Area Forecast Discussion
Issued by NWS Grand Forks, ND

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118
FXUS63 KFGF 141951
AFDFGF

Area Forecast Discussion
National Weather Service Grand Forks ND
251 PM CDT Mon Aug 14 2017

.SHORT TERM...(This evening through Tuesday)
Issued at 212 PM CDT Mon Aug 14 2017

Main impacts will be in the long term however the evolution of
this next event being Tuesday afternoon...and the primary
challenge will be timing of the next round of rainfall and
isolated storms into my western zones on Tuesday. Models in better
agreement and a tad slower today, with best chances for rain from
Devils Lake to Valley City being mid- to late afternoon. This
system lacking instability and think it will be primarily rain
showers Tuesday with some isolated TS in the 21Z to 00Z Wed
timeframe.

For remainder of aftn and early evening...NE flow has scoured out
low cigs and southeastern half of CWA is cellular now, expecting
this cu field to dissipate early this evening.

Tonight...Mid level cloud over western Dakotas will move into ern
ND overnight...but expecting southeastern to remain clear for
most of night and with light winds fog should develop towards
morning. Keeping best chance for areas of fog in the southeastern
quadrant of the CWA.

Tuesday...upper ridge remains over eastern half of CWA during the
morning and shifts to our eastern edge by 18Z. SW flow into the
western half of the CWA sets up...and main challenge becomes
timing leading wave and precip into the western zones. ECMWF
brings POPs all the way to Fargo by 18Z but all other models
generally keep morning precip well west of the valley. Will hold
off on high chance POPs (40s/50s) until the 21Z to 00Z timeframe
as NAM keeps main precip west of CWA in the late aftn period. Main
show begins Tuesday night (see long term discussion below).

.LONG TERM...(Tuesday night through Monday)
Issued at 212 PM CDT Mon Aug 14 2017

As a developing shortwave moves in from Tuesday afternoon through
Wednesday night, expect the main threat to be the potential for
heavy rain for Richland, Ransom, and Sargent counties that saw
considerable rain this past weekend. Elsewhere, this system will
likely bring welcome relief from drier than normal conditions.
Starting Tuesday afternoon and evening, showers will begin moving
east into eastern North Dakota from central North Dakota. Late
Tuesday night through Wednesday, shower coverage will become more
widespread as precipitable water values reach 1.5 to nearly 2 inches
across the area and forcing increases from a strengthening 700 mb
shortwave, some upper level jet influence, and overrunning from a
surface low moving from south central South Dakota toward the Twin
Cities metro. Expect some isolated to perhaps scattered thunder, but
instability will be quite weak (less than 500 J/kg most unstable)
even in the afternoons, so severe threat looks quite low. QPF is
more the main focus of concern. Locations for the heaviest amounts
are difficult to pinpoint with considerable model and ensemble
spread, but at this point, a model consensus generally depicts at
least an inch of rain for areas along and south of a Lisbon to Fargo
to Bemidji line, with potential for locally varying pockets of as
much as 2 to 4+ inches. Locations north of this line can expect
generally less than an inch of rain.

For Thursday through Thursday evening, high pressure brings dry and
a bit warmer conditions after the previous system moves out.
Precipitation chances move back in late Thursday night through
Friday night with a boundary passing through. Will be monitoring for
severe potential with this boundary, despite weak shear, due to
recent deterministic model indications of moderate instability
creeping into the southern valley during Friday afternoon and
evening.

Through the middle of the work week, temperatures look to
remain cool with highs in the 70s. For the end of the week, a bit
warmer with highs nearing 80, and for the weekend, a drier forecast
with highs peaking in the upper 70s to middle 80s.

&&

.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 1236 PM CDT Mon Aug 14 2017

FAR continues to have IFR cigs around 500 ft...however, NE flow is
rapidly pushing clearing line NE of FAR toward the aerodrome and
expect it to clear out within the next hour. The dry northerly
flow will clear remainder of area by mid aftn however parts of w
cntrl MN will likely cu up with increased heating....clearing
again aft sunset. Mid level clouds then spread into ern ND during
last 6 hours of 18Z TAFs.


&&

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

$$

SHORT TERM...Speicher
LONG TERM...BP
AVIATION...Speicher



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