FXUS63 KAPX 252330
AFDAPX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GAYLORD MI
630 PM EST WED NOV 25 2009
.SYNOPSIS.../ISSUED AT 403 PM/
LOW PRESSURE MOVING ACROSS NORTHERN LOWER MICHIGAN LATE THIS
AFTERNOON...WILL STALL OVER LAKE HURON THANKSGIVING DAY. AN
ASSOCIATED UPPER LEVEL DISTURBANCE SWINGING ACROSS THE REGION WILL
SPREAD RAIN ACROSS NORTHERN MICHIGAN LATER TONIGHT INTO
THANKSGIVING...WITH PRECIPITATION CHANGING OVER TO SNOW ACROSS
MANY AREAS THURSDAY NIGHT WITH SOME LIGHT ACCUMULATIONS ACROSS
PARTS OF EASTERN UPPER AND INTERIOR NORTHERN LOWER MICHIGAN. SOME
LAKE EFFECT SNOW SHOWERS WILL OCCUR FRIDAY...WITH DRIER WEATHER
MOVING BACK IN FOR SATURDAY. COLDER WEATHER IS ON THE WAY FOR NEXT
WEEK.
JPB
&&
.SHORT TERM.../ISSUED AT 403 PM/...TONIGHT
MAIN CONCERN IS FOR THE RAIN CHANCES TONIGHT. MAIN IDEA THAT WE
HAVE BEEN CARRYING IS STILL GOOD AS SECOND 500 MB WAVE OVER IOWA
WILL ROTATE THROUGH THE 500 MB LONG WAVE AND INTO LOWER MICHIGAN
OVERNIGHT. THIS WILL KEEP US IN SCATTERED TO LIKELY RAIN SHOWER
THIS EVENING AND LIKELY TO CATEGORICAL RAIN SHOWERS OVERNIGHT. NOT
TO MENTION LOW CLOUDS AND FOG. THIS IS BEING REINFORCED BY THE
UPWARD MOTION FROM THE LEFT FRONT QUADRANT OF THE 500 MB JET AND
THE 850 MB BAROCLINIC/DEFORMATION ZONE BEGINNING TO ENCROACH ON
THE UPPER LAKES. SNOW WILL HOLD OFF UNTIL THURSDAY NIGHT TIME
FRAME, ONCE THE SFC LOW MOVES TO THE EAST IN ONTARIO.
JSL
&&
.LONG TERM.../ISSUED AT 403 PM/...THURSDAY AND BEYOND
UPPER LOW SPINNING ITS WAY ACROSS IOWA THIS AFTERNOON WILL SWING
THROUGH LOWER MICHIGAN AND THE OHIO VALLEY ON THANKSGIVING
DAY...TAKING ON A NEGATIVE TILT AS IT APPROACHES THE EAST COAST
FRIDAY. HEIGHT RISES/FLAT SHORT RIDGING BUILDS BACK ACROSS THE
MIDWEST AND WESTERN GREAT LAKES TO START THE WEEKEND...WITH SPLIT
FLOW TROUGHING MOVING INTO THE WESTERN U.S.. FORECAST EVOLUTION OF
THIS TROUGH HAS BEEN A PROBLEM THE LAST FEW DAYS...AND WILL PROBABLY
CONTINUE TO BE AS GUIDANCE ATTEMPTS TO DEAL WITH ENERGY IN SEPARATE
STREAMS...AND WHICH WILL PREDOMINATE. LONG RANGE MEAN CHARTS
CONTINUE TO SUGGEST MORE MEAN TROUGHING SETTING UP ACROSS CENTRAL
NORTH AMERICA WITH RIDGING UP OFF/ALONG THE WEST COAST FOR THE FIRST
DAYS OF DECEMBER...SO PERHAPS ALL OF THIS IS A PRECURSOR TO A SHIFT
TOWARD COLDER TEMPERATURES TO START METEOROLOGICAL WINTER. INITIAL
FORECAST CONCERNS WILL DEAL WITH PRECIP ISSUES ASSOCIATED WITH
SYSTEM CROSSING THE REGION ON THANKSGIVING...INCLUDING PRECIP TYPE
HEADING INTO THE LATTER PART OF THURSDAY.
THURSDAY...FORECAST THINKING HASN'T CHANGED MUCH SINCE YESTERDAY...
