Area Forecast Discussion
Issued by NWS Duluth, MN

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000
FXUS63 KDLH 190554
AFDDLH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DULUTH MN
1254 AM CDT TUE AUG 19 2014

.UPDATE...
ISSUED AT 1252 AM CDT TUE AUG 19 2014

UPDATED FOR NEW AVIATION FORECAST DISCUSSION.

UPDATE ISSUED AT 1024 PM CDT MON AUG 18 2014

A FEW SHOWERS NEAR GPZ AND HIB TO NEAR DLH. OTHERWISE...BULK OF
THE RAIN HAS MOVED INTO NW WI. LIGHTNING LIMITED TO SOUTHERN TIER
OF WI ZONES. HAVE MADE ADJUSTMENTS TO ACCOUNT FOR THESE TRENDS AND
ADD MORE FOG.

UPDATE ISSUED AT 834 PM CDT MON AUG 18 2014

THE THUNDER THREAT HAS MOVED INTO NW WI FOR THE NIGHT AND HAVE
REMOVED THE THUNDER MENTION FROM NE MN. REST OF THE FORECAST STILL
ON TRACK.

&&

.SHORT TERM...(THIS EVENING THROUGH TUESDAY AFTERNOON)
ISSUED AT 248 PM CDT MON AUG 18 2014

MAIN CONCERNS IN THE SHORT TERM REMAIN FOCUSED AROUND THE POTENTIAL
FOR SHOWERS AND THUNDERSTORMS LATE THIS AFTERNOON INTO THE EARLY
OVERNIGHT HOURS...ALONG WITH THE CHANCE OF STORMS AGAIN TUE
AFTERNOON. WILL ALSO HIGHLIGHT THE LIKELIHOOD OF ANOTHER ROUND OF
FOG LATE TONIGHT AND TUE MORNING...AND COOLER TEMPERATURES AROUND
THE PERIPHERY OF LAKE SUPERIOR DUE TO A PERSISTENT EAST WIND.

LARGE SCALE LIFT IS BEING GENERATED BY AN INCOMING UPPER LEVEL S/W
DROPPING IN FROM THE NW THIS AFTERNOON...CO-LOCATED WITH AN EWD
PROGRESSING SFC COLD FRONT CURRENTLY POSITIONED N-S OVER WRN MN.
AS THE TROUGH AND SFC FRONT SWEEP TO THE EAST...SHOWERS AND
THUNDERSTORMS WILL DEVELOP AND SPREAD THROUGH THE NORTHLAND THIS
EVENING AND TONIGHT. LATEST SATELLITE IMAGERY CONTINUES TO
INDICATE THE CLOUD COVER ATTEMPTING TO MIX OUT OVER E AND N-CENTRAL
MN. IF THIS CLEARING CONTINUES PRIOR TO FROPA...THE BL WILL LIKELY
BECOME UNSTABLE ENOUGH TO GENERATE SCATTERED T-STORMS...WITH A FEW
STORMS POSSIBLY PRODUCING HAIL AND STRONG WINDS FROM AROUND PINE
RIVER TO HINCKLEY TO PHILLIPS. INSTABILITY PARAMETERS ARE BECOMING
ELEVATED AROUND THE SRN AND SWRN PERIPHERY OF THE FORECAST AREA
WITH ML CAPE VALUES AROUND 1000 J/KG. DEEP LAYER SHEAR IS
MINIMAL...BUT LOW LEVEL LAPSE RATES WILL BE STEEP ENOUGH TO
SUPPORT PULSE TYPE STORMS THROUGH THE LATE EVENING. THE STORMS
WILL LIKELY BE RELATIVELY SLOW MOVING AS WELL...WHICH COULD ALLOW
THE STORMS TO DROP HEAVY AMTS OF RAINFALL OVER A PERIOD OF TIME. A
GOOD PORTION OF THE NORTHLAND SAW SATURATING RAINS LAST
NIGHT...AND ANY ADDITIONAL HEAVY RAIN COULD FURTHER ENHANCE THE
POTENTIAL FOR LOCALIZED FLOODING. MOST OF THE AIR MASS AROUND LAKE
SUPERIOR WILL BE COOLER AND MORE STABLE...AND NOT SUPPORTIVE OF
ORGANIZED CONVECTIVE DEVELOPMENT. HOWEVER...STILL CANNOT RULE OUT
SCT SHOWERS AND ISO STORMS ANYWHERE IN THE NORTHLAND THROUGH THE
EARLY OVERNIGHT HOURS.

AS THE BOUNDARY LAYER COLLAPSES TONIGHT AND AN ELEVATED INVERSION
SETS UP AGAIN...THE COMBINATION OF COOL OVERNIGHT TEMPS AND A MOIST
NEAR-SFC LAYER AND CALM WINDS WILL PRODUCED AREAS OF FOG ONCE
AGAIN. VSBYS WILL BE REDUCED TO A HALF MILE OR LESS AT TIMES
THROUGH THE REGION. CONDITIONS SHOULD IMPROVE BY MID MORNING AS
THE DEEP LAYER MIXING BEGINS.

A SFC LOW ASSOCIATED WITH THE FRONT WILL TAKE A FAVORABLE PATH
THAT WILL KEEP THE DOMINANT WIND FLOW FROM THE EAST OFF LAKE
SUPERIOR AND ALLOW THE COOL WIND REGIME TO PERSIST THROUGH AT
LEAST TUE. THE WIND OFF THE LAKE SHOULD BE WEAK ON TUE... BUT
ENOUGH TO KEEP TEMPS 5-10 DEG COOLER THAN INLAND LOCATIONS. LOOK
FOR HIGHS AROUND THE LAKE IN THE LOWER TO MID 60S...AND INLAND
INTO THE LOWER TO MID 70S.

