Area Forecast Discussion
Issued by NWS Twin Cities, MN

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000
FXUS63 KMPX 250104 AAB
AFDMPX

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
804 PM CDT THU JUL 24 2014

.UPDATE...
ISSUED AT 804 PM CDT THU JUL 24 2014

ONLY UNTIL RECENTLY HAVE MODELS BEGUN TO LATCH ONTO THE CURRENT
SITUATION. HRRR AND NOW HOPWRF HAVE BEGUN TO CONVERGE TOWARD A
SOLUTION WHICH ALLOWS CONVECTION OVER THE WESTERN DAKOTAS AND
EASTERN MONTANA TO EXPAND EASTWARD RAPIDLY DURING THE LATE EVENING
AND SPILL INTO MINNESOTA OVERNIGHT. THE GLOBAL MODELS THROUGH 18Z
DID NOT HANDLE THIS IDEA WELL...SO WHILE CONFIDENCE HAS BEEN QUITE
LOW IT IS STARTING TO INCREASE. IT REMAINS TO BE SEEN WHETHER THE
00Z GLOBAL MODELS WILL LATCH ONTO THIS SOLUTION...BUT GIVEN THE
RECENT TRENDS IN THE CAMS THERE IS A PRETTY GOOD CHANCE.

STRONG MOISTURE ADVECTION OVER EASTERN SOUTH DAKOTA/NEBRASKA WHERE
PW VALUES ARE 1.5 TO 1.9 INCHES WILL CONTINUE TO IMPROVE OVERNIGHT
AS A 40 TO 50 KT LLJ DEVELOPS. THIS LLJ WILL THEN VEER EASTWARD INTO
SWRN MN OVERNIGHT AND FOCUS THIS MOISTURE TRANSPORT OVER THE MPX
CWA. A STRONGLY TO EXTREMELY UNSTABLE AIRMASS TO THE WEST SHOULD
MAINTAIN THIS DEVELOPING MCS AS IT CONTINUES EAST FOR THE NEXT 12
HOURS. THUS...THE SOLUTIONS KEEPING ACTIVITY CONFINED TO IOWA
/A LA NAM...GFS...AND CMC/ IS LOOKING LESS AND LESS LIKELY. INCREASED
POPS ACROSS CENTRAL MN INTO THE LIKELY RANGE AND THE TIMING WAS
BASED ON THE LATEST HRRR/HOPWRF.

ANY SEVERE THREAT WILL BE DETERMINED BY HOW FAR EAST THE EML AND
ASSOCIATED INSTABILITY CAN PROGRESS. BEST CHANCE FOR ANY SEVERE
WOULD BE ACROSS WRN MN...CLOSEST TO THE EML. LARGE HAIL WOULD BE
THE PRIMARY CONCERN.

&&

.SHORT TERM...(THIS EVENING THROUGH FRIDAY)
ISSUED AT 233 PM CDT THU JUL 24 2014

SHORT TERM CONCERNS REMAIN COVERAGE OF THUNDER OVERNIGHT INTO
FRIDAY.  ALSO...CHANCE OF LARGE HAIL MAINLY LATER TONIGHT INTO SOUTH
CENTRAL MN WITH SOME SEVERE POTENTIAL LINGERING INTO FRIDAY AHEAD OF
FRONT.

UPPER RIDGE IS BEGINNING TO MOVE EAST WITH ONE IMPULSE DROPPING
SOUTHEAST OVER WESTERN MINNESOTA AND THE NEXT WAVE LIFTING INTO
NORTHWEST NODAK AND SOUTHERN MANITOBA. IT APPEARS THE INITIAL WAVE
WILL DROP SOUTHEAST THIS EVENING ALONG THE EASTERN PERIPHERY OF THE
INSTABILITY GRADIENT TO THE WEST AND THE EDGE OF LOW LEVEL WAA/STEEP
MID LEVEL LAPSE RATES. MODELS DIVERGE ON DEVELOPMENT THEREAFTER...
WITH SEVERAL HIRES MODELS INDICATING CANADIAN SYSTEM TAKES OVER AND
DROPS SOUTHEAST OVERNIGHT.  STILL SOME POTENTIAL OF LLJ DRIVING
CONVECTION INTO MAINLY SOUTH CENTRAL MN LATE.  WILL CARRY HIGHER
POPS TO THE SOUTH ONCE AGAIN...IN SPIRIT WITH THE PREVIOUS
FORECAST.  SHOULD SEE SOME QPF MOVE THROUGH THE MOST OF AREA.

FRIDAY STILL SEE SOME POTENTIAL OF ISOLATED/WIDELY SCATTERED
CONVECTION DEVELOPING ALONG THE FRONT AS IT MOVES ACROSS THE EASTERN
PORTION OF THE AREA INTO THE AFTERNOON.  WILL HOLD ONTO SOME LOW END
POPS FOR THIS POTENTIAL.  INSTABILITY ALONG THE FRONT DOES INCREASE
DURING THE DAY BUT LOW LEVEL CONVERGENCE REMAINS WEAK.  MUCH OF THE
HIGH END FORCING IS DRIVEN EAST DURING THE MORNING AS WELL.
TEMPERATURES SHOULD WARM INTO THE MID 80S TO THE SOUTHWEST WITH MIX
WITH THE WEAK FRONT AND UPPER 70S/LOWER 80S ELSEWHERE.