THOUGH FORECAST IS A BIT COMPLICATED GIVEN SYNOPTIC/LAKE EFFECT
PRECIP EVOLUTION AND PRECIP TYPE ISSUES. CENTER OF UPPER LEVEL
CIRCULATION EXPECTED TO BE OVER INDIANA THANKSGIVING MORNING...
CROSSING THE OHIO VALLEY DURING THE DAY. EXPECT PRECIPITATION
SHOULD BE WIDESPREAD ACROSS NORTHERN MICHIGAN BY MORNING WITH THE
FORECAST AREA IN THE PRIME DEFORMATION ZONE. DRY SLOT WILL BE
LIFTING UP THE EAST SIDE OF THE UPPER TROUGH DURING THE MORNING...
SOME QUESTION AS TO HOW CLOSE IT WILL GET TO NORTHERN LOWER MICHIGAN
(WHICH WOULD LIKELY CUT OFF PRECIPITATION FOR A WHILE ACROSS
NORTHEAST LOWER). JUDGING VARIOUS GUIDANCE VERSUS WATER VAPOR
IMAGERY/GOES TOTAL PRECIPITABLE WATER PLOTS SUGGESTS MOST OF THE DRY
AIR WILL REMAIN EAST OF THE STATE (MAY ALTER POPS A BIT ALONG LAKE
HURON SHORELINE TO ALLOW FOR POSSIBILITY OF "DRY SLOT INTERFERENCE").
OVERALL FRONTOGENETIC FORCING NOT OVERWHELMING GIVEN RATHER
DISORGANIZED THERMAL GRADIENT ACROSS LOWER MICHIGAN (BASICALLY
WITHIN THE LOW LEVEL THERMAL "RIDGE")...AND QG FORCING MAY END UP
GETTING "SQUEEZED" (FOR LACK OF A BETTER SCIENTIFIC SOUNDING TERM)
DOWN INTO THE LOWER LAYERS AS THE DAY WEARS ON. SO QPF POTENTIAL
APPEARS TO BE GREATEST DURING THE FIRST HALF OF THE DAY OR SO.
DRIER AIR NUDGES INTO WESTERN PORTIONS OF THE FORECAST AREA THURSDAY
EVENING...WHICH SHOULD GRADUALLY CONFINE SYNOPTIC PRECIP COVERAGE
CLOSER TO LAKE HURON THROUGH THE NIGHT. MEANWHILE...COLDER AIR TO
THE WEST DURING THE DAY WILL BEGIN TO SPILL INTO NORTHERN MICHIGAN
THURSDAY NIGHT. 850MB TEMPERATURES FORECAST TO DROP INTO THE -6 TO
-8C RANGE (ABOUT THE SAME AS INVERSION HEIGHT)...WITH LAKE INDUCED
CAPE VALUES ONLY AROUND 200 J/KG OR SO. BUT ENOUGH INSTABILITY AND
WRAP AROUND LOW LEVEL MOISTURE/CYCLONIC FLOW TO ALLOW FOR SOME LAKE
EFFECT STREAMERS TO DEVELOP IN NORTH-NORTHWEST FLOW MAINLY OFF LAKE
MICHIGAN INTO NORTHWEST LOWER (LOW LEVEL TRAJECTORY MAY NOT BE
FAVORABLE FOR EASTERN UPPER).
AS FOR PRECIP TYPE...STILL LOOKS LIKE PRECIP WILL START THURSDAY AS
ALL RAIN ACROSS THE AREA...AS COLD AIR GRADUALLY ADVANCES IN FROM
THE NORTHWEST AND SOUTHWEST. FIRST AREAS TO BEGIN TO CHANGE OVER
LOOK TO BE WESTERN CHIPPEWA/MACKINAC COUNTIES AND HIGHER TERRAIN OF
NORTHERN LOWER POSSIBLY BY LATE AFTERNOON. WARM LAYER WILL BE
SURFACE BASED...SO WILL TAKE SOME TIME TO ERODE THROUGH ADVECTION
AND MELTING INDUCED COOLING. LOW LEVEL THERMAL PROFILES MAY BE A
BIT WARM AS MODELS HAVE A TENDENCY TO HANG ONTO SURFACE BASED WARM
LAYERS THAT EXHIBIT STEEPER LAPSE RATES IN THE GUIDANCE (USUALLY
ENDS UP BEING COOLER AT THE SURFACE THAN FORECAST). EXPECT
TRANSITION ACROSS INTERIOR NORTHERN LOWER AND EASTERN UPPER TO BE
RELATIVELY QUICK...BUT AREAS AROUND THE LAKE SHORES WILL LIKELY
REMAIN LIQUID INTO THE EVENING...WITH SOME TRANSITION OVERNIGHT
(ESPECIALLY WITH MARINE INFLUENCE).
