Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 141750 AAC
AFDMPX

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
ISSUED BY NATIONAL WEATHER SERVICE DULUTH MN
1250 PM CDT TUE APR 14 2015

.UPDATE...
ISSUED AT 1228 PM CDT TUE APR 14 2015

UPDATED AVIATION DISCUSSION FOR 18Z TAF ISSUANCE BELOW.

UPDATE ISSUED AT 1107 AM CDT TUE APR 14 2015

THE FORECAST IS GENERALLY ON TRACK THIS MORNING..AND ONLY VERY
MINOR CHANGES WERE NEEDED. LARGE SCALE TROF MOVING INTO THE
PACIFIC NORTHWEST CONTINUES TO PRODUCE STRONG PRESSURE FALLS ON
THE NORTHERN HIGH PLAINS OF MT/ND/SD..AND THUS THE SURFACE PRESSURE
GRADIENT CONTINUES TO STRENGTHEN BETWEEN THE DAKOTAS AND THE
SURFACE HIGH CENTERED OVER FAR SOUTHERN WI. THIS PROCESS WILL
CONTINUE THROUGH THE AFTERNOON..WITH STRONG AND GUSTY WINDS
DEVELOPING OVER THE WESTERN HALF OF THE CWA..AND IN PARTICULAR FAR
WEST CENTRAL MINNESOTA. THE RED FLAG WARNING LOOKS ON TRACK AND NO
APPRECIABLE CHANGES WERE REQUIRED.

WE MADE SOME SUBTLE CHANGES TO THE VARIOUS SHORT TERM GRIDS TO
REFLECT OBSERVATIONAL TRENDS IN TEMP/DEWPOINT AND WINDS..AND ALSO
TO ACCOUNT FOR THE HIGH LEVEL CIRRUS STREAMING ACROSS THE FAR
SOUTHERN CWA. UPDATES ARE ALREADY AVAILABLE.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 350 AM CDT TUE APR 14 2015

QUIET SHORT TERM FORECAST PERIOD AHEAD...WITH THE EXCEPTION OF
FIRE WEATHER /SEE DISCUSSION BELOW/.

SURFACE HIGH PRESSURE DRIFTS EAST OF THE AREA TODAY WHILE THE
PRESSURE GRADIENT TIGHTENS LOCALLY AS A SURFACE LOW DEEPENS OVER
THE HIGH PLAINS. BY 00Z...850 MB TEMPS CLIMB TO AROUND +10C IN
WEST CENTRAL MN. SOUTHERLY WINDS AROUND 20 MPH LOOK TO PROVIDE
SUFFICIENT MIXING TO YIELD HIGHS IN THE MID TO UPPER 70S ACROSS
WEST CENTRAL MN...WITH UPPER 60S TO LOWER 70S ELSEWHERE.

OTHER THAN A FEW CIRRUS CLOUDS...MOSTLY SUNNY SKIES WILL BE FOUND.
WINDS HOLD AT 5-10 KTS OVERNIGHT. LOWS WILL BE AROUND 10 DEGREES
ABOVE NORMAL...WITH READINGS IN THE LOW/MID 40S.

.LONG TERM...(WEDNESDAY THROUGH MONDAY)
ISSUED AT 350 AM CDT TUE APR 14 2015

A SPLIT FLOW REGIME WILL MAKE FOR A DIFFICULT FORECAST IN THE
EXTENDED PERIOD BASED ON HOW THE SOUTHERN JET INTERACTS WITH A
CUTOFF UPPER LOW THRU THIS WEEKEND. CURRENTLY AN UPPER LOW IS
DRIFTING NORTHEAST ACROSS NORTHERN TEXAS. THE FORECAST CHALLENGE IS
HOW WILL THIS SYSTEM INTERACT WITH A STRONGER SYSTEM MOVING ONSHORE
IN THE WEST. BASED ON MODEL GUIDANCE THIS UPPER LOW WILL SLOWLY MOVE
NORTHEAST ACROSS THE MID SECTION OF THE NATION AND GET ABSORBED INTO
A DEEP CUTOFF LOW DEVELOPING ACROSS THE ROCKIES. ALTHOUGH MOISTURE
WILL INCREASE AS THIS UPPER LOW MOVES INTO OUR REGION BY
WED/THU...THERE REMAINS NO SFC CONVERGENCE TO FOCUS ANY SHOWER
ACTIVITY. THE MEAN SFC FLOW IS MORE DIVERGENCE BASED ON THE
STRENGTHENING RIDGE ACROSS THE GREAT LAKES AND A STRONG LOW
DEVELOPING OVER THE NORTHERN ROCKIES. THERE REMAINS NO EVIDENCE OF A
WAA REGIME AS COOLER TEMPS FROM THE UPPER LOW MOVES INTO THE CENTRAL
PLAINS. NO UPPER JET ENERGY IS ALSO NOTED WHICH COMPLICATES WHY SOME
MODELS ARE DEVELOPING SPOTTY SHRA FROM WEDNESDAY THRU FRIDAY. ONLY
THE TYPICAL DIURNALLY DRIVEN AFTN/EARLY EVENING SHRA IS LIKELY BASED
ON SOME SFC MOISTURE RETURN. HOWEVER...THIS IS NOT OVERWHELMING SO
AM LEANING TOWARD A DRY FORECAST THRU THURSDAY. ONLY LATE THURSDAY
NIGHT/FRIDAY DOES A WEAK SFC FRONT MOVE ACROSS THE AREA...LEADING
TOWARD A BETTER SCENARIO WITH LIFT. WILL KEEP THE ISOLD WORDING FOR
THURSDAY NIGHT/FRIDAY BASED ON THIS ASSESSMENT.

