Area Forecast Discussion
Issued by NWS Twin Cities, MN

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000
FXUS63 KMPX 270400
AFDMPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
1100 PM CDT FRI JUN 26 2015

.SHORT TERM...(THIS EVENING THROUGH SATURDAY)
ISSUED AT 242 PM CDT FRI JUN 26 2015

EARLY AFTERNOON WATER VAPOR IMAGERY IDENTIFIED A WEAK SHORTWAVE
DROPPING DOWN ACROSS NORTHERN MINNESOTA.  COOLING ALOFT TOGETHER
WITH DIURNAL HEATING WAS ENOUGH TO DESTABILIZE THE ATMOSPHERE WHICH
RESULTED IN SHOWERS AND THUNDERSTORMS ACROSS MAINLY CENTRAL MN THIS
AFTERNOON. EFFECTIVE SHEAR IS ONLY AROUND 20KTS...AND CAPE VALUES
ARE ON THE ORDER OF 1000 TO 1500 J/KG...SO THE THREAT FOR SEVERE
WEATHER IS NEARLY ZERO. A STRAY LIGHTING STRIKE AND A FEW MINUTES OF
HEAVY RAIN ARE THE PRIMARY SENSIBLE WEATHER FEATURES OF THESE
SHOWERS AND THUNDERSTORMS.

AS THE WAVE SHIFTS SOUTHWARD AND PEAK HEATING WANES THE SHOWERS AND
THUNDERSTORMS WILL DIMINISH ACROSS THE REGION. TONIGHT WINDS WILL BE
LIGHT AND VARIABLE. HYDROLAPSE SHOWS DECREASING MOISTURE WITH
HEIGHT...SO NOT ANTICIPATING FOG...BUT RATHER A HEAVY DEW BY
MORNING. ON SATURDAY TEMPERATURES WILL WARM INTO THE LOWER/MID 80S
WITH MOSTLY CLEAR SKIES. WINDS WILL BECOME SOUTHWESTERLY BY
AFTERNOON. A POTENT SHORTWAVE ON THE OWING TO THE CYCLONIC SHEAR
ASSOCIATED WITH A 100KT JET STREAK WILL DROP DOWN FROM CANADA AND
LEAD TO A TROUGH OF LOW PRESSURE ACROSS THE DAKOTAS AND NORTHERN MN
BY SATURDAY AFTERNOON. MID LEVEL LAPSE RATES OF 7 TO 8 C/KM TOGETHER
WITH 40-50KTS OF EFFECTIVE SHEAR WILL SUPPORT THE POTENTIAL FOR SOME
STRONGER UPDRAFTS. THE PRIMARY SEVERE THREAT IS LARGE HAIL.
FORECAST SOUNDINGS SHOW LCLS ON THE ORDER OF 5000FT WITH A LINEAR
WIND PROFILE...SO NOT ANTICIPATING A TORNADIC THREAT...BUT A FEW
WIND GUSTS ARE POSSIBLE GIVEN THE INVERTED-V SOUNDINGS. SPC HAS
UPGRADED THE FAR NORTHWESTERN PORTIONS OF THE CWA TO A SLIGHT
RISK.

.LONG TERM...(SATURDAY NIGHT THROUGH FRIDAY)
ISSUED AT 242 PM CDT FRI JUN 26 2015

THE LARGE SCALE PATTERN WILL REMAIN FAIRLY AMPLIFIED THROUGH THE
EXTENDED PORTION OF THE FORECAST... WITH THE MAIN CHANGE LOOKING
TO BE A RETROGRESSION OF THE WESTERN RIDGE AND EASTERN TROUGH.
THIS WON/T CHANGE TOO MUCH WITH RESPECT TO THE CURRENT FORECAST...
EXCEPT A TRANSITION TOWARD SOMEWHAT COOLER TEMPERATURES TOWARD THE
END OF THE PERIOD AS LOWER HEIGHTS WORK INTO THE REGION. SHOULD
CONTINUE TO SEE PERIODIC PCPN CHANCES WITH COOL MID-LEVEL
TEMPERATURES LENDING THEMSELVES TOWARDS INSTABILITY SHRA/TSRA...
PARTICULARLY WITH THE PASSAGE OF SHORTWAVES AND DIURNAL HEATING.

