458 
FXUS63 KMPX 190002
AFDMPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
702 PM CDT THU MAR 18 2010

.UPDATE...

00Z AVIATION DISCUSSION ADDED BELOW.

&&

.DISCUSSION...
THE WEATHER CHALLENGES IN THE FORECAST ARE PRECIPITATION CHANCES
ON FRIDAY AND QUANTIFYING THE DEGREE OF AND LONGEVITY OF THE 
UPCOMING COOL DOWN.

THE GOES WATER VAPOR LOOP THIS AFTERNOON REVEALS A WELL-DEFINED
DISTURBANCE MOVING EAST ACROSS LAKE WINNIPEG...WITH THE SURFACE
OBSERVATIONS INDICATING A TRAILING COLD FRONT SOUTHWEST ACROSS
NORTH DAKOTA WHICH IS PUSHING SOUTHEAST. SOLID SURFACE PRESSURE
RISES ALONG WITH AIR TEMPERATURES IN THE 20S ARE SEEN BEHIND THIS
FRONT. PARALLEL MID-LEVEL MOIST FLOW AHEAD OF THE TROUGH HAS BEEN
SEEN ON SATELLITE AND THE RADAR MOSAIC THROUGH THE DAY IN SD AND NE.
OCCASIONAL SPRINKLES HAVE BEEN OBSERVED AND FEEL COMFORTABLE WITH
MENTION OF THAT IN WESTERN AND SOUTHWESTERN MN TONIGHT. THE
SURFACE COLD FRONT WILL MOVE THROUGH THE FORECAST AREA OVERNIGHT.
THIS WILL SWING WINDS TO THE NORTHWEST AND DROP TEMPERATURES. HAVE
ADJUSTED THE NIGHTTIME HOURLY TEMPERATURE TREND TO ACCOUNT FOR
THIS.

THE MODELS HAVE CONSISTENTLY TRENDED SOUTH WITH THE DEVELOPING
MID-LEVEL WAVE ALONG THE BAROCLINIC ZONE. THIS HAS CONTINUED INTO
TODAY. SOUTHERN MN WILL REMAIN UNDER FAVORABLE UPPER ASCENT...BUT
THE LOW-LEVEL DRY AND COOL AIR ADVECTION UNDERCUTTING THIS SUPPORT
AND MID-LEVEL MOISTURE WARRANTS ONLY A CHANCE OF LIGHT
PRECIPITATION OVER SOUTH CENTRAL MN...WITH BETTER SUPPORT FURTHER
SOUTH IN IA. THE COLUMN IS COOL ENOUGH TO PRIMARILY SUPPORT LIGHT
SNOW ACROSS THE INTERSTATE 90 CORRIDOR WHERE PRECIPITATION IS ABLE
TO FALL...ESPECIALLY BY LATER AFTERNOON.

THE COOLER AIR WILL REINFORCE ITSELF THROUGH FRIDAY. SURFACE
TEMPERATURES ON FRIDAY WILL BE 20 TO 25 DEGREES COOLER ON FRIDAY
AFTERNOON THAN THIS AFTERNOON...WITH CLOUDS HELPING AS WELL.
SATURDAY SHOULD SEE SUNSHINE BY AFTERNOON AND LIKELY AGAIN ON
SUNDAY. SIMILAR TO THE PREVIOUS FORECAST SHIFT...THE MODELS
CONTINUE TO TREND NORTH WITH THE POLAR STREAM AND ACTIVITY ALONG
IT. WITH WESTERLY FLOW AND RIDGING OVER THE AREA...CONTINUE THE
TREND TO INCREASE TEMPERATURES ON SUNDAY INTO MONDAY. THE FLOW
REMAINS SOMEWHAT SPLIT NEXT WEEK...WITH THE UPPER MIDWEST
PRIMARILY UNDER WEST TO WEST NORTHWEST FLOW. THE GFS AND ECMWF
HAVE COME MORE INTO ALIGNMENT WITH A SYSTEM IN THIS SPLIT FLOW
DURING THE TUESDAY TO TUESDAY NIGHT PERIOD...ALTHOUGH ITS IMPACT
APPEARS TO PRESENTLY BE MINIMAL. TEMPERATURES DURING THE MID TO
LATTER PART OF NEXT WEEK SHOULD BE SOMEWHAT FLAT-LINE AND NEAR
NORMAL.

HYDROLOGY...
MOST POINTS ALONG AREA RIVERS CONTINUE TO GRADUALLY RISE. SNOW
ACROSS WEST CENTRAL AND FAR SOUTHWESTERN MN HAS BEEN DEPLETED TO
MAINLY DITCHES FROM REPORTS RECEIVED...SO LARGE SCALE MELT OVER
INFLOW BASINS APPEARS PRIMARILY DONE. NIGHTTIME TEMPERATURES WILL
DROP BELOW FREEZING ACROSS THE HYDROLOGIC SERVICE AREA ON FRIDAY
THROUGH SUNDAY NIGHTS. THE COOLEST TEMPERATURES...TO NEAR THE
UPPER TEENS ON SATURDAY AND SUNDAY NIGHTS...ARE FORECAST OVER
SOUTHERN AND SOUTHWEST MN. AT LEAST SOME MINIMAL REFREEZING IS
LIKELY.

&&

.AVIATION.../00Z TAF ISSUANCE/ 

COUPLE FEATURES OF INTEREST THIS EVENING. FIRST IS BAND OF MID
LEVEL MOISTURE AND WEAK WARM ADVECTION STRETCHING FROM SODAK INTO
CENTRAL MN AND A COLD FRONT THAT IS QUICKLY DROPPING SOUTH THROUGH
NODAK AND NW MN. SEEING LOTS OF RADAR RETURNS IN CLOUD COVER...BUT
DRY LOW LEVELS MEANS MOST OF THIS IS VIRGA. SEEING SPOTTY RAIN
REPORTS WITH THIS OUT WEST...BUT FEEL THIS ACTIVITY CAN BE COVERED
JUST FINE WITH VCSH...AND HAVE DONE THIS AT MN TERMINALS. WITH
THE FRONT...SEEING GUSTY NW WINDS BEHIND THIS...WHICH WILL BE
WORKING INTO ALL TAF SITES BY THE MORNING...WITH GUSTS INTO THE 20
TO 25 KT RANGE POSSIBLE AT MN TAFS DURING THE DAY SAT. OTHER ISSUE
WITH THE COLD FRONT IS LARGE BANK OF MVFR CIGS IN COLD ADVECTION
BEHIND IT. SEEING RATHER EXPANSIVE CIGS IN THE 025 TO 030 RANGE
ALONG THE INTL BORDER AND EXPECT THESE TO MOVE FROM NW TO SE
ACROSS THE AREA AFTER 06Z. CIGS WILL IMPROVE BACK TO VFR IN THE
AFTERNOON...WITH RAPID CLEARING HAPPENING SHORTLY AFTER 00Z
SUNDAY.

MSP...HAVE BEEN SEEING ENOUGH RA REPORTS TO THE NW TO INCLUDE
MENTION OF VCSH FROM 4Z TO 9Z...WHEN BEST FORCING WILL BE OVHD.
AFTER THAT...GIVEN EXTENT OF HIGH END MVFR CIGS TO THE
NORTH...FAIRLY CONFIDENT IN MVFR CIGS DROPPING DOWN TOWARD THE O25
LEVEL OVERNIGHT AND STAYING THERE INTO THE AFTERNOON. 

&&

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

$$

MTF/MPG