Area Forecast Discussion
Issued by NWS Duluth, MN

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000
FXUS63 KDLH 192324
AFDDLH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DULUTH MN
624 PM CDT TUE AUG 19 2014

.UPDATE...
ISSUED AT 502 PM CDT TUE AUG 19 2014

BEST INSTABILITY HAS MOVED AWAY FROM THE FA. GRANTED...THERE IS
STILL SOME MUCAPE AROUND...ABOUT 500J/KG...NOT EXPECTING THUNDER
FOR THE REST OF THE NIGHT HOWEVER AND HAVE REMOVED. SHOWERS STILL
DOT THE LANDSCAPE AND WILL GRADUALLY DIMINISH THROUGH THE EVENING.
REST OF THE FORECAST ON TRACK.

&&

.SHORT TERM...(THIS EVENING THROUGH WEDNESDAY AFTERNOON)
ISSUED AT 310 PM CDT TUE AUG 19 2014

SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS LATE THIS AFTERNOON AND
EVENING ARE THE MAIN FOCUS OF ATTENTION IN THE SHORT TERM...WITH
AREAS OF FOG RE-DEVELOPING LATE IN THE EVENING AND PERSISTING
THROUGH THE OVERNIGHT HOURS. QUIET WEATHER CONDITIONS ARE EXPECTED
THROUGH THE DAY TOMORROW.

CUTOFF UPPER LOW CONTINUES TO ROTATE EWD INTO THE CENTRAL GREAT
LAKES THIS AFTERNOON...ALONG WITH AN ASSOCIATED SFC LOW...FAIRLY
EXTENSIVE CLOUD COVER AND SCATTERED RAIN SHOWERS. HAVE YET TO SEE
ANY THUNDER FROM THE CONVECTION AS OF 300 PM...BUT STARTING TO SEE
THE CLOUD COVER ACROSS THE SRN AND SWRN COUNTIES BECOME MORE
CELLULAR IN NATURE...WHICH WILL ALLOW THE BL TO WARM AND AID IN
THE DE-STABILIZATION AND POTENTIAL DEVELOPMENT OF WEAK T-STORMS
BEFORE THE SUN GOES DOWN. ML CAPE VALUES INTO CENTRAL MN AND
W-CNTRL WI HAVE RISEN TO AROUND 500-700 J/KG AND WILL COMBINE WITH
WEAK LOW LEVEL LAPSE RATES AND FAIRLY DEEP LAYER MOISTURE TO
PRODUCE SCT RAIN SHOWERS...AND A FEW WEAK ISOLATED STORMS INTO THE
EVENING. BRIEF HEAVY RAIN AND VERY SMALL HAIL ARE THE MAIN
THREATS. STRATO-CU FIELD WILL BEGIN TO MIX OUT FROM NW-SE LATER
THIS EVENING AND INTO THE OVERNIGHT AS HIGH PRESSURE BUILDS IN.
THE CYCLONIC FLOW AROUND THE LOW TO THE EAST WILL HOWEVER KEEP AN
ABUNDANT AMOUNT OF CLOUDS OVER THE ERN HALF OF THE FORECAST AREA
THROUGH MUCH OF THE NIGHT.

THE CLOUD COVER WILL CAUSE TEMPERATURE FORECAST TONIGHT TO BE
QUITE A CHALLENGE WITH TEMPS REMAINING ELEVATED IN THE MID TO
UPPER 50S THROUGH THE ARROWHEAD AND INTO NRN WI DUE TO THE CLOUD
COVER...AND DROPPING INTO LOWER 50S OVER THE WRN COUNTIES WHERE
SKIES CLEAR OUT. AS THE TEMPERATURES FALL AFTER
MIDNIGHT...CONDITIONS WILL BECOME FAVORABLE FOR FOG ONCE AGAIN.
RESIDUAL SFC MOISTURE...CALM WINDS AND ENOUGH OF AN INVERSION WILL
ALLOW FOG TO FORM AND PERSIST INTO WED MORNING. VSBYS WILL BE
REDUCED TO A HALF MILE OR LESS AT TIMES.

UPPER RIDGE BUILDS IN THROUGH THE DAY WED AND FINALLY BRINGS IN A
BRIEF PERIOD OF DRY WEATHER. A WEAK WAA REGIME WILL DEVELOP OVER
CENTRAL MN AND USHER IN A WARM AIR MASS FROM THE SOUTH.
TEMPERATURES WILL RISE INTO THE MID TO UPPER 70S OVER MUCH OF THE
NORTHLAND. A VERY LIGHT E/NE WIND OFF LAKE SUPERIOR WILL KEEP
TEMPS ONLY A FEW DEG COOLER INTO THE LOWER 70S.

