Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 190203 AAB

Area Forecast Discussion...UPDATED
National Weather Service Twin Cities/Chanhassen MN
903 PM CDT Fri May 18 2018

.SHORT TERM...(This evening through Saturday)
Issued at 346 PM CDT Fri May 18 2018

Trend of decreasing precip potential with the incoming front
continues. The problems this front are encountering include weak
forcing in split flow, with the MPX area stuck between the
northern stream up in southern Canada and the southern stream down
across the srn/central Plains. We also lack much in the way of
instability thanks to dewpoints only in the 50s and meager mid
level lapse rates. And finally, the low levels remain quite dry
ahead of the front.

Based on what we are seeing with the HRRR and other CAMs, looks like
we`ll see only scattered showers developing along the front as it
moves through tonight, with precip amounts for where it does rain
rather meager.

What we do look to get with the front is a good dose of post frontal
stratocu as what we see up in NODAK today moves through here tonight
and Saturday. This cloud cover along with CAA behind the front will
help hold highs back a good 10 degrees from what we are seeing
today. They also look shallow and unlikely to provide us with much,
if any precipitation.

.LONG TERM...(Saturday night through Friday)
Issued at 346 PM CDT Fri May 18 2018

The long term will start with southern stream wave currently coming
out of the 4-corners region slowly making a trip across Iowa and the
WI/IL border Sunday and Monday. There will be several bouts of
showers and storms beneath this wave, but those will stay largely
south of us. Our problem is the northern stream wave going across
southern Canada on Saturday will drop an area of high pressure over
central MN/northern WI. Dry air associated with the high will limit
the northern extent of precip Sunday/Monday, with the I-90 corridor
looking to have the best shot at seeing rain. Current PoPs probably
still spread precip chances too far north Sunday and Monday, but we
did see a southward contraction with this forecast update.

Behind this system it`s back to more of the same for what we`ve been
dealing with much of May. With the northern stream retracting well
north into Canada as an upper ridge builds from the northern high
Plains up toward eastern Alaska. A weak southern stream under-cuts
the ridge, coming out across the southern/central Plains. This
means highs in the 80s return Tuesday and will stay with us for the
rest of the work week. As heat/moisture slowly build next week,
models show increasing instability and start generating qpf based on
diurnal destabilization and nightly increases in the strength of the
LLJ. Current forecast is probably overdoing the endless precip
chances that start Wednesday as at some point Wednesday thru
Saturday you can find a model giving us precip, hence the forecast
that sounds a lot more active than it will really be. Best precip
chances look to come Friday/Saturday when there is at least some
agreement on a system working across the upper MS Valley, though it
does not look overly strong, with severe weather or even healthy
rainfall amounts looking unlikely.


.AVIATION...(For the 06Z TAFS through 06Z Saturday evening)
Issued at 903 PM CDT Fri May 18 2018

MVFR and some IFR cigs will progress eastward behind a cold front
overnight. MVFR cigs are expected area wide Saturday morning with
conditions improving again to VFR during the afternoon from west
to east. Expecting a mostly dry forecast, with only a few showers
near the front tonight.

KMSP...MVFR cigs arrive by Saturday morning. Cannot rule out a few
showers nearby late this evening through the overnight.

SUN...VFR. Wind ENE 5-10 kt.
MON...MVFR. Chc -SHRA. Wind E 5-10 kt.
TUE...MVFR cigs early, then VFR. Wind lgt and vrb.




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