000
FXUS63 KMPX 201142
AFDMPX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
542 AM CST THU NOV 20 2008
.UPDATE...
UPDATED FOR AVIATION DISCUSSION BELOW.
&&
.DISCUSSION...
/ISSUED 239 AM CST THU NOV 20 2008/
THE CHALLENGES WITH THE FORECAST ARE TEMPS TODAY AND TONIGHT IN
THIS COLD PATTERN...THEN MINOR SNOW CHANCES ON FRI NIGHT AND AGAIN
DURING THE END OF THE WEEKEND.
GOES WV LOOP AND THE LAST EVE 00Z RAOBS DEPICTING SHORT WAVE IN NW
FLOW MOVING ACROSS ND AT THE LEADING EDGE OF MUCH COLDER MID-LEVEL
TEMPS /-34C H5 TEMP AT CYQD/. ND AND ABR 88DS HAVE INDICATED
NUMEROUS ECHOES WITH LIGHT SNOW SHOWERS BEING OBSERVED ALONG
FORWARD FLANK OF THIS WAVE. RUC MID-LEVEL LAPSE RATES AND
ASSOCIATED TOTAL TOTAL INDICES ALONG WITH MID-LEVEL Q-VECTOR
CONVERGENCE LINE UP WELL WITH THIS AREA. THIS WILL TRANSVERSE
ACROSS THE SOUTHWEST PORTION OF THE FORECAST AREA THIS MORNING.
WITH MOST ND SITES HAVING RECORDED ONLY A TRACE LAST EVE AND THIS
MORNING...HAVE CONTINUED WITH ONLY FLURRIES IN THE GRIDS. WITH THE
LOWER TO MID TROP TEMPS CONTINUING TO COOL ACROSS THE
AREA...BROKEN STRATOCU IS EXPECTED TO FILL IN ANY BREAKS IN CLOUDS
ELSEWHERE ACROSS THE AREA. WITH THAT...SCATTERED FLURRIES STILL
EXPECTED THIS LATE MORNING AND AFTERNOON ELSEWHERE. WITH SECONDARY
SFC COLD FRONT MOVING SOUTH THROUGH THE AREA THIS MORNING...BL
COLD AIR ADVECTION IS PREDICTED. SO HAVE TEMPS NEARLY STEADY OR
SLIGHTLY FALLING THROUGH THE MORNING...WITH A SLIGHT CLIMB DURING
THE EARLY AFTN. WINDS TO STILL BE BREEZY AT TIMES TODAY AS
PRESSURE GRADIENT FORCE WILL BE STRONG WITH ARCTIC HIGH BUILDING
SOUTHEASTWARD.
GOING INTO TONIGHT...TEMPS SHOULD BE IN THE UPPER TEENS TO LOWER
20S NEAR SUNSET...ALLOWING FOR A STARTING POINT NEAR THE AVERAGE
MINS FOR THIS TIME OF YEAR. HIGHEST CURRENT SFC PRESSURE UNDER
ARCTIC HIGH IN SASKATCHEWAN IS AN IMPRESSIVE 1048 MB. THIS IS
EXPECTED TO MODERATE SOMEWHAT BY TONIGHT...BUT BY OVERNIGHT
PRESSURES OF OVER 1040 MB EXPECTED INTO WRN CWA. THE WINDS SHOULD
COME DOWN QUICKLY IN WRN MN THIS EVE...WHICH WITH CLEARING SKIES
SHOULD ALLOW FOR MAXIMUM RADIATIONAL COOLING. H8 TEMPS OVER THE
REGION TONIGHT TO BE IN THE -10C TO -16C RANGE. DESPITE NO SNOW
ON THE GROUND...GIVEN THOSE TEMP AND MSLP PROJECTIONS...SOME 2F
TO 5F MIN TEMPS FRI MORNING ARE VERY POSSIBLE IN WRN MN.