THE SYSTEM WHICH STARTS TO DROP IN LATE SATURDAY AFTERNOON AND
COULD BRING SOME POTENTIAL FOR STRONGER STORMS... WILL CONTINUE TO
PUSH EAST ACROSS THE AREA SATURDAY NIGHT INTO SUNDAY. AT THIS
POINT... THIS IS THE MOST COHERENT FEATURE IN THE EXTENDED
PERIOD... AND INCREASED POPS ACROSS THE AREA LATER SATURDAY NIGHT
INTO SUNDAY AS IT MOVES THROUGH THE AREA. KEPT SOME LOW POPS IN
PLACE ON MONDAY ACROSS THE EAST... WHERE BETTER LAPSE RATES AND
CYCLONIC BOUNDARY LAYER FLOW WILL LINGER. OTHERWISE... NEXT CHANCE
FOR MORE WIDESPREAD PCPN LOOKS TO BE DURING THE LATE WEDNESDAY AND
THURSDAY TIME FRAME AS A DECENT SURFACE LOW MOVES EAST ALONG THE
CANADIAN BORDER AND DRAGS A FRONT THROUGH THE AREA. THE GFS AND
ECMWF ARE IN DECENT AGREEMENT ON THE TIMING AND STRENGTH OF THIS
FEATURE... ALTHOUGH THERE ARE SUFFICIENT DIFFERENCES TO CAP THINGS
AT CHANCE POPS AT THIS POINT. PRIOR TO THAT... CHANCES FOR PCPN
WILL MAINLY BE TIED TO DIURNAL INSTABILITY ALTHOUGH THE GFS DOES
HINT AT THE POSSIBILITY OF SOME HEAVIER PCPN IN THE SOUTHWEST
TUESDAY INTO TUESDAY EVENING AS IT HAS THE BAROCLINIC ZONE
LINGERING CLOSER TO THE REGION THAN THE ECMWF. CYCLONIC FLOW AND A
GOOD MID-LEVEL COLD POOL LOOK TO PUSH INTO THE AREA ON FRIDAY...
WHICH WILL POINT TOWARD A CONTINUED CHANCE FOR PRIMARILY DIURNALLY
DRIVEN SHRA/TSRA.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SATURDAY NIGHT)
ISSUED AT 1100 PM CDT FRI JUN 26 2015

SHRA/TSRA HAVE ENDED AT THE TAF SITES FOR THE OVERNIGHT HOURS. THE
CONCERN NOW TURNS TO FOG POTENTIAL DUE TO THE LINGER RAIN IN THE
EVENING...ESPECIALLY ACROSS WEST CENTRAL WI. THE 00Z NAM NOW SHOWS
THE HYDROLAPSE INCREASING WITH HEIGHT FOR KEAU. THEREFORE...
MENTIONED MVFR BR FROM KSTC THROUGH KRNH AND KEAU NEAR DAYBREAK. A
COLD FRONT WILL MOVE INTO WESTERN MN SATURDAY NIGHT. A BROKEN
LINE OF TSRA MAY REACH KAXN BY 02Z...AND THE TWIN CITIES SHORTLY
AFTER 06Z. CONFIDENCE IS HIGH WITH THIS INCOMING SYSTEM AND VCTS
WITH TEMPO SHRA GROUPS WERE USED. LIGHT WINDS OVERNIGHT BECOMING
SW 6-10 KNOTS ON SATURDAY.

KMSP...SMALL POTENTIAL FOR MVFR BR NEAR DAYBREAK. CONFIDENCE WAS
NOT HIGH ENOUGH TO INCLUDE IN TAF. SHRA/TSRA WILL LIKELY MOVE
ACROSS THE AIRFIELD DURING THE EARLY MORNING HOURS ON SUNDAY
(06Z-12Z). VCTS INDICATED ALONG WITH TEMPO MVFR SHRA.

/OUTLOOK FOR KMSP/

SAT NGT...VFR WITH SHRA/TSRA LIKELY. SW WINDS 5 TO 10 KTS.
SUN...VFR WITH SHRA/TSRA EARLY. SW WINDS BCMG NW 5-10 KTS.
MON...VFR WITH -SHRA POSSIBLE. WINDS NNW 5 TO 10 KTS.

&&

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

$$

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


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