES
BACK TO REMNANTS OF SOCAL'S UPPER LOW NOW OVER THE MID MS VALLEY.
SECONDARY COLD FRONT FOLLOWS THE TROUGH AXIS THROUGH THE UPPER
MIDWEST INTO NEBRASKA. ANOMALOUS AND COLD 1044MB SURFACE HIGH LOOMS
OVER NW CANADA, SLOWLY OOZING SOUTHWARD TOWARD THE WESTERN US ALONG
STRENGTHENING THERMAL GRADIENT AND A COUPLE PV MAXIMA RIDING IT OUT
HERE.
COLD FRONT(S) TO CONTINUE TO EXIT STAGE RIGHT EARLY TODAY...WITH
INCREASINGLY COLD AIR EXPECTED TO FLOOD SOUTHWARD IN ITS WAKE. THIS
WILL OF COURSE RAMP UP OVERLAKE INSTABILITY AND LAKE EFFECT
SNOW...AS WELL AS RAMP UP THE LAKE AGGREGATE TROUGH...AS COLDEST OF
THE AIR FLOWS AROUND OUR STILL-ANOMALOUSLY WARM GREAT LAKES. ANOTHER
MORE POTENT TROUGH AXIS SWINGS THROUGH SUNDAY/SUNDAY NIGHT...WITH
FLOW TURNING A BIT MORE ZONAL AS WE GO INTO MONDAY (ALSO SHIFTING
THE FOCUS OF LAKE EFFECT SNOW). UPSTREAM TROUGH AXIS SHARPENS UP
MONDAY NIGHT...CROSSING THE GREAT LAKES TUESDAY. LAKE AGGREGATE
TROUGH BECOMES MORE ZONALLY ORIENTED AS SURFACE HIGH PASSES THROUGH
THE OH VALLEY TO OUR SOUTH, POTENTIALLY PUTTING SOME PARTS OF
CENTRAL LOWER MI UNDER A GREATER THREAT FOR COLD AIR/CLEARING
COMPARED TO POINTS FURTHER NORTH. HEIGHT RISES FINALLY RETURN FOR
MIDWEEK...JUST AS ADDITIONAL SHORTWAVE TROUGHING SNEAKS INTO THE
CENTRAL US (EXACT POSITION TBD)...WITH POTENTIAL FOR SOME SYNOPTIC-
TYPE ACTIVITY TO IMPACT THE UPPER GREAT LAKES GOING INTO THE SECOND
HALF OF THE WEEK. BEYOND THIS...MODEL SOLUTIONS DIVERGE WITH REGARD
TO EVOLUTION OF THE UPSTREAM PATTERN, RESULTING IN SIGNIFICANT
UNCERTAINTY IN THE PATTERN FOR LATE NEXT WEEK INTO NEXT WEEKEND.
PRIMARY FORECAST CONCERNS:
ACCUMULATING POWDERY LAKE EFFECT SNOW THROUGH TUESDAY...AS HAS BEEN
ADVERTISED FOR THE LAST FEW DAYS/NIGHTS...INCOMING COLD AIR MASS
WILL RESULT IN LAKE EFFECT SNOW. SNOW TO CONTINUE SUNDAY, AND LIKELY
BECOME A BIT ENHANCED BY A TROUGH AXIS SWINGING THROUGH IN THE
MORNING. THIS SHOULD KEEP GENERALLY NNW-NW FLOW ONGOING...WITH THE
EXPECTATION WINDS SHOULD BACK A LITTLE MORE WNW GOING INTO SUNDAY
NIGHT AND MONDAY WITH ADDITIONAL PV NIBLETS DIGGING DOWN INTO THE
UPPER MIDWEST, DRAGGING THE CORE OF THE COLDEST AIR THROUGH THE
REGION IN. THINK THE FLOW COULD BECOME EVEN A LITTLE MORE W TO EVEN
WSW MONDAY NIGHT INTO TUESDAY AS ANOTHER NIBLET DIGS THROUGH
TUESDAY...WITH LAKE AGGREGATE TROUGH REMAINING STRONG AS COLD AIR
PASSES BY. FOCUS SHOULD BE THE USUAL NNW TO W FLOW SNOWBELTS OF
NORTHWEST LOWER, AND STRONG LAKE AGGREGATE TROUGH SUPPORTS A DECENT
THREAT FOR THE PRESQUE ISLE COAST OF NE LOWER (THOUGH THIS COULD
WAVER BACK AND FORTH OFF/ONSHORE)...AS WELL AS THE EUP. TRICK PART
WITH THE YOOP (PERHAPS EVEN FOR NW LOWER?) WILL BE THE POSITION OF
