FXUS63 KDLH 021447 AAA
AFDDLH
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE DULUTH MN
847 AM CST WED DEC 2 2009
.UPDATE...NOT MANY CHANGES TO THE ONGOING FCST EXPECTED. WHILE
SOME BRIEF BREAKS IN CLOUD COVER DURING THE MORNING HOURS...VERY
COLD TEMPERATURES ALOFT AND A LOW LEVEL FRONTAL INVERSION WILL
RESULT IN CLOUDY SKIES ACROSS THE AREA. 925/850 COLD AIR
ADVECTION WILL CONTINUE TODAY...AND SO TEMPERATURES WILL GENERALLY
REMAIN WHERE THEY ARE FOR THE REST OF THE DAY.
LAKE EFFECT SNOW ADVISORY STILL LOOKS ON TRACK AND WILL BE
REVISITED IN DETAIL TODAY. 850 TEMPERATURES ARE DROPPING TO THE
-10 C RANGE...WHICH IS AMPLE FOR LATENT HEAT FLUX INTO THE
BOUNDARY LAYER...WINDS ARE BECOMING FAVORABLE. WHILE THE BOUNDARY
LAYER LOOKS TO REMAIN SATURATED...WE WILL NEED TO MONITOR THE
850/700 RH VALUES FOR DEEPER SATURATION. THE BEST
TRAJECTORY...WINDS BECOMING N/NE... AND SUFFICIENT DEEPER LAYER
SATURATION LOOKS TO SETUP AFTER 6 PM TONIGHT. /DONOFRIO
&&
.PREV DISCUSSION... /ISSUED 627 AM CST WED DEC 2 2009/
AVIATION...12/2 12Z TAFS
CYCLONIC FLOW AND LOW LEVEL MOISTURE WILL KEEP MVFR CEILINGS OVER
MOST OF THE AREA THROUGH THE TAF PERIOD. THERE MAY BE A FEW POCKETS
OF LOW VFR THROUGH THE PERIOD AS WELL. LIGHT SNOW WILL AFFECT MAINLY
WESTERN AREAS...SUCH AS KBRD/KPWC/KXVG LATER TODAY AND
TONIGHT...WITH VSBYS DROPPING TO 2SM AT TIMES. OTHER AREAS MAY SEE
SOME FLURRIES.
PREV DISCUSSION... /ISSUED 340 AM CST WED DEC 2 2009/
DISCUSSION...SFC LOW HAS MOVED INTO CTRL UP OF MICH EARLY THIS
MORNING. A SECONDARY SFC TROF STRETCHES FROM THE SFC LOW WNW TO SE
MANITOBA. THIS IS A REFLECTION OF THE DEEP MID LVL TROF/LOPRES
LOCATED OVER NODAK. WITH THE MID LVL FEATURE AMPLIFYING
TODAY AS IT MOVES INTO SODAK...WOULD EXPECT SFC REFLECTION TO BE
MAINTAINED AS IT SLIPS SOUTH ACROSS CWA. COND PRESS DEFICITS
SUGGEST THAT ENOUGH SATURATION MAY OCCUR AT LOWEST LAYERS TO BRING
OCCASIONAL LT SN/FLURRIES TO WRN EDGE OF CWA. CONFIDENCE ON CLOUD
COVERAGE OVER CTRL CWA IS LOW AS MIXED SIGNALS DEVELOP. WILL
MAINTAIN CONTINUITY AND COLLABORATION WITH SURROUNDING OFFICES FOR
NOW AND ASSUME WHATEVER BREAKS THAT OCCUR WILL BE SHORT LIVED WITH
STEEPENING LAPSE RATES PROMOTING INSTABILITY CLOUDS. OTHERWISE
MAIN STORY WILL BE LAKE EFFECT SNOW DEVELOPING OVER SOUTH SHORE.
