Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 281140
AFDMPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
640 AM CDT TUE APR 28 2015

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 403 AM CDT TUE APR 28 2015

A COLD FRONT BISECTS THE STATE FROM NORTHEAST TO SOUTHWEST EARLY
THIS MORNING. A BAND OF LIGHT RAIN EXISTS IN THE WAKE OF THE FRONT
FROM NORTH CENTRAL MN THROUGH EAST CENTRAL SD ASSOCIATED WITH A
BAND OF MID LEVEL FRONTOGENESIS. MULTIPLE WRF FORECASTS INDICATE
THE BAND OF LIGHT RAIN WEAKENING...WITH A FEW MEMBERS EVEN SHOWING
DISSIPATION THIS MORNING...AS IT HEADS INTO CENTRAL AND SOUTHWEST
AREAS OF MN. THIS SEEMS PLAUSIBLE GIVEN THE FORECAST WEAKENING OF THE
MID LEVEL FRONTOGENESIS/THERMAL GRADIENT. HOWEVER...THE AFTERNOON
AND EARLY EVENING TIME PERIODS ARE A LITTLE DIFFERENT. EVEN
THOUGH THERE IS SOME WEAKENING FORECAST THIS MORNING...EASTERN MN
AND WESTERN WI WILL BE IN THE LEFT EXIT REGION OF THE 250MB JET
THIS AFTERNOON ALONG WITH BEING UNDER THE SHORT WAVE/COLD TROUGH
AT 500 MB. NSHARP PROFILES FROM THE NAM AND GFS SHOW RATHER STEEP
MID LEVEL LAPSE RATES OCCURRING. THIS COUPLED WITH WEAK FORCING
AND LAYER MOISTURE SHOULD YIELD ISOLATED TO SCATTERED SHOWERS
DEVELOPING EARLY IN THE AFTERNOON TO THE NORTH AND WEST OF THE
TWIN CITIES...WITH THE ACTIVITY WORKING INTO WEST CENTRAL WI AND
SOUTH CENTRAL MN BY LATE IN THE AFTERNOON AND THEN DISSIPATING
EARLY THIS EVENING. HENCE...FOLLOWED THE IDEA OF THE NSSL WRF AND
NCAR ENSEMBLE WRF. THE LATTER SHOWS THAT THERE IS QUITE A BIT OF
SPREAD IN THE SIMULATED REFLECTIVITY THIS AFTERNOON. THIS CAN BE
SEEN QUITE WELL IN THE NCAR ENSEMBLE SOUNDING FOR KMSP. IF ONE
WERE TO REMOVE A FEW OF THE DRIER PROFILES...THE SOUNDING WOULD
HAVE A BETTER DEEP LAYER MOISTURE PROFILE. THEREFORE...USED SOME
20/30 POPS FOR TODAY ACROSS MUCH OF THE MN CWA AND ADJOINING AREAS
OF WESTERN WI. A CONCERN TODAY IS THE HIGH TEMPERATURE FORECAST
DUE TO THE INCREASE IN CLOUDS AS THE DAY PROGRESSES ALONG WITH
SOME SHOWERS. WENT A FEW DEGREES COOLER THAN THE PREVIOUS
FORECAST...BUT THIS MAY STILL BE TOO WARM AND MAY NEED TO BE
TWEAKED FURTHER THIS MORNING. CLEARING WILL OCCUR TONIGHT AS HIGH
PRESSURE BUILDS IN FROM THE WESTERN DAKOTAS. THE LOW TEMPERATURE
FORECAST LOOKED TOO WARM OVER OUR WESTERN CWA DUE TO DEW POINTS
FALLING INTO THE UPPER 20S AND LOWER 30S. USED A BLEND OF
BCCONSRAW AND GEMNHBC WHICH BROUGHT LOWS DOWN INTO THE MIDDLE 30S
ACROSS PORTIONS OF CENTRAL MN.

.LONG TERM...(WEDNESDAY THROUGH MONDAY)
ISSUED AT 403 AM CDT TUE APR 28 2015

THE LONG TERM WILL FEATURE A DECIDEDLY MORE SUMMER-LIKE UPPER AIR
PATTERN...ONCE THE DEEP AND PERSISTENT ERN NOAM UPPER LOW LIFTS INTO
THE ATLANTIC THIS WEEKEND...SETTING UP A WAVY ZONAL FLOW ACROSS THE
NRN CONUS THIS WEEKEND INTO NEXT WEEK.

THE LONG TERM WILL START WITH AN UPPER RIDGE BUILDING ACROSS THE
PLAINS AS AN UPPER LOW DIVES SOUTH THROUGH THE WRN GREAT LAKES ON
THE WRN EDGE OF THE ERN NOAM UPPER LOW. THIS WILL LIKELY LEAD TO
INCREASED CLOUD COVER ACROSS WRN WI ON WEDNESDAY...THOUGH ANY
INSTABILITY DRIVEN SHOWERS BENEATH THE UPPER COLD POOL LOOK TO STAY
OVER ERN WI. THIS FEATURE MOVES TOWARD INDIANA WEDNESDAY
NIGHT...TAKING THE CLOUD COVER WITH IT. AT THE SFC...DRY HIGH
PRESSURE WILL DOMINATE THE REGION WEDNESDAY AND THURSDAY. DEEP
MIXING IS EXPECTED BOTH DAYS...AND AS WE HAVE SEEN THROUGHOUT THIS
SPRING...THIS CALLS FOR LOWERING DEWPOINTS BELOW GUIDANCE AND
FAVORING BIAS CORRECTED FORECASTS FOR HIGHS...WHICH WAS DONE BOTH
DAYS.