THE LAKE AGGREGATE TROUGH...AS WELL AS STRONG INFLUENCE OF DRAINAGE
FLOW OUT OF ONTARIO TO FURTHER ENHANCE THE SURFACE
TROUGH/CONVERGENCE/FGEN. THINK THIS CERTAINLY HAS POTENTIAL TO SHIFT
THE BETTER CONVERGENCE WESTWARD TOWARD WESTERN CHIP AND PERHAPS EVEN
TC...AND COULD CERTAINLY DRIFT BACK AND FORTH OVER THE YOOP
DEPENDING ON HOW FAR THE DRAINAGE FLOW IS ALLOWED TO GO, THOUGH FOR
NOW...SUSPECT THE PRIMARY FOCUS COULD/SHOULD BE WESTERN CHIPPEWA
COUNTY OR PERHAPS JUST WEST, PARTICULARLY WITH SOME CONCERNS FOR A
PIVOT POINT IN THIS REGION AS THE LAKE AGGREGATE TROUGH BACKS FROM A
NW-SE ORIENTATION TO W-E WITH TIME. ALSO THINK THERE IS POTENTIAL
FOR PESKY MESOLOWS OVER LAKE SUPERIOR IN PARTICULAR, WHERE THE FLOW
MAY BE LIGHT ENOUGH TO SUPPORT SUCH NEBULOUS-TO-PREDICT BUT
IMPACTFUL FEATURES.
REGARDING AMOUNTS, COLD AIR MASS SUPPORTS SMALLER FLAKES AND MORE
POWDERY SNOW, WHICH WILL NOT ACCUMULATE AS EFFICIENTLY AS RECENT
LAKE SNOWS, BUT WILL CERTAINLY BE EASIER TO BLOW/DRIFT AND REDUCE
VISIBILITY. STILL...STRONG SIGNALS FOR DEVELOPMENT OF CONVERGENCE
BANDS AND REASONABLY DEEP LAKE CONVECTION (INVERSION HEIGHTS STILL
EXPECTED AROUND 8-12KFT) SUPPORT POTENTIAL FOR SEVERAL INCHES TO
ACCUMULATE THROUGH ANY GIVEN 12-24HR PERIOD UNDER THE HEAVIEST BANDS
AS THEY PERSIST. FORTUNATELY, NOTING THE FLOW MAY NOT STAY LOCKED IN
THROUGH THE SUNDAY-TUESDAY TIME PERIOD...EXPECTING THE LAKE EFFECT
FIREHOSE TO SHIFT AROUND A BIT AND SPREAD THE WEALTH. IF ANY
MESOLOWS DO END UP FORMING, WHICH IS ENTIRELY POSSIBLE...SOME AREAS
COULD END UP WITH MUCH MORE SNOW THAN CURRENTLY FORECAST.
DANGEROUSLY COLD TEMPERATURES/WIND CHILLS SUNDAY THROUGH
TUESDAY...AGAIN, AS HAS BEEN ADVERTISED...VERY COLD AIR MASS COMING
INTO THE REGION TO START THE UPCOMING WEEK. ANNUAL RETURN INTERVALS
FOR THE LOWER-LEVEL (I.E., 850MB) AIR MASS ARE GENERALLY 3-5 YEARS
FOR OUR AREA...BUT 5-10 YEARS OR MORE FURTHER WEST (WHERE THE LAKES
WILL HAVE MUCH LESS OF A MODERATING IMPACT). 1000-500MB THICKNESS
VALUES DROPPING BELOW 500DAM TEND TO BE ASSOCIATED WITH HIGHS IN THE
SINGLE DIGITS; EVEN SOME OF THE ENSEMBLE THICKNESS PROGS SUGGEST WE
COULD BE WELL BELOW THIS (CLOSER TO 490DAM OR EVEN LESS)...WHICH
COULD SUPPORT DAYTIME HIGHS STRUGGLING TO BREAK THE ZERO-DEGREE
MARK. FOR HISTORICAL REFERENCE/CONTEXT...OUT OF THE RELATIVELY FEW
TIMES THE GLR ASOS HAS RECORDED SUB-ZERO DAYTIME HIGHS (SINCE ITS
INSTALLATION IN 1998...SO P.O.R. ISN'T VERY LONG, FWIW)... FEB 19,
2015 WAS THE COLDEST, WITH A HIGH OF -5F. REANALYSIS SHOWS THE CORE
OF THE COLDEST AIR WITH THIS EVENT WAS FOCUSED MUCH MORE TO OUR
NORTH THAN IS EXPECTED FOR THIS EVENT...BUT ITS THICKNESS VALUES OF
486DAM ARE WITHIN THE REALM OF POSSIBILITIES FOR OUR UPCOMING EVENT.