PRIMARY AREA OF INTEREST WILL BE ALONG GOGEBIC RANGE WHERE
ELEVATED TERRAIN WILL ENHANCE ACCUMULATIONS. BUFKIT INSTABILITY
PARAMETERS...USING ABOUT 6C FOR LAKE TEMP...ARE MARGINAL UNTIL
AFTER 6Z THUR. HOWEVER ...FAVORABLE SFC/85H TRAJECTORY ALIGNS
TODAY AS 85H TEMPS REACH LOW ENOUGH LVLS TO PROMOTE UNSTABLE
LAPSE RATES. LIMITING FACTOR MAY BE MARGINAL MOISTURE WITHIN
CRITICAL 85/70H LAYER...FAVORABLE THRESHOLD OF 60 PERCENT IS
QUESTIONABLE DEPENDING ON MDL SELECTION. WINDS SHIFT MORE NWRLY
THUR AFTERNOON WHICH SHOULD TEMPER INFLUX OF LL MOISTURE. WITH
CORE OF UPPER TROF PASSING OVERHEAD THURSDAY...DEEP CYCLONIC
CURVATURE SHOULD MAINTAIN ENOUGH MOISTURE TO HAVE SMALL POPS FOR
SNOW SHOWERS. /CANNON
EXTENDED...THURSDAY NIGHT THROUGH TUESDAY
UPPER LOW WILL BE CENTERED JUST SOUTH OF HUDSON'S BAY...WITH
CYCLONIC FLOW AND PLENTY OF MOISTURE PRESENT THURSDAY NIGHT. THE LOW
STARTS TO MOVE SOUTH-SOUTHWEST ON FRIDAY...REACHING THE
INTERNATIONAL BORDER ON SATURDAY. THE ECMWF AND GFS DIFFER ON THE
LOCATION OF THE LOW BY THEN. HOWEVER...THEY BOTH SHOW A SURFACE
TROUGH EXTENDING NORTHEAST THROUGH SOUTHERN MINNESOTA OVER LAKE
SUPERIOR. THE EXACT ORIENTATION OF THIS TROUGH WILL HAVE A BIG
IMPACT ON THE WEATHER...ESPECIALLY FOR THE THE TWIN PORTS AREA. IF
THE GFS IS CORRECT...THE TWIN PORTS AND A PORTION OF THE SOUTH SHORE
COULD GET LAKE EFFECT SNOW DURING THE WEEKEND AS 850MB TEMPS ARE
FORECAST TO BE FROM -12C TO -14C.
WE DID NOT MAKE SIGNIFICANT CHANGES TO THE EXTENDED AT THIS TIME. WE
HAVE CHANCES FOR LIGHT SNOW THURSDAY NIGHT INTO FRIDAY NIGHT...WITH
MOST LOCATIONS NOT SEEING TOO MUCH ACCUMULATION. WE ALSO DID NOT ADD
POPS TO FAR WESTERN LAKE SUPERIOR FOR THE WEEKEND...DUE TO MODEL
DISAGREEMENT...BUT WE WILL WATCH CLOSELY. THE REST OF THE EXTENDED
WAS UNCHANGED AS WELL. /MELDE
TEMPERATURES WILL BE SEASONAL.
AVIATION...06Z TAF ISSUANCE
WIDESPREAD MVFR CIGS ARE EXPECTED DURING THE TAF PERIOD. THROUGH
THE EARLY MORNING HOURS...SOME LOCALIZED IFR/LIFR CIGS/VSYBS WILL
BE POSSIBLE DUE TO SOME SNOW...ESPECIALLY ACROSS NORTHERN TAF
SITES. CONDITIONS SHOULD GENERALLY BE DRY DURING THE DAY ON
WEDNESDAY...WITH MVFR CIGS BEING THE RULE. /MELDE
&&
.POINT TEMPS/POPS...
DLH 29 16 20 12 / 10 10 20 20
INL 26 12 16 12 / 10 10 20 40
BRD 31 18 23 12 / 20 20 20 20
HYR 32 17 22 14 / 20 30 20 20
ASX 33 19 22 18 / 30 40 40 20
&&
.DLH WATCHES/WARNINGS/ADVISORIES...
MN...NONE.
WI...LAKE EFFECT SNOW ADVISORY FROM 4 PM THIS AFTERNOON TO 4 PM CST
THURSDAY FOR WIZ003-004.
LS...SMALL CRAFT ADVISORY UNTIL NOON CST THURSDAY FOR LSZ121-146>148.
SMALL CRAFT ADVISORY UNTIL NOON CST TODAY FOR LSZ140>145.
&&
$$
