Area Forecast Discussion
Issued by NWS Gaylord, MI

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000
FXUS63 KAPX 220151
AFDAPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GAYLORD MI
951 PM EDT TUE APR 21 2015

.UPDATE...
ISSUED AT 950 PM EDT TUE APR 21 2015

FAIRLY DIFFICULT PCPN TYPE FORECAST ACRS NRN MI TONIGHT...AS SFC
BASED WARM TEMPS COMBINE WITH COOLING TEMPERATURES ALOFT. THE
FORECAST TONIGHT SEEMS MORE LIKE OCTOBER THAN LATE APRIL.

SFC AND UPPER LVL LOWS LOCATED BETWEEN LAKE SUPERIOR AND JAMES BAY
THIS EVENING...WILL REMAIN NEARLY STATIONARY THROUGH WEDNESDAY
MORNING. THIS PATTERN WILL CONTINUE TO FORCE COLD AIR INTO THE GREAT
LAKES THROUGH WEDNESDAY AFTERNOON. 850MB TEMPS ARND -5C THIS EVENING
WILL DROP TO AROUND -9C BY 12Z WED...BEFORE DROPPING TO -12C BY 18Z
WED AFTN. THE OVERALL PATTERN SUGGESTS SYNOPTIC DRIVEN SNOW THIS
EVENING WILL BECOME MORE LAKE ENHANCED OVERNIGHT AND WEDNESDAY
MORNING...AS THE MID LVL COLD POOL SETTLES OVER NRN MI (NRN LAKE MI
WATER TEMPS LINGER ARND +2C COMBINING WITH 850MB TEMPS FALLING TO
AROUND -12C BY 12Z WED). MODEL SOUNDINGS SHOW LOW LVL INVERSION
INCREASING TO ARND 5K FT OVERNIGHT AS COLDEST MID LVL TEMPS SETTLE
OVERHEAD. HOWEVER...MODEL SOUNDINGS DO SHOW SFC BASED TEMPS WARM
ENOUGH TO CONTINUE A RAIN/SNOW MIX LINGERING ALONG THE GREAT LAKES
SHORELINE THROUGH THE OVERNIGHT HOURS.

OVERALL WILL CONTINUE A WINTRY MIX OF RAIN/SNOW ALONG THE GREAT
LAKES SHORELINE OVERNIGHT. WILL MENTION WINTRY MIX OVER ERN UPPER
AND THE HIGHER ELEVATIONS THIS EVENING TRENDING TO ALL SNOW
OVERNIGHT AND LINGERING INTO WEDNESDAY MORNING. ALL SNOWFALL SHOULD
REMAIN UNDER 2 INCHES OVERNIGHT.

&&

.NEAR TERM...(THIS EVENING THROUGH TONIGHT)
ISSUED AT 344 PM EDT TUE APR 21 2015

HIGH IMPACT WEATHER: MINIMAL

FORECAST CHALLENGE: DETERMINING THE RAIN/SNOW MIX.

OVERVIEW...500 MB COLD POOL IS PRODUCING DIURNALLY DRIVEN SHOWERS
AND CLOUDS OVER THE UPPER GREAT LAKES. MORE MOISTURE AS EVIDENT ON
THE WATER VAPOR IMAGE IS UPSTREAM ON THE BACK SIDE OF THE 500 MB
LOW, AND WILL ROTATE AROUND FROM N MINNESOTA INTO WISCONSIN AND OVER
N MICHIGAN OVERNIGHT. 850 MB TEMPERATURES ARE RUNNING -6C UPSTREAM
OF THE STATE WITH THE -10 TO -11C TEMPERATURES IN THE BOUNDARY
WATERS REGION. WHILE THE MAJORITY OF THE AIRPORT OBS HAVE SAID RAIN,
THERE IS A MIX OR ALL SNOW IN SOME LOCALES.

DETAILS FOR TONIGHT...THE SHOWERY ACTIVITY WITH A MIX OF RAIN AND
SNOW WILL CONTINUE INTO THE EVENING, AS THE DIURNALLY DRIVEN
ELEMENTS SUBSIDE FROM THE LACK OF DAYTIME HEATING. AS THE NEXT SURGE
OF MOISTURE MOVES INTO THE FORECAST OVERNIGHT, WITH THE -9C TO -10C
AIR, WILL EXPECT THAT LIGHT RAIN/SNOW, OF A LESS CONVECTIVE NATURE
WILL MOVE INTO THE REGION. AS ANOTHER SFC TROUGH DROPS THROUGH
AROUND 00Z. ONCE THE TROUGH DROPS THROUGH, THE WINDS SHIFT TO THE NW
AROUND 00Z. BY 12Z, THE 850 MB TEMPERATURES FALL TO AROUND -10C OVER
N LAKE MICHIGAN. WATER TEMPERATURES ARE AROUND +3C, SO WILL EXPECT
THAT THERE WILL BE SOME LAKE ENHANCEMENT, IN THE LAKE BELTS OF E
UPPER AND NW LOWER. HOWEVER, WITH THE DELTA TS BELOW 13C, MOST OF
THE TIME, WILL EXPECT THAT THE ACCUMULATIONS WILL BE MINOR TO LIGHT
AS THE SYSTEM MOVES EAST INTO QUEBEC.

