Area Forecast Discussion
Issued by NWS Twin Cities, MN

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056
FXUS63 KMPX 250838
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
338 AM CDT Tue Apr 25 2017

.SHORT TERM...(Today and tonight)
Issued at 325 AM CDT Tue Apr 25 2017

Today and tonight...Surface analysis early this morning depicts a
low pressure center just to the west of WFO MPX this morning. It
associated warm front extends NE then E into northern WI while a
trailing cold front extends SW across northwest Iowa into eastern
Nebraska. The front then continues W to a stronger and more complex
low developing over the TX/OK panhandles. Scattered rain showers
overnight through east-central Minnesota due to enhanced isentropic
lift have shifted into northeast MN and northwest WI, allowing for a
break before more steady and heavier rains develop later today. The
cold front will have a slow progression eastward today while a
potent longwave trough aloft tightens, deepens and slightly pivots.
These actions will help kick the panhandle low northeast along the
front, allowing for enhanced omega in advanced of the cold front and
also bringing in plenty of additional moisture from the deep south.
Essentially, this entire frontal system will develop over central-
southern MN through central IA which will bring close to 1" of QPF
over the region (with potentially higher amounts) from late this
afternoon through tomorrow morning. Due to the lack of insolation
and fairly benign lapse rates, not looking for much at all in the
way of convection so the prevailing thinking is to have more
stratiform rains with an expected large precipitation shield
developing from south to north over the area. Have maintained pops
increasing to categorical levels for much of the WFO MPX coverage
area late today through tonight. The panhandle low will reach the
IA/MN/WI triple point by daybreak Wednesday morning with the front
just barely out of MN and bisecting WI. Thus, fairly little dry time
is expected this evening through tomorrow morning. The other
function of this system is to maintain the large temperature
difference across the area from west to east. Lows early this
morning are already at an over 20-degree difference from western MN
to western WI. This difference will continue today as temperatures
range from the mid 40s in western MN to the low 60s in eastern MN
with mid (to potentially upper) 60s in western WI. Since cold air
advection will not commence for the entire coverage area until
tomorrow, early Wednesday morning will feature another large
temperature spread with lows in the mid 30s to the lower 50s west to
east.

.LONG TERM...(Wednesday through Monday)
Issued at 325 AM CDT Tue Apr 25 2017

The forecast concerns remain movement of the upper low across the
area Wednesday into Thursday and development of the next trough
over the western conus lifting into the region over the weekend.

Initially the trough is progged to lift northeast through this
period. Significant moisture should lift northeast Wednesday
morning with the first area of lift. What remains will be any
residual moisture Wednesday afternoon into Thursday as the closed
core low lifts slowly northeast. This should provide a very cool
boundary layer across the region by late Wednesday night. Any
remaining precipitation would be a rain and snow ix or plain snow
showers. We do have some wet accumulations progged for the far
northwest - around Alexandria/Staples area - which could see some
accumulation on grassy areas into early Wednesday morning.
Otherwise and mix/change over to snow would occur Wednesday night
into Thursday which would affect mainly the northeast cwa. Any
accumulation would be less than an inch.

The GFS still works another weak wave into the region Friday and
may affect mainly the southern cwa. We will retain the small
chance PoP for that region into Friday night. Then models and in
fair agreement with the next significant storm system to affect
the region over the weekend. Timing would favor later Saturday
night into Sunday night diverge more on the development and
handling the weekend storm system. The ECMWF is slower and more
dynamic/colder with the low. This would likely generate a rain
changing to wet snow scenario over much of the eastern cwa later
Sunday/Sunday night. The latest CIPS analog mean snowfall for that
period favors at least a couple inches of snow across the
northern half of the cwa or central Minnesota into west central
Wisconsin. Stay tuned.

&&

.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 1010 PM CDT Mon Apr 24 2017

Only changes to the 06z taf was to delay the onset of MVFR cigs
across far east central Minnesota, and into west central
Wisconsin until mid/late morning, or Tuesday afternoon. The
remainder of west central/southwest and central Minnesota will
have MVFR/IFR cigs developing overnight, with LIFR cigs likely
near KAXN for a few hrs. The other change to these tafs was to
delay the onset of -SHRA/-RA until mid/late afternoon for most
sites. Only KRWF will have the best chance of -SHRA before 18z,
with most of MPX taf sites having the bulk of the steadier
rainfall after 21z. Once the precipitation begins, expect
cigs/vsbys to lower to IFR/LIFR at times. A cold front has moved
into west central Minnesota late this evening. This front will
move eastward and stall near the Minnesota/Wisconsin border by
morning.

KMSP...

Kept the MVFR cig development close to previous taf with an hour
or two delay. However, once precipitation develops, cigs/vsbys
will drop to IFR conditions by the afternoon, and continue through
the evening. Winds will hold from the south around 8 kts
overnight, then become light and variable through noon before
shifting to the east/northeast by the afternoon and increasing in
speed.

/OUTLOOK FOR KMSP/

Wed...MVFR, IFR possible. -RA likely early, mixed with -sn late.
Winds NE 10-20 kts.

Thu...MVFR, IFR possible. Chc -RA/-SN early.
Winds N 5-15 kt bcmg light & variable.


&&

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

$$

SHORT TERM...JPC
LONG TERM...DWE
AVIATION...JLT



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