Area Forecast Discussion
Issued by NWS Twin Cities, MN

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000
FXUS63 KMPX 162119
AFDMPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
419 PM CDT SAT AUG 16 2014

.SHORT TERM...(THIS EVENING THROUGH SUNDAY)
ISSUED AT 419 PM CDT SAT AUG 16 2014

NO MAJOR CHANGES TO THE SHORT-RANGE FORECAST WITH CONTINUED
SHOWER/STORM CHANCES ACROSS THE NORTHERN AND WESTERN FORECAST AREA
TONIGHT AND TOMORROW.

THERE IS A NEARLY CONTINUOUS LINE OF SHOWERS AND EMBEDDED
THUNDERSTORMS STRETCHING FROM LAKE MILLE LACS IN MN AND LADYSMITH IN
WESTERN WI. THESE STORMS ARE FORMING ALONG A BACK DOOR COLD FRONT
THAT IS SLOWLY DROPPING TO THE SOUTH ACROSS THE FAR NORTHERN
FORECAST AREA. THE SLOW STORM MOTION AND FAIRLY DEEP WARM CLOUD
LAYER IS LEADING TO GOOD RAIN RATES OF 1.25"-1.75" PER HOUR WITH THE
STRONGEST CORES. THE LINE OF STORMS IS PARALLEL TO AN AXIS OF
ENHANCED PWATS /~1.5 TO 1.7/ THAT STRETCHES FROM WI TO THE EASTERN
DAKOTAS. WE EXPECT ACTIVITY TO CONTINUE ALONG THE FRONT FOR THE NEXT
SEVERAL HOURS...BUT SLOWLY DIMINISH IN COVERAGE AND INTENSITY AS WE
HEAD INTO THE LATE EVENING. THE ACTIVITY SHOULD BE ISOLATED TO
WIDELY SCATTERED BEFORE IT REACHES...ST. CLOUD...THE TWIN
CITIES...AND EAU CLAIRE.

A SECOND AREA OF THUNDERSTORMS ARE ORIENTATED FROM NW TO SE OUT
AHEAD OF TROUGH DIGGING INTO THE NORTHERN ROCKIES AND THE NORTHERN
HIGH PLAINS. A LOBE OF POTENTIAL VORTICITY NEAR THE DRYING IN THIS
AFTERNOON`S WATER VAPOR IS FORCING THE CONVECTION IN THE DAKOTAS.
THE THUNDERSTORMS ARE ALSO IN AN AXIS OF HIGHER PWATS...BUT IN
ADDITION THERE IS ALSO IN AN AREA OF 850-300MB THICKNESS
DIFFLUENCE. WE EXPECT THIS ACTIVITY TO SLOWLY SAG SOUTHEAST WITH
TIME. THIS AREA OF THUNDER WILL LIKELY AFFECT WESTERN MN TONIGHT.
LOCALLY HEAVY RAIN AMOUNTS ARE EXPECTED UNDER THE STRONGEST
CORES...WHERE A QUICK COUPLE INCHES IS POSSIBLE. THAT BEING
SAID...THE SPARSE STORM COVERAGE SUGGESTS MUCH OF SOUTHERN MN WILL
REMAIN DRY TONIGHT.

.LONG TERM...(SUNDAY NIGHT THROUGH SATURDAY)
ISSUED AT 419 PM CDT SAT AUG 16 2014

AS THE UPPER LOW CURRENTLY OVER NORTHWESTERN MT HEADS EAST ALONG
THE CANADIAN BORDER TO NORTHEASTERN NODAK BY SUNDAY NIGHT AND
MONDAY...TWO IMPULSES WILL ROTATE AROUND IT. THE FIRST WILL PUSH
ACROSS MN SUNDAY AFTERNOON AND INTO WI SUNDAY NIGHT. THIS WILL
FOCUS ANY ONGOING ACTIVITY SUNDAY OVER MAINLY WESTERN WI FOR
SUNDAY EVENING AND EARLY OVERNIGHT. THE SECOND WILL APPROACH
WESTERN MN LATE SUNDAY NIGHT AND PROPAGATE ACROSS THE REST OF THE
CWA MONDAY. SCATTERED TO NUMEROUS SHOWERS AND THUNDERSTORMS WILL
ACCOMPANY THIS IMPULSE AS IT ENCOUNTERS A MODESTLY UNSTABLE BUT
VERY MOIST ENVIRONMENT. STORM PROPAGATION VECTORS ARE QUITE
LIGHT...LESS THAN 5 KT...SO HEAVY RAINFALL AND LOCALIZED FLOODING
ARE CONCERNS. WIDESPREAD RAINFALL TOTALS OF A HALF TO THREE
QUARTERS OF AN INCH ARE A DECENT BET...BUT LOCAL AREAS COULD SEE 2
OR 3 INCHES IN A RELATIVELY SHORT PERIOD OF TIME.