THURSDAY NIGHT...MODELS CONTINUE TO SHOW ANOTHER SHORTWAVE AND COLD
FRONT MOVING THROUGH THE AREA WITH MAINLY MINOR TIMING DIFFERENCES
NOTED. UNLIKE TODAYS FRONT...THIS FRONT WILL MAINTAIN BETTER
DEFINITION COMING INTO MN...WITH RAINFALL CHANCES LOOKING MORE
LIKELY WITH THIS FRONT THURSDAY NIGHT INTO FRIDAY. HOWEVER...LIKE
TODAYS FRONT...IT WILL BE WASHING OUT FRIDAY AFTERNOON AS THE
SHORTWAVE BECOMES SHEARED OUT...MEANING RAINFALL CHANCES ARE BETTER
TO THE WEST AS OPPOSED TO THE EAST. DID RAISE POPS INTO THE HIGH
CHANCE CATEGORY FOR WRN MN LATE THURSDAY NIGHT AS MODEL AGREEMENT IS
LOOKING BETTER ON RAIN MOVING INTO THE WEST LATE THURSDAY NIGHT. DID
REMOVE THUNDER WITH THIS SYSTEM AS WELL AS BOTH THE GFS AND ECMWF
SHOW NO INSTABILITY PRESENT WITH THE WAVE AS IT MOVES THROUGH.

FOR THE WEEKEND...WITH ZONAL FLOW SETTING UP...WE WILL SEE A PLUME
OF RATHER MILD H85 AIR MOVE INTO THE UPPER MS VALLEY IN THE WAKE OF
FRIDAYS SYSTEM...WITH THE ECMWF CONTINUING TO SHOW H85 TEMPS IN
EXCESS OF +12C. DID ADD SOME BIAS CORRECTED CONSENSUS GRIDS INTO THE
INITIAL CENTRAL REGION BLEND FOR HIGHS ON SATURDAY TO GET MORE MID
70S TO LOWER 80S IN THE GRIDS FOR SATURDAY...WHICH LOOKS TO OFFER
SOME SUNNY SKIES BEFORE THE WARM FRONT ARRIVES SATURDAY NIGHT. AS
FOR THAT WARM FRONT...THOUGH SPREAD IS TYPICAL OF WHAT YOU WOULD
EXPECT THIS FAR OUT FOR SATURDAY NIGHT THROUGH SUNDAY NIGHT...THE
GFS/GEM/ECMWF ALL AGREE ON THE GENERAL IDEA OF A WARM FRONT LIFTING
NORTH INTO THE AREA SATURDAY NIGHT...FOLLOWED BY A COLD FRONT OR SFC
LOW PASSAGE SUNDAY INTO SUNDAY NIGHT. THIS SYSTEM WILL BE BRINGING
UP SOME MODIFIED TROPICAL AIR...WITH DEWPS LIKELY INTO THE
60S...WHICH WILL RESULT IN A DECENT AMOUNT OF INSTABILITY FOR THE
SYSTEM COMING THROUGH SUNDAY. THOUGH KINEMATIC FIELDS ARE MARGINAL
FOR ANY SORT OF SEVER POTENTIAL...PLENTY OF INSTABILITY LOOKS TO
EXIST TO GIVE US A GOOD SHOT AT SOME THUNDERSTORMS. AS A
RESULT...HAVE FAIRLY WIDESPREAD CHANCE POPS SUNDAY INTO SUNDAY
NIGHT...WITH THE THUNDER WORDING MORE THAN WARRANTED IN THE FORECAST
THIS TIME AROUND.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z WEDNESDAY MORNING)
ISSUED AT 640 AM CDT TUE APR 28 2015

A COLD FRONT JUST WEST AND NORTH OF THE TWIN CITIES AT TAF
ISSUANCE WILL MOVE EAST OF KEAU BY MID MORNING. A BROKEN BAND OF
SHOWERS WELL IN THE WAKE OF THE FRONT WILL BRING A FEW HOUR PERIOD
OF LOW MVFR CEILINGS OR PERHAPS EVEN IFR TO KAXN THIS MORNING. THE
SHOWERS CURRENTLY NEAR KAXN SHOULD DISSIPATE THROUGH THE MORNING
AND NOT BE A PROBLEM FOR KSTC/KRWF. HOWEVER... IN THE
AFTERNOON...SHOWERS ARE EXPECTED TO REDEVELOP JUST WEST AND NORTH
OF THE TWIN CITIES AND MOVE ESE BEFORE DISSIPATING EARLY IN THE
EVENING. AN ISOLATED THUNDERSTORM CAN`T BE RULED OUT BUT CHANCES
ARE QUITE LOW AT THIS TIME. VCSH CONTINUES FOR KMSP AND KRNH FOR A
GOOD PORTION OF THE AFTERNOON HOURS. CEILINGS WITH THE AFTERNOON
SHOWERS ARE EXPECTED TO REMAIN VFR. NORTHWEST TO NORTH WINDS IN
THE WAKE OF THE COLD FRONT WITH SPEEDS 10-12 KNOTS GUSTING 18
KNOTS.

KMSP...SHOWER THREAT GREATEST IN THE 21Z-23Z TIME FRAME. A
LIGHTNING STRIKE OR TWO CAN/T BE RULED OUT. CEILINGS AOA 050 THIS
AFTERNOON.

/OUTLOOK FOR KMSP/
WED...VFR. WINDS N 5-10 KTS.
THU...VFR. WINDS E 5-10 KTS.
FRI...VFR. CHANCE OF SHOWERS. WINDS S 10 KTS.

&&

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

$$

SHORT TERM...RAH
LONG TERM...MPG
AVIATION...RAH


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