FXUS63 KAPX 150845
AFDAPX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GAYLORD MI
345 AM EST TUE DEC 15 2009
.SYNOPSIS.../ISSUED AT 345 AM/
COLDER AIR WILL POUR INTO THE NORTH WOODS TODAY AND TONIGHT AND
LEAD TO ACCUMULATING LAKE EFFECT SNOWS IN THE SNOWBELTS. THE LAKE
EFFECT SNOWS WILL WEAKEN INTO WEDNESDAY AS HIGH PRESSURE SETTLES
IN ACROSS THE WESTERN GREAT LAKES. LIGHT LAKE EFFECT SNOW AND
FLURRIES WILL LINGER ACROSS THE REGION THROUGH THE END OF THE WORK
WEEK.
SMD
&&
.SHORT TERM.../ISSUED AT 345 AM/...TODAY
MAIN FCST CONCERN THRU THE DAY REVOLVES AROUND LAKE EFFECT/ENHANCED
SNOWFALL AMOUNTS AND ANY POTENTIAL HEADLINES NEEDED. BACK EDGE OF
LINGERING SYNOPTIC SNOW SHIELD GRADUALLY EDGING EAST EARLY THIS
MORNING...THOUGH PICKING UP A BIT OF ENHANCEMENT AT TIMES VIA
TERRAIN ENHANCEMENT/LAKE HELP AS WELL AS TRANSIENT FGEN AXIS BEING
PICKED UP BY THE RUC QUITE WELL (NAM/GFS NOT SO MUCH). APPEARS
OVERALL MOISTURE AND PRECIP COVERAGE WILL TAKE A HIT FOR A FEW HOURS
CENTERED ON 10-12Z IN THE WAKE OF DEPARTING SHORTWAVE...WITH LAKE
EFFECT SNOW SHOWERS QUICKLY TAKING SHAPE AS COLD ADVECTION ENSUES
(H85 TEMPS HEADED DOWN TOWARD -16C BY 18Z). SETUP THEN APPEARS
RATHER FAVORABLE FOR A BRIEF PERIOD OF SOME BEEFY LAKE ENHANCEMENT
INTO THE AFTN HOURS (SAY 15-21Z OR SO) WITH APPROACH OF SECONDARY
SHORTWAVE TROUGH CURRENTLY CROSSING EASTERN MINNESOTA AT 07Z (SEE
NICE ENHANCEMENT VIA IR SATELLITE PICS). QUICK SHOT OF DEEP LAYER
-DIVQ COUPLED WITH UPTICK IN 850-700MB RH TOWARD 90% AND INVERSION
HEIGHTS CLIMBING UPWARD TOWARD 6-7KFT (8KFT OR SLIGHTLY HIGHER INTO
EASTERN UPR) ARGUE FOR SOME NICE LAKE ENHANCEMENT AS MEAN 1000-850MB
FLOW SETS UP ROUGHLY 280-290 DEGREES.
THINGS QUICKLY TAKE A DIVE THEREAFTER WITH RAPID LOSS OF SYNOPTIC
MOISTURE (850-700MB RH FALLING TOWARD 35% BY 00Z) AND DEEP LAYER
SUBSIDENCE HELPING SQUASH INVERSION HEIGHTS DOWN TOWARD 3-4KFT BY
EARLY EVENING. PER FCST RAOBS...COULD BE LOOKING AT SOME HEALTHY
RATIOS AT TIMES DURING LAKE ENHANCEMENT WITH LAKE-INDUCED VERTICAL
MOTION FIELDS PEGGED RIGHT AROUND THE -14C TO -18C RANGE (HELPED OUT
BY COOLING COLUMN OF COURSE). WILL CARRY A GENERAL 2 TO 5 INCHES IN
THE FAVORED WEST/NORTHWEST FLOW REGIMES...HIGHEST NEAR PARADISE/
WHITEFISH POINT WHERE APPEARS LOCALIZED CONVERGENCE MAY BE MAXIMIZED
THRU EARLY AFTN. GIVEN OVERALL SHORT TIME PERIOD OF FAVORABLE LAKE
ENHANCEMENT...WILL OPT TO HOLD OFF ON ANY ADVISORIES AT THIS
POINT...THOUGH SUPPOSE NOT TOTALLY IMPOSSIBLE FOR A FEW SPOTS TO
NEED ONE PENDING WHERE BEST ENHANCEMENT SETS UP THIS AFTN. HIGH
TEMPS WILL MAX OUT EARLY TODAY...SLOWLY FALLING INTO THE AFTN WITH
ONGOING COLD ADVECTION.
