000
FXUS63 KDTX 172342
AFDDTX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
742 PM EDT WED MAR 17 2010
.AVIATION...
VFR CONDITIONS WILL CONTINUE THROUGH THE TAF PERIOD WITH A VERY
DRY AIR MASS IN PLACE ACROSS THE REGION. WINDS WILL BE GENERALLY
LIGHT AND WESTERLY THROUGH THE OVERNIGHT PERIOD. HOWEVER...THEY
WILL BEGIN TO INCREASE TOMORROW AFTERNOON AS THE PRESSURE GRADIENT
TIGHTENS AND STRONGER WINDS MIX DOWN TO THE SURFACE.
&&
.PREV DISCUSSION...ISSUED 402 PM EDT WED MAR 17 2010
SHORT TERM...TONIGHT
SURFACE RIDGE OVER AREA WILL DROP SOUTH TONIGHT. VERY DRY AIRMASS
WILL REMAIN IN PLACE OVERNIGHT WITH THE SKY REMAINING CLEAR. WITH
DEWPOINTS GENERALLY IN THE TEENS ALONG WITH CLEAR SKIES AND LIGHT
WINDS...TEMPERATURES SHOULD DROP SHARPLY AFTER SUNSET. GUIDANCE HAS
BEEN TOO HIGH ON THE LOWS THE PAST COUPLE OF NIGHTS. EVEN WITH
SLIGHT WARM AIR ADVECTION ALOFT...RADIATIONAL COOLING SHOULD STILL
BE GREAT ENOUGH TO DROP LOWS A FEW DEGREES BELOW GUIDANCE. WILL
UNDERCUT GUIDANCE NUMBERS A COUPLE OF DEGREES AND SEE LOWS RANGE
ANYWHERE FROM THE UPPER 20S MAINLY IN SHELTERED AREAS TO THE MID 30S
IN THE CITY.
LONG TERM...THURSDAY THROUGH NEXT WEDNESDAY
UPPER SHORTWAVE CURRENTLY OVER ALBERTA WILL TRACK EAST THROUGH THE
NORTHERN GREAT LAKES THURSDAY AND THURSDAY NIGHT. MAIN IMPACT TO
SOUTHEAST MICHIGAN WILL BE AN INCREASE IN WEST-SOUTHWEST WINDS
TOMORROW. WITH GOOD MIXING EXPECTED...HAVE CONTINUED TO FORECAST
ABOVE MOS...WITH FORECAST HIGHS FOR MOST LOCATIONS IN THE MID 60S.
SHOULD ALSO MIX INTO A GOOD WIND CORE OF 25 KNOTS ALOFT...WITH THESE
GUSTS EXPECTED TO TUMBLE DOWN TO THE SURFACE IN THE AFTERNOON.
HUMIDITIES WILL ALSO FALL QUITE LOW TOMORROW AFTERNOON...WITH MINS
IN THE LOW TO MID 20S.
UPPER AIR PATTERN OVER THE GREAT LAKES WILL START TO CHANGE ON
FRIDAY AS SHORTWAVE ENERGY ORIGINATING OVER THE GULF OF ALASKA DIVES
THROUGH THE CENTRAL ROCKIES AND THEN TRACKS EAST ACROSS THE EASTERN
U.S. MEANWHILE...SHORTWAVE ENERGY CURRENTLY OVER THE NORTHWEST
TERRITORIES/NUNAVUT WILL DIVE SOUTH AND FORM A FAIRLY DEEP TROUGH
EXTENDING FROM THE GREAT LAKES TO THE GULF COAST. MODELS HAVE SHOWN
A WIDE RANGE OF VARIABILITY OVER THE PAST FEW DAYS WITH TIMING AND
PLACEMENT OF BOTH THESE FEATURES...AND ALSO VARY WITH HOW MUCH
INTERACTION THESE TWO SYSTEMS HAVE. THIS UNFORTUNATELY LEADS TO A
GOOD DEAL OF UNCERTAINTY WITH THE FORECAST BY SATURDAY AND SUNDAY.