CLIPPER SYSTEM FOR FRI NIGHT STILL BEING PROGNOSTICATED TO PASS
JUST TO THE SOUTHWEST OF THE FORECAST AREA. BECAUSE THIS IS SO
CLOSE TO THE HEELS OF AN EARLY SEASON ARCTIC AIR MASS...THE ASCENT
AND MOISTURE IN THE DENDRITIC GROWTH AREA IS GREAT...HOWEVER...THE
AREAL COVERAGE AND TIME DURATION OF THIS IS LIMITED AND IS FOCUSED
FROM ERN SD INTO NWRN IA. SHOULD BE A FINE CUTOFF TO THE NORTHEAST
GIVEN PREDICTED BL TDS AND MODEL SOUNDINGS. SO HAVE TIGHTENED
GRADIENT IN POPS OVER MN RIVER VALLEY EVEN MORESO ON FRI NIGHT TO
BETTER DEPICT THIS...BUT ANY MINOR SNOW ACCUMULATIONS ARE LOOKING
MORE UNLIKELY IN OUR FORECAST AREA.
THE NEXT AND POSSIBLY LAST SYSTEM IN NW FLOW TO MOVE DOWN OVER
THE UPPER LAKES ON SUNDAY INTO MONDAY. WARM SECTOR OF THIS TO
BRING NEAR NORMAL TEMPS FOR SAT AND SUN...WITH HIGHS IN THE 30S TO
NEAR 40F. UPPER LEVEL COLD POCKET AND WRAPAROUND MOISTURE STILL
APPEAR THE BEST SCENARIO FOR PRECIP ON SUNDAY NIGHT. NOTHING
PAINTS TOWARDS ANYTHING GREAT FOR SNOW THOUGH. PRIMARILY NW FLOW
STILL EXPECTED TO PREVAIL TOWARDS THE MIDDLE OF THE WEEK BEFORE A
POSSIBLE CHANGE TO WRLY OR SWRLY FLOW. STILL SOME INCONSISTENCIES
WITH THIS...AND THE 00Z ECMWF KEEPS NORTHWEST FLOW WITH A CLIPPER-
LIKE SYSTEM FOR THANKSGIVING. WE SHALL SEE...BUT DOES LOOK LIKE
WRN U.S. RIDGE SHOULD EVOLVE GRADUALLY EASTWARD INTO DEC.
&&
.AVIATION.../12Z TAF ISSUANCE/
BULK OF MVFR CLOUDS AND LOW END VFR CIGS EXTEND ACROSS FAR SW MN
INTO EC MN AND WISC... WITH RATHER PATCHY MVFR CLOUDS SCATTERED
AROUND NRN MN AND STREAMING SOUTHWARD. RUC SEEMS TO DO THE BEST
JOB IN CAPTURING THIS SCENARIO. LOW LEVEL STREAMLINES ARE STILL
SOMEWHAT CYCLONIC THROUGH MID AFTERNOON IN EASTERN SITES...MAINLY
MSP... EAU AND RNH. THOUGH BEST MOISTURE DROPS INTO SERN MN AFTER
15Z... PROFILES SUGGEST ENOUGH TO MERIT BKN CLOUDS AROUND
3500-4000 WELL INTO THE AFTERNOON. LOW LEVEL LAPSE RATES ARE NOT
THAT EXCITING BUT HIGHER LEVELS ARE MORE UNSTABLE. WILL KEEP SOME
FLURRIES IN MOST TAFS MIDDAY AND EARLY THIS AFTERNOON WITH
REDEVELOPMENT OF BKN SC AFTER A TAD BIT OF HEATING. CLOUDS WILL
DISSIPATE AND WINDS DECREASE THIS EVENING AS SFC RIDGE MOVES IN.
&&
.MPX WATCHES/WARNINGS/ADVISORIES...
MN...NONE.
WI...NONE.
&&
$$
MTF/TDK
