Area Forecast Discussion
Issued by NWS Duluth, MN

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000
FXUS63 KDLH 020838
AFDDLH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DULUTH MN
338 AM CDT TUE SEP 2 2014

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 330 AM CDT TUE SEP 2 2014

LATEST SHORT RANGE GUIDANCE CONTINUES TO SHOW AN UNSTABLE ZONAL FLOW
WITH EMBEDDED VORTS...OVER THE REGION TODAY. SOUNDINGS INDICATE
STEEP LAPSE RATES AS A RESULT OF THE COOL AIR ALOFT...AND AROUND
1000 J/KG OF SB CAPE TO TAP INTO THIS AFTERNOON. ALTHOUGH A STRAY
SHOWER/TSTM COULD BE TRIGGERED ANYWHERE IN THE CWA THIS
AFTERNOON...THERE IS MODEL CONSENSUS THAT THE BEST CHC FOR A FEW
STORMS WILL BE OVER NORTH-CENTRAL MN THIS AFTERNOON...TRACKING
EAST ACROSS THE NRN ZONES THROUGH THE EVENING. HAVE KEPT SMALL
POPS ACROSS THE NORTH THROUGH THE OVERNIGHT HOURS AS LATEST BUFR
SOUNDINGS SHOW SOME ELEVATED CAPE LINGERS IN THIS REGION AS A
TRANSITION TO WARM AIR ADVECTION PUSHES OVER MN. A RETURN FLOW AND
WARMING H85 TEMPS WILL PREVAIL WEDNESDAY AS THE NORTHLAND BECOMES
SITUATED INT HE WARM SECTOR AHEAD OF A DEVELOPING LOW PUSHING INTO
THE WESTERN DAKOTAS. THE INCREASING MOISTURE AND INSTABILITY WILL
BRING INCREASING CHANCES FOR THUNDER ACROSS THE FORECAST AREA
THROUGH THE DAY. A FEW OF THESE STORMS WILL HAVE THE POTENTIAL TO
BECOME SEVERE.

.LONG TERM...(WEDNESDAY THROUGH MONDAY)
ISSUED AT 330 AM CDT TUE SEP 2 2014

THREE PRIMARY FEATURES OF INTEREST IN THE DAY 2 THROUGH 7 TIME
FRAME: 1) THE CHANCE FOR MAINLY LIGHT SNOW ACROSS THE SOUTHEAST HALF
TO TWO THIRDS OF THE CWA THURSDAY/THURSDAY NIGHT.. 2) ANOTHER SHOT
OF VERY COLD ARCTIC AIR FROM SATURDAY-MONDAY AND 3) ASSOCIATED
CHANCES FOR SIGNIFICANT LAKE EFFECT SNOW ALONG THE SOUTH SHORE.

VERY WEAK IMPULSE WILL SLIDE RAPIDLY EASTWARD ALONG THE CANADIAN
BORDER REGION WED NIGHT..PERHAPS BRINGING SOME LIGHT SNOW TO THE
BORDERLAND AND ARROWHEAD.  THE MAIN EFFECT OF THIS FEATURE WILL BE
TO ALLOW THE RETURN OF SHALLOW COLD ARCTIC AIR ACROSS MOST OF THE
REGION..RESULTING IN THE STRENGTHENING OF A LOW LEVEL BAROCLINIC
ZONE JUST TO OUR SOUTH.  THERE IS STILL SOME UNCERTAINTY REGARDING
CHANCES FOR WIDESPREAD LIGHT SNOW LATER THUR/THUR NIGHT..BUT BEST
CHANCES APPEAR TO BE SOUTH/EAST OF THE I35/HIGHWAY 61 CORRIDORS. WE
HAVE RAISED POPS SOME FROM THE PREVIOUS FORECAST ACROSS NW
WISCONSIN..ESP IN CLOSER PROXIMITY TO LK SUPERIOR WHERE COLD NE
WINDS SHOULD ALLOW SOME ENHANCEMENT.  HOWEVER..DUE TO THE CONTINUED
MODEL SPREAD IN PLACEMENT..WE HAVE KEPT AMOUNTS FAIRLY LOW AT THIS
TIME..GENERALLY IN THE 1-3 INCH RANGE.

