Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 200524
AFDMPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
1224 AM CDT SUN APR 20 2014

.UPDATE...
ISSUED AT 1212 AM CDT SUN APR 20 2014

UPDATED TO INCLUDE 06Z AVIATION DISCUSSION BELOW.

&&

.SHORT TERM...(THIS EVENING THROUGH SUNDAY)
ISSUED AT 346 PM CDT SAT APR 19 2014

EARLY AFTERNOON WATER VAPOR IMAGERY TOGETHER WITH 500MB HEIGHTS AND
WINDS OFF THE 19.12 GFS IDENTIFIED 5 WELL DEFINED PV ANOMALIES
ACROSS NORTH AMERICA. THREE OF THESE WAVES WERE LOCATED IN THE
NORTHERN STREAM ALONG THE INTERNATIONAL BORDER. THE ONE IN THE
CENTER WAS OVER MANITOBA...WHILE THE OTHER TWO WERE EQUIDISTANT
UPSTREAM AND DOWNSTREAM. MEANWHILE WITH THE REMAINING TWO WAVES WERE
IN THE SOUTHERN STREAM STRADDLING EITHER COAST...WITH ONE OVER THE
BAJA PENINSULA...AND THE OTHER OVER FLORIDA.

A CLOSER LOOK AT THE SURFACE REFLECTION OF THE NORTHERN STREAM WAVE
OVER MANITOBA REVEALED A 1004MB SURFACE LOW...WITH A TRAILING COLD
FRONT EXTENDING FROM INTERNATIONAL FALLS...DOWN THROUGH THE
SOUTHWEST CORNER OF MINNESOTA. AN AREA OF COOL CLOUD TOPS WAS
LOCATED AHEAD OF THIS FRONTAL BOUNDARY ALONG THE AXIS OF DEEP
MOISTURE CONVERGENCE...WHERE WITH LESS THAN 100 J/KG OF MUCAPE. THIS
INSTABILITY HAD DECREASED OVER THE PAST FEW HOURS...WITH ONLY A FEW
LIGHT SPRINKLES BEING REPORTED AS OF 19Z. THEREFORE HAVE DECREASED
POPS AS MOST LOCATIONS WILL NOT SEE MEASURABLE PRECIP WITH THE
FRONTAL PASSAGE THIS EVENING.

LATER TONIGHT THE SHORTWAVE THAT WAS LOCATED OVER THE BAJA
PENINSULA WILL MOVE ONSHORE AND CAUSE A TROUGH OF LOW PRESSURE TO
FORM ALONG THE TX/OK PANHANDLES. THIS WILL CAUSE THE MIDWEST
FRONTAL BOUNDARY TO STALL OUT ALONG A LINE FROM OMAHA...THROUGH LA
CROSSE WI...TO GREEN BAY WI. CONFIDENCE IS HIGH THAT PRECIP WILL
DEVELOP ALONG THAT FRONTAL BOUNDARY LATER TONIGHT AND PERSIST
THROUGH THE DAY ON SUNDAY. FORECAST SOUNDING SHOW ELEVATED
INSTABILITY...SO WILL HAVE THUNDER AS WELL...AND A FEW LOCATIONS
SHOULD SEE AN INCH TO PERHAPS 2 OF PRECIP AS THE BOUNDARY REMAINS
STATIONARY THROUGH SUNDAY BEFORE SLOWLY DRIFTING SOUTHEAST.

