Area Forecast Discussion
Issued by NWS Oklahoma City, OK

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FXUS64 KOUN 281947

Area Forecast Discussion
National Weather Service Norman OK
247 PM CDT Wed Jun 28 2017

Latest observational data shows compact shortwave trough moving from
the northern Plains into the Midwest with an attendant sub-1000 mb
surface low in Minnesota. Negative 500 mb height anomalies increase
with higher latitude owing to a fairly tight gradient for this
time of year. A broad area of mid-level flow across the Rockies
has helped form lee troughing/transient lee low in the High
Plains. Southerly winds have strengthened across our area as a
result. Low-end elevated or nearly elevated fire weather
conditions may result in the windy and warm/dry environment this
afternoon and again tomorrow afternoon across mainly northwest
Oklahoma (see Fire Weather section below).

A trough will deepen over the northern Rockies Thursday and then
move east into the Plains Friday forcing a cold front south into the
area. Convergence along/near the front and subtle forcing aloft
should be enough for thunderstorms to develop late Friday and
probably increase into the evening. Moderate instability and
effective bulk shear of around 30-35 knots will support a low end
severe thunderstorm risk with damaging winds and a few instances
of marginally severe hail late Friday through Friday evening.

The cold front will shift south and become diffuse by Saturday with
only slightly cooler temperatures expected. The forecast becomes
unclear this weekend into next week with regards to rain chances.
Models show a quasi-zonal flow with generally weak small scale waves
traversing the area into next week. These convective regimes are
difficult since it only takes subtle forcing in a moist/unstable
environment for thunderstorms which can occasionally grow upscale
enough to overturn instability limiting additional activity for at
least a short period. Once models come into better agreement on
timing of transient shortwave troughs, we`ll have better confidence
with assigning precipitation probabilities.



A low-end fire threat may develop later today and again tomorrow
afternoon. Southerly winds around 20 knots combined with hot
temperatures in the mid 90s to near 100 and minimum RH around 30
percent or just below will result in elevated or nearly elevated
conditions for portions of western Oklahoma and western north
Texas. Fuels are of course green but relative to what they should
be this time of year their moisture content is low. Latest ERC-G
values are around the 70th percentile. Some initial attack fire
activity will be possible both afternoons.

It`s worth noting that there is a small section of central
Oklahoma that has seen significantly below normal rainfall for the
last 30 days, and this includes the OKC metro area. Fuels may
locally be more responsive to fire in this area, although again
this must be put in context for the time of year. Fuel dryness
isn`t nearly what typically occurs during late winter and spring
when fuels are dormant.



Oklahoma City OK  73  94  75  94 /   0   0  10  40
Hobart OK         73  98  76  95 /   0   0   0  30
Wichita Falls TX  73  97  75  98 /   0   0   0  20
Gage OK           72 100  69  87 /   0  10  10  20
Ponca City OK     74  94  72  89 /   0   0  30  40
Durant OK         71  91  74  94 /   0   0   0  20




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