ANOTHER WEAK DISTURBANCE WILL SLIDE EASTWARD ACROSS ONTARIO ON
SATURDAY..BRINGING ANOTHER CHANCE OF LIGHT SNOW MAINLY ACROSS THE
NORTH. FOLLOWING THIS WAVE..ANOTHER MUCH STRONGER SHOT OF ARCTIC AIR
WILL SURGE SOUTHWARD INTO THE WESTERN GREAT LAKES REGION AND TAKE UP
RESIDENCE FOR THE COMING WEEKEND INTO EARLY NEXT WEEK.  THE STRENGTH
OF THIS AIRMASS LOOKS TO BE ON PAR WITH THE ONE THAT JUST RECENTLY
DEPARTED..SO MUCH OF THE REGION WILL HEAD INTO THE DEEP FREEZE ONCE
AGAIN.

PROVIDED THAT MEDIUM RANGE MODEL GUIDANCE HAS A DECENT HANDLE ON
THINGS DURING THIS TIME FRAME..ONE PRIMARY DIFFERENCE WITH THIS NEXT
ARCTIC SURGE WILL BE A MUCH MORE NORTHERLY LOW LEVEL WIND
COMPONENT.  THE SOUTH SHORE WAS LARGELY SPARED HEAVY LK EFFECT SNOWS
WITH THE LAST ARCTIC OUTBREAK DUE TO MAINLY WESTERLY WINDS..BUT IT
APPEARS THAT THIS WILL NOT BE THE CASE THIS NEXT TIME AROUND.  WE
HAVE ADJUSTED POPS UPWARD FROM SAT NIGHT-MONDAY TIME FRAME IN
ANTICIPATION OF A MUCH BETTER COVERAGE OF LK EFFECT SNOWS.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z TUESDAY NIGHT)
ISSUED AT 1235 AM CDT TUE SEP 2 2014

MAIN CONCERN OVERNIGHT IS FOR FOG...WITH LOW DEWPOINT
DEPRESSIONS...LIGHT WINDS AND RECENT RAINFALL TO ENHANCE FOG
POTENTIAL.  HIGH CLOUDS MOVING IN FROM THE SOUTHWEST MAY REDUCE FOG
POTENTIAL...BUT FOR NOW IT LOOKS FAIRLY FAVORABLE.  HAVE PUT IN SOME
PREVAILING MVFR VSBYS WITH TEMPO GROUPS FOR IFR AS RADIATIONAL FOG
IS LIKELY TO FLUCTUATE.  CONDITIONS TO RETURN TO VFR QUICKLY AFTER
12Z.  SHOWERS AND THUNDERSTORMS LIKELY TO DEVELOP ONCE AGAIN TUESDAY
AFTERNOON.  FOR NOW IT APPEARS THAT THEY SHOULD BE FOCUSED IN A
TROUGH AXIS EXTENDING EAST-WEST ACROSS NORTHERN MN...MAINLY NEAR
KDLH AND KHIB.  HOWEVER...ALL SITES MAY GET SOME ACTIVITY AND HAVE
PUT IN EITHER VCSH OR VCTS FOR SEVERAL HOURS DURING THE AFTERNOON.


&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  73  56  73  62 /  20  20  50  60
INL  72  49  75  57 /  40  30  30  50
BRD  75  55  77  65 /  20  10  50  60
HYR  74  54  79  64 /  20  10  40  70
ASX  75  55  80  63 /  20  20  40  60

&&

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

$$

SHORT TERM...GRANING
LONG TERM...MELDE
AVIATION...MELDE/LE






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