.LONG TERM...(WEDNESDAY NIGHT THROUGH TUESDAY)
ISSUED AT 310 PM CDT TUE AUG 19 2014

THE NORTHLAND WILL BE IN ACTIVE WEATHER PATTERN FOR THE FORECAST
PERIOD WITH THE POTENTIAL FOR MULTIPLE SYSTEMS TO BRING SIGNIFICANT
RAINFALL TO PARTS OF THE FORECAST AREA.

AS OF WEDNESDAY EVENING...THERE WILL BE AN UPPER LEVEL RIDGE
CENTERED OVER THE SOUTHERN MISSISSIPPI REGION...WITH THE RIDGE AXIS
EXTENDING NORTHWARD TO THE NORTHLAND. THERE WILL BE A SURFACE LOW IN
CENTRAL SOUTH DAKOTA. ITS NW TO SE ORIENTATED WARM FRONT WILL CUT
ACROSS WESTERN AND SOUTHERN MINNESOTA...AND SW WISCONSIN.

THE MODELS ARE NOT IN GOOD AGREEMENT...PRIMARILY ON HOW FAR NORTH
THE WARM FRONT WILL LIFT AND HOW FAR EAST THE SURFACE LOW WILL MOVE.
THIS HAS IMPLICATIONS ON FAR NORTH MODERATE TO HEAVY RAIN WILL LIFT
INTO THE NORTHLAND. THE GFS IS THE DRIER MODEL FOR THE
NORTHLAND...KEEPING THE SURFACE LOW IN SOUTH DAKOTA AND SUGGESTING
THE COOL AND DRIER EASTERLY FLOW OFF LAKE SUPERIOR WILL HELP KEEP
THE PCPN AT BAY. THE ECMWF AND GEM CONTINUE TO BE MUCH MORE ROBUST
WITH PCPN FOR THE NORTHLAND COMPARED TO THE GFS SINCE THEY LIFT THE
WARM FRONT MUCH FARTHER NORTH AND DO NOT SUGGEST THE COOLER EASTERLY
FLOW WILL HAVE A SIGNIFICANT IMPACT ON THE RAINFALL. I LEANED ON THE
ECMWF/GEM/SREF MODELS SINCE THERE IS BETTER AGREEMENT BETWEEN THE 3
COMPARED TO THE GFS.

THERE ARE THEN MAJOR MODEL DIFFERENCES FOR LATE THIS WEEK. THE GFS
FINALLY LIFT THE SOUTH DAKOTA LOW INTO NORTHERN MINNESOTA FRIDAY
NIGHT AND EARLY SATURDAY WITH ITS WARM FRONT LIFTING THROUGH THE
NORTHLAND. THIS COULD BRING A SURGE OF MOISTURE AND MODERATE TO
HEAVY RAIN. ON THE OTHER HAND...THE ECMWF AND GEM ARE PRIMARILY DRY
FOR FRIDAY AND SATURDAY.

THE MAJOR MODEL DIFFERENCES CONTINUE INTO EARLY NEXT WEEK. THE
MODELS DO SUGGEST THERE WILL BE A DEEPENING UPPER LEVEL LOW OVER
SOUTH CENTRAL CANADA OR THE NORTHERN PLAINS. A STRONG LOW PRESSURE
SYSTEM COULD FORM SOMEWHERE IN THE PLAINS OR SOUTH CENTRAL CANADA
AND BRING SIGNIFICANT RAINFALL TO PARTS OF THE NORTHLAND DURING THIS
TIME. COOLER AIR COULD MOVE INTO THE NORTHLAND DURING THE MIDDLE OF
NEXT WEEK IN THE WAKE OF THAT SYSTEM AND ITS COLD FRONT.

BEYOND THE THURSDAY AND THURSDAY NIGHT TIMEFRAME...I PRIMARILY
LEANED ON A WIDE MODEL BLEND DUE TO THE MAJOR MODEL DIFFERENCES.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z WEDNESDAY EVENING)
ISSUED AT 624 PM CDT TUE AUG 19 2014

SHOWER THREAT HAS DIMINISHED AND HAVE REMOVED FROM THE TAFS.
OTHERWISE...MVFR TO VFR CIGS. THERE ARE STILL INDICATIONS OF BR
FORMATION AGAIN TONIGHT WITH LIFR/VLIFR CIGS. VSBYS MAT STAY IN
THE IFR RANGE. A QUICK IMPROVEMENT TO VFR IS EXPECTED AFTER 13Z.

&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  58  72  58  70 /  20  10  20  60
INL  53  77  58  75 /  10  10  20  60
BRD  55  79  64  79 /  10  10  70  70
HYR  55  75  61  82 /  30  10  30  60
ASX  59  73  56  78 /  30  10  10  60

&&

.DLH WATCHES/WARNINGS/ADVISORIES...
MN...NONE.
WI...NONE.
LS...NONE.
&&

$$

UPDATE...GSF
SHORT TERM...BJT
LONG TERM...GROCHOCINSKI
AVIATION...GSF





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