Area Forecast Discussion
Issued by NWS Twin Cities, MN

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000
FXUS63 KMPX 041702
AFDMPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
1202 PM CDT SAT JUL 4 2015

.UPDATED FOR AVIATION DISCUSSION BELOW...

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 324 AM CDT SAT JUL 4 2015

BOUNDARY THAT SLIPPED INTO CENTRAL MN/NW WI LAST NIGHT IS NOW ALL
BUT INDISCERNIBLE...WITH A VERY BAGGY PRESSURE GRADIENT IN PLACE.
THIS BOUNDARY DID HANG UP A BAND OF LOWER 60 DEWPOINTS ACROSS
CENTRAL MN...WHICH IS WHERE FOG HAS BEEN EXPANDING. OF COURSE THIS
AREA ALREADY HAD VIS RESTRICTIONS FRIDAY AFTERNOON IN SMOKE...WHICH
IS CERTAINLY AIDING IN THE POOR VIS ACROSS CENTRAL MN. IN FACT...WE
WERE GETTING REPORTS OF ASH DEPOSITING IN ST. CLOUD YESTERDAY...SO
THE SMOKE IS GIVING US SOME EXTRA CLOUD CONDENSATION NUCLEI IN THE
LOW LEVELS...WHICH IS FURTHER HELPING THE FOG ALONG. MAY TAKE SOME
TIME TO CLEAN UP THE FOG GIVEN THE CONTINUED DENSE SMOKE OVER THE
AREA THAT WILL SLOW DOWN DIURNAL HEATING.

FOR THE REST OF TODAY...FULLY EXPECT DENSE SMOKE TO AGAIN LEAD TO A
HAZY SKY...THE QUESTION REMAINS THOUGH AS TO HOW MUCH SURFACE
VISIBILITIES WILL BE REDUCED. NW SURFACE WINDS THAT BROUGHT SMOKE
INTO CENTRAL MN YESTERDAY HAVE DISAPPEARED...WITH SRLY WINDS SLOWLY
TAKING HOLD DURING THE MORNING...SO DO NOT ANTICIPATE SURFACE BASED
SMOKE TO MAKE IT ANY FARTHER SOUTH THAN IT DID YESTERDAY. CURRENT
THINKING IS THAT FOG IN CENTRAL MN WILL LIFT INTO A REDUCED VIS IN
SMOKE THAT WILL BEGIN TO FINALLY IMPROVE DURING THE AFTERNOON.

FOR PRECIP...HAVE REMOVED ALL OF IT FOR THE SHORT TERM PERIOD.
ALOFT...WE HAVE RIDGING AND AT THE LOW LEVELS WE HAVE LOST ANY
SEMBLANCE OF A FRONT. CAMS HAVE COME IN DRY AS WELL...SO SAW NO
SUPPORT FOR MAINTAINING ANY POPS. THIS AFTERNOON...WE WILL SEE A
SHORTWAVE WORKING ACROSS THE DAKOTAS THAT WILL KICK OF SCATTERED
THUNDERSTORMS BY THE AFTERNOON TO OUR WEST. SOME DETERMINISTIC
GUIDANCE TRIES TO WORK SOME OF THIS INTO WRN MN LATE
TONIGHT...THOUGH IT IS RUNNING INTO SOME PRETTY DRY MID-LEVEL AIR
OVER MN...SO FOLLOWED THE IDEA OF THE CAMS IN KEEPING ANY ACTIVITY
TONIGHT OUT OF THE MPX AREA.

FOR TEMPERATURES...DENSE SMOKE WILL AGAIN HOLD BACK HIGHS A BIT. THE
LAST 3 DAYS...WE HAVE SEEN HIGHS ABOUT 5 DEGS COOLER THAN WHAT OUR
925-850 MB TEMPS WOULD SUGGEST AND EXPECT MORE OF THE SAME TODAY.
BASICALLY FORECAST A CONTINUED SLOW MODERATION IN TEMPERATURES...
WITH HIGHS TODAY FORECAST TO BE 2 TO 4 DEGREES WARMER THAN WHAT WE
SAW FRIDAY...WHICH WAS 2 TO 4 DEGREES WARMER THAN WHAT WAS SEEN ON
THURSDAY.

