Heavy Snow in Michigan, January 17 to 18, 2009

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GAYLORD MI
326 AM EST FRI JAN 16 2009

.SYNOPSIS.../ISSUED AT 326 AM/

A LOW PRESSURE SYSTEM WILL MOVE INTO LOWER MICHIGAN TONIGHT. SNOW
WILL DEVELOP OUT AHEAD OF THIS SYSTEM...AND WILL BE HEAVY IN SOME
PORTIONS OF LOWER MICHIGAN. SNOW WILL SLOWLY DIMINISH TONIGHT...BUT
SNOW SHOWERS WILL LINGER NEAR SOME OF THE GREAT LAKES COASTLINE.

&&

.SHORT TERM.../ISSUED AT 326 AM/...TODAY

SHORTWAVE ADVANCING ACROSS MANITOBA/ONTARIO BORDER REGION. THIS WAVE
WILL AMPLIFY...AND CLOSE OFF OVERHEAD BY MIDNIGHT. SURFACE LOW IS
NEAR ND/MN BORDER...WITH A WARM FRONT EXTENDING SOUTH TO EASTERN KS.
THE LOW WILL DEEPEN LATE TODAY AS IT REACHES LAKE MI BY EVENING.
SNOW AMOUNTS AND ASSOCIATED HEADLINES ARE THE MAIN CONCERN.

THERE ISN/T ALL THAT MUCH SNOW UPSTREAM NOW...MAINLY FROM THE FAR
UPPER MS VALLEY ON UP INTO WESTERN ONTARIO. HOWEVER...AS THE UPPER
SYSTEM AMPLIFIES AND SLOWS...SNOW WILL INTENSIFY AND EXPAND.
ISENTROPIC ASCENT (285K) LASTS THRU THE DAY...WITH ONE SURGE AROUND
DAYBREAK (WHICH WILL GET PRECIP STARTED)...AND ANOTHER THIS
AFTERNOON. STRONGEST ASCENT IN THE PM APPEARS TO PASS JUST TO OUR
SOUTH. 700-600MB FGEN MAX MOVES ACROSS THE SOUTH HALF OF THE
FORECAST AREA THRU 18Z...AGAIN FAVORING THE BEST ASCENT TO OUR
SOUTH. 700-600MB Q-VECTOR CONVERGENCE MAX IS CENTERED OVER THE HEART
OF CENTRAL LOWER MI AT 18Z...TRANSITING THE AREA FROM W TO E.

SNOW WILL EXPAND ACROSS THE ENTIRE FORECAST DURING THE MORNING AND
MIDDAY HOURS. CERTAINLY PLENTY COLD ENOUGH FOR LAKE ENHANCEMENT.
HOWEVER...THRU 18Z 1000-850MB WINDS ARE DUE SOUTH ACROSS MOST OF THE
REGION...WHICH IS NOT IDEAL...PROVIDING A SOMEWHAT LIMITED FETCH FOR
ENHANCEMENT EVEN IN FAR WESTERN MACKINAC CO. INDEED...THE NAM
RESOLVES A LAKE-ENHANCED BAND POKING UP INTO SCHOOLCRAFT CO. ONE
POTENTIAL TRICKY SPOT WILL BE CENTRAL LAKE MI...WHERE A SSW FETCH
MAY GIVE THE IMMEDIATE COAST FROM THE DUNES SOUTHWARD SOME
ENHANCEMENT. THIS IS ESPECIALLY THE CASE MID/LATE AFTERNOON...WHEN
THE APPROACHING SURFACE LOW BRINGS A BOOST IN 1000-850MB
CONVERGENCE...AND WINDS START TO VEER MORE SW.

ONE CONCERN IS THAT MODEL PROGGED SOUNDINGS SHOW A RELATIVELY DEEP
ISOTHERMAL LAYER AROUND -15C FROM THE SURFACE UP THRU 650MB. THIS IS
THE HEART OF THE DENDRITIC GROWTH ZONE...AND WOULD FAVOR BIG FLUFFY
FLAKE PRODUCTION AND POTENTIALLY QUITE HIGH SNOW/LIQUID RATIOS. HAVE
ADJUSTED RATIOS UPWARD TO BETWEEN 20/1 AND 25/1. GIVEN RATHER
LENGTHY PERIOD OF MODERATE FORCING FOR ASCENT...AND WE END UP WITH
SOMETHING AROUND 6 INCHES OF SNOW IN THE SW THIRD OF THE FORECAST
AREA...DWINDLING TO AROUND 2 INCHES NEAR THE SAULT.

