Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 190920
AFDMPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
420 AM CDT TUE AUG 19 2014

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 358 AM CDT TUE AUG 19 2014

TODAY AND TONIGHT...SFC ANALYSIS DEPICTS A LOW PRES CENTER CROSSING
INTO NWRN WI EARLY THIS MRNG...WITH A CDFNT DRAGGING OVER SERN MN
INTO FAR SWRN WI. ALOFT...A UPR LVL LOW OFFSET TO THE NNW FROM THE
SFC LOW WILL ACCOMPANY THE SFC LOW TO THE E INTO THE GREAT LAKES
TDA. THIS WILL DRAG ANY REMAINING SHOWERS/T-STORMS OFF INTO WI.
HOWEVER...IN ITS WAKE WILL BE PLENTY OF LLVL MOISTURE ALONG WITH
COOLER AIR THAT MAY WELL BE CONDUCIVE TO FOG DEVELOPMENT. KEY FACTOR
FROM THIS MRNG COMPARED TO YDA MORNING...WHERE DENSE FOG WAS
PREVALENT OVER WRN MN...IS THAT WINDS ARE SHIFTING TO NW BEHIND THE
SFC LOW AND AT SPEEDS IN THE 5-10KT RANGE...HELPING KEEP THINGS
MIXED JUST ENOUGH TO AVOID MORE WIDESPREAD FOG COVERAGE. GOING
BEYOND DAYBREAK...A LINGERING NW-SE TROUGH EMANATING FROM THE NWRN
SIDE OF THE SFC LOW WILL FOLLOW THE LOW AND MAKE ITS WAY INTO NWRN
MN INTO WRN WI. THIS SFC TROF WILL ACT AS A LLVL CONVERGENCE
BOUNDARY FOR MOISTURE AND LIFT WHILE THE SHORTWAVE TROUGH AXIS
ALOFT...WHICH CONTAINS THE UPR LVL LOW...MOVES ATOP SFC TROUGH...
HELPING AID LIFT FOR ERN PORTIONS OF THE MPX CWFA. THIS COMBINATION
WILL BE ENOUGH TO PRODUCE SCATTERED SHWRS/TSTMS MAINLY THIS AFTN
OVER ERN PORTIONS OF THE CWFA. NOT LOOKING FOR A LOT OF COVERAGE NOR
INTENSITY BUT PRECIP MENTION IS CERTAINLY WARRANTED. AS FOR
CENTRAL-WRN MN...HIGH PRESSURE WILL START TO MAKE INROADS TO THE UPR
MISS RIVER VALLEY...ALLOWING FOR CLEARING SKIES WELL IN THE WAKE OF
THE SFC LOW. PRECIP OVER THE ERN PORTIONS WILL STEADILY SHIFT OFF TO
THE E THIS EVE WHILE SKIES CLEAR OUT...ALLOWING FOR DECENT
RADIATIONAL COOLING CONDS OVERNIGHT TNGT INTO WED MRNG. THE CONCERN
AGAIN BECOMES FOG DEVELOPMENT. WITH WINDS DROPPING OFF AND COOLER
BLYR AIR ATOP STILL MOIST DEWPOINTS SHOULD MAKE FOR AT LEAST AREAS
OF FOG...IF NOT THE PROTOTYPICAL WIDESPREAD FOG. AM NOT QUITE
CONFIDENT ENOUGH TO GO WITH DENSE FOG MENTION ATTM...BUT WOULD NOT
BE SURPRISED IF THAT IS INDEED THE CASE 24 HOURS FROM NOW.
TEMPERATURES TDA WILL BE A LITTLE COOLER BEHIND THE DEPARTING SFC
LOW PRES SYSTEM. WILL LOOK FOR HIGHS FROM THE LWR 70S TO LWR
80S...THE LOWER END OF THAT RANGE IN WRN WI AND THE HIGHER END OF
THAT RANGE IN SWRN MN WHERE CLEARING WILL BE MOST EFFICIENT.


.LONG TERM...(WEDNESDAY THROUGH MONDAY)
ISSUED AT 358 AM CDT TUE AUG 19 2014

TWO MAIN ROUNDS OF CONVECTION WILL DEVELOP LATE WEDNESDAY INTO
THURSDAY...AND AGAIN FRIDAY NIGHT INTO SATURDAY. THE PREVIOUS
FORECAST WAS IN VERY GOOD SHAPE...SO DID NOT MAKE ANY SIGNIFICANT
CHANGES.

