Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 170004
AFDMPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
704 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 00Z TAFS THROUGH 00Z SUNDAY EVENING)
ISSUED AT 704 PM CDT SAT AUG 16 2014

A TOUGH NIGHT AHEAD ON AVIATION DUE TO SEVERAL FACTORS. THE FIRST
IS A WEAK COOL FRONT NEARING A KSTC-KEAU LINE EARLY THIS EVENING.
THE FRONT IS DRIFTING SLOWLY SW AND WILL LIKELY STALL OUT SOUTH OF
THE TWIN CITIES TO KAXN LATE IN THE NIGHT. SHOWERS AND A FEW
THUNDERSTORMS WILL PERSIST FOR A FEW MORE HOURS ALONG THE FRONT
WITH JUST ISOLATED ACTIVITY THEREAFTER. THE SHOWERS ARE VERY
EFFICIENT RAIN PRODUCERS WITH BOUTS OF VERY HEAVY RAINFALL. SURFACE
DEW POINTS ARE NOT GOING TO LOWER MUCH BEHIND THE FRONT AND
THIS WILL LIKELY LEAD TO MORE FOG/STRATUS DEVELOPING OVERNIGHT...
SIMILAR TO EARLIER THIS MORNING. TO THE WEST AND SOUTH OF THE
BOUNDARY (WEST CENTRAL THROUGH SOUTH CENTRAL MN) LIES A VERY MOIST
AIRMASS. THIS TOO IS VERY SIMILAR TO LAST NIGHT AND EXTENSIVE
STRATUS AND FOG (LOW MVFR/IFR) IS EXPECTED TO DEVELOP ONCE AGAIN
IN THESE AREAS AS WELL LATE TONIGHT AND PERSIST THROUGH MUCH OF
THE MORNING ON SUNDAY. FINALLY...A SHORT WAVE OVER CENTRAL ND WILL
DROP INTO WEST CENTRAL MN AFTER MIDNIGHT. THIS FEATURE WILL MOVE
SLOWLY ACROSS MN ON SUNDAY AND WESTERN WI SUNDAY NIGHT. THUNDERSTORM
ACTIVITY IS POSSIBLE AT KAXN AND KRWF BY 09Z WITH THE THREAT
WORKING INTO THE TWIN CITIES BY SUNDAY AFTERNOON AND WESTERN WI BY
EVENING. AGAIN...THESE SHOWERS AND THUNDERSTORMS WILL CONTAIN
BOUTS OF VERY HEAVY RAINFALL. WINDS WILL BE LIGHT TONIGHT AND
MAINLY FROM THE NE BEHIND THE FRONT AND ESE AHEAD OF IT. SE WINDS
5 TO 10 KNOTS ON SUNDAY.

KMSP...A SMALL THREAT FOR A SHOWER OR ISOLATED THUNDERSTORM LATE
THIS EVENING AS A WEAK COOL FRONT MOVES IN FROM THE NORTHEAST. LOW
MVFR CEILINGS EXPECTED ONCE AGAIN LATE TONIGHT AND SUNDAY MORNING.
THUNDERSTORM CHANCES ON THE INCREASE SUNDAY AFTERNOON.

/OUTLOOK FOR KMSP/
SUN NIGHT...VFR. MVFR WITH TSRA POSSIBLE. WINDS SE 5-10 KTS.
MON...VFR/MVFR WITH TSRA LIKELY. 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...RAH








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