FXUS63 KDTX 012309
AFDDTX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
609 PM EST TUE DEC 1 2009
.AVIATION...
THE RESIDUAL STRATO CU HAS LIFTED NORTH OF MBS...LEAVING MAINLY
CLEAR SKIES ACROSS THE SOUTHERN MICHIGAN. THE PRESSURE GRADIENT
ASSOCIATED WITH A SURFACE LOW LIFTING ACROSS LAKE SUPERIOR TONIGHT
SHOULD MAINTAIN ENOUGH OF A GRADIENT TO PREVENT FOG DEVELOPMENT.
MAINLY HIGH CLOUDS ARE EXPECTED THROUGH WED AFTERNOON BEFORE
CONDITIONS RAPIDLY DETERIORATE WED EVENING AS THE STORM SYSTEM
OVER THE GULF OF MEXICO LIFTS INTO THE OHIO VALLEY/EASTERN GREAT
LAKES.
&&
.PREV DISCUSSION...ISSUED 400 PM EST TUE DEC 1 2009
SHORT TERM...THIS AFTERNOON AND TONIGHT
GEOPOTENTIAL HEIGHTS WILL BALLOON ACROSS NE NOAM TONIGHT IN RESPONSE
TO BOTH STRONG UPPER LEVEL CONFLUENCE NEAR THE EASTERN
SEABOARD...AND ORGANIZED HEIGHT FALLS IN VICINITY OF THE GULF COAST.
MEANWHILE...ANOTHER U/L JET CORE HARBORING THE NODAK SHORTWAVE WILL
SLIDE INTO THE GREAT LAKES...WITH IT A FAIRLY HEALTHY BOUT OF WARM
AIR ADVECTION. THIS THETA E BUBBLE...IN CONCERT WITH THE ARKLATEX
HEIGHT FALLS...WILL ALLOW THE RIDGE AXIS TO EMERGE NORTHWARD
ENCAPSULATING ALL OF THE FORECAST AREA INTO TOMORROW. INCREASING WAA
AT/AROUND 900MB TONIGHT WILL ERODE THE MIXED LAYER FROM TODAY AND
DESTROY THE BASE OF THE INVERSION. THEREFORE...EXPECTING THE
STRATUS/STRATOCUMULUS THAT HAS MIGRATED TO THE NW CWA TO DISSIPATE
AFTER SUNSET. FOR TONIGHT...ANTICIPATING MOSTLY CLEAR TO PARTLY
CLOUDY SKIES WITH PASSING HIGH CLOUDS STREAMING OCCASIONALLY ACROSS
LOWER MICHIGAN. INCREASING WAA ADVECTION AND REASONABLY MIXED FLOW
WILL KEEP LOWS IN CHECK...LOWER TO MIDDLE 30S.
LONG TERM...WEDNESDAY THROUGH NEXT TUESDAY
EXPECTATIONS OF MILD CONDITIONS OVER THE REGION ON WEDNESDAY ARE
SUPPORTED BY TEMPERATURES OBSERVED IN THE MID TO UPPER 50S AS CLOSE
BY AS ILLINOIS THIS AFTERNOON. THIS BODES WELL FOR HIGHS AT LEAST IN
THE LOWER 50S OVER THE SOUTH HALF OF OUR AREA ON WEDNESDAY EVEN
GIVEN THE INCREASED CLOUD COVER AND RAIN EXPECTED IN THE AFTERNOON.
THE WARMING TREND WILL BE AIDED BY SOUTHWEST WINDS AHEAD OF THE COLD
FRONT ASSOCIATED WITH LOW PRESSURE IN MINNESOTA TODAY. THIS FRONTAL
SYSTEM IS STILL EXPECTED TO STALL NEAR THE STRAITS AS THE GULF
SYSTEM MAKES IT MOVE TOWARD SE MICHIGAN DURING THE DAY. MILD AIR
WILL THEN REMAIN IN PLACE IN SE MICHIGAN AS MOISTURE ARRIVES FROM
THE GULF COAST SYSTEM. THE 12Z MODELS ARE IN GOOD AGREEMENT WITH
A PATTERN OF RAIN REACHING UP INTO THE SOUTH HALF OF THE AREA
DURING THE LATE AFTERNOON HOURS WHICH IS REFLECTED IN THE FORECAST
WITH LIKELY POPS INTO MONDAY EVENING.