.LONG TERM...(SUNDAY NIGHT THROUGH SATURDAY)
ISSUED AT 346 PM CDT SAT APR 19 2014

SHOWERS AND ISOLATED THUNDERSTORMS ARE LIKELY SUNDAY NIGHT ALONG
THE FRONTAL BOUNDARY MEANDERING FROM SOUTHERN MN INTO WEST CENTRAL
WI. MODEL AGREEMENT IS HIGH WITH THIS SCENARIO WITH MORE THAN AN
INCH OF QPF LIKELY JUST SOUTH AND EAST OF OUR FORECAST AREA. A
GROWING CONCERN FOR SUNDAY NIGHT IS HOW THE MODELS HANDLE THE
INTERACTION BETWEEN A NORTHERN STREAM SHORT WAVE APPROACHING FROM
THE DAKOTAS AND A SOUTHERN STREAM SHORTWAVE LIFTING NORTHEAST
THROUGH THE CENTRAL PLAINS. SEVERAL RUNS OF THE GEM AND EC WOULD
SUGGEST HAVING SOME LIGHT SHOWERS ALL THE WAY BACK INTO CENTRAL
MN. THE GFS AND NAM HAVE BEEN HOLDING TIGHT ACROSS THE EASTERN AND
SOUTHERN CWA. WE NOTICED TODAY THAT THE EC WAS A LITTLE TOO
GENEROUS WITH THE SHOWERS ACROSS CENTRAL THROUGH SOUTHWEST MN.
WITH THIS IN MIND...HELD LIKELY POPS FROM NEAR ALBERT LEA TO EAU
CLAIRE SUNDAY NIGHT WITH CHANCE POPS FROM REDWOOD FALLS THROUGH
THE TWIN CITIES METRO TO LADYSMITH.

THE SHOWERS END EARLY MONDAY MORNING ACROSS WEST CENTRAL WI AND
SOUTHEAST MN AS THE SHORTWAVE ENERGY PUSHES EAST. HIGH PRESSURE
WILL BUILD IN WITH VERY PLEASANT WEATHER THROUGH TUESDAY. HIGHS IN
THE 60S WILL BE COMMON ON MONDAY WITH MIDDLE 50S TO LOWER 60S ON
TUESDAY. AFTERNOON HUMIDITY WILL LOWER TO AROUND 35 PERCENT
TUESDAY AFTERNOON.

THE THREAT FOR SHOWERS WILL RETURN TO WESTERN MN TOWARDS DAYBREAK
ON WEDNESDAY. THIS IS AHEAD OF A LARGE STORM SYSTEM PUSHING
THROUGH THE WESTERN CONUS. SHOWERS AND ISOLATED THUNDERSTORMS WILL
BECOME MORE NUMEROUS ACROSS THE FA WEDNESDAY AND WEDNESDAY NIGHT.
AS THE UPPER WAVE PUSHES INTO THE PLAINS ON THURSDAY IT BEGINS TO
TAKE ON A NEGATIVE TILT. MODEL SOLUTIONS ARE QUITE VARIED AT THIS
TIME ON THE TRACK OF THE SURFACE LOW PRESSURE SYSTEM EMANATING
FROM THE CENTRAL PLAINS ON THURSDAY. THE GEM AND GFS WOULD FAVOR
MOVING THE LOW ALMOST DUE NORTH INTO THE EASTERN DAKOTAS WHILE THE
EC WOULD HAVE THE LOW REACHING SOUTHERN MN. ALL OF THE SOLUTIONS
SHOW INCREASING SHEAR AND INSTABILITY...ESPECIALLY ACROSS SOUTHERN
MN. SOUTHERLY WINDS AT 500 MB REACH OR EXCEED 50 KNOTS OVER
PORTIONS OF THE FA ON ALL THREE SOLUTIONS. DEPENDING ON HOW THINGS
EVOLVE...THERE CERTAINLY COULD BE A WINDOW OF OPPORTUNITY FOR
SEVERE WEATHER ON THURSDAY ACROSS PORTIONS OF THE FA. THURSDAY
HAPPENS TO BE OUR SEVERE WEATHER DRILL DAY.

THE BIGGEST DISAGREEMENT IN THE LONG TERM IS HOW FAST THIS STORM
SYSTEM EXITS THE REGION. THE EC IS THE FASTEST AND WOULD HAVE
MUCH OF THE AREA DRY BY FRIDAY AFTERNOON. HOWEVER...THE GFS AND
GEM WOULD FAVOR MORE OF A SLOW MOVING CLOSED UPPER LOW OVER THE
AREA INTO SATURDAY. AS THE THERMAL PROFILE COOLS...IT WOULD OFFER
THE CHANCE FOR SOME LIGHT SNOW ACROSS MUCH OF THE AREA FRIDAY
NIGHT.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SUNDAY NIGHT)
ISSUED AT 1212 AM CDT SUN APR 20 2014

