Area Forecast Discussion
Issued by NWS Twin Cities, MN

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000
FXUS63 KMPX 041140
AFDMPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
640 AM CDT TUE AUG 4 2015

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 400 AM CDT TUE AUG 4 2015

TODAY AND TONIGHT...SFC ANALYSIS SHOWS THE CENTER OF A LARGE NW-SE
ORIENTED HIGH PRES AIRMASS SITTING OVER THE UPR MISS RIVER
VALLEY THIS MRNG UNDERNEATH PRONOUNCED NW FLOW ALOFT. THIS IS
KEEPING COOL/DRY AIR OVER THE MPX CWFA THIS MRNG WITH BARELY ANY
CLOUDS IN SIGHT OR PRESENT ON IR IMAGERY. TEMPS HAVE DROPPED INTO
THE 50S CWFA- WIDE /OUTSIDE OF THE TWIN CITIES METRO/ WITH EVEN A
FEW SPORADIC READINGS IN THE 40S. PLENTY OF SUNSHINE IS EXPECTED
TDA AS HIGH PRES EXITS TO THE SE. HOWEVER...H5 HEIGHTS WILL RISE
SLIGHTLY FROM THE W WHICH MEANS TEMPS WILL CONTINUE TO RUN WARM.
HIGHS WILL RANGE FROM THE MID 70S IN WRN WI TO THE LWR 80S IN WRN
MN. MOCLR SKIES WILL CONTINUE THRU THE EVE HRS THEN CLOUDS INCRS
SLIGHTLY OVERNIGHT IN ADVANCE ON AN APCHG WMFNT AND A FLATTENING
RIDGE ALOFT. ISENTROPIC LIFT ALONG WITH DEEPER
MOISTURE...ASSOCIATED WITH THE WMFNT AND A CAPABLE COMBINATION IN
ORDER TO PRODUCE RAIN SHOWERS...WILL REMAIN OFF TO THE SW THRU
TNGT SO HAVE KEPT THE CWFA DRY THRU TNGT. HOWEVER...THE INCRS IN
CLOUDS PLUS A MORE WLY RATHER THAN NWLY FLOW ALOFT MEANS TEMPS
WILL BE WARMER EARLY WED MRNG THAN THIS MRNG. LOWS EARLY TUE MRNG
WILL RUN 50-60 DEGREES.

.LONG TERM...(WEDNESDAY THROUGH MONDAY)
ISSUED AT 400 AM CDT TUE AUG 4 2015

THE GUIDANCE GENERALLY AGREES THAT THE LONGWAVE TROUGH AND UPPER
LOW OVER EASTERN NORTH AMERICA WILL CONTINUE TO SHIFT EAST THROUGH
THE WEEKEND. WITH THIS TRANSITION...WE`LL BREAK OUT OF THE
STEADY NORTHWEST FLOW BEGINNING TOMORROW. THE PATTERN BECOMES A
BIT COMPLEX STARTING TOMORROW NIGHT.

THE FIRST SHORTWAVE IN A SERIES OF POTENTIAL PRECIP MAKERS WILL
PUSH THROUGH THE UPPER MIDWEST FROM TOMORROW NIGHT INTO THURSDAY
MORNING. THE MAIN CHANGE WITH THIS WAVE WAS TO SHIFT THE
FORCING/SATURATION FURTHER NORTH...WITH DRIER AIR REACHING
SOUTHERN MN. SO...INCREASED POPS IN NORTH CENTRAL MN AS THE
GFS/EC/NAM/CANADIAN ALL SHOWED BETTER AGREEMENT ON THIS NORTHERLY
TRACK. DECREASED POPS AND REMOVED ALL MENTION OF PRECIP ACROSS FAR
SOUTHERN MN FOR THIS PERIOD.

