Area Forecast Discussion
Issued by NWS Twin Cities, MN

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000
FXUS63 KMPX 160922
AFDMPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
422 AM CDT SAT AUG 16 2014

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 422 AM CDT SAT AUG 16 2014

ALTHOUGH WIDELY SCATTERED IN NATURE...A FEW AFTERNOON SHOWERS AND
THUNDERSTORMS HAVE THE POTENTIAL TO PRODUCE LOCALLY HEAVY RAINFALL
AMOUNTS. EARLY MORNING SURFACE ANALYSIS IDENTIFIED A WEAK COLD
FRONT LOCATED TO THE NORTH ALONG THE INTERNATIONAL BORDER.
MEANWHILE LOW LEVEL MOISTURE CONTINUE TO ENCROACH FROM THE
SOUTH...WITH LOW STRATUS SPILLING UP FROM NORTHERN IA INTO
SOUTHERN MN.

OVER THE NET 12 TO 24 HOURS...THE STRATUS SHOULD MIX OUT WITH
FORECAST SOUNDINGS SHOWING AN UNCAPPED ENVIRONMENT BY DURING THE
AFTERNOON WITH 1000 TO 2000 J/KG OF CAPE. WEAK CONVERGENCE ALONG THE
SAGGING FRONTAL BOUNDARY SHOULD RESULT IN A FEW WIDELY SCATTERED
THUNDERSTORMS ACROSS THE NORTHERN HALF OF THE CWA. THE MAIN CONCERN
WITH THESE STORMS IS THE INCREDIBLY WEAK WIND FIELD THROUGHOUT THE
TROPOPAUSE. THE BUFKIT HEAVY PRECIP PARAMETER SHOWS AROUND 2-5KTS
FOR THE MEAN WIND...LOW LEVEL JET...AND MESOBETA ELEMENTS. THIS
SHOULD LEAD TO VERY SLOW MOVING...IF NOT STATIONARY THUNDERSTORMS
WHICH WILL BE CAPABLE OF PRODUCING A QUICK 1-3...WITH POSSIBLE 4
INCHES OF RAIN OVER VERY SMALL AREAS. THIS COULD LEAD TO LOCALIZED
FLOODING...BUT AGAIN THE COVERAGE WILL BE SCARCE SO NOT ANTICIPATING
WIDESPREAD FLOODING PROBLEMS. HIRES MODELS SUPPORT THE LIMITED
COVERAGE SO DID NOT RAISE POPS MUCH FROM THE PREVIOUS FORECAST...
HOWEVER DID INCLUDE THE HEAVY RAIN MENTION IN THE WEATHER GRIDS
FOR ANY STORMS THAT DO MANAGE TO DEVELOP.

.LONG TERM...(SUNDAY THROUGH FRIDAY)
ISSUED AT 422 AM CDT SAT AUG 16 2014

MAIN ISSUES FOR THE LONG TERM DEAL WITH SHORT WAVE DROPPING OUT OF
THE WNW SUNDAY INTO MONDAY...AND PROBABLE DEVELOPMENT OF WESTERN
TROUGH DURING THE MIDDLE TO LATTER PORTION OF NEXT WEEK.

UPPER LEVEL LOW NOW SPINNING ALONG THE IDAHO/BC BORDER. BEING
DISPLACED FROM THE FASTER FLOW NEAR 60 DEGREES NORTH IN WESTERN
CANADA... SAID UPPER LOW WILL TAKE ITS TIME GETTING HERE. LOW
MOVES ENE INTO SOUTHERN SASKATCHEWAN THEN ESE INTO NRN MN MONDAY
EVENING. NW/SE ORIENTED LOBE OF ENERGY IS FLAGGED BY ECMWF AND
GFS MOVING INTO WC/SW MN SUNDAY...THEN ACROSS MOST OF OUR AREA
SUNDAY NIGHT. LOW POPS SUNDAY INTO SUNDAY EVENING WILL BE LARGELY
DUE TO THE SURFACE HIGH TO THE NORTH OF LAKE SUPERIOR KEEPING SOMEWHAT
DRY EASTERLY FLOW ACROSS CENTRAL AND EAST CENTRAL MN INTO WISC.
BUT THIS SHOULD SATURATE QUICKLY AS SHORT WAVE ARRIVES. THERE LOOKS TO BE
PLENTY OF MOISTURE AND PRECIPITABLE WATER VALUES SHOULD BE IN THE
1.5 TO 1.7 INCH RANGE ACROSS MUCH OF THE AREA SUNDAY AND MONDAY.
WINDS WILL STILL BE RELATIVELY WEAK ALOFT LEADING TO POCKETS OF
HEAVY RAIN. MAIN ENERGY WITH SHORT WAVE FINALLY DEPARTS TUESDAY RESULTING
IN TUESDAY NIGHT AND WEDNESDAY BEING LARGELY DRY. CANNOT
COMPLETELY ELIMINATE POPS AS THERE WILL STILL BE PLENTY OF
RESIDUAL MOISTURE AND SOME INSTABILITY DESPITER WEAK RIDGING.

