Area Forecast Discussion
Issued by NWS Bismarck, ND

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FXUS63 KBIS 130521
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
1121 PM CST Sun Nov 12 2017

.UPDATE...
Issued at 1121 PM CST Sun Nov 12 2017

Latest suite of surface observations, webcams, and GOES16
nighttime microphysics satellite imagery indicate dense fog across
far north central and northwest ND. Mclean and Sheridan counties
have improved considerably and will remove them from the dense fog
advisory. The remaining counties are in good standing. Rest of the
overnight forecast is on track.

For Monday, 925mb temps are as warm if not warmer than Sunday,
thus will look at possibly raising high temperatures after the
gridded data/Forecast Builder runs shortly.

UPDATE Issued at 951 PM CST Sun Nov 12 2017

Based on largely NDDOT webcam trends through 0330 UTC, cancelled
the Dense Fog Advisory for Wells county, but, extended it into
Renville and Bottineau counties. Still plenty of uncertainty in
how the fog will evolve across the north central, whether it will
continue a slow regression north with drier air in southeasterly
winds, or if it will hold more solidly as suggested by the 03 UTC
GFSLAMP.

UPDATE Issued at 757 PM CST Sun Nov 12 2017

Expanded the Dense Fog Advisory to include Burke and Divide
counties per observed trends through 0130 UTC and the consensus of
the 01 UTC RAP/NBM/GFSLAMP and the 00 UTC HRRR visibility
forecasts which favor dense fog focusing into far northwest North
Dakota through the night. The fog has been eroding across
portions of eastern McLean into Sheridan and Wells counties over
the past 1 to 2 hours. Thus, the Dense Fog Advisory may be
cancelled later this evening if trends continue for these counties.
In fact, the CAMs suggest that drier air with southeasterly winds
may erode the fog through Minot by 05-07 UTC.

UPDATE Issued at 552 PM CST Sun Nov 12 2017

Little change with this update. Some uncertainty exists how long
dense fog will last tonight across Sheridan, Wells and possibly
McLean counties with southeasterly winds advecting drier air into
the area. The 23 UTC RAP/NBM/GFSLAMP and 22 UTC HRRR within their
visibility forecasts suggest the fog for these areas decreasing
over the next 1-3 hours. Otherwise, the dense fog is favored by
the aforementioned guidance to remain solidly in place across the
northwest, and potentially expanding towards the international
border of the north central. Modifications to the current Dense
Fog Advisory are certainly possible through the night.

&&

.SHORT TERM...(This evening through Monday)
Issued at 428 PM CST Sun Nov 12 2017

The main forecast issue in the short term continues to be fog/no fog
issues, how dense any fog might become, as well as sky cover. Late
this afternoon decided to issue a dense fog advisory for portions of
northwest and north central ND, mainly along and north of Lake
Sakakawea to the Harvey area. Later shifts may need to expand this
advisory.

Currently, the surface high pressure center was off to our east in
Minnesota/Iowa, with the high pressure axis extending northwestward
into the Devils Lake Basin/Turtle Mountains area. Warm advection
southerly winds were established over western and most of central
North Dakota. Throughout the day, the area of low clouds and fog
that developed early this morning persisted until around noon CST
over northwestern and into parts of central ND...mainly from
McKenzie to Divide counties...east/southeast along Lake
Sakakawea...nearly making its way to the Minot area. There was a
large temperature spread across our area this afternoon, with lower
20s in the Turtle Mountain area to the lower 50s in parts of the
southwest.

The short term high res models continue to depict dense fog
(visibilities of 1/4 mile or less) in most of northwest North Dakota
this afternoon, but by mid-afternoon visibilities there had improved
around noon CST with most areas having visibilities above 3 miles.
It was only after 3 pm when visibilities began to drop. Some area
web cams continued to show some locales with lower visibilities in
fog, especially around Lake Sakakawea and a few points north. The
evolution of fog expansion is the main challenge for tonight.

The high res models indicate the area of low clouds and fog
expanding tonight and moving northward. Thus will have a mention of
widespread fog across all of northwest and north central ND.

The broad ridging aloft continues on Monday, along with southerly
winds. Low clouds and fog should erode from south to north on Monday
as was seen Sunday afternoon. Highs Monday should again be in the
low/mid 50s far southwest, but reach into the 30s in the Turtle
Mountains.

.LONG TERM...(Monday night through Sunday)
Issued at 428 PM CST Sun Nov 12 2017

Deterministic models are in reasonable agreement through mid week.
A cold front moves through the area on Tuesday afternoon/evening
bringing only minimal precipitation chances and a brief cooldown on
Wednesday north and east. Expecting breezy northwest winds late
Tuesday afternoon and night mainly across the northeast half of the
state.

Although there are some differences between the GFS/ECMWF with the
next wave that moves through Thursday/Friday, their solutions,
especially regarding the position of the northern upper trough, have
come into better agreement. We are expecting strong south winds
(especially the James Valley to Turtle Mountains and east) and
seasonable to mild conditions Thursday. Then the cold front moving
through Thursday night with northwest winds developing, and becoming
strong on Friday with colder air moving in. Highs Thursday from 30
to 50 northeast to southwest...cooling to highs Friday from lower
20s north to 30s south. Precipitation chances still look best to the
north and east of our area. Model consensus is still giving mainly
slight chances of light rain or snow for us.

The colder air Friday lingers into Saturday, with a moderate
recovery in the southwest on Sunday.

&&

.AVIATION...(For the 06Z TAFS through 06Z Monday night)
Issued at 1121 PM CST Sun Nov 12 2017

Vlifr cigs/vsbys forecast for KISN/KMOT until 14z-15z Monday.
Thereafter, a return to vfr conditions expected. Elsewhere, light
winds and vfr cigs/vsbys this Taf period.

&&

.BIS WATCHES/WARNINGS/ADVISORIES...
Dense Fog Advisory until 6 AM CST Monday for NDZ001>004-009>012.

&&

$$

UPDATE...KS
SHORT TERM...JV
LONG TERM...JV
AVIATION...KS



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