AGAIN...WITH THE SPLIT FLOW REGIME CONTINUING...AND THE MEAN FLOW
ACROSS SOUTHERN CANADA ZONAL...AM LEANING TOWARD A DRY FORECAST THIS
WEEKEND ALSO. NOT UNTIL THERE IS STRONG EVIDENCE OF THE NEXT PATTERN
CHANGE WHERE NORTHWEST FLOW BECOMES MORE DOMINATE...WILL THE
FORECAST BECOME MORE CERTAIN. WITH THIS IN MIND...NEXT WEEK
CONTINUES TO BE COOLER THAN NORMAL WITH THICKNESS VALUES DROPPING
BELOW 520DM. THERE IS EVEN A CHANCE OF SNOW AGAIN EARLY NEXT WEEK
WHICH IS DEPENDENT ON THE EVOLUTION OF A SFC TROUGH MOVING ACROSS
THE ROCKIES AND INTO THE UPPER MIDWEST WITH THIS NORTHWEST FLOW
DEVELOPING.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z WEDNESDAY AFTERNOON)
ISSUED AT 1249 PM CDT TUE APR 14 2015

HIGH CONFIDENCE IN PERSISTENCE OF VFR CONDITIONS THROUGH THIS TAF
PERIOD. GRADUAL INCREASE IN COVERAGE/OPACITY OF CIRRUS CLOUDS IS
EXPECTED THE NEXT 24 HOURS..ALONG WITH THE DEVELOPMENT OF SCT-BKN
CLOUDS FROM 8-12 KFT AFTER 15Z WED AS A WEAK DISTURBANCE MOVES
NORTHWARD ACROSS THE AREA. GUSTY S/SE WINDS /ESP WEST/ WILL WEAKEN
AND BECOME MORE SOUTHEASTERLY 00-02Z TONIGHT WITH LOW LEVEL WIND
SHEAR CONDITIONS DEVELOPING AT KAXN/KRWF BETWEEN ROUGHLY 09-15Z.
SURFACE WINDS SHOULD INCREASE RAPIDLY BETWEEN 14-16Z WED AT ALL
TAF SITES..WITH A FEW GUSTS 20-25 KT.

KMSP...
VFR CONDITIONS EXPECTED TO PERSIST THROUGH THE PERIOD..WITH SCT
MID LEVEL CLOUDS DEVELOPING ON WED. MARGINAL LOW LEVEL WIND SHEAR
CONDITIONS COULD DEVELOP BETWEEN ROUGHLY 09-15Z WED WITH WINDS
2KFT AGL SOUTHEAST AROUND 25 KT.

/OUTLOOK FOR KMSP/
THU...VFR. SW WINDS BECOMING WNW 10 KTS.
FRI...VFR. ISOLD VFR RAIN SHOWERS PSBL. WINDS WNW 10-15 KTS.
SAT...VFR. ESE WINDS 5-10 KTS.

&&

.FIRE WEATHER...
ISSUED AT 350 AM CDT TUE APR 14 2015

THE FIRE WEATHER WATCH HAS BEEN UPGRADED TO A RED FLAG WARNING
FOR WEST CENTRAL MN. WHILE RELATIVE HUMIDITY VALUES DROP BELOW 20
PERCENT AREA-WIDE...WEST CENTRAL MN IS OF HIGHER CONCERN GIVEN
WIND SPEEDS WILL REACH SUSTAINED 20+ MPH AND DUFF/FINE FUEL
MOISTURE CODES AND FIRE WEATHER INDICES ARE IN THE VERY HIGH TO
EXTREME CATEGORIES.

WEDNESDAY IS ALSO BEING MONITORED FOR POTENTIALLY NEEDING A WATCH
AS WELL...ALTHOUGH WINDS AND RELATIVE HUMIDITY VALUES APPEAR MORE
BORDERLINE AT THIS POINT.

&&

.MPX WATCHES/WARNINGS/ADVISORIES...
MN...RED FLAG WARNING UNTIL 8 PM CDT THIS EVENING FOR MNZ047-054>056-
     064-073.

WI...NONE.
&&

$$




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