Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 181709
AFDMPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
1209 PM CDT FRI JUL 18 2014

.UPDATE...
ISSUED AT 1200 PM CDT FRI JUL 18 2014

UPDATED TO INCLUDE 18Z AVIATION DISCUSSION BELOW.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 408 AM CDT FRI JUL 18 2014

A FAIRLY BENIGN PERIOD IS IN STORE TODAY AND EARLY TONIGHT WITH
SPRAWLING HIGH PRESSURE ENCOMPASSING MUCH OF THE EASTERN HALF OF THE
CONUS. RETURN FLOW WILL BRING INCREASING MOISTURE TODAY...SO
EXPECTING QUITE A BIT OF CU FORMATION ACROSS THE UPPER MIDWEST. NAM
FORECAST SOUNDINGS SHOW NEARLY OVERCAST SKIES...BUT IT HAS BEEN
KNOWN TO HAVE A CLOUDY BIAS. CU RULE FROM THE NAM SEEMS MORE
REASONABLE IN POINTING TOWARD A SCT-BKN SKY FROM LATE MORNING INTO
EARLY EVENING. TODAY WILL BE A TOUCH WARMER THAN YESTERDAY WITH
HIGHS NEAR 80.

THE MAIN FORECAST CONCERN FOR THIS PERIOD WILL BE LATER TONIGHT AS A
COMPACT SYSTEM OVER SASKATCHEWAN PROPAGATES EAST SOUTHEAST ALONG THE
U.S./CANADIAN BORDER. A LINE OF SHOWERS AND THUNDERSTORMS ALONG THE
WEAK COLD FRONT ACCOMPANIES THE SYSTEM THIS MORNING. THIS ACTIVITY
WILL DIMINISH TODAY BEFORE REGENERATING THIS EVENING OVER THE
DAKOTAS....REACH WESTERN MINNESOTA SOMETIME AROUND MIDNIGHT. NOT
OVERLY IMPRESSED WITH THE DYNAMICS OR INSTABILITY SO KEPT POPS IN
THE CHC CATEGORY. HOWEVER...DID INCREASE THEM A BIT OVER THE LAST
FORECAST DUE TO SOMEWHAT GOOD CONSISTENCY AMONG MODELS.

.LONG TERM...(SATURDAY THROUGH THURSDAY)
ISSUED AT 408 AM CDT FRI JUL 18 2014

THE FIRST HALF OF THE LONG TERM WILL FEATURE INCREASING HEAT AND
HUMIDITY WHILE THE SECOND HALF WILL SEE COOLER AND WETTER CONDITIONS.

THE COMPACT UPPER LOW MENTIONED IN THE SHORT TERM WILL BE JUST
NORTH OF THE INTERNATIONAL BORDER SATURDAY MORNING WITH A SHORT
WAVE SOUTH ACROSS WESTERN MN. THE ASCENT FROM THE APPROACHING SHORT
WAVE COUPLED WITH INCREASING LOW LEVEL MOISTURE TRANSPORT SHOULD
YIELD A BROKEN LINE OF SHOWERS AND THUNDERSTORMS MOVING EAST
SOUTHEAST ACROSS CENTRAL INTO SOUTHWEST MN SATURDAY MORNING. THESE
MAY DISSIPATE BEFORE REACHING THE TWIN CITIES LATE IN THE MORNING
BUT SEVERAL OF THE CAMS SHOW MORE ACTIVITY DEVELOPING OVER AND TO
THE SOUTH OF THE TWIN CITIES DURING THE AFTERNOON.

AFTER SATURDAY...THE FORECAST FOR SHOWERS AND THUNDERSTORMS
BECOMES MORE PROBLEMATIC. THERE ARE CERTAINLY MORE MINOR SHORT
WAVES COMING INTO OUR AREA IN THE WNW UPPER FLOW. THE ECMWF AND
GFS BOTH SUGGEST POCKETS OF CONVECTION IN THE FA SATURDAY NIGHT
AND THEN AGAIN SUNDAY AFTERNOON AND NIGHT. TRIED TO MODEL THIS IDEA
IN THE FORECAST. WHILE THIS IS OCCURRING...LOW/MID LEVEL WARMING
CONTINUES TO INCREASE. THIS LEADS TO POTENTIAL HEAT WARNING
CRITERIA ON MONDAY FOR MUCH OF THE MN CWA INCLUDING THE TWIN
CITIES. H85 TEMPERATURES WILL LIKELY REACH 22-24 DEGREES C ON MONDAY
ACROSS THE MN CWA WITH H7 TEMPS NEAR 14 DEG C. BUFKIT PROFILE DATA
SHOWS QUITE A CAP IN PLACE FOR THE AFTERNOON. THE H85 TEMPS ALONE
WOULD INDICATE HIGHS IN THE LOWER TO MIDDLE 90S. THIS WILL BE
COUPLED WITH DEW POINTS IN THE LOWER TO MIDDLE 70S...YIELDING HEAT
INDICES FROM 102 TO 107 DEGREES. COMPLICATING MATTERS FOR THE
HIGHS ON MONDAY WILL BE RESIDUAL CLOUD COVER MONDAY MORNING FROM
NIGHTTIME/EARLY MORNING CONVECTION. IF CONTINUITY CONTINUES WITH
THE HEAT THREAT FOR MONDAY IT/S LIKELY THAT AN EXCESSIVE HEAT
WATCH MAY BE ISSUED ON THIS SHIFT TOMORROW NIGHT.