CURRENT IDEA IS FOR A BAROCLINIC ZONE TO STRETCH FROM THE DEPARTING
LOW OVER THE NORTHERN GREAT LAKES BACK INTO THE SOUTHERN PLAINS BY
FRIDAY. THIS BOUNDARY WILL SLOWLY PUSH SOUTH AND EAST THROUGH THE
WEEKEND. MODELS REMAIN IN STRONG AGREEMENT WITH EXCELLENT
CONVERGENCE DEVELOPING ALONG THE FRONT OVER MICHIGAN DURING THE
WEEKEND...WITH VERY COLD AIR PUSHING DOWN ON THE NORTH SIDE AND WARM
AIR ADVECTION OCCURRING ON THE SOUTH SIDE. THIS WILL BRING A VERY
TIGHT TEMPERATURES GRADIENT ACROSS CENTRAL LOWER MICHIGAN OVER THE
WEEKEND. WOULD ALSO EXPECT TO SEE A GOOD PUSH OF MOISTURE
SATURDAY/SUNDAY AS THIS SYSTEM TAPS INTO GULF MOISTURE.
PRECIPITATION IS LIKELY...HOWEVER HOW TIMING...AMOUNT...AND TYPE ARE
STILL VERY MUCH IN QUESTION.
MODEL CONSENSUS STILL MATCHES GOING FORECAST FAIRLY WELL...WITH BEST
CHANCES FOR PRECIPITATION STARTING ON SATURDAY AND CONTINUING INTO
SUNDAY. THERE IS A POTENTIAL FOR ACCUMULATING SNOWFALL...HOWEVER HOW
FAR SOUTH THE RAIN/SNOW LINE DROPS WILL BE EXTREMELY DEPENDENT ON
WHERE THE FRONT SETTLES OVER THE REGION...WITH AMOUNTS MORE
DETERMINED BY HOW QUICKLY THIS FEATURE EXITS TO OUR SOUTHEAST. WILL
LIKELY SEE SOME CHANGES TO THE FORECAST AS THIS SYSTEM DRAWS CLOSER
AND BETTER UPPER AIR SAMPLING OF THE VARIOUS SHORTWAVES AND JET
STREAKS OCCURS.
AFTER A PROLONGED STRETCH OF LONG DRY WEATHER...WILL SEE
TEMPERATURES FALL FOR THE WEEKEND...WITH LOCATIONS ON THE NORTH SIDE
OF THE FRONT (CURRENTLY THINKING THE TRI-CITIES AND THUMB) ONLY
PEAKING INTO THE UPPER 30S TO LOW 40S FOR HIGHS BY SUNDAY.
MODELS ALL WANT TO PUSH A CLIPPER THROUGH LATE SUNDAY INTO
MONDAY...THOUGH SOME RUNS ARE PHASING THIS WITH THE LARGER SYSTEM
AHEAD OF IT. EITHER WAY...WILL SEE GUSTY WINDS AND ADDITIONAL COLD
AIR SPILL IN FOR MONDAY. THIS SHOULD DROP EVERYONE INTO THE 30S FOR
HIGHS.
HIGH PRESSURE IS ADVERTISED TO BUILD OVER THE CENTRAL GREAT LAKES
FOR THE MID-WEEK PERIOD. THIS SHOULD WARM HIGHS BACK UP TO NEAR
NORMAL BY TUESDAY.
MARINE...
SURFACE GRADIENT WILL TIGHTEN AS SURFACE RIDGE SLIDES TO THE SOUTH.
THIS WILL BRING A SLIGHT INCREASE IN SOUTHWESTERLY FLOW OVER THE
LAKES. WINDS WILL SHIFT TO THE NORTH AS A WEAK COLD FRONT DROPS
THROUGH ON FRIDAY. A STORM SYSTEM WILL EFFECT THE AREA SATURDAY AND
SUNDAY BRINGING THE POSSIBILITY OF SNOW OVER LAKE HURON. AS THIS
SYSTEM DEPARTS...A STRONG NORTHWESTERLY FLOW WILL DEVELOP SUNDAY
NIGHT AND MONDAY BRINGING SMALL CRAFT CONDITIONS TO THE NEARSHORES
AND GUSTS TO 30 KNOTS POSSIBLE OVER THE OPEN WATERS OF LAKE HURON.
&&
.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LAKE HURON...NONE.
LAKE ST CLAIR...NONE.
MI WATERS OF LAKE ERIE...NONE.
&&
$$
AVIATION.....AGD
SHORT TERM...DRX
LONG TERM....HLO
MARINE.......DRC
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AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE).