LAWRENCE
&&
.LONG TERM.../ISSUED AT 345 AM/...TONIGHT AND BEYOND
PURE LES SCENARIO SETTING UP TONIGHT THRU THE DAY ON WEDNESDAY WITH
INVERSION HEIGHTS FURTHER LOWERING TOWARD 3KFT WHILE OVERLAKE
INSTABILITY MAXES OUT WITH H85 TEMPS DIPPING TO -18C FOR A BRIEF
TIME. DESPITE ANEMIC MOISTURE FIELDS...PROPENSITY FOR LAKE
CONVECTION TO PERSIST ARGUES FOR CATEGORICAL SNOW MENTION IN THE
WEST/NORTHWEST FLOW BELTS TONIGHT. ONE INTERESTING AREA TO WATCH
WILL BE NORTHERN CHIPPEWA COUNTY AS NAM HAS BEEN RATHER CONSISTENT
THE PAST 24 HOURS REGARDING POTENTIAL FOR LOCALIZED CONVERGENCE
MAXIMUM TO DEVELOP UP THAT WAY AS DRAINAGE FLOW TAKES SHAPE OVR
ONTARIO. WILL CARRY A SMALL STRIP OF 2 TO 4 INCHES UP THERE...WITH
PERHAPS AN INCH OR TWO ANTRIM/OTSEGO/KALKASKA/CHARLEVOIX AS DESPITE
PATHETIC MOISTURE...REBOUNDING THERMAL PROFILES PLACE LOW LEVEL
OMEGA RIGHT BACK THRU THE DGZ (MAXIMIZED POTENTIAL FOR VERY FLUFFY
SNOW).
THEREAFTER...RATHER GOOFY UPR PATTERN EXPECTED TO UNFOLD LATE INTO
THE WEEK/WEEKEND WITH SLOW RETROGRESSION OF CLOSED MID LEVEL CYCLONE
INTO EASTERN CANADA (STRONG REX BLOCK SIGNATURE). GUIDANCE
STRUGGLING QUITE A BIT WITH RUN TO RUN CONSISTENCY REGARDING THIS
FEATURE (NO SURPRISE THERE)...THOUGH DOES INCREASINGLY APPEAR HIGH
PRESSURE WILL DOMINATE THE SCENE AROUND THESE PARTS LATER WED NIGHT
THRU FRI AS FAIRLY HEALTHY MID LEVEL CONFLUENCE AXIS HELPS DRIVE
ELONGATED LOW LEVEL RIDGING FROM NEAR NORTHERN SASKATCHEWAN DOWN
THRU THE GREAT LAKES/OHIO VALLEY. DIFFICULT TO SEE MUCH IN THE WAY
OF LAKE SNOW CHANCES DURING THIS PERIOD WITH LIGHT/VARIABLE WIND
FIELDS AND NON-EXISTENT MOISTURE... THOUGH WILL INEVITABLY BE
DEALING WITH SOMETHING PESKY...MOST NOTABLY WED NIGHT WITH POTENTIAL
FOR LAKE HURON BAND TO BE SHOVED BACK TOWARD NORTHEAST LOWER
COASTLINE WITH DEVELOPING STRONGER DRAINAGE FLOW FROM ONTARIO. HIGH
PRESSURE SETUP ALSO SUGGESTS SOME RATHER COLD MORNINGS MAY BE IN THE
OFFING...ESPECIALLY INLAND AREAS WHERE WOULD NOT BE SURPRISED TO SEE
SOME SPOTS FLIRTING WITH -5 TO -10F AT SOME POINT. OTHERWISE...HIGH
TEMPS TO HOLD BELOW CLIMO.
LAWRENCE
&&
.MARINE.../ISSUED AT 345 AM/
COLDER AIR SURGING INTO THE REGION WILL SUPPORT A RETURN TO SMALL
CRAFT ADVISORY CONDITIONS FOR ALL NEARSHORE WATERS TODAY THROUGH
TONIGHT...WITH PERIODIC GUSTS TO 30 KNOTS POSSIBLE. CONDITIONS WILL
GRADUALLY CALM DOWN INTO WEDNESDAY...WITH MUCH MORE TRANQUIL WEATHER
EXPECTED WEDNESDAY NIGHT THROUGH THE DAY ON FRIDAY...AS HIGH
PRESSURE BUILDS OVER THE NORTHERN GREAT LAKES.
LAWRENCE
&&
.AVIATION.../ISSUED AT 1150 PM/...VALID FOR 06Z TAFS
MVFR TO AT TIMES IFR CONDITIONS WILL CONTINUE OVER THE NEXT 24 HOURS
AS AREAS OF LIGHT SNOW GRADUALLY TRANSITION TO LAKE EFFECT SNOW
SHOWERS OVERNIGHT. LAKE EFFECT SNOW SHOWERS WILL PERSIST THRU
TUESDAY...TARGETING NW FLOW AREAS FOR THE BEST CHANCE OF
ACCUMULATING SNOW. SNOW SHOWERS WILL DIMINISH TUESDAY EVENING AS MID
LEVEL DRY AIR FILTERS INTO THE REGION AND INVERSION HEIGHTS STEADILY
LOWER.
&&
.APX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LM...SMALL CRAFT ADVISORY UNTIL 7 AM EST WEDNESDAY FOR LMZ323-341-342-
344>346.
LH...SMALL CRAFT ADVISORY UNTIL 7 AM EST WEDNESDAY FOR LHZ345>349.
LS...SMALL CRAFT ADVISORY UNTIL 7 AM EST WEDNESDAY FOR LSZ321-322.
&&
$$
