Area Forecast Discussion
Issued by NWS Grand Forks, ND

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977
FXUS63 KFGF 180010
AFDFGF

Area Forecast Discussion
National Weather Service Grand Forks ND
710 PM CDT Thu May 17 2018

.UPDATE...
Issued at 704 PM CDT Thu May 17 2018

First wave of storms has weakened (strongest storms did stay west
and south of CWA) and transitioned to primarily rain showers as
line moved east of instability axis. Still a few claps of thunder
north of FAR, which should weaken as well. Intense LLJ develops
later in the evening over w cntrl SD and more storms/showers will
develop and advect eastward in to primarily wrn zones, where
higher rainfall amounts are expected. At this point not enough new
QPF data to evaluate for changing expected precip amounts, but
NAMnest does indicate higher rainfall amt axis may be west of CWA.

&&

.SHORT TERM...(This evening through Friday)
Issued at 255 PM CDT Thu May 17 2018

Challenge and impacts continue to be placement and amounts of
convection activity through the next 24 to 36 hours. Showers with
embedded thunder continue to lift north and east across the area
as moist and warm air advection bring PWats greater than an inch ahead
the parent upper wave. MUCAPE remains on the low side with values
generally 500 J/kg or less across the FA. As the current activity
weakens and moves east another round of precipitation is
developing across the western high plains and is expected to
evolve and lift into the Devils Lake basin overnight into Friday
morning. As the SFC low and main 500mb wave lift into central ND
Friday rain will continue across the northwest portion of the FA.
With afternoon heating and fropa finally pushing southeast
another round of showers and storms are expected to develop in SE
ND and spread through the southern valley into west central MN.
Event total rainfall amounts continue to range from a half inch
to around 2 inches, lowest in W central MN and highest across the
Devils Lake basin. High temps will range from the upper 40s and
low 50s in DVL basin to near 80 in the southern valley tomorrow.

.LONG TERM...(Friday night through Thursday)
Issued at 255 PM CDT Thu May 17 2018

Sat-Sun: A cold front continues southeast out of the area pushing
rain chances deeper into Minnesota with drier, cooler air filtering
in from the north and northeast. Although the surface cold front is
expected to move well south of the region, there is still some
question of how fast moisture gets scoured out towards the south
from dry northeasterly mid level flow. Guidance continues to
indicate another lee wave moving out of Colorado into southern
Minnesota which could battle the dry air intrusion from the north,
or at least slow it down. For this reason, areas from south of Fargo
to Park Rapids and points southward still hold a slight chance of
rain showers through Saturday morning. Eventually the dry air should
win with high pressure squeezing itself into the region. This
squeezing of the surface gradient combined with cold air advection
will allow for gusty northeasterly winds to develop Saturday.
Saturday will be noticeably cooler compared to previous days with
high temperatures only reaching into the lower to mid 60s. By
Sunday, the center of the surface high will nestle itself over the
region likely resulting in dry conditions. Clear skies and calm
winds should allow for efficient radiational cooling during the
early morning hours Sunday. With a dry air mass in place noted by
dew points in the lower to mid 30s there is the potential for lows
to dip to these temperatures posing some risk for frost. Will not
introduce this chance into the forecast however due to the expected
variability in guidance to come.

Mon-Thu: The aforementioned surface high pressure will block a
surface low from pushing north keeping rain chances out of the CWA
towards the south Monday. The high begins to shift eastward late
Monday into Tuesday allowing for return flow and warmer temperatures
with highs deeper into the 70s. With this return flow, guidance is
having a difficult time resolving moisture return and its
interaction with a transient mid level wave dropping out of the
Canadian High Plains towards Tuesday. The ECMWF favors moving this
wave through the region allowing for rain chances to develop around
the Tuesday into Wednesday time frame. While the forecast reflects
this solution, confidence is low as guidance typically has a
difficult handling the movement of perturbations within weak/split
flow regime, as is expected with the polar jet stream remaining deep
into the Canadian interior. Towards mid to late next week, another
scenario involving a weak upper cyclone breaking eastward out of the
western US within an upper level ridge should increase precipitation
chances.

&&

.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 704 PM CDT Thu May 17 2018

Primarily VFR conds outside of SHRA/TSRA within and west of valley
with some lower cigs in the MVFR (tempo IFR) range vcnty DVL.
Should see some increase in cigs in this region as quasistationary
boundary begins to lift north. Main impacts on general aviation
will be storms vcnty FAR and avoiding SHRA...and for commercial
flights...late flight JMS-DVL could experience TSRA with second
wave of storms.

&&

.FGF WATCHES/WARNINGS/ADVISORIES...
ND...None.
MN...None.
&&

$$

UPDATE...Speicher
SHORT TERM...JK
LONG TERM...CJ
AVIATION...Speicher



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