THINK SOME LIGHT ACCUMULATIONS STILL POSSIBLE ACROSS INTERIOR
NORTHERN LOWER...A COMBINATION OF LINGERING SYNOPTIC PRECIP AND
PERHAPS SOME CONTRIBUTION FROM LAKE EFFECT THOUGH THAT IS DIFFICULT
TO QUANTIFY. ANOTHER AREA OF CONCERN IS THE EASTERN END OF THE
UPPER PENINSULA...WHICH MAY CHANGE OVER TO SNOW WHILE SOME "DECENT"
SYNOPTIC PRECIP STILL ONGOING. SO WILL ALSO ADD SOME LIGHT
ACCUMULATIONS THERE AS WELL (GENERALLY 1-2/1-3 INCHES). AS
MENTIONED IN THIS SPACE YESTERDAY...WILL NEED TO KEEP AN EYE ON THIS
AS SLOW MOVING DEFORMATION ZONES CAN BE SNEAKY (THOUGH LACKING
BAROCLINICITY IN THIS CASE MAY HELP US OUT). FROM A TOTALLY
NON-SCIENTIFIC STANDPOINT HOWEVER...HOLIDAY EVENING SHIFTS ARE
CLIMATOLOGICALLY RIPE FOR METEOROLOGICAL MISCHIEF (BEEN THERE...
DONE THAT). SO ALL THE MORE REASON TO PROCEED WITH CAUTION...
FRIDAY...SYNOPTIC EVENT WILL HAVE WOUND DOWN BY FRIDAY MORNING...
WITH CONTINUED POTENTIAL FOR LAKE EFFECT SNOW SHOWERS IN NORTHWEST
FLOW ALOFT. ANTICIPATE LAKE CONVECTION TO WIND DOWN FRIDAY NIGHT AS
DRIER AIR AND LOW LEVEL RIDGING PUSH INTO THE UPPER LAKES.
EXTENDED FORECAST (SATURDAY THROUGH WEDNESDAY)...WEEKEND STARTS OUT
WITHIN FLAT SHORT WAVE RIDGING ACROSS THE UPPER MIDWEST/UPPER GREAT
LAKES BETWEEN EAST COAST STORM SYSTEM AND SPLIT TROUGHING CROSSING
THE WESTERN MOUNTAINS. WARM ADVECTION PATTERN DEVELOPS ACROSS THE
STATE AHEAD OF AN UPSTREAM BAROCLINIC ZONE ASSOCIATED WITH WESTERN
HEIGHT FALLS. SATURDAY ITSELF STILL LOOKS DRY...PIECE OF NORTHERN
STREAM ENERGY AND ASSOCIATED SURFACE WAVE/FRONTAL BOUNDARIES MAY
IMPACT THE UPPER GREAT LAKES GOING INTO SUNDAY CURRENT LOW CHANCE
POPS FOR SUNDAY (RAIN SOUTH/RAIN OR SNOW NORTH) WILL SUFFICE FOR
NOW...POTENTIAL NOT OVERLY IMPRESSIVE ON PAPER. COLD ADVECTION
BEHIND THIS SURFACE WAVE FORECAST TO BRING SUB -5C 850MB
TEMPERATURES BACK INTO THE FORECAST AREA BY MONDAY MORNING...
INCREASING THE POTENTIAL FOR LAKE INDUCED SNOW SHOWERS FROM SUNDAY
NIGHT THROUGH MONDAY NIGHT. THINGS GET INFINITELY MORE INTERESTING
GOING FORWARD INTO TUESDAY AND BEYOND AS EVOLUTION OF SPLIT TROUGH
AND POTENTIAL STORM DEVELOPMENT COME INTO FOCUS (WITH ANOTHER WAVE
DROPPING INTO THE NORTHERN ROCKIES HELPING TO COMPLICATE MATTERS).