THINK THE COLDEST TIMEFRAME WILL BE MONDAY INTO TUESDAY NIGHT...WITH
COLDEST TEMPS MOST LIKELY TO IMPACT THE SOO AND NEARBY AREAS WITH
DRAINAGE FLOW (BARRING CLOUD COVER/LAKE BANDS)...AND TOWARD THE M-55
CORRIDOR WHERE THE COLDER AIR SWINGING THROUGH WILL HAVE LESS WATER
TO CROSS (AND WHERE THERE IS A GREATER POTENTIAL FOR HIGH PRESSURE
TO LEAD TO RADIATIONAL COOLING CONCERNS). OVERNIGHT LOWS EXPECTED TO
DROP INTO THE SINGLE DIGITS BELOW ZERO...AND IF WE DO END UP
STRUGGLING TO GET ABOVE ZERO FOR HIGHS...COULD BE LOOKING AT
OVERNIGHT LOWS WELL INTO THE MINUS-TEENS OR COLDER, PARTICULARLY IF
RADIATIONAL COOLING IS ABLE TO PLAY A ROLE AT ALL.
WIND CHILL CONCERNS WILL BE GREATEST ACROSS THE EASTERN UP WHERE
ACTUAL AIR TEMPS WELL BELOW ZERO, EVEN WITH VERY LITTLE WIND (AND
WINDS SHOULD BE LIGHTER UP HERE), WILL SUPPORT A THREAT FOR WIND
CHILLS BELOW -25F. THINK THERE WILL BE CONCERNS FOR NORTHERN LOWER,
TOO, AS WINDS ARE MORE LIKELY TO BE STRONGER (EVEN IF ONLY BY A FEW
KNOTS) BETWEEN THE LAKE AGGREGATE TROUGH AND SURFACE HIGH SLIDING
THROUGH THE OH VALLEY...AND WIND CHILLS/APPARENT TEMPS THEMSELVES
WOULD BE THE PRIMARY THREAT...PARTICULARLY IF ANY AREAS DO END UP
GETTING COLDER THAN CURRENTLY EXPECTED. PROB GUIDANCE ACTUALLY SEEMS
TO LIKE THE IDEA OF -20F OR COLDER TEMPS ACROSS A DECENT SWATH OF
NORTHERN LOWER FOR MONDAY NIGHT AND AGAIN TUESDAY NIGHT...SO WILL
HAVE TO KEEP AN EYE ON THIS, TOO.
AVIATION /12Z TAFS THROUGH 12Z SUNDAY/
ISSUED AT 600 AM EST SAT JAN 18 2025
STRONG CAA IN THE WAKE OF A DEPARTING ARCTIC FRONT WILL GENERATE
NW FLOW LAKE EFFECT SNOW SHOWERS TODAY AND TONIGHT...TARGETING
OUT TYPICAL SNOWBELT AREAS FOR THE HEAVIEST AND MOST PERSISTENT
SNOWFALL. PREVAILING LOW VFR/MVFR CONDITIONS WILL DROP TO IFR
WITHIN HEAVIER SNOW SHOWER ACTIVITY OVER THE NEXT 24 HOURS.
SURFACE WINDS WILL REMAIN FORM THE NW AT 15 TO 25 KTS WITH
HIGHER GUSTS EXPECTED.
APX WATCHES/WARNINGS/ADVISORIES
MI...WINTER WEATHER ADVISORY UNTIL MIDNIGHT EST TONIGHT FOR MIZ086.
MARINE...SMALL CRAFT ADVISORY UNTIL MIDNIGHT EST TONIGHT FOR LHZ345>349.
SMALL CRAFT ADVISORY UNTIL 5 AM EST SUNDAY FOR LMZ323-341-342-
344>346.
SMALL CRAFT ADVISORY UNTIL MIDNIGHT EST TONIGHT FOR LSZ322.
SMALL CRAFT ADVISORY UNTIL 5 AM EST SUNDAY FOR LSZ321.
UPDATE...MSB
SHORT TERM...MLR
LONG TERM...FEF
AVIATION...MLR
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