ANOTHER...MORE ENERGETIC WAVE IS FORECAST TO QUICKLY FILL IN
THURSDAY AFTERNOON AND NIGHT...AND MOVE ACROSS THE FA THROUGH
FRIDAY. THE DETERMINISTIC GUIDANCE SHOWED IMPROVED AGREEMENT ON
THE TIMING AND STRENGTH OF THIS WAVE...EVEN MORE SO THAN THE FIRST
WAVE. BY THURSDAY NIGHT...STRONG PV ADVECTION WILL BE PUSHING INTO
WESTERN MN ALONG THE LEADING EDGE OF THIS SHORTWAVE...WITH A WEAK
WEST TO EAST ORIENTED JET STREAK PUSHING THROUGH IOWA...IMPLYING
UPPER LEVEL DIVERGENCE ACROSS SOUTHERN MN. AT THE SURFACE...THE
NAM AND GFS SOLUTIONS SUGGEST A SURFACE LOW WILL PROGRESS EAST
THROUGH SOUTH DAKOTA THROUGH OUR AREA THURSDAY NIGHT THROUGH
FRIDAY...WITH A FRONTAL BOUNDARY DRAPED EAST TO WEST THROUGH MN.
THE EC SUGGESTS THIS POSSIBILITY AS WELL...BUT LIFTS THE FRONT AS
A WARM FRONT INTO NORTHERN MN. THIS SOLUTION IS AN OUTLIER...AS
THE CANADIAN AGREES MORE WITH THE NAM/GFS AT THIS TIME. IF THIS
LOW AND FRONT TRACK DOES COME TO FRUITION...WE`LL HAVE A DECENT
HEAVY RAINFALL SETUP WITH THE FRONT DRAPED ACROSS THE AREA...AND
PRECIPITABLE WATER VALUES INCREASING TO 1.75" OR MORE...BROAD LOW
LEVEL LIFT WITH POSITIVE THETA-E ADVECTION...UPPER LEVEL
SUPPORT...AND MODEST INSTABILITY. WILL NEED TO SEE RUN TO RUN
CONSISTENCY AND EVEN BETTER AGREEMENT BEFORE COMING TOO CONCERNED
ABOUT HEAVY RAINFALL ISSUES...BUT AT THIS POINT WE DID INCREASE
POPS TO THE LOW END LIKELY CATEGORY ACROSS SOUTHERN MN AND WESTERN
WI THURSDAY NIGHT.

AS THAT SECOND WAVE DEPARTS THE AREA FRIDAY...OUR ATTENTION TURNS
TO THE NEXT UPPER LOW WHICH IS EXPECTED TO SLIDE EAST ALONG THE
MN/CANADIAN BORDER SATURDAY. THERE IS ACTUALLY DECENT AGREEMENT
BETWEEN THE EC/GFS FOR BEING 5 DAYS AWAY ON THIS SCENARIO. GIVEN
THESE SOLUTIONS...TRIMMED THE POPS IN EXTREME SOUTHERN MN...BUT
STUCK WITH SLIGHT CHANCE MENTION FOR MOST OF THE AREA INCLUDING
THE TWIN CITIES...AS CONFIDENCE IN THE PLACEMENT/TIMING WITH A
FEATURE LIKE THIS...EMBEDDED IN A COMPLEX FLOW PATTERN...IS
RELATIVELY LOW.

FROM SUNDAY AND BEYOND...THE LONGWAVE RIDGE STILL LOOKS TO BUILD
IN...INCREASING HEAT AND HUMIDITY FOR NEXT WEEK.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z WEDNESDAY MORNING)
ISSUED AT 632 AM CDT TUE AUG 4 2015

VFR CONDS FOR ALL TERMINALS AS HIGH PRESSURE MOVES ATOP THE AREA.
LGT/VRBL WINDS THIS MRNG BECOME WNW 5-10 KT BEFORE GOING LGT/VRBL
AGAIN OVERNIGHT TNGT. SOME MIDLVL FAIR WX CU TO DEVELOP THIS AFTN
BEFORE SKIES GO SKC OVERNIGHT.

KMSP...NO SIGNIFICANT WX IMPACTS EXPECTED.

/OUTLOOK FOR KMSP/
THU...MAINLY VFR. CHC MVFR SHRA/TSRA. WIND SE 5-10 KTS.
FRI...MAINLY VFR. CHC MVFR SHRA/TSRA. WIND N 5-10 KTS.
SAT...MAINLY VFR. SLGT CHC MVFR SHRA/TSRA. WIND W 5-10 KTS.

&&

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

$$

SHORT TERM...JPC
LONG TERM...SPD
AVIATION...JPC


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