Area Forecast Discussion
Issued by NWS Bismarck, ND

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FXUS63 KBIS 180539
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
1239 AM CDT Wed Apr 18 2018

.UPDATE...
Issued at 1203 AM CDT Wed Apr 18 2018

Minor adjustments were made to the precip forecast based on latest
trends. A very narrow band of snow has developed between Dickinson
and Glen Ullin. This band of snow across west central North Dakota
will remain through the overnight hours. Warm road temperatures
should limit freezing/accumulation on the roadways.

UPDATE Issued at 850 PM CDT Tue Apr 17 2018

Mesoscale models continue to trend farther west with snow. 18Z NAM
keeps any snow accumulation west of Bismarck and Minot. And the 18
April 00 UTC RAP and HRRR keep accumulations well west of Bismarck
and Minot. Utilized a blend which still kept a couple tenths in
Bismarck but kept Minot dry. Overall theme here is precipitation
remains confined to the vicinity of the inverted trough, which
continues to weaken overnight and Wednesday. Heaviest snow totals
remain in this area, from around Crosby and Tioga, through eastern
Dunn county and between Dickinson and Hebron and south into South
Dakota. Generally an inch amounts in this area, maybe up to 1.5
inches. Snowfall tapers quickly as you go east or west of this
line. Updated text products will be sent shortly.

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 06Z TAFS through 06Z Wednesday night)
Issued at 1203 AM CDT Wed Apr 18 2018

Low pressure trough across western North Dakota will remain
nearly stationary through Noon CDT Wednesday, then weaken and move
southeast as high pressure nudges south into Northwest North
Dakota after 00Z. This weather pattern will maintain VFR
conditions from KJMS-KMOT. MVFR conditions are expected to develop
KDIK-KISN after 08z and move into KBIS after 11Z. Conditions will
slowly improve to VFR after 18-21z.


&&

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

$$

UPDATE...AJ
SHORT TERM...TK
LONG TERM...TK
AVIATION...WAA



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