REGARDING THE POTENTIAL FOR SNOW ACCUMULATION WEDNESDAY NIGHT INTO
THURSDAY, THE POINTS MADE IN THE MIDNIGHT SHIFT FORECAST CYCLE
REMAIN VALID IF NOT FURTHER SUPPORTED BY OBSERVATIONS TODAY. THE
MAIN CONSIDERATION BEING THE DEGREE OF WARMTH IN PLACE AHEAD OF THE
GULF SYSTEM AS IT MOVES INTO THE REGION AND THE RELATIVELY SLOW PACE
IN WHICH ANY COLDER AIR CAN BE DRAWN IN FROM THE DYING FRONT TO OUR
NORTH. NOTHING IN THE 12Z MODEL CYCLE HAS CHANGED EXPECTATIONS IN
THAT REGARD. IF ANYTHING, THE WARM TEMPERATURES OBSERVED TODAY ADDS
CONFIDENCE TO THE WARM BOUNDARY LAYER HOLDING WELL INTO THE EVENT
WHEN COMBINED WITH CONTRIBUTIONS FROM THE WARM GROUND AND WARM
WATERS OF THE GREAT LAKES. THERE REMAIN DIFFERENT MODEL OFFERINGS ON
THE TRACK AND STRENGTH OF THE LOW BUT THERE IS AGAIN NOT MUCH
DIFFERENT OCCURRING IN THE LARGE SCALE FLOW THAT WOULD SUPPORT A
FARTHER EAST SOLUTION. OUR FORECAST CONTINUES TO REFLECT A TRACK
THROUGH THE EASTERN HALF OF OHIO INTO SOUTHERN ONTARIO EAST OF
GEORGIAN BAY. SATELLITE IMAGERY SUGGESTS THE GULF LOW WILL VERIFY ON
THE STRONG SIDE AS IT IS KICKED TOWARD US BY THE LARGER SCALE HEIGHT
FALLS OVER THE NORTHERN PLAINS AND ROCKIES. THESE HEIGHT FALLS WILL
BE ASSOCIATED WITH A LONG WAVE RIDGE BUILDING OVER THE EAST HALF OF
CANADA. THE COMBINATION OF THIS LONG WAVE EVOLUTION AND THE STRENGTH
OF THE GULF LOW SUPPORTS A FARTHER WEST TRACK THAN THE 12Z GFS
WHICH, IF ANYTHING, WILL KEEP US IN THE WARMER AIR LONGER AS THE
SYSTEM MOVES THROUGH THE REGION. IN THE END, THE AFTERNOON FORECAST
PACKAGE MAKES LITTLE CHANGE TO THE OVERALL QPF BUT DOES BUMP DOWN
THE SNOWFALL ACCUMULATION ANOTHER NOTCH. THIS ALLOWS FOR ENOUGH
OF A CHANGE OVER TO SNOW FOR A SLUSHY INCH OF ACCUMULATION AS THE
COLD AIR FINALLY ARRIVES AND PRECIPITATION ENDS LATE WEDNESDAY
NIGHT THROUGH THURSDAY MORNING.
OPPORTUNITIES FOR ADDITIONAL MINOR ACCUMULATION ARE IN THE FORECAST
ON FRIDAY AS COLD AIR DEEPENS OVER THE SOUTHERN GREAT LAKES. THIS
WILL ACTIVATE SNOW SHOWERS UNDER THE COLD POOL OF THE UPPER TROUGH
ALONG WITH SOME LAKE EFFECT CONTRIBUTIONS. THE BULK OF THE LONG
WAVE TROUGH WILL THEN LINGER OVER LOWER MICHIGAN DURING SATURDAY
AND HELP MAINTAIN THE SNOW SHOWER PATTERN, BUT PROSPECTS FOR A
GREATER PRESENCE OF SOUTHWEST FLOW WILL REMOVE LAKE MICHIGAN FROM
THE PICTURE A LITTLE MORE AND KEEP THE ACTIVITY ON THE LIGHT SIDE
BEFORE THE UPPER TROUGH SHIFTS TOWARD THE EAST BY SUNDAY. THIS IS
SAID WITH SOME CONFIDENCE IN THE EVOLUTION OF THE LONG WAVE
PATTERN THROUGH THE WEEKEND. GLOBAL MODEL TRENDS ARE FAVORING THE
HIGHLY AMPLIFIED FLOW TAKING ON SOME BLOCKING CHARACTER FROM THE
NORTH PACIFIC THROUGH CENTRAL NORTH AMERICA. THIS RAISES
CONFIDENCE THAT THE LONG WAVE TROUGH WILL BE MAINTAINED OVER THE
ROCKIES AND PLAINS VIA A PROGRESSION OF SHORT WAVE FEATURES. AFTER
THE SHORT WAVE RIDGE ON SUNDAY, PREDICTABILITY IS LOW IN REGARD TO
TIMING AND INTENSITY OF THE SMALLER SCALE FEATURES MOVING INTO THE
GREAT LAKES BUT A CHANCE OF SNOW DOES LOOK APPROPRIATE FOR THE
BEGINNING OF NEXT WEEK.
MARINE...
A BRIEF PERIOD OF QUIET WEATHER WILL CONTINUE TONIGHT INTO WEDNESDAY
WITH SURFACE RIDGING IN PLACE. THIS WILL BE SHORT
LIVED...HOWEVER...AS A LOW PRESSURE LIFTS FROM THE GULF COAST
THROUGH THE OHIO RIVER VALLEY WEDNESDAY NIGHT AND THURSDAY.
CERTAINTY IN THIS LOW TRACK HAS INCREASED APPRECIABLY THE PAST 24
HOURS. ATTM...IT APPEARS WINDS WITH THIS SYSTEM WILL REMAIN LESS
THAN GALE FORCE. THE REASON FOR THE SUBDUED WINDS WILL BE THE
GLANCING BLOW OF THE LOW PRESSURE SYSTEM...AND A QUICK EASTWARD
TRANSLATION OF THE STRONGEST PRESSURE GRADIENT.
&&
.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LAKE HURON...NONE.
LAKE ST CLAIR...NONE.
MI WATERS OF LAKE ERIE...NONE.
&&
$$
AVIATION.....SC
SHORT TERM...CB
LONG TERM....BT
MARINE.......CB
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AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE).