.LONG TERM...(SUNDAY THROUGH FRIDAY)
ISSUED AT 324 AM CDT SAT JUL 4 2015

CONCERNS IN THE LONG TERM CONTINUE TO BE FROM SUNDAY INTO MONDAY
WHEN A VIGOROUS SHORT WAVE AND SURFACE LOW PRESSURE SYSTEM MOVE
ACROSS THE NORTHERN PLAINS AND UPPER MISSISSIPPI VALLEY REGION.
ALTHOUGH MODEL TRENDS REMAIN CONSISTENT WITH THESE FEATURES...THERE
CONTINUES TO BE A SLIGHT SLOWING ON THE EASTWARD PROGRESSION FROM
RUN TO RUN AS DEEPENING SURFACE LOW PRESSURE MOVES FROM CENTRAL
SOUTH DAKOTA SUNDAY EVENING TO LAKE SUPERIOR BY MONDAY EVENING.
THE THREE MAIN CONCERNS ARE HIGHS ON SUNDAY...THE SEVERE WEATHER
THREAT SUNDAY AFTERNOON/NIGHT AND THE HEAVY RAINFALL POTENTIAL
SUNDAY NIGHT AND MONDAY.

BEGINNING WITH THE FIRST CONCERN...THE FLOW ALOFT SHOULD BE MORE
WESTERLY ON SUNDAY AND PERHAPS EVEN SOUTHWESTERLY LATE IN THE
DAY. THIS SHOULD CLEAR THE AREA OF THE FIRE SMOKE ALLOWING FOR
HIGHS TO BE MORE REPRESENTATIVE OF MIX-DOWN VALUES. A TREND NOTED
IN OUR LOCAL CLIMATE PRODUCTS IS THAT HIGHS HAVE BEEN INCREASING
ABOUT 4 DEGREES PER DAY SINCE JULY 1ST. THIS TRENDS MATCHES NICELY
WITH FORECAST HIGHS IN THE MIDDLE TO UPPER 80S IN SUNDAY...WITH
THE WARMEST READINGS IN WEST CENTRAL MN UNDER THE LOW LEVEL
THERMAL RIDGE.

THE SECOND CONCERN IS THE SEVERE WEATHER RISK SUNDAY AFTERNOON
AND NIGHT. WITH THE CONTINUED SLOWING ON THE EASTWARD MOVEMENT OF
THE FRONTAL BOUNDARY...THE EASTERN PORTION OF SOUTH DAKOTA LOOKS
TO BE AT GREATEST RISK FOR SEVERE STORMS DURING THE LATE
AFTERNOON/EVENING. THIS IS THE AREA WHERE CWASP (CRAVEN-
WIEDENFELD AGGREGATE SEVERE PARAMETER) IS HIGHEST ALONG WITH THE
SREF CALIBRATED SEVERE PROBABILITIES. HENCE...MUCH OF THE DAY WILL
BE DRY IN OUR FA WITH ONLY THE FAR WESTERN AND NORTHERN CWA AT
RISK FOR THUNDERSTORMS LATE IN THE DAY...BUT EVEN THESE AREAS MAY
NOT SEE MUCH UNTIL EVENING. SO THE SLIGHT RISK CONFINED TO OUR
WEST CENTRAL SEEMS OKAY AT THIS POINT WITH THE MAIN THREAT SUNDAY
EVENING.