.LONG TERM...(FRIDAY NIGHT THROUGH THURSDAY)
ISSUED AT 233 PM CDT THU JUL 24 2014

MAIN CONCERN IN THE EXTENDED PERIOD IS WHETHER SHRA/TSRA DEVELOP
FURTHER SOUTHWARD ACROSS MN THAN EXPECTED FOR LATE SAT AFTN/EARLY
SUNDAY AS A STRONG...AND UNUSUAL UPPER LOW FOR THIS TIME OF YEAR
MOVES EAST-SE ACROSS THE NORTHERN PLAINS...AND INTO THE WESTERN
GREAT LAKES BY SUNDAY. WILL FOLLOW PREVIOUS FORECAST WITH THE MAIN
AREA OF SHRA ACROSS CENTRAL MN/EC MN AND WC WI WHERE BOTH UPPER
LEVEL ENERGY AND HIGHER RH FIELDS ARE EVIDENT. K-INDEX AND 85H
SHOWALTER INDEX FIELDS INDICATED MAINLY SHRA WITH SOME EMBEDDED
TSRA FOR THE TYPICAL DIURNAL TIME FRAME. SUNDAY MORNING/AFTN WILL
LIKELY BE BREEZY AS THE SFC LOW DEEPENS AS IT MOVES SE ACROSS THE
WESTERN GREAT LAKES IN RESPONSE TO THE UPPER JET.

NO CHGS IN THE EXTENDED PERIOD BEYOND THIS WEEKEND WITH BOTH THE
EC/GFS ADVERTISING A STRONG UPPER RIDGE BUILDING OFF THE EAST
COAST OF NORTH AMERICA WITH A DEEPENING LONG WAVE TROUGH ACROSS
THE EASTERN 1/3 OF THE CONUS. THIS WILL KEEP OUR REGION COOLER
THAN NORMAL AND MAINLY DRY. ALTHOUGH COOLER TEMPS ARE
EXPECTED...STANDARD ANOMALIES ARE NOT TOO IMPRESSIVE COMPARED TO
THE DEEP SE U.S. WHERE ANOMALIES COULD DROP TO 2-3 BLW NORMAL.
FOR COMPARISON...OUR REGION WILL BE SLIGHTLY COOLER...BUT STILL
NICE FOR LATE JULY/EARLY AUGUST.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z FRIDAY EVENING)
ISSUED AT 630 PM CDT THU JUL 24 2014

MUCH TO CONSIDER FOR THIS TAF ISSUANCE. DECAYING SHOWERS ACROSS
SOUTHERN MN HAVE PRODUCED STRONG WINDS AS RECENTLY AS 23Z AT MSP
AND STP WHERE GUSTS OF 35 TO 41 KTS WERE REPORTED. GUSTINESS WILL
SUBSIDE THIS EVENING AS THE BOUNDARY LAYER STABILIZES SOMEWHAT.
STRONG MOISTURE TRANSPORT OVER THE EASTERN DAKOTAS HAVE PRODUCED
MID LEVEL CLOUDS OVER WRN MN AT TAF ISSUANCE TIME...AND COULD
FOSTER DEVELOPMENT OF SHRA THIS EVENING. OTHER CIGS...THE MVFR
VARIETY...HAVE ALSO DEVELOPED NORTHWEST OF MSP ALONG I-94. THESE
APPEAR TO BE SOMEWHAT TRANSIENT...SO MADE MENTION OF IT FOR THE
FIRST HOUR IN STC AND AXN TAFS. WILL NEED TO WATCH FOR FURTHER
EXPANSION. OVERNIGHT...MODELS ARE ALL AT ODDS WITH EACH OTHER WITH
THE POTENTIAL NEXT ROUND OF SHRA/TSRA. THE HRRR MODEL SEEMS TO BE
IMPROVING ITS HANDLE ON CURRENT ACTIVITY OVER IA AND ERN MT...AND
IT SHOWS A BAND OF SHRA/TSRA ARRIVING BETWEEN 06-07Z OVER FAR WRN
MN AND HEADING EAST INTO WRN WI BY 09Z OR 10Z. THIS SEEMS LIKE THE
MOST LIKELY SCENARIO AT THIS POINT...BUT SINCE SO MANY OTHER
MODELS ARE SHOWING LITTLE OR NO ACTIVITY OVERNIGHT WAS ONLY
CONFIDENT ENOUGH TO MENTION A PROB30 ATTM.

KMSP...THE GUSTS HAVE CEASED FOLLOWING THE UNEXPECTED 41 KT GUST
AT 23Z. MOSTLY CLEAR CONDITIONS ARE ANTICIPATED FOR THE REMAINDER
OF THE EVENING...ALTHOUGH THE MVFR CIGS TO THE NORTHWEST ARE A
LITTLE CLOSE TO COMPLETELY IGNORE THE POSSIBILITY OF BRIEF MVFR
CONDITIONS IN THE NEXT COUPLE HOURS. AS MENTIONED IN THE GENERAL
DISCUSSION...CONFIDENCE IS LOW OVERNIGHT FOR THE NEXT ROUND OF
SHRA/TSRA SO KEPT THE TAF AT PROB30. COME THE 03Z AMD...SHOULD
HAVE A BETTER HANDLE ON THE OVERNIGHT FORECAST AND BE ABLE TO
REMOVE COMPLETELY OR REINTRODUCE PREVAILING.

/OUTLOOK FOR KMSP/
SAT...VFR. WINDS WSW AT 5-10KTS.
SUN...VFR. CHANCE SHRA/MVFR CIGS. WINDS NW AT 10-15 KTS.
MON...VFR. WINDS N 5 KT.


&&

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

$$

UPDATE...BORGHOFF
SHORT TERM...DWE
LONG TERM...JLT
AVIATION...BORGHOFF





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