Area Forecast Discussion
Issued by NWS Aberdeen, SD

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FXUS63 KABR 300906

Area Forecast Discussion
National Weather Service Aberdeen SD
406 AM CDT Tue May 30 2017

.SHORT TERM...(Today through Thursday Afternoon)
Issued at 406 AM CDT Tue May 30 2017

While the overall pattern will indicate northwesterly flow at
500mb through the period, the high amplitude ridge currently across
ID will move across eastern MT/western Dakotas by the end of the day
Thursday. This will be while the persistent low to our northeast
continues to exit across southeastern Canada.

High pressure situated over southern Saskatchewan will slide
directly overhead 06-12Z Wednesday. Patchy frost may be possible
tonight over portions of the region, mainly east of the Missouri
River, with temperatures falling into the mid 30s, light winds, and a
clear sky. Included the potential in the HWO for now, and will get
another good look at the threat later today. Additional frost
headlines may be needed.

A warming trend will take hold during the day Wednesday, as the sfc
high sinks southeast across IA. Southeasterly wind will return, and
temperatures should end up topping out near seasonal normal values
Wednesday afternoon. Isolated showers and possibly thunderstorms may
sneak into our southwestern counties Wednesday night, otherwise a
mainly dry forecast should remain. The southeasterly winds will
persist and increase slightly for Thursday, with 850mb temps jumping
up to 12 to 19C by mid afternoon.

.LONG TERM...(Thursday Evening through Monday)
Issued at 406 AM CDT Tue May 30 2017

Not unlike the current blocky/highly amplified upper level steering
flow pattern, much of the out periods continue to maintain this
"weird"-looking upper flow pattern, atypical of an early June flow
pattern over NoAm. In the 00Z deterministic solutions of the
Canadian, ECMWF and GFS tonight, at least there seem to be a couple
of features/themes seen in all of them through 180 hours (day 7)
that lend a little bit of forecast confidence to the precipitation
forecast; namely longwave troffing over the two coasts with weak
upper ridging nestled in between over the central/northern plains.

For a third night in a row, low level thermal and pressure progs
seem to be highlighting the formation and/or movement of a warm
front up into eastern South Dakota somewhere by Friday. Per GFS
soundings in BUFKIT, most of the area appears to be capped
Friday/Friday night and (low level) moisture starved. Perhaps over
toward the southeastern corner of the CWA, there could be enough low
level moisture advection, forcing and lift along or north of the
boundary by early Friday evening to see some thunderstorms develop.
And then there is still the signal in the models for some stronger
polar jet westerlies to enter the scene on Saturday, shoving a cold
front through the region, and perhaps enough forcing/lift with the
fropa to generate some scattered coverage of showers and
thunderstorms Saturday into Saturday night. By late Saturday night
and Sunday, things appear to dry out as upper level ridging tries to
re-assert itself over the CWA. The general consensus amongst
deterministic models (although not well-timed or producing similar
areal coverage of qpf) is that more energy over the western CONUS
will then be trying to work into the region by Monday evening into
Tuesday and guidance pops (unchanged) appear to address this.

According to the deterministic solutions and the available ensemble
guidance, temperatures are the warmest over the CWA Thursday night
through Friday night (perhaps between 2 and 3 standard deviations
above normal) before the Saturday cold frontal passage signals a
return to temperatures closer to normal for early June during the
latter half of the weekend and on into early next week.


.AVIATION...(For the 06Z TAFS through 06Z Tuesday Night)
Issued at 1221 AM CDT Tue May 30 2017

VFR conditions will prevail across the area through Tuesday


SD...Frost Advisory until 8 AM MDT this morning for SDZ003-015.



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