THE POSITIVELY TILTED UPPER TROUGH AXIS WILL ROTATE THROUGH MONDAY
EVENING AND ALLOW FOR DWINDLING POPS BEHIND IT ACROSS WESTERN MN.
HOWEVER...THE TROUGH WILL BECOME MORE NEUTRALLY OR SLIGHTLY NEGATIVELY
TILTED OVER WI BY TUESDAY WHICH WILL LIKELY KEEP RAIN CHANCES
GOING ACROSS FAR ERN MN AND WRN WI INTO TUESDAY AFTERNOON. RIDGING
WILL PUSH THE CLOSED TROUGH EAST TO THE CENTRAL OR EASTERN GREAT
LAKES TUESDAY NIGHT AND WEDNESDAY.

THE PATTERN IS EXPECTED TO CHANGE SIGNIFICANTLY BY MID TO LATE
NEXT WEEK. FOR THE FIRST TIME THIS SUMMER...STRONG RIDGING WILL
DEVELOP OVER THE MISSISSIPPI VALLEY AND CENTRAL/SOUTHERN PLAINS
WITH A 594 DAM HEIGHT CENTERED OVER SWRN MO OR NERN OK BY
SATURDAY MORNING. HOWEVER...A FAIRLY DEEP TROUGH DOWN THE WEST
COAST AND A SOUTHWEST FLOW ACROSS THE FAR NORTHERN CONUS AND
SOUTHERN CANADA COULD BRING AN ACTIVE THUNDERSTORM PATTERN.
THUS...UNCERTAINTY INCREASES THIS PERIOD WITH RESPECT TO POPS AND
TEMPS. IT IS CONCEIVABLE TO SEE A FEW DAYS WITH HIGHS IN THE 90S...
BUT THAT WILL DEPEND ON WHETHER THUNDERSTORM COMPLEXES DEVELOP IN A
RING OF FIRE SCENARIO.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SUNDAY AFTERNOON)
ISSUED AT 1246 PM CDT SAT AUG 16 2014

IFR/MVFR CEILINGS ARE STILL SLOWLY LIFTING WITH THE AFTERNOON
SUNSHINE...BUT THE CLEARING IS ALSO HELPING TO BUILD INSTABILITY
AND WE ARE SEEING ISOLATED TO SCATTERED SHOWERS FORMING NEAR A
COLD FRONT IN CENTRAL MN AND NORTHWEST WI. WE EXPECT THE COVERAGE
TO INCREASE SLIGHTLY OVER THE NEXT FEW HOURS AND THE SHOWERS
SHOULD ALSO SLOWLY MOVE SOUTH WITH TIME. AT THIS POINT...THE
COVERAGE SHOULD BE SPARSE ENOUGH THAT MOST OF THE ACTIVITY WILL
JOG AROUND THE TAF SITES...BUT A BRIEF DOWNPOUR IS POSSIBLE THIS
AFTERNOON AND AFTERNOON AND EVENING.

KMSP...

NOW THAT THE CEILING HAS LIFTED TO 2000FT /WITH FURTHER
IMPROVEMENT EXPECTED/. NO SIGNIFICANT WEATHER IMPACTS ARE EXPECTED
THROUGH THE AFTERNOON AND EARLY EVENING. THERE ARE ISOLATED
SHOWERS DEVELOPING IN CENTRAL MN...AND IT`S NOT IMPOSSIBLE THAT
THESE EVENTUALLY IMPACT KMSP EARLY THIS EVENING...HOWEVER...THE
SHOWER COVERAGE WILL REMAIN SPARSE AND WE DECIDED TO LEAVE THE
MENTION OF RAIN OUT OF THE FORECAST FOR NOW. WE THINK MSP WILL BE
CLOSE TO THE FRONT THIS EVENING AND LOW STRATUS SEEMS POSSIBLE ONE
AGAIN LATE TONIGHT.

/OUTLOOK FOR KMSP/
SUN NIGHT...VFR. MVFR WITH TSRA POSSIBLE WINDS E 5-10 KTS.
MON...VFR/MVFR WITH TSRA LIKELY AFTN/NIGHT. WINDS S 5-10 KTS.
TUE...VFR/MVFR WITH TSRA POSSIBLE. WINDS NW 5-10 KTS.

&&

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

$$

SHORT TERM...CLF
LONG TERM...BORGHOFF
AVIATION...CLF






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