MODELS ARE STILL SHOWING THE OVERALL TREND OF A LARGE TROUGH
DEVELOPING IN THE WEST DURING THE MIDDLE PART OF NEXT WEEK. SOME
MAJOR DIFFERENCES STILL INCLUDE EXTENT OF CUTOFF LOW OFF
CALIFORNIA...AND IN THE STRENGTH OF UPPER RIDGE EXTENDING
NORTHWARD TOWARD MN/WI FROM THE DEEP SOUTH. THE GFS WOULD SUGGEST
THE WARMEST TEMPS BUT EVEN THE ECMWF IS TRENDING TOWARD WARMER AND
MORE HUMID THAN ITS PERVIOUS VERSIONS. BROAD SW UPPER FLOW OVER
THE AREA WILL MEAN HIGHER CHANCES OF STORMS LATE NEXT WEEK.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SATURDAY NIGHT)
ISSUED AT 1104 PM CDT FRI AUG 15 2014

CONFIDENCE REMAINS PRETTY HIGH ON LOW MVFR/IFR CEILINGS AND
VISIBILITIES OVERNIGHT AND EARLY SATURDAY MORNING AT THE TAF
SITES. TEMP/DEW POINT SPREADS ARE ALREADY QUITE CLOSE AT THE MN
TAF SITES BUT THERE HAS ALSO BEEN SOME CEILINGS FROM 040 TO 090
SPROUT ACROSS WEST CENTRAL MN IN THE PAST TWO HOURS. IT REMAINS
CLEAR ACROSS SOUTHERN MN AND WEST CENTRAL WI. CEILINGS ARE
DETERIORATING ACROSS NORTHERN IA WITH SOME INDICATION OF THE
STRATUS BUILDING NORTHWARD. HENCE...THE SOUTHWEST AND SOUTH
CENTRAL AREAS OF MN WILL LIKELY DEVELOP WIDESPREAD CEILINGS AT OR
BELOW 010 IN THE NEXT FEW HOURS. SHORT TERM SOLUTIONS SHOW THIS
TRYING TO ADVECT INTO THE TWIN CITIES AND WEST CENTRAL WI BEFORE
DAYBREAK. THEREFORE...PRETTY MUCH KEPT THE LOW CEILING FORECASTS
IN PLACE WITH A LITTLE UPWARD ADJUSTMENT TO THE VISIBILITIES
ACROSS CENTRAL MN WITH CEILINGS BEING MORE DOMINATE. ANOTHER
CONCERN IS THE SHRA/TSRA CHANCES LATE SATURDAY AFTERNOON/EVENING.
NAM FORECAST SOUNDINGS REMAIN VERY MOIST ALONG THE COLD FRONT
ALONG WITH LIGHT WINDS IN THE VERTICAL. CONVECTION THAT DOES DEVELOP
WILL BE SLOW MOVING AND MAY PRODUCE TORRENTIAL DOWNPOURS.
CONSENSUS IS NOT VERY GOOD AMONG THE WRF MEMBERS AT THIS TIME WITH
VCSH INDICATED AT THIS TIME. LIGHT SOUTH WINDS OVERNIGHT. LIGHT
AND VARIABLE WINDS SATURDAY MORNING BECOMING NORTHEAST DURING THE
AFTERNOON AND EVENING.

KMSP...STRATUS WILL ARRIVE FROM THE SOUTH BEFORE DAYBREAK AND LAST
INTO THE MID MORNING HOURS. SCT-BKN VFR CONDITIONS IN THE
AFTERNOON WITH SHRA/TSRA CHANCES DURING THE EVENING...ALTHOUGH
CONFIDENCE IN THE PRECIP CHANCES IN THE EVENING IS LOW.

/OUTLOOK FOR KMSP/

SUN...VFR. WIND E 5-10 KTS.
MON...VFR/MVFR WITH TSRA LIKELY AFTN/NIGHT. WINDS S 5-10 KTS.
TUE...VFR/MVFR WITH TSRA POSSIBLE. WIND NW 5-10 KTS.


&&

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

$$

SHORT TERM...JRB
LONG TERM...TDK
AVIATION...RAH





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