PER EXTENSIVE COORDINATION WITH GRR/DTX...WILL ISSUE A WINTER STORM
WARNING FOR ROUGHLY THE SW THIRD OF THE FORECAST AREA...FROM LELAND
TO OSCODA AND SOUTH. THAT WARNING WILL RUN THRU 5 AM TONIGHT...WHICH
MAY BE A BIT LONG BUT BETTER TO ERR ON THE SIDE OF CAUTION.
ADVISORIES WILL RUN FOR EVERY OTHER COUNTY BUT CHIPPEWA.

JZ

&&

.LONG TERM.../ISSUED AT 326 AM/...TONIGHT AND BEYOND

AN ARCTIC SHORTWAVE WILL DROP INTO THE UPPER LOW CARVED OUT BY THE
STALLING CLIPPER. THE UPPER LOW WILL ONLY MAKE VERY SLOW PROGRESS
OVER THE EASTERN LAKES THRU MONDAY. THE ASSOCIATED SURFACE LOW WILL
REACH SOUTHERN LAKE HURON BY SUNDAY MORNING...AND START TO FIZZLE
OUT NEAR LAKE ONTARIO BY MONDAY MORNING AS ENERGY TRANSFERS TO THE
EAST COAST. SNOW CHANCES THRU SUNDAY WITH THIS SLOW-MOVING SYSTEM
ARE THE MAIN CHALLENGE.

MODELS...GOOD AGREEMENT ON THE BASIC PATTERN. LOTS OF DIFFS IN THE
DETAILS...ESPECIALLY ON MONDAY...WHEN THE GFS HAS A REASONABLY
VIGOROUS ARCTIC SHORTWAVE DROPPING IN FROM THE NORTH. THE NAM STILL
HAS THIS UP TOWARD HUDSON BAY...THE ECMWF HAS IT DOWN HERE BUT
LARGELY WEST OF LAKE MI. WILL FOR NOW TAKE THE POSITION THAT THIS
WAVE WILL NOT HAVE A MAJOR IMPACT (IT IS RATHER MOISTURE STARVED IN
ANY CIRCUMSTANCE).

TONIGHT...LIGHT SYNOPTIC SNOW WILL PERSIST THRU THE EVENING...THEN
ERODE OVERNIGHT AS FORCING EXITS TO THE EAST. STILL A TREMENDOUS
AMOUNT OF MOISTURE AROUND THOUGH (850-700MB RH ABOVE 80 PERCENT). SO
LAKE EFFECT SNOW SHOWERS WILL CONTINUE WHERE WINDS WILL BE ONSHORE.
A LINGERING SURFACE TROF AXIS OVER THE SOUTHERN PORTION OF THE
FORECAST AREA WILL PRODUCE SOME RATHER SHARP CYCLONIC CURVATURE...
BUT ALSO LIMIT ONSHORE FLOW. MAINLY IMPACTED IS NEAR/NORTH OF APN ON
THE HURON COAST...AND NEAR/SOUTH OF NORTHPORT ON LAKE MI. SNOW
AMOUNTS WILL BE LESS THAN AN INCH NEAR/NORTH OF THE BRIDGE...UP TO
AROUND 2 EAST OF M-33 IN NE LOWER...AND NEAR THE LAKE MI COAST IN
THE SW. MIN TEMPS WILL LOWER TO SINGLE DIGITS IN EASTERN UPPER AND
THE INTERIOR...AND HOLD AROUND 10 ALONG NORTHERN LOWER COASTS.

SUNDAY...LOW LEVEL N TO NE FLOW WILL TAKE HOLD ACROSS THE ENTIRE
FORECAST AREA...AS THE SURFACE LOW FINALLY PULLS EAST FROM LAKE
HURON. THE LOW AND MID LEVELS REMAIN QUITE MOIST...THOUGH WITH SOME
DRYING JUST UPSTREAM ON SUPERIOR BY EVENING. THE FLOW AND 850MB
TEMPS NEAR -17C WILL SUPPORT NUMEROUS SNOW SHOWERS IN NE LOWER MI
(WITH LOCAL 1-3 INCH ACCUMS)...AND FROM LEELANAU SOUTHWARD. CHANCE
POPS ELSEWHERE. MAX TEMPS MAINLY IN THE TEENS...NEAR 20 ALONG SOME
OF THE COASTS.

