Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 271211
AFDMPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
711 AM CDT MON OCT 27 2014

.UPDATE...
ISSUED AT 637 AM CDT MON OCT 27 2014

UPDATED TO INCLUDE 12Z AVIATION DISCUSSION BELOW.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 330 AM CDT MON OCT 27 2014

TODAY-TONIGHT...SFC ANALYSIS THIS MRNG DEPICTS TWO LOW PRES
CENTERS...ONE OVER THE NE/IA BORDER AND A SECOND OVER SRN MANITOBA
PROVINCE. THESE TWO LOW PRES CENTERS ARE LINKED BY A WEAK SFC
FRONTAL BOUNDARY...LIKELY AN OCCLUSION. THAT SAID...WARM AIR
ADVECTION IS CERTAINLY EVIDENT GIVEN THAT TEMPS ACRS MUCH OF THE MPX
CWFA THIS MRNG ARE ABOUT 20-25 DEGREES WARMER THAN 24 HRS PRIOR.
ALOFT...A LONGWAVE TROF CONTINUES TO LUMBER ITS WAY ACRS THE
NRN-CENTRAL ROCKIES INTO THE NRN-CENTRAL PLAINS. THIS TROF WILL
NUDGE BOTH LOW PRES CENTERS EWD TDA...BUT THE TROF WILL BECOME
SHARPER...PIVOT TO A MORE NEUTRAL FROM POSITIVE POSITION...AND ALLOW
FOR THE DEVELOPMENT OF A CUTOFF LOW WITHIN IT. WHILE THESE FEATURES
DEVELOP ALOFT...THE SFC LOWS WILL ATTEMPT TO PHASE TOGETHER AS THEY
SHIFT E BUT THIS PHASING DOES NOT APPEAR TO OCCUR UNTIL THE LOWS
MOVE OVER THE GREAT LAKES...LEAVING THE MPX CWFA SLOTTED TO HAVE
LESSER COVERAGE OF PRECIP. THAT SAID...EFFICIENT LIFT WAS GENERATED
IN WRN WI VIA WEAK BUCKLING OF THE FLOW ALOFT WITH ISENTROPIC LIFT
AHEAD OF THE SRN OF THE TWO LOW PRES CENTERS TO PRODUCE SHOWERS AND
ISOLD TSTMS OVER WRN WI. THIS IS DESPITE DEW POINT DEPRESSIONS OF
20-25 DEGREES. TRANSLATING THAT THINKING TO THE FCST...HAVE
INCREASED POPS IN WRN-CENTRAL MN TDA AS THE LOW PRES CONGLOMERATION
SHIFTS EWD TDA AND THE UPR TROF PIVOTS. LOCAL MPXWRF...HOPWRF...NAM
AND SREF ALL DEPICT A BAND OF RAIN DEVELOPING IN THE ERN DAKOTAS
THAT WILL SPREAD EWD LATE THIS MRNG THRU THIS AFTN IN CONJUNCTION
WITH THE SRN LOW MOVG NWD INTO WI AND THE UPR TROF AXIS SWINGING
THRU. PRECIP COVERAGE WILL STEADILY DIMINISH GOING INTO THIS
EVE...GIVING FURTHER CREDENCE TO THE THINKING OF DIURNALLY DRIVEN
PRECIP FOR TDA. HAVE ONLY CARRIED SLGT CHC POPS FOR TNGT...MAINLY
FOR THE NRN TIERS OF THE CWFA...DUE TO WRAPAROUND MOISTURE FROM THE
DEPARTING LOW PRES CENTERS. AS FOR TEMPS...MILD CONDITIONS WILL
CONTINUE DUE TO THE STRONG CAA HOLDING OFF UNTIL THE EARLY MRNG HRS
ON TUE. WEAK SFC AIR MASS ADVECTION COMBINED WITH CONTINUED SW FLOW
ALOFT TDA WILL MAKE FOR ONE MORE DAY WITH HIGHS GENERALLY FROM THE
UPR 50S TO LWR 60S. THERE IS SOME THINKING THAT FAR SERN PORTIONS OF
THE CWFA COULD SEE HIGHS HITTING THE MID 60S...WHERE WAA WOULD THE
MOST PROLONGED WITH AMPLE SUNSHINE AS CLEARING TAKES PLACE WITH THIS
MORNING/S SHOWERS MOVING AWAY. ON THE FLIP SIDE...HIGHS IN NWRN
PORTIONS OF THE CWFA COULD HOLD IN THE MID 50S SHOULD CLOUD COVER BE
MORE PREVALENT AND LLVL NW FLOW COMMENCES EARLIER. WITH THE UPR TROF
HOLDING OFF TO THE W OVERNIGHT INTO TUE MRNG...STRONGER CAA ALSO
LOOKS TO HOLD OFF SO MIN TEMPS TONIGHT WILL ONLY BE SLIGHTLY COOLER
THAN THIS MRNG...RANGING FROM THE UPR 30S TO LWR 40S.

.LONG TERM...(TUESDAY THROUGH SUNDAY)
ISSUED AT 307 AM CDT MON OCT 27 2014

A STRONG FALL STORM SYSTEM WILL BE NEARLY OVERHEAD TUESDAY MORNING
ACROSS THE UPPER MIDWEST WITH THE LARGE SCALE LIFT NORTH/EAST OF
MPX CWA. WRAP AROUND MOISTURE IS LIKELY DUE TO THE STRENGTH AND
PROXIMITY OF THE UPPER LOW. THE MAIN CONCERNS ARE IN THE DEPTH OF
THE MOISTURE AND HOW FAR SOUTH DOES THE MOISTURE TRAVEL IN MN/WI
BEFORE LIFTING OUT TUESDAY AFTN/EVENING.