&&

.SHORT TERM...(WEDNESDAY THROUGH FRIDAY)
ISSUED AT 344 PM EDT TUE APR 21 2015

...COOL AND SHOWERY FOR THE NEXT FEW DAYS...

PATTERN OVERVIEW/FORECAST: MORNING HEMISPHERIC ANALYSIS REVEALS A
PATTERN A BIT MORE REMINISCENT OF A MONTH AGO...WITH RIDGING ALONG
THE WEST COAST OF NORTH AMERICA AND LONG WAVE TROUGHING DOWNSTREAM
THROUGH THE CENTRAL AND EASTERN CONUS. DEEP CLOSED UPPER LOW RESIDES
OVER UPPER MICHIGAN WITH A POCKET OF FAIRLY COLD AIR ALOFT (-13C AT
PICKLE LAKE ONTARIO) POISED ACROSS ONTARIO...AND DEEP CYCLONIC
FLOW/AMPLE MOISTURE ROTATING THROUGH THE REGION. COUPLED WITH A
CORRIDOR OF MODEST FORCING/CHANNELED VORTICITY STRETCHING FROM
WISCONSIN ACROSS LOWER MICHIGAN...POCKETS OF SHOWERS CONTINUE TO
ROTATE THROUGH MUCH OF THE REGION. STRONGER DEFORMATION FORCING/MORE
WIDESPREAD PRECIPITATION (SNOW!) IS IN PLAY ACROSS WESTERN ONTARIO
ALONG THE BACKSIDE OF THE LOW.

THIS COLD/SHOWERY PATTERN IS UNFORTUNATELY GOING TO STICK WITH US
FOR THE NEXT FEW DAYS ANYWAY...MAINTAINING THIS SHOWERY/COOL WEATHER
AND...SOME SNOW CHANCES.

WEDNESDAY/WEDNESDAY NIGHT/THURSDAY...MORE OF THE SAME. CLOSED UPPER
LOW VERY SLOWLY DRIFTS INTO SW ONTARIO WHILE DRAGGING CORE OF
COLDEST AIR (-10C TO -12C 850 MB AIR) DOWN INTO NRN MICHIGAN ON
WEDNESDAY. LIKE TODAY...STRONGEST DEFORMATION FORCING STAYS FOCUSED
NORTH OF THE REGION ACROSS ONTARIO...AND SUBTLE MID LEVEL WARMING
(ABOVE 700 MB)/RELAXING CYCLONIC FLOW/SUBSIDENCE DOES BRING
INVERSION HEIGHTS BACK DOWN TO UNDER 750 MB (COMPARED TO OUR VIRTUAL
LACK OF AN INVERSION TODAY). BUT WITH -10C TO -12C H8 AIR SLIDING
ACROSS NRN MICHIGAN...WE SHOULD GET NW FLOW LAKE SNOW SHOWERS GOING
WEDNESDAY MORNING THAT EVENTUALLY BECOME MORE DIFFUSE/SPREAD OUT AND
CHANGE BACK TO RAIN OR MIXED RAIN/SNOW SHOWERS THROUGH THE AFTERNOON
DUE TO "HEATING" OF THE DAY. BACK TO A LITTLE BETTER ORGANIZED NW
LAKE EFFECT SNOW/MIXED RAIN AND SNOW SHOWERS WEDNESDAY NIGHT INTO
THURSDAY MORNING...WITH SOME LIGHT ACCUMULATIONS (AROUND AN INCH
PERHAPS) ACROSS THE HIGHER TERRAIN.

THURSDAY NIGHT AND FRIDAY...IMPROVEMENT FINALLY. UPPER LOW MOVES OFF
TO NEW ENGLAND WHILE SUBTLE SHORT WAVE RIDGING/WARMER AIR NOSES INTO
THE UPPER MIDWEST/WESTERN GREAT LAKES THROUGH FRIDAY. DRYING/WARMING
ALOFT/INCREASING SUNSHINE WILL BRING AN END TO OUR SHOWERY PRECIP BY
FRIDAY WITH DAYTIME TEMPS MAKING A REBOUND INTO THE 40S FOR FRIDAY.