SUNDAY NIGHT/MONDAY...AS THE UPPER TROF SLOWLY DRIFTS EAST...AND THE
NEAREST SURFACE LOW FILLS...DRIER AIR WILL GRADUALLY ENTER THE
REGION FROM THE NORTH. THE PERSISTENT NNE 1000-850MB FETCH SUNDAY
NIGHT IS A QUIET ONE...ESPECIALLY GIVEN THE DRYING TREND (850-700MB
RH LEVELS BELOW 50 PERCENT BY 12Z). WILL KEEP POPS CHANCY NEAR HURON
AND LAKE MI...AND TRY TO GET AWAY WITH A DRY NIGHT IN THE INTERIOR
AND EASTERN UPPER. MONDAY IS HIGHLY DEPENDENT ON AN ARCTIC SHORTWAVE
THAT MAY OR MAY NOT DROP IN FROM THE NORTH. THE GFS IS SUGGESTING
WINDS WILL BACK TO THE NW...AND ALLOW FOR LAKE EFFECT TO RETURN TO
THE CLASSIC SNOWBELTS IN THE PM. WILL NOT GO NUTS WITH THIS...
KEEPING POPS JUST CHANCY UNTIL WE GET A BETTER HANDLE ON THIS
SYSTEM. MIN TEMPS SINGLE DIGITS TO AROUND ZERO...MAX TEMPS TEENS.

JZ

MONDAY NIGHT ONWARD...THE AMPLIFIED EASTERN CONUS TROF WILL FINALLY
BEGIN TO LIFT OUT...ALTHOUGH A WEAKER TROF WILL REMAIN ACROSS THE
GREAT LAKES REGION PROVIDING ROOM FOR MORE CLIPPER SYSTEMS TO DROP
SOUTHWARD THROUGH THE AREA...PRODUCING PERIODIC CHANCES FOR LIGHT
SNOW THROUGH THE REMAINDER OF THE WEEK. TEMPERATURES WILL CONTINUE
TO MODERATE THROUGH MIDWEEK...BEFORE A POTENT WAVE ON THURSDAY DRAGS
ANOTHER BLAST OF COLD AIR INTO THE REGION BY THE END OF THE WEEK
WHICH MAY BE REINFORCED BY ANOTHER CLIPPER SYSTEM EARLY NEXT
WEEKEND.  KAS

&&

.MARINE.../ISSUED AT 326 AM/

GUSTY SOUTHWEST TO SOUTH WINDS WILL CONTINUE TO PRODUCE SMALL CRAFT
WINDS AND WAVES OVER THE LAKE MICHIGAN NEARSHORE AREAS TODAY.

ADAM

&&

.AVIATION.../ISSUED AT 1143 PM/...VALID FOR 06Z TAFS

SCT LIGHT LAKE EFFECT SNOW SHOWERS AND CLOUDS WILL CONTINUE TO
IMPACT PORTIONS OF NW LWR MICHIGAN OVERNIGHT...ESPECIALLY AROUND
KPLN UNDER THE DIRECTION OF SW LOW LEVEL FLOW. OVERALL CONDITIONS
WILL REMAIN VFR ACROSS THE REST OF NRN LWR MICHIGAN THRU THE NIGHT.
HEAVIER SNOWFALL AND MVFR/IFR CONDITIONS RETURN FOR ALL 3 TERMINAL
SITES BETWEEN 10Z AND 13Z SATURDAY MORNING AS ANOTHER AREA OF LOW
PRESSURE SWINGS SE THRU MICHIGAN. WIDESPREAD SNOWFALL WILL PERSIST
FOR THE REST OF THE DAY AND INTO THE EVENING...WITH MVFR TO AT TIMES
IFR CONDITIONS EXPECTED.

&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...WINTER STORM WARNING FROM 7 AM THIS MORNING TO 5 AM EST SUNDAY
     FOR MIZ020-021-025>029-031>036-041-042.
     WINTER WEATHER ADVISORY FROM 7 AM THIS MORNING TO 11 PM EST THIS
     EVENING FOR MIZ015>019-022>024-030.
LM...SMALL CRAFT ADVISORY UNTIL 5 PM EST THIS AFTERNOON FOR LMZ323-
     342-344>346.
LH...NONE.
LS...NONE.

&&

<!doctype html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <title>Service Notice</title>
  <link rel="stylesheet" href="index.css">
</head>
<body>
  <main class="wrap">
    <section class="card" role="status" aria-live="polite">
      <div class="status" id="status">Temporary Notice</div>
      <h1 id="headline">This service is currently unavailable.</h1>
      <p id="message1">
        The site you requested is temporarily down for maintenance or an unexpected outage.
      </p>
      <p id="message2">
        Please try again in a few minutes.
      </p>
      <p class="small" id="detail">
        If you are an administrator, restore upstream service and remove the redirect/fallback rule when normal operations resume.
      </p>
    </section>
  </main>
  <script src="index.js"></script>
</body>
</html>