Area Forecast Discussion
Issued by NWS Bismarck, ND

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FXUS63 KBIS 172252
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
552 PM CDT Tue Apr 17 2018

.UPDATE...
Issued at 540 PM CDT Tue Apr 17 2018

Quick update to update pops/qpf. Latest 18Z medium range model
guidance and latest mesoscale models continue to trim back on the
eastward extend of precipitation and total qpf with this system.
Utilized a blend of latest mesoscale guidance with current
Superblend and medium range models. This delays higher pops and
precip around Bismarck/Mandan until after midnight and knocks
back snow totals to around a half inch (in Bismarck/Mandan). This
may even be overdone if trends continue, but at least a good
start. Still may see an are of 1-2 inches but likely in a narrower
band. Updated text products will be sent shortly.

&&

.SHORT TERM...(This evening through Wednesday)
Issued at 220 PM CDT Tue Apr 17 2018

Light rain will continue moving eastward from eastern Montana into
western and central North Dakota this evening. Expect light rain
to change over to light snow later this evening as the forecast
NAM BUFR soundings show temperatures falling below freezing
throughout the entire column with a saturated snow growth zone.
The forecast NAM sounding in Bismarck for 12z matches the observed
12z sounding very well, so confidence is high that the NAM will
continue performing well into tonight.

Light snow will likely continue through tonight and into tomorrow
morning as a convergence zone with associated mid-level
frontogenesis becomes nearly stationary over central North Dakota.
Any leftover snow will change back over to light rain during the
late morning and early afternoon tomorrow as surface temperatures
warm into the 40s for most spots. Expect a trace to an inch or two
of snow accumulation from most of western and central North Dakota
by tomorrow afternoon.

Conditions dry out tomorrow afternoon and evening as a surface
high pressure system begins building in from the west.

.LONG TERM...(Wednesday night through Tuesday)
Issued at 220 PM CDT Tue Apr 17 2018

High pressure will dominate western and central North Dakota
Wednesday night through Thursday night, making for calm weather.
Some leftover clouds will keep temperatures in the 40s and lower
50s on Thursday. A split flow pattern with a large upper- level
low over the four-corners region will prevail on Friday, giving
southern North Dakota a slight chance of light rain for Friday
and Friday night.

A ridge will build over North Dakota on Saturday and Sunday,
leading to sinking motion and mostly clear skies. This will allow
for strong mid-April sunshine to warm western and central North
Dakota into the low to mid 60s on both Saturday and Sunday.
Although the latest suite of model guidance suggests colder
conditions mainly in the 50s, the bias-corrected models have been
about 5 to 10 degrees too cold in most spots the past couple of
days, likely due to a pattern change to warmer weather. The ECM
and MAV MOS guidance has been performing much better, suggesting
highs very close to what has been observed. For these reasons, the
high temperatures for Saturday and Sunday have been manually
increased by 5 degrees or more across all of western and central
North Dakota to account for model guidance likely being too cold.

Chances for light rain and snow return to southern North Dakota
for Monday through early Tuesday morning as a shortwave moves
through from the northwest. Conditions dry back out Tuesday
afternoon and evening as a ridge begins building back in from the
west.

&&

.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 540 PM CDT Tue Apr 17 2018

Light rain will spread into central North Dakota this evening
while changing over to snow, leading to MVFR/IFR conditions for
KBIS by 07z and KMOT by 10z. Once MVFR/IFR conditions arrive at
any given terminal, expect those conditions to continue through
the morning with improving conditions in the afternoon. MVFR
conditions currently forecast to not quite reach KJMS.

&&

.BIS WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...TWH
SHORT TERM...TK
LONG TERM...TK
AVIATION...TWH



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