MODELS HAVE BEEN CONSISTENT OF THE LOCATION OF THE UPPER LOW.
MODELS ARE ALSO DEPICTING SEVERAL SHRTWV/S /PVA BOOT/ ROTATING
AROUND THIS STORM SYSTEM AS IT SLOWLY LIFTS TO THE EAST-NORTHEAST
ACROSS THE GREAT LAKES AND INTO SOUTHEAST CANADA. THESE SHRTWV/S
AND THE AMOUNT OF AVAILABLE MOISTURE SHOULD ALLOW FOR
ISOLD/SCATTERED SHRA TO DEVELOP...ESPECIALLY NEAR THE CORE OF THE
UPPER LOW. ALTHOUGH THERE COULD BE AREAS OF WIDESPREAD SHRA/S IF
THE DEPTH OF THE MOISTURE IS HIGHER...A LACK OF SFC CONVERGENCE
WITH THE MAIN SFC LOW NORTH OF THE GREAT LAKES AND THE SFC TROUGH
NORTH OF MPX CWA...COVERAGE REMAINS SMALL. THEREFORE...POPS OF
20-40% SEEMS REASONABLE. ANOTHER ASPECT TO THIS STORM SYSTEM IS
THE STRENGTH OF THE CAA AND WIND ENERGY IN THE LOWEST 3K. THERE
SHOULD BE ENOUGH MIXING IN THE BOUNDARY LAYER AND WITH STRONG
CAA...WINDY CONDS ARE LIKELY...ESPECIALLY IN THE TYPICAL AREAS OF
WESTERN AND SOUTHERN MN. AS THIS SYSTEM DEPARTS THE AREA TUESDAY
NIGHT...DRY WX IS FORECAST WED/THU/FRI WITH ONLY A SUBTLE SHRTWV
RIDING SE ALONG THE NW FLOW THURSDAY. A FEW SPRINKLES ARE
POSSIBLE WITH THIS SYSTEM...BUT THE DRY AIR MASS REMAINS
UNFAVORABLE FOR ANY MEASURABLE PRECIPITATION.

THE PROGRESSIVE FLOW IN THE MODELS IS STILL FORECAST TO CONTINUE
IN THE NEXT 7-10 DAYS. THEREFORE...A PERIOD OF BLW NORMAL TEMPS
FROM TUESDAY THRU SATURDAY WILL CHG ONCE AGAIN BY SUNDAY AND EARLY
NEXT WEEK AS AN AMPLIFIED UPPER RIDGE BUILDS ACROSS THE MID SECTION
OF NORTH AMERICA. THICKNESS VALUES ONCE AGAIN RISE SUNDAY WITH
TEMPS REBOUNDING BACK ABV NORMAL. THE STRONG AMPLIFICATION OF THIS
RIDGE ALSO PROVIDES UNCERTAINTY WITH A BLOCKING PATTERN
DEVELOPING. AS SAID BEFORE...MODELS REMAIN PROGRESSIVE SO A
BLOCKING PATTERN IS NOT FORECAST BUT SOMETHING TO PONDER IN THE
EXTENDED PERIOD WITH MODEL TREADS AND THE OVERALL MEAN FLOW.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z TUESDAY MORNING)
ISSUED AT 637 AM CDT MON OCT 27 2014

DISORGANIZED LOW PRES SYSTEM WILL APPROACH FROM THE W THIS
MRNG...ALOWLY MOVG ACROSS MN INTO WI THIS AFTN THRU THIS EVE.
SCATTERED -SHRA WILL DEVELOP OVER WRN BY LATE MRNG...SLOWLY
SPREADING EWD. MODELS DEPICT PLENTY OF DRY AIR IN THE LOWER
LEVELS...MAKING IT DIFFICULT TO SATURATE FOR CLOUD COVER LET ALONE
PRECIP. THEREFORE...HAVE OPTED TO RUN WITH VFR FOR ALL SITES...
EVEN WITH POTENTIAL -SHRA. BEST CHANCES FOR PRECIP LOOK TO BE AT THE
WRN-CENTRAL MN SITES...WITH CHCS DECRG GOING EWD. NOT EVEN SURE
THE WI SITES WILL SEE PRECIP. BKN SKIES WILL REMAIN IN THE WAKE OF
THE PASSAGE OF THIS SYSTEM...WITH WIND SPEEDS PICKING OVERNIGHT
THRU DAYBREAK TUE FOM THE W.

KMSP...VFR THROUGHOUT. BEST CHCS FOR -SHRA LOOK TO OCCUR MID-TO-
LATE AFTN...BUT NOT EXPECTING ANYTHING THAT WOULD REDUCE FLIGHT
CONDITIONS TO LESS THAN VFR.

/OUTLOOK FOR KMSP/
WED...VFR. WINDS W 5-10 KT...BECMG S.
THU...VFR. WINDS N 5-10 KT.
FRI...VFR. WINDS N 6-10 KT...BECMG E.

&&

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

$$

UPDATE...JPC
SHORT TERM...JPC
LONG TERM...JLT
AVIATION...JPC







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