&&

.LONG TERM...(FRIDAY NIGHT THROUGH TUESDAY)
ISSUED AT 344 PM EDT TUE APR 21 2015

AN IMPROVEMENT OVER THE WORK WEEK LOOKS TO BE ON TAP FOR THE WEEKEND
ACROSS NORTHERN MICHIGAN. WITH UPPER LEVEL TROUGHING CONTINUING TO
SHIFT EASTWARD THROUGH THE WEEKEND AND NO REAL SIGNS OF ANY WEAK
DISTURBANCES ON THE HORIZON TO KICK OFF ANY SHOWER ACTIVITY...WILL
GO AHEAD AND CONTINUE A DRY FORECAST FROM FRIDAY NIGHT THROUGH
MONDAY. THE NEXT SYSTEM OF INTEREST ARRIVES NEAR THE VERY TAIL END
OF THE PERIOD AS LOW PRESSURE BEGINS TO DEVELOP OVER SOUTHWESTERN
CANADA ON MONDAY BEFORE DROPPING INTO THE NORTHERN PLAINS/GREAT
LAKES REGION ON TUESDAY. AT THIS POINT...WILL GO AHEAD AND INTRODUCE
LOW POPS FOR LATE MONDAY NIGHT - TUESDAY...BUT WITH NEARLY A WEEK
FOR THIS TO UNFOLD... MANY QUESTIONS REMAIN IN TERMS OF THE
DEVELOPMENT AND POSITIONING OF THE SYSTEM.

IN TERMS OF TEMPERATURES...BELOW NORMAL READINGS ARE EXPECTED TO
CONTINUE THROUGH THE PERIOD WITH THE WARMEST DAYS COMING LATE IN THE
WEEKEND INTO EARLY NEXT WEEK WHERE A BLENDED GUIDANCE APPROACH
SUGGESTS TEMPERATURES MAY TAG THE LOW-MIDDLE 50S FOR DAYTIME
HIGHS.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z WEDNESDAY EVENING)
ISSUED AT 650 PM EDT TUE APR 21 2015

SFC AND UPPER LVL LOWS CURRENTLY LOCATED BTWN LAKE SUPERIOR AND
JAMES BAY...WILL REMAIN NEARLY STATIONARY THROUGH THE TAF PERIOD.
COLD AIR FILTERING INTO THE GREAT LAKES AGAIN TONIGHT WILL TRANSIT
ANY WINTRY MIXED PCPN THIS EVENING TO MAINLY SNOW...ACRS NRN MI TAFS
SITES INTO WEDNESDAY MORNING. BASED ON CURRENT SATELLITE TRENDS AND
SFC OBS...WILL CONTINUE MAINLY MVFR CIGS AND VSBY ACROSS NRN MI TAF
SITES THROUGH WED AFTN.


&&

.MARINE...
ISSUED AT 344 PM EDT TUE APR 21 2015

TONIGHT THROUGH THURSDAY...AS THE SECONDARY SFC TROUGH MOVES
THROUGH THE UPPER GREAT LAKES THIS EVENING, WILL EXPECT THAT THE
WINDS WILL TAKE A BRIEF BREAK. HOWEVER, ONCE THROUGH, THE GRADIENT
SHOULD TIGHTEN UP BEHIND IT. SO WILL KEEP THE SMALL CRAFT ADVISORY
UP TONIGHT, EVEN THOUGH IN SOME SEGMENTS THE WINDS FALL BELOW
CRITERIA. HOWEVER, THE NW FLOW WILL CONTINUE, ESPECIALLY WITH THE
COOL AIR ALOFT, ALLOWING ENOUGH MIX FOR HIGHER WINDS TO BE MIXED
DOWN. TO THE SFC. WITH THIS COOL AIR MASS OVER THE REGION, THE
LOWER LEVELS WILL BE UNSTABLE ENOUGH, THAT THE SMALL CRAFT
CRITERIA WINDS WILL CONTINUE INTO THURSDAY.


&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LH...SMALL CRAFT ADVISORY UNTIL 6 PM EDT WEDNESDAY FOR LHZ345>347.

     SMALL CRAFT ADVISORY UNTIL 11 PM EDT THIS EVENING FOR LHZ349.

LM...SMALL CRAFT ADVISORY UNTIL 6 PM EDT WEDNESDAY FOR LMZ323-341-342-
     344>346.

LS...SMALL CRAFT ADVISORY FROM 2 AM TO 6 PM EDT WEDNESDAY FOR LSZ321-
     322.

&&

$$

UPDATE...SWR
NEAR TERM...JSL
SHORT TERM...ADAM
LONG TERM...GILLEN
AVIATION...SWR
MARINE...JSL



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