Area Forecast Discussion
Issued by NWS Grand Forks, ND

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FXUS63 KFGF 210356 AAA

Area Forecast Discussion...UPDATED
National Weather Service Grand Forks ND
1056 PM CDT Tue Mar 20 2018

Issued at 1055 PM CDT Tue Mar 20 2018

Updated aviation discussion for 06z TAF issuance.

UPDATE Issued at 1012 PM CDT Tue Mar 20 2018

Latest surface obs indicate a mix of light snow and freezing
drizzle entering the Devils Lake basin, so adjusted precipitation
chances and types to account for this. This will continue
overnight as expected, as drier, warmer air aloft moves in aloft.
Could produce some slick spots on roads, especially as daytime
melt refreezes now that temperatures are slowly dropping.

UPDATE Issued at 643 PM CDT Tue Mar 20 2018

Added in small chances for light snow and flurries in the Devils
Lake basin this evening as radar returns over north central ND
have been reaching the ground. No other significant changes needed
at this time.


.SHORT TERM...(This evening through Wednesday)
Issued at 258 PM CDT Tue Mar 20 2018

Challenge for the low impact weather for the short term will
hinge mostly on cloud cover and light precipitation. Next short
wave bringing some light echoes across western ND this afternoon
will provide lift and continued light snow or flurry activity for
the overnight period. Flurries transitioning to some patchy
drizzle in the south possible as ice nuclei aloft diminishes
through the overnight period. The saturated surface layer is not
going anywhere within the light winds regime and therefore fog
will again be possible through the overnight. With day break
diminishing chances of precipitation is expected with a dry
forecast by noon Wednesday. Some sun maybe possible tomorrow
afternoon with highs in the mid and upper 30s expected.

.LONG TERM...(Wednesday night through Tuesday)
Issued at 258 PM CDT Tue Mar 20 2018

An active weather pattern resumes later this week after a mid week
warm up.

Upper level ridging and southerly return flow mid week will allow
for calm weather and afternoon temperatures to climb into the upper
30s and low 40s for Thursday. Lee troughing over the northwestern
Plains is expected late Thursday night as a longwave trough over the
western US begins to move eastward. As this occurs, high
precipitable water values will advect northward in response to the
strengthening lee cyclone. Recent GEFS ensemble means continue to
rank Friday`s PW values above the 90th percentile. As large scale
ascent moves over the northern Plains during the day Friday a broad
region of precipitation is expected over central and eastern North
Dakota. Deterministic models continue to indicate the potential for
frontogenetical banding, which could cause locally higher amounts of
precipitation. Precip type during the Friday through Saturday time
period will be determined mainly by diurnal heating as afternoon
temperatures above freezing will favor rain or a rain snow mix,
while overnight lows just below freezing will favor snow.

Most deterministic guidance show a fast moving upper level shortwave
propagating through the region within the southwesterly flow
Saturday night through Sunday behind the initial system. Another
round of precip will be possible along a trailing cold front across
eastern North Dakota and far northwestern Minnesota. Precip totals
associated with this second system are not expected to be as high,
though liquid accumulation over the duration of the weekend could
range from a few tenths to nearly one inch over eastern North
Dakota. Any lingering precipitation will slowly move out of the
region on Monday.

While snow accumulation is likely during the overnight hours this
weekend, any potential impacts will be determined by both the timing
of the heaviest precipitation with the diurnal temperature curve and
how quickly snow can melt off during the daytime hours. Because of
this uncertainty in timing, confidence in specifics such as snowfall
amounts, type, and placement is still low.


.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 1055 PM CDT Tue Mar 20 2018

Any remaining VFR cigs will gradually worsen to MVFR late tonight,
persisting overnight and well into Wednesday. IFR cigs will
develop spread into the valley and further east toward BJI late
tonight and into the morning. Scattered light snow and freezing
drizzle will remain possible with IFR and low MVFR cigs through
the night, with reduced visibilities due to fog being possible as
well. Light winds will remain out of the south or southeast
through the TAF period.




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