PRIMARY AVIATION CONCERNS ARE THE CHANCES FOR SOME SHRA OVER THE
SOUTHEAST HALF OR SO OF THE AREA OVERNIGHT INTO THE MORNING... ALONG
WITH THE POTENTIAL FOR FOG FROM THE NORTHERN EDGE OF THAT PCPN ON
NORTHWARD DURING THE OVERNIGHT HOURS INTO EARLY THIS MORNING. A
FRONTAL BOUNDARY IS VERY SLOWLY SINKING SOUTHEAST... WITH SOME
WEAK WARM ADVECTION AND MOISTURE TRANSPORT ALOFT HELPING TO KEEP
SCATTERED SHRA GOING NEAR THE BOUNDARY. THE HRRR AND HOPWRF KEEP
SOME ACTIVITY NEAR KMSP FOR THE NEXT FEW HOURS... THEN DROP IT
SOUTHEAST AND OUT OF ALL BUT PERHAPS KEAU BY MORNING. CEILINGS
SHOULD REMAIN VFR WITH ANY SHRA... BUT COULD SEE VISIBILITIES DIP
INTO MVFR RANGE FOR BRIEF PERIODS. NORTH OF THE FRONTAL BOUNDARY
AND SCATTERED SHRA WE/RE SEEING FOG DEVELOP IN AREAS NORTH OF THE
CLOUD COVER... PARTICULARLY WHERE SNOW MELTED YESTERDAY. COULD
DEFINITELY SEE SOME ISSUES WITH IFR AND PERHAPS SOME LIFR AT KSTC
AND KRNH THROUGH 13Z OR SO THIS MORNING. OTHERWISE... THE NEXT
ITEM OF INTEREST WILL BE A WEAK SHORTWAVE THAT IS EXPECTED TO MOVE
THROUGH THE REGION LATER TONIGHT... POTENTIALLY REJUVENATING THE
SHRA ACTIVITY ACROSS THE AREA SINCE THE BAROCLINIC ZONE WILL STILL
BE LOITERING IN THE VICINITY. IT APPEARS TO BE AN ISSUE MAINLY
AFTER 06Z... SO AT THIS POINT THE ONLY TAF WHERE ANY MENTION IS
NEEDED SHOULD BE KMSP... SO INCLUDED A VCSH THERE AFTER 07Z.

KMSP...PRIMARY UNCERTAINTIES ARE WITH WHEN WE/LL SEE THE CURRENT
SHRA ACTIVITY FINALLY DROP SOUTH OF THE AREA. HAVE REASONABLE
CONFIDENCE IN THE FORECAST TIMING... BUT IT/S POSSIBLE IT COULD BE
1-2 HOURS SLOWER. IN ADDITION... INCLUDED SOME MVFR FOG BEFORE
DAYBREAK AS THE THICKER CLOUD COVER DEPARTS AND WE POTENTIALLY SEE
A BIT OF RADIATION FOG DEVELOPMENT. CONFIDENCE IN THAT POSSIBILITY
IS ALSO FAIRLY LOW... AND IT COULD EASILY NOT OCCUR OR BE A BIT
WORSE SHOULD CLOUDS DEPART MORE QUICKLY THAN EXPECTED.

/OUTLOOK FOR KMSP/
MONDAY...MVFR CEILINGS AND VISIBILITIES POSSIBLE EARLY WITH A
CHANCE OF SHRA. NORTHWEST WIND 10 TO 20 KT.
MONDAY NIGHT...VFR. NORTHWEST WIND 10 TO 15 KT.
TUESDAY...VFR. NORTHWEST WIND LESS THAN 10 KT BECOMING VARIABLE
LESS THAN 5 KT.
TUESDAY NIGHT...VFR. SOUTHEAST WIND 5 TO 10 KT.
WEDNESDAY THROUGH THURSDAY...MVFR CEILINGS AND VISIBILITIES
EXPECTED WITH RAIN LIKELY. IFR CONDITIONS POSSIBLE ALONG WITH A
CHANCE OF THUNDERSTORMS. SOUTHEAST WIND 10 TO 20 KT BECOMING
SOUTHWEST.

&&

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

$$

UPDATE...
SHORT TERM...JRB
LONG TERM...RAH
AVIATION...






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