Area Forecast Discussion
Issued by NWS Twin Cities, MN

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948
FXUS63 KMPX 180751
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
251 AM CDT Wed Apr 18 2018

.SHORT TERM...(Today and tonight)
Issued at 251 AM CDT Wed Apr 18 2018

Surface analysis early this morning shows a fairly well-organized
low pressure system centered over eastern KS with a warm front
extending eastward through the southern tip of IL and a trailing
cold front extending SW through the TX/OK Panhandles into NM.
Aloft, a narrow negatively-tilted upper level trough, emanating
from a larger trough over western Canada, remains offset to the
northwest of the surface low while ridging builds into the CONUS
Intermountain West.

Over the next 24 hours, the trough near the surface low will
become cutoff, with this new low being dragged eastward by
another large upper trough over the northern Atlantic. The surface
low will then also be similarly ushered along eastward, centering
itself into central IL by midday today then moving through the
Ohio Valley tonight and to the Mid-Atlantic region by daybreak
Thursday. This system still looks to have plenty of moisture with
it but the system is overall shifted a bit south again, as was
shown yesterday. There are still multiple dynamic factors at play
which may well produce nearly 1 in/hr rates in far southern MN
later this morning but with the better forcing further south and
weaker upper level support, snowfall amounts are again expected to
be not quite as high. Have lowered amounts such that the winter
storm warning will be confined to the southern-most 3 counties in
south-central Minnesota with the advisory only one row of counties
north then nothing beyond that. The snowfall will mainly take
place during the day today and the forcing from the snowfall
should keep highs only in the 33-34 degree range in far southern
MN with higher temperatures going north.

With the system quickly pulling away this evening and tonight, the
snowfall will end late this afternoon into the evening with little
to no additional accumulation by sunset. Skies will then partially
clear out overnight as lows drop into the mid-20s area-wide.

.LONG TERM...(Thursday through Tuesday)
Issued at 251 AM CDT Wed Apr 18 2018

Long term concerns will trend warmer with focus turning toward
hydro as snow melts in earnest this period. Some timing differences
in the frontal passage early next week.

Following Wednesday storm system, high pressure follows in its
wake  leaving mainly dry conditions during the first part of the
period. Upper flow pattern continues to be split with the main
moisture and energy for the next frontal in the southern stream.
Some moisture tries to work north into the Dakotas and may clip
far western MN later Friday night or early Saturday but it looks
like the surface ridge in place will preclude any significant
precipitation threat. Temperatures over the first part of the
period will be modulated somewhat by snowcover and possible fog
development as the snow melt continues. Greatest fog threat would
be found under the surface ridge. We wont warm it as fast as
models currently do, shade a degree or two through the weekend.

Question comes how much of a snowpack will there be by next
Monday. We could be nearly snow free again. If this happens,
warming ahead of the next cold front could be realized, with some
lower 60s possible. There are some timing differences in the front
with the GFS a bit faster and holding more moisture than the
ECWMF. We will temper the highs some and mention a small chance of
rain with its passage.

Rivers will continue to be on the rise with the snow melt, and several
rivers and streams will reach minor flood stage through the
weekend and into early next week. Consult the latest river summary
concerning the latest river forecast trends.

&&

.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 1106 PM CDT Tue Apr 17 2018

VFR conditions until Wednesday morning when snow begins to move
into southern Minnesota. MVFR cigs are also possible to the north
of the snow. The worst conditions (possibly LIFR at times) will
impact RWF and MKT, although some light snow is possible as far
north as MSP and RNH.

KMSP...It still appears the snow will push in around early
afternoon and last for perhaps 4 to 6 hours. Accumulations look
light.

/OUTLOOK FOR KMSP/
Thu...VFR. Wind N at 5 to 10 kts.
Fri...VFR. Wind light/vrb.
Sat...VFR. Wind bec S at 5 kts.

&&

.MPX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...Winter Weather Advisory until 7 PM CDT this evening for MNZ082.

     Winter Weather Advisory from 7 AM this morning to 1 AM CDT
     Thursday for MNZ083>085.

     Winter Storm Warning from 7 AM this morning to 1 AM CDT Thursday
     for MNZ092-093.

     Winter Storm Warning until 7 PM CDT this evening for MNZ091.

&&

$$

SHORT TERM...JPC
LONG TERM...DWE
AVIATION...BORGHOFF



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