429
FXUS63 KMPX 271125
AFDMPX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
525 AM CST FRI NOV 27 2009
DISCUSSION
A FAIRLY TRANQUIL WEATHER PATTERN WILL BE IN PLACE THROUGH THE
WEEKEND BUT A FEW WEAK SHORTWAVES/FRONTS WILL CROSS THE AREA DURING
THAT TIME...BUT WILL ONLY BRING SMALL CHANCES FOR PRECIPITATION.
TEMPERATURES WILL BE A BIT OF A ROLLER COASTER THROUGH EARLY NEXT
WEEK BEFORE BECOMING NOTICEABLY COLDER BY THE END OF NEXT WEEK.
EARLY MORNING WATER VAPOR IMAGERY SHOWS AN AMPLIFIED PATTERN ACROSS
NORTH AMERICA WITH A LONGWAVE TROUGH MOVING ACROSS THE LOWER GREAT
LAKES WHILE BROAD RIDGING IS FOUND ACROSS THE CENTRAL U.S WITH
FAIRLY ZONAL FLOW TO IT/S NORTH OVER SOUTHERN CANADA. FURTHER
WEST...A NUMBER OF TROUGHS ARE EVIDENT MOVING TOWARDS THE WEST
COAST. AT THE SURFACE...LOW PRESSURE WAS SLOWLY MOVING EASTWARD
ACROSS LAKE HURON. HIGH PRESSURE RIDGING WAS SQUARELY OVER THE LOCAL
FORECAST AREA. A WEAK AREA OF LOW PRESSURE AND AN ATTENDANT COOL
FRONT WERE OVER SOUTHERN SASKATCHEWAN AND WILL AFFECT THE AREA LATER
ON TODAY AND TONIGHT.
TODAY THROUGH SUNDAY...SEVERAL WEAK SYSTEMS WILL CROSS THE AREA OVER
THE NEXT SEVERAL DAYS. A CLOSER LOOK AT WATER VAPOR IMAGERY SHOWS A
WEAK SHORTWAVE MOVING EASTWARD ACROSS EASTERN ALBERTA INTO
SASKATCHEWAN WHICH CORRESPONDS WITH AREA OF INCREASED HEIGHT FALLS
ON UA ANALYSIS. WITH SFC RIDGING DEPARTING THE AREA THE LOW OVER
SASKATCHEWAN WILL MOVE ACROSS THE DAKOTAS TODAY. THIS WILL BRING
SOUTHERLY SFC FLOW AND WARM ADVECTION TO THE AREA. SOUTH WINDS WON/T
BE VERY STRONG BUT THE LOW LEVELS BETWEEN 925 AND 850 MB WILL WARM
SOME 10 DEGREES FROM CURRENT VALUES. MIXING TO 950 OR 925 MB LOOKS
REASONABLE FOR TODAY SO HIGHS ARE EXPECTED TO RANGE FROM AROUND 40
NORTHEAST TO THE LOWER 50S FAR SOUTHWEST WHERE MODEST LOCAL
DOWNSLOPE WARMING WILL OCCUR. THE COOL FRONT WILL TAKE ITS TIME
CROSSING THE AREA TONIGHT AND SATURDAY MORNING WITH LITTLE MORE THAN
A WIND SHIFT. NORTHWEST WINDS WILL FILL IN BEHIND IT BUT THE COLD
ADVECTION WILL NOT BE OVERLY STRONG. A SECOND AND MORE ORGANIZED
UPPER TROUGH WHICH IS CURRENTLY OVER CENTRAL BRITISH COLUMBIA WILL
PUSH SOUTHEASTWARD THROUGH THE DAY SATURDAY AND REACH THE FORECAST
AREA SATURDAY EVENING. THIS TROUGH WILL ENCOUNTER A FEED OF MOISTURE
BEING SENT NORTHWARD FROM A TROUGH WORKING ONTO THE WEST COAST TODAY
AND TONIGHT. THE MOISTURE WILL NOT BE ALL THAT ABUNDANT BUT THERE
WILL BE ENOUGH FORCING TO WARRANT A MENTION OF SCATTERED
FLURRIES SATURDAY NIGHT AND IN THE EAST ON SUNDAY MORNING. SOME
FLURRIES MAY LINGER NORTH AND EAST FOR THE REMAINDER OF SUNDAY.
SHARP COLD ADVECTION WILL COMMENCE WITH THE PASSAGE OF THE TROUGH SO
EXPECT TEMPS TO BE HELD IN THE 30S WITH BREEZY NORTHWEST WINDS.
MONDAY THROUGH TUESDAY NIGHT...A SHIFT IN THE FLOW PATTERN OVER
NORTH AMERICA WILL BE UNDERWAY BY THE END OF THE WEEKEND. THE
TROUGH THAT MOVES ACROSS THE LOCAL AREA WILL EVOLVE INTO A
LONGWAVE TROUGH OVER THE EASTERN U.S. MONDAY. THE AFOREMENTIONED
TROUGH MOVING ONTO THE WEST COAST WILL CLOSE OFF AND SETTLE
SOUTHWARD ACROSS THE DESERT SOUTHWEST SUNDAY AND MONDAY WHILE
RIDGING BUILDS ALONG THE WEST COAST. THE FLOW OVER THE WESTERN RIDGE
WILL BECOME ACTIVE ACROSS WESTERN CANADA WITH A SERIES OF SHORTWAVES
TRAVERSING THE NORTHERLY FLOW DOWN ITS EASTERN FLANK...WHICH WILL
TAKE THEM OVER THE FORECAST AREA. THE FIRST WAVE LOOKS TO CROSS THE
AREA MONDAY. AGAIN THE DRY ATMOSPHERE WILL REMAIN IN PLACE SO
PRECIPITATION IS UNLIKELY. BRIEF LOW AMPLITUDE RIDGING SHOULD MOVE
IN BEHIND THE TROUGH PASSAGE INTO TUESDAY WITH WARM ADVECTION AND
SOUTHWESTERLY SFC FLOW BRINGING A SHORT LIVED RETURN TO MILDER AIR.
A MORE SIGNIFICANT TROUGH WILL MOVE ACROSS LATER TUESDAY AND INTO
WEDNESDAY BRINGING MUCH COLDER AIR BY WEDNESDAY NIGHT AND THROUGH
THE REST OF THE WEEK. ..MDB..
AVIATION
/12Z TAF ISSUANCE/
VFR FLYING CONDS WILL PREVAIL THROUGH THE BULK OF THE PERIOD.
SOUTHEAST WINDS INCREASING TO AROUND 10 KNOTS...THEN DIMINISHING
THIS EVENING. CLOUD AND CEILING HEIGHTS GENLY AT OR ABOVE 10
THOUSAND FEET AGL.
MPX WATCHES/WARNINGS/ADVISORIES
MN...NONE.
WI...NONE.
MDB/JM
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