Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 172022

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
322 PM CDT Mon Apr 17 2017

.SHORT TERM...(This evening through Tuesday)
Issued at 320 PM CDT Mon Apr 17 2017

It was a fine spring day across the region with a ridge of high
pressure overhead. Relative humidity readings at mid afternoon
were in the 35 to 40 percent range at many locations. The high
will depart off to the east early this evening as low pressure
over eastern Montana and Wyoming advances eastward. Deterministic
solutions are in great agreement with regards to the track of the
low pressure system across northern Minnesota on Tuesday as well
as with the timing on the precipitation. Only minor tweaks were
made to the forecast for tonight and Tuesday. The first was to
boost pops into the categorical range along the core of
precipitation moving through late tonight and early Tuesday due to
high confidence in the model solutions.

Rain amounts will be greatest across northwest Minnesota where up
to an inch of rain is expected. Amounts taper back to around a
half inch around Alexandria and St. Cloud with a quarter inch or
less across southern Minnesota, the Twin Cities and west central
WI. The higher rain amounts to our northwest are tied to
impressive divergence associated with a coupled upper jet along
with a strong mid level PV boot pushing through this area. There
will also be some convection with this system, with the negative
best LI`s from the GFS used for timing in our FA. The best chance
for thunderstorms will be across western Minnesota after midnight.
Severe weather is not expected.

The rain will end from west to east on Tuesday as a cold front
trailing from the low drives through. There will be a tight
pressure gradient associated with the low as southerly winds at 15
to 20 mph to start the day will become SW and then W. Gusts in the
high 20 to low 30 knot range can be expected. This was the second
tweak in the forecast on boosting wind speeds.

It will be mild tonight with lows from the upper 30s in our far
eastern FA to near 50 in west central and south central Minnesota.
Even with the rain early on Tuesday, it will still be a warm day
with highs from the upper 60s from the Twin Cities on east and
south. High will taper back into the middle to upper 50s in
central Minnesota.

.LONG TERM...(Tuesday night through Monday)
Issued at 320 PM CDT Mon Apr 17 2017

The longer term concerns remain the timing of the next short wave
trough Wednesday/Thursday time period. The thunder threat does
exist, along with the potential of some frost/freezing
temperatures mainly Friday morning.

The extended deterministic models are in good agreement with
overall timing of the next wave. We expect it to spread clouds
into the area Tuesday night and then showers and at least a chance
of thunder across the southern half of the cwa. This should
spread east Wednesday night and then lingering at least a chance
of showers over mainly the eastern cwa for Thursday. The GFS is
slower and a little deeper with the short wave. Temepratures
appear to be trending a little cooler as well and the rain snow
mix late Wednesday night into the far northern cwa looks possible.

High temperatures will struggle to reach 50 over southwest as the
clouds and showers arrive and that will shift east into Thursday.
We should see some partial clearing over the west Thursday
afternoon and this should help boost temperatures into the mid 50s
at least. High pressure follows this system through Saturday. THis
should provide more sunshine and cool overnight lows. The
potential for frost/freezing temperatures looks best Friday
morning across the northern cwa. Depending on how quickly this
system shifts east, it may linger into west central WI for
Saturday morning as well. We should be able to see temperatures
rebound through the 50s to some lower 60s Friday and Saturday and
mainly the 60s for Sunday. The next trough/shower threat arrives
the following Monday.


.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 1234 PM CDT Mon Apr 17 2017

Several concerns this cycle. The first is the threat for LLWS late
tonight and early Tuesday morning as S winds near 50 knots
develop in the 015-020 foot range. This is not seen in all short
term solutions so confidence is low at this point. In addition, there
will be showers and isolated thunderstorms moving in from the
west as the stronger low level winds develop, which with TSRA
implies LLWS is possible. Therefore, have not mentioned LLWS in
the TAFS at this time. Confidence is high on a band or two of
showers and isolated thunderstorms moving into western MN after
06z, reaching the Twin Cities around 12z and KEAU by 15z. There
will be about a 4 hour period where ceilings/visibilities
fluctuate between VFR and MVFR. In the wake of showers, surface
winds will be on the increase from the SSW and then W as a low
pressure system passes just north of the TAF sites Tuesday
afternoon and evening. Sustained winds on Tuesday from 18-22
knots are likely along with gusts from 26-32 knots.

KMSP...Few concerns through this evening with VFR prevailing.
Problems develop late tonight when showers and isolated
thunderstorms move in from the west. Timing remains on track with
the best chance for precipitation between 12z-16z. MVFR ceilings
to linger after the showers for a few hours with a return to VFR
by afternoon. Light N winds this afternoon becoming east this
evening and then SE 13g20kts after 06z. Stronger SSE winds Tuesday
morning 15-20kts, then more southerly at 20 knots by late
morning, becoming westerly in the afternoon. Gusts from 25 to 30
knots on Tuesday as well.

Tue ngt...VFR. Wind NW 10 kts.
Wed...VFR with -RA/MVFR ceilings in the aft/eve. Wind NE 8 kts.
Thu...MVFR Cigs possible early then VFR. Wind NE at 5-10kt.




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