AT THE START OF THE PERIOD A SHORTWAVE WILL LIFT FROM THE WYOMING
FOOTHILLS UP ACROSS NORTHERN MINNESOTA. THIS DRAG A WARM FRONT UP
FROM THE SOUTH...WHICH WILL BE THE FOCUS FOR SHOWERS AND
THUNDERSTORMS LATE WEDNESDAY INTO THURSDAY. CONFIDENCE IS HIGH THAT
AN MCS WILL DEVELOP THURSDAY NIGHT AND BRING HEAVY RAIN ACROSS THE
UPPER MIDWEST. A FEW LOCALIZED AREAS SHOULD SEE AROUND 2 INCHES.
SEVERE WEATHER IS ALSO POSSIBLE WITH THE ELEVATED CONVECTION. BUFR
SOUNDINGS SHOW 30-40KTS OF 1-6KM SHEAR...WITH A VEERING WIND
PROFILE...SO STORMS MAY BE FAIRLY ORGANIZED WEDNESDAY NIGHT. AT THIS
TIME...SEVERE WIND WOULD BE THE PRIMARY THREAT...WITH A SECONDARY
THREAT OF HAIL...AND NEARLY ZERO THREAT OF TORNADOES.

THIS CONVECTION WILL LINGER INTO THURSDAY AS THE FRONT LIFTS
NORTHWARD. THE GFS CONTINUE TO SHOW ANOTHER SHORTWAVE EJECTING
NORTHEAST FROM THE CALIFORNIA TROUGH ON FRIDAY...BUT THE ECMWF AND
GEM REMAIN DRY SO DO HAVE HAVE MUCH FAITH IN THE GFS SOLUTION. THIS
IMPACTS THE REST OF THE FORECAST AS WELL...WITH THE GEM AND ECMWF IN
GOOD AGREEMENT ON PRECIP ACROSS THE SOUTHERN HALF OF THE CWA FRIDAY
NIGHT INTO SATURDAY. THEREFORE CONTINUED LIKELY POPS SATURDAY
NIGHT...WITH A BLENDED SOLUTION CARRIED ON THROUGH THE WEEKEND.
TEMPERATURES WILL DEPEND ON CLOUD COVER AND LOCATION OF THE WARM
FRONT...NEAR 90 SOUTH OF THE FRONT...AND UPPER 70S ALONG AND
NORTH OF THE FRONT.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z TUESDAY NIGHT)
ISSUED AT 1159 PM CDT MON AUG 18 2014

FOG/STRATUS IS LIKELY IN WESTERN WI EARLY THIS MORNING...BUT EVEN
KMSP/KSTC/KAXN COULD BE ON THE FRINGE OF MVFR CONDITIONS
/ESPECIALLY MVFR CEILINGS/. PRECIP CHANCES INCREASE IN THE
AFTERNOON IN FAR EASTERN MN AND IN WI.

KMSP...
WE`VE GONE BACK AND FORTH AT KMSP ON WHETHER WE THINK THERE WILL
BE LOW STRATUS AROUND FOR THE MORNING RUSH. WE KNOW IT WILL BE
CLOSE...BUT WE ARE STILL NOT TOTALLY SURE HOW EXPANSIVE THE CLOUDS
WILL BE IN MN. WE ARE CONFIDENT IN STRATUS OFF TO THE NORTH AND
EAST...BUT A SLIGHTLY DRIER WESTERLY FLOW WILL LIKELY KEEP KMSP
FROM DROPPING TOO LOW ON THE CEILINGS AND VISIBILITY OVER THE NEXT
6-9 HOURS.

/OUTLOOK FOR KMSP/
WED...VFR. WIND E 5-10 KTS.
THU...VFR. CHC MVFR WITH TSRA. WINDS SE 5-10 KTS BECMG SW.
FRI...VFR. CHC MVFR WITH TSRA. WINDS NE 5-10 KTS.


&&

.MPX WATCHES/WARNINGS/ADVISORIES...
MN...NONE.
WI...NONE.
&&

$$

SHORT TERM...JPC
LONG TERM...JRB
AVIATION...CLF





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