THE THIRD CONCERN IS THE HEAVY RAINFALL POTENTIAL SUNDAY NIGHT AND
MONDAY AS THE SYSTEM MOVES SLOWLY EASTWARD. THE NAM AND GFS
CONTINUE TO SHOW PW VALUES IN THE 2 TO 2.5 INCH RANGE SPREADING
EASTWARD ACROSS THE FA SUNDAY NIGHT AHEAD OF THE COLD FRONT. THIS
IS IN RECORD TERRITORY FOR EARLY JULY. FOLLOWING THE ECMWF LOW
LEVEL MOISTURE TRANSPORT FIELDS AS WELL AS THE 925-850MB
FRONTOGENESIS AND NEGATIVE FN VECTOR DIVERGENCE...POINTS TO THE
WESTERN HALF OF THE MN CWA AS HAVING THE HIGHEST CHANCE FOR HEAVY
RAIN SUNDAY NIGHT. THE AFOREMENTIONED FIELDS SHIFT EASTWARD ON
MONDAY AND WEAKEN...LESSENING THE RISK FOR HEAVY RAIN...BUT NOT
TOTALLY ELIMINATING IT. QPF GRIDS FOR THE SUNDAY NIGHT/MONDAY
PERIODS WORKED OUT TO A LITTLE OVER 2 INCHES FROM CANBY TO LITTLE
FALLS WITH 1.25 TO 1.5 INCHES FROM THE TWIN CITIES THROUGH WEST
CENTRAL WI. THE LOWEST TOTAL QPF WAS NEAR THE I-90 CORRIDOR WITH
AROUND AN INCH FORECAST. HEAVY RAINFALL WAS INCLUDED IN THE
WEATHER GRIDS WHERE THE POPS WERE CATEGORICAL.

IN THE WAKE OF THIS SYSTEM...HIGH PRESSURE ALONG WITH COOLER
AND LESS HUMID CONDITIONS WILL SPREAD IN FOR MONDAY NIGHT THROUGH
MUCH OF THE WORK WEEK. AN EXCEPTION ON THE PRECIPITATION CHANCES
IS ON THURSDAY WHEN A SMALL THREAT FOR SHOWERS AND THUNDERSTORMS
IS INDICATED BUT NOT SUPPORTED VERY WELL BY THE ECMWF. HIGHS MUCH
OF NEXT WEEK WILL BE IN THE 70S.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SUNDAY AFTERNOON)
ISSUED AT 1210 PM CDT SAT JUL 4 2015

SMOKE REMAINS OVER CENTRAL MN...BEGINNING TO THIN/MIX A BIT TO THE
WEST. MODEL GUIDANCE SUGGESTS THIS WILL MOVE EAST INTO WESTERN WI
BY 00Z SUN. WILL IMPROVE VSBYS OVER CENTRAL MN SITES THIS
AFTERNOON. MAY LINGER THE SMOKE A BIT INTO KRNH...DEPENDING ON
LATE MORNING TREND. OTHERWISE VFR EXPECTED WITH SOME CUMULUS AND
CIRRUS THIS AFTERNOON. SOME SMALL CHANCE OF AN ISOLATED
SHOWER/THUNDER...MAINLY ALONG AND NORTH OF I94 THIS AFTERNOON PER
SOME LATE DETERMISITIC RUNS. HOPWRF DIDNT GENERATE ANYTHING ALONG
THE WEAK BOUNDARY SO WILL LEAVE OUT FOR NOW. WINDS LIGHT SOTUH/SW
OVER MUCH OF THE AREA THIS AFETRNOON/EVENING AND INCREASING INTO
SUNDAY. SHOULD BECOME GUSTY 20-25KTS TO EH WEST BY 18Z SUNDAY.

KMSP...APPEARS THICKEST SMOKE/HZ LAYER MOVING ACROSS THE AREA NOW.
MODEL FORECAST HAS THIS THINNING DURING THE AFERNOON AND MOVING
OUT BY EVENING. WILL TRY AND IMPROVE VSBY THROUGH 00Z SUN. THEN
SOME SMALL CHANCE OF BR DEVELOPING LATE. WILL MENTION ONLY 6SM BR
10Z-13Z FOR NOW...AS A SOTUHERLY WIND IS EXPECTED TO REMAIN.
OTHERWISE...VFR THROUGH THE PERIOD WITH SOEM CUMULUS AND CIRRUS
AT TIMES THROUGH THE AFETRNOON. WINDS SHOULD INCREAS FROM THE
SOUTH SUNDAY AND BECOME GUSTY BY AFTERNOON.

/OUTLOOK FOR KMSP/
SUN NIGHT...VFR. TSRA WITH MVFR/IFR LIKELY LATE. WINDS S 10-15 KTS.
MON...MVFR/IFR WITH TSRA EARLY THEN VFR. WINDS NW 10-15 KTS.
TUE...VFR. WINDS N 5-10 KTS.

&&

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

$$

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



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