FXUS63 KDLH 142102
AFDDLH
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DULUTH MN
302 PM CST MON DEC 14 2009
.DISCUSSION...
ANOTHER UPPER TROUGH...ASSOCIATED WITH A WAVY NORTHWEST FLOW...
WILL DROP THROUGH OUR AREA TUESDAY. CLOUDS ARE DISSIPATING FROM
WEST TO EAST...WITH AN ERODING BACK-EDGE MOVING THROUGH WESTERN MN
AT THIS TIME. A RADIATING ARCTIC AIR MASS SUGGESTS LOW TEMPERATURS
MORE IN LINE WITH THE MUCH COLDER MET FORECASTS. THE CORE OF THE
COLD AIR ALOFT PASSES...BUT SURFACE RIDGING AND THE LEADING EDGE
OF MID/HIGH CLOUDS WILL LIKELY NOT REACH OUR AREA BEFORE WEDNESDAY
MORNING. TEMPERATURES WILL BE MOSTLY OR COMPLETELY SUBZERO ACROSS
OUR AREA UNTIL THEN. AS THE SASKATCHEWAN SURFACE HIGH SLIPS TO OUR
SOUTH...RIDGING NORTH OF LAKE SUPERIOR SHOULD QUICKLY DIMINISH AND
WINDS WILL BACK...DRIVING LAKE CONVECTION MORE AND MORE OFFSHORE
TONIGHT AND KEEPING IT OFFSHORE TUESDAY AND TUESDAY NIGHT. GRADUAL
WARMING WILL FOLLOW...BUT WEAK SHORT WAVES WILL NOT RESULT IN MUCH
OR ANY PRECIPITATION THROUGH THURSDAY.
.EXTENDED...THURSDAY NIGHT THROUGH MONDAY...
WAA REGIME AND A FAST MOVING UPPER DISTURBANCE WILL HAVE SHIFTED OFF
TO THE EAST AT THE START OF THE PERIOD. UPPER LEVEL FLOW WILL THEN
VEER AND BECOME NW AND THEN N THROUGH THE REMAINDER OF THE EXTENDED.
THIS IS DUE TO THE FACT THAT A DEEP UPPER LEVEL LOW WILL GET BLOCKED
ALONG THE EASTERN US AND THEN...TO SIGNIFICANT DIFFERING DEGREES
BASED ON YOUR MODEL OF CHOICE...RETROGARDE BACK TO THE WEST THROUGH
SE CANADA. THE GFS AND GEM RETROGRADE THE UPPER LOW AND KEEP
SURFACE HIGH PRESSURE TUCKED OFF TO OUR WEST...WHILE THE ECMWF KEEPS
THE LOW MUCH FURTHER EAST AND KEEP WEAK HIGH PRESSURE OVER THE AREA.
THIS MAKES THE GFS/GEM A BIT WETTER THAN THE EURO...ESPECIALLY ON
THE SOUTH SHORE.
WHAT THIS ALL MEANS IS...WITH UPPER FLOW NORTHERLY...DISTURBANCES
MOVING AROUND THE BACK SIDE OF THE LOW...AND CAA IN PLACE...OFF AND
ON CHANCES OF LIGHT SNOW SHOWERS/FLURRIES WILL PERSIST AND WILL
DEPEND ON HOW MUCH THE LOW RETROGRADES. SURFACE-850 WINDS WILL
INVOLVE SOME FORM OF A NORTHERY COMPONENT WHICH WILL KEEP THE FEED
OF COOL AIR OUT OF SOUTHERN CANADA...AND ALSO KEEP THE CHANCE OF
LAKE EFFECT SNOW SHOWERS ALONG THE SOUTH SHORE...THOUGH THE QUESTION
MARK WILL BE MOISTURE. THEREFORE...LITTLE CONFIDENCE TO DEVIATE
FROM ONGOING FCST TOO MUCH AT THIS TIME.
.AVIATION...18Z TAF ISSUANCE...KHYR WILL SEE LINGERING MVFR
CONDITIONS IN -SN THROUGH AT LEAST 0Z. THERE WILL BE A WINDOW OF MVFR
AT KBRD WITH LIGHT SNOW SHOWERS PUSHING THROUGH CENTRAL MINNESOTA
THIS AFTERNOON AHEAD OF A WEAK MID LEVEL DISTURBANCE. THESE MAY ALSO
IMPACT KDLH LATER THIS AFTERNOON...BUT LOW CONFIDENCE ON THAT
OCCURRING...AND IT WILL BE BRIEF AT BEST. THE MAIN UPPER LEVEL WAVE
WILL THEN MOVE THROUGH OVERNIGHT...WITH LITTLE MORE THAN LOW VFR
CLOUD. OTHERWISE...VFR CONDITIONS WILL PREVAIL THROUGH TAF PERIOD
WITH MID LVL CLOUDS AROUND 6-8 KFT BEFORE CLEARING NEAR THE END OF
THE PERIOD.
&&
.POINT TEMPS/POPS...
DLH -7 2 -11 6 / 10 10 10 10
INL -21 -9 -21 3 / 10 10 10 20
BRD -14 -1 -13 9 / 10 10 10 10
HYR -8 4 -12 8 / 10 10 10 10
ASX -4 4 -12 10 / 50 10 10 10
&&
.DLH WATCHES/WARNINGS/ADVISORIES...
MN...WIND CHILL ADVISORY FROM 6 PM THIS EVENING TO 11 AM CST TUESDAY
FOR MNZ010>012-018>021-025-026-033>038.
WI...WIND CHILL ADVISORY FROM 6 PM THIS EVENING TO 11 AM CST TUESDAY
FOR WIZ001.
LS...SMALL CRAFT ADVISORY FROM 4 AM TO 10 PM CST TUESDAY FOR LSZ121-
146>148.
&&
$$
EOM/DONOFRIO