THE COOL NLY FLOW ALOFT ON THE BACK SIDE OF THE DEPARTING LOW
PRESSURE SYSTEM WILL ALLOW LAPSE RATES TO STEEPEN ENOUGH TO
TRIGGER ADDITIONAL CONVECTIVE SHOWERS AND STORMS TUE AFTERNOON.
SHOWERS COULD BECOME QUITE WIDESPREAD...HOWEVER LIMITED
INSTABILITY WILL ALLOW STORMS TO BE GENERALLY ISOLATED.

.LONG TERM...(TUESDAY NIGHT THROUGH MONDAY)
ISSUED AT 248 PM CDT MON AUG 18 2014

IT LOOKS LIKE AN ACTIVE PERIOD WITH CHANCES OF SHOWERS AND STORMS
THROUGH MUCH OF THE FORECAST. WHILE THE MIDDLE OF THE WEEK LOOKS
RELATIVELY QUIET...THE LATTER HALF OF THE WEEK COULD FEATURE A
COUPLE SIGNIFICANT SYSTEMS THAT COULD AMOUNT TO MODERATE TO HEAVY
RAINFALL FOR PARTS OF THE NORTHLAND.

AS OF TUESDAY EVENING...THERE WILL BE AN UPPER LEVEL LOW OVER THE
LAKE SUPERIOR AND LAKE MICHIGAN AREA. AN UPPER LEVEL RIDGE WILL BE
OVER THE PLAINS.

THERE COULD BE LINGERING SHOWERS TUESDAY EVENING...MAINLY OVER THE
EASTERN FORECAST AREA...AS THE UPPER LEVEL LOW OVER THE GREAT LAKES
GRADUALLY SHIFTS EAST AND SURFACE HIGH PRESSURE MOVES INTO THE
NORTHLAND.

THE UPPER LEVEL RIDGE WILL MOVE OVER THE NORTHLAND WEDNESDAY. INLAND
AREAS WILL BE WARMER THAN TUESDAY...BUT THE EASTERLY WINDS OFF LAKE
SUPERIOR WILL KEEP AREAS CLOSE TO THE LAKE SOMEWHAT COOL.

THE MODELS ARE COMING INTO BETTER AGREEMENT THAT A SURFACE TROUGH
AND WARM FRONT WILL LIFT INTO THE UPPER MIDWEST DURING THE WEDNESDAY
NIGHT AND THURSDAY TIMEFRAME AND BRING SIGNIFICANT RAINFALL TO PARTS
OF THE NORTHLAND DURING THAT TIME. INCREASED PCPN CHANCES BECAUSE OF
THIS. THE SURFACE FRONT COULD STALL OVER THE SOUTHERN FORECAST AREA
THURSDAY AS EASTERLY INCREASE OVER LAKE SUPERIOR AND KEEP AREAS NEAR
LAKE SUPERIOR AND THE NORTHERN FORECAST AREA SIGNIFICANTLY COOLER
THAN THAN THE SOUTHERN FORECAST AREA.

THE MODELS DO NO AGREE ON TIMING BUT GENERALLY INDICATE THAT A
POTENT SHORTWAVE IN THE PLAINS WILL LIFT INTO CANADA DURING THE
FRIDAY OR SATURDAY TIMEFRAME AND RESULT IN A STRONG LOW PRESSURE
SYSTEM MOVING THROUGH THE NORTHERN PLAINS OR UPPER MIDWEST DURING
THAT TIME. THIS SYSTEM COULD BRING HEAVY RAIN TO THE FORECAST AREA.
THE WESTERN AND NORTHERN FORECAST AREA APPEAR TO BE MORE AT RISK OF
THIS HEAVY RAIN THAN THE SE FORECAST AREA. THE GFS IS MUCH FASTER
THAN THE ECMWF AND GEM...BUT DUE TO THE GENERAL AGREEMENT ON THE
PLACEMENT OF THIS SYSTEM...WE WILL NEED TO KEEP AN EYE ON THIS
SYSTEM FOR THE POTENTIAL OF HEAVY RAIN AFFECTING THE NORTHLAND.

COOLER AIR WILL LIKELY BEGIN TO MOVE INTO THE NORTHLAND LATE THIS
WEEKEND IN THE WAKE OF THE PASSING LOW PRESSURE SYSTEM. THERE ARE
CHANCES OF SHOWERS AND STORMS SUNDAY INTO EARLY NEXT WEEK.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z TUESDAY NIGHT)
ISSUED AT 1252 AM CDT TUE AUG 19 2014

AS AN UPPER LOW MOVES OVER THE TERMINALS THROUGH 12Z...AREAS OF
FOG ARE EXPECTED WITH IFR/LIFR CIGS/VSBYS. BY 15Z...AN IMPROVEMENT
TO VFR IS FORECAST. VCSH ARE POSSIBLE AGAIN BY MID DAY. SOME
CLEARING WILL COMMENCE BY LATE AFTERNOON...BUT SOME PATCHY BR MAY
OCCUR AFTER 00Z.

&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  56  71  58  70 /  10  10  30  60
INL  55  78  58  74 /  10  10  20  60
BRD  58  80  63  80 /  10  10  60  60
HYR  55  77  61  81 /  20   0  20  60
ASX  55  71  57  76 /  20  10  20  60

&&

.DLH WATCHES/WARNINGS/ADVISORIES...
MN...DENSE FOG ADVISORY UNTIL 8 AM CDT THIS MORNING FOR MNZ025-
     033>038.

WI...DENSE FOG ADVISORY UNTIL 8 AM CDT THIS MORNING FOR WIZ001-006-
     007.

LS...NONE.
&&

$$

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





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