THE THREAT FOR SHOWERS AND THUNDERSTORMS WILL INCREASE
DRAMATICALLY MONDAY NIGHT AND TUESDAY AS A STRONG SHORT WAVE
BREAKS THROUGH THE RIDGE OVERHEAD. THIS IS A FEATURE SEEN ON BOTH
THE ECMWF AND THE GFS WITH THE EURO MUCH STRONGER. IN FACT...IT
HAS A CLOSED MID/UPPER LEVEL LOW FORMING OVER MN/WI LATE
TUESDAY/EARLY WEDNESDAY. RAINFALL AMOUNTS MAY BECOME EXCESSIVE
DURING THIS PERIOD WITH PRECIPITABLE WATER VALUES PROGGED TO
AROUND 2.25 INCHES WHICH IS NEARLY 200 PERCENT OF NORMAL.
ANOTHER CONCERN WILL BE THE POTENTIAL FOR SEVERE WEATHER
TUESDAY/TUESDAY NIGHT AS A SURFACE WAVE/FRONT MOVES ACROSS THE
CWA. CIPS ANALOGS FOR THIS PERIOD SHOWED A CONSIDERABLE AMOUNT
OVER SEVERE REPORTS ACROSS CENTRAL AND NORTHERN MN AS WELL AS THE
EASTERN DAKOTAS.

FINALLY...A DRIER AND MORE SEASONAL TEMPERATURE PATTERN IS FORECAST
FOR THURSDAY IN THE WAKE OF THE WAVE.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SATURDAY AFTERNOON)
ISSUED AT 1200 PM CDT FRI JUL 18 2014

THINGS STILL LOOK GENERALLY QUIET THROUGH THE FORECAST PERIOD...
ALTHOUGH SLIGHTLY MORE COMPLICATED THAN THE PAST FEW DAYS. FRONTAL
BOUNDARY OVER THE DAKOTAS WILL MOVE EAST THROUGH THE FORECAST AS
ITS ASSOCIATED UPPER LEVEL TROUGH MOVES EAST ACROSS SOUTHERN
CANADA. THE FRONT WILL LOSE ITS IDENTITY AND WASH OUT AS IT
CROSSES MINNESOTA LATE TONIGHT AND SUNDAY. CONVECTION IS EXPECTED
TO FIRE OVER THE DAKOTAS ALONG THE BOUNDARY LATER TODAY... AND
THIS WILL MOVE TOWARD THE AREA TONIGHT. HOWEVER... THE ACTIVITY
WILL LIKELY OUTPACE THE INSTABILITY GRADIENT AND FORCING WILL BE ON
THE DECREASE AS THE FRONT LOSES BAROCLINITY AND THE UPPER WAVE
STAYS WELL TO THE NORTH. SO... ALTHOUGH SOME SHRA/TSRA COULD MAKE
IT INTO THE WESTERN PART OF THE AREA... DO NOT EXPECT MUCH TO HOLD
TOGETHER AS IT MOVES EAST. KEPT PCPN OUT OF ALL TAFS EXCEPT KAXN
GIVEN THESE EXPECTATIONS. WHAT/S LEFT OF THE OLD BOUNDARY WILL
BE NEAR OR A BIT EAST OF I-35 BY SATURDAY AFTERNOON... AND THERE/S
A POSSIBILITY FOR SOME ISO/SCT SHRA/TSRA TO DEVELOP ALONG IT.
HOWEVER... CONFIDENCE IN OCCURRENCE... TIMING... AND LOCATION IS
PRETTY LOW... SO CHOSE NOT TO INCLUDE ANYTHING FOR THE EASTERN
SITES AT THIS POINT.

KMSP...MAIN AREA OF CONCERN IS WHETHER ANY SHRA/TSRA WILL IMPACT
THE AREA... WITH THE TIME FRAME OF POTENTIAL LOOKING TO BE FROM
AROUND 19-22Z SATURDAY. HOWEVER... CONFIDENCE IN OCCURRENCE IS
LOW... WITH THE POSSIBILITY OF EITHER NOTHING DEVELOPING AND/OR IT
OCCURRING EAST OF THE AREA. SO... CHOSE TO LEAVE PCPN OUT OF THE
FORECAST... AND KEEP VFR THROUGHOUT. SOME GUSTS AOA 20KT FROM THE
SOUTH ARE EXPECTED THIS AFTERNOON AS THE GRADIENT TIGHTENS AND WE
MIX MORE DEEPLY.

/OUTLOOK FOR KMSP/
SATURDAY NIGHT. BRIEF MVFR POSSIBLE WITH A CHANCE OF SHRA/TSRA.
SOUTH WIND 5 TO 15 KT.
SUNDAY THROUGH MONDAY. VFR. SOUTH WIND 5 TO 15 KT.
MONDAY NIGHT AND TUESDAY. MVFR POSSIBLE WITH A CHANCE OF
SHRA/TSRA. SOUTH WIND 5 TO 15 KT BECOMING LIGHT AND VARIABLE
TUESDAY.

&&

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

$$

UPDATE...
SHORT TERM...BORGHOFF
LONG TERM...RAH
AVIATION...





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