CURRENTLY LEANING AWAY FORM THE 25/00Z GFS OPERATIONAL IDEA OF MORE
OF A PHASED IDEA WITH NORTHERN BRANCH ENERGY DIVING INTO SOUTHERN
BRANCH TROUGH AND SPINNING UP A STORM OVER THE TENNESSEE VALLEY
TUESDAY (THOUGH WOULD STILL BE A MOSTLY RAIN EVENT FOR NORTHERN
MICHIGAN...AT LEAST ON THE FRONT END). REGARDLESS...PREFER ECMWF
IDEA OF MORE SEPARATION BETWEEN STREAMS AND MORE DOMINANCE OF THE
SOUTHERN BRANCH (NEW LOOK AT THE 25/12Z GUIDANCE SUPPORTS THIS AS
WELL AS GFS HAS ABANDONED ITS IDEA FROM 00Z). AT THE VERY LEAST
THERE IS MORE CONFIDENCE IN TRENDING THE FORECAST COLDER FOR EARLY
NEXT WEEK...AND WITH THERMAL TROUGHING STILL PERSISTING ACROSS THE
STATE TUESDAY WITH 850MB TEMPERATURES POSSIBLY FLIRTING WITH
-10C...SO WILL CONTINUE THE POTENTIAL FOR LAKE INDUCED SNOW SHOWERS
TUESDAY IN GENERAL WESTERLY FLOW AREAS... AND START THE WEDNESDAY
FORECAST OUT DRY THOUGH THAT MAY CHANGE IF WARM ADVECTION PATTERN
FORECAST IS THE CORRECT IDEA. WILL TREND TEMPERATURES DOWNWARD FROM
MONDAY ONWARD.
JPB
&&
.MARINE.../ISSUED AT 403 PM/
SURFACE LOW IN THE VICINITY OF GRAND TRAVERSE BAY AT MID AFTERNOON
DRIFTING NORTHEAST TOWARD A LARGE 2-3MB/3H PRESSURE FALL AREA ACROSS
NORTHEAST ONTARIO/NORTHWEST QUEBEC. LOW EXPECTED TO LINGER IN THE
VICINITY OF NORTHERN LAKE HURON/NORTH CHANNEL THANKSGIVING DAY...
WITH AN INCREASING NORTH/NORTHWEST GRADIENT DEVELOPING ON LAKES
SUPERIOR/MICHIGAN THURSDAY...AND SLIDING INTO LAKE HURON THURSDAY
NIGHT. SMALL CRAFT ADVISORIES WILL LIKELY BE REQUIRED AT LEAST ON
WITHIN LAKE MICHIGAN NEARSHORE ZONES BY THURSDAY AFTERNOON (WHICH
WILL ISSUE WITH THE AFTERNOON NEARSHORE FORECAST)...AND AT LEAST IN
THE NEARSHORE ZONES FROM FALSE DETOUR CHANNEL AROUND TO PRESQUE ISLE
LIGHT BY THURSDAY NIGHT. SMALL CRAFT CONDITIONS EXPECTED TO LAST
INTO FRIDAY BEFORE SURFACE RIDGE AXIS SLIDES INTO THE UPPER LAKES
AND ALLOWS WINDS TO SLACK OFF BY FRIDAY EVENING.
JPB
&&
.AVIATION.../ISSUED AT 624 PM/...VALID FOR 00Z TAFS
UPPER LEVEL TROF WILL SLIDE SLOWLY ACROSS MICHIGAN THROUGH
THURSDAY...AS A WEAK AREA OF SURFACE LOW PRESSURE DEVELOPS OVER
LAKE HURON. WIDESPREAD RAIN OVERSPREADING ALL TAF SITES BETWEEN
06Z-12Z...CONTINUING THROUGH MUCH OF THE DAY ON THURSDAY. CIGS/VBYS
GRADUALLY DECREASING FROM MVFR TOWARD IFR OVERNIGHT...AS RAIN...STRATUS
AND FOG DEVELOP. AREAS OF LIFR CIGS POSSIBLE...ESPECIALLY AT KTVC
AND KPLN.
JK
&&
.APX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LM...SMALL CRAFT ADVISORY FROM 11 AM THURSDAY TO 11 AM EST FRIDAY FOR
LMZ323-341-342-344>346.
LH...NONE